Microsoft Word - 1.doc Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 1 Year 2009 22 TENSILE STRENGTH OF HIGH STRENGTH POLYMER MODIFIED CONCRETE Qusay A. Jabal Al-Kufa University, Engineering College (Civil. Dept) Abstract High strength concrete is widely used especially during the last century. High Strength concrete means concrete with max. Compressive strength ( cf ′ )more than 50 N/mm2 (Shetty, 1988). Polymer modified concrete was) used since 1970s by adding polymer monomers such as styrene Butadiene rubber (SBR) to ordinary concrete during casting as a percentage of weight of cement in order to improve the mechanical properties of concrete. This research includes the study of the effect of styrene Butadiene Rubber on Tensile Strength of Polymer modified concrete PMC, also include the effect of the polymer on compressive strength and relationship between tensile and compressive strength (as a mathematical model). A different types of mixes (1: 1.5: 2, 1:1.5:3 and 1:2:4) were used in this research. Keywords: Polymer modified concrete, Compressive strength, Tensile strength, styrene Butadiene rubber, Cylinder splitting مقاومة الشد للخرسانة المطورة بالبوليمر والعالية المقاومة قصي عبد الحميد جبل العطيه جامعة الكوفة قسم الهندسة المدنيه– آلية الهندسة الخالصة ي إن الخرس دأت ف ي ب شائية والت صناعة اإلن ي ال تخدام ف شائعة االس واد ال ن الم بحت م البوليمرات أص ورة ب انة المط .السبعينات من القرن الماضي في اليابان والواليات المتحدة ثم شاعت االستخدام على مستوى العالم البوليمر أيضا استخدمت بصورة شائعة في القرن الماضي والخرسانة الخرسانة العالية المقاومة مثل الخرسانة المطورة ب ميكا باسكال واستخدم هذا النوع من الخرسانة ) 50(العالية المقاومة تعني الخرسانة التي مقاومة انضغاطها العظمى أآثر من أثناء صب في بداية السبعينات عن طريق إضافة مستحلبات البوليمرات مثل مستحلب الستايرين بيوتادين للخرسانة االعتيادية ,.الخرسانة وإنتاجها آنسبة مئوية من وزن االسمنت لتحسين الخواص الميكانيكية للخرسانة االعتيادية البوليمر ويتضمن هذا البحث تأثير هذا المستحلب على مقاومة ويتضمن أيضا تأثير إضافة نسب الشد للخرسانة المطورة ب النضغاط واستخراج موديالت رياضية لهذه العالقات إضافة إلى استنباط على مقاومة ا ) الستايرين بيوتادين ( مختلفة من الرآام : الرآام الناعم : االسمنت ( موديل رياضي يربط مقاومة االنضغاط بمقاومة الشد وتم استخدام نسب خلط مختلفة من .في هذا البحث) الخشن Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 1 Year 2009 23 Nomenclature ft : Splitting tensile strength (N/mm2) fc : Compressive strength (N/mm2) P : The applied load of machine (N) L : Height of cylinder specimens (mm) Polymer Modified Concrete PMC This type of concrete means a concrete composed of cement latex and aggregates with polymer added as a percentages by weight of cement. This type of concrete can be used for high loaded structural members and also for both pre-cast and prestressed concrete (Vipulanandan, 1990) Tensile strength of " PMC " The study of Tensile strength of concrete is very important . For prestudies , the increase of compressive strength leads to increase tensile strength. There is a different relationships between compressive and tensile strength; some researches, gives the tensile strength as a percentage form the compressive strength ranged between 1/8 to 1/12 (Neville, 1995). This investigation gives a better improvement in tensile strength, and also a better ( cfft ′/ ) ratio .Indirect Tension test is used in this study by splitting of cylinder using the following equation (Eq.1 ) dL p f t π 2 = …(1) The High value of tensile strength may lead to use less tension bars of Reinforcement and make the construction of Building more economic. Aim and Scope of Work The aim of this investigation is to study the effect of (SBR) polymer on Tensile strength PMC and also the optimum P/C(polymer/cement) that gives the Higher values of Both compressive and tensile strength also anew mathematical model is suggested to relationship between: P/C with tensile strength, P/C with compressive strength and tensile strength with compressive strength. Materials Ordinary Portland cement (Type I) was used in this work. Aggregates with specific gravity of 2.79. The max: size Aggregate is 10mm with grading shown in this Table 1 blow . SBR polymer with specifications shows in Table 2 was used in this study. Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 1 Year 2009 24 Concrete Mixing Procedure Aggregates were added to a mechanical mixer with max. capacity of 0.1m3 before adding the cement . After adding the cement, the mixer turned on with adding water according to W/C ratio then the (SBR) polymer should be added to be the homogeneous mix and the mixing should be continued until all particles are fully coated with (polymer- cement paste) matrix. Also, the total mix should have a uniform or homogeneous colour. Ohama (Ohama, 1998) adopted this procedure under title "Modification with liquid polymers", also this mixing procedure was illustrated by Radomir (Radomir, 1998) Program layout The program layout is shown in (1). Curing Using air curing in all polymer mixes, specimens of dimensions (150 × 300mm) were cured in water for six days and 21 days in air with temp ( Average temp. 20oC) This is the best method of curing. Radomir (Radomir, 1998) illustrate the best method for curing for polymer modified concrete see Figure (2) Specimens Using (3) specimens for each mix, the specimens of dimensions of (150×300 mm) where used for both compressive and indirect tension tests, capping were used only for compression tests . The max. Size Aggregates for all mixes was 10mm. (W/C) ratio used in this study were: 0.30 for polymer mixes and 0.35 for reference mixes because of the action of polymers that's tend to reduce the W/C ratio for concrete and improve the Mechanical properties (Bentur, 1982) Specimens Tests a.Compressive strength tests Using rate of loading according to ASTM (39/C 39M-2001), (ASTM, 2001) standard specifications for determination of static Modulus of elasticity and poisons ratio of concrete in compression. This test was done using ELE compression testing machine with max capacity (2000 kN). Capping is done in this work for all cylinder specimens (for compression test ) in order to obtain uniformly distributed load under applied load, and also to obtain accurate readings, the capping was made by means of cement paste and by glass plate of about 7mm in thickness and of a length about (diameter of cylinder +30 mm) (Shetty, 1988). The capping was done after (4hrs) of casting so that the concrete in cylinder mould undergoes plastic shrinkage and subsides fully. Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 1 Year 2009 25 b. Indirect Tensile Strength " Cylinder splitting " A three specimens for each mix were used and also the same rate of loading and same ELE testing machine is used. c. Development of tensile and compressive strength, and Mathematical models. Table 3, shows the effect of the increase in P/C ratio on compressive strength, P/C of 15% Gives the higher value of compressive strength (or optimum value ) for all mixes. (1:1.5:2) (cement :Fine Agg.: Coarse Agg ) mixes gives the Maximum Compressive strength of about (83.3) MPa. Table (4), shows the effect of the increase in P/C on tensile strength, 15% P/C is the optimum P/C that gives the maximum tensile strength for all mixes; Both tensile and compressive strength are improved by adding polymer, this improvement due to double influence of polymer caused by the polymer films formation of SBR polymer and a co- matrix phase is formed by both cement hydration and polymer film formation processes (Ohama, 1997). Also, another factors that causes improvement in the properties for this type of concrete; the first is that the voids in this type of concrete is fill up by polymers, and some polymer particles bond with cement hydrates and silicate surfaces of Aggregates. Also, Some chemical reactions may take place between the particles surfaces of polymers and calcium ions (Ca+2), Ca(OH)2 solid surfaces, or silicate surfaces of aggregates (Sujjavnith, 1998). Figure (3), shows the effect of the increase in P/C up to 25% of weight of cement on the compressive strength for different mixes. The mathematical model shown in equations 2,3 and equation 4. Fc =-0.1757 *(P/C)2 +5.297 * (P/C) +39.29 …(2) R2 = 0.88 [ For mix. Proportion =1:1.5:2] Fc =-0.135 *(P/C)2 +4.945 * (P/C) +28.92 …(3) R2 = 0.98 [ For mix. Proportion =1:1.5:3] Fc =-0.093 *(P/C)2 +3.316 * (P/C) +27.54 …(4) R2 = 0.96 [ For mix. Proportion =1:2:4] Where : R2 Correlation Coefficient Figure (3), it can be seen that optimum P/C ratio is found as 15% , this optimum P/C Was also found 15% for maximum tensile strength. Figure (4), shows the effect of P/C on Tensile strength of (PMC), the mathematical model also given in equation (5), (6) and equation (7) as follows: Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 1 Year 2009 26 Ft =-0.0277 (P/C)2 +0.989 (P/C) +4.79 …(5) R2 = 0.96 [ For 1:1.5:2 mixes] Ft =-0.0126 (P/C)2 +0.62 (P/C) +3.246 …(6) R2 = 0.98 [ For 1:1.5:3 mixes] Ft =-0.0133 (P/C)2 +0.607 (P/C) +2.739 …(7) R2 = 0.96 [ For 1:2:4 mixes] A straight line related the data in Figure 5 with equation illustrated as Equation (8). This equation is a perfect equation shows that the increase in compressive strength due to the increase of (P/C); leads to increase in tensile strength, In this research the increase in tensile strength is more than (1/8) of fc' [as in the previous investigations]. Now we can see from Table (3), if cF ′ =83.3 gives indirect tensile strength cF ′ =13.9, the ft/fc' ratio equals to 1/6, and also for some other mixes the ratio becomes more than 1/6 , this due to the action of (SBR), while the ratio of ft/fc for ordinary concrete of the same mixes without (P/C) gives (ft/fc') ratio of about (4.4/36.1)=(1/8.2). Figure (5) shows a relationship between tensile and compressive strength of (PMC). Fc= 4.538(Ft)+18.004 ….