Vasanelli Emilia, Calò Silvia, Cascardi Alessio, Aiello Maria Antonietta
CNR-ISPC (National Research Council-Institute of Heritage Science), University Campus, Prov. le Lecce Monteroni, 73100 Lecce, Italy.
Department of Innovation Engineering, University of Salento, University Campus, Prov. le Lecce Monteroni, 73100 Lecce, Italy.
Materials (Basel). 2024 Apr 14;17(8):1798. doi: 10.3390/ma17081798.
Geopolymers have been proposed as a green alternative to Portland cement with lowered carbon footprints. In this work, a geopolymeric mortar obtained using waste materials is studied. Fly ash, a waste generated by coal combustion, is used as one of the precursors, and waste glass as lightweight aggregates (LWAs) to improve the thermal performance of the mortar. The experimental study investigates the effect of varying the alkali activating solution (AAS) amount on the workability, compressive strength, and thermal conductivity of the mortar. Indeed, AAS represents the most expensive component in geopolymer production and is the highest contributor to the environmental footprint of these materials. This research starts by observing that LWA absorbs part of the activating solution during mixing, suggesting that only a portion of the solution effectively causes the geopolymerization reactions, the remaining part wetting the aggregates. Three mixes were investigated to clarify these aspects: a reference mix with a solution content calibrated to have a plastic consistency and two others with the activating solution reduced by the amount absorbed by aggregates. In these cases, the reduced workability was solved by adding the aggregates in a saturated surface dry state in one mix and free water in the other. The experimental results evidenced that free water addiction in place of a certain amount of the solution may be an efficient way to improve thermal performance without compromising the resistance of the mortar. The maximum compressive strength reached by the mortars was about 10 MPa at 48 days, a value in line with those of repair mortars. Another finding of the experimental research is that UPV was used to follow the curing stages of materials. Indeed, the instrument was sensitive to microstructural changes in the mortars with time. The field of reference of the research is the rehabilitation of existing buildings, as the geopolymeric mortars were designed for thermal and structural retrofitting.
地质聚合物已被提议作为一种绿色替代品，用于替代碳足迹较低的波特兰水泥。在这项工作中，对一种使用废料制备的地质聚合物砂浆进行了研究。粉煤灰是煤炭燃烧产生的废料，用作前驱体之一，废玻璃用作轻骨料（LWAs）以提高砂浆的热性能。实验研究考察了改变碱激发溶液（AAS）用量对砂浆工作性、抗压强度和导热系数的影响。事实上，AAS是地质聚合物生产中最昂贵的成分，也是这些材料环境足迹的最大贡献者。本研究首先观察到，轻骨料在搅拌过程中会吸收部分激发溶液，这表明只有一部分溶液有效地引发了地质聚合反应，其余部分则润湿了骨料。研究了三种配合比以阐明这些方面：一种参考配合比，其溶液含量经校准以具有塑性稠度，另外两种配合比的激发溶液减少了骨料吸收的量。在这些情况下，通过在一种配合比中加入饱和面干状态的骨料和在另一种配合比中加入自由水来解决工作性降低的问题。实验结果表明，用自由水替代一定量的溶液可能是一种在不损害砂浆强度的情况下提高热性能的有效方法。砂浆在48天时达到的最大抗压强度约为10MPa，该值与修补砂浆的抗压强度值一致。实验研究的另一个发现是，超声脉冲速度（UPV）被用于跟踪材料的固化阶段。事实上，该仪器对砂浆微观结构随时间的变化很敏感。该研究的参考领域是现有建筑物的修复，因为地质聚合物砂浆是为热和结构改造而设计的。
