Generally, the phosphoric acid-activated systems use aluminosilicates as raw material (e.g., metakaolin) ; and the addition of alkali metals (e.g., Mg or Ca) contributes to obtain best properties. Volcanic ash (Va) is an aluminosilicate globally available and contain these metal oxides, which makes it a suitable raw material to produce acid-activated cements. The research on the production of this type of cements using Va is relatively recent. The knowledge on some parameters that influence the activation process under acid conditions of Va can be of great value as a viable alternative to its industrial application in the foreseeable future. This study examines the reactivity of four samples of volcanic ashes with different chemical composition in phosphoric acid at ambient temperature (25°C). Two concentrations of phosphoric acid were used (41.1 % and 51.2% P₂O₅ by mass). The main parameter used in this study is the molar ratio R expressed as the relation (MgO + CaO)/P₂O₅. Properties such as setting time, paste temperature in fresh state and compressive strength at 28 days of curing were evaluated. The final products obtained via acid activation of the volcanic ashes were studied using the XRD and FTIR techniques. The results showed that the initial and final setting time and the compressive strength increases with the increase of the molar ratio R of the mix when the proportion of P₂O₅ is constant. This coincides with the decrease in the temperature of the pastes. The highest compressive strength at 28 days of curing (81.3 MPa) was obtained with a molar ratio R = 4.2 and 41.1% P₂O₅ using a volcanic ash with high calcium and magnesium content (13.1% and 9.9% respectively). This volcanic ash when is activated with phosphoric acid of 51.2% P₂O₅ (R=3.0) reported lower strength (40%) and a significant increase in the setting time. The results obtained showed that the CaO and MgO content in the volcanic ash and the acid concentration used as activator are parameters that affect the final properties of the acid-activated cements. Also, the presence of amorphous phase hindered the reactivity. Based on the results, the volcanic ashes may be considered precursors in the production of phosphoric acid-activated cements for construction purposes.

通常，磷酸活化的系统使用铝硅酸盐作为原料（例如偏高岭土）。并且添加碱金属（例如Mg或Ca）有助于获得最佳性能。火山灰（Va）是一种全球可购得的硅铝酸盐，其中含有这些金属氧化物，这使其成为生产酸活化水泥的合适原料。使用Va生产这种类型的水泥的研究相对较新。在可预见的将来，对某些在Va酸性条件下影响活化过程的参数的了解，可作为其工业应用的可行替代品，具有重要的价值。这项研究检查了在环境温度（25°C）下四个不同化学成分的火山灰样品在磷酸中的反应性。使用了两种浓度的磷酸（41。₂ O ₅质量）。本研究中使用的主要参数是摩尔比R，表示为（MgO + CaO）/ P ₂ O _5关系。评价固化时间，新鲜状态下的糊料温度和固化28天时的抗压强度等性能。使用XRD和FTIR技术研究了通过火山灰的酸活化获得的最终产品。结果表明，当P ₂ O ₅的比例增加时，初始和最终凝固时间以及抗压强度随混合物摩尔比R的增加而增加。是恒定的。这与浆料温度的降低相吻合。使用钙和镁含量较高的火山灰（分别为13.1％和9.9％），摩尔比R = 4.2和41.1％P ₂ O ₅可获得固化28天时的最高抗压强度。火山灰在被51.2％P ₂ O _5的磷酸活化后（R = 3.0）报告强度较低（40％），凝固时间显着增加。所得结果表明，火山灰中CaO和MgO的含量以及用作活化剂的酸浓度是影响酸活化水泥最终性能的参数。另外，非晶相的存在阻碍了反应性。根据结果​​，火山灰可被认为是用于建筑目的的磷酸活化水泥生产的前体。