Performance Indices for a Simulated Strawbale _sb_ Masonry Sprayed With Fibre Reinforced

8/11/2019 Performance Indices for a Simulated Strawbale _sb_ Masonry Sprayed With Fibre Reinforced

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Websjournal of Science and Engineering ApplicationISSN: 1974-1400-X, Vol 2, No 2, 2013, 103-112

A.A. Adedeji, V. S. Kamara and D. P. Katale

104Websjournal of Science and Engineering Application//Lyon _ AIGEN

cement plastered and unplastered strawbale as well as the unsprayed termitarium plastered strawbale.

The methodology of this project includes production of strawbale specimens of plastered and

unplastered sprayed blocks and prisms. The termitarium plastered strawbale were initially tested and itssimulation carried out at the Department of Civil Engineering, Namibia University of Science and

Technology (Kamara et al, 2012). The result of the present work is hereby compared with that of the

termitarium plastered wall. A typical thermal conductivity of natural (coconut) fibre, due to changes in

temperature, is shown in Table 1.

Table 1. Experimentally determined ()for coconut fibre

Density (kg/m ) Thermal Conductivity (W/mK)

15.6C mean temp. 21.8C mean temp.

40 0.05624 0.0575850 0.05099 0.05184

60 0.05051 0.04970

70 0.04891 0.0488480 0.04800 0.04886

90 0.04869 0.05009

Source: Aridome et al (1998)

2. SPRAYED FIBRE REINFOCED PLASTICS REVIEW

Closed-cell spray polyurethane foam (ccSPF) insulation is a self-adhering, two-component productthat is spray applied on site. The material tenaciously bonds to most construction material substrates(i.e. metal, wood, plastic, masonry) and provides a rigid insulation system that adds structural strength

to buildings. It has the highest level of thermal performance per mm, for commonly used thermalinsulation products. Typically, this performance shows a design R-value of 6.2 for 0.91 kg at 23.89oC

for ccSPF wall insulation, and a design R-value of 6.7 for 1.36 at 23.89oC(ccSPF) roof insulation at a

mean temperature of23.89oC(ASTM C 518 04).Closed-cell spray polyurethane foam also has nearly

zero air permeability and acts as an integral vapor barrier. Because the product is sprayed onto thesubstrate and expands to nearly 30 times its original volume when applied, it conforms too many

irregular spaces and fills voids that other insulation materials leave open. It requires no fasteners and istypically installed in a single application (CES, 2007). The Open-cell spray polyurethane foam (ocSPF)

utilizes carbon dioxide as the sole blowing agent. In ocSPF, the cells burst open and are suspended in

the finished foam in an open form.

In walls, ccSPF insulation can be used throughout the interior or exterior of a structure and may beapplied to nearly any construction surface (i.e. masonry, gypsum board products, wood, metal),including exposed or new construction wall framing. Closed-cell spray polyurethane foam wall-

insulation systems provide a continuous air barrier, improved building strength and significant thermal

performance. The system addresses all key issues associated with insulation and air-barrier systems incommercial insulation performance, because of: Superior effective R-value in a complete assembly. A

monolithic, integral vapor and air barrier that requires no additional products to reduce air andmoisture infiltration and exfiltration, thereby exceeding building codes and standards and meeting

ASTM C1029/SPFA guidelines. Low water vapor permeability, low liquid water absorption and highthermal performance, which combine to minimize condensation and water intrusion into the building

(Banthia, 2002). Complete coverage of the building envelope (i.e. roof, walls, foundation and slab),which minimizes thermal bridging caused by fasteners, joints, cracks, penetrations and framing.Finally, ccSPF insulation and waterproofing systems employed in the building envelope (i.e. roof,

walls, foundation and slab) can substantially improve the structural integrity of the building. In fact,

studies show that using ccSPF insulation in walls increases racking strength two to three timescompared to assemblies using traditional insulation products. Using ccSPF as a wall-insulation system

provides significant energy-related benefits. In addition to significantly higher R-value than other

insulation materials, ccSPF eliminates moisture and air infiltration and exfiltration. Thermal testing

standard of R-13 of SPF cells and other polystyrenes are shown in Table 2.


