Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 3 Year 2009 ��� EFFECT OF FREEZING AND THAWING ON STRESS-STRAIN RELATIONSHIPS OF POLYMER MODIFIED CONCRETE (PMC) Abstract The investigation includes the effect of freezing and thawing cycles on stress-strain relationships of polymer modified concrete (PMC). Cycles of freezing and thawing contains 12 hours at 100°C and 12 hours at -4°C. The process of cycles of freezing and thawing Simple experimental technique is used to obtain the complete stress-strain curves up to strain of 0.006 (Both ascending and descending portions) sample subjected to freezing and thawing cycles (FTC), then subjected also to stress-strain tests. Keyword : Polymer modified concrete, Compressive strength, Modulus of elasticity, Styrene Butadiene Rubber, Foil gages. ������� � �� � ��– ������ ���� ��� ������� –������� �������� � � ��� ���! "�� �##$�"�� ������ � � � � �������� ���� �� ����� ����� ����� � ��� – ��������� ������� �!�" � #�$% ��. ��'�� �� ����� �� ��(�� ��������)* ��� ��! ���� �)),, ( � ��.� ���)* ����' ���� ��! )/0 ( '��.� '��� . ����� ���� ���!� �������� ���� ��)1, ( 23� � � #�4 � � �� #���� 5��"�!� 5� 67��� �� 8���� 5�� ��'���� – #�'$% �� ��(��)#9� ��� ���4�� :9��� .( 5� �������� ���� �� ������ �$�";< 7��� �� = >������ –#�$% �� . Nomenclature ft : Splitting tensile strength (N/mm 2 ) fc : Compressive strength (N/mm 2 ) P : The applied load of machine (N) L : Height of cylinder specimens (mm) Es : Modulus of elasticity of steel (N/mm 2 ) Dr. Ameer Gh. Taleb Al-Kufa University Civil Eng. Dept. Mohammed H. Salih Al-Kufa University Civil Eng. Dept. �.6��� 6��@ A"< �B:*� ��"�1–����3 ���4 ����$ ����3 (&C � 1 ��DE � % �FC �B:*� ��"�1–����3 ���4 ����$ ����3 (&C G�� +�:H �DI �B:*� ��"�1–����3 ���4 ����$ ����3 (&C Qusay Abdulhameed Jabal Al-Kufa University Civil Eng. Dept. Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 3 Year 2009 ��� fs : Stress in steel tube (N/mm 2 ) Pconc : The load on concrete specimens (N) Ac : Cross sectional area of concrete cylinder (mm 2 ) Ptotal : Total load by machine (N) εs : Average strain in steel tube (mm/mm) σc : Stress in concrete specimens (N/mm2) PS : The load on steel tube (N) Specimens and Materials Specimens were (7.5 × 15 cm)cylinders, 36 specimen were made to obtain total stress-strain curves, a different mix proportions of cement: Fine Aggregates: Coarse Aggregates of (1:1.5:2) (1:1.5:3) and (1:1.5:4) using styrene Butadiene Rubber (SBR) as a percentage of cement weight of 15% to improve the properties of ordinary concrete and makes the concrete with high strength values. The maximum size aggregate is (10 mm) of 2.8 specific gravity sieve analysis is shown in (Table 1) Ordinary portland cement was used in all mixes ordinary drinking water was used in all mixes. Curing : Ordinary mixes were cured in water, but polymer mixes cured 6 days in water and 22 days in air. This gives the perfect curing according to Radomir investigation (Radomir, 1998) Experimental Program Testing Method A simple Technique was developed by ASTM C-469 (ASTM, C-469, 1981) to obtain the stress-strain curve of concrete ( both ascending and descending portions ) up to the strain of 0.006 (Figure 1) (Wang, 1978) Concrete cylinders were loaded in parallel with a steel tube. The high strength steel tube was case hardened so that it's stress-strain curve was linearly elastic up to the strain of 0.006. The specimens were capped in the testing machine to ensure that the load will be shared simultaneously by both the tube and concrete cylinder immediately on loading. The strains in the steel tube were measured with two foil-type resistance strain gauges . These strains gave not only the amount of load taken by the steel tube, but were also used to obtain nominal strains in concrete. Thus knowing the total load and steel strain, the stress – strain relationship of each curve were made by three tested specimens and taking average of three readings of stress. Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 3 Year 2009 ��� Calculations Simple calculations to obtain the stress-strain curve are given below The strain in steel tube multiply by the modulus of elasticity of steel (Es) gives the stress in steel tube: Єs * Es = fs ...