Production of concrete of grade higher than 40N/mm2

Abstract

The scope of this dissertation was to study the factors that affect compressive strength and manipulate these factors to achieve the high required strength without using an admixture. Compressive strength of concrete has been accepted as the most important mechanical properly of structural concrete. Following an extensive literature review, it was observed that some factors which influencing the strength of concrete were: the amount and type of cement, w/c ratio, aggregate type and grading. It was also noticed that there was no specific mix design particularly for high strength, and therefore a number of trial mixes had to be produced. This lead to a mix design method being developed and is put forward in this dissertation. For the purpose of this study, two different fine and coarse aggregate were used: coralline limestone as local aggregate and dolomite as a foreign material. Each aggregate type had different characteristics, thus were of different quality. All these aggregate were tested and all the characteristics observed were noted. Different cement type was also used and the difference in the compressive strength was also noted. Five main concrete mix types were designed for the production of concrete and each type had three different strengths. Cubes were produced and tested for seven and twenty-eight day strengths. The results observed in all the concrete mixes were compared and statistically analysed. From the results obtained, it was concluded that both coarse and fine aggregate actually affected the properties of concrete at all levels of strength , thus it was observed that using local coarse aggregate combining it with dolomite sand, higher strengths could be achieved.