Preparation and evaluation of high-fluid backfill materials from construction spoil

Abstract

With the rapid development of cities, construction spoil (CS) is gradually accumulating. Moreover, in urban construction, challenges related to heavy pollution and high cost of backfilling are common, and unsuitable backfill materials have the disadvantage of late shrinkage. Using CS, phosphogypsum (PG), and blast furnace slag (BFS) to prepare high-fluid backfill materials (HFBMs) can reduce the amount of CS and industrial solid wastes. In addition, it can save cost, reduce pollution and solve the shrinkage problem of HFBMs. In this study, the performance and mechanism of HFBMs fabricated by using CS, PG, and BFS were investigated. The environmental and economic benefits were also evaluated. The results showed that industrial solid waste was not conducive to working performance and water permeability, and the negative effect of PG was clearly observed. Compound mixing reduced the negative effects of PG and improved its mechanical properties. The HFBMs with 5% cement, 3% BFS and 2% PG exhibited the highest strength (7 d, 870 kPa; 28 d 1060 kPa). More importantly, PG and BFS can solve the problem of HFBMs shrinkage. This is because more Aft, which ran through the cracks, was formed in the system when the HFBMs were prepared with PG and BFS. Moreover, compared with the two traditional backfilling methods, HFBMs can reduce the backfilling cost by 0.66% and 62.59%, respectively. In addition, carbon emissions were reduced by 66.23% and 80.97%. Thus, the material is economical and environmentally friendly.