High-volume ultrafine fly ash-cement slurry mechanical properties and strength development model establishment

This paper, orthogonal experiments were designed to study the changes of water separation rate, concretion rate and uniaxial compressive strength (UCS) without side pressure of ultrafine fly ash (UFA)-cement slurry with high volume. Low field-nuclear magnetic resonance (NMR) was used to characterize the pore structure characteristics. The relationship between UCS without lateral compression and pore characteristics, FA content and water-cement ratio of specimens was studied. The results show that the watercement ratio has the greatest influence on the water separation rate and the concretion rate of the specimen, and the FA content has the greatest influence on the UCS of the specimen, and the changing trend was polynomial function. With the increase of FA content, the UCS without side compression of specimens decreases, and the elastic modulus decreases, but the ductility deformation is improved. Based on Feret classical equation and maturity formula, a model is proposed to predict the strength of FA-cement, where just three variables (i.e., the FA content, the water-cement ratio and the curing time) can characterize this complex model. The optimal ratio of FA-cement slurry is optimized according to the actual demand of mine. At present, this method has been widely applied in the mine and achieved good results. (C) 2021 Elsevier Ltd. All rights reserved.