(8) Conclusions 1- Concrete specimens with different mix proportions developed with adding polymers. P/C of (15%) gives maximum values of both tensile and compressive strength. 2- The proposed model for polymer modified concrete (PMC) has a general form for all mixes. The constants change from mix to fit the shape of (P/C- compressive and tensile ) relations; and it is found from the second degree. 3- The proposed model for compressive – tensile strengths is found as a straight line (first degree) Equation and if we derive the equation then we can find 54.4== ft fc dx dy in general 4- The improved mixes in this study did not submit to previous relations that gives the value of tension as a percentage from compressive strength. (ft/fc) [As we seen in paragraph(3)]. In this research the value (ft/fc) is found as (1/4.54), this ratio is bigger than the previous ratio (1/8 – 1/10) that indicate the (ft/fc) for ordinary concrete in previous studies. This perfect improvement in Tensile strength make this type of (PMC) more useful and more economic for structural design and may lead to use less tension steel bars and make the construction more economic. Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 1 Year 2009 27 References: 1- shetty, M.," Concrete Technology, Theory and practice" S.Chand and Company, India , 3rd Ed., 1988. 2- Vipulanandan ,C. and Paul, W., "Mechanical properties of Epoxy and polyester polymers and polymer concrete Systems, "ACI Mat.J., May-June 1990: 241-251. 3- Neville, A., "Properties of concrete", 4th and Final Ed., London , 1995. 4- Ohama, Y., "Polymer- Based Admixture", Cem. And Conc. Comp., 1998,20:189-212. 5- Radomir , J. and Vlastimir, S."Experimental Research on Polymer Modified Concrete ", ACI Mat.J., July-Aug., 1998,:463-469. 6- Bentur, A., " Properties of polymer latex – cement composites " The International .J . of cement composites and lightweight concrete , Vol.4, No.1, 1982: 57-65. 7- ASTM,C39/ C39M_ 01 Standard Test Method For Compressive Strength Of Cylindrical Concrete. 8- Ohama, Y., " Recent progress in concrete polymer composites" advn cem Bas Mat, New York, 1997: 31-40. 9- Sujjavnith, S.and Lundy,J.," Development of strength and fracture properties of styrene – Butadiene Copolymer Latex – Modified concrete ", ACI Journal, title no.95-M13.1998:131-143. Table 1: Grading of Coarse and fine aggregates I.S Sieve Designation Percentage passing by weight (%) Indian Standard (I.S) for grading(Zone III) 10mm 100 100 4.75mm 90 90-100 2.36mm 88 85-100 1.18mm 83 75-100 600micron 74 60-79 300micron 18 12-40 150 micron 2 0-10 Table 2: Chemical composition of SBR Infra-Red(I.R.)test PH% Humidity content Solid Particles content % Styrene Butadiene rubber with small percentage of admixtures 8.2 42.4 57.42 Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 1 Year 2009 28 Table (3): The effect of (P/C) on compressive strength of (PMC). P/C Mix proportion P/C 0% P/C 5% P/C 10% P/C 15% P/C 20% P/C 25% 1:1.5:2 36.1* 67.8* 71.1* 83.3* 67.7* 65.3* 1:1.5:3 30.1* 48.3* 63.7* 76.1* 72.3* 68.0* 1:2:4 28.9* 40.2* 48.8* 60.3* 56.4* 51.7* * Compressive strength in N/mm2(MPa) Table (4): The effect of (P/C) on tensile strength of (PMC). Splitting Tensile Strength (MPa) P/C Mix proportion P/C 0% P/C 5% P/C 10% P/C 15% P/C 20% P/C 25% 1:1.5:2 4.4 9.9 11.3 13.9 12.7 12.5 1:1.5:3 3.5 5.8 7.6 10.3 10.8 10.6 1:2:4 3.0 5.2 6.8 9.7 9.5 9.4 Tests Compressive strength Indirect tension test Test for cylinders for cylinders Figure (1) Experimental program of this work Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 1 Year 2009 29 Figure (3) The effect of the increase in (P/C) on compressive strength of (PMC) Figure (4) The effect of the increase in (P/C) on tensile strength of (PMC) Figure (2) Effect of curing conditions on compressive strength for modified polymer concrete (5) Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. 1 Year 2009 30 Figure (5) Shows a mathematical model for the relationship between tensile strength and compressive strength for different mixes of PMC.