Iprc Saint Joseph-concrete Technology
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CONCRETE TECHNOLOGY
LABORATORY MANUAL
PLAIN CONCRETE
&
REINFORCED CONCRTE
PART-I:CEMENT CONCRETE
February, 2013
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CHAPITER-I
CEMENT
1. DEFINITION1.1. WHAT IS CEMENT?
In the most general sense of the word, cement is a binder, a substance that sets and hardens
independently, and can bind other materials (ingredients) together.
The word "cement" traces to theRomansword, who used the termopus caementicium
to describemasonryresembling modernconcretethat was made from crushed rock with burntlimeas
binder.
Thevolcanic ashand pulverizedbrickadditives that were added to the burnt limeto obtain a hydraulic
binder were later referred to as cementum, cimentum, cment, and cement.
Cement used in construction is characterized as hydraulicor non-hydraulic.
Hydraulic cements (e.g.,Portland cement)harden because ofhydration,chemical reactions that occur
independently of the mixture's water content; they can harden even underwater or when constantly
exposed to wet weather.
The chemical reaction that results when theanhydrouscement powder is mixed with water produces
hydratesthat are not water-soluble. Non-hydraulic cements(e.g.gypsumplaster)must be kept dry in
order to retain their strength.
The most important use of cement is the production ofmortarandconcretethe bonding of natural or
artificialaggregates(ingredients) to form a strong building material that is durable in the face of normal
environmental effects.
Note:Concreteshould not be confused with cement, because the term cement refers to the material used
to bind the aggregate materials of concrete. Concrete is a combination of a cement; aggregate
(ingredients) and water.
1.2. WHAT IS MORTAR?
Mortaris a workable paste used to bind construction blocks together and fill the gaps between them.
The blocks may bestone,brick,cinder blocks,etc.
Mortar becomes hard when it sets, resulting in a rigidaggregatestructure. Modern mortars are typically
made from a mixture ofsand,a binder(cementorlime), and water.
Mortar can also be used to fix, or point,masonrywhen the original mortar has washed away.
1.3. WHAT IS CONCRETE?
Concreteis acompositeconstruction material made primarily withaggregate(ingredients),cement,and
water.There are many formulations of concrete, which provide varied properties, and concrete is the
most used man-made product in the world.
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Concrete is widely used for makingarchitectural structures,foundations,brick/blockwalls,pavements,
bridges/overpasses,motorways/roads, runways,parkingstructures,dams,pools/reservoirs,pipes,
footingsfor gates,fencesandpolesand evenboats.
Note: Concrete technologywas known by theAncient Romansand was widely used within theRoman
EmpiretheColosseumis largely built of concrete. After the Empire passed, use of concrete becamescarce until the technology was re-pioneered in the mid-18 thcentury.
2. CHEMICAL REACTIONS OF CEMENT
When these ingredients are mixed, they form a plastic mass which can be poured in suitable mould calledforms; and set on standing into hard solid mass.The chemical reaction of cement and water, in the mix, is relatively slow and requires time and favorabletemperature for its completion. This time is known as Setting Timewhich may be divided into threedistinct phases:
Phase 1:
This phase is designated as time of Initial Setting Time which requires a time from 30 minutesup to 60 minutes for completion.During this phase, the mixed concrete decreases its plasticityand develops its pronouncedresistance to flow.
Phase 2:This phase is designated as the time of Final Setting Time which may vary between 5 hoursand 6 hours, after the mixing operation.During this phase, the concrete appears to be relatively soft solidwithout surface hardness
Phase 3:This phase consists of progressive hardeningand increase in strength.
The process is rapid in the initial stage, until about One month ( 28 days) after mixing, at which time theconcrete almost attains its major portion of Potential Hardness and Strength.
REMARKS:
Depending on the quality and proportions of the ingredients used in the mixing process, the propertiesof concrete vary almost as widely as different kinds of stones.
Concrete has enough strength in Compressionbut has little strength in Tension.Due to this, concrete as such is weak in Bending, Shear and Torsion.
Hence, the use of Plain Concrete, describe above, is limited to applications where great CompressiveStrength and Weight are the principal requirements and where Tensile Stresses are either totally absent orare extremely low.In order to use concrete Cement Concrete for common structures such as beams, slabs, retaining
structures ect; steel bars may be replaced at tensile zones of the structures which may then beconcreted.The steel bars known as Steel Reinforcements, embedded in the concrete, takes the tensile stresses. Theconcrete so obtained is is termed as Reinforced Cement Concrete, commonly abbreviated as RCC
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3. CLASSIFICATION AND COMPOSITIONOF CEMENT
3.1. CLASSIFICATION
Cement may be classified into five groups shown as follows:1. Portland cement2. High Alumina cement3. Super sulphated cement4. Natural cements5. Special cement
1.Portland Cements-PC:
Ordinary Portland Cement (OPC) Rapid Hardening Cement (RHC) Extra Rapid Hardening Cement (ERHC) Low Heat Portland Cement (LHPC) Portland Blast Furnace Slag Cement (PBFSC) Portland Puzzolana Cement (PPC) Sulphate Resisting Portland Cement (SPC) White Portland Cement (WPC) Coloured Portland Cement (CPC)
2. High Alumina cement
Super Sulphated Cement Natural Cements Special Cements: Masonry Cement Trief Cement Expansive Cement Oil Well Cement
3.2. COMPOSITION OF PORTLAND CEMENT
The principal raw materials used in the manufacture of cement are:
1. Argillaceous or Silicate of Aluminum -(AlO)2SiO32. Calcareous or Calcium Carbonate (CaCO3). This is found in the form of Lime stone, Chalk and Marl;which is a mixture of clay and calcium carbonate
MANUFACTURING OF CEMENT:PORTLAND CEMNT (PC)The ingredients are mixed in the proportion of about two partsof Calcareous material
to one partof Argillaceous material. Then, the dry mixture is crushed and ground in ball mills (mixed
in dry state or in wet state)The dry powder or wet slurry is then burnt in a rotary Kiln at the temperatureof between 14000C to 15000C.
The clinker obtained from the Kiln is first cooled and then passed on to ball mills where gypsum is addedand it is ground to the requisite fineness according to the class of product.
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CHIEF CHEMICALS CONSTITUENT OF PCChemical Name Formula Quantity (%)
Lime CaO3 60 - 67
Silica SiO2 17 - 25
Alumina Al2O3 3 - 8
Iron Fe2O3 0.5 - 6Magnesia MgO 0.1 - 4
Sulphur Trioxide SO3 1 - 3
Sod (Potash) Na2O + K2O 0.5 - 1.3
COMPOUND CONSITUENTS OF PCNote: When single raw materials (chemical constituents of OPC undergo chemical reactions during
burning and fusion; and combine to form the following compounds , called
Bogue compounds, in the finished products.
Compound Chemical Name Formula Abbreviated names
Tricalicium Silicate 3CaO.SiO2 C3SDicalicium Silicate 2CaOSiO2 C2S
Tricalicium Aluminate 3CaOSiO2 C3Al
Tetracalicium Alumino-ferrite 4CaO.Al2O3Fe2O3 C4AF
COMPOSITION AND COMPOUND CONTENT OF PCDescription Normal Rapid Hardening Low Heat
1. Composition (%) Xxx xxx xxx
Lime 63.1 64.5 60
Silica 20.6 20.7 22.5
Alumina 6.3 5.2 5.2
Iron Oxide 3.6 2.9 4.62. Compound (%) Xxx xxx xxx
C3S 40 50 25
C2S 30 21 45
C3Al 11 9 6
C4AF 12 9 14
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4.DESCRIPTION AND PROPERTIES OF CEMENT
4.1. ORDINARY CEMENT
ORDINARY PORTLAND EMENT (OPC)Properties of various Portland Cement (OPC) differ because of relative proportionsof the four compounds and the fineness to which the cement the cement clinkeris ground.The Ordinary Portland Cement (OPC) also called Setting cement(SC) is the basicPortland cement and is manufactured in larger quantities than all the others.
Application:
It is admirably suited for use in general concrete construction where there is no exposureto Sulphatein the soil or ground water.
RAPID HARDENING CEMENT (RHPC)This cement is also called High-Early Strength Cement. It is similar to OPC except
that it is ground finer, posses more more C3S (Tricalicium Silicate-3CaO.SiO2 ) than OPC.The strength of RHPC at the age of 3-days is the same as of the 7-days for OPC, with the same
water-cement ratio (W/C).
Advantages:
The main advantage of RHPC is that shuttering (formwork) may be removed much earlier,thus saving considerable time and expenses.
Also, in the concrete products industry (prefabrication industry), the moulds can bereleased quicker.
Application:The RHPC is used for road works, where it imperative to open the road traffic with
the minimum delay.
EXTRA RAPID HARDENING CEMENT (ERHC)The ERHC is obtained by inter-grinding Calcium Chloride (CaCl2) with RHPC.
