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Transcript of 7314245 Admixtures
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Role Of Construction Chemicals In Ensuring Durability of Concrete Structure
need of major repair and hundreds of crores of rupees is being spent on
restoration. The situation is not much different in other countries. Hence, there
is an not much different in other countries. Hence, there is an urgency to study
the causes of deterioration in concrete and the role of construction chemicals
in making new construction durable and in rehabilitating and construction
durable and rehabilitating and resurrecting structures whose durability is in
question.
So the chemical admixtures are used to modify the properties of
concrete or mortar to make them more suitable for the work at hand, or for
economy, or for such other purposes as saving energy.
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2. PERMEABILITY OF CONCRETE
If concrete is impermeable, corrosive agents cannot penetrate
and attack it. Concrete basically has two types of pores, which determine
permeability. These are capillary pores (with a diameter varying between 0.01
to 10 micron) in the cement, paste which coats the aggregates and larger micro
voids, between 1 mm to 10 mm, which are caused by faulty compaction of
fresh concrete.
When voids are interconnected because of their larger number
and size a continuous link is formed, which makes the concrete permeable.
FACTOR'S CONTROLLING PERMEABILITY
There are three major factors which determine the permeability
in concrete.
(a) Water cement ration,
(b) Compaction and curing.
fig.1. Each factor is equally important, if one of these factors is not controlled,
the result will be increase, in permeability.
It can be shown that permeability increases as water cement
ration increase. Fig.2. Portrays the relationship. Typically, at a water cement
ratio of around 0.4, permeability is practically nill.
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3. TYPES OF ADMIXTURES
Admixtures can act to reduce water cement ratio while
maintaining work ability which is essential for good compaction. Therefore,
work ability is a major criteria for ensuring impermeability in concrete.
Admixtures are used to modify the properties of fresh concrete, mortar, and
grout.
TABLE 2 : TYPES OF ADMIXTURES
Chemical admixture Miscellaneous admixtures
Non-water reducing
Accelerators
Retarders
:
: Air entraining agents
: Integral water proofers
Water reducers Normalplasticizers
Accelerating
plasticizers
Retarding
:
: Pumping aids:
: Bonding agents.
:
: Gas forming.
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plasticizers : Expansion producing.
High range water Normal
reducer.superplasticizers
Retarding
Superplastic
izers
:
: Corrosion inhibiting
: Fungicides: Air detraining
: Flocculating
: Pigments
: Mortar plasticisers
: Grout admixtures
WATER REDUCTION CAPACITY OF ADMIXTURES
Minimum reduction in water for different types of admixtures.
These values are given below in Table 3.
TABLE 3 : WATER REDUCTION FOR DIFFERENT TYPES OF ADMIXTURES.
Category of admixture Water reduction at normal dosage, percentage
Minimum BS: 5057
requirement
Actual in practice
Normal plasticisers 8 8 to 15
Accelerating plasticisers 8 8 to 12Retarding plasticisers 8 8 to 16
Air entraining agents - 2 to 4
Entraining agents - 8 to 12
Normal 16 16 to 35
Superplasticisers
Retarding 16 16 to 30
Superplasticisers
PERMEABILITY REDUCED BY SUPERPLASTICISERS
As per tests were carried out to determine the effect of
superplasticisers on water permeability 150 mm size cubes water stored for 28
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day's in lime - saturated water at 230C and subjected to water pressure on one
face.
Definition of Admixture
In general, an admixture is defined as a material other than
water, aggregate and Portland cement that is added to concrete immediately
before or during its mixing". It was established that, these substances usually,
added in comparatively small quantities, for this reason they have been called
as admixture.
Why is admixture used ?
Over decades, attempts have been made to obtain concrete with
certain desired characteristics such as high compressive strength, high
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workability, high performance and durability parameters to meet the
requirement of complexity of modern structures. To achieve the improved
properties, the use of cementitious/chemical admixture as fourth ingredient
proved to be essential and changes microstructure of concrete depends upon
the quantity of admixture added to concrete. The properties commonly
modified are the heat of hydration, accelerate or retard setting time,
workability, water reduction, dispersion and air-entrainment, impermeability
and durability factors. Admixtures certainly enhance the properties of
concrete and it is humorously suggested that "admixtures are to concrete as
cosmetics to a woman".
