Preparation and Thermodynamic Analysis of Steel Slag-Coal Based Solid Waste Controllable Low-Strength Materials

Abstract

Abstract: Cement-free controllable low strength material (CLSM) was prepared by coal gangue (CG), steel slag (SS) and fly ash (FA) under the condition of NaOH, Na₂SO₄ synergistic alkali-activation. The microstructure and phase composition of CLSM were analyzed by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) technique. The results show that there is a linear relationship between the molar ratio of Ca/(Ca+Si) and 7 d, 28 d unconfined compressive strength ratio. When the molar ratio of Ca/(Ca+Si) is greater than 0.407, the unconfined compressive strength of CLSM curing for 7 d can reach more than 70% of that of 28 d, which shows the material has early strength feature. When the fly ash is below 40% (mass fraction), the CLSM performance (flow ability) meets the requirements of ACI specification. The different mass proportions of SS/FA change the phase composition of the reaction products in the CLSM system, and the dense chimeric structures of ettringite and calcium silicate hydrate (C-S-H) gel provide the microstructure ground for mechanical properties. Finally, based on the Gibbs free energy minimization method, the amount of two crystal types of hydrated calcium silicate in the hydration products is simulated.

Key words: controlled low-strength material, alkali-activated material, C-S-H, ettringite, thermodynamics model, industrial solid waste

CLC Number:

TU528.59

LU Mingyang, PANG Laixue, YANG Da, SONG Di, ZHANG Jiali, TIAN Xiaofeng, ZHANG Yiyang. Preparation and Thermodynamic Analysis of Steel Slag-Coal Based Solid Waste Controllable Low-Strength Materials[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2022, 41(7): 2344-2351.

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