LAUSR

One of the most important technological problems associated with alkali-activated materials (AAM) is large shrinkage. A possible solution to decrease the extensive drying shrinkage of these materials is the use of shrinkage-reducing admixtures (SRAs). The promising group of SRAs, from the perspective of using in AAMs, are amino alcohols. However, the efficiency of reducing the drying shrinkage strongly depends on their chemical structure. Hence, the study is focused on the molecular architecture of amino alcohol surfactants and its relation to the affected properties of alkali-activated blast-furnace slag systems. Selected amino alcohols were tested in terms of the ability to reduce the surface tension of pore solution as well as to influence the drying shrinkage, hydration mechanism and mechanical properties of AAMs. The study confirms that the length and branching of the alkyl chain linked to the amino group play the key role in SRA efficiency. Amino alcohol surfactants with a high-carbon alkyl chain decreased dramatically both the surface tension and the drying shrinkage, but simultaneously negatively affected the process of alkali activation, resulting in a deterioration of the mechanical properties. Conversely, the addition of 0.5 w/ % of the surfactants with a low molecular weight, such as 2-(Methylamino)ethanol, showed a slight improvement of the compressive strength after 7 d and 28 d, and at the same time reduced the drying shrinkage by 30 % compared to the reference sample.