Type of Admixture
The present day concrete of the incorporated with an admixture
is modify one or more properties at free of hardened state and are broadly
classified as follows :
Chemical admixtures - Accelerators, Retarders, Water-reducing agents and
Superplasticizers.
Mineral admixtures - Diatomacco earth, Volcanic glass. Calcined clays on
Shales as natural minerals and Fly-as Blast-furnace slag, Silica fume and R
husk bye-product mineral admixture.
Miscellaneous admixtures - Air entraining and Water proofing agents.
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Selection and specific application Selection
Admixtures shall be selected carefully to alter the concrete
properties to the requirement of job at site and shall be used judiciously
according to specification and method of application to avoid adverse effect
on concrete properties at fresh and hardened strata. After selecting the
product, one should carefully choose the supplier, who can supply quality
product, timely service and at competitive price. The compare shall be
reputed one and time tested the business, shall possess the staff with efficient
and professional experience who can guide on effective application/use of
admixture in right way. The admixture shall be supplied with test certificate,
manufacturing date and its chemical composition, shall comply specifications
given by the authorities.
Specific application
The following chemical admixture commonly used for specific
purpose and are explained in detail;
i) Accelerators : Admixtures which are used to speed up the initial set of
concrete is called an accelerator. The advantage of these admixtures are either
to increase the rate of hydration of cement or to shorten setting time results in
early strength development, removal of shuttering, reduction of curing period
and specially when concrete used in low temperature and marine construction.
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The common accelerator is Calcium chloride and rarely Tri-
ethanolamine, Carbonates, Silicates etc., used. However the use of Calcium
chloride is not permitted in Pre-stressed concrete whereas in other concrete it
is restricted to 1.5% by eight of cement content.
Mechanism : According to investigations, the essence of hardening
intensification is CaCl2 as a catalyst acts on hydration of C S results in
increase the rate of setting and strength development. It also established from
the figure 1 that the CaCl2 accelerate the setting time considerably.
(ii) Retarders: The function of retarded is to delay or extend the setting time
of cement paste in concrete. These are helpful for concrete that has to be
transported to long distance in transit mixers and helpful in placing the
concrete at high temperatures, specially used as grouting admixture and water
reducers results in increase of strength and durability.
The commonly known retards are Calcium Ligno-sulphonates
and Carbohydrates derivatives used in fraction of percent by weight of
cement.
Mechanism : The mechanism of set retards is based on absorption. The large
admixture anions and molecules are absorbed on the surface of cement
particles, which hinders further reactions between cement and water i.e.
retards setting. Later as a result of the reaction between the organic salts and
C3A for cement, the former are removed from liquid phase of system, thus
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eliminating further retardation. The figure 2 shows the effect of retards on
setting.
(iii) Water-reducing admixture (WRA) :
The water reducing admixture are group of products which
posses concrete of a given workability as measured by slump or compaction
factor at a lower water-cement ratio than the control concrete.
The commonly used admixtures are Ligno-sulphonates and
hydrocarbolic acid salts.
Mechanism : The principal role on mechanism of water reductions and set
retardation of admixtures are usually composed of long-chain organic
molecules and that are hydrophobic (not wetting) at one end and hydrophilic
(readily wet) at the other. Such molecules tend to become concentrated and
form a film at the interface between two immiscible phases such as cement
and water, and alter the physio-chemical forces acting at this interface. The
presence of such admixture in a fresh concrete results in
(i) a reduction of the interfacial tension.
(ii) an increase in the electro kinetic potentials and
(iii) protection sheath of water dipoles around each particles i.e. mobility of
fresh mix becomes greater, partly because of reduction in inter-particle forces
and partly because of water freed from the restraining influence of the highly
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flocculated system which is now available to lubricate the mixture. Hence less
water is required to achieve given consistency.
(iv) High range water-reducing agents (HRWA) : These are the second
generation admixture and also called as Superplasticizers. These are synthetic
chemical products made from organic sulphonates of type RSO3, where R is
complex organic group of higher molecular weight produced under carefully
controlled condition :
The commonly used superplasticizer are as follows :
i) Sulphonated melamine formaldehyde condensate (S M F C)
ii) Sulphonated napthalene formaldehyde condensate (S N F C)
iii) Modified ligno-sulphonates and other sulphonic esters, acids etc.,
Mechanism : The H R W A consists off very large molecules normally
anionic in nature, are thought to be absorbed on to the cement particles
become negatively charged and subsequently dispersed in the water, similar to
the action of WRA. However the H R W A produce a much higher degree of
dispersion and do not lower the surface tension of water significantly. The
figure 3 shows the mechanism of Superplasticizer with cement and water.
iv) Air Entraining agents : These are generally used to improve workability,
ease of placing, increased durability, better resistance to frost action and
reduction in bleeding.
