Bagasse ash (BA), a by-product of the sugarcane industry, is produced in substantial amounts and typically discarded, leading to environmental degradation and the misuse of valuable agricultural land. While BA has shown potential as a filler in asphalt concrete, limited research exists,...

The global asphalt industry seeks sustainable alternatives to reduce its environmental footprint. This study investigates the potential of an industrial by-product, namely lime kiln dust (LKD) as an alternative mineral filler for asphalt mixtures, focusing on its impact on physico-chemical properties and overall mixture performances. Collaborative efforts involving university and industry laboratories were undertaken from sample preparation to performance testing and to investigate the potential of LKD-modified mixture. Through a comprehensive laboratory investigation involving mechanical tests (Marshall stability, indirect tensile strength, resilient modulus, dynamic creep, and Hamburg wheel tracking) and microstructural analysis (field emission scanning electron microscopy coupled with energy dispersive x-ray spectroscopy and x-ray diffraction), LKD-modified mixtures demonstrated superior performance. The main quantitative results show that the AC14 + 2%LKD mixture exhibited a 27% increase in resilient modulus (5549 MPa versus 4375 MPa) and a 58% higher Dynamic Stability (4167.94 versus 2630.06 cycles mm ⁻¹ ) compared to the standard AC14 + 2%OPC mixture. Furthermore, LKD mixtures showed enhanced moisture resistance, with the AC20 + 2%LKD mix achieving a tensile strength ratio of 1.21, indicating superior moisture damage resistance compared to conventional fillers. Critically, the AC14 + 2%LKD mixture demonstrated a 44% reduction in rut depth (2.51 mm versus 4.50 mm) compared to the traditional AC14 + 2%OPC mixture. The study concludes that LKD is not only an eco-friendly filler aligning with circular economy principles but similarly a technically superior one that significantly improves rutting resistance and durability of asphalt pavements.

This study was conducted to predict the dynamic modulus of Pakistan’s regionally prevalent bituminous mixtures using a wide range of material properties, mix design parameters, and testing conditions. A total of twenty-four bituminous mixes, characterized by sixteen distinct gradations and four different types of bitumen, were tested for dynamic modulus at various temperatures and frequencies. Three different types of models were used on the experimental data, namely, the traditional Witczak 1-37 model, recalibrated Witczak 1-37 model, and the recalibrated Witczak 1-37 model with dummy variables. Recalibration was done using 75% of the data, while the remaining 25% was used for testing. In each case, the model’s accuracy was reported using R-squared values and two error parameters. The comparison of the models clearly demonstrated that the traditional Witczak model had the lowest accuracy in terms of the error parameters with error terms exceeding 3. Recalibrated models with and without the dummy variables, on the other hand, produced comparable results, with errors less than 0.5. The recalibration revealed an insignificant impact of fine material on stiffness. It also showed that 60/70 asphalt from a specific source has a significant impact on the model, while other types had an insignificant effect. The study findings are expected to be equally beneficial to both researchers and practitioners working on pavements mechanistic-empirical design. Future study might include incorporating other parameters and the most recent machine learning techniques to build models for the prediction of locally utilized bituminous mixes in Pakistan.

In recent years, the rapid development and proliferation of highways in China have made asphalt pavement maintenance increasingly complex, requiring maintenance management departments to make practical choices of preventive maintenance measures within limited budgets. To improve comprehensiveness, scientific rigor, and the economy of decision-making, the Analytic Hierarchy Process (AHP) was employed to conduct a decision-optimization study of preventive maintenance measures for asphalt pavements. Taking the preventive maintenance project of the Liuzhou North Ring Expressway in Guangxi as a case study, maintenance measures were initially selected through road condition assessment and investigation. A multi-level, multi-objective decision-making AHP model was constructed, including an objective layer, a criterion layer, an indicator layer, and a scheme layer. By comprehensively considering maintenance needs and assigning values to multi-level factors, the weights and priorities of each maintenance measure were determined. The results show that the ranking and weight calculation of measures such as ultra-thin cover, composite seal coat, micro-surfacing, thin layer cover, and seal coat are relatively rational, and the theoretical analysis results are in good agreement with actual needs.

The viability of lime kiln dust (LKD) as a substitute filler in asphalt paving materials has been assessed to determine its suitability for road surfacing applications. This study compares the chemical composition, environmental impact, and leaching behavior to conventional fillers like ordinary portland cement (OPC) and hydrated lime (HL). Using attenuated total reflectance Fourier transform infrared spectroscopy, it was found that LKD shares almost similar functional groups with OPC and HL, including calcium hydroxide, carbonate, silica, and sulfate, suggesting its suitability for improving asphalt durability. Gas chromatography-mass spectrometry (GC-MS) analysis identified hydrocarbons, esters, brominated alkanes, and phenols in all fillers, with OPC showing higher ester concentrations, whereas LKD and HL exhibited more varied compositions. These differences indicate distinct environmental impacts, with compounds such as 2-Bromododecane and phenols contributing to emissions. Toxicity characteristic leaching procedure tests confirmed that heavy metal concentrations (such as Pb: 0.14 ppm and Cu: 0.05 ppm) in LKD were well below those of OPC (such as Pb: 0.28 ppm and Cu: 2.56 ppm), and HL were within safe regulatory limits, ensuring their environmental safety. Furthermore, GC-MS analysis revealed that LKD contained a lower total concentration of critical organic compounds, such as the bis(2-ethylhexyl) ester (13.45 % in LKD versus 22.89 % in OPC), reinforcing its lower environmental impact profile. Based on the findings, LKD emerges as a viable, environmentally safer alternative filler for asphalt, offering almost similar performance benefits to conventional fillers while lowering environmental risks. The study supports the use of LKD to enhance pavement durability and promote more sustainable construction practices.

This study investigates the influence of shear rate on the non-Newtonian flow behavior of asphalt binders modified with 1–5% organophilic nano clay by weight. Asphalt binders exhibit shear-thinning characteristics, where viscosity decreases with increasing shear rate, enhancing elasticity and reducing temperature sensitivity. Two penetration-grade bitumen samples (60/70 and 80/100) from Attock Refinery Limited (ARL), Pakistan, were modified using the melting method as per ASTM D6606. Rotational viscometer tests (ASTM D4402) were conducted at 135°C, over shear rates from 3.4 to 34 s−1. Viscosity dropped by nearly 60% with increasing shear rate, with the 5% nano clay blend exhibiting the highest viscosity (385.5 cp (mPa·s)) at low shear rates. All concentrations demonstrated improved flow behavior, with 5% yielding the most significant effect. These findings highlight the potential of organophilic nano clay to improve binder rheology, indicating enhanced resistance to rutting and deformation, critical for pavement applications. Further field-scale research is recommended to evaluate long-term performance, mix workability and economic feasibility.