Strength and elastic properties of powdered and aqueous polymer-modified mortars

The effectiveness of powdered emulsions (powdered cement modifiers) and aqueous polymer dispersions (aqueous cement modifiers) on improvements in strength and elastic properties of mortars is investigated in this paper. Polymer-modified mortars using various powdered and aqueous cement modifiers were prepared with variation in polymer-cement ratio, and tested for flexural strength, compressive strength, tensile strength, deflection, extreme tensile fiber strain and tensile strain. It is concluded from the test results that powdered cement modifiers affect the properties of mortars similarly as the aqueous cement modifiers and the powdered polymer-modified mortars can be used in the same manner as the aqueous polymer-modified mortars for practical applications.

iii'i 'i Cementand ConcreteResearch,VoL24, No.7, pp 1199-1213.1994 i!ilili!iiiiiiiiill Copyright© 1994 ElsevierScienceLtd iiiiiiili~ii Printedinthe USA All fightsreserved i~iii~i~i iiiiiiiilliliil 0008-8846/94 $6.00+.00 ii!i~m~i~ Pergamon iiiiiiiii i!i i!iii!il~ii ii:iiiiii!Tiii 0008-8846(94) 00064-6 STRENGTH AND ELASTIC PROPERTIES AND AQUEOUS POLYMER-MODIFIED OF POWDERED MORTARS i~ii:~iiii~'ii i!i'iii'ii~ii',li~ i~'~:~i' !:' ~:iiiii, Musarrat Ullah Khan Afridi and Zia Ullah Chaudhary Cement Research and Development Institute, State Cement Corporation, Near Lahore Race Club, Kot Lakhpat, Lahore, Pakistan Yoshihiko Ohama and Katsunori Demura Department of Architecture, College of Engineering, Nihon University, Koriyama, Fukushima-ken, 963 Japan Muhammad Zafar Iqbal Institute of Chemistry, University of the Punjab, Lahore, Pakistan (Communicated by M Daimon) (Received October 29, 1993; in finalform February 9, 1994) ABSTRACT The effectiveness of powdered emulsions (powdered cement modifiers) and aqueous polymer dispersions (aqueous cement modifiers) on improvements in strength and elastic properties of mortars is investigated in this paper Polymer-modified mortars using various powdered and aqueous cement modifiers were prepared with variation in polymer-cement ratio, and tested for flexural strength, compressive strength, tensile strength, deflection, extreme tensile fiber strain and tensile strain It is concluded from the test results that powdered cement modifiers affect the properties of mortars similarly as the aqueous cement modifiers and the powdered polymer-modified mortars can be used in the same manner as the aqueous polymer-modified mortars for practical applications Introduction Polymer-modified mortars using aqueous cement modifiers are widely used as high performance, low-cost construction materials particularly for finishing and repairing works because of their excellent performance and durability A recent advance for the preparation of polymer-modified mortars is the invention of powdered cement modifiers with improved qualities Much interest is focussed nowadays for the usage of mortars modified by such powdered cement modifiers in U.S.A., U.K., Germany, Japan and elsewhere in the advance countries of the world But sufficient data are not available on the performance of powdered cement modifiers or on the properties of mortars modified by them The purpose of this paper is to evaluate and compare the performance of powdered and aqueous cement modifiers in improving the strength and elastic properties of mortars or to evaluate and compare the strength and elastic properties of powdered and aqueous polymer-modified mortars In this paper, polymer-modified mortars using four