Strength and stability of cementless concrete-like materials in air environment

The experiments carried out by checking specimen's long-term strength and examining the composition and microstructure of cured matter in air environment. It was found that strength development of specimens with only HCOSFA took place in two stages: increase during the first month and following continuous drop up to the ending of experiments (60 months). Ettringite - one of curing products played a major role in this process. It was determined that the addition of low calcium coal fly ash (LCCFA) improved strength and stability of the material. The strength curve of specimens with HCOSFA + LCCFA in atmospheric air had three sections. The first section showed evidence of the curing process and development of strength within the first month. The second section (from one to six months) showed an abrupt decrease in strength. In the third section, starting from the sixth month, strength declined at a slower rate and then stabilises from 24 up to 60 months.