ITEE Innovation Expo 2008 : Project Details

early stage compressive strength prediction of steam cured concrete

This project aims to predict the early age compressive strength of pre-cast concrete being used in the North South Bypass Tunnel (NSBT) culverts. The culverts are cured in a temperature controlled environment at Humes Eagle Farm site. The curing process involves heat treatment of the concrete by means of a controlled steam application system. Because of the fact that the culverts are being cured in a mould, it is of cardinal importance to allow necessary hydration before the mould can be stripped and the culvert escalated from the mould. The aim was accomplished by casting test cylinders comprising of the same concrete mixture, and after curing these cylinders under nearly the same conditions as the culvert itself, the cylinders were tested for compressive strengths at different times after the steaming process. At the same time, the equivalent age of the concrete inside the cylinders was being recorded with the use of thermo couples connected to a data logger. The equivalent ages of the concrete comprising the cylinders were recorded at the time of compressive strenght testing.This was done by implementing the Arrhenius equation. This procedure created both a log-equivalent age as well as a compressive strength for each tested cylinder. By use of the Plowman equation the strength can be expressed as a function of the log equivalent age. The process was repeated 20 times and a linear regression was run to estimate and equation that can predict the compressive strength of the concrete given the equivalent age. Finally, in order to predict the early age compressive strength of the concrete without sacraficing the structure of the culvert, the equivalent age of the concrete within the culvert itself was also recorded during the curing process. Given this equivalent age, the concrete strength was predicted. The project also served as a way of ensuring Main Road Standards were being met.