Bio-oil modified binder derived from cotton stalks as an eco-friendly alternative binder for flexible pavements.

Scientists and engineers encounter considerable environmental and economic obstacles stemming from the depletion of crude oil or petroleum fossil fuel reservoirs. To mitigate this challenge, alternative solutions like bio-oil-modified binder derived from biomass have been innovated. This research aims to examine the feasibility of using bio-oil-modified binder obtained from cotton stalk waste as a modifier. Various mechanical and physical tests, including penetration, softening point, ductility, and dynamic shear rheometer tests, were conducted on asphalt binder incorporating 5% and 10% bio-oil-modified binder. Wheel tracker, four-point beam fatigue, and dynamic modulus tests were used to evaluate asphalt mixture performance, including rutting, fatigue, and dynamic stiffness. A rolling bottle test (RBT) and asphalt binder bond strength (BBS) were used to assess moisture susceptibility. A bio-oil-modified binder enhanced ductility and penetration characteristics while reducing the softening point. With the addition of a bio-oil-modified binder, stiffness was reduced in parameters such as complex shear modulus and phase angle. In fact, for both specimens containing 5% and 10% bio-oil-modified binder, statistically significant differences were observed among the measured samples. As a result of this reduced stiffness, the modified asphalt binder is more suitable for low-temperature applications. Additionally, 5.8% increased at 10% and 3.1% at 5% CS. Bio-oil-modified binder, compared to virgin mixtures, supports equal rut resistance. However, the RBT and BBS tests revealed that the addition of bio-oil-modified binder increased the susceptibility of conventional asphalt binder to moisture. The findings suggest that bio-oil-modified binder can enhance asphalt binder properties in low-temperature regions, but further research is needed to improve moisture resistance.

Enhancing sustainability in self-compacting concrete by optimizing blended supplementary cementitious materials.

Within concrete engineering, the uptake of self-compacting concrete (SCC) represents a notable trend, delivering improved workability and placement efficiency. However, challenges persist, notably in achieving optimal performance while mitigating environmental impacts, particularly in cement consumption. However, simply reducing the cement content in the mix design can directly compromise the structural-concrete requirements. Towards these challenges, global trends emphasize the utilization of appropriate waste materials in blended concrete. This study explored a promising strategy by integrating supplementary cementitious materials (SCMs) to contribute to the United Nations' Sustainable Development Goals (SDGs) in addition to the engineering contributions. It suggests an optimal combination of Metakaolin (MK) and Limestone Powder (LP) to partially substitute cement. The research methodology employs the response surface method (RSM) to systematically explore the ideal ingredient ratios. Through a comprehensive analysis of orthogonal array of 16 mixes, encompassing both mixture and process variables, this study aims to explain the effects of MK and LP addition on the rheological and mechanical properties of SCC with varying cement replacement levels. In terms of mixture constituents, the total composition of cement, MK, and LP was fixed at 100%, while coarse aggregate (CA), fine aggregate (FA), and the water-to-binder ratio were held as process variables. In order to assess the rheological properties of the mix-design, various tests including slump flow, L-box, and sieve segregation were conducted. Additionally, to evaluate mechanical strength, samples were tested for compressive strength at both 7 and 28 days. Findings from the experiments reveal higher concentrations of MK result in reduced workability and hardened properties. Through RSM-based designed experimentation covering both rheological and mechanical aspects, it is observed that the optimal cement replacement level lies between 40 and 55%. The findings of this study contribute to the advancement of sustainable and structurally robust concrete practices, offering insights into the optimal utilization of SCMs to meet both engineering requirements and environmental sustainability goals.