The normal addition of CaCl2is 2% ( of the commercial 70 % CaCl2) by the weight of RHPC.The addition of CaCl2also imparts quick setting properties.
Application:
This cemnt (ERHC) should be placed and fully compacted with 30 minutes of the mixing time
LOW HEAT PORTLAND CEMENT (LHPC)When concrete is poured in any structure, an increase in temperature occurs and a certain amount
of heat is generated. This is due to the chemical reaction that takes place while the cement is settingand hardening.
Application:
The LHPC is used in massive constructions like abutments, retaining walls, dams, etcwhere the rate atwhich the heat can be lost at the top surface is lower than at which the heat is initially generated.The heat generated in OPC at the end of 3-days may be of the order of 80 calories / gram of cement; whilein LHPC it is about 50 calories/gram of cement.
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Composition:
The LHPC has the low percentage of C3A and relatively more C2A and less and less C2S than OPC.This is achieved by restricting the amount of Calciumand increasing the Silicatespresent in the rawmaterials of manufacture. Therefore, iit has low rate of gain of strength, but the ultimate strength is
practically the same.
PORTLAND BLAST FURNANCE CEMENT (PBFC)The PBFC is a special blended cement with low heat of hydration characteristics for mass concreting.Concrete produced using PBFC have chlorideand sulphateresisting properties with improved durability.
Composition:
It is made by intergrading Portland cement clinker and blast furnace slag being not lessthan 25% or more than 65 % by weight of cement.The slag should be granulated blast furnace slag of high lime content which is produced by
rapid quenching of molten slag obtained during the manufacture of pig iron in blast furnace.
Application:In general,, the PBFC will be found to gain strength more slowly than the OPC.From, the point of view of builder and the structural engineer, the PBFC may be used for all purpose for
which OPC is used .In addition, in view of its low heat evolution the PBFC can be used in massconcrete structures such as dams, retaining walls, foundations and bridge abutments.
PORTLAND POZZOLANA CEMENT (PPC)The PPC is manufactured either by intergrinding of Portland Cement clinker and pozzolanaor by intimately and uniformly blending Portland Cement and fine pozzolana.
The proportions of pozzolana may vary from 10 %-25 % by weight of cementThe pozzalana used in the manufacture of PPC is burnt clay or shale or fly ash
Application:The PPc has high resistance to chemical agencies and resists to attacks of sea water,
because of absence of free lime.The PPC also has a lower heat of evolution, It is frequentely statedto have a lower rate of development.The compressive strengths reached by PPC are comparable with those reached by the OPC.
Compression strength, N/mm2
Age, days PPC OPC
3 20-22 19-23
7 26-33 27-32
28 37-48 26-52
SULPHATE RESISTING PORTLAND CEMENT (SRPC)In the SRPC, the quantity of Tricalcium Alumina (C3A) is strictly limited.
They are normally ground finer than Portland cement.The action of Sulphates is to form sulpho-aluminates which have expansive properties andso that cause distingration of the concrete.The SRPC should be allowed to harden in the air for as long as possible to allow a resistance skinto be formed through carbonation, by the action of atmosphere carbon dioxide (CO2)
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WHITE AND COLORED PORTLAND CEMENT (WPC &CPC) WHITE PORTLAND CEMENT (WPC)
The graysh colour of Portland Cement is due to the presence of iron oxide (FeO).
White Portland Cement (WPC) is manufactured in such a way that the percentage of iron oxide
(FeO0 is limited to less 1 % .To achieve this, the raw materials, such ac chalk ( China clay)are used. Sodium Aluminium Fluoride-Cryolite (Na3AlF6) is added to act as flux in the absence
of iron oxide. Oil fuel is used in place of ulverised coal in the kilning process in order to avoidcontamination by coal ash .
COLORED PORTLAND CEMENT (CPC)The CPC are usually obtained by adding strong pigment, upto 10 % to OPC or to WPC,during grinding of clinker.
The essential requirements of a good pigment are that it should be permanent and shouldbe chemically inert when with cement.
HIGH ALUMINA CEMENT (HAC)
The HAC also called Aluminous Cement Founu-(ACF) is manufactured in entirely different way fromthat of Portland Cements.The raw materials used for its manufacture are chalk and bauxite which isspecial clay of extremely high alumina content.
Advantages
The HAC is characterized by its dark color, high early strength, high heat of hydration, and resistanceto chemicals attacks. It produces concrete of far greater strength and in considerably less time eventhan RHPC; and allowing earlier removal of the formwork.
Its rapid hardening properties arise from the presence of Calcium Aluminates chiefly monocalciumsilicates of Portland Cement (Al2O3.CaO) as predominant compound in place of Calcium Silicateof Portland Cement. After setting and hardening there is no hydrated lime as in the case Portland cement.The great care should be taken in the use of high Alumina Cement; and it must not be mixedwith any other type of cement since the heat given off on setting is greater than other cements.
SUPER SULPHATE CEMENT (SSC)The SSC is made from well granulated blast furnace slag (80 % - 85 %), Calcium Sulfate
(10 %-15 %) and Portland cement (1 %-2%); and is ground finer than the Portland cement
Advantages
One of its most important properties is its low total heat of hydration.
Application
It is very suitable for construction of dams, mass concreting works, Remark
Concrete made from SSC may expand if cured in water and may shrink if the concrete is curedin air. Another advantage is that SSC is high resisting to chemical attacks.
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5. SPECIAL CEMENTS
5.1. NATURAL CEMENT
Natural Cements are those cements which are manufactured from naturally occurring cementrocks,which have compositions similar to the artificial mix of argillaceousand calcareousmaterials from
which Portland cement is manufactured.The natural cement rocks are burned at somewhat lower temperatures than those used forthe production of Portland cement clinker.
The properties of such cement depend upon the composition of the natural cement rock.
5.2. MASONRY CEMENT
For a long time, lime gauged with sand was used for mortar used in laying bricks. However,in order to increase the strength and rapidity of gaining strength, it became common to mixPortland cement with the lime.
The usual proportions of Cement-Lime-Sand are as follows: For heavy loads = 1:1:6 For light loads = 1:3:12
Cement-Sand mortars are too harsh (rough) , while Lime makes the mortar easier to work.In order to avoid the necessity for mixing for mixing Cement and Lime, masonry cents have been
introduced.In general, most successful masonry cement are composed of Portland cement clinker,
Lime stone, Gypsum and Air-entraining agent (water soluble sulphosuccinamate, a water solublesulphosuccinate and a water soluble alkyl benzene sulphonate).The constituents are ground to an even greater fineness than that of High Early Strength Portland Cement.The plasticity and workability of masonry cements are imparted by the Lime stone and air-entrainingagents.
The easy workability of masonry cements and their water retentive properties help to increase theiradhesion to bricks or other building units and their shrinkage is fairly very low.
5.3. TRIED CEMENT
Trief cement is practically the same as Blast Furnace cement except that the blast furnace cement slag isground wet and separately from the cement.Wet grinding result in a fine product, with a specific surface af at least 3000 cm2/gram.
Due to this, the slow gain of strength normally associated with blast furnace cement is avoided andstrength from early ages equal to those of OPC are obtained.This cement has smaller heat of evolution while setting than OPC
5.4. EXPANSIVE CEMENT
Expansive cement expands while hardening. Ordinary concrete shrinks while hardening, resulting in
shrinkage cracks. This can be avoided by mixing Expansive cementwith the Normalcementsin the
concrete, which will neither shrink nor expand.Another useful application of Expansive Cement is in repair works where the opened up joints can befilled with this cement, so that after expansion a tight joint is obtained.
Expansive Cement has been used in France for underpinning and for the repair of bomb damaged archbridges.
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5.6. OIL WELL CEMENT
In the drilling of wells, cement is used to fill the space between the steel lining tubeand the wallof the well, in order to grout up porous strata and to prevent water or or gas fromgaining access to oil bearing strata.The cement used may be subjected to very high pressure, and the temperature may rise to 4000F
say 204.40C.The cement used must be capable of being pumped for up to about 3-hours.It must also harden quickly after setting.All these properties can be achieved by:
Adjusting the composition of the cement Adding retarders to OPC
The setting times of up to 4 hours at a temperature of 200 0F say 93.30C and 6-hours at a temperature of70
0F say 21.1
0C, can be obtained with a Portland Cement containing no Tricalcium Aluminates (Ca3A).
By the use of retarders, the setting times of up to 6-hours and 30 minutes at the temperatureof up to 2200F say 104.40C.
6. SPECIFICATIONS OF PORTLAND CEMENT
6.1. INTRODUCTION
For the quality control of Portland cement used for Plain concreteand Reinforced concrete,the different Standard Institutes have recommended the following specifications and tests.
The main tests are the following: Fineness tests Setting time test Heat of hydration Soundness test Compressive strength test
6.2. CHEMICAL REQUIREMENTS
When tests in accordance with the methods given IS: 4032-1968 (Methods of chemical analysis ofhydraulic cement), Ordinary Portland cement and Rapid Portland Cement shall comply withthe following chemical requirements.
