This study investigates the stress–strain response of a novel high-porosity semi-bound soft–rigid permeable pavement blend prepared using rock- and tire-derived aggregates (RDA and TDA) bonded by a polyurethane (PUR) binder. A series of unconfined compression tests were performed on 36 mix designs (with different RDA and TDA proportions, PUR contents and curing durations) to identify the variables governing the stress–strain response. The greater the TDA content, the lower the mobilized strength (UCS) and stiffness (E50), both following an exponentially-decreasing trend. Meanwhile, an increase in PUR content (i.e. increase in the number of inter-particle bonds) and/or curing duration enhanced the UCS and E50. Unlike the UCS which often achieved a stabilized state at seven days of curing, the development of stiffness extended into higher curing durations. Applying the dimensional analysis concept, a practical modeling framework was proposed and validated (using an independent database) for the UCS and E50, allowing these parameters to be simulated as a function of the blend's basic properties – that is, RDA (or TDA) content and its mean particle size, PUR content, curing duration, and dry density. The proposed models can be used with confidence for preliminary design assessments and/or semi-bound soft–rigid optimization studies.
This study examines the potential use of sodium alginate (SA) biopolymer as an environmentally sustainable agent for the stabilization of rubberized soil blends prepared using a high plasticity clay soil and tire-derived ground rubber (GR). The experimental program consisted of uniaxial compression and scanning electron microscopy (SEM) tests; the former was performed on three soil–GR blends (with GR-to-soil mass ratios of 0%, 5% and 10%) compacted (and cured for 1, 4, 7 and 14 d) employing distilled water and three SA solutions—prepared at SA-to-water (mass-to-volume) dosage ratios of 5, 10 and 15 g/L—as the compaction liquid. For any given GR content, the greater the SA dosage and/or the longer the curing duration, the higher the uniaxial compressive strength (UCS), with only minor added benefits beyond seven days of curing. This behaviour was attributed to the formation and propagation of so-called “cationic bridges” (developed as a result of a “Ca2+/Mg2+ ⟷ Na+ cation exchange/substitution” process among the clay and SA components) between adjacent clay surfaces over time, inducing flocculation of the clay particles. This clay amending mechanism was further verified by means of representative SEM images. Finally, the addition of (and content increase in) GR—which translates to partially replacing the soil clay content with GR particles and hence reducing the number of available attraction sites for the SA molecules to form additional cationic bridges—was found to moderately offset the efficiency of SA treatment.
The effects of a sulfonated oil (SO) stabiliser on the swell–shrink properties of an expansive soil were investigated through cyclic wetting–drying tests. The cyclic wetting–drying action led to the reconstruction of the soil microstructure by inducing clay particle aggregation. Accordingly, the greater the number of applied cycles, the lower the swell–shrink potential up to the fourth cycle, beyond which the swelling and shrinkage strains attained elastic equilibrium. At any given cycle, the tendency for swell–shrink reduction was in favour of the SO concentration up to 0·75%, beyond which the excess SO molecules self-associated in the form of aggregates, thereby acting as a ‘lubricant’ rather than a clay-stabilising agent. As a result of SO treatment, the accumulated axial strain progressively transitioned towards a desirable, ‘neutral’ state, with 0·75% SO exhibiting the highest resistance against cyclic wetting–drying. For any given SO concentration, the equalised void ratio–moisture content curves for wetting and drying followed the same S-shaped path, further corroborating that the swelling and shrinkage processes, on achieving elastic equilibrium, become reversible. The shrinkage and liquid limits indicated a progressive transition towards a desirable, aggregated fabric, with 0·75% SO identified as the optimum concentration.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.