Investigation of the use of obsidian and zinc slag powder additives in self-compacting concrete

Self-Compacting Concrete (SCC) is a special concrete type with good workability but expensive because of more cement requirement. For decrease cost of SCC, the use of various mineral additives is being investigated. In this study, the effects of the use of obsidian and zinc slag powder additives in SCC production on the workability, unit weight, compressive and splitting tensile strength, ultrasonic pulse velocity, rebound (Schmidt), capillary water absorption and abrasion resistance properties of concrete were investigated. This study consists of two stages. In the first stage; the pozzolanic activities of the mortar samples produced by substituting 2.5-5-7.5-10% by weight of zinc slag and 5-10-15-20-25% by weight of obsidian powder instead of cement were determined after 56 and 90 days curing periods. In the second stage; based on the pozzolanic activity results, SCC groups with constant dosage of 577 kg/m3 were formed by replacing cement with zinc slag and obsidian additives as selected ratios, and then experiments were carried out to determine the investigated fresh and hardened concrete properties of these groups. As a result of the study, the optimum replacement ratios of the materials with pozzolanic activity indexes in the range of 64-88% were determined as 5% for zinc slag and 15% for obsidian. It has been observed that the use of zinc slag and obsidian powder additives in SCC production has positive effects on workability, partially reduces the mechanical performance, but increases the abrasion resistance by 49% after 90 days of curing. Although it partially reduces the other mechanical properties of concrete, it is thought that these materials can be preferred in SCCs used in road etc. productions due to their economic and environmental advantages.