Rheological behavior with time dependence and fresh slurry liquidity of cemented aeolian sand backfill based on response surface method

Abstract

Slurry transportation in pipelines is the key link in the filling process. Liquidity and rheological behavior are important bases for evaluating the feasibility and stability of slurry pipeline transportation and the rheological behavior is time-dependent. Research on the performance and application of cemented aeolian sand (AS) backfill (CASB) is in the preliminary stage, and the time effect and continuous response of various factors to the rheological behavior of CASB slurry have not been studied. Here, the CASB slurry contained AS as an aggregate, fly ash (FA) as an auxiliary material, ordinary Portland cement (PO) as a cementitious material, and water. The response surface method (RSM) was adopted to analyze the influence of PO content (x1), FA–AS ratio (x2), concentration (x3), and their interaction terms (x1x2, x1x3, and x2x3) on the rheological parameters (yield stress (τ0) and viscosity coefficient (η)) of slurry at 0, 40, 80 and 120 min. Additionally, liquidity (slump flow (Sf) and bleeding rate (Br)) of fresh slurry was evaluated. The rheological parameters increased with PO content, FA–AS ratio, and concentration, except that the bleeding rate first decreased and then increased with PO content, the slump flow and bleeding rate decreased with each response factor. The interaction term, x2x3 had a significant influence on τ0 and η at each curing time and Sf and Br, x1x3 had a significant influence on the τ0 and η at 40, 80, and 120 min, and x1x2 influenced τ0 and η at 80 and 120 min significantly. An improvement in one factor promoted the strengthening of another factor. τ0 increased as a quadratic function, and η increased as a primary or quadratic function with curing time. The fitting degree between τ0, η, and curing time was > 0.9, indicating that the rheological parameters of the slurry had a strong time dependence. In conclusion, this study determined the influence and mechanisms of PO content, FA-AS rate, concentration, and their interaction terms on the rheological behavior with time dependence and fresh slurry liquidity of CASB, thereby providing theoretical and engineering guidance for CASB filling.