Abstract
Concrete wastewater infrastructures are important to modern society but are susceptible to sulfuric acid attack when exposed to an aggressive environment. Fibre-reinforced mortar has been adopted as a promising coating and lining material for degraded reinforced concrete structures due to its unique crack control and excellent anti-corrosion ability. This paper aims to evaluate the performance of polyethylene (PE) fibre-reinforced calcium aluminate cement (CAC)–ground granulated blast furnace slag (GGBFS) blended strain-hardening mortar after sulfuric acid immersion, which represented the aggressive sewer environment. Specimens were exposed to 3% sulfuric acid solution for up to 112 days. Visual, physical and mechanical performance such as water absorption ability, sorptivity, compressive and direct tensile strength were evaluated before and after sulfuric acid attack. In addition, micro-structure changes to the samples after sulfuric acid attack were also assessed by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) to further understand the deterioration mechanism. The results show that overall fibre-reinforced calcium aluminate cement (CAC)-based samples performed significantly better than fibre-reinforced ordinary Portland cement (OPC)-based samples as well as mortar samples in sulfuric acid solution in regard to visual observations, penetration depth, direct tensile strength and compressive reduction. Gypsum generation in the cementitious matrix of both CAC and OPC-based systems was the main reason behind the deterioration mechanism after acid attack exposure. Moreover, laboratory sulfuric acid testing has been proven for successfully screening the cementitious material against an acidic environment. This method can be considered to design the service life of concrete wastewater pipes.
Highlights
Sewerage networks and wastewater systems are significant urban infrastructures to modern societies worldwide, conveying the safe transport of sewage from households and industrial sites to wastewater treatment plants
The effect of sulfuric acid (H2 SO4 ) on concrete is complex as it is a combination of acid and sulfate attack
The results show that the ductility of Strain hardening cementitious composite (SHCC) was remarkably decreased after
Summary
Sewerage networks and wastewater systems are significant urban infrastructures to modern societies worldwide, conveying the safe transport of sewage from households and industrial sites to wastewater treatment plants. These valuable assets often suffer serious corrosion and deterioration issues due to external aggressive acid attack, resulting in a huge loss to the economy annually. The effect of sulfuric acid (H2 SO4 ) on concrete is complex as it is a combination of acid and sulfate attack. The chemical reaction of sulfuric acid attack that takes place in concrete sewerage can be seen as follows [1]: Acid attack: Ca(OH)2 + H2 SO4 → CaSO4 ·2H2 O (gypsum)
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