Abstract
Concrete's durability where sulfate and chloride ions coexist is a challenging issue. In addition, utilization of limestone powder (LS) in blended cements tended to result in physically and chemically different hydration processes compared with other cements. The present study aims to evaluate Cl− ingress into concrete samples containing LS in the presence of sulfates in exposure environment. In this regard, 3 different exposure conditions of 165 g/l NaCl, 27.5 g/l Na2SO4 + 165 g/l NaCl, and 55 g/l Na2SO4 + 165 g/l NaCl solutions have been designated. Compressive strength, capillary water absorption, surface electrical resistivity, and rapid chloride ions migration tests have been carried out and the total and water-soluble Cl− penetration profiles were determined. Besides these experimental studies, thermodynamic modelling was conducted to simulate the phase assemblage of samples before and after exposure to NaCl and Na2SO4 solutions. According to the results, using LS in concretes is followed by an increase in permeability and a decrease in compressive strength, which agree well with the outcomes of thermodynamic modelling. In the case of single Cl− attack, adding LS results in up to 60.7% and 36.0% increase in apparent and non-steady state Cl− diffusion coefficients, respectively. In addition, both thermodynamic modelling and experimental studies show that the presence of sulfate ions decreases the chemical Cl− binding ability of binders, and the Cl− diffusion coefficient of samples exposed to the combined condition increases. However, by increasing the sulfate ions concentration, the Cl− ingress may be retarded.
Published Version
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