Rheological Parameters and Correlations of Ultra-Fine CEM-I Cement Grout with Ultra-Fine Fly Ash and Silica Fume

Abstract

Ultrafine CEM-I portland cement with high-purity clinker has high strength, and it is widely used in reinforcing microfractures and very small voids. Existing studies on rheological properties have been focused on composite or blended cements without exact content of each component. It is difficult to accurately obtain the influence of mineral admixture content and to guarantee grouting effectiveness. Currently, rheological parameters and correlations of ultrafine CEM-I cement composite grouting material, especially with ultrafine fly ash and silica fume, are still insufficiently studied. This study systematically investigated rheological properties of ultrafine CEM-I cement grouts (UICGs) influenced by ultrafine fly ash (UFA), silica fume (SF), and polycarboxylate superplasticizer (PCE). Results indicated that at a water-to-binder ratio ( W / B ) of 0.8–2.0, increasing UFA content (0%–40%) and decreasing SF content (0%–15%) led to progressive reductions in plastic viscosity, hysteresis area, and yield stress. Synergistic interactions of UFA, SF, and PCE effectively counteracted the adverse rheological effects of SF. When the W / B was 0.8–1.2, the rheological model of UICG with UFA (10%–40%) followed the modified-Bingham model, and the Herschel-Bulkley model was more suitable for UICGs with UFA and SF (5%–15%). For UICGs with UFA, interrelationships among plastic viscosity, yield stress, and hysteresis area generally followed modified linear trends, and SF transformed this relationship into linear trends. At a W / B of 1.0–1.5, favorable rheological performance was achieved as the amounts of UFA, SF and PCE were 30%–40%, 5%–10%, and 0.3%–0.4%, respectively. These findings have provided theoretical bases for workability and injectability design of UICGs in civil engineering.