types of commercially available powdered cement modifiers and two types of commercially available aqueous cement modifiers were prepared with various polymer-cement ratios and tested for flexural strength, compressive strength, tensile strength, deflection, extreme tensile fiber strain and tensile strain 1199 1200 M.U.IC Afridiet al Vol 24, No Materials Cement and Fine Aggregate Ordinary portland cement and Toyoura standard sand as specified in JIS (Japanese Industrial Standard) were used in all mixes Cement Modifiers Commercially available, four powdered and two aqueous cement modifiers were used The powdered cement modifiers used included one brand of poly (vinyl acetate-vinyl carboxylate) (VA/VeoVa) type and three brands of poly (ethylene-vinyl acetate), (EVA) type The aqueous cement modifiers used were one brand of EVA emulsion and one brand of styrene-butadiene rubber (SBR) latex type Their typical properties are given in Table Before mixing, a silicone emulsion type antifoamer containing 30% silicone solids was added to the cement modifiers in a ratio of 0.7% of the silicone solids in the antifoamer to the total solids in the powdered and aqueous cement modifiers Table Typical Properties o f C e m e n t Modifiers Type of Cement Modifier Stabilizer Type Powdered VA/VeoVa Emulsion Anionic Powdered EVA-1 Emulsion Anionic Powdered EVA-2 Emulsion Anionic Appearance Milky-White Powder without Coarse Particles Milky-White Powder without Coarse Particles Milky-White Powdcr without Specific Gravity (20 °C) pH Viscosity (20 °C) (20 °C,cP) Total Solids 1.100 1.180 1.120 Coarse Particles Powdered EVA-3 Emulsion Anionic Milky-White Powder wilhout Coarse Parliclcs 1.180 EVA Emulsion Anionic Milky-White Aqueous Dispersion 1.056 5.2 16()0 44.4 SBR Latex Anionic Milky-White Aqueous Dispersion 1.019 8.5 155 45.8 Vol 24, No STRENGTH,ELASTICPROPERTIES,AQUEOUSPOLYMERS,MORTARS Testing Preparation 1201 Procedures of Mortars Powdered and aqueous polymer-modified m o r t a r s were mixed according to J I S A 1171 (Method of Making Test Sample of Polymer-Modified M o r t a r in Laboratory) as follows: cement: s t a n d a r d sand = 1:3 (by weight), p o l y m e r - c e m e n t ratios, P / C (calculated on t h e basis of total solids in powdered and aqueous c e m e n t modifiers) of 0,5,10,15 and 20% a n d t h e i r flows were adjusted to be constant at 170 + The mix proportions of polymermodified m o r t a r s are given in Table Table Mix Proportions of Polymer - Modified Mortars rype of Mortar Unmodified Powdered VA/VeoVaModified Powdered EVA-IModified Powdered EVA-2Modified Powdered EVA-3Modified EVAModified SBRModified Cement:Sand (by weight) Polymer - Cement Ratio (%) 1:3 1:3 1:3 1:3 1:3 Flexural and Compressive Flow 77.5 165 10 15 20 72.2 75.5 76.2 75.0 172 172 173 168 10 15 20 73.8 75.2 73.0 73.8 170 173 170 172 10 15 20 76.2 76.5 76.2 76.2 167 168 172 168 10 15 20 76.2 76.5 77.5 77.5 168 170 168 169 10 15 20 72.5 66.8 63.0 59.8 I70 167 167 168 10 15 20 74.2 70.6 62.8 57.7 172 168 168 168 1:3 1:3 Water-Cement Ratio (%) Strength Tests Beam type m o r t a r specimens 40x40x160 m m were moulded, and subjected to a 2day-20°C-80% r.h.-moist, 5-day-20°C-water, and 21-day-20°C-50% r.h.-dry cure The cured specimens were t h e n t e s t e d for flexural and compressive s t r e n g t h s according to JIS A 1172 (Method of Test for S t r e n g t h of Polymer-Modified Mortar) using I n s t r o n - a n d Amsler-type universal t e s t i n g machines 1202 M.U.K.Afridiet al Vol.24, No Tensile Strength Test Briquet mortar specimens were moulded, and given a 2-day-20°C-80% r.h.