Concrete mix design for hot weather

Abstract

The design of a concrete mix is a complex procedure. It depends on many factors such as properties of materials, method of preparation, compaction, placement and curing of concrete, as well as the requirements of a construction job such as workability and durability. Once these factors are specified, the remaining task involves proportioning of the quantities of materials. This is usually carried out in terms of determining the water-cement ration, aggregate-cement ratio or cement content, and sand to total aggregate ratio for particular gradations of aggregates and maximum size of coarse aggregate. This procedure becomes more difficult to achieve for an optimum mix design in hot weather conditions. In order to develop a suitable method for concrete mix design in hot weather, the effects of the following factors are considered : (1) water-cement ratio, (ii) total aggregate to cement ratio, (iii) sand to total aggregate ratio, and (iv) concrete mix temperature at placement in conjunction with field conditions for curing in hot weather. To examine the effects of the above factors on compressive strength and workability of concrete, the method of factorial experimental design was adopted which enables the evaluation of the combined effects of various factors and their interactions. The data for workability, in terms of slump, and the compressive strength was subjected to regression analysis to develop equations for predicting compressive strength and workability. The equations were used through a computer program to generate tables for use in concrete mix design.