Ratio % of Lime to % of Silica, alumina
and iron oxide
Not greater than 1.02
and not less than 0.66
Ratio % alumina to that of iron oxide Not less than 0.66 %
Weight of insoluble residue Not less than 2 %
Weight of magnesia Not more than 6 %
Total sulphur content calculated as sulphuric
anhydride (SO3)
Not more than 2.75
Total loss in ignition Not more than 4 %
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FINENESSWhen the cement is tested for Fineness in terms of specific surface, by Blaine Air Permeability method;the cement will comply with the following requirements.
Type of cement Specific surface (g/cm2)
Ordinary cement Not less than 2250Rapid hardening cement Not less than 2250
Low heat cement Not less than 3200
SOUNDNESSWhen tested by the Le Chateliermould method described in IS:47031-1968; unaerated ordinaryrapid hardening and low heat Portland cement shall not have an expansion of more than 10 mm
SETTING TIMEThe setting time of cements, when tested by Vicat apparatus method shall conformto the following requirements
Description Type of cement
Ordinary cement Rapid hardening Low heat cement
Initial setting in minutes Not less than 30 Not less than 30 Not less than 60
Final setting time in minutes Not more than 600 Not more than 600 Not more than 600
COMPRESSIVE STRENGTHThe average compressive strength of at least three mortar cubes; with area of 50 cm2;composed of one partcement and tree parts of standard sand- say 1:3 by weight
and ( P/4) + 3.0 percent(Combined weight of cement + sand); and the water; where P represent water required to produce a
cement mortar of standard consistency.The cubes are prepared, cured in the water and tested after 28 daysThe compression strength for different types of cements is given below:
Curing time,in days
Type of cement
Ordinary cementN/mm2 (MPa)
Rapid hardening cement;N/mm2(MPa)
Low Heat cementN/mm2 (MPa)
1-day (not cured) xxxx Not less than 11.5 xxxx
3.days Not less than 11.5 Not less than 21 Not less than 7
7-days Not less than 17.5 - Not less than 11.5
28-days xxxx xxxx Not less than 26.5
Normally the following quantities are adopted: Cement.. = 555 g Standard sand = 185 g Water .= 110 ml
Note: The above quantities are taken for 1-cube only
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HEAT OF HYDRATIONThe requirement shall apply only to Low Heat cement. When tested according to the methoddescribed in IS: 4031-1968; the Heat of hydration of Low heat Portland cement (LHPC)shall be as follows:
Type of cement Period Quantity, in calories/g
Low Heat 7-days Not more than 65 cal/g28-days Not more than 75 cal/g
7. LABORATORY TESTS ON CEMENT
The quantity of cement and that of concrete manufactured from it, is judged from the tests conducted in
the laboratories, as the work in the field progresses.There are a large number of tests for Portland cement, but we shall discuss the following important tests:
Fineness test Consistency test Soundness test Setting time test
Compressive strength test Tensile strength test
7.1. FINENESS TEST
It has been found that the rate of hydration and hydrolysis and the subsequent setting of cementDepends upon its Fineness of the particles. The rate of gain of strength is rapid for finer cementthough the final strength is not affected by Fineness. Therefore, the shrinkageand cracking
of cement is greater for fine cement.
MEASUREMENT OF FINENESSThe Fineness of Cement is measured in term of Specific surface(cm2/gram).
There are several methods of measuring specific surface of cement, such as: Particles size distribution method Blaine air-permeability method Wagner turbid meter method
BLAIN AIR-PERMEABILITY METHODThe Blaine Air-permeabilityapparatus is used for determining the Finenessof cement in termsof specific surfaceexpressed as total surface area in square centimetersper gram (cm2/g)of cement. This is a variable flow type are permeability.
The mains components are listed below: Stand of Frame U-tube monometer Manometric liquid (dibutylphatalate) Permeability Cell Cell plunger Cell perforated disc Filter papers Pumping pipe
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Blaine air Permeability apparatus
The Blain Air-permeability apparatus consists essentially of a means of drawing a definitequantity of air through a prepared bed of cement of definite porosityThe number and size of pores in a prepared bed of cement of definite porosity is a function
of the size of the particles and determines the rate of air flow through the bed.
DISPOSITION AND FUNCTION OF COMPONENTSThe Permeability cell consists of a rigid cylinder of glass or non-corrodible metal of 12.7 mm
diameter. The cell is fitted to the U-manometer tube assembly.The bottom of the of the cell forms an airtight connection with the top of manometerPerforated disc of 0.9 mm thickness; perforated with 30-40 mm holes; 1 mm dia. equally distributed
over its surface fits the inside of the cell snugly.
The Plunger is used to compact the bed of cement over the perforated disc.The height of the plunger is such that when the head of the of the plunger touches the top of the cell,
the difference between the height of the plunger bottom and perforated disc is 15 mm.The top of the one arm of the U-tube manometer forms an air tight connection with the Permeability cell.A positive airtight valve or clamp is provided on the side outlet.The U-tube manometer is filled to the midi-point with non-volatile, non-hygroscopicliquid of low viscosity and low density, such as dubitylphatalate
TEST PROCEDURESThe test is conducted into on two samples:
Test on standard sample Test on the sample of cement under investigation
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A.TEST ON STANDARD SAMPLE
The Test on Standard Sample is commonly known as the Calibration of Apparatus;and the complete test is done in the following steps or phases:
Step 1: DETERMINATION OF BULK VOLUMEOF
COMPACTED BED OF CEMENT POWDERA thin bed of dry cement, of height 15 mm is compacted in the cylinder; this bed of cement
is actually the test specimenIn order to know exactly the bulk volumeof cement compacted in the cell, the mercuryis used.The perforated metal disc is first placed in the cell and the two filter papers are placed
over it.The filter papers are pressed with the help of the rod slightly smaller than the cell diameter, until the filter
paper-discs are flat on the perforated disc.Then, mercury is filled in the cell up to its top.Use a glass plate to level the mercury with the top of the cell.
Mercury is removed (emptied) from the cell and weigh it; and record the weight Wa(g).
The one of the filter paper-discs is removed from the cell.Measure about 2.8 g of cement and fill it into the in the cell.Tapping slightly the overall side of the cell in order to level the bed of cement.
Put another filter paper-disc ob\n the top of the cement and compress it with plunger until the plunger
collar is in contact with the rim of the cell; the plunger is then removed leaving a space.Fill the mercury in the remaining space in the cell and level off the top by using a glass plate.
Remove the mercury from the cell and weigh it; record the weight Wb(g)The bulk volume occupied by the cement is calculated by the following expression:
V = (Wa - Wb) / D
Where V= Bulk Volume of compacted bed of cement powder
D= Density of mercury at temperature of test (at to = 260C, the D = 13.53)
Wa= Weight of mercury filled into the cell beforeWb= Weight of the mercury filled in the left space after compression of cement
in the cell
Step 2: TEST ON STANDARD SAMPLE
The air permeability is first conducted on the standard sample. The standard sample is generallyavailable in the vial. The contents of the vial are enclosed in a 125 g jar and shaken vigorously.
The weight W of standard sample used for the calibration test should be that required to producea bed of cement having a porosity of 0.005, and is calculated from the following expression
W =V (1-e)
Where W= Weight of Standard sample= Specific gravity of test sample (for Portland cement, a value of 3.15 is used)V= Bulk volume of bed of cement, determined from equation.e= Desired porosity of cement (0.500 +/-0.005)
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Put a filter paper disc above perforated disc and place the quantity of standard cement determinedabove (its quantity).
Place a filter paper disc over the bed and compress it with the plunger till the plunger collaris in contact with the top (rim) of cell; then, remove the plunger.Attach the cell to the manometer U-tube, making certain that an airtight connection is obtained andtaking care not to jar or disturb the prepared bed of the cement.
The air in one arm of the U-tube manometer is slowly evacuated until the liquid reaches the top mark -E;and the valve is then closed tightly.The stopwatch as started as the bottom of the meniscus of the manometer liquid reaches the second mark-F; and is stopped as the bottom of meniscus of the liquid reaches the third mark-GMeasure the Time intervalbetween Fand G ; and record the temperature of the test.
B. TEST ON TEST SAMPLE
Repeat completely step-2 on the cement to be testedThe weight of sample to be compacted is calculated from equation of the weight of Standard sample (W).It is customary to use the same porosity (0. 500 +/- 0.005).
However, while determining the Fineness of High-early- strength cements, a porosity of
0.530 +/- 0.005 should be adopted.Determine the Time taken by the liquid to drop from point-F up to point-G as describedin step-2. Measure the temperature during the test.
