EFFECT OF SUPERPLASTICIZERS ON WORKABILITY AND STRENGTH OF CONCRETE Saeed Ahmad*, University of Engineering & Technology,Taxila, Pakistan Muhammad Nawaz, University of Engineering & Technology, Taxila, Pakistan Ayub Elahi, University of Engineering &Technology, Taxila, Pakistan 30th Conference on OUR WORLD IN CONCRETE & STRUCTURES: 23-24 August 2005, Singapore Article Online Id: 100030014 The online version of this article can be found at: http://cipremier.com/100030014 This article is brought to you with the support of Singapore Concrete Institute www.scinst.org.sg All Rights reserved for CI Premier PTE LTD You are not Allowed to re distribute or re sale the article in any format without written approval of CI Premier PTE LTD Visit Our Website for more information www.cipremier.com
30 th Conference on OUR WORLD IN CONCRETE & STRUCTURES: 23 24 August 2005, Singapore EFFECT OF SUPERPLASTICIZERS ON WORKABILITY AND STRENGTH OF CONCRETE Saeed Ahmad*, University of Engineering & Technology,Taxila, Pakistan Muhammad Nawaz, University of Engineering & Technology, Taxila, Pakistan Ayub Elahi, University of Engineering &Technology, Taxila, Pakistan Abstract It has long been a concrete technologist s dream to discover method of making concrete at the lowest possible water/cement ratio while maintaining a high workability. To a considerable extent this dream has been fulfilled with the advent of superplasticizers. Have indeed added a new dimension to the application of admixtures with regards to production of high strength and flowing concretes. It is now possible to produce concrete with compressive strength of the order of 13000 psi (90 Mpa). In addition, these are also suitable for use with other cementations materials like fly ash and blast furnace slag. In the wake of energy conservation policy and diminishing supplies of high quality raw materials, there is a need to use marginal quality cements and aggregates for the production of concrete. In such instances the use of superplasticizers permits the production of concrete at low water/ cement ratios. Thus many waste materials of today become the useful by products of tomorrow. It is the particular role of superplasticizers, which is very importance for us here in Pakistan, because of our poor economy and less developed industrial base. Besides, the addition of superplasticizers to produces concrete with less cement but normal strength and workability is another application, which has received more attention. In this research programme two types of superplasticizers(rheobuild 1100,Rheobuild561M) of synthetic polymer base confirming to ASTM C-494 type A&F and ASTM type B,D&G respectively has been used. Three nominal ratios of 1:1:2, 1:1.5:3 and 1:2:4 were used for mix proportioning of concrete constituents by weight. The water cement ratio was maintained as 0.50, 0.55 and 0.60 to study the effect of these SP on various properties of concrete. The dosage of superplasticizers was adopted as constant @ 0.80% by the weight of cement. To study the effects of superplasticizers the experiments have been divided into three series namely workability series, water reduction series and cement saving series. The result have shown substantial improvement in the properties of concrete after use of the superplsasticizers.the Rheobuild 561M high range water reducer,superplasticizer has given more promising results as compared to Rheobuild1100. Key words: Superplasticizers, reinforcement, pre-cast, slab, beam, slender, mixproportioning, compreseve strength, tensile strength, modulus of rupture.
