Abstract
Whether chloride resistance is highly influenced by chloride binding capacity remains unknown. In this study, the chloride resistance of Portland cement-based mortar incorporating aluminate cement and calcium carbonate was investigated considering the chloride binding capacity, pore structures and chloride diffusion coefficient from non-steady state chloride migration and natural chloride diffusion. The cement hydrates were investigated using X-ray diffraction and thermogravimetric analysis. The chloride binding capacity was evaluated based on the chloride adsorption from the solutions using the adsorption isotherm. The aluminate cement, as an available alumina source, can stimulate the formulation of layered double hydroxides, which in turn can increase the chloride binding capacity. The results of mercury intrusion porosimetry show that non-substituted (control) and substituted (only aluminate cement) specimens have capillary pore volume 8.9 vol % and 8.2 vol %, respectively. However, the specimen substituted with aluminate cement and calcium carbonate shows a higher capillary volume (12.9 vol %), which correlates with the chloride diffusion coefficient. Although the specimen substituted with calcium carbonate has a higher chloride binding capacity than the control, it does not necessarily affect the decrease in the chloride diffusion coefficient. The capillary pore volume can affect not only the chloride diffusion but also the chloride adsorption.
Highlights
Chloride does not directly affect the deterioration of concrete but the chloride attack on steel-reinforced concrete causes severe problems due to steel corrosion [1]
We report our findings on the chloride diffusion properties of ordinary Portland cement (OPC)-based mortar blended with HAC and CaCO3 considering the pore characteristics and chloride binding capacity
The oxide composition was analyzed by X-ray fluorescence spectroscopy (Axios, PANalytical, Almelo, The Netherlands) and the loss of ignition was measured by thermogravimetric analysis (TGA; DTG-60, Shimadzu, Japan)
Summary
Chloride does not directly affect the deterioration of concrete but the chloride attack on steel-reinforced concrete causes severe problems due to steel corrosion [1]. The approaches for the durability design of concrete in a high saline environment are based on factors such as the water-to-cement ratio, concrete strength and minimum values for unit cement content [2,3]. These are essential factors for the service life design of the concrete because the properties considered in most standards and codes for concrete durability [2,3] are related to the permeability of concrete and are influenced by the porosity, the capillary pores.
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