CALCULATIONThe Specific Surfaceof cement is calculated from the following expression:
S = Ss (T/Ts)
Where S= Specific Surface (cm2/gram) of the Test sample
Ss= Specific surface of the Standard sample
T= Time interval (in seconds) of manometer drop for the Test sample
Ts= Time interval (in seconds) of manometer drop for Standard sampleNote: The above expression is valid only if temperature (T,Ts) during both the tests is constant. If thetemperature varies, the following expression is used.
S =Ss (T/Ts).(ns/n)
Where ns= Viscosity (in poises) of the air at the temperature of test of the Test samplen= Viscosity (in poises) at the temperature of the test of the Test sample
Note: Bothe the two above equations of Specific surface (S) are valid only if the Test sampleis compacted at the same porosity as the Standard sample.
If the porosity is different, the following expression is used:
S =Ss(T/Ts).(ns/n).(e3/e).[ (1- es)/(1- e)]
Where es= Porosity of bed of Standard sand
e= Porosity of bed of Test sample
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Density of Mercury, Viscosity of Air (n) andn
RoomtemperatureT0C
Density ofMercuryg/cm3
Viscosity ofair (n), poise)
n
16 13.56 0.0001788 0.01337
18 13.55 0.0001798 0.01341
20 13.55 0.0001808 0.01344
22 13.54 0.0001818 0.01348
24 13.54 0.0001828 0.01352
26 13.53 0.0001837 0.01355
28 13.53 0.0001847 0.01359
30 13.52 0.0001847 0.01362
32 13.52 0.0001867 0.01366
34 13.51 0.0001876 0.01369
C.SIEVING METHOD
APPARATUSDrying oven, 1050C-1100C heat capacity
Laboratory balanceSieve: 90 micros
PROCEDUREDrying the cement powder in oven for 24 hours, at 1050C-1100CWeigh about 100 grams of cement powder; with standard sieve of 90 micros
Break down all air-set lumps in the sample with fingers
Continuously sieve the sample giving circular and vertical motion for a periodof 15 minutes or use mechanical sieve devices for 5 minutesWeigh the residue retained on the sieveDetermine the Percentage of the residue and the weight of initial cementNote: This weight will not exceed 10 % of initial weight of cement
7.2. STANDARD CONSISTANCY TEST
Many tests on cement , such as the determination of Setting time, Soundness,Compressive strength and Tensile strength ect; require the preliminary determination
of the amount of mixing water required in order to produce a good cement paste of
Standard Consistency.
The test for the determination of water content to form the cement paste of Standard Consistencyis conducted with the help of Vicat apparatus.
DEFINITIONThe Standard consistency of the cement paste is defined as that consistency which will permit the Vicatplungerto penetrate to a point 5 mm-7 mm depth.The two cases may happen due to the scale graduation:
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If the scale is graduated from the 40 mmup to 0 mmdownward; then, the plunger muststop at the depth of 35 mm up to 33 mm from the to
If the scale is graduated from the 0 mm up to 40 mm upward; then, the plunger must stopat the depth of 5 mm up to 7 mm from the top
VICAT APPARATUS
Vicat apparatus with mould
The Vicat apparatus consists principally to the following components: Stand or Frame Plunger (300 g) Needles (for initial & final setting time) Release pin Clamping pin Scale ( 0 mm-40 mm) Piston or movable rod Vicat mould Glass base plate( non-porous plate)
Other apparatus or equipments needed are: Weighing balance Crucible or tray Graduated measuring cylinder Trowel or Spatula Stopwatch or Timer
TEST PROCEDURE Weigh about 500 g of cement powder Measure the quantity of pure water of 24 % ( water /cement ratio) of the weight of the
cement Prepare the cement paste; the mixing time must be not more than 5 minutes
Adjust and fix the Vicat plunger in the Vicat Apparatus Place very well the non-porous base plate and the mold on the Vicat stand Fill the cement paste in the mould and shake the mould to expel the air Smooth the top surface of the cement paste ( block test) Release the plunger and let it to penetrate in the cement paste freely After about 40-60 seconds, when the plunger seems to stop, read on the scale the depth
(penetration)
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Note: Repeat the procedure by varying the Water / Cement ratio(with 25 %; 26 %; 27 %) until you found out the required depth (5 mm-7 mm)
The plunger could penetrate the depth of 35-33 mm from the bottom of the mould or 5mm-7 mmfrom top surface of the cement paste (block test).The Standard Consistency helps to determine the required water to produce a good cement paste.
RESULTATThe Standard Consistency is expressed in percentage, as follows:
SC = (W/C) x 100expressed in percentage
Where: W= Mixing water (ml)C= Cement powder (g)
7.3. SETTING TIMES
The Setting time of the cement may be divided into two phases:
Initial setting time Final setting time
It is difficulty to say what exactly each time means as they are arbitrary points in relationship connectingthe strength of cement with the time from adding water.
DEFINITIONThe Initial setting timeis a phase in the process of hardening of cement after which any cracks that mayoccur or appear will no re-unit (it is dangerous phase).
The Final setting timeis a phase in the process of maximum hardening of cement is reached.The two setting times are defined arbitraryin the Vicat testby using appropriate needles.
In actual construction dealing with cement paste, mortaror concrete; a certain time is required formixing, transporting, compacting and finishingDuring this time, the cement paste, mortar and concrete should be in plastic condition.
RESULTATThe time intervals from which the cement products remain in plastic conditionis known asInitial Setting Time. Normally a minimum of 45 minutes aboveis given for mixing andhandling operations.
Note: The constituents and fineness is maintained in such way that the concrete remains in plasticcondition for certain minimum time
Once the concrete is placed in final position, compacted (vibrated) and finished; it should
loose its plasticity in earliest possible time; so that it is least vulnerable to damages from externaldestructive agencies.
This time should not be more than 4 hrs to 10 hrs; which is referred to as Final Setting Time (maximumhardening of cement)
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A. INITIAL SETTING TIME TEST
Initial Setting Time is defined as the elapsing time from which when water is added to thecement and the time at which the cement paste starts loosing its plasticity (reduction in water content)Note: The apparatus used is known as Vicat ApparatusIn this case, the sliding plunger and Initial setting time needle are the ones considered
APPARATUSThe apparatus are the same as those used for Standard consistency; except the plunger whichis replaced by Initial setting time needle (the pointed needle).
PROCEDURE Prepare the cement paste of standard consistency Check if the penetration depth of the plunger is 35-33 mm from the bottom
of the mould or 5-7 mm from the top surface of block test
If the penetration required attained the depth, then replace the plunger by theInitial Setting Time Needle ( the pointed needle) and adjust it
Release the Needle and let it penetrate in the test block; the needle absolutelypenetrates until a certain depth into the test block
After a given time, check again the penetration over the whole surface of the block test Repeat the procedure until the penetration is 35-33 mm from the bottom of mold
or 5-7 mm from the top surface of the cement paste.
RESULTCheck the time elapsing between the time at which water is added to the cementand the time atwhich the Initial Needle penetrates 35-33 mm of depth from bottom or 5-7 mmfrom topThe time computed is known as Initial Setting Time; expressed in minutes.
Note: In general, Initial Setting Time of cement is more or equal to 30 minutes
B. FINAL SETTING TIME
Final Setting Time is the time elapsing from at which water is added to the cement and the
time at which the Final Setting Time Needle failure to make a circular impression on the block test;or when the Final Needle and its centre does not pierce through the paste more than 0.5 mm
Note: The apparatus used is known as Vicat Apparatus
In this case, the sliding plunger and Final setting time needle are the ones considered during experiment
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APPARATUSThe apparatus are the same as those used for Initial setting time; except the Initial setting timeneedle replaced by Final setting time needle (the annular needle).
PROCEDURE After checking the Initial Setting Time; then replace the Initial setting time Needle by the
Final setting time Needle. The Final setting time Needle has got a circular cutting edge attachment at
its end rim. Release the setting time Final Needle and check if it makes a circular impression on the
block test.
If it gives a circular impression on the test block, then repeat the procedure until the Finalsetting time Needle fails to do so; it marks only a point.
RESULTIf it makes about 0.5 mmor makes an impression of only a pointon the test block; then compute
the time elapsing from the time at which the water is added to the cement until the time at whichthe Final Needle fails to make an impression on the block test.
This time is known as Final setting Time; expressed in minutes and hours
At this time, the cement paste (block test) is completely hardenedIn general, the Final Setting Time for the cement is more or equal to 600 minutes (or 10 hours)
7.4. SOUNDNESS TEST
DEFINITIONThe Soundnessis meant the ability or otherwise ability of cement to maintain a constant volume.The cement having some quantity of free lime (CaO) and magnesia (MgO) undergoes large change
of volume as the time elapses, tending to cause cracks; such cement is calledunsound cement.The Soundness of cement is determined either by LeChatelier mould or by means of
Autoclave Test
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LE CHATELIER METHODThe test is carried by the means of Le Chateliermould apparatus which consists of small split cylinderof spring brass, or other suitable metal of 0.5 mm thickness, forming a mould of 30 mm internal diameterand 30 mm high.