1. Introduction The earliest known published reference to the use of small amounts of organic material to increase the fluidity of cement containing composition was made in 1932 [1] where polymerized naphthalene formaldehyde sulphonate salts were claimed as useful in this role. This was followed during the mids 1930s to early 1940s by numerous disclosures regarding the use of lignosulphonate and improved composition [1].In recent years, construction agencies in North America, Great Britain and other countries have evinced great intrest in the use of superplasticizers, superfluidifiers, siper waterreducers or high range water reducers [3]. The superplastisizers (SP) are refered to as high range water reducing admixture by ASTM- C494,which mainly disperses the water in concrete matrix. This property is some time called as dispersion-fluidification property of concrete admixture. The superplasticizers are classified in the following four major groups; Sulphonated Nephthalene Formaldehyde Condense(SNF). Sulphonated Melamine Formaldehyde Condense (SMF). Modified Lignosulphonates (MLS). Others. Today superplasticizers are used in all important projects across the world in high raise buildings, prestressed concrete, slender components with congested and densely packed reinforcement, beams and slabs pre-cast elements and long slender columns. The superplasticizer affect the various properties of concrete both in fresh and hardened forms mainly due to the following facts as commented by M.Collperdi [1] in Concrete Admixtures Hand Book; Reduction in interfacial tension. Multilayered adsorption of Organic molecule. Release of water trapped amongst the cement particles. Retarding effect of cement hydration. Change in morphology of hydrated cement. The workability of concrete is mainly governed by the max size, shape, texture and grading of the aggretes. For a given value of water cement ratio, there is one value of coarse/fine ratio for given material that gives the highest workability [2].Parenchio [3] developed a miniature slump test for the cement paste which requires small amount of paste and less testing time. The high workability of SP concrete is however lost in the early 30minutes due to formation of hydrates [4]. The compressive strengths of SP concrete are usually higher than the corresponding strengths of the reference mixes. When SP is used, a water reducer up to 32-33% can be achieved [5].This fact leads to the increase in the compressive strength of SP concrete. Most recently new generations of SP have been developed to give ultra high strength concrete producing concrete with compressive strength of 15000 psi and more [6] and very high early strength at 2 to 4 hours. In water reduced SP concrete no undue segregation and bleeding of concrete occurs due to decrease in water cement ratio. if there are sufficient fine aggregates in the concrete, the segregation in high workability sp concrete can also be controlled [7] There are three possible ways in which superplasticized concrete can be produced [19] High workability concrete, Concrete with low water/ cement ratio,concrete with reduced cement content. 2. Experimental Details 2.1 Material: Cement: Ordinary Portland Type-1 cement was used.
