This study investigated the curing mechanism of foamed asphalt mixes. Various laboratory strength and stiffness tests were performed on mixes with various asphalt and portland cement contents, and the specimens were subjected to two relatively extreme curing conditions. It was found that portland cement enhances certain properties of foamed asphalt mixes by strengthening the mineral filler phase, with the curing mechanism similar to that of typical cement treated materials. The curing mechanism of foamed asphalt mastic is primarily related to water evaporation. The bonding between asphalt mastic and aggregate particles cannot fully develop until most of the water retained at the interface evaporates. This bonding, once formed, is only partially damaged by reintroduced water. This proposed mechanism was supported by observations of fracture faces on tested specimens. A long-term curing study confirmed the validity of this mechanism regardless of the curing duration. Standard curing procedures are proposed for use in project level mix design and evaluation based on the findings.

On-road vehicle use is responsible for about a quarter of US annual greenhouse gas (GHG) emissions. Changes in vehicles, travel behavior and fuel are likely required to meet long-term climate change mitigation goals, but may require a long time horizon to deploy. This research examines a near-term opportunity: management of pavement network roughness. Maintenance and rehabilitation treatments can make pavements smoother and reduce vehicle rolling resistance. However, these treatments require material production and equipment operation, thus requiring a life cycle perspective for benefits analysis. They must also be considered in terms of their cost-effectiveness in comparison with other alternatives for affecting climate change. This letter describes a life cycle approach to assess changes in total GHG (measured in CO₂-e) emissions from strategic management of highway pavement roughness. Roughness values for triggering treatments are developed to minimize GHG considering both treatment and use phase vehicle emission. With optimal triggering for GHG minimization, annualized reductions on the California state highway network over a 10-year analysis period are calculated to be 0.82, 0.57 and 1.38 million metric tons compared with historical trigger values, recently implemented values and no strategic intervention (reactive maintenance), respectively. Abatement costs calculated using $/metric-ton CO₂-e are higher than those reported for other transportation sector abatement measures, however, without considering all benefits associated with pavement smoothness, such as vehicle life and maintenance, or the time needed for deployment.

This paper reviews various emerging alternative SCMs derived from minerals and biomass sources, industrial byproducts, and underutilized waste streams. The paper compiles and evaluates physicochemical properties, reaction mechanisms in cementitious systems, resource availability, supply chain dynamics, technology readiness, the impact on concrete performance, and environmental and cost factors for each candidate SCM. Specifically, the review examines wood ash from bioenergy plants, volcanic and sedimentary natural pozzolans, and construction and demolition waste. This includes recycled concrete fines, asphalt plants’ rock dust (baghouse fines), aggregate production fines, and post-consumer waste, particularly municipal solid waste incinerator ash and wastewater sludge ash. Additionally, the paper explores innovative additives such as cellulose and chitin nanomaterials and calcium–silicate–hydrate nanoseeds to address challenges of slower strength development and rheological changes. The key contribution of this review is a multifactor framework for assessing alternative SCMs, emphasizing availability, supply chain, market readiness, and environmental performance, combined with an engineering performance review.

This paper summarizes the results of numerous simulations to assess the hydraulic performance of fully permeable highway shoulder retrofits designed to capture all the rainfall runoff falling onto conventional highway surface pavements. The simulations were performed using commercially available HYDRUS software that uses unsaturated flow theory. The hydraulic properties of subgrade soil and pavement materials were measured in the laboratory and used as input for numerical simulation. The simulations were performed for three rainfall regions in California representing high, medium, and low annual rainfall events. The simulations were performed based on 24-h actual rainfall data using 2-, 50-, and 100-year storm recurrences to determine the critical thickness of aggregate needed to capture the highway runoff volume without surface ponding and/or overflow. Sensitivity analyses were performed to evaluate the influence of material, hydrologic, and geometric factors on the critical aggregate base thickness. Results indicated that an aggregate depth of about 1.5 m was adequate for most California areas with two-lane highways. Sensitivity analyses also revealed that the saturated hydraulic conductivity ($K_s$ ) of the subgrade soil is the most important parameter to be considered in the design of fully permeable pavements, with a minimum effective allowable value of approximately ${10}^{-5}\mathrm{cm}/\mathrm{s}$ .

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