On either side of the split are attached two indicators with pointed ends; the distance from these ends and
the centre of the cylinder being 165 mm
APPARATUS Le Chatelier mould Water bath ( for curing) Le Chatelier water bath ( for heating) Weight (10 g) Square glasses Steel rule
Le Chatelier mould and accessories Le chatelier water bath
PROCEDURE Weigh about 400 g of cement Measure water quantity of 0.78 times the weight of cement (0.78 x P) Check the standard consistency of the cement paste Fill the cement paste into Le Chateliermould kept on the glass plate Smooth the top surface of the cement and cover the mould with another glass
plate and weight (10 g)
Immerse the whole assembly in the water, at the temperature of 270C-320C; for 24 hours Measure the distance separating the indicator-end points Submerge again the mould in water and heat and bring to boiling point;
for about 25-30 minutes; keep it boiling for 3 hours Remove the assembly from water and; allow it to cool Measure again the distance between two end pointers
RESULTCompute the differencebetween the first measurementand the last measurement.
This differencerepresents the expansion(volume change) of cementUnaerated ordinary rapid hardening and Low Heat Portland cement should not have an expansionof more than 10 mmNote: This distance should be less than 10 mm.If it is more than 10 mm, then the cement is said unsound
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7.5. COMPRESSIVE STRENGTH OF CEMENT
The composition strength of the concrete depends upon the strength of the cement used formanufacture concrete. Any test for the strength of cement should reflect the ability of the cementto make concrete of the a given strength.The compressive strength test of cement is conducted on mortar cubes, formed by mixing one part
of cementwith three parts of standard sand, compacted by means of a vibration machine.
MIX PROPORTION AND MIXStandard re-graded Ennore sandconforming to IS: 650-1966 is used for preparing the cementmortar. The following proportions are used.
Materials Quantity
Cement 200 (g)
Standard sand 600 (g)
Water (P/4) + 3.0 (ml)
Note: The quantity (P/4) + 3.0;percent (%) of combined weight of cement and sand, where P
is the percentage of water required to produce a paste of standard consistency.
REMARKHowever, if re-graded Ennore sandis not available, single graded Ennore sand may be used.
Such sand should pass through 850 micro (0.850) IS sieve and not more than 10 % by weightshould pass through 600 (0.600) micro IS sieve.In that case, the mix proportions may be taken as under.
Materials Quantity
Cement 185 (g)
Standard sand 555 (g)
Water (P/4) + 3.5 (ml)
Mixing ratio 1:3
Note: The quantity (P/4) + 3.5;percent of combined weight of cement and sand, where P
is the percentage of water required to produce a paste of standard consistency.
Cement and sand are first mixed dry on a non-porous plate (tray) with a trowel for one minute
and then with water until the mixed is of uniform color.The time of mixing should in any event not be less than 3-minutes and should the time taken to
obtain a uniform color exceed 4-minutes; the mixture should be rejected and the operation repeatedwith a fresh quantity of cement, sand and water
MOULDING SPECIMENSThe Compressive strength test is done on mortar cubes having area of face of 50 cm2.The moulds for the cube specimens of 50 cm2 face area should be of metal which is not attacked
by cement mortar.Normally, split moulds are used so that the molded specimens could be removed easily.The parts of the mould when assembled together should be positively held rigidly together.
In assembling the mould ready for use, the points between the two halves of the mould are coveredwith a fin film of petroleum jelly.
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A similar coating of petroleum jelly between the contacts surfaces of the bottom of the mouldand its base plate is applied.
The interior faces of the mould are treated with a thin coating of the oil.The assembled mould is mounted on the table of the vibrating machineand a hopper is attachedto the top of it. Immediately, after mixing the mortar, place the mortar in the mould and prod it withthe standard packing rod made of non-absorptive , non-abrasive and non- brittle material; such as a rubber
compound.The mortar should be prodded 20 timesin about 8 seconds, to ensure that the elimination of entrained airand honey combining.The remaining quantity of mortar is placed in the hopper of the cube and it is prodded again.The vibrating machine is then started and the mould is vibrated for 2-minutes.The vibrating machine should have a speed of 12000 RPM/ minute.
At the end of vibration, the mould assembly is removed from the machine, and its top is is levelledwith the blade of the trowel.
Vibrating machine Mortar cube for cement strength
CURING SPECIMENSSeveral such cubes are compacted in separate moulds.The mixture is made separately for each mould. The mould are kept at the temperatureof 270C-290C and in an atmosphere of at least 90 % relative humidity for 24 hours after
the completion of the vibration.After that, the cube specimens are removed from the mould and immediately submerged in clean freshwater and kept there until taken out just prior to breaking.
COMPRESSION TESTINGThe three such cubes are tested at the end of specified period; the period could be 3-days,7-days or 28days. Normally, 28-days are the days required for Maximum Strength.
The Compressive strength should be the average of the strength of the 3-cubes of each period of curing.The testing can be done on any standard compression testing machine.
The cubes should be tested on their sides without any packing between the cube and the steel platens ofthe testing machine. One of the platens should carried on on a base and should be self adjusting ; and theload should be steadily and uniformly adjusted; starting from zero (0) up to a rate of 350 kg/cm2
minimum.
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CALCULATION OF COMPRESSIVE STRENGTHThe compressive strength is calculated from the Crushing Load(P) and the Area (A)
over which the load is applied.If P = Applied load, Newton (N)
A= Surface over which the load is applied, mm2
The Compression Strengthis given by the following expression:
fcompr.= P/A , N/mm2
Note: The minimum desirable value of compression strengths at various curing periods,
for different cements are as follows:
Curing time
(days)
Type of cement
Ordinary cement
N/mm2 (MPa)
Rapid hardening cement;
N/mm2(MPa)
Low Heat cement
N/mm2 (MPa)
1-day (not cured) xxx Not less than 11.5 xxx
3-days Not less than 11.5 Not less than 21 Not less than 7
7-days Not less than 17.5 xxx Not less than 11.528-days xxx xxx Not less than 26.5
Compression testing machine.
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7.6. TENSILE STRENGTH OF CEMENT
Just like Compressive strength, the Tensile strength of cement is determined by testing specimensof cement-sand mortar in direct tension.
MIXING PROPORTIONStandard sand or Ennore sandis used for preparing the cement mortar.
The following proportions used:
Materials Quantity
Cement 250 (g)
Standard sand 750 (g)
Water (P/5) +2.5 (ml)
Mixing ratio 1:3
Percent of total weight of cement and sand; where P is the percent of water required for StandardConsistency. The mortar is prepared exactly in the same as for the Compression test.
MOULDING SPECIMEN AND CURINGSpecimens are prepared in Standard briquette moulds, placed on no-porous plate. The moulds are of splittype so that specimens could be easily taken (removed) out later.
These moulds are open on both ends of the faces.
Tensile strength machine (a) and Standard briquette mould(b)
MAIN COMPONENTS OF TENSILE STRENGTH MACHINE Frame Yard
Pan Upper and Lower jaw: holding specimen Counterpoise
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APPARATUS AND EQUIPMENTS Tensile testing machine Hopper: containing lead shots Standard briquette mould Non-porous plate Standard spatula
Note: This Cement tensile testing machineis primarily used to determine the Tensile strength of
briquette specimens of cement. It can also be used to test the Flexure strength of the sample. This test
is commonly used by Cement Manufacturers in order to determine the quality of cement.
DIMENSIONS OF STANDARD BRIQUETTEThe thickness of briquette is :
Length: -Minimum .= 50.8 mm ( inner)
-Maximum .= 76.2 mm (outer)
Bridth: - Minimum= 25.4 mm ( at the neck)
-Maximum.= 44.5 mm (outer)
The cross-sectional area (at the neck) = 654mm2
Before filling the mould, the two halves of the mould are lightly greased and the inner surface
of the mould is coated with oil; then the mortar is then filled in the mould.
To ensure the complete filling of the mortar in the mould, the mortar should be heaped on the mould and
the excess mortar is beaten down by means of standard spatula until the mortar is on the same level with
the top rim of the mould, then water appears on the top surface of the mortar
Note: This process of heaping and beating down the mortar on the other open face of the mould is
repeated. Finally, the two faces are smoothened by the help of trowel.
After 24 hours, the briquettes-specimens are removed from the moulds, immediately they are immersed
into the water; at 270C temperature and humidity of 90 % and leave them in until the day of test. Twelvespecimens are prepared; sixof which are tested after 3-days and the other six are tested after 7-days.
TEST FOR TENSILE STRENGTHThe briquettes specimens so prepared are tested on a Special Tensile testing machine.
The machine utilizes the principle of compound lever for applying tensileforce.
The briquette-specimen is held in position in specially shapedjaws.
