Abstract
A realistic forecast of the impact of CaCl2-blended acrylic polymer (CP) emulsions on steel reinforcement corrosion is difficult without a detailed study. This is traceable to the conflicting effects of cement additives on the chloride threshold value, pore solution chemistry, and matrix resistivity. Hence, in the study reported herein, the actual influence of 0.5–1.5 wt% CP on rebar corrosion was assessed via an accelerated corrosion test. The macrocell current, half-cell potential measurements (HCP), reinforcement cover crack propagation, and rebar deterioration were monitored. The resistance of mortar specimens to acid-induced degradation was also evaluated over time. The corrosion test results indicate that steel rebar corrosion initiation in the mortar expedited as the CP dosage in mixtures increased. Consequently, the time required for the CP-modified specimens to crack shortened. Moreover, non-uniform rebar section loss and surface crack width widening were also observed in CP-modified mortar specimens. However, X-ray diffraction (XRD) analyses of the plain Ref and 1.5% CP corrosion byproduct residues indicated that key phases such as akaganeite, goethite, lepidocrocite, hematite, and magnetite were quantitatively similar. Interestingly, the addition of 1.0–1.5% CP to mixtures enhanced the acid attack resistance of mortars. For now, these results indicate that CP should only be used as a chemical admixture in unreinforced cement composites.
Highlights
The capacity of calcium chloride (CaCl2) to accelerate early-age strength gain in cement composites is well known
Given that chloride-induced steel reinforcement corrosion is a major cause of reinforced concrete (RC) durability problems worldwide, the use of chlorides and chloride-based admixtures in cement composites is prohibited by building standards such as British Standard European Norm BS EN 206-1 [1]
This study investigated whether the previously observed positive benefits of CaCl2blended acrylic polymer (CP) on some durability properties of cement composites [21,22] could be extended to the steel rebar corrosion protection and acid attack resistance of cement mortars
Summary
The capacity of calcium chloride (CaCl2) to accelerate early-age strength gain in cement composites is well known. Many studies [3–5] have been dedicated to evaluating chloride–cement matrix interactions and establishing the critical chloride threshold for the initiation of steel reinforcement corrosion This critical chloride content is mostly expressed as free/total chloride and the chloride-to-hydroxyl ion ratio [Cl−]/[OH−]. Andrade and Page [3] investigated the effects of sodium chloride (NaCl) and calcium chloride (CaCl2) on reinforcement corrosion at the same total chloride content of 0.4–1.0%. They observed that despite the lower [Cl−]/[OH−] ratio and reduced free chloride content of the pore solution, rebar corrosion was more aggressive in CaCl2-blended paste mixtures. For concrete internally admixed with either of the two chemical additives, the [Cl−]/[OH−] ratio and risk of reinforcement corrosion were higher in the CaCl2-admixed concrete
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