Exploiting potential use of partially deteriorated cement in concrete mixtures

Whenever cement is left unused for a long time or improperly stored, it deteriorates. The degree of deterioration mainly depends on the duration and condition of storage. Due to this, cement partially or completely loses its engineering qualities. Even if such cement is only 10% of total 100 million tonnes cement produced in India, total quantity available for use would be in the range of 10 million tonnes. The aim of this study is to develop a stepwise procedure to proportion plain concrete mixes using partially deteriorated cement. Extensive laboratory studies are done to study the behavior of concrete with partially deteriorated cement. Conventional methods of mix design such as British Method, ACI and country's standard code can be used directly for concrete containing standard cement which satisfies prescribed specifications. When deteriorated cement is used these conventional methods of mix design fail as its physico-chemical interacting particulate characteristics would have been reduced to low levels. The re-proportioning of concrete mixes did not yield the required strength and workability when only deteriorated cement was used. However, the performance of the concrete could be improved by replacing a part of the deteriorated cement by fresh cement. As the fresh cement content increases, the strength and workability of the concrete also improved. Using these modified mixes, re-proportioning could be made for other levels of strength and even up to that of 100% fresh cement concrete. The procedure is validated through a series of experimental trials.