Fine Aggregates: Fine aggregates confirming to the gradation of ASTM-136 were used. Coarse Aggregates: Lime stone crushed stones of size1/2 in and below were used. Series No 1 To investigate the effect of SP on workability slump tests were carried out and to check the effect on compressive strength cubes [6*6*6] were tested at the ages of 3,7,28 days. The results are shown in Table1 to 3. For Tensile strength of SP added concrete cylinders (6*12 ) was tested by splitting tests at the age of 28days,the results are shown in Table 4. To check the modulus rupture of SP added concrete, the standard plain concrete beams were tested at third point load after 28days of pouring. The results are shown in Table 5. Series No 2 To check the effect of water reduction on SP added concrete the water content was gradually increased, at constant workability, keeping all other ingredients of the mix costant,.increasing the dosages of the SP to compensate for the lost in workability. Workability was kept constant by the method of successive trials; the results are shown in the Table 6&7. Series No 3 In this test workability was kept constant both; cement content and water content were reduced keeping water/cement ratio and workability as constant. The results are shown in the Table 6&9.
Table 1 TEST RESULTS SHOWING EFFECT OF SUPERPLASTICIZERS ON COMPRESSIVE STREGNTH AND WORK ABILITY AT CONSTANT W/C RATIO (SERIES- 1) MIX RATIO (1:2:4) Superplasticizer Used W/C Slump Compressive Strength (Psi) Ratio 3 Days 7 Days 28 Days Nil 0.55 8 2685 2940 4270 Rheobuild- 0.55 12 2705 3005 4290 1100@0.80% Rheobuild-561 M@0.80% 0.55 15 2715 3035 4345 EFFECT OF S.P ON COMPRESSIVE STRENGTH AT CONSTANT W/C RATIO 5000 4500 Compressive Strength i(p i) 4000 3500 3000 Ages of testing 2500 3 Days 7 Days 28 Days Nil 2685 2940 4270 Rheobuild-1100 2705 3005 4290 Rheobuild-561 M 2715 3035 4345 EFFECT OF SUPPER PLASTICIZER ON COMPRESSIVE WORKABILITY AT CONSTANT W/C RATIO Slump 30 25 20 15 10 5 0 Superplasticizer Nil Rheobuild-1100 Rheobuild-561M
Table 2 TEST RESULTS SHOWING EFFECT OF SUPERPLASTICIZERS ON COMPRESSIVE STREGNTH AND WORK ABILITY AT CONSTANT W/C RATIO (SERIES-1) MIX RATIO (1:1:5:3) Superplasticizer Used W/C Slump Compressive Strength (Psi) Ratio 3 Days 7 Days 28 Days Nil 0.55 15 2935 4135 6070 Rheobuild- 0.55 30 2980 4240 6125 1100@0.80% Rheobuild-561 M@0.80% 0.55 45 3035 4380 6230 EFFECT OF S.P ON COMPRESSIVE STRENGTH AT CONSTANT W/C RATIO Compressive Strength i(p i) 7000 6000 5000 4000 3000 2000 Ages of testing 3 Days 7 Days 28 Days Nil 2935 4135 6070 Rheobuild-1100 2980 4240 6125 Rheobuild-561 M 3035 4380 6230 EFFECT OF SUPPER PLASTICIZER ON COMPRESSIVE WORKABILITY AT CONSTANT W/C RATIO Slump 60 50 40 30 20 10 0 Superplasticizer Nil Rheobuild-1100 Rheobuild-561M
Table 3 EFFECT OF SUPERPLASTICIZERS ON COMPRESSIVE STREGNTH AND WORK ABILITY AT CONSTANT W/C RATIO (SERIES-1) MIX RATIO (1:1:2) Superplasticizer Used Slump Compressive Strength (Psi) W/C Ratio 3 Days 7 Days 28 Days Nil 0.55 35 4280 5515 6135 Rheobuild-1100@0.80% 0.55 75 4345 5530 6205 Rheobuild-561 M@0.80% 0.55 115 4395 5540 6315 EFFECTS OF S.P ON COMPRESSIVE STRENGTH AT CONSTANT W/C RATIO 6500 6000 Compressive Strength psi (Psi) 5500 5000 4500 4000 Ages of testing 3 Days 7 Days 28 Days Nil 4280 5515 6135 Rheobuild-1100 4345 5530 6205 Rheobuild-561 M 4395 5540 6315 EFFECT OF SUPPER PLASTICIZER ON COMPRESSIVE WORKABILITY AT CONSTANT W/C RATIO Slump 120 100 80 60 40 20 0 Superplasticizer Nil Rheobuild-1100 Rheobuild-561M
Table 4 TEST RESULTS SHOWING EFFECT OF SUPERPLASTICIZERS ON SPLITTING TENSILE STREGNTH OF CONCRETE AT CONSTANT W/C RATIO (SERIES-1) MIX RATIO (1:2:4) Superplasticizer Used W/C Ratio Slump 28 Days Splitting Tensile Strength (Psi) Nil 0.55 8 405 Rheobuild-1100@0.80% 0.55 13 415 Rheobuild-561 M@0.80% 0.55 15 430 MIX RATIO (1:1:5:3) Superplasticizer Used W/C Ratio Slump 28 Days Splitting Tensile Strength (Psi) Nil 0.55 15 460 Rheobuild-1100@0.80% 0.55 30 485 Rheobuild-561 M@0.80% 0.55 45 500 (SERIES-1) MIX RATIO (1:1:2) Superplasticizer Used W/C Ratio Slump 28 Days Splitting Tensile Strength (Psi) Nil 0.55 35 560 Rheobuild-1100@0.80% 0.55 75 575 Rheobuild-561 M@0.80% 0.55 115 585
