Self-compacting concrete: using limestone to resist sulfuric acid

Abstract

Self-compacting concrete (SCC) is increasingly being used in precast concrete sewer pipes, water treatment facilities, industrial floors and foundations that are susceptible to biogenic and/or chemical sulfuric acid attack. Since the mixture design of SCC is different to that of normal concrete, the durability of SCC in such applications needs to be evaluated. In particular, SCC can incorporate proportions of limestone filler and different combinations of aggregates, which is believed to alter its resistance to sulfuric acid. Hence, this study aimed to investigate the resistance to sulfuric acid of various SCC mixtures incorporating different limestone material types, proportions and combinations. The study comprised 12 weeks of immersion of test specimens in 1, 3 and 5% sulfuric acid solutions with a maximum pH threshold of 3, 2 and 1, respectively. The study revealed that the resistance to sulfuric acid of SCC incorporating limestone materials was dependent on the degree of solution aggression. While limestone filler contributed to increasing the resistance of SCC to the moderately aggressive solution (3% sulfuric acid), it accelerated the rate of mass loss in the highly aggressive solution (5% sulfuric acid). The effect of fineness and particle size of limestone and the kinetics of corrosion reaction on the resistance of SCC to sulfuric acid was also highlighted in this study. Microanalysis conducted upon test termination elucidated the damage mechanisms, and it was shown that the change in compressive strength after exposure to sulfuric acid solutions was not a proper indicator for the surface deterioration of SCC in acidic media.