A pan is attached to the free end of the lever. The loading is done by allowing lead shots to fall from a
hopper to the pan. This causes the tensileforcein the briquette-specimen which ultimately breaks.When fracture occurs, the supply of lead shots is automatically cut-off. The lead shots collected in the panare weighted by moving the counterpoise until balance is obtained
The reading pan the yard gives the tensile load during fracture process.The Load divided by the Area of neck gives the Tensile strength of the briquette-specimen
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CALCULATIONIf WLs= Read value on counterpoise, Newton (N)
As= Cross-sectional area at the neck of briquette, mm2
The Tensile Strengthis given by the following expression:
ftensile= WLs/ As ,N/mm2
7.8. FLEXURAL TEST STRENGTH
Flexure testingis often done on relatively flexible materials such as polymers, wood and composites.There are two test types; 3-point flexural test and 4-point flex.In a 3-point testthe area of uniform stress is quite small and concentrated under the center loading point.
In a 4-point test, the area of uniform stress exists between the inner span loading points (typically half theouter span length).
CALCULATIONS OF FLEXURAL STRESS fRECTANGULAR CROSS-SECTION AREA
If the cross-section area is a rectangular; the Flexural Stressis calculatedas follows:
Flexural strength for rectangular area
Where f = Flexural stress, MPaP= Load at a given on the load deflection curve, NewtonL = Support span , mm
b= Width of test bean specimen, mmd= Depth of test beam specimen, mm
CIRCULAR CROSS-SECTION AREAIf the cross-section area is a circular; the Flexural Stressis calculated as follows:
Flexural strength for circular area
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Where f = Flexural stress, MPa
P= Load at a given on the load deflection curve, N
L = Support span, mm
R= Radius of the test beam test, mm= 3.14
CALCULATIONS OF FLEXURAL STRAIN fTheFlexural Stressis calculated as follows:
Flexural stress
Where f = Flexural strain, mm/mm
D= Maximum deflection of the center of the beam (mm)
d= Width of the test beam (mm)L= Support span of the beam (mm)
CALCULATIONS OF FLEXURAL MODULUS EfTheFlexural Modulusis calculated as follows:
Flexural Modulus
Where Ef= Flexural Modulus (no units)
L = Support span, mmm= Gradient (slope) of the initial straight-line portion of the load deflection
curve, (P/D), N/mmb= Width the test beam
d= Depth of the test beam
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CHAPITER-II
AGGREGATE
1. DEFINITION
WHAT IS AGGREGATE?Construction aggregate, or simply "aggregate", is a broad category of coarse particulatematerial
used inconstruction,includingsand,gravel,crushed stone,slag,recycled concrete and geosynthetic
aggregates. Aggregates are the most mined material in the world.
Aggregates are a component ofcomposite materialssuch asconcreteandasphalt concrete;the
aggregate serves as reinforcement to add strength to the overall composite material.
Due to the relatively high hydraulic conductivity value as compared to most soils, aggregates are widely
used in drainage applications such as foundation and French drains, septic drain fields, retaining walldrains, and road side edge drains.
Aggregates are also used as base materialunder foundations, roads, andrailroads.
In other words, aggregates are used as a stable foundation or road/rail base with predictable, uniformproperties (e.g. to help prevent differential settling under the road or building),or as a low-cost extender that binds with more expensive cement or asphalt to form concrete.
Aggregate is a general to those inert materials or chemically inactive materials, which when bondedtogether with cement form concrete. Most of aggregate used are naturally occurring aggregates such ascrushed rock, gravel and sand. Artificially and processed aggregate may be broken bricks, of crushed air-cooled blast-furnace slag.
Light weight aggregatessuch as pumice, furnace clinker, coke , breeze, sawdust, foamed slag, expandedslates, etc; are used in production of concrete of low density , known as
Light weight concrete
Lightweight concrete, similar to Normal weight concrete, is a mixture of water, Portland cement orOrdinary Portland Cement (OPC), and aggregate.It is classified as structural or nonstructural concrete depending on strength and compression rating,
generally determined by the type of aggregate material usedin the concrete mix.
Heavy weight aggregateis most commonly used for radiation shielding, counterweights and otherapplications where a high mass-to-volume ratio is desired. ASTM C637 covers aggregates used for
radiation shielding .Heavyweight concretecontains aggregates that are natural or synthetic whichtypically weigh more than 2,080 kg/m3 and can range up to 4,485 kg/m3.
http://en.wikipedia.org/wiki/Aggregate_%28composite%29http://en.wikipedia.org/wiki/Aggregate_%28composite%29http://en.wikipedia.org/wiki/Aggregate_%28composite%29http://en.wikipedia.org/wiki/Materialhttp://en.wikipedia.org/wiki/Materialhttp://en.wikipedia.org/wiki/Materialhttp://en.wikipedia.org/wiki/Constructionhttp://en.wikipedia.org/wiki/Constructionhttp://en.wikipedia.org/wiki/Constructionhttp://en.wikipedia.org/wiki/Sandhttp://en.wikipedia.org/wiki/Sandhttp://en.wikipedia.org/wiki/Sandhttp://en.wikipedia.org/wiki/Gravelhttp://en.wikipedia.org/wiki/Gravelhttp://en.wikipedia.org/wiki/Gravelhttp://en.wikipedia.org/wiki/Crushed_stonehttp://en.wikipedia.org/wiki/Crushed_stonehttp://en.wikipedia.org/wiki/Crushed_stonehttp://en.wikipedia.org/wiki/Slaghttp://en.wikipedia.org/wiki/Slaghttp://en.wikipedia.org/wiki/Slaghttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Asphalt_concretehttp://en.wikipedia.org/wiki/Asphalt_concretehttp://en.wikipedia.org/wiki/Asphalt_concretehttp://en.wikipedia.org/wiki/Railroadhttp://en.wikipedia.org/wiki/Railroadhttp://en.wikipedia.org/wiki/Railroadhttp://en.wikipedia.org/wiki/Railroadhttp://en.wikipedia.org/wiki/Asphalt_concretehttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Slaghttp://en.wikipedia.org/wiki/Crushed_stonehttp://en.wikipedia.org/wiki/Gravelhttp://en.wikipedia.org/wiki/Sandhttp://en.wikipedia.org/wiki/Constructionhttp://en.wikipedia.org/wiki/Materialhttp://en.wikipedia.org/wiki/Aggregate_%28composite%29 -
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CLASSIFICATION OF AGGREGATESAggregates may be divided into two groups:
Coarse aggregates: which are more than 4.75 mm IS sieve Fine aggregate: which are less than 4.75 mm IS sieve
Note: For large and important works, it has become usual to separate the coarse aggregate also
into two or more sizes; and these fractions kept separate until the proper quantity to be used is
obtained.
In all aggregate (natural mixture of coarse and fine aggregate-sand) is said aggregates comes from pit orriver bed, and is sometimes used for unimportant works.
QUALITY OF AGGREGATENatural aggregate used for concrete construction is required to comply with the following norms:
Strength Particle sizes Particle shapes Surface texture Grading Impermeability Cleanliness Chemical inertness Physico-chemical stability at high temperature Coefficient of thermal expansion
Note: Aggregate should be chemically inert, strong hard, durable, of limited porosity, free from adherentand coating matters (clay lumps, coal residues); and free from organic matters or other admixture thatmay cause corrosion of the reinforcement (in RCC), or impair the strength or the durability of concrete.
DELETERIOUS MATERIALS IN AGGREGATESThe mains deleterious in aggregate are the following:
Coal Lignite Clay lumps Soft fragments Material finer than 75 micros (silt, filler, dust..) Shale
Note:The limits of content of deleterious materials are given in the table below:
Deleterious substance Fine aggregate Coarse aggregate
Uncrushed Crushed Uncrushed CrushedCoal and lignite 1 % 2.9 % 1% 1%
Clay lumps 1% 1% 1% 1%
Soft fragments - - 3% -
Fine materials less than75 micros ( silt andfiller)
3% 15% 3% 3%
Shale 1% 2% 5% 5%
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STRENGTH OF CONCRETEThe strength of concrete depends upon the strength of aggregate. The strength of aggregate depends upon
the nature of base rock (mother-rock).Granite aggregate provides greater strength than pumiceor burnt clayaggregate.Strength quality of an aggregate is usually specified in the following form:
Crushing strength Crushing Impact Value (ACV) Aggregate Impact Value (AIV)
CRUSHING STENGTHThe crushing strength of aggregate is checked under the test known as Point Load Test.It is determined on a rock sample of specific size. A minimum value of 80 N/mm2as Crushing strength
is normally accepted
AGGREGATE CRUSHING VALUE (ACV)Aggregate Crushing Value(ACV) test is the one among mechanical properties of aggregate.
It gives a relative measure of the resistance of aggregate to crushing under a gradually applied
Compressive Load. The aggregate sample is being packed in the steel cylinder known as
Crushing Impact value mould.