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The common Air-Entraining agents are natural wood resins,
neutralized vinsol resins, polyethelene oxide polymers and sulphonated
compounds.
Mechanism : These are anionic, because the hydrocarbon structures contain
negatively charged hydrophilic groups, such as COO, SO3 and OSO so that
large anions are released in water. Conversely, if the hydrocarbon ion is
positively charged, the compound is cation active or cationic. In other words,
anionic surface active agents produce bubbles that are negatively charged,
cationic charged cause bubbles to be positively charged, surface active agents
of all classes can cause air entrainment in concrete, but their efficiency and
characteristics of air-void system vary widely.
General Tests on Admixture
Normally the admixture are not tested at site and generally used
based on the guidelines given by manufacturers. However, it is very essential
to ascertain the suitability of admixture with the ingredients used such as
cement, aggregates etc. in concrete. The following tests must be carried out
before using the admixture.
i) Compatibility test - March cone test.
ii) Consistency/Workability - Slump cone or Compaction factor test.
iii) Setting time - Concrete Penetrometer test.
iv) Flow test - Flow table test
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For the large and off-shore structures one should ensure the Choloride and
Sulphate cement of admixture.
Quality Requirement of Admixture
When the admixtures are said to be compatible with concrete, it
should meet the following quality requirement;
i) Characteristics of admixture : The data sheet shall give the characteristic
details such as type of admixtures, available forms, basic material used, details
on dosage and its application methods, precaution to be taken and compliance
with specified standards.
ii) Chemical composition : This is an important parameter and manufacturer
shall furnish details of suitability of admixture with cement available in
market and other ingredients in different environment condition. The
chemical composition such as chloride and soluble sulphate content of
admixture shall comply with specification given by BIS and other
organisation.
iii) Solid content : The solid content will determine the concentration and
efficiency of admixture. Higher the solid contents higher the efficiency and
require less amount of admixture to alter the properties of concrete.
iv) Specific gravity : The consistency of admixture mainly depends on its
specific gravity and depends on solid content. If the specific gravity changes,
the consistency of concrete mix will vary.
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v) Molecular weight : Higher the molecular weight higher the efficiency
when it is used in concrete.
vi) Dosage/Mode of application :
Details of dosage and application methods shall be furnished by
manufacturer for all admixtures.
vii) Compatibility details : Basic compatible details, possible compatibility
problems due to different type of cement and their effects on water demand or
water absorption etc., shall be furnished.
viii) The admixture should not change the hydration process of cement paste
to convert into solid mass and it should not contain high chloride, which will
corrode steel.
ix) Air entrain in the concrete should not exceed 1% unless otherwise
specified.
Adverse effects due to improper application :
Admixtures are used extensively to produce high workable, high
strength high performance and highly durable concrete with minimum cost.
However, these admixtures are not used judiciously and with the poor
knowledge of admixture among engineers at site results in the following
adverse effect on concrete.
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Rapid slum loss : This effect general observed in rich mixes with higher
cement content and it can be reduced by adding booster dosages at different
intervals.
Severe segregation/bleeding : This is generally observed in lean mixes with
low cement content and depends on dosage of admixture. This can be
minimized either by reducing admixture dosage or by increasing content of
fine in the concrete.
Over retardation : This effect a noticed when the admixture is added beyond
the specified dosage and it would effect the construction schedule, result in
low strength development at early age. However ultimate strength of the
concrete remains same.
Plastic shrinkage : This is general observed in large floor slabs of this
sections and due to excess evaporator of water from the surface of the concrete
at high temperatures are continuous breezing. However the plastic shrinkage
cracks are determental to structures.
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Effect of CaCl2 on setting time of OPC
4. ROLE OF ADMIXTURES
Admixtures are used to modify properties of fresh concrete,
mortar and grout so as to.
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(1) Increase workability without increasing water content or decrease the
water content at the same workability.
