Title: Performance of Reinforced Blast Furnace Slag Cement Concrete Specimens After 10-Years’ Exposure in Bahrain

Author(s): N. H. Olsen and G. R. Summers

Publication: Symposium Paper

Volume: 170

Issue:

Appears on pages(s): 285-308

Keywords: Blast-furnace slag; carbonation; chlorides; climate; concretes; corrosion; impurities; portland cement.

DOI: 10.14359/6827

Date: 7/1/1997

Abstract:
Granulated ground blast furnace slag is widely used as a partial substitute for normal portland cement in concrete. Among others, one of the perceived benefits is that slag cement improves the durability of reinforced concrete structures. Numerous investigations have reported enhanced resistance to steel reinforcement corrosion. There are two aspects to enhancing resistance to reinforcement corrosion. The first is the ability of the concrete to resist the penetration of chlorides. The second is the degree of corrosion once the chlorides have reached the reinforcing steel. This presentation considers the performance of specimens once chlorides have reached the depth of steel reinforcement. The Ministry of Works & Agriculture has monitored the performance of 96, 100 by 100 by 300 mm reinforced concrete specimens for ten years; exposed to the Bahrain environment. The environment is classified as an ultra hot climate with extreme temperature, extreme solar radiation and extreme chloride salt concentrations in the air and seawater. The specimens were cast with three types of cementitious material: 1) normal portland cement, 2) site-blended slag cement, consisting of 30 percent portland cement and 70 percent slag and 3) preblended slag cement, typically consisting of 30 percent portland cement and 70 percent slag. The exposure program includes two concrete mixtures (220 and 330 kg/m3 cementitious material), two curing regimes (good and poor) and two depths of cover (10 mm and 20 mm). The concrete was contaminated with 0.4 percent chloride and 1.5 percent sulfate by weight of cementitious material. The exposure specimens made with the slag cements had substantially greater carbonation depths and steel corrosion losses than the specimens made with normal portland cement. This is the result regardless of curing regime,cover to reinforcement and content of cementitious material.