Experimental Study on the Synergistic Solidification of Soft Soil with Ceramic Powder–Slag–Phosphorus Slag

Abstract

The bearing capacity of silt soft soil is poor, making it difficult for it to be used as a subgrade material in foundation engineering, and the use of traditional Portland cement curing agents causes environmental pollution. In this study, a new soft soil curing agent, CSP (ceramic powder–slag–phosphorus slag), was prepared using ceramic powder, slag, and phosphorus slag. The unconfined compressive strength of 7-day was determined via an orthogonal test, and the optimal ratio of the curing agent was determined. The effects of the initial water content, curing agent content, admixture type, and admixture content on the mechanical properties of solidified soil were investigated via a uniaxial compression test. The microstructure characteristics of the solidified soil were analyzed via XRD and SEM-EDS, and the mechanism by which ceramic powder–slag–phosphorus slag acted as a curing agent to increase the strength of the soft soil was explored. The results show that the optimal ratio of the curing agent for the inorganic binder is ceramic powder/slag/phosphorus slag = 3:2:1, the best water glass modulus is 1 mold, the best water glass content is 26%, and the 7-day compressive strength can reach 2.382 MPa; the strength of the solidified soil decreases with an increase in the water content and increases with an increase in the curing agent content. When the water content is 35% and the curing agent content is 14%, the strength of the solidified soil can meet the requirements of relevant specifications. When the content of triisopropanolamine was 2.0% and 1.5%, the compressive strength of the 7-day and 28-day solidified soil specimens increased most significantly. The ceramic powder–slag–phosphorus slag can promote the formation of aggregates and amorphous hydration products (C-S-H, C-A-H), be distributed on the surface of the soil and fill the pores, and enhance the cementation between the particles, improving the compactness of the soil structure. In terms of the macroscopic performance, the mechanical properties of the solidified soil were significantly improved. Therefore, CSP curing agents can be promoted and applied as green, economical, environmentally friendly, and low-carbon curing materials in soft soil roadbed engineering.

The Design of a Novel Alkali-Activated Binder for Solidifying Silty Soft Clay and the Study of Its Solidification Mechanism

“…The average 7 d UCS results of the SGP-solidified soil are shown in Table 5. Referring to the literature [2,3,39], the range analysis method was used to analyze the data in Table 5 to determine the optimal level of each factor and the optimal combination. The formula for calculating the range is "R j = [max (K j1 , K j2 , K j3 ) − min (K j1 , K j2 , K j3 )]/3".…”

“…The enhancement of PVA was due to its hydrolysis of aluminum hydroxyl complexes with large molecular weight and high charge that can play the role of electrical neutralization and adsorption bridging, strong adsorption and complexation of ions in solution, especially SiO 3 2− , which promoted the continued dissolution of the mineral phase components of GBFS and PS [50][51][52]. The incorporation of Na 2 SO 4 led to a high Na + concentration in the SGP-solidified soil, and the thickness of the soil particle bilayer increased after a large amount of Na + was adsorbed on the surface of negatively charged soil particles [2]. The adhesion between the soil particles was weakened, which led to the microstructure of the SGP-solidified soil becoming loose.…”

“…Riverside silty soft clay (SC) has difficulty satisfying construction requirements due to its high water content, relatively large pores, high compressibility and poor bearing capacity [1][2][3]. Therefore, it is particularly important to solidify SC quickly and efficiently so as to improve these properties [4,5].…”