Abstract
Geopolymers are gaining attention as sustainable alternatives to Portland cement, offering improved acid resistance while reducing environmental impact. The current study evaluates the mechanical properties and durability of a pumice-based geopolymer matrix compared to conventional Portland cement. Therefore, Portland cement and pumice-based geopolymer specimens (GPSs) were subjected to compressive and flexural strength tests at 7 and 28 days. Durability was assessed through acid neutralization capacity (ANC) and mass loss analysis through controlled acid exposure. Subsequently, the compressive strength of Portland cementat 7 days was 32.45 MPa, whereas the geopolymer reached only of about 14.63 MPa. At 28 days, cement increased to 52.22 MPa, while the geopolymer reached 16.27 MPa, yielding a 68.85% lower strength. Flexural strength followed a similar trend, with Portland cement reaching 6.59 MPa at 7 days and 8.22 MPa at 28 days. Hereby, the geopolymer recorded 3.90 MPa and 5.80 MPa, respectively, maintaining a 29.32 % performance gap at 28 days. In terms of durability, ANC tests demonstrated that the geopolymer neutralized 91% less acid (1.43 mmolH+/g) compared to Portland cement (14.08 mmolH+/g), while mass loss resulted to be significantly lower in geopolymers (1.2 % vs. 9.4 % for cement), indicating higher resistance to acidic environment. The novelty of using pumice as a geopolymer precursor instead of fly ash or slag is based on its natural origin, which is rich in amorphous silica and low in calcium, favouring the formation of sodium aluminosilicate hydrate (N-A-S-H) gels that are more stable in acidic environments.
