Pak. J. Engg. & Appl. Sci. Vol. 15, July, 2014 (p. 87-94) 87 Behaviour of Normal Concrete Using Superplasticizer under Different Curing Regimes Abstract The performance of concrete primarily depends upon the type and ratio of its constituents, compaction, curing conditions and admixtures used during curing process. Part of this research emphasis to calculate the consequences on strength of concrete when water-cement ratio is constant and the increase in slump occurs with the increase in amount of superplasticizer by percentage. The rest of the investigation is carried out to study the effects of superplasticizer with different dosages under different curing regimes at an ambient field temperature ranges between 45°C-50°C. For this purpose, a concrete mix at 20MPa with all parameters constant was prepared by using an ASTM C494 type A, and F, anionic melamine polycondensate non-toxic superplasticizer with no chlorides. Different dosages of superplasticizer were used in different batches of all 95 specimens, and cured under different curing conditions and then tested for compressive and tensile strengths following ASTM standards. In all cases, the water curing up to 28 days testing showed maximum strength. The highest and lowest values of compressive strength were obtained with the addition of 0.5% and 1% superplasticizer respectively. It was found that without increasing the W/C ratio, the addition of superplasticizer exhibits increase in strength. Key Words: Curing, superplasticizer, workability, slump increase, strength. 1. Introduction 1.1 General In modern days, the need of optimum and rapid construction has given rise to the use of chemical admixtures. Among these admixtures, particularly, superplasticizer has a great market nowadays as workability is one of the major issues of a freshly prepared concrete, which can be enhanced by superplasticizer. These superplasticizers, on one hand, lower the water-cement ratio and on the other hand, they improve the workability of concrete. Advanced concrete technology, therefore, requires the detailed study of effects of superplasticizer upon the workability of concrete. The workability can be enhanced by using exact required amount of superplasticizer. Usually, manufacturers indicate the effects of such admixture; however, their action and performance should be checked before use. When concrete is fresh, it is desirable to be malleable or workable. But sometimes, due to scorching conditions at site, desirable workability cannot be maintained. Then superplasticizer enhances the workability to sufficient extent by lowering the shear and flow resistance [1]. Even in the case of self-consolidating concrete, superlasticizer greatly enhances the workability of fresh and hardened concrete [2, 3]. Normally, the chemicals used for reducing water quantity are liquids and possess less than 0.5% of cement weight. In these chemicals, solid’s contribution ranges from 30% to 40% of total volume. In low range water reducers, high retardation and bleeding may occur but, comparatively, high range water reducing chemicals can be added from 0.7%-2.5% of cement weight [4]. The subjects of interest for this study, superplasticizers, are generally chemicals of the type presented in Table 1 [5]. Superplasticizers are usually classified according to following polymer groups [6]: • Sulfonated melamine-formaldehyde condensates (SMF) S N R Shah, Muhammad Aslam, S A Shah, Raja Oad 1. Assistant Professor, Department of Civil Engg. MUET, SZAB Campus, Khairpur Mir’s, Pakistan. 2. PhD Scholar, Department of Civil Engg: University of Malaya, Malaysia. 3. Lecturer, Department of Civil Engg: MUET, MUET, SZAB Campus, Khairpur Mir’s, Pakistan. Corresponding Author: Syed Naveed Raza Shah, Email: naveedshah@muetkhp.edu.pk 1 2 3 3