Accuracy in Estimating the Mix Proportions of Hardened Concrete

It is necessary to know and control inner factors which influence durability when structures are designed and constructed. The most important factor is mix the proportions, especially the water-cement ratio. Therefore, the accuracy of estimating the water-cement ratio is the most important point in evaluating durability and estimating life time. However, in the case of existing concrete structures, there is no documentation in most cases. Consequently, in many cases estimation of the water-cement ratio from a hardened concrete sample is necessary for existing structures. This method is shown in papers of CAJ and JSCE. But there are few experiments and little consideration about the accuracy of estimating mix proportions of hardened concrete. In this paper, accuracy in estimating mix proportions of hardened concrete is studied. And the following results were attained. (1) In order to improve the accuracy of estimating mix proportions, the accuracy of quantifying CaO and measuring attached water must be improved. (2)The test of attached water measurement must be conducted before strength tests on the specimen for estimating mix proportions, because large errors in estimating the amounts of attached water will influence the estimation of the water-cement rati