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.

Geosynthetic materials (i.e., geogrids, geotextiles and other geocomposites) act as an interlayer system and are widely used in construction applications. In pavement structures, geosynthetic layers provide potential benefits such as reinforcement, reflective cracking mitigation, increased fatigue life, and improved drainage and filtering. However, few studies have addressed the installation and construction practices of geosynthetics in pavements. Furthermore, the study of geosynthetics and their contribution during construction are limited. In this paper, a full-scale field study was conducted and three trial sections were constructed; two types of geosynthetics, a fibreglass geogrid and a geogrid composite, were installed in the asphalt binder course and at the interface between the subgrade and base layer, respectively, to be compared with a control section without geosynthetic reinforcement. Trial sections were instrumented to monitor the pressure applied on the subgrade, the strain in the base lift of the asphalt binder course, the temperature, and the moisture within the pavement structure during construction. In addition, post-construction field testing was performed to measure the stiffness of the pavements after construction. The results indicated that geosynthetic-reinforced pavements can maintain pavement resilience during construction and significantly mitigate the disturbances caused by construction activities. The geogrid embedded in the asphalt layer was demonstrated to reduce the pressure at the subgrade caused by paving equipment by 70% compared with the control section, while simultaneously reducing the longitudinal and transverse strain at the bottom of the asphalt layer by 54% and 99%. Observations from the geogrid composite test section also demonstrate the potential to minimize the impacts of future freeze–thaw at the subgrade due to the improved drainage and indirect insulation effect.

The capillary rising is one of the most common phenomena in fine-grained soils. However, research is limited for capillary actions in cementitiously treated engineered soils. In this study, a soil column test was performed for the free capillary rising in compacted loess and modified loess samples. Moisture content of compacted soil samples was measured and analyzed to determine capillary height and rising rate. Results indicated that there was a considerable capillary rising in loess and lime-modified loess, while the capillary rising in cement-treated loess was significantly restrained. Current models are not appropriate for the rate and height predictions of capillary rising in cementitiously treated loess, especially in early ages. Therefore, a logarithmic form correlation was suggested and validated. In addition, salt migration effect and microscopic properties of soils after capillary rising were evaluated. Overall, the paper presented an experimental study and prediction on the capillary rising behavior of treated and recompacted engineered loess.

Permanent deformation, or rutting, is one of several critical distresses in flexible pavements. This paper introduced a novel experimental method, a penetration test, for asphalt mixtures to quantify the effects of glass fibre geogrids embedded in asphalt under repeated loading. It was found that the evolution of permanent deformation (ε_p) and its strain rate have three clearly identifiable stages. It was also observed that the presence of the geogrid increased the flow number and the number of cycles to failure significantly compared to control samples. Some of the current ε_p fitting models were found to be valid for deformation prediction under penetration. In addition, a new simple FN calculation method was also proposed based on strain rate and it showed consistent results. In particular, geogrid type “Grid10”, which has smaller aperture size (12.7 mm) had slightly better reinforcement performance regarding the rutting resistance due to its larger contact area. Overall, the test and data analysis method presented in this study could be an important reference for future investigations on geosynthetic-reinforced pavement materials.

Hydraulic road binders (HRBs) are specially designed materials for pavement stabilisation. The objective of this research was to investigate the properties of several laboratory-blended HRBs constituted of reduced cement clinker content and different types of Supplementary Cementitious Materials (SCMs). Formulated HRBs were characterised chemically and physically in the form of paste and mortar. Laboratory results showed a distinct reduction of hydration temperature and drying shrinkage in HRBs. In addition, HRBs had different contents of hydration products compared to Portland cement. Moreover, HRB mortars containing up to 50% of slag could have similar strength compared to GU and GUL at 28 curing days and onwards. It was also indicated that slag had superior strength development effect compared to the other two SCMs. Furthermore, a statistical prediction was conducted on compressive and flexural strength of HRB mixes. Finally, a framework of HRB optimisation was proposed.