Application of the Maturity Method for Improved Concrete Quality Control in Kenya

Abstract

In Kenya, quality control of concrete involves taking samples of poured concrete and preparing specimens which are then stored under controlled conditions in laboratories. The specimens are subjected to strength testing at predetermined ages to ensure that the design strength is achieved in 28 days. However, the temperature of the concrete placed in a structure is rarely the same as that of the specimens. Depending on prevailing in-situ temperature conditions, concrete strength prediction based on the 28-day rule may be inaccurate. The maturity method of estimating in-situ concrete strength, which was developed by the US National Bureau of Standards, provides a basis for estimating the in-situ strength of concrete by monitoring the temperature of the concrete over time. However, this method is based on the assumption that concrete is prepared according to American standards. This research sought to determine the applicability of the maturity method to concrete prepared according to British standards, which are used to design structural concrete in Kenya. Two concrete mixtures were prepared, one according to American standards and the other according to British standards. For each mixture, the strength and temperature of concrete was determined at ages of 1, 3, 7, 14, and 28 days. The recorded temperature was used to calculate the maturity of the concrete. Strength-maturity relationship curves were then developed for each concrete mixture. Although strength tended to be slightly higher for concrete prepared according to British standards, maturity was the same for the two concrete mixtures at all test ages. It was concluded that the maturity method is applicable to concrete prepared according to British standards. In order to reduce structural failure resulting from inaccurate prediction of concrete strength, we recommend that this method be applied to the Kenyan construction industry