Mechanical Properties and Chloride Ion Penetration of Alkali Activated Slag Concrete

Abstract

Compared to ordinary Portland cement (OPC) concrete, alkali activated compounds refer to inorganic materials that cement is not the main constituent in their mixes. In fact, alkali activated concretes have two main parts in their binder structure: source material and alkaline activator liquid. In this study, the binder consists of blast furnace slag as a source material and sodium silicate solution (wt. ratio: SiO₂/Na₂O = 2.33) and 6 M potassium hydroxide which are incorporated as alkaline activator liquids. Since there are several parameters that affect the properties of these concretes, 9 alkali activated concrete mix designs are utilized to investigate the influence of source material amount, solid part of alkaline activator, solid part of sodium silicate solution and the ratio of water to binder. Furthermore, one mix design for OPC concrete is performed to compare with alkali activated slag (AAS) concrete characteristics.

In this investigation, the fresh concrete properties are reported for these mix designs through slump loss test. Additionally, the compressive strength of the samples is measured at 1, 7, 28, 90 and 180 days ages. Moreover, because of the influence of chloride ion penetration that initiates corrosion of the reinforcement steel, chloride ion ingress is examined by diffusion tests based on NT Build 443. Besides, color change boundaries (CCB) in each specimen are measured to determine the penetration depth.

According to the results, mechanical properties and durability of AAS concretes are mostly influenced by the alkaline activator liquid contents and also it was observed that these characteristics development is decelerated specially by increasing the amount of activators.