Treatment of weak subgrade materials with cement and hydraulic road binder (HRB)

Portland cement has been widely used to improve the engineering performance of pavement materials. On the other hand, hydraulic road binder (HRB) is now a frequent option in Europe for the treatment of road base, and subbase, and earthworks. HRB contains high amounts of supplementary cementitious materials (SCMs) and by-products. HRB has the potential of reducing the amount of cement clinker thereby making it more cost effective and environmentally friendly. Moreover, the HRB treated materials also have improved workability due to its slower setting and hardening. The primary objective of this study is to investigate the chemical and physical properties of organic clayey subgrade materials treated by different HRBs. The paper first introduced a brief background for the development of hydraulic binders and their current applications for soil stabilisation. Then, it presented the results of laboratory testing for cement- and HRB- treated subgrade soils. Test results indicated that all the three subgrade soils named Dresden, Blenheim, and Niagara were fine-grained soils with substantial silt and cvnlay particles and organic matters. Cement and HRBs significantly improved soil’s engineering properties. The improvement included the change of soil’s environment from acidic to alkaline and prevent development of organics, the significant improved strength, durability, and resilient modulus. In addition, HRB-treated subgrade soils had lower sulfate included than cement-treated one that could reduce the risk of sulfate-induced problems. Among all HRB-treated materials, with abundant curing, the subgrade soils treated with the HRB composed of GUL and slag (HRB-4LS) had the highest UCS values, followed by the soil treated with HRB-4LF (composed of GUL and fly ash), and HRB-3S (GU and GGBFS). It should be noted as well that the soil types played an important role in the treatment. Soils with high plasticity, high organic matters had lower strength and modulus than less plastic and organic soils. Lastly, the differences of the soils could be visualised from the environmental scanning electron microscopy (ESEM) images. This research contributed to a tentative treatment of weak subgrade soil with locally blended HRBs. The results also proposed a potential solution for the treatment of weak subgrade soils at the top of the natural subgrade.