A comprehensive research was conducted to study the performance of a variety of stabilized geomaterials against the freeze–thaw (F–T) cycling process. Also included were unstabilized recycled materials, i.e., recycled asphalt pavements (RAP) and recycled concrete aggregates (RCA). Stabilized geomaterials used in this study included natural coarse-grained and fine-grained soils and reclaimed pavement materials (RPM). The stabilizers (binders) included self-cementitious fly ashes (i.e., class C and off-specification fly ashes). Resilient modulus ($M_r$ ) performances of geomaterials and geomaterials stabilized by binders were evaluated under a number of F–T cycles. This article also compares the F–T performances of different geomaterials including, stabilized coarse-grained versus fine-grained geomaterials, stabilized natural soils versus stabilized RPMs versus unstabilized RAP versus RCA. Additionally, the impact of fly ash type and fly ash content on F–T performance of stabilized geomaterials was also investigated. Moreover, correlations between the physicochemical properties [CaO, $\mathrm{CaO}/{\mathrm{SiO}}_2$ , $\mathrm{CaO}/{\mathrm{Al}}_2{\mathrm{O}}_3$ , $\mathrm{CaO}/({\mathrm{Al}}_2{\mathrm{O}}_3+{\mathrm{SiO}}_2)$ , $D_{60}$ , $D_{30}$ , gravel-to-sand (G/S) ratio and fines content] of these stabilized and unstabilized geomaterials and their resilient modulus were explored under F–T cycling. $M_r$ decreases (7–50%) in response to F–T cycling and then levels off in approximately 1–5 cycles. Fly ash stabilized coarse-grained geomaterials provided 5% less drop in initial $M_r$ compared to the fly ash stabilized fine-grained soils. RPMs stabilized with fly ash performed better (average reduction of 25%) against F–T cycling than the unstabilized RAP materials (average reduction of 33%) and natural fine-grained soils (average reduction of 29.5%) stabilized with fly ash. No correlations were found between the fly ash types/fly ash contents and $M_r$ performance of fly ash stabilized geomaterials under F–T cycling process. Fly ash stabilized coarse-grained geomaterials with higher $D_{60}$ , $D_{30}$ , G/S ratio, and fines content tend to lose more stiffness at higher number of F–T cycles. Such correlations could also be determined for RCA and RAP except G/S ratio. Stabilized fine-grained and coarse-grained geomaterials with fly ashes having higher $\mathrm{CaO}/{\mathrm{SiO}}_2$ , $\mathrm{CaO}/{\mathrm{Al}}_2{\mathrm{O}}_3$ , and $\mathrm{CaO}/({\mathrm{SiO}}_2+{\mathrm{Al}}_2{\mathrm{O}}_3)$ ratios experienced lower loss in $M_r$ during F–T.

Swelling, shrinking, and subsequent low strength of expansive soil poses significant damage to structures if it is considered as foundation or fill material. Recently, the use of cement has become very prevalent in stabilizing these problematic soils owing to its effectiveness. However, the swelling potential of expansive soil is not always adequately resolved by cement. The presence of sulfate salts aggravates the situation impairing the effectiveness of cement, leading to the need to reassess its performance. In this study, the effectiveness of different stabilizers was investigated in stabilizing high-plasticity soil. Two types of soil with variable sulfate content were treated with slag, Type I/II, and Type V Portland cement, and their performances were evaluated based on Atterberg limits, pH, unconfined compression, and volumetric swell tests. A total of 312 samples were prepared for 18 different soil–stabilizer blends tested after 7, 28, and 90 days of curing period. Laboratory test results indicated that strength gain performance was attenuated and swelling potential increased due to the presence of sulfate salts. Adding stabilizers improved the strength of soils by a factor of 4–10 and decreased the swelling potential to < 1%. Atterberg limits decreased initially and then slightly increased with the increase of additive dosages. Additives increased the pH up to a maximum value of 11–12, which could be used as an indicator of target stabilizer addition rate. Finally, slag improved the performance of cement significantly and has proven to be a better option for treating high sulfate expansive soils.

The use of recycled concrete aggregate (RCA) materials in highway constructions is economically viable and reduces virgin natural resource demands on the environment. To evaluate their potential use in highway construction, two different RCA materials and four virgin granular aggregate base (GAB) materials and their select mixtures were tested in the laboratory for strength, resilient modulus, permanent deformation, and durability. Laboratory water leach tests and pH-dependent leaching tests were conducted to determine the environmental suitability of the RCA materials. The leaching behavior of Ca, Cr, Cu, Fe, and Zn and the effects of pH, curing time, liquid-to-solid (L∶S) ratio, and particle size on metal leaching from the RCAs were investigated. Summary resilient moduli (SMR) of the RCAs were up to 2.6 times higher than that of the GAB materials. Their stiffness also increased when subjected to freezing and thawing cycles. Consistent trends could not be observed with percent RCA addition and st...