(1) where Єs : The strain (AVG. Strain in steel by two foil gages) Es : The modulus of elasticity of steel 207000 MPa fs : The stress in steel tube 1. The load on concrete Pconc =Ptotal -Ps ...(2) where Pconc : The load on concrete specimen Ptotal : Total load by machine Ps : The load on steel tube Ps =fs x As ...(3) As : area loaded (steel tube) 2. The stress in concrete (σc) is calculated from Eq.4 below c conc c A P =σ ...(4) where σc : The stress in concrete Ac : Area ( loaded) by concrete Ac = 2 )75( 4 π (in mm 2 ) Thus, executing the calculations above gives the total stress – strain relationship of concrete. Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 3 Year 2009 ��� Analysis of results Figures (2-7) show the effect of cycles of freezing and thawing on stress – strain relationships for different mixes of concrete with or without polymers , the mixes with 15% p/c shows the higher values of maximum compressive strength with respect to the reference mix after FTC (Ohama, 2003) Figure (2) shows the effect of FTC on stress-strain relationship of concrete mix (1:2:4) with 0% p/c ( reference mix) . The reduction in max. Compressive strength of the reference mix due to FTC is about (66%), but with using SBR polymer, the reduction is very little see (Figure 3 ) and its about (2.2%) . Table 3 Shows the reduction in the value of the chord modulus of elasticity for the mixes. The reduction after FTC cycles is about 68% for (1:2:4) mix, but after using SBR polymer , the reduction is very less and about (9.8%). Figure 4 also shows the effect of FTC on stress-strain relationship of concrete with mix proportions of (1:1.5:3) without adding polymers , the reduction in compressive strength is about (47%), but after using polymers, the reduction after FTC is about (1.2%), (see fig. 5 ). The reduction in modulus of elasticity for the reference mix with mix prop. of (1:1.5:3), is about 57.7 , but the reduction in mixes with p/c=15% is about 0.4% and this is perfect, see (Table 3). Figure 6 shows the effect of FTC on (1:1.5:2) mixes (p/c=0%) , the reduction in compressive strength is about (48.2 %). With using 15% p/c , the reduction is a bout (4.2%) see (Figure 7). The reduction in modulus of elasticity for (1:1.5:2) reference mix is about ( 57.7 ), while in 15% p/c mix , is about (3.8%) see (Table 3 ) Discussion The improvement in properties of concrete with adding styrene butadiene rubber seen in previous Figures (2-7), is very excellent, because of the action of styrene butadiene rubber (Watanable, 2005) Polymer latex modification of concrete is governed by both cement hydration and polymer film formation processes (wang, 1978), some chemical reactions may take place between the surface of polymer particles and calcium ions ( Ca +2 ) , Ca(OH)2 solid surfaces , or silicate surfaces over the aggregates (Kaempfer, 2006, Ye, 2005) Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 3 Year 2009 ��� Moreover, there are other reasons that cause this improvement in the properties of these mixes ; the first is that the voids in the reference mixes are filled up by polymer particles when using the polymer with 15% , (p/c=15%) , also , it appears that the microcracks in latex - modified mortar and concrete under stress are bridged by the polymer films or membranes formed , which can prevent cracks propagation , and that a simultaneously strong cement hydrate- aggregate bond is developed (Ohama, 1998) Therefore, these reasons cause the prefect reduction in compressive strength and modulus of elasticity after FTC Conclusion 1. The action of FTC on concrete with different mix proportions without using polymer is very high with respect to polymer modified concrete (PMC) . 2. (PMC) with 15% p/c gives perfect results in both compressive strength and static modulus of elasticity . 3. PMC gives a perfect durability against cycles of freezing and thawing, because of the action of polymer – film formation and less voids inside the concrete. References 1- Radomir, J. and Vlastimir, S., " Experimental Research on Polymer Modified Concrete ". ACI Materials Journal, July-August 1998:463-469. 2- ASTM Committee, C-469 " Standard Test Method for Static Modulus of Elasticity and Poisson's Ratio of Concrete in Compression". 1981. 