-moist, 5day-20°C-water and 21-day-20°C-50% r.h.-dry cure The cured specimens were then tested for tensile strength according to ASTM C 190 (Standard Test Method for Tensile Strength of Hydraulic Cement Mortar) using an Amsler-type universal testing machine Deflection and Extreme Tensile Fiber Strain Measurements During the flexural strength test as mentioned above, deflection and extreme tensile fiber strain (the fiber strain on the tension side of the specimens) were also measured The deflection was measured by attaching glass plates to the specimens and with the help of non-indicating displacement transducers Whereas, the extreme tensile fiber strain was measured by means of wire strain gauges attached to the center of the specimens The data so obtained were recorded on automatic recorders Tensile Strain During the tensile strength test as mentioned above, tensile strain was also measured by attaching wire strain gauges to the center of the specimens where the tensile stress occurs along the longitudinal direction The data so obtained were recorded on a automatic recorder 1~o Powdered Powdered Powdered Powdered F'.VA - SBR - VA/VeoVa- EVA - I - EVA-2- EVA-3- Modified Modified Modified Modified Modified Modified / IOO i f 50 h I o Ib,'s Lbl] o Polymer - b ab zo C~meflt Ratio b tbl o 6stbt 2b (%) Figure Polymer-Cement Ratio vs Flexural Strength of Powdered and Aqueous PolymerModified Mortars Vol 24, No STRENGTH,ELASTICPROPERTIES,A Q ~ U S POLYMERS,MORTARS Test Results 1203 and Discussion Figure shows the polymer-cement ratio vs flexural strength of powdered and aqueous polymer-modified mortars Figure depicts the polymer-cement ratio vs compressive strength of powdered and aqueous polymer-modified mortars Figure represents the polymer-cement ratio vs tensile strength of powdered and aqueous polymer-modified mortars It is apparent from the above figures that except for powdered VA/VeoVa-modified mortar with a P/C of 5%, the addition of both powdered and aqueous cement modifiers to mortars generally increases their flexural, compressive and t e n s i l e strengths The powdered and aqueous polymer-modified mortars (PAAPMMs) show an improvement in flexural and tensile strengths mainly due to an improved bond between aggregate and matrix(i) or due to an improvement in sand-matrix adhesion level or due to an overall improvement in cement-hydrate-aggregate bond because of a decrease in watercement ratio and higher flexural and tensile strengths of polymer films present in PAAPMMs(2,3,4,5) Whereas, the increase in compressive strength of PAAPMMs is attributed mainly due to a reduction in water-cement ratio(6,7) which ultimately affects the gel - space ratio thereby causing a reduction in the capillary porosity of the system(6,8) and helping the pore maxima of pore size distribution range to shift towards the pores of the finer porosity(9) Polymer films present in such PAAPMMs may also contribute towards the compressive strength hike but to a lesser extent(10AD On the other hand, the slight reduction in compressive strength of powdered VA/VeoVa-modified mortar with a P/C of 5% is associated with its highest air content i.e 13.1% (9) The results reveal higher and pronounced gains in flexural and tensile strengths of PAAPMMs as compared to those in their compressive strength However, the magnitude to which the flexural, compressive and tensile strengths of PAAPMMs are improved, depends 4O0 F~owdered VA/VeoVaMedified Powdered EVA I Modified Powde.red Powdered EVA - - EVA -5 Modified Modified EVA Modified S BR -Modified c _.