The preparation of nano calcium carbonate and calcium silicate hardening accelerator from marble waste by nitric acid treatment and study of early strength effect of calcium silicate on C30 concrete. (November 2020)

• Record Type: Journal Article
• Authors: Yang, Hong; Yan, Yun; Hu, Zhihua
• Is Part Of: Journal of building engineering. Volume 32(2021)
• Publication Date: 2020-11
• Subjects: Marble waste -- Nano calcium carbonate -- Nitric acid treatment -- Hardening accelerator -- Early strength effect; Building -- Periodicals; 690.05
• DOI: 10.1016/j.jobe.2020.101507
• Languages: English
• ISSNs: 2352-7102

Abstract

Abstract: Accumulation of marble waste increases pressure on the environment and human healthcare. In this work, it is focused that square-shaped nano calcium carbonate was prepared from marble polishing waste by nitric acid treatment and the effects of various preparation parameters, such as the concentration of nitric acid, reaction time and temperature on the morphology and size of nano calcium carbonate were investigated. Meanwhile, hardening accelerator was synthesized using Ca(NO3 )2 liquid waste generated the process of preparing nano calcium carbonate as the source of calcium and Na2 SiO3 as the source of silicon. Entire technological process is free of pollutants and will not cause secondary pollution to environment and it is eco-friendly and sustainable. Nano calcium carbonate can be achieved with an average particle size of approximately 70 nm and homogeneous under nitric acid concentration of 1.6 mol/l, reaction temperature at 55 °C, reaction time for 4 h and sodium dodecyl benzene sulfonate(SDBS) as the dispersant. Additionally, when the prepared hardening accelerator is applied to C30 concrete with content of 3%, improvement value of compressive strength of concrete are 89.3%, 21.5% and 17.3% curing 1d, 3d and 28d, respectively, and it will not cause the decline of compressive strength in the later stage. Highlights: Nano calcium carbonate was obtained by nitric acid treatment using marble waste as raw material and nitric acid as solvent. Chlorine-free hardening accelerator for concrete can be prepared using Ca(NO3 )2 liquid waste as the calcium source and Na2 SiO3 as silicium source. Hardening accelerator was applied to C30 concrete, it has a significant effect on improving the early compressive strength of concrete. Marble polishing waste was effectively utilized and environmental and economic benefits can be obtained.