Bílek Vlastimil, Kalina Lukáš, Novotný Radoslav, Tkacz Jakub, Pařízek Ladislav
Materials Research Centre, Faculty of Chemistry, Brno University of Technology, Brno 612 00, Czech Republic.
Materials (Basel). 2016 Jun 10;9(6):462. doi: 10.3390/ma9060462.
Significant drying shrinkage is one of the main limitations for the wider utilization of alkali-activated slag (AAS). Few previous works revealed that it is possible to reduce AAS drying shrinkage by the use of shrinkage-reducing admixtures (SRAs). However, these studies were mainly focused on SRA based on polypropylene glycol, while as it is shown in this paper, the behavior of SRA based on 2-methyl-2,4-pentanediol can be significantly different. While 0.25% and 0.50% had only a minor effect on the AAS properties, 1.0% of this SRA reduced the drying shrinkage of waterglass-activated slag mortar by more than 80%, but it greatly reduced early strengths simultaneously. This feature was further studied by isothermal calorimetry, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Calorimetric experiments showed that 1% of SRA modified the second peak of the pre-induction period and delayed the maximum of the main hydration peak by several days, which corresponds well with observed strength development as well as with the MIP and SEM results. These observations proved the certain incompatibility of SRA with the studied AAS system, because the drying shrinkage reduction was induced by the strong retardation of hydration, resulting in a coarsening of the pore structure rather than the proper function of the SRA.
显著的干燥收缩是碱激发矿渣（AAS）更广泛应用的主要限制之一。此前很少有研究表明，使用减缩剂（SRA）可以降低AAS的干燥收缩。然而，这些研究主要集中在基于聚丙二醇的SRA上，而本文表明，基于2-甲基-2,4-戊二醇的SRA的性能可能有显著差异。虽然0.25%和0.50%的添加量对AAS性能只有轻微影响，但1.0%的这种SRA使水玻璃激发矿渣砂浆的干燥收缩降低了80%以上，但同时也大大降低了早期强度。通过等温量热法、压汞法（MIP）和扫描电子显微镜（SEM）对这一特性进行了进一步研究。量热实验表明，1%的SRA改变了诱导前期的第二个峰，并将主要水化峰的最大值推迟了几天，这与观察到的强度发展以及MIP和SEM结果非常吻合。这些观察结果证明了SRA与所研究的AAS体系存在一定的不相容性，因为干燥收缩的降低是由水化的强烈延迟引起的，导致孔隙结构粗化，而不是SRA的正常作用。