(2) Retard or accelerate time of initial setting.
(3) Reduced or prevent settlement or create slight expansion,
(4) Modify the rate and or capacity for bleeding.
(5) Reduced segregation.
(6) Improve pumpability, and
(7) Reduced the rate of slump loss.
Admixtures are also used to modify properties of hardened
concrete, mortar and grout so as to
(1) Retard or reduce heat evolution during early hardening.
(2) Accelerate the rate of strength development at early ages.
(3) Increase strength (compressive, tensile, or Flexural, increase durability or
resistance to servers conditions of exposure, including application of deicing
salts.
(4) Decrease permeability of concrete.
(5) Control expansion caused by the reaction of alkalies with certain aggregate
constituents.
(6) Increase bond between concrete and steel reinforcement.
(7) Increase bond between existing and concrete.
(8) Improve impact resistance and abrasion resistance.
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(9) Inhibit corrosion embedded metal and
(10) Produced coloured concrete or mortar.
CONCRETE ADMIXTURES
Fairmate Chemicals, subsidiary of Fairmate Group of companies
dealing in the marketing of chemicals since last Eighteen Years and is engaged
in the Marketing and Manufacturing of speciality construction chemicals and
ready to use products in collaboration of M/s Resin Building Products Ltd.,
U.K. and M/s Morton Chemicals USA. M/s Resin Building Products the
major Principals are one of the pioneers in the technology of Resin Based
Products, and have been in this field for more then two decades. Morton
Chemicals USA are the pioneers in bringing the Poly sulphide based products
in the field of Civil Engineering applications and one of the few companies all
the world manufacturing the basic Poly sulphides.
Fairmate Chemicals in collaborations with M/s RBP US & M/s
Mortons Chemicals USA, has been in the manufacturing & Marketing of High
Quality Construction Chemicals. Fairmate Chemicals to keep ahead in the
competition market has opted for ISO 9002 since its existence as a
Manufacturer and is opting for ISO 14000 in short time.
In the range of Construction Chemicals the Groups of products
offered.
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1. Admixtures
2. Cementitious & Epoxy Grouts
3. Water Proofing Systems
4. Heavy duty Industrial Floors & screeds
5. Prepacked Concrete & Mortar
6. Protective Coatings.
The following section describes the Range of Admixtures
offered by the company.
Fairmate Chemicals has brought new range of Admixtures based
on Naphthalene Formaldehyde & range of admixture based as Acrylic
Polymers to Produce Ultra High Strength, free flowing concrete with or
without Retardation. Products have two ranges the Faircrete-Range, the
Range of Normal high performance Plasticisers & Fairflorange, the range of
high performance Super Plasticisers. In both the ranges the plasticisers
containing retarders are named under Faircrete R range and super plasticisers
are named under Fairflo R range.
Range of plasticiser containing Faircrete N the best seller in
Normal Plasticiser which works excellent for High slump concrete up to 350
kg of cement for normal concrete, for longer retention Faircrete HP is offered
and for retention and retardation application up to 350 kg cement/m3 of
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concrete Faircrete R2 is offered. The above are conforming to ASTM-C494
Type A&D.
In high rang water reducing types, Fairflo we offer Fairflo which
is excellent product for retention of slump for up to 90 minutes without
introducing any retardation if concrete temperature is controlled within 30-
350C.
Further in the range of Accelerators and product offered are
Faircrete NC non-chloride, high performance liquid accelerator for all
Reinforced concrete. Spraycrete a powder accelerator for spray concrete and
Guniting Faircrete a chloride based liquid accelerator offered specifically for
Hollow block construction for faster setting and strength development, less
curing & better finishes. A specialised Air entraining agent Fairmin is offered
for production lightweight concrete.
For Mortar, Fairplast IP, a power admixture is offered which
help increasing the pot life of Mortar reduces dropping of Mortar and
increases the yield of Mortar.
Faircrete RMW, a waterproofing admixture is specially offered
for the waterproofing of all type of concrete floors and slabs.
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ADMIXTURES AND FIBRES FOR IMPROVED CONCRETE
For Roads And Bridges
This article is intended to specifically highlight the conditions of
building roads and the role of speciality chemical admixtures, which facilitate
the construction of highways in adverse conditions.