Table 5 TEST RESUTS SHOWING EFFECT OF SUPERPLASTICIZERS ON MODULUS OF RUPTURE (FLEXURAL STRENGTH) OF CONCRETE AT CONSTANT W/C RATIO (SERIES-1) MIX RATIO (1:2:4) Superplasticizer Used W/C Ratio Slump 28 Days Tensile Strength (Psi) Nil 0.55 9 655 Rheobuild-1100@0.80% 0.55 12 680 Rheobuild-561 M@0.80% 0.55 16 710 MIX RATIO (1:1.5:3) Superplasticizer Used W/C Ratio Slump 28 Days Tensile Strength (Psi) Nil 0.55 15 810 Rheobuild-1100@0.80% 0.55 30 845 Rheobuild-561 M@0.80% 0.55 45 875 MIX RATIO (1:1:2) W/C Ratio Slump 28 Days Tensile Superplasticizer Used Strength (Psi) Nil 0.55 35 965 Rheobuild-1100@0.80% 0.55 75 980 Rheobuild-561 M@0.80% 0.55 118 1005
Table 6 TEST RESULTS SHOWING EFFECT OF SUPERPLASTICIZER ON WATER REDUCTION AND COMPRESSIVE STREGNTH AT CONSTANT WORK ABILITY (SERIES-2) MIX RATIO (1:1.5:3) Superplasticizer Used Rheobuild 1100 W/C Ratio (%)Water Reduction Slump Compressive Strength (Psi) 3 Days 7 Days 28 Days 0.0% 0.60-18 2735 3925 5870 0.40% 0.58 3.33% 20 2815 3995 5935 0.50% 0.57 5% 19 2870 4060 5995 0.60% 0.56 6.66% 16 2910 4130 6070 0.70% 0.54 10% 18 2965 4215 6095 0.80% 0.53 11.66% 19 3025 4285 6140 EFFECTS OF SUPERPLASTICIZER ON COMPRESSIVE STRENGTH AT CONSTANT WORKABILITY 6500 Compressive Strength i(p i) 6000 5500 5000 4500 4000 3500 3000 2500 Ages of testing 3 Days 7 Days 28 Days Nil 2735 3925 5870 Rheobuild-1100 3025 4285 6140
Table 7 TEST RESULTS SHOWING EFFECT OF SUPERPLASTICIZERS ON WATER REDUCTION AND COMPRESSIVE STREGNTH AT CONSTANT WORK ABILITY (SERIES-2) MIX RATIO (1:1.5:3) Superplasticizer Used Rheobuild 561 M W/C Ratio (%)Water Reduction Slump Compressive Strength (Psi) 3 Days 7 Days 28 Days 0.0% 0.60-18 2738 3925 5875 0.40% 0.57 5% 19 2825 4010 5945 0.50% 0.56 6.66% 20 2885 4085 6005 0.60% 0.54 10% 17 2920 4135 6085 0.70% 0.53 11.66% 18 2970 4225 6195 0.80% 0.52 13.33% 19 3055 4390 6255 EFFECTS OF SUPERPLASTICIZER ON COMPRESSIVE STRENGTH AT CONSTANT WORKABILITY Compressive Strength i (P i) 6500 6000 5500 5000 4500 4000 3500 3000 2500 Ages of testing 3 Days 7 Days 28 Days Nil 2738 3925 5875 Rheobuild-1100 3055 4390 6255
Superplasticizer Used Rheobuild-1100 W/C Ratio Cement saving (%) Slump Compressive Strength (Psi) 3 Days 7 Days 28 Days 0.0% 058-22 - 4070 6005 0.40% 0.58 3.08% 21-4095 6065 0.50% 0.58 4.18% 19-4120 6082 0.60% 0.58 5.62% 22-4168 6098 0.70% 0.58 7.15% 23-4192 6105 0.80% 0.58 8.30% 24-3845 5430 Table 8 TEST RESULTS SHOWING EFFECT OF SUPERPLASTICIZER ON CEMENT SAVING AT CONSTANT WORK ABILITY AND CONSTANT W/C RATIO (SERIES- 3) TRIAL MIX RATIO (1:1.5:3) Table 9 TEST RESULTS SHOWING EFFECT OF SUPERPLASTICIZER ON CEMENT SAVING AT CONSTANT WORK ABILITY AND CONSTANT W/C RATIO (SERIES- 3) TRIAL MIX RATIO (1:1.5:3) Superplasticizer Used Rheobuild-561 M W/C Ratio Cement saving (%) Slump Compressive Strength (Psi) 3 Days 7 Days 28 Days 0.0% 0.58-21 - 4064 6018 0.40% 0.58 3.21% 19-4136 6082 0.50% 0.58 4.58% 21-4172 6115 0.60% 0.58 5.82% 23-4196 6158 0.70% 0.58 7.96% 22 4230 6194 0.80% 0.58 8.85% 23-3995 5545 3. Conclusion On the basis of observation on test result it can be stated that properties of concrete in fresh and hardened stages have been improved with the addition of both types of superplasticizer for all nominal mixes of concrete the rheobuild561m have shown however more pronounced in terms of increase in the compressive strength, workability, water reduction, cement saving requirements of concretes.
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