The Effect of the Properties of Constituent Materials on the Quality of Concrete in Kenya

Kenya’s long term strategic plan under Vision 2030 includes, among others, a large component of infrastructure development to meet the demand for its population. Reinforced concrete is the most commonly used construction material in the country and therefore it forms an integral part of this development plan. In the recent past, Kenya has experienced a worrying rate of collapse of reinforced concrete buildings during construction. This phenomenon has been partly attributed to the quality of in-situ concrete and poor workmanship among other factors. Currently the concrete mix design methods used in Kenya are based on Ordinary Portland cement (42.5) which is normally directly replaced by the blended Portland cements (32.5). Thiswork presents findings of an experimental investigation on the effects of cement type and properties of fine aggregates on the quality of concrete in Kenya. Four different brands of cement and fine aggregates from three different locations in the country were used during the study. The effect of eucalyptus plant extracts on the quality of concrete was also investigated. The British DOE mix design method was used to generate the concrete mix proportions. It was observed that the currently used mix design methods lead to production of concrete with compressive strengths that are less than the target strengths at 28days when the blended Portland cement 32.5N/mm2 is used. Concrete made from Tiwi sand also had higher strengths compared to the other fine aggregates used inthe experiments. It was further observed that Eucalyptus leaf extracts helped to increase both the initial and ultimate compressive strength development for the four selected cement brands. The studytherefore proposes that a mix design procedure be developed for blended Portland cement concrete