The increase in CO2 emission during Portland cement manufacturing has motivated studies on new binder systems. The production of alternative cements with less environmental impact (zero clinker) has been gaining increasing interest, mainly because green cements emit smaller amounts of CO2. One of these binders, the geopolymers, are obtained from the alkaline activation of materials rich in silica and alumina, being binders with reduced environmental impact. Therefore, the aim of this work was to study the structural (by DSC and FTIR) and compressive strength evolution of a reference, stoichiometric metakaolin by alkaline activation with Na + ions at 28 and 90 days. The effect of sodium ion concentration at room temperature during geopolymerization was observed. A pure, stoichiometric kaolin and the derived metakaolin calcined in a rotary kiln at 800 ˚C were characterized by XRF, XRD, DSC/TG and PSD. Geopolymeric pastes activated with NaOH and Na2SiO3 were made using mixture design. The pastes were characterized by DSC, FTIR in ATR mode and axial compression strength at 28 and 90 days. The DSC analysis showed that the main reactions occur up to 180 min from the beginning of the preparation of the pastes. The main bands identified by FTIR are from the Si-O-T bond and water contained in the pastes. The index of axial compressive strength shows that the geopolymer pastes reached, on average, 90 % of the final strength in up to 14 days. The use of a metakaolin without impurities for SiO2/Al2O3 ratios close to 1.5 resulted in geopolymers with 85 MPa of compressive strength after 28 days of curing.

中文翻译：

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Na+ 碱性活化对纯偏高岭土在室温下地聚合的影响


波特兰水泥制造过程中二氧化碳排放量的增加促使人们研究新的粘结剂系统。生产对环境影响较小的替代水泥（零熟料）越来越受到关注，这主要是因为绿色水泥排放的二氧化碳量较少。其中一种粘合剂，即地质聚合物，是通过对富含二氧化硅和氧化铝的材料进行碱性活化而获得的，是减少对环境影响的粘合剂。因此，这项工作的目的是研究参考化学计量偏高岭土在 28 天和 90 天时通过 Na + 离子的碱性活化的结构（通过 DSC 和 FTIR）和抗压强度演变。观察了地聚合过程中室温下钠离子浓度的影响。采用 XRF、XRD、DSC/TG 和 PSD 对在 800 °C 回转窑中煅烧的纯化学计量高岭土及其衍生的偏高岭土进行表征。使用 NaOH 和 Na2SiO3 活化的地聚合物浆料采用混合物设计制成。通过 DSC 、 ATR 模式下的 FTIR 和 28 和 90 天的轴向压缩强度对浆料进行了表征。DSC 分析表明，主要反应发生在糊剂制备开始后长达 180 分钟。FTIR 鉴定的主要条带来自 Si-O-T 键和糊状物中所含的水。轴向抗压强度指数显示，地质聚合物浆料平均在 14 天内达到最终强度的 90%。使用不含杂质的偏高岭土，使 SiO2/Al2O3 比率接近 1.5，固化 28 天后，地聚合物的抗压强度为 85 MPa。