Non-Ferrous Slag as Cementitious- Material and Fine Aggregate for Concrete

A non-ferrous slag from the production of metallic zinc was studied as a new ingredient for concrete. It was used in two forms: ground and un-ground material. The ground slag replaced 15% of portland cement, whereas the un-ground slag replaced 20% of the natural sand. Five different concrete mixtures were studied, all with a water-cementitious materials ratio of 0.60: reference mixture with portland cement and natural aggregates; concrete mixture with ground non-ferrous slag replacing portland cement; concrete mixture with un-ground non-ferrous slag replacing sand; concrete mixture with ground non-ferrous slag replacing portland cement and un-ground slag replacing sand. Additionally, for comparative purposes, a ground granulated blast-furnace slag was used to replace 15% portland cement. The following properties were studied: compressive strength; heat development through change in temperature; and immobilization of heavy metals of the non-ferrous slag through water-leaching tests. The compressive strength development of the concrete with the ground non-ferrous slag was the same as that of the corresponding concrete with ground, granulated blast-furnace slag. When un-ground slag was used to replace sand there was a negligible decrease in the early compressive strength. When both ground and un-ground non-ferrous slag were used there was a significant retardation in the development of compressive strength during the first 2 days. The early heat development was slightly reduced due to the portland cement replacement and the temperature peak was significantly delayed when both ground and un-ground non-ferrous slag were used. The leaching by water of heavy metals from the hardened specimens was negligible and then the immobilization of zinc and lead of the slag into the cement matrix was very effective.