Basic rheological and mechanical properties of high-volume fly ash grouts

Abstract

Soil, rock and oil-well grouting require enormous amounts of cement and are therefore good examples of areas where high volumes of fly ash could replace cement partially to produce low-cost, environmentally friendly and durable grouts. This paper presents the results of the particle size distribution, three rheological properties (flow time, bleeding and setting time), and five mechanical and strain properties (compressive strength, shear bond strength, modulus of elasticity, Poisson's ratio and drying shrinkage) of high-volume fly-ash (HVFA) grouts (cement replacement by fly ash of over 55% by weight), with and without superplasticizer (SP) and/or anti-washout agent (AWA). Rheological properties are reported for eight water–cementitious materials (cement+fly ash) ratios (W/CM), ranging from 0.4 to 1.3, whereas mechanical and strain properties of hardened grouts are given at W/CM of 0.5, 0.55 and 0.65. The effects of SP and AWA on the flow time of low-W/CM grouts and the stability of high-W/CM grouts were investigated. The results indicate that the addition of fly ash in cement grouts reduces the flow time, improves stability, reduces drying shrinkage, and attains similar compressive and shear bond strengths as pure cement grouts at later ages. Moreover, when SP is used for low-W/CM grouts, the latter destabilizes, and in those cases AWA should be used.