Durability of mortars and concretes containing scoria-based blended cements

A lot of reinforced concrete (RC) structures in Syria went out of service after a few years of construction. This was mainly due to reinforcement corrosion or chemical attack on concrete. The use of blended cements is growing rapidly in the construction industry due to economical, ecological and technical benefits. Syria is relatively rich in scoria. In this study, mortar/concrete specimens were produced with seven types of cement: one plain Portland cement (control) and six blended cements with replacement levels ranging from 10 to 35%. Rapid chloride penetration test (RCPT) was carried out according to ASTM C 1202 after two curing times of 28 and 90 days. The effect on the resistance of concrete against damage caused by corrosion of the embedded steel has been investigated using an accelerated corrosion test (ACT) by impressing a constant anodic potential. The variation of current with time and the time to failure of RC specimens were determined at 28 and 90 days curing. The specimens were also monitored periodically. In addition, effects of aggressive acidic environments on mortars were investigated through 100 days of exposure to 5% H 2 SO 4, 10% HCl, 5% HNO 3 and 10% CH 3 COOH solutions. Evaluation of sulfate resistance of mortars was also performed by immersing in 5% Na 2 SO 4 solution for 52 weeks. Test results reveal that the resistance to chloride penetration of concrete improves substantially with the increase of replacement level, and the concretes containing blended cements, especially CEM II/B-P, exhibited corrosion initiation periods several times longer than the control mix. Moreover, a definite correlation is observed between RCPT and ACT. An increase in scoria addition improves the chemical resistance of mortar, especially in the early days of exposure, whereas after a long period of continuous exposure all specimens show the same behavior against the chemical attack. According to results of sulfate resistance, CEM II/B-P can be used instead of SRPC in sulfate-bearing environments.