3- Wang, P.T., Shah, S.P., and Naaman, " Stress-Strain Curves of Normal and Lightweight Concretes in Compression". Journal of the American Concrete Institute, NO. 75-62, 1978: 603-611> 4- Ohama, Y., " Study on Properties and Mix Proportioning of Polymer-Modified Mortars for Buildings". Report of the Building Research Institute, NO. 65 (2003) 100-104. 5- Watanabe, T., and Kawano, T., " Study on SBR Latex Composite Material ". MRS International Meeting on Advanced Materials, Vol. 13 Advanced Cement and Chemically Bonded Materials. MRS, Pittsburgh, 2005, pp 6- Kaempfer ,W., Durability of Polymer-Modified Mortar and Concrete. Journal of Structural and Construction Engineering (In Japanese), Architectural Institute of Japan , 664 (2006)2- 6. 7- Ye, Z. , Research on the structure of reactive Polymer Cement Materials .Technological Institute of the Royal Flemish Society of Engineers, Antwerp , 2005,P.P.457-462. 8- Ohama, Y., "Polymer- based admixture", cement and concrete compositions, 1998, 20:189- 212. Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 3 Year 2009 �� Table 1: Sieve Analysis of Aggregates I.S. Sieve Designation % Passing by weight Indian standard (I.S.) for grading zone II 10 mm 100 100 4.75 mm 93 90-100 2.36 mm 85 85-100 1.18 mm 77 75-100 600 micron 62 60-79 300 micron 20 12-40 150 micron 1.0 0-10 Table 2: Chemical Composition of Styrene Butadiene Rubber (SBR) Infra-Red (I.R) Test PH Humidity Content Solid Particle content % Styrene Butadiene Rubber with small percentage of admixtures 8.2 42.4 57.42 Table 3: The Reduction in Elastic Modulus of Elasticity Due to FTC Reduction in Elastic Modulus Due to FTC% Chord Modulus of Elasticity After FTC (GPa) Chord Modulus of Elasticity Before FTC(GPa) % P/C W/C Mix. Proportion 9.8 42.4 47.0 15 0.35 1:2:4 68 7.8 24.4 0 0.4 1:2:4 0.4 67.5 67.8 15 0.35 1:1.5:3 57 12.6 29.3 0 0.4 1:1.5:3 3.8 68.6 71.3 15 0.35 1:1.5:2 57.7 15.7 37.1 0 0.4 1:1.5:2 Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 3 Year 2009 �� Figure (2) The effect of FTC on stress-strain behaviour for ordinary concrete (without polymers) with (1:2:4) mix proportion Mix. Proportion 0% P/C Ref. Mix. W/C=0.4 0 5 10 15 20 25 30 35 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 Axial strain x10 (mm/mm) C o m p re s s iv e s tr e s s ( M P a ) before FTC (Fc=31.8 Mpa) afte re FTC (Fc=10.9 Mpa) Mix. Proportion 1:2:4 P/C=0% Ref. Mix. W/C=0.4 Figure1- Test Set up High Strength Steel Tube 2 Foil Strain gauges Machine Head Machine base Capping 15 Cm Concrete Specimen Φ=9.3 cm 7.5 cm Steel plate MPa ) MPa ) Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 3 Year 2009 ��� Figure (3) The effect of FTC on stress-strain behaviour for PMC with mix proportion of (1:2:4). Figure (4) The effect of FTC on stress-strain behaviour for (1:1.5:3) mixes Without polymers Mix Proportion 1:2:4 P/C=15% W/C=0.35 0 10 20 30 40 50 60 70 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 Axial strain (mm/mm) C o m p re s s iv e s tr e s s ( M P a ) before FTC (Fc=60.1 MPa) after FTC (Fc=58.8 MPa) Mix Proportion 1:1.5:3 P/C 0% W/C=0.4 0 5 10 15 20 25 30 35 40 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 Axial strain (mm/mm) C o m p re s s iv e s tr e s s ( M P a ) before FTC (Fc=37.9 Mpa) afte r FTC (Fc=20.1 Mpa) MPa) MPa) MPa) MPa) Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 3 Year 2009 ��� Figure (5) The effect of FTC on stress-strain behaviour for PMC of (1:1.5:3) mixes. Figure (6) the effect of FTC on stress-strain behaviour for (1:1.5:2) mixes Without polymers Mix Proportion 1:1.5:3 P/C=15% W/C=0.35 0 10 20 30 40 50 60 70 80 90 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 Axial strain (mm/mm) C o m p re s s iv e s tr e s s ( M P a ) be fore FTC (Fc=80.8 Mpa) after FTC (Fc=80.8 Mpa)79.8 Mix Proportion 1:1.5:2 P/C=0% W/C=0.4 0 5 10 15 20 25 30 35 40 45 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 Axial strain (mm/mm) C o m p re s s iv e s tr e s s ( M P a ) be fore FTC (Fc=41.1 Mpa) afte r FTC (Fc=21.3 Mpa) MPa) MPa) MPa) MPa) Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 3 Year 2009 ��� Figure (7) The effect of FTC on stress-strain behaviour for PMC of (1:1.5:2) mixes. Mix Proportion 1:1.5:2 P/C=15% W/C=0.35 0 10 20 30 40 50 60 70 80 90 100 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 Axial strain (mm/mm) C o m p re s s iv e s tr e s s ( M P a ) be fore FTC (Fc=85.9 Mpa) after FTC (Fc=82.3 Mpa)MPa) MPa)