*, i tO0 O t.J i t IO 1520 I ! I I / I IO 15 20 I I I I '0 15. '43 P o l y m e r - Cement Figure Polymer-CementRatio vs M o d i f i e d Mortars I I I I i IO 1520 Rotio t i t I0 1520 i i i i I 101520 (%) Compressive Strength o f Powdered and Aqueous Polymer- 1204 M.UJK Afridi et a l 6C 5O ~ 30 Powdered VAIVsoVctModified Powdered EVA-I Modified Powdered EVA -2Modified Vol 24, No PoNdered EVA - o - Modified EVA ° Modified SB R Mo dlfied /j;;X to iOI5 ~0 1520 Polymer - IO 20 I0 Cement R~io 0 IO 1520 I0t520 (0/.) Figure 3, Polymer-Cement Ratio vs Tensile Strength of Powdered and Aqueous PolymerModified Mom~"s 50C PdymerCement Ratio (%) 20 40C 30C o _.J 20( x EL iCK | 0.5 Def lection (X lO-Imm) ! 1.0 Figure Flexural Load-Deflection Curves for Powdered VA/VeoVa-Modified Mortars Vol 2,4, No STRENGTH, ELASTIC PROPERTIES, AQUEOUS POLYMERS, MORTARS 1205 on the type of cement modifier used, polymer-cement ratio or both Generally, a rise in polymer-cement ratio also raises the flexural and tensile strengths of all PAAPMMs while, such a consistent relationship between polymer-cement ratio and compressive strength is present only in powdered EVA-2-modified, EVA-modified and SBR-modified mortars The t 40{ PolymerCement Relic / 50, o d (°/:,) z 15 I0 20 20( o " IOC ¢ I I 0.5 I.O Deflection (X lO'tmm) Figure Flexural Load-Deflection Curves for Powdered EVA- 1-Modified Mortars // 500 400 / PolymerCement Ratio (%) 500 IO 2O 15 J 200 It bOO I ! 0.5 I-0 Deflection (X IO-Imm) Figure Flexural Load-Deflection Curves for Powdered EVA-2-Modified Mortars 1206 M.U.K Afridi et al Vol 24, No rest of the powdered polymer-modified mortars show an optimum level of P/C on which compressive strength is maximum The results show that generally the performance of powdered cement modifiers in improving the flexural and compressive strengths of mortars is almost comparable to those of aqueous cement modifiers However, powdered cement modifiers seem less effective than those of aqueous cement modifiers in improving the tensile strength of mortars 500 J f 400 v v 300 PolymerCemenl R~tio O J (%} 200 I0 15 2o u_ I00 0.5 Deflection I.O (X IO-Imm) Figure Flexural Load-Deflection Curves for Powdered EVA-3-Modified Mortars 5O0 PolymerCement 400 Ratio (%) C" 500 0 J "6 200 e h I00 O,5 I 1.0 Deflection (X IO-Imm) Figure Flexural Load-Deflection Curves for EVA-Modified Mortars Vol 24, No STRENGTH, ELASTICPROPERTIES, AQUEOUS POLYMERS, MORTARS 1207 probably because [i] the powdered cement modifiers are less effective in reducing the water-cement ratio of the mix(9), [ii] the powdered cement modifiers form inferior quality polymer films having lesser sand-matrix adhesion level or lesser overall improvement in cement-hydrate-aggregate bond(9) Figures 4-9 show the flexural load deflection curves of various PAAPMMs Figures 10-15 depict the flexural stress - extreme tensile fiber strain curves of various PAAPMMs Figures 16-21 represent the tensile stress - tensile strain curves of various PAAPMMs It is 400 A 'v' I , / Polymer Cement 300 Ratio J / (%) 200 X 20 I0 It 15 IO0 fi ° I 0.5 Deflection (XlO-Imrn) 1.0 Figure Flexural Load-Deflection Curves for SBR-Modified Mortars N E Polymer - Cement 30 R~tio (%) zo I/) 20 t O Lt I0 /11 Ij/ • , I I 200 400 600 Extreme Tensile Fiber Slroin I 800 (XlO -~) | IO00 Figure 10 Flexural Stress-Extreme Tensile Fiber Strain Curves of Powdered VA/Veo-Va-Modified Mortars I 12oo 1208 Vol 24, No M.U.K Afridi et at apparent from the above figures that the addition of both powdered and aqueous cement modifiers to mortars markedly improves their