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Table 2. Current thermal testing standardsInsulation ASTM Standard Mean Test Temperature

Differential, F (oC)

Temperature, F (oC)

R-13 Fiberglass with

paper facing

ASTM C 653 75 (23.89) 40 (4.44)or 50 (10)

Extruded polystyrene ASTM C 578 25 (-6.67), 75 (23.89) 110 (43.33) Min 40 (4.44)

Polyisocyanurate ASTM C 1289 40 (4.44), 75 (23.89) 110 (43.33) Min 40 (4.44)

Closed-cell sprayfoam insulation

C 1029 40 (4.44), 75 (23.89) 110 (43.33)Min 40 (4.44)

Open-cell spray foaminsulation

None 75 (23.89) Min 40 (4.44)

Source : (CES, 2007)

3. MATERIALS PROPERTIES AND CONSTRUCTION OF SB MASONRY

3.1 Strawbale wall as energy efficient

The use of straw as insulation means that the standard insulation materials are removed from the home

standard fiberglass insulation has formaldehyde in it, a known carcinogen bale walls also eliminate theuse of plywood in the walls. Plywood contains unhealthy glue that off-gas into the house overtime

(Downton 2003, Lancinski and Bergeron 2000), which can endanger the occupants. A house envelopedwith a strawbale wall can save up to 75% on heating and cooling costs intact in most climates, we do

not even install air conditioning unit into strawbale building as the natural cooling cycle of the planet

are enough to keep the house cool all summer long(Downton, 2003). Likewise, Adedeji and Aweda(2013) and Adedeji (2007) postulated that all new buildings must be energy efficient with straw walls,

the insulation (straw) is also the building block. Also Lee (2001) indicated straw compacted into balesoffers much better insulation with its high thermal resistance.

3.2 Materials used for specimen construction

DataBase used for this research work was based on experimental tests on strawbale wall - also reportedherewith - were conducted by Samuel (2012). The following materials were used: Mature straw of

guinea corn stalk (cut to size of three strings), ordinary Portland cement (OPC), fine aggregate, steel

wire/twine. The fine aggregate used was clean, soft, well graded, freed from salt and organic

contaminant of 100% passing through sieve no 5mm was employed in the mix. Two different specimensamples were prepared, one in which strawbale was unplastered and other specimen plastered withSFRP.

3.3 Particle size distribution tests and results

500g of dry fine aggregate sample, which passes through sieve no. 5mm, weighted and complied with

BS 882:1201. This was employed in the mix. The natural sand used was well graded in conformity

with the limit given in the Table 1 of BS 882:1201. The result of the sieve analysis carried out is shownin Table 1 and in Figure1, for the number of different sized particle available, BS410: 1976 was

employed for the production of the block specimens.

Table 1 Sieve analysis result or grading of sand for blockSieveSize (mm)

Sieveweight

(g)

Sieve weight +retained

(g)

Retainedweight (g)

Percentageretained %

Cumulativepercentage

retained

Cumulativepercentage

passing5 100

4 554 558 4 0.8 0.8 99.2

2.36 478 493 15 3 3.8 96.22 520 565 45 9 12.2 87.20.5 496 641 145 29 41.8 58.20.25 472 582 114 22.8 70.8 29.20.063 455 552 97 19.4 90.2 9.5Recording pan 254 303 49 9.8 1 00 0

Percentage retained = (weight retained/total weight of sample) x100%


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106ebsjournal of Science and Engineering Application//Lyon _ AIGEN

Figure 1 Particle size distribution curve

3.4 Spraying of strawbale

The spray was applied to the strawbale by a compressed pump machine. The polymers were mixed andpoured into the compressed pump machine gun after which the polymer fibre reinforced cement mortar

was sprayed out of the guns nozzle toward the surface of the strawbale. Contained in the mix waspaint DALUX 01202092 with a base, hardener and reducer in ratio 2:1:02 (that is, 2 part base, 1

hardener and 0.2 reducer). The surface of the strawbale was cleaned and free of dirt, grease, oil, wateror other contaminants. A total of sixty coupon specimens of each sprayed FRP were prepared as Type

A test pieces. Thirty specimens were made with carbon fiber (CF), and the other thirty specimens for

glass fiber (GF). The installing procedure of the sprayed FRP strengthening is as follows:i) Base arrangement; other extra fin leaves on surface of strawbale (SB) prism were trimmed using

scissors.ii) Primer resin coating; Primer resin was applied to the surface in order to make highly adhesive

between SB and putty/resin.

iii) Putty arrangement; Dent areas and steps on SB surface are filled with putty and made the surfaceflat in order to prevent partial stresses of FRP and air voids on SB. After putty got dried, the

surface was thoroughly sanded.

iv) Resin coat; In order to make fibers more adhesive, resin was coated first by a spray gun. Maximum

lengths of the carbon and glass fibers are 0.5mm and 0.2mm respectively.