The test is applicable for sample consisting of aggregates passing through 12.5 mmand retainedon 10 mmdiameter sieve (the same as for ACV)
The ACV is given by the following expression:
ACV = (W2/W1).100(expressed in %)
Where W2= Weight of surface dry aggregate sample, passing 12.5 mm and retained on 10 mm
(Initial weight in calculation)
W1= Weight of fraction passing 2.36 mm after application of specified load, by using
Compressive machine
Note: The value of ACV should be:
Not exceed 45 %- for plain concrete Not exceed 40 % for RCC buildings Not exceed 30 % for prestressed concrete
Note: High value of ACV indicates a weakaggregate; and lower valueof ACV indicates strong
aggregate.
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AGGREGATE IMPACT VALUE (AIV)The Aggregate Impact Value (AIV) gives relative measure of the resistance of aggregate
to a sudden shock or sudden impact.
Which in some aggregates differs from its resistance to a slow compressive load?The test is applicable for sample consisting of aggregates passing through 12.5 mmand retained
on 10 mmdiameter sieve (the same as for ACV)
The sample shall be dried in ovenfor 24 hours; at the temperature of 1050C to 110
0C
and freely cooled in the room temperature.The AIV is given by the following expression:
AI V = (W2/W1).100(expressed in %)
Where W2= Weight of oven dry aggregate sample, passing 12.5 mm and retained on 10 mm
(Initial weight in calculation)
W1= Weight of fraction passing 2.36 mm, formed after hammering, by usinga special hammer falling from 30 mm (30 cm).
A value of AIV of 30 % indicates good quality aggregate; where the value of 45 % sometimes may be
accepted.
Note: High valueof AIV indicates a weakaggregate, therefore a weak concrete; and lower valueof AIV
indicates strongaggregate, therefore strong concrete.
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3. THE USE OF AND IMPACT OF AGGREGATE IN CONCRETE
The size of coarse aggregate used depends upon the nature of the work. The coarse aggregate must be
small enough to enable it to be worked between and around all reinforcements; and into all corners
of the work.
For RCC works, the maximum size of aggregate is limited to 20 mm-25 mm.The shape of aggregate may have free types:
Rounded shape Irregular shape Angular shape
A-Rounded shape B-C-D-Angular shape E-Irregular shape
For a concrete of a given workability, the water-cement ratio depends upon the shape of
aggregate particles: Rounded shape requires leastwater-cement ratio Angular and irregular shapes require highestwater-cement ratio
The particle shape is thus very important, since the water- cement ratio governs greatly the workabilityand the strength of concrete. Similarly, the concrete made with the aggregate of rough surface is stronger
than that made with smooth surface.Grading of aggregate greatly affects the strength and imperviousness of concrete.
Thus, if the coarse and fine aggregate are well graded; therefore, the percentage of voids is extremelyreduced. The voids of fine aggregates are then occupied by the cement paste(Cement + water) while the voids of coarse aggregate are occupied by mortar
(cement + sand + water); which result to Imperviousness.
The Imperviousness of concrete is very essential requirement, especially when the concrete is used forwater retaining structures or water canals.Imperviousness is also essential in RCC works of permanence ; otherwise air and moisture would
penetrate with the result that outer concrete would spall out (to split).
Aggregate must be cleanand free from clay, silt, filler, fine dust etc; so that proper mixing is possible.Dirt or other adherent coating matters would weaken the adhesion between the individual particles inhardened concrete.Impurities like traces of sulphuror unburntcoal etcmay cause the swellingdue to chemical action ,or may attack the reinforcements. Aggregate should resist to thermal expansion similar to cement
matrix.
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In summary, the aggregate should: Be composed of inert mineral matter; Have high resistance to attrition; Be clean, free from any adhering coating materials; Be dense, durable and strong enough; Enable to full strength of the cement matrix.
4. CATEGORY OF AGGREGATE
There are two categories of aggregate:
Coarse aggregate Fine aggregate or Sand
4.1. COURSE AGGREGATE
The material retained on 4.75 mm diameter sieve is termed as Coarse Aggregate.
Crushed stone and natural gravel are the common materials used as coarse aggregate for concrete.Natural gravel can be obtained from pits where they have been deposited by alluvial or glacial action.Natural gravel are normally composed of flint, quartz, schist, igneous rocks etcCoarse aggregate are obtained also by crushing various types of granites (like dolerites, diorites, quartzite,schist,ect,..); gneiss, crystal lime stone and sand stones.
REMARKS:
When very high strength concrete is required, a very fine grained-graniteis perhaps the best aggregate.
Coarse-grained rocks make harsh concrete, and need high proportion of sand and high water-cement ratioin order to get a reasonable degree of workability.
Harder types of sand-stones, having fine grained texture, are suitable as coarse aggregate,but softer varieties should be used with caution.
Concrete made of with sand stone aggregate give trouble due to cracking, because of high degree ofshrinkage.Similarly, hard and close- grained crystalline lime-stoneare very suitable for aggregate; it ischeap, but should be used only in plainconcrete.
The bricksshould be used clean, hard, well burnt and free from mortar, and should not contain more that
50 % of soluble sulphates. Bricks should not used for RCC works since it is porous and may corrode thereinforcement.
Blast-furnace slag, coal ashes, coke breeze act; may also used as aggregate to obtainLight-weight concrete and Insulating concrete of low strength.
4.2. FINE AGGREGATE-SAND
The materials smaller than 4.75 mm diameter sieve is called Fine Aggregate or Sand.Naturally are generally used as fine aggregate .Sand may be obtained from pits, rivers,
Sea-shore, ect When the sand is obtained from pits (pit-sand), it should be washed in order to removeclayand siltand coating matters.Sea shore sandmay contain chlorideswhich may cause efflorescence (occurrence of powder); and may
cause corrosion of reinforcement; hence, it should be washed before use.
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If river-sandcontains impurities such as mud, organic matters, ect, it should also be washed beforeuse. Angular grained sand produces good and strong concrete, because it has interlocking property; while
round grained particles of sand do not afford that interlocking property.
5. GRADING OF AGGREGATE
Grading of aggregates is almost as important as its quality is.The grading of aggregates has marked effect on the workability, uniformity and finishing qualities ofconcrete.
The grading of coarse aggregate may be varied through wide limits than that of Fine aggregate (sand)without appreciably affecting the workability of concrete.
The following sieve sizes are used for grading aggregate:10 mm
4.75 mm 300 micros2.36 mm 150 micros
1.18 mm 75 micros600 micros
Grading limits for Fine aggregates
Sieve sizes(mm)
Percentage (%) Passing
Grading
Zone-I
Grading
Zone-II
Grading
Zone-III
Grading
Zone-IV
10 mm 100 100 100 100
4.75 mm 90-100 90-100 90-100 95-100
2.36 mm 60-95 75-100 85-100 95-100
1.18 mm 30-70 55-90 75-100 90-100
0.600 mm 15-34 35-39 30-79 80-100
0.300 mm 5-20 8-30 12-40 15-50
0.150 mm 0-10 0-10 0-10 0-15
Note: The Fine aggregate (sand) of Zones I-II-III may be used for concrete works.
While, the Fine aggregate (sand) of Zone-IV should not be used except for special mixes.
6. FINENESS MODULUS OF AGGREGATE
Fineness Modulus(E) of aggregate is an index number which is roughly proportional to the Averagesizeof the particles in a given aggregate sample.The coarser aggregatehas the Higher Fineness Modulus-E.