deflection (flexural deformation behaviour), extreme tensile fiber strain and tensile strain Such properties of PAAPMMs are improved because of their modified structure due to the presence of rubbery regions or polymer films which themselves are highly ductile as compared to that of cement hydrate(12) and are capable to arrest the advancing cracks It is significant to note that PAAPMMs are more extensible than the unmodified mortar not at the cost of strength Moreover, PAAPMMs also show improved toughness over the unmodified mortar in conformity to the earlier results(13) o0E P o l y m e r - Cemenf 30 F~tio (°Io) jSz° in G) 2O I= 03 i"7 I0 I 200 400 Extreme 600 I 800 1200 IO~ Tensile Fiber Strain (XIO-6) Figure 11 Flexural Stress-Extreme Tensile Fiber Strain Curves of Powdered EVA- 1-Modified Mortars Polymer- Cement Rotio (%) 50 ZO E o ~j / > ~ ~ - t 20 (/l 03 o I0 It P 20O I 400 Extreme I L_ (300 Tensile Fiber 800 [ _ lOOO I 1200 Strain (x I0- ) Figure 12 Flexural Stress-Extreme Tensile Fiber Strain Curves of Powdered EVA-2-Modified Mortars Vol 24, No STRENGTH, ELASTIC PROPERTIES, AQUEOUS POLYMERS, MORTARS 1209 However, the magnitude to which the deflection, extreme tensile fiber strain and tensile strain of PAAPMMs are improved, depends on the type of cement modifier used, polymer-cement ratio or both Generally, a rise in polymer-cement ratio also raises the deflection, extreme tensile fiber strain and tensile strain of PAAPMMs P o l y m e r - Cement Ratio (%) 30 \o f / _20 ~ 20 :2 I0 ,7 I 200 I t I 400 600 CO0 Extreme _ I00O ! I2o0 Tensile ,Fiber Strain (xlO-~ Figure 13 Flexural Stress-Extreme Tensile Fiber Strain Curves of Powdered EVA-3-Modified Mortars POlymer Cement Ratio (%) \0 3O ~E 20 O0 x I0 h | 2OO 400 600 800 Exlr~me Tensile Fiber Stain (xlO-6) ! 1000 Figure 14 Flexural Stress-Extreme Tensile Fiber Strain Curves of EVA-Modified Mortars ! 1200 1210 M.U.K Afridi ¢t el Vol 24, No It is apparent from the results that powdered cement modifiers are mostly more effective in improving the deflection, extreme tensile fiber strain and tensile strain of mortars in comparison to aqueous cement modifiers This is because the powdered cement modifiers may be more effectively accumulated, along with the bleeding water, at the surfaces of the mortars than the aqueous cement modifiers(14) Conclusions The addition of both powdered and aqueous cement modifiers to mortars increases Polymer Cement Ratio (%) 30 NE ~3 ~0 v ¢/) 20 o~ 10 u_ f 200 ! i I 400 600 Extreme Tensile Fiber I ! 800 I000 Statn (xlO - e ) 1200 Figure 15 Flexural Stress-Extreme Tensile Fiber Swain Curves of SBR-Modified Mortars Polymer- Cement Rol,io (%) 6O E 50 15 5~ ~ 40 j j J J g, 3o ~ "N 20 e- IO J r Ioo Tensile i i I 20 o 300 4O0 Strain (xlO "6 ) Figure 16 Tensile Stress-Tensile Strain Curves of Powdered VA/Veo-VA-Modified Mortars _ _ Vol 24, No STRENGTH,ELASTIC PROPERTIES, AQUEOUS POLYMERS, MORTARS 1211 their flexural, compressive and tensile strengths The gains in flexural and tensile strengths of PAAPMMs are higher and pronounced as compared to those noticed in compressive strength However, the magnitude to which such strengths of PAAPMMs are improved, depends on the type of cement modifier used, polymer cement ratio or both The addition of both powdered and aqueous cement modifiers to mortars markedly improves their deflection, extreme tensile fiber strain and tensile strain However, the magnitude to which such elastic properties of PAAPMMs are improved, depends on the type of cement modifier used, polymer - cement ratio or both 6O f Polymer-Cement Ratio (%) ,¢ 40 I/I 3O - 20 I0 , I00 400 200 300 Tensile 31rain (xlO -6) Figure 17 Tensile Slress-Tensile Strain Curves of Powdered EVA-l-Modified Mortars 6O N f E 50 40 •'- 50 = Polymer- Cement 20 / C //// Ratio (%) \ 2o - IO I, I | 1o0 2O0 3OO Tensile _ _ I 4OO Strain (xlO -6 ) Figure 18 Tensile Stress-Tensile Strain Curves of Powdered EVA-2-Modified Mortars 1212 M.U.K.Afridiet al Yol 24, No The powdered cement modifiers affect the properties of the mortars similarly as those of aqueous cement modifiers Accordingly, it is r e c o m m e n d e d that powdered polymer - modified mortars can be used in the same m a n n e r as those of aqueous polymer - modified mortars for practical applications References 1° Pomeroy, C.D.,Magazine of Concrete Research, V 28, No 96, S e p t e m b e r 1976, pp.121-129 Ohama, Y., AC1 Materials Jounral, V 84, No.6, N o v e m b e r - December 1987, pp 511-518 6O Polymer- Cement E -.~ 5O Ratio (%) 40 3O Â- 20 / I0 I I I00 I _ 200 300 TencJile Stroin ( x l O - ) I 400 Figure 19 Tensile Stress-Tensile Strain Curves of Powdered EVA-3-Modified Mortars Polymer Cement Ratio (%) 60 NE 50 "~ 40 3o -~ 20 Io I I I I I00 200 300 400 Tensile Strain (x I - ) Figure 20 Tensile Stress-Tensile Strain Curves of EVA-Modified Mortars Vol 24, No STRENGTH, ELASTIC PROPERTIES, AQUF~US POLYMERS, MORTARS 1213 Polymer Cement Ratio (%} 6O E 50 L 20 U~ v 4O 30 ¢ 20 IO I I00 Tensile I" 200 I SO0 I 400 Strain (xlO -s) Figure 21 Tensile Stress-Tensile Strain Curves of SBR-Modified Mortars 10 11 12 13 14 Ohama, Y., Proceedings of the 14th Japan Congress on Materials Research, The Society of Materials Science, Koyoto, Japan, 1971, pp 177-179 Wagner, H.B., Chemical Technology, V 3, No.2, February 1973, pp 105-108 Wagner, H.B., I & EC Product Research and Development, V 6, No.4, December 1967, pp 223-231 Brown, J.H., Pomeroy, C.D., Technical Report, CI/SfB/I/Yq 4/-/UDC 666 - 974 017: 678-6-7, 42-507, Cement and Concrete Association, March 1975, pp 1-24 Sun, P.F., Nawy, E.G., and Sauer, J.A., Journal of the American Concrete Institute, V 72, No.ll, 1975, pp 608-613 Wagner, H.B., I&EC Product Research and Development, V 5, No.2, June 1966, pp 149-152 Afridi, M.U.K., Ph.D Thesis, Institute of Chemistry, University of the Punjab, Lahore, Pakistan, 1992, pp 151-191 Ohama, Y., Proceedings of the Second Australian Conference on Engineering Materials, Sydney, July 1981, pp 163-172 Sugata, T., and Ueda, T., Technology Reports of Kansai University, Japan, No.15, 1974, pp 133-141 Bean, D.L., Husbands, T.B., Final Report, Department of Army, U.S Army Corps of Engineers, Washington DC 20314-1000, Under Work Unit 32303, July 1986, pp 1-27 Frondistrou-Yanns, S.A., and Shah, S.P., Supplement to Jounral of the American Concrete Institute, Title No 69-7, 1972, pp 1-17 Yamada, K., Sakata, K., Nakajima, K., Watanabe, N., and Inokawa, H., Review of the Thirty-Fifth General Meeting, Technical Session, The Cement Association of Japan, Tokyo, May 1981, pp 127-129  ... ratio vs flexural strength of powdered and aqueous polymer-modified mortars Figure depicts the polymer-cement ratio vs compressive strength of powdered and aqueous polymer-modified mortars Figure... Polymer-Cement Ratio vs Flexural Strength of Powdered and Aqueous PolymerModified Mortars Vol 24, No STRENGTH, ELASTICPROPERTIES,A Q ~ U S POLYMERS ,MORTARS Test Results 1203 and Discussion Figure shows... Dispersion 1.019 8.5 155 45.8 Vol 24, No STRENGTH, ELASTICPROPERTIES,AQUEOUSPOLYMERS ,MORTARS Testing Preparation 1201 Procedures of Mortars Powdered and aqueous polymer-modified m o r t a r s were