Concrete Pavement
Construction Condition
It is very difficult to generalise the site conditions for the
construction of a highway since the conditions depend on the terrain
environment and size of the project, which varies from place to place and
project to project.
But more often the conditions affecting tile manufacturing and
performance of wet concrete on site can be summerised below.
Location of concrete manufacturing unit with respect to minimum lead.
Difference in the day and night temperatures and humidity.
The total length of construction defining the increase in lead and lead
time.
The casting method and quantity of concrete consumed per hour
defining the size of manufacturing unit, medium of transportation and
the loading and unloading time (cum/min).
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All the above factors point towards the unique quality of
concrete required.
To be manufactured with following characteristics.
Highly cohesive mix- to enable heavy vibrations for
compactions by paving machine.
Low initial slump- To enable concrete to be carried in dumper
vehicles which will also help fast loading and unloading. Transit mixers with
rotating drum are not capable of delivering more than 1 cum per minute
whereas the consumption of a mechanical paving machine is of the order of
1.6 to 2.0 cum. per minute.
Long retention time- to enable long lead distances to be comfortably
handled. This is the issue of pavement quality concrete since in the
construction of road the casting site changes continuously whereas the
site of production of concrete is fixed.
Minimising the water loss of concrete and lowering tile development of
shrinkage cracks.
The above characteristics make the use of plasticising, water
reducing and admixtures essential.
Fairmate has developed a special admixture (FAIRFLO R13)
meeting all above requirements with further benefits of lowering the initial
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heat of hydration of cement and to hold the water for a longer time, thus
reducing the plastic shrinkage cracks.
Bridges, Culverts And Other Structures On Road
The quantity of structural concrete consumed per minute is not
high since the casting mechanism is manual and the sites are in restricted areas
many a times requiring high slump concrete.
Characteristics of structural concrete required are:
- High initial slump
- Long retention
- Pumpability at the end of retention period.
The special admixture has extensively been used with slight
modification in the control mix to give floatable concrete after 60 minutes and
90 minutes.
Concrete Admixtures with New Concepts
The construction industry has continued to become more
international as the economic climate of the construction industry has declined
in most western countries, so has the need to be involved in overseas contracts
become more important. Many more Engineers are finding themselves
grappling with products, standards and specifications which emanate from
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other countries and working in climatic conditions which make Concrete
Admixtures not only desirable, but necessary.
Also there arc multiple reasons affecting strength and durability
of concrete. Right from the stage of mixing of its constituents, placing into
forms, curing, handling and during service life concrete has some limitations.
Mostly to the requirement of work site, high early strength, retardation,
acceleration and denser quality of concrete etc is necessary. To prepare a mix
for such requirement without affecting the basic concrete properties and
imparting strength and durability, admixtures are required.
In order to take "care" of these specific requirements Apple
Chemic has Admixtures:
1. AC-Plast-BV: Lignosuphonate based chloride free liquid Plasticizer
cum water reducing admixture for achieving impermeable and
improved strength concrete confirming of relevant DIN, BS, IS: 9103:
1979 and ASTM-C-494 specifications. Use of product results in
cement saving. Useful in structural and mass concrete for water
retaining, hydraulic and sewerage structures. Dosage: 0.15 to 0.3%.
2. AC-MENT-BV: Naphthalene Formaldehyde based high early strength
universal liquid Super Plasticizer for producing flowable & pumpable
mix conforming to ASTM-C-494 Type G,IS: 9103 Concrete placing at
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difficult & large places with ease is possible. Dosage (a) Flow concrete
1 to 1.50% (b) Early strength 1.5 to 3%.
3. AC. SUPERPLAST (FF) : Melamine Formaldehyde based liquid super
plasticiser for prestressed and precast concrete confirming to ASTM-
C-194, Type F, BS: 5075 Part III and IS: 9103-1979, Dosage (a) flow
concrete 0.8% to 1.6% (b) High early strength 1.50 to 3%.
4. AC-PLAST-N- High performance liquid Waterproofer for all types of
water retaining structures for all concrete grades, mortars & plasters.
Confirming to ASTM-C-494 IS:2645 and IS:9103-1979. Dosage-0.3%
to 0.5%.
5. AC-RETARD- Retarding liquid Superplasticizer. Delays initial setting
& makes concrete flowable. Useful in hot climate confirming to
ASTMC-494-Typc D& IS:9103: 1979. Dosage 0.3% to 0.5%.
