Warda Bint Ashraf

Assistant Professor, BUET

Concrete Mix Design Using Locally Available Materials

Concrete Mix Design Using Locally Available Materials

•    Developed “5-10-14-18”and “5-10-18-22” band gradations of aggregate and concrete mix design procedure using contours.
•    Conducted large scale laboratory experiments on cements, aggregates and concrete properties

Concrete is the most popular and widely used construction material in Bangladesh. A prerequisite behind the vast popularity of concrete is to achieve the desirable fresh and hardened properties of concrete. And there is the importance of a concrete mix design method. Concrete Mix Design is the process of selecting suitable ingredients of concrete and determining their relative amounts with the objective of producing a concrete of the required strength, durability, and workability as economically as possible. Numerous researches already have been accomplished in many countries to find out the optimum proportions of concrete ingredients. As a result, many countries already have their own methods of concrete mix proportioning. But there is an exceptional scenario in case of Bangladesh. Although some researches were done for concrete materials but none of these were related to concrete mix proportioning using indigenous materials. Noteworthy that, ACI method of concrete mix design is the most popular method in Bangladesh for concrete works. But one major problem lies in the fact that all requirements of these methods may not be possible to fulfill such as, aggregate gradation (i.e. ASTM C33, BS 882). It is still in question that, whether it is possible to achieve this gradation limits using local aggregates, moreover these aggregate gradation limits and procedure to achieve these gradations are not much common in local concrete production fields in Bangladesh. Aggregate occupies 70 ~ 80% of the volume of the concrete, it is understandable that aggregate affects the various characteristics and properties of concrete. Since required aggregate properties cannot be ensured as per the code prerequisite, the concrete mixes as per ACI or BS may not confirm the mix requirements (i.e. Strength, workability). The main objectives of the projects were- a) Comparative analysis of different aggregate gradation methodology including some recent aggregate gradation and code suggested gradations. b) Parametric study of different aspects of concrete mix design methods.

This research work was mainly experimental based. Within the scope of the research large scale laboratory scale investigation have been conducted on different properties of cement, aggregates and concrete which involved around 70 concrete mixes and so on. For the ease of research purpose total work was divided into three distinct phases. Each of these phases contains different types of mix proportions and number of mixes based on the particular objectives of that phase. (I) Selection of the suitable aggregate gradation methodology. (II) Check the consistency of selected aggregate gradation bands. (III) Laboratory experiments for concrete mix design based on the selected aggregate gradation methodology. The outcomes of the thesis are a suitable aggregate gradation methodology and a mix design procedure using locally available materials.