Effects of Polymer Latex and Expansive Agent on the Resistance of Cement Asphalt Pastes to Sulfuric Acid Attacks

Abstract

Two types of polymer latexes and one expansive agent were employed to investigate their effects on the resistance of cement asphalt (CA) pastes to sulfuric acid. Mercury intrusion porosimetry, a thermogravimetric analysis, and scanning electron microscopy were performed to analyze the microstructure of the CA pastes. Anticorrosion coefficients were calculated by comparing the compressive strength before and after corrosion. Results show that the chemical attack by sulfuric acid on the CA pastes begins from the neutralization reaction, accompanied by the crystalline expansion of calcium sulfate in pores and the decompositions of C-S-H gel and asphalt. At a mass ratio of asphalt to cement (A/C) of 0.2, Latex I enhances the anticorrosion coefficients of the CA pastes at low dosages but reduces them at high dosages. In contrast, Latex II results in a completely inverted effect on the anticorrosion coefficients. At an A/C of 0.6, the addition of both Latex I and II visibly increases the anticorrosion coefficients, owing to the binding effect of latex on hydrates. Compared to Latex I, Latex II results in a more obvious increase in the anticorrosion coefficients. With the inclusion of the expansive agent, the anticorrosion coefficients of the CA pastes at the A/C of 0.2 sharply decrease, while the ones at the A/C of 0.6 significantly increase. It is concluded that the precipitation of calcium sulfate crystals in a compact structure produces expansion stress and microcracks, thereby decreasing the strength and anticorrosion coefficients of CA pastes at low A/C values. In the case of high A/C values, the paste structure is difficult to be damaged, owing to the binding effects of asphalt membranes. Hence, the anticorrosion coefficients are increased by adding the expansive agent.