6. AC-IMPRO-Integral Waterproofer for all cement based works
confirming to IS:2645:1979 in powder & liquid form. Dosage : @ 2%
7. AC-SET-FAST- Liquid Accelerator gives rapid strength to
concrete/mortars suitable for all cement grades. Dosage-Depends on
reduction in setting time required.
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A Novel Admixture-KR-2 Emulsion
It is well known that the properties of the cement can be altered
by using suitable additives. These additives are known as admixtures and are
materials used in used in cement mortar and cement concrete lo improve or
impart some of its properties.
They are defined as material, other than cement, water and
aggregate, that are used as an ingredients of concrete and are added to the
batch immediately before or during mixing. A proper use of admixtures offers
certain beneficial effects to concrete, improved quality, acceleration or
retardation of setting time, enhanced frost and surface resistance, control of
strength development, improved workability, and enhanced finishability.
The use of these admixtures and additives has been a matter of
controversy and several technologists have discouraged the use of these
admixtures. But there are many on the contrary, who highly commend and
foster the use and development of admixtures as they impart many desirable
characteristics and effect economy in concrete construction.
There are large number of proprietary products available in the
market with their effects described but the full details of the action of these
additives, known as admixtures are yet to be determined and the performance
of the admixtures should be carefully checked before use.
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Admixtures are classified according to the purpose for which
they are used in concrete, (1) Accelerating admixtures (Calcium Chloride) (2)
Retarding admixtures (3) Water reducing admixtures and also the so called
superplasticizers.
There are other additives like air entrainment admixtures etc.
there exist additives for other purposes also such as water proofing and
fungicidal action etc., but it may be noted that these are not sufficiently
standardized. Here it suffices to say that waterproofing admixtures (Calcium,
Ammonium Stearate, Butyl Stearate, Calcium Oleate etc.) are supposed to
repel water by an electrostatic charge which they form after reacting with
calcium ions on the walls of the capillaries in the hydrated cement paste. It is
doubtful whether this effect persists over long periods.
For fungicidal purposes, Copper Sulphate and
Pentachlorophenol have been suggested. These also control the growth of
algae or lichen on hardened concrete but again their effectiveness is lost with
time. Needless to say toxic admixtures should not be used.
To understand the present status of admixtures, it would be
appropriate to quote from "Properties of Concrete by A.M. Neville".
"An important feature of majority of admixtures for concrete is
that they are used primarily on the basis of experience or adhoc tests. The
theoretical information
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on a scientific basis is generally not available to permit a reliable quantitative
prediction of behaviour in concrete under the various possible circumstances.
This is due to the marketing of admixtures largely as proprietary products. In
view of the above, it is important that admixtures should be used judiciously
and will proper instructions, because of these different views and difficulties
faced by the users.
Tech-dry (India) Pvt. Ltd; has develop a novel Emulsion-KR2 which has not
chemical admixtures are added concrete in a small amount mainly the
entrainment of air, reduction of water or cement content, plasticization of the
concrete mixtures, or control of setting time and based on that they are divided
in the following categories.
Air-Entrainment
Water-Reducing
Set-Retarding
Accelerating
Superplasticizers
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However, EMULSION-KR2 emulsion solvent-free aqueous organic copoly
water based emulsion. This unit Emulsion creates hydrophobicity in pores and
capillaries and therefore evaporation is slow and the water already present
enables the hydration. Because of its unique ability to create this
hydrophobacity. It reduces the water absorption by 80% besides increases the
compressive and flexural strength.
Description
Emulsion KR-2 is designed to be unit as an admixture during in-
placing manufacture of slow slump, cementitious containing blocks products
as admixture in ready-mix-concrete freshly made concrete and MORTOR
FOR PLASTE.
1. When EMULSION-KR2 incorporated into low slum cementitious products
such as imitant stone blocks and pavers, the permeability to water and the
occurrence of unsighted efflorescence is dramatically reduced. Additionally,
the 28 day compressive strength and transverse breaking by the strength
increased by up to 50%.
Superment-F10: A Revolution in Dry Mortar industry
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Building Materials technology is changing rapidly with the
development of new innovative materials. Concrete is no longer a mixture of
one, two and three shovels of cement, sand and coarse aggregate respectively.
