Mohammad Jamal Khattak

The increasing demand for bricks has raised environmental concerns related to natural clay depletion, land degradation, and agricultural waste disposal. To address these challenges, this study utilizes rice husk ash (RHA) as a sustainable partial replacement for clay in fired clay bricks. Brick mixtures were casted with varying RHA dosages (up to 80%), and the effect of 2% lime addition was also examined. Mixtures were fired at 1000 °C and 1200 °C and were tested for compressive strength, flexural strength, and water absorption. Microstructural and mineralogical characteristics were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). At 1000 °C, increasing RHA content and lime addition increased porosity and reduced mechanical strength due to limited vitrification. In contrast, firing at 1200 °C promoted extensive verification and densification, resulting in improved strengths surpassing the severe-weathering requirements of ASTM C62. Compressive strengths of 74.62 MPa and 52.55 MPa were achieved for bricks containing 20% and 40% RHA, respectively, exceeding ASTM C62 severe weather grade requirements. Results demonstrate that RHA can be utilized at high replacement levels when appropriate firing conditions are applied, supporting sustainable fired brick production and agricultural waste valorization.

This research investigated the utilization of sugarcane bagasse ash (SBA) for developing geopolymer-based sustainable “green” construction materials that can be utilized in transportation infrastructure. The resulting geopolymer material can be used as concrete in road pavements and as a brick in pedestrian walkways, sidewalks, curbs, and other non-structural elements. The physical, mechanical, and durability properties of the geopolymer-based materials were determined, and mixtures were selected to cast bricks for transportation infrastructure. The microstructure and morphology of the selected mixtures were studied using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The results depicted that the compressive strength of SBA–geopolymer bricks depended on various mixture variables, such as SBA dosage, alkali activator ratio, molarity of the sodium hydroxide, and curing temperature and time. The optimum alkali ratio was found to be 1.25. SBA was replaced up to 80% by weight of fly ash. The results revealed that the compressive strength of the SBA–geopolymer composites having 50% SBA and different molar concentrations and curing temperatures were in the range of 11.99–34.91 MPa, which were in accordance with the requirements of ASTM standards. The modulus of rupture was in the range of 3.01–4.44 MPa. The water absorption and strength loss caused by acid attack were also within an acceptable range. SEM, FTIR, and XRD confirmed the formation of geopolymer compounds in different mixtures. The resulting high SBA content geopolymer could be used as a non-structural element in transportation infrastructure.

This research study presents a resilient control scheme for an islanded DC microgrid (DC MG) integrating solar photovoltaic (PV), battery storage (BESS), and piezoelectric (PE) energy harvesting modules. The microgrid (MG) case study represents an energy hub designed to provide electricity for lighting systems in transportation, roads, and other infrastructure. To enhance practicality, the PE is modeled using the real data captured from a traffic simulator. The proposed reinforcement learning (RL) method was tested against four severe and unexpected failure scenarios, including short circuit at the load side, sudden and severe change of load, open circuit, and converter failure. The performance of the controller was quantitatively compared with a conventional PI controller. The results show marginal improvement in one scenario and significant improvement in the other three, suggesting that the proposed scheme is a robust candidate for microgrids with high levels of uncertainty, such as those involving solar and PE harvesters.

Pavement maintenance presents significant financial challenges, driving researchers to explore innovative approaches that can prolong pavement service life and reduce costly interventions. The objective of this research is to examine the feasibility of utilizing polyvinyl alcohol (PVA) fibers to self-heal asphalt pavements. A comprehensive mechanical testing strategy was developed to evaluate the self-healing capability of several hot mix asphalt (HMA) mixtures at the micro- and macro-level. Moreover, to assess the healing behavior of macro fractures in PVA-fiber-reinforced HMA, semi-circular bending (SCB) specimens were loaded until peak load and then allowed to heal at varying time intervals and temperatures for several loading cycles. Healing indices developed based on SCB stiffness, strength, and beam fatigue technique were utilized to measure the self-healing ability of control and reinforced mixtures. By comparing different concentrations of PVA fibers with a control HMA, the optimal fiber dosage was determined based on newly developed healing indices. This study also investigated the impact of healing time and different temperatures on healing. The results demonstrated that PVA fibers expedited the healing process, effectively healing macro-, meso-, and micro-cracks. The most effective recovery occurred with 0.3% fiber content at 40°C for a 2 h duration. Incorporating PVA fibers into asphalt pavements presents a promising solution for extending pavement service life and can be helpful in reducing maintenance costs.

Geothermal energy presents a promising opportunity for sustainable and efficient energy production. To maximize the efficiency of geothermal systems, developing advanced materials capable of effectively transferring and withstanding thermal loads is crucial. This study focuses on demonstrating highly conductive nano-engineered geopolymer cement tailored for geothermal applications using prototype laboratory samples. The study included an evaluation of thermal conductivity, shear bond strength, and compressive strength of newly designed geopolymer mixtures as well as the thermal conductivity of large-scale geopolymer samples, with a specific emphasis on their performance in the handling fluid flow for enhanced geothermal systems. The results showed that, compared to the control geopolymer, the developed geopolymer formulations had a lower thermal conductivity performance due to higher air voids in the system. In general, the addition of carbon nanotubes and graphite in geopolymer mixtures reduces the strength and elastic modulus. The thermal conductivity of the large prototype sample cured for 7 days at 49 °C showed better thermal conductivity for the control geopolymer. Conversely, the water flow data reflected better performance for the modified mixtures. Additionally, numerical simulations were developed and validated by the experimental observations for further studies on the effect of geopolymer properties on the performance of geothermal systems.