The ever-increasing volume of construction and demolition waste and the growing demand for sustainable construction practices have spurred extensive research on incorporating Recycled Concrete Aggregates (RCA) in various construction applications. Among these, the use of RCA in Thin Concrete Overlay Slurry (TCOS) for road repairs has emerged as a promising solution to address both environmental concerns and the need for cost-effective infrastructure maintenance. The first segment focuses on the properties and characteristics of RCA, comparing them with natural aggregates and the importance of the criteria for TCOS in terms of mechanical properties, durability, crack prevention, and skid resistance. The key environmental advantages identified are the reduction of construction waste, conservation of natural resources, and energy savings during production. Cost savings on aggregates, reduced waste disposal costs, and lower transportation expenses are highlighted as key economic advantages. The paper emphasizes how RCA may be used in TCOS for sustainable road repairs. A viable sustainable method for building roads has been demonstrated by the integration of RCA in TCOS. However, introducing RCA may lower the TCOS compressive strength. Research suggested that a lower water-to-cement ratio of 30% to 35% may increase the compressive strength of TCOS-RCA. Likewise, the blending of fibers as reinforcement might increase the wear resistance and decrease surface spalling. Further, the flexural strength and crack resistance of TCOS can be enhanced by combining fibers.

Fiber-reinforced rigid pavement offers a viable option for sustainable concrete development due to its superior mechanical properties, notably enhanced durability and crack resistance. Nonetheless, cracks remain inevitable. Recent studies have concentrated on harnessing biological mechanisms to introduce self-healing properties to concrete. A particularly promising method employs microorganisms like Bacillus subtilis, which can induce the precipitation of calcium carbonate (CaCO3) when exposed to moisture and air. This microbial-induced calcite precipitation (MICP) efficiently seals cracks, thereby reducing need for manual repairs and extensive maintenance. This study examined the application of 2.36 × 109 CFU of Bacillus Subtilis ATCC 6633 as a bio-admixture in fiber-reinforced concrete pavement. The study assessed the effectiveness of various concentrations. The research concluded that Bacillus subtilis effectively stimulated self-healing of cracks in concrete width of 1–2 mm and material recovery over the seven (7) day period, as verified by Absorption Test (Sorptivity), Ultrasonic Pulse Velocity (UPV), and X-ray Diffraction Analysis (XRD). However, the efficacy of the self-healing process varied based on the concentration of Bacillus subtilis. Higher concentrations (10%) of Bacillus subtilis improve fracture healing but diminished overall material performance. Furthermore, the direct application of 5% Bacillus subtilis proved to be a highly effective variant among the tested formulations, exhibiting an enhancement of flexural strength by 13.13% at 14 days, surpassing the design specifications.

Abstract. Replacing and repairing cracked concrete can be a costly and time-consuming process that can also be disruptive, with adverse environmental impacts. Taking these challenges into consideration, the current study explores Bacillus subtilis as a bio-admixture to activate an intrinsic self-healing mechanism that allows concrete to heal its cracks by itself. More specifically, the use of Bacillus subtilis ATCC 6633, incorporated into the concrete at a dosage of 2.36 x 109 CFU to heal cracks in the size range of 1-2 mm were tested. Each of the bacteria was assessed at four concentrations—1%, 3%, 5%, and 10% were evaluated for their ability to enhance the self-healing property of the concrete. The self-healing performance and internal structure recovery were assessed using two different methods: the Sorptivity Test (ASTM C 1585) and the Ultrasonic Pulse Velocity (UPV) equipment PUNDIT PL200. The findings revealed that Bacillus subtilis significantly enhanced the self-healing process in 3-7 days, effectively repairing cracks within a 10-day period, as demonstrated by improvements in material recovery, absorption rates, and ultrasonic pulse velocity. The results suggest that 5% Bacillus subtilis concentration has considerable potential to improve the durability and sustainability of concrete, offering a more environmentally friendly and cost-effective solution for autonomous crack repair using the two distinct methods.

Abstract. Reclaimed Asphalt Pavement (RAP) is becoming significant for the sustainable road constructions. Despite its global success, the standardization of RAP as blending materials continues to be hampered by substantial differences and lack of field validation in tropical areas. This study addresses the challenges by utilizing a statistical normalization method to evaluate recent utilization of RAP-based mixtures in tropical countries, evaluating them across six essential factors: mechanical strength, durability, constructability, environmental impact, economic feasibility, and regulatory compliance. The result highlights that Warm Mix Asphalt with RAP (WMARAP) as the top-performing solution among twelve (12) different mixtures with a composite score of 4.44 out of 5.00, achieving up to 30% reduction in carbon emissions, 18% life-cycle cost savings, and full compliance with AASHTO. RAP offers notable benefits for those areas with limited availability of virgin aggregates and reducing construction expenses. In the Philippines, RAP-based mixtures present a promising solution for developing durable, low-emission, and cost-effective pavements. The study presents a practical decision framework for policymakers, engineers, and contractors aiming for sustainable road engineering.

Abstract. Urban flooding has become a major global problem that is caused by the fast growth of cities, climate change, and the lack of proper infrastructure to cope with the increased stormwater runoff. Therefore, an effective stormwater management system is necessary to alleviate flooding by gathering and rerouting rainwater to the drainage systems. Predictive modeling has turned into an important tool for stormwater management simulation, as it can demonstrate runoff behavior and the impact of catch basins. Different hydrologic and hydraulic modeling software each have their own features for studies related to stormwater, watershed, and floodplains. The EPA SWMM integrates green solutions, such as rainwater harvesting, bio-retention systems, permeable pavements, floodplains, and infiltration trenches. The PCSWMM makes it possible to predict floods in real time and design detention systems making it appropriate for large and multiple uses watersheds at the same time. HEC-HMS provides a solid base for event-based and watershed simulations that require a lot of data sources and different runoff diversion methods. Meanwhile, InfraWorks and XPSWMM are dedicated to integrated hydrologic-hydraulic modeling. Moreover, MIKE+ and OpenFlows FLOOD provide high resolution detailed flood simulations and sophisticated unified platforms. Nevertheless, there is not a single modeling platform that completely solves the problem of hydrological, hydraulic and urban variability. The review applied Latent Dirichlet Allocation (LDA) to select relevant papers from various databases and identify the research issues in the simulation software for urban flooding management, which in turn led to the future research and policy making in flood control systems. The research shows that existing modeling tools can only partially connect real-time monitoring information with climate changes and machine learning methods to create complete prediction systems. The research results give new understanding about creating adaptive data-driven flood modeling methods which will help improve stormwater management techniques and upcoming flood management policies for urban areas at risk of flooding.