ABSTRACT

This work explores the short- and long-term effects of admixtures typically used to improve durability on air lime mortars. With that purpose, two air-entraining admixtures (AEA), based on sodium alpha olefin sulfonate (AOS) and sodium dodecyl sulfate (SDS), and a water-repellent admixture (WRA) based on alkylsilicone resin were studied. The AEAs proved not to be detrimental to mechanical strength both in the short- and long-term, when used in an appropriate dosage, and reduced water intake, while improving water vapour permeability, allowing a faster drying. Comparing the AEAs, SDS led to less entrained air and, thus, to higher mechanical strength and lower porosity and pore size than AOS. In turn, the WRA substantially increased mechanical strength in the short- and long-term, despite delaying carbonation, but also increased stiffness. Water intake was reduced, as well as the mortar’s drying kinetics, which can hamper its compatibility with old masonries. With increasing dosage, both types of admixtures increased the air content, but different implications in the short-term mechanical strength of the mortars were observed: WRA led to an increase, whereas the AEAs led to a decrease in this property.

摘要

这项工作探讨了通常用于提高空气石灰砂浆耐久性的外加剂的短期和长期影响。为此，研究了两种基于 α-烯烃磺酸钠 (AOS) 和十二烷基硫酸钠 (SDS) 的引气外加剂 (AEA)，以及一种基于烷基硅树脂的防水外加剂 (WRA)。事实证明，当以适当的剂量使用时，AEA 在短期和长期都不会损害机械强度，并减少水的摄入量，同时提高水蒸气渗透性，从而加快干燥速度。与 AEA 相比，SDS 导致的夹带空气更少，因此与 AOS 相比，其机械强度更高、孔隙率和孔径更低。反过来，WRA 在短期和长期内显着增加了机械强度，尽管延迟了碳化，但也增加了刚度。减少了水的摄入量，以及砂浆的干燥动力学，这可能会妨碍其与旧砖石的相容性。随着剂量的增加，两种类型的外加剂都增加了空气含量，但观察到对砂浆的短期机械强度的不同影响：WRA 导致增加，而 AEA 导致这种性能下降。