[1015] EFFECT OF LOW CURING TEMPERATURE AT EARLY AGES ON EXPANSION BEHAVIOR OF EXPANSIVE MORTAR
Keywords:expansive additive、ettringite、calcium hydroxide、low curing temperature、cracking、膨張材、エトリンガイト、水酸化ナトリウム、低温、ひび割れ
This paper investigates the effect of low curing temperatures on the expansion properties of nonexpansive and expansive mortar at early ages, considering the different curing conditions and change in curing temperature at later ages. The experiment included visual observation, expansion strain, compressive strength, thermogravimetric differential thermal analysis, quantitative X-ray diffraction, Rietveld analysis, and a scanning electron microscopy test. The crack appeared in the surface of expansive mortar that was first cured at 5℃ for 14 days, then cured at 20℃ and 40℃ until 36 and 18 days, respectively. However, if enough water is supplied, cracks will not appear even after 14 days of curing at low temperatures and then increasing curing temperatures to 20℃ and 40℃. The higher thetemperature, the faster cracks appear. The test results also revealed that after expansive mortar was cured in the air at a low curing temperature, there was still an amount of expansive additive in the mortar that had not reacted, which explains the appearance of cracks.