0

20

40

60

80

100

0.001 0.01 0.1 1 10

PERCENTAGEFINER(%)

PARTICLE SIZE (mm)

Figure 2 SFRP plasteredStrawbale prism before loading

Figure 3 Failure mode in ruptureand splitting


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107ebsjournal of Science and Engineering Application//Lyon _ AIGEN

In this study however, it was a goal to obtain sufficient behaviours as applicable to the wall element

by factoring the results of the prism (Adedeji, 2007). Figure 2 shows typical FRP sprayed strawbaleprism, while Figures 3, 4 and 5 show typical failure modes of the prisms subjected to compressive

strength test.

3.5 DataBase

Mechanical properties of carbon and glass fibres are shown in Table 2 and database for specimensare also indicated in Table 3.

Table 2. Mechanical properties of FRP and plastered strawbale and TSB

Identification Tensile Strength(MPa) Elastic Modulus(GPa) Ultimate strain (%)

CF-A1** 4451* 254.1* 1.76

GF-A2** 2378* 127.1* 1.87CF-A3** 117.1 15.24 0.78

GF-A4** 112.9 8.00 1.48

T-SB*** - 6.00 -* For sectional area of only fiber (not included resin)

**(Toshiyuki, c_kanakubo_final_pdf)*** Kamara et al (2012)

T-SB = Termitarium Strawbale composition, thermal conductivity =0.020 0.035

Table 3. Prism specimensSpecimen Section FRP FRP (Specified values)

(mm) Length (mm) Arrangement pFRP(%) Elastic modulus (GPa) Thickness (mm)

CF- A1 254.1 0.5GF- A2 250 *450 1000 Mixed 0.13 127.1 0.16CF-A3 15.2 0.2GF-A4 8.0 0.13

pFRP= Percentage of FRP

3.6 Compressive strength test results

The characteristic values of axial compressive strength of the SFRP masonry prisms are obtained

from the compression test results on full height prism subjected to eccentric loading. In general, it isconservative to assume pinned-pinned condition and it may be noted that for design purposes, the

characteristic values should be divided by partial safety factor 1.7 and maximum of 3.3 (Adedeji, 2000)

Compressive strength applied in this study involved the capacity of the masonry to withstand axialload only. When the limit of compressive strength is reached, materials are crushed. Tables 4 to 7

Figure 4 Sprayed plastered strawbale

prism splitting under loading

Figure 5 Sprayed plastered strawbale prism

crushing under loading


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shows the average compressive strength test results on sprayed and unsprayed plastered strawbale

prisms with their standard deviation.

Table 4. Average compressive strength for sprayed cement plastered strawbale prism

Analysis Plan Area

(mm2)

Crushing load

(N)

Compressive strength (N/mm )

Prism Actual wall

Mean Value 85.6 x140.6 7838.77 0.65 6.5

Standard deviation 1192.75 0.092

Table 5. Average compressive strength for unsprayed cement plastered strawbale prism

.

Table 6.average compressive strength for sprayed cement unplastered strawbale prism

Analysis Plan Area

(mm2)

Crushing load

(N)

Compressive strength (N/mm )

Prism Actual wall

Mean Value 85.6 x140.6 7838.77 0.65 6.5Standard deviation 1192.75 0.092

Table 7.average compressive strength for unplastered strawbale prism without spray

Prism model is factored by 0.1 of the actual wall dimensions

For the height of the strawbale prism, HP = 1m and thickness BP = 0.45m, the maximum stressesallowable and calculated using SAP2000 are also shown in the Tables 8 and 9for both cement

(Adedeji, 2011) and termitarium plaster composition (Kamara et al, 2012).

Table 8.Minimum and maximum stresses (N/mm2) between each of the plaster compositions

and the strawbale material.

