EFFECT OF SUPERPLASTICIZERS ON WORKABILITY AND STRENGTH OF CONCRETE

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1 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: August 2005, Singapore Article Online Id: The online version of this article can be found at: This article is brought to you with the support of Singapore Concrete Institute 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

2 30 th Conference on OUR WORLD IN CONCRETE & STRUCTURES: 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 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 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.

3 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 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.

4 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.

5 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 Rheobuild @0.80% Rheobuild-561 M@0.80% EFFECT OF S.P ON COMPRESSIVE STRENGTH AT CONSTANT W/C RATIO Compressive Strength i(p i) Ages of testing Days 7 Days 28 Days Nil Rheobuild Rheobuild-561 M EFFECT OF SUPPER PLASTICIZER ON COMPRESSIVE WORKABILITY AT CONSTANT W/C RATIO Slump Superplasticizer Nil Rheobuild-1100 Rheobuild-561M

6 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 Rheobuild @0.80% Rheobuild-561 M@0.80% EFFECT OF S.P ON COMPRESSIVE STRENGTH AT CONSTANT W/C RATIO Compressive Strength i(p i) Ages of testing 3 Days 7 Days 28 Days Nil Rheobuild Rheobuild-561 M EFFECT OF SUPPER PLASTICIZER ON COMPRESSIVE WORKABILITY AT CONSTANT W/C RATIO Slump Superplasticizer Nil Rheobuild-1100 Rheobuild-561M

7 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 Rheobuild-1100@0.80% Rheobuild-561 M@0.80% EFFECTS OF S.P ON COMPRESSIVE STRENGTH AT CONSTANT W/C RATIO Compressive Strength psi (Psi) Ages of testing 3 Days 7 Days 28 Days Nil Rheobuild Rheobuild-561 M EFFECT OF SUPPER PLASTICIZER ON COMPRESSIVE WORKABILITY AT CONSTANT W/C RATIO Slump Superplasticizer Nil Rheobuild-1100 Rheobuild-561M

8 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 Rheobuild-1100@0.80% Rheobuild-561 M@0.80% MIX RATIO (1:1:5:3) Superplasticizer Used W/C Ratio Slump 28 Days Splitting Tensile Strength (Psi) Nil Rheobuild-1100@0.80% Rheobuild-561 M@0.80% (SERIES-1) MIX RATIO (1:1:2) Superplasticizer Used W/C Ratio Slump 28 Days Splitting Tensile Strength (Psi) Nil Rheobuild-1100@0.80% Rheobuild-561 M@0.80%

9 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 Rheobuild-1100@0.80% Rheobuild-561 M@0.80% MIX RATIO (1:1.5:3) Superplasticizer Used W/C Ratio Slump 28 Days Tensile Strength (Psi) Nil Rheobuild-1100@0.80% Rheobuild-561 M@0.80% MIX RATIO (1:1:2) W/C Ratio Slump 28 Days Tensile Superplasticizer Used Strength (Psi) Nil Rheobuild-1100@0.80% Rheobuild-561 M@0.80%

10 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% % % % % % % % % % % EFFECTS OF SUPERPLASTICIZER ON COMPRESSIVE STRENGTH AT CONSTANT WORKABILITY 6500 Compressive Strength i(p i) Ages of testing 3 Days 7 Days 28 Days Nil Rheobuild

11 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% % % % % % % % % % % EFFECTS OF SUPERPLASTICIZER ON COMPRESSIVE STRENGTH AT CONSTANT WORKABILITY Compressive Strength i (P i) Ages of testing 3 Days 7 Days 28 Days Nil Rheobuild

12 Superplasticizer Used Rheobuild-1100 W/C Ratio Cement saving (%) Slump Compressive Strength (Psi) 3 Days 7 Days 28 Days 0.0% % % % % % % % % % % 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% % % % % % % % % % % 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.

13 4. References [1] RIXOM, M.R and MAILVGANAM, N.P. Chemical admixtures for concrete, [Second edition],publisher E.and F.N. Spon[London],pp 1-91 and [2] RAMACHANDRANV.S, FELDMANR.F, BEAUDOIN J.J Concrete Science-Treatise on current research, pp and Heyden and sons Limited, Philadelphia, [3] Collepradi, M, Concrete Admixtures Hand Book 2 nd Edition Noys Publisher, 1995 pp.359 [4] Hewiett, P.C. Superplasticizing admixtures in concrete Cement and Concrete Association Publication, Vol.45, NO. 30, 1976 [5] Basile et. Al Influence of different sulfonated Polymers on the fluidity of cement paste Proceeding of third International Conference CANMET/ACI Ottawa, 1989 pp [6] Glanville, W.H., Collins, A>R and Mathews The grading of aggregates and workability of concrete. Road Research Technology paper London. [7] Aignesberger, A, and Kern, A Use of melamine based superplasticizers as water reducers. ACI Special Publication 1981, pp [8] Kinoshita,M, et.al application of new superplacticizer fro Ultra high strength concrete. Proceedings of Japan cement association Japan [9] Rivera, R, Davila., and Durn. A High performance concrete using fly ash and superplasticizers Proceeding of International Symposium on High Performance and Reactive Powders concretes Sherbrook [10] New Types of concrete. Concrete in developing countries material design and construction, Vol-1. Proceeding of International colloquium, Lahore (Pakistan) 1985, pp