Effects of pre-curing treatment and chemical accelerators on Portland cement mortars at low temperature (5 °C). (20th April 2020)

• Record Type: Journal Article
• Authors: Liu, Zhuangzhuang; Lou, Baowen; Barbieri, Diego Maria; Sha, Aimin; Ye, Tong; Li, Yanlong
• Is Part Of: Construction & building materials. Volume 240(2020)
• Publication Date: 2020-04-20
• Subjects: Cement mortar -- Low temperature -- Accelerators -- Pre-curing treatment -- Cold weather concreting -- Interval time; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2019.117893
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Cement mortars were curred at a low temperature (5°C). The influences of pre-curing treatment and chemical accelerators on the Portland cement mortars were observed. Mechanical behaviors, setting time, microstructures, and released heat of hydration were measured. The importance of time interval between the initial and the final setting was confirmed. Abstract: Artificial heating and chemical admixtures are widespread solutions to keep and improve the early strength of cement concretes in cold weather. The research analyzed the performance of cement mortar at low temperature (5 °C) in combination with pre-curing treatment and the use of chemical accelerators, e.g., calcium chloride (CaCl2 ), sodium nitrite (NaNO2 ), potassium carbonate (K2 CO3 ), and sodium sulfate (Na2 SO4 ). The investigation comprised the mechanical behavior, setting time, released heat of hydration, and microstructures. The standard curing pretreatment at 20 °C, differently from curing at 5 °C, engendered a reduction in the mechanical strength of both untreated and chemically treated cement mortar samples. Although all chemicals accelerated the reactions of hydration, the achieved compressive strengths of the mortars were different. The specimens treated with calcium chloride (CaCl2 ) reached the highest compressive strength, followed by sodium nitrite (NaNO2 ) and sodium sulfate (Na2 SO4 ). Specimens containing potassium carbonate (K2 CO3 ) attained the lowest compressive strength. Further analyses highlighted the importance of the time interval between initial and final setting: a shorter time interval led to lower mechanical strength due to more cracks in the cement matrix.