Outside plaster Inside plaster

Plaster composition Minimum stressMaximum

stressMinimum stress Maximum stress

*Cement -9.8 9.6 -19.3 18.3

Termitarium -6.0 6.2 -6.3 6.5

*Adedeji (2011), Kamara et al (2012)

Table 9Differences between the allowable and calculated stresses for both plaster compositions.

Wall composition Maximum allowable stressMaximum calculated stress using

SAP2000*Cement plastered strawbalewall

70.14kN/m2 38.836kN/m

2

Termitarium plasteredstrawbale wall

73.14kN/m2 67.452kN/m

2

*Adedeji (2011), Kamara et al (2012)

Analysis Plan Area(mm

2)

Crushing load(N)

Compressive strength (N/mm )Prism Actual wall

Mean Value 85.7x140.6 7305.7 0.61 6.1

Standard deviation 865.28 0.076

Analysis Plan Area(mm

2)

Crushing load(N)

Compressive strength(N/mm )Prism Actual wall

Mean Value 85.8 x 140.5 5297.4 0.44 4.4Standard Deviation 727.14 0.061


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5. DISCUSSION OF RESULTS

Due to the tests carried out on strawbale prisms and simulation, the results are presented as follows:In a sprayed fibre reinforced plastics walls, thepeak values for the state of stress and deformation occur

in the same minute cycle of temperatures. So, the results of thesimulation of temperature for the stress

and deformation indicate the rational 'stress and deformation tolerance 'in which the wall situates, The

section of an SFRP of the strawbale (SB)wall plastered with cement mortar has minimum compressive

stress (outside wall-surface) of 8.839, 8.034 and 7.001 N/mm2

at eccentricity, e = 0, e = 6 and e =20mm and the length of 1.0 m respectively, while the compressive stress (inside wall-surface of 0.1

N/mm2 occurred

at 20 hrs respectively. The case is different with a two-sideplastered wall, where the

tensile stress of 1.8N/mm2was recorded at 15 hrs, while the compressive stress of 0.5 N/mm

2occurred

at 24 hrs. The maximum (normal) stress at the contact of the wall and the FRPplaster outside the wallis 1.3N/mm2and it occurred at 20hrs. The shear stress along the contact is in compression with a

maximum value of 0.2N/mm2in the 23hrs. This is not the case with the wall plastered on both sides

where tensile stress occurs in the 14hrs mid the shear stress (compressive) occurs in the 20hrs .The

SFRPplastered wall is very sensitive to thermal movement, from 'all indications,when compared with

both cement plastered and termitarium plastered SB wall and so is the compatibility (bond) between thewall elements and the plasters. The high bond stress is due to the field of stress by the modulus of

elasticity of SFRP plaster and the strawbale surface area. Though, a modular ratio (ESFRP/ESB) of 1.33gives moderate compatibility between the two materials, the time cycle for this rapid change may affectthebond between the two elements as yearspassby. This maybe more damaging at any slight daily

swings of temperature. Temperaturepatterns forboth plastered and unplastered wall arethe same.

6. CONCLUSION

The performance of sprayed fibre reinforced polymer plasters, on strawbale prism, has beenidentified by this research work. The results obtained were factored 0.95 (Adedeji, 2007) to obtain the

values for the wall. Strawbale wall has shown adequate resistance against vertical loading. Comparison

of results was made between plastered and unplastered strawbale with spray, unplastered and plastered

strawbale without spray. Spray-plastered strawbale have stresses of 8.838N/mm2over 8.387N/mm

2of

unsprayed plastered strawbale with the sprayed FRP thermal conductivity ranges between 0.020and0.035.This implies that when higher loading such as the above stresses occur, the response of the

fibre reinforced cement plastered strawbale is high compared to other unsprayed strawbale wall. From

this work however, it could be recommended that strawbale sprayed plastic fibre mortar should beemployed for sustainable, strong and ecosystem compatible buildings; as there is a strong indication of

a moderate bond between the SFRP of both cement and termitarium plaster and the SB surface areaeven, on the west wall, at 700 W/m2solar gain at a temperature of 43.33oC.

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Performance Indices for a Simulated Strawbale _sb_ Masonry Sprayed With Fibre Reinforced

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