Effects of acidic environments and sorptivity on high-performance concrete containing natural pozzolan and limestone filler

Even though high-performance concrete (HPC) is a more robust type of concrete, acidic environments can still have a negative impact on it. Acids can dissolve other components in the concrete as well, leading to a loss of material and increased porosity. This makes the concrete even more susceptible to further degradation. Acidic environments attack the calcium hydroxide (CH), a key component of the cement paste that binds the aggregate in concrete. This reaction weakens the structure and reduces the overall strength of the concrete. The purpose of this study is to assess how HPC containing natural pozzolan (NP) and limestone filler (LF) responds to acidic environments and sorptivity. The cement (PC) was replaced by NP and LF in different mass proportions. The mixtures HPCC (100% PC), HPC18 (10%LF + 90%PC), HPC7 (20%NP + 80%PC), and HPC14 (5%LF + 10%NP + 85%PC) were prepared. The sorptivity was evaluated by measuring the sorptivity coefficient (S, cm*s-0.5) after 28 days of submersion in distilled water. HPC specimens were submersed in distilled water, 5% sulfuric acid (H2SO4), and 5% hydrochloric acid (HCl) for up to 180 days in order to test their acid resistance. Visual inspection and changes in mass were used to evaluate the specimens' resistance to acid attack. The results showed that replacing PC with LF and NP reduced the sorptivity of HPC. Substituting 10% of PC mass with LF increased the HPC's resistance to sulfuric acid. However, substituting the PC with NP and/or LF reduced the HPC's resistance to hydrochloric acid. According to visual inspection and mass losses, the sulfuric acid was more aggressive than hydrochloric acid.