We investigated the sulfuric acid resistance of low-calcium alkali-activated materials (i.e., geopolymers) supplemented with an iron mineral admixture (i.e., hematite). Geopolymers without and with 5% hematite were produced at two alkali contents (Na:Al = 0.86 and 1.39). Acid degradation reactions were comprehensibly studied through three replenishes of acid. Results demonstrate that hematite is chemically active upon acid exposure yielding a short-term increase in acid neutralization capacity. Prolonged acid resistance was enhanced in high alkali content formulations with hematite. Acid exposure revealed minimal changes to mineralogy, molecular structure, and micro-scale porosity in these samples, resulting in less dealumination and silicon leaching. Thus, results indicate that the acid buffering capacity of geopolymers, specifically at higher alkali content formulations, increases due to the addition of hematite. The increased buffering capacity leads to lower degrees of dealumination of the N-A-S-H cementitious binder. These results are important to explain the increased acid durability of alkali-activated materials synthesized from industrial aluminosilicate precursors (e.g., slag, fly ash, lateritic clays) that may contain iron minerals.

我们研究了低钙碱活化材料（即地质聚合物）和铁矿物掺合料（即，赤铁矿）。在两种碱含量（Na：Al = 0.86和1.39）下生产不含和含5％赤铁矿的地聚合物。通过补充三种酸全面地研究了酸降解反应。结果表明，赤铁矿在暴露于酸中后具有化学活性，会导致酸中和能力的短期增加。在含赤铁矿的高碱含量配方中，延长了耐酸性。酸暴露显示这些样品的矿物学，分子结构和微孔率变化很小，从而导致脱铝和硅浸出减少。因此，结果表明，地质聚合物的酸缓冲能力，特别是在碱含量较高的配方中，由于添加了赤铁矿而增加。增加的缓冲能力导致NASH胶结粘结剂的脱铝程度降低。这些结果对于解释由工业铝硅酸盐前体合成的碱活化材料的耐酸耐久性提高具有重要意义（（例如矿渣，粉煤灰，红土）中可能含有铁矿物质。