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This article discusses the effects of glass powder (GP) replacements and sodium hydroxide (NaOH) molarity on the rheological, fresh, mechanical and microstructure characteristics of slag-based mechanochemical geopolymer (MG) grout. A conventionally activated geopolymer grout and an ordinary Portland cement (OPC) grout were also investigated for comparison. Four glass powder replacement ratios were used (0%, 10%, 20% and 30% by the total precursor weight) to prepare slag-based mechanochemical geopolymer at three NaOH concentrations (1.25, 2.5 and 3.75 molars). The experimental results showed that the rheological behaviour of MG grouts was considerably reduced, whereas the setting time and the bleeding capacity value increased when slag was substituted with 0%–30% GP. However, after 28 days, the unconfined compressive strength (UCS) improved by 2%–13% when 10%–20% GP was used as a slag replacement, then dropped by 4% when 30% GP was substituted. The results confirmed that both geopolymer grouts irrespective of the activation method had shorter setting time and more stable bleeding capacity than OPC grout. The results also revealed that the UCS of geopolymer grout is enhanced by 18% when the source materials are activated by the mechanochemical method compared to the conventional activation of geopolymer grout. The microstructure results revealed that the activation method had a considerable effect on the microstructure of geopolymer grout because the ball milling process increased the surface area and reduced the particle size of slag compared to conventionally activated geopolymer grout. [ABSTRACT FROM AUTHOR]

In recent years, the deep mixing technique that utilizes cement-based grout mixtures has become a popular approach, particularly for the enhancement of soft soils. Despite the advantages of deep mixing technique in numerous construction applications, the effort given for this technique still needs to be extended using new material as additive. Thus, this study investigates the use of cement-based grout combined with glass powder to enhance the clay soil via deep mixing technique. An experimental program has been conducted including grout mixtures at different replacements of glass powder (0%, 3%, 6% and 9% by dry weight of binder) mixed with clay having different water contents (36%, 31% and 21%). The Vicat, unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests have been carried for analysing performances of mixtures. The results indicate that the setting times of the mixture pastes increase, while the bulk densities of the soilcrete samples do not significantly change with the replacement of glass powder. Moreover, due to the use of glass powder, both the UCS and UPV increase alongside decreasing water content as well as increasing curing time. Test results imply that, owing to the replacement of glass powder, all UCS values of the soilcrete samples are applicable for the purpose of deep mixing. However, the replacement of glass powder by 3% produces a more favorable UCS response. Strong correlations exist for the UCS versus elastic modulus (R ⩾ 0.84) as well as for the UCS versus UPV (R ⩾ 0.82), which practically could be useful for the strength predictions of soil-cement columns. Consequently, the use of cement-based grout with the glass powder replacement could provide a new insight into the deep mixing technique for the treatment of clay. Moreover, the employment of glass powder as a waste material could also benefit the environment and construction costs. [ABSTRACT FROM AUTHOR]