Effect of Glass Powder Added Grout for Deep Mixing of Marginal Sand with Clay

摘要

The deep mixing has recently become a popular technique for improvement of weak or problematic soils in order to increase bearing capacity and reduce settlement. Despite various successful applications in construction projects, specifically improvement of marginal sand (i.e., loose poorly graded sand) using new materials in the viewpoint of strength development is still open for the attempt of deep mixing regarding the binder of grout, curing time and clay content. Thus, in this paper, effect of glass powder added to cement-based slurry grout in different proportions (0, 3, 6, 9% by dry weight of binder) has been experimentally investigated for deep mixing of marginal sand with various clay contents (4, 8, 20%). An experimental program has been developed for this purpose conducting the Vicat, unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests for the performances of soilcrete samples. From the testing results, it is found that: (i) The glass powder is not able to accelerate the setting times of grout, (ii) the bulk density does not significantly change with the glass powder, clay content and curing time, (iii) the most performed UCS value is obtained due to the addition of 3% glass powder at the 28-day curing for the soilcrete samples of 20% clay content of sand, while all UCS magnitudes obtained for the soilcrete samples are considered acceptable for the construction of soil-cement column, (iv) the elastic modulus correlates well with the UCS values (R 0.83) at the majority of soilcrete samples and (v) the UPV values of soilcrete samples at 28-day curing perform better due to the addition of 3% glass powder similar to the response trend of UCS, while their performances are higher due to 4% clay content in contrast to the trend of UCS. As a consequence, this study demonstrates the use of glass powder added grout to be beneficial for deep mixing of marginal sand, in which 20% clay inclusion contributes more.