Controlled low strength materials (CLSM) activated with alkaline solution: Flowability, setting time and microstructural characteristics

Conventional controlled low strength materials (CLSM) are used in rapid construction due to their self-leveling and self-consolidating properties. However, as these mixes contain low cement content, the setting time of CLSM mixes are slow, making it less desirable in most construction applications where fast setting mixes are required. In this paper, authors prepared twelve conventional CLSM mixes with different cement to cementitious material ratios to represent current practice of CLSM mixes typically used for construction. The control mixes were modified by reducing the cement content and substituting it with an equivalent quantity of fly ash activated with alkaline solution constituting of NaOH and Na2SiO3. Authors performed flowability, initial setting time and compressive strength tests on these mixes to quantify the improvements in mechanical properties of modified CLSM mixes compared to their control counterparts. Authors also performed microstructural characterization using Scanning Electron Microscopy (SEM) to identify morphological changes in modified CLSM mixes. The primary objective of this study was to observe improvement in flowability, setting time and compressive strength of conventional mixes after addition of alkaline solution. Significant improvements in flowability and over 70% reduction in setting time were observed for modified mixes compared to their conventional counterparts.