The Fineness Modulus-E is obtained by summation of all percentages of the weight of material retained
on the following sieves sizes dividingit by 100The sieve sizes are: 80 mm;40 mm;20 mm;10 mm;4.75 mm;2.36 mm;1.18 mm;600 micros; 300 microsand 150 micro ( 10-in total)
Determination of Fineness Modulus-E of both Coarse aggregate and Fine aggregate
1. Coarse aggregate-Illustration example:
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Sieve sizes
(mm)
Retained
weight, (kg)
Retained
weight,(%)
Cumulative
(%)
80 mm 0.0 0.0 0.0
40 mm 0.0 0.0 0.0
20 mm 3.5 35.0 35.0
10 mm 6.5 65.0 100.0
4.75 mm 9.3 93.0 193.0
2.36 mm 10.0 100.0 293.0
1.18 mm 10.0 100.0 393.0
0.600 mm 10.0 100.0 493.0
0.300 mm 10.0 100.0 593.0
0.150 mm 10.0 100.0 693.0
SUM xxx xxx 693.0
Fineness Modulus-E = 693.0/100 = 6.93 (no unit)
2. Fine aggregate-Illustration example
Sieve sizes(mm)
Retainedweight, (kg)
Retainedweight,(%)
Cumulative(%)
80 mm 0.0 0.0 0.0
40 mm 0.0 0.0 0.0
20 mm 0.0 0.0 0.0
10 mm 0.0 0.0 0.0
4.75 mm 0.0 0.0 0.0
2.36 mm 0.1 10.0 10.0
1.18 mm 0.35 35.0 45.0
0.600 mm 0.70 70.0 125.0
0.300 mm 0.90 90.0 215.00.150 mm 1.00 100.0 305.0
SUM xxx xxx 305.0
Fineness Modulus-E = 305.0/100 = 3.05 (no unit)
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3. Limits of Fineness Moduli-E
Aggregatedesignation
Maximumsizes (mm)
Fineness Modulus-E
Maximum Minimum
Fine aggregate -------- 2.0 3.5
Coarse aggregate 20 mm 6.0 6.9
40 mm 6.9 7.5
75 mm 7.5 8.0
150 mm 8.0 8.5
Mixed aggregate 20 mm 4.7 5.1
25 mm 5.0 5.5
32 mm 55.2 5.7
40 mm 5.4 5.9
75 mm 5.8 6.3
150 mm 6.5 7.0
Note: In general, the Fineness Modulus-E of sand is limited as follows:
Class of sand Fineness Modulus-E
Minimum Maximum
Coarse sand 2.2 2.6
Medium sand 2.6 2.9
Fine sand 2.9 3.2
7. STRENGTH TEST OF COURSE AGGREGATE
The Strength Tests of Coarse aggregate are the following:
Crushing test-Point load Test Aggregate Crushing Value (AIV) Aggregate Impact Value (AIV) Los Angeles Test (Abrasion Test)
7.1. POINT LOAD TEST
APPLICATION
Point Load Tester (PLT) permits to determine the point load strength Index (Is).This index provides a method to establish rock strength classification
The Index can also be used to determine the rock anisotropy as well as to predict other rock strengthproperties like the unaxial tensileand compressive strengths
1. DESCRIPTIONThe PLT components consist of:
Loading framemounted on hydraulic ram and pressure gaugefor maximum load indication
Upper conical platen: which is fixed on the frame Lower conical platen: one on the jack piston Graduated scale:is fixed on the frame which indicates the specimen diameter
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2. TEST PROCEDURES
The PLT configurations are used depending one on available rock specimens
Diametric Test Axial Test Irregular Lump Test
Diametric and Axial tests use core specimenwith Length-Diameter ratio (L/D) is greater than 1(unit)in the first case; and L/Dwhich is between 0.3and 1in the second case.Note: Rock pieces of suitable irregular shapes are used when core specimens are not available.
3. TESTING PROCEDURES
Note: Testing steps are the same for all configurations The specimen is positioned between the conical platens (upper and lower platens) The platens are then closed to make contact with the specimen The distance (De) between two points of contact is measured and read on the
scale (steel rule). The load is increased gradually such that failure occurs with 10 seconds
to 60seconds .
The failure load (P) is read on the scale and recorded
Point Load testing machine
4. INTERPRETATION
Point Load Tester (PLT) allows the user to determine Unconfined Point Load Strength
Index(UPLSI) denoted IsThis Index must be corrected to a standard equivalent diameter De of 50 mm(5 cm)It then becomes unique property of the rock tested, denoted Is(50)which is most useful in rock strengthclassification
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ROCK ANISOTROPYRock anisotropy is quantified by Strength Anisotropy Index, denoted Ia(50)This Index is the ratio of the greatest to the least Ia(50) index, measured respectively perpendicularand parallel to existing planes of weakness
Anisotropy= is the property of being directionally dependent, as opposed toisotropy,which implies identical properties in all directionsThe uniaxial Tensile Strenth (UTS) and Uniaxial Compressive strength (UCS) can be approximatedfrom Ia(50) Index. Ia(50)Then, UTS is about 1.25 times Ia(50)
UTS = 1.25 x I a (50)
Note: UCSis normally ranging between 20to 25times Ia(50) indexTherefore UCSlow value = 20 xIa(50)
UCSupper value = 25xIa(50) CALCULATION OF Is
Uncorrected Point Load Strength Index (PLSI) is calculated from the following formula:
I s = P/ (De)2, MPa
Where I s= Uncorrected Point Load Strength Index, expressed in N/mm2or MPa
P= Failure load, expressed in KN (Kilo Newton)De= Equivalent core diameter, expressed in m( meters)
THE ISRM METHODThe International Society of Rock Mechanics-ISRM-the suggested method to determine PLT strength, thesize correction is used.
Is950) is obtained graphically or by testing a simple of 50 mm diameter maximum
EXAMPLE
Description Values
Distance between two points ,De 4.6 cm 46 mm
Failure load,P 83.582 KN 83582 N
Strength Index ,Is - 39.5 MPa
Corrected strength Index, I(50)
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7.2. AGGREGATE CRUSHING VALUE TEST (ACV)
1. INTRODUCTION
Note: Aggregate Crushing Value (ACV) and Aggregate Impact Value (AIV) are mechanical properties
of aggregate. With such a wide range of aggregates available, an engineer must select a materialsuitable for the project to be doneCertain mechanical properties may be undesirable in a particular project, whilst being imperative
to another.
Resistance to ImpactValueand AbrasionValue(LosAngeles) may be important for aggregates
used in asphalts, but for an aggregate used in an exposed finish decorative concrete these properties may
be irrelevant( less important).
There are many aggregate tests to determine these mechanical properties.
Aggregate Crushing Value(ACV) test is the one among mechanical properties of aggregate.
It gives a relative measure of the resistance of aggregate to crushing under a gradually applied
Compressive Load
REMARK
This test is applicable for aggregate size passing 12.5 mmand retained on10 mmdiameterof sieve. If required or if the standard size is not available; then other sizes up to 25 mmmay be tested.
But owing to the no-homogeneity of aggregates the result will not be comparable with those in thestandard test of 12.5 mmpassing and 10 mmretained
APPARATUS1. Steel Cylinder + plunger+ base plate2. Compression machine
3. Sieves (12.5 mm; 10 mm; 2.36 mm)4. Tamping rod
5. Standard cylindrical measures6. Balance
Aggregate Crushing Value (ACV) apparatus(a) and Compression machine(b)
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PROCEDURE Choose about 6.5 kg of materials consisting of aggregates passing 12.5 mm
and retained on 10 mmdiameter of sieve. Let the aggregate be dried by surface dry condition ( open air drying) Fill the surface (open air) dry condition aggregate; retained on 10 mm diameter sieve; in t
standard cylindrical measure in three layers of approximately equal depth. Each layer is tamped 25 strokes with standard tamping rod (the big one) Leveling the top surface by using the tamping rod or straight edge Weight the sample aggregate contained in the cylindrical measure and record the weight A Place the steel cylindrical in its proper position; on the base plate and fixing it firmly. Pouring the same sample in the steel cylindrical and insert the plunger on the top surface of the
aggregate sample; such that the plunger could not jump from the cylinder
The whole assembly of steel cylinder, test sample and plunger are placed under the load of thecompression testing machine
Apply the load on the plunger up to 40 tons(400 KN) for 10 minutes time Release the load and remove all crushed material from the cylinder metal measure Sieve the removed material aggregate with 2.36 mm diameter of sieve Weigh the fraction passing 2.36 mm diameter sieve and record the weight B. CALCULATION
The Aggregate Crushing Value is given by the following expression
ACV = (B /A) x 100 - expressed in percentage, ( %)
Where B= Weight of crushedmaterial, sieved and passing material (2.36 mm)
A= Weight of surface dry sample (Initial weight) of aggregate
Note: The ACVshould not be more than 40 %for aggregate used for concrete other than for wearing
surfaces. And 30 %for concrete used for wearing road surfaces such a runways and airfield pavements
7.3. AGGREGATE IMPACT VALUE TEST (AIV)
INTRODUCTIONThe Aggregate Impact Value (AIV) gives relative measure of the resistance of aggregate to a sudden
shock or sudden impact. Which in some aggregates differs from its resistance to a slow compressive load?
REMARK:
The test is applicable for sample consisting of aggregates passing through 12.5 mmand retained on 10mmdiameter sieve (the same as for ACV)The sample shall be dried in ovenfor four 24 hours; at the temperature of 105
0C to 110
0C
and freely cooled in the room temperature
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APPARATUS Aggregate Impact Value apparatus comprising: Cylindrical mould (bigger) Cylindrical measure cup (smaller Sieves (12.5 mm; 10 mm; 2.36 mm) Heavy hammers Small tamping rod Blow counter Balance
Aggregate Impact Value (AIV) apparatus
PROCEDURE Dry the sample in open air dry condition (surface dry condition) Adjust the Aggregate Impact Value apparatus and the height of hammer at 380 mm Fill the aggregate sample (dry sample) in the cylindrical metal measure (smaller) in
three layers; and each layer is tamped 25 blows with a tamping rod (the small one)
Determine the weight of the aggregate sample filled into the metal measure; record A. Pouring the prepared and weighed aggregate sample in the cylindrical mould(bigger) Place the cylindrical mould containing aggregate sample on the base plate of the AIV
apparatus and fix it firmly
Allow the hammer to fall freely on the top surface of the aggregate filled into thecylindrical mould; start hammering by 15 blows for 15 seconds time.
Remove the crushed aggregate from the cylindrical