Abstract
In the present research, industrial wastes, e.g., fly ash (FA), lithium slag (LS), ground granulated blast furnace slag (GGBS), and red mud (RM) were utilized to prepare the magnesium phosphate cement (MPC)-based grouting material by a two-component grouting method. Successive additions of GGBS within 40% (C1–C5) led to reduced fluidity, increased pH value, and shortened setting time. The compressive strength increased first and then decreased. The strength value reached the maximum at a 20% dosage (C3). Increasing the content of RM from 0% (C4) to 25% (C9) resulted in prolonged setting time and an increased pH value. The fluidity and compressive strength increased first and then decreased. The fluidity and strength value became the highest at a 15% additive ratio (C7). GGBS can significantly improve the strength and water resistance at 7 days and 28 days by the potential hydraulic property. RM has a smaller particle size than MP, making the microstructure denser by the pore-filling effect. Thus, the drying shrinkage was increased after adding GGBS, while it was decreased when incorporating RM. The MPC-based grouting material has a controllable short setting of 3–21 min, self-leveling fluidity above 200 mm, a near-neutral pH value, high early strength (1 day compressive strength of 5 MPa), minor drying shrinkage (one-tenth of OPC), and excellent water resistance (over 85%), which is much superior to traditional grouting materials.
Highlights
Water inrush is one of the geological disasters that frequently happens during the construction of underground engineering [1]
In this formula, Wrn is the water resistance of the Magnesium phosphate cement (MPC)-based grouting material at n days, fn is the compressive strength of the hardened sample cured in water for n days, and Fn is the compressive strength of the hardened sample cured in air for n days
During the period from 7 days to 28 days, the water resistance of the samples mixed with ground granulated blast furnace slag (GGBS) significantly improved. e group containing 20% GGBS (C3) increased from 71.4% to 86.8%
Summary
Water inrush is one of the geological disasters that frequently happens during the construction of underground engineering [1]. Magnesium phosphate cement (MPC), as a kind of chemically bonded phosphate ceramics, has the advantages of fast setting, super early strength, minor shrinkage, good volume stability, and low environmental pollution (the slurry pH is close to neutral) [14, 15]. It is widely used in engineering reinforcement [16, 17]. In the present research, industrial wastes (FA, LS, GGBS, and RM) were utilized to prepare the MPC-based grouting material by a two-component grouting method. E research results enrich the knowledge about large-volume industrial waste-based MPC grouting material, effectively solving the water inrush problem in underground engineering constructions and significantly utilizing industrial solid waste [3, 26] The compressive strength, water resistance, and drying shrinkage of hardened samples were measured. e microscopic tests: X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP), were applied to investigate the hydration products and microstructure. e research results enrich the knowledge about large-volume industrial waste-based MPC grouting material, effectively solving the water inrush problem in underground engineering constructions and significantly utilizing industrial solid waste [3, 26]
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