Influence of calcium and sodium nitrate on the strength and reaction products of the CaO-activated GGBFS system

• Published in: Construction & building materials Vol. 215; pp. 839 - 848
• Main Authors: Yum, Woo Sung, Suh, Jung-Il, Sim, Sungwon, Yoon, Seyoon, Jun, Yubin, Oh, Jae Eun
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 10.08.2019
• Subjects: Calcium nitrate; CaO-activation; Cementless binder; GGBFS; Sodium nitrate; Cementless binder; CaO-activation; Calcium nitrate; GGBFS; Sodium nitrate
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2019.04.240

•The influence of Ca(NO3)2 and NaNO3 on the CaO-activated GGBFS was investigated.•Both salts notably increased early strengths by forming more C-S-H.•NaNO3 increased pH while Ca(NO3)2 supplied additional Ca ions at early days.•Ca(NO3)2 continued increasing strength until 28 days while NaNO3 did not.•At 28 days of curing, the use of NaNO3 reduced C-S-H unlike that of Ca(NO3)2. The influence of the added nitrate salts (Ca(NO3)2 and NaNO3) on the CaO-activated ground granulated blast-furnace slag (GGBFS) system was investigated. Both salts significantly increased the early strength of the binder, and the Ca(NO3)2 maintained this tendency until 28 days of curing, whereas NaNO3 did not. At early days, the NaNO3 likely increased pH of samples, resulting in more dissolving GGBFS and formation of C-S-H, while the Ca(NO3)2 slightly decreased pH due to the common ion effect, but because the Ca(NO3)2 supplied additional Ca ions, it also increased the strength. At 28 days, the NaNO3 clearly induced the reduction in C-S-H, which was not the case for the Ca(NO3)2 samples. In addition, the pore size distribution was also significantly dependent on the cation type of nitrate salts.