It has matured enough to lead us into the 21st century.
Dry mortar is one of the major parts of that revolutionary
change. The concept includes
a) Gypsum and gypsum hydrated lime mortars.
b) Cement and cement hydrated lime mortars.
Such mortars based on mineral or binder combinations can be grouped into
Self-leveling floor screeds Repairs. External paints. Grouts Injection mortars,
Underwater concrete Depending on the applications, such blends require
adjustment to their characteristic properties like Consistency, Flowability,
Strength, Surface hardness etc.
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Superment - industrially called Superment-F10, is a powder admixture based
on water soluble melamine polymer. Superment-F10 makes it possible to
formulate tailor made dry mortar products ready for use on the building site
requiring only the addition of water. When water is added to the dry mortar,
Superment-F10 goes into solution with the other binders and the dispersing
effect of polymer can be used to obtain the required consistency or reduce the
water demand and of course both characteristics at the same time Superment-
F10 can also be used to increase properties and stability towards segregation,
increased adhesion or wear resistance.
1. Self leveling floor screeds
Floor screeds are in most cases based on high alumina cement,
which combined with gypsum results in a reduced shrinkage and a high degree
of chemical water binding. With Superment-F10 combined with set
regulation chemicals, resin copolymer, filler and suspension additives, it has
been possible to develop many different
floor screed products which fulfill very high quality requirements such as
hardness, evenness, low emission, etc.
2. Repairs
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With concrete structures built 30 years ago becoming weak.
repairs to protect these structures have become increasingly important. There
are repair products with different applications and different properties such as
consistency, setting time, strength, wear resistance, etc. With Superment-F10,
it is possible to adapt and even increase the properties of these products.
3. Cement Based Paints For External Use
A plastered facade with a cement based paint in pleasant color
gives a classic and elegant appearance. Cement based powder paints for
external use often contains coloring pigments, copolymers and fillers. The use
of Superment-F10 enables the effective dispersion, a reduction of water
content and an increase of coloring effect. It enables better utilization of the
pigments and the cements, thereby also enabling the reduction in the quantities
of these additives.
4. Grout
The need for grout exists when there is built up in different
ways. There are products with different levels and times of expansion.
Common points between all the types of grout are the need for high early and
final strength, a low water-cement ratio and an ability to flow and fill under
difficult conditions.
Superment-F10 is excellent for formulating this type of grout
and gives all the required properties.
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5. Injection Mortar
When there arc sonic cracks in rocks, in concrete or in soil to
stabilize, it is possible to inject different types of grouts. The most common
type is cement slurry but because of the settlement and requirement for good
flow with a low water demand, it is necessary to modify the grout. The
excellent water reduction effect of Superment-F10 can be used to give very
good flow even with very low water/cement ratio.
6. Underwater Concrete
For underwater concrete , it is important to design the concrete
very carefully to minimize the risk of separation and wash out the cement
paste in the water. The use of micro-silica and of the water reducing admixture
increase the properties but to ensure that the concrete can be used in an
optimal water, it is often advised to add a stabilizing agent. More-ever for
underwater concrete, it is necessary that the cement has a good flow since
manual finishing is impossible.
Thanks to Superment-F10, there are many possibilities to
formulate admixtures with all necessary properties combined in one product.
5. COST ASPECT
Through diffusion coefficients in concrete do not follow linear
relationships, by using curve fitting techniques. It can be shown that in the
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given situation the life of a concrete structure, say for example, a bridge which
would normally have lasted a period of 25 years, would have an extra span of
10 year. The cost of using construction chemicals as admixtures, sealants,
curing membranes and protective coatings, in comparison to the extra lease of
life is insignificant.
6. CONCLUSION
Admixtures, sealants and curing membranes could be used to
ensure structural curability despite the higher initial costs. These initial costs
would be more than compensated several times over by the enhance life of the
structure. In aggressive environments it may be prudent to go in for
appropriate protective coating. The argument about cost versus enhanced life,
equally holds here as well.
7. REFERENCES
1. Concrete Technology
- By Mr. M.S. Shetty
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2. Soil Mechanics & Foundation Engg.
- By Dr. K.R. Arora
- Dr. B.C.Punmia
3. Constructional Material
Jer. 2000, vol. 6
4. M/S Fairmate Chemicals Pvt. Ltd.
E-mail: [email protected]