Utilization of kimberlite tailings as aggregates in concrete - Strength and selected durability properties

The feasibility of using kimberlite tailings as aggregates in concrete was assessed. Compressive strength and selected durability tests were carried out on concretes made using various replacement levels (0, 40, 60 and 100%) fine and/or coarse blended crushed andesite and kimberlite tailings as aggregates. A w/b ratio of 0.50 and a CEM I 52.5R were used. The results show that the kimberlite tailings as aggregates have a relatively high water demand which was manifested as a reduction in workability of the fresh concretes with kimberlite tailings as a proportion of either fine and/or coarse aggregates. The results also showed that the use of the kimberlite tailings as a proportion of either fine or coarse aggregates in concrete resulted in a decrease in both compressive strength and durability properties viz water sorptivity and oxygen permeability. This was partly attributed to the low workability of the concretes which is known to limit the degree of compaction of fresh concrete. It is envisaged that careful concrete mix proportioning including the use of admixtures and pre-wetting of the aggregates can be used to offset the negative effects of high water demand of the kimberlite aggregates.