Experimental study on performance of cement-based grouts admixed with fly ash, bentonite, superplasticizer and water glass

To ensure desirable flowability, enough penetrability and less leaching of grouting materials in geotechnical engineering, the ASTM Type I Portland cement (PC), class F fly ash (FA), bentonite (B), superplasticizer (SP) and water glass were designed to improve properties of grouting materials in different aspects. The fresh-state properties i.e. flowability, spreading ability, bleeding and setting time; mechanical properties i.e. flexural strength and compressive strength; and microstructures of the cement-based grouts were investigated. The water/solid (W/S) ratio is selected as 1.0, the amounts of FA, bentonite and SP by mass of PC were 0–40%, 0–15% and 0.7%, respectively. The volume ratios of cement-based suspensions and water glass were selected as 1:1, 2:1 and 3:1. The results show that the FA and 0.7% SP enhance the flowability and spreading ability of fresh grouts, and the bentonite can enhance the stability. The effects of various FA, B, SP and water glass contents on flexural strengths of grouts are different. The class F FA, B and 0.7% SP reduce the compressive strength of hardened grouts. The performance of cement-based grouts with 20–30% class F FA, 0–5% bentonite, 0.7% SP and volume ratios of 2:1–3:1 can satisfy the requirements of high performance, environmental friendliness and low costs in geotechnical and underground engineering.