Relationships among moisture loss, volumetric and strength properties of cold mix asphalt: impacts of curing dynamic and active fillers

Palm oil fuel ash application in cold mix dense-graded bituminous mixture

Cold-mix asphalt (CMA) can be produced more sustainably by using byproducts as fillers instead of conventional materials such as cement. This study used a new filler of calcined eggshell powder (cESP)-activated ground granulated blast furnace slag (GGBFS) in CMA mixtures to improve performance and reduce curing time. The outcomes were compared with those of CMA mixtures comprising limestone and cement fillers and two hot-mix asphalt (HMA) mixtures with AC10 and AC20 asphalt binders. This study used indirect tensile strength, cracking tolerance, and rutting performance as basic performance measurements and used moisture loss, volumetric properties, and microstructural analysis to visualize the mechanism behind the strength development. The results reveal that cESP-activated GGBFS can improve the performance of CMA mixtures at both early and late ages, and performs comparably to cement filler CMA and conventional HMA mixtures for application in pavement structural layers. The hydration products were visualized using microstructural analysis in the cement and cESP-activated GGBFS CMA mixtures, which can enhance the bond strength in the mixtures. Hydration reaction and moisture loss together contributed to strength development in cement and cESP-activated GGBFS CMA mixtures. Conversely, strength improvement in limestone and pure GGBFS mixtures was entirely attributable to the loss of water by evaporation. Because GGBFS and eggshells are byproducts, utilizing them in CMA construction will be economically and environmentally advantageous, and lead to improved mechanical performance and a shorter curing time.

Effects of air voids on comprehensive laboratory performance of cold mix containing recycled asphalt pavement

Optimizing the mix design of cold bitumen emulsion mixtures using response surface methodology

Cold bitumen emulsion mix (CBEM) is an emerging sustainable material for constructing the base or surface layer of flexible pavements, reducing energy consumption and global warming effects compared to hot mix asphalt. The main challenges associated with CBEM are low initial strength, moisture susceptibility, etc. This is primarily due to water encapsulation. The curing process allows the water to evaporate gradually over time, improving mechanical properties. This study investigates CBEM’s volumetric and mechanical properties under different curing conditions. CBEMs were prepared using low (50 blows) and high (75 blows) compaction efforts and cured at 25, 40, and 55 °C for 1 to 28 days. In volumetric characteristics, the air voids and voids in mineral aggregates decreased slightly with curing, while total binder volume decreased. Effective binder volume and voids filled with binder increased slightly, then decreased. The mechanical properties, i.e., Marshal Stability, Marshal Quotient, Indirect Tensile Strength (ITS), and Moisture Susceptibility parameters like the Indirect Tensile Strength Ratio (ITSR) and Retained Marshal Stability (RMS), were found to improve over time at each curing temperature. Using a high curing temperature further improved the mechanical characteristics of CBEM. The curing process was decelerated in case of CBEM prepared by high compactive efforts compared to CBEM prepared by low compactive efforts. The Michaelis-Menten model can be used to analyze moisture loss growth and the development of mechanical properties over time. The strength-maturity model can be developed by using ITS as strength parameters. There was a strong correlation between all mechanical characteristics and moisture loss.

This study evaluates the enhancement of cold mix asphalt (CMA) through dual modification with high-grade VG30-based bitumen emulsion (BE30) and pozzolanic fillers, namely, ground granulated blast furnace slag (GGBS) and rice husk ash (RHA). Dense-graded CMA mixes were prepared using semi-dense bituminous concrete (SDBC) gradation and cured for 3, 7, 14, and 28 days, with BE30 compared with a VG10-based emulsion (BE10) and filler systems comprising basalt dust, binary, and ternary blends. The laboratory parameters inicluded Marshall and volumetric properties, indirect tensile strength (ITS), tensile strength ratio (TSR), and rutting resistance via IDEAL-RT, while energy dispersive spectroscopy (EDS) was used to quantify the Ca/Si ratios to capture hydration-driven densification. Correlation and statistical analyses were performed to establish quantitative links between microstructural chemistry, macroscopic performance, and life cycle assessment (LCA) benchmarked energy, emissions, and costs against hot mix asphalt (HMA). The results revealed that BE30-based mixes consistently outperformed BE10 because of their higher binder viscosity, stiffer residue and improved filler reactivity. Synergistic binary and ternary blends (C-BRG, C-Eq) achieved the highest Ca/Si ratios, superior cohesion, balanced volumetrics and rutting resistance approaching HMA levels. Statistical findings validated the Ca/Si ratio as a reliable predictor of mechanical and durability responses, while LCA confirmed nearly 50% lower energy demand, over 50% reduction in CO₂ emissions and 15%–20% cost savings compared to HMA. The integrated experimental–statistical–environmental evaluation establishes BE30-pozzolanic CMA as a durable, sustainable, and climate-conscious alternative for structural pavements, bridging the gap between conventional CMA and high-performance low-carbon asphalt technologies.

Cold mix asphalt (CMA) has been increasingly recognized as an important alternative technology to hot mix asphalt (HMA) worldwide. The present study investigates the optimum proportions of fine content (FC) and emulsion content (EC) to gain suitable levels of both mechanical and volumetric properties. A factorial design with response surface method (RSM) was applied to optimize the mix design parameters. This work aimed to investigate the interaction effect between these parameters on the mechanical and volumetric properties. The stability and indirect tensile strength (ITS) tests were performed to obtain the mechanical response. The results indicate that the interaction of both FC and EC influences the bulk density. However, the EC tended to influence the ITS more significantly than FC. Further, the experimental results for the optimum mix design were in agreement with model predictions. It is found that optimization using RSM is an effective approach for mix design of CMA.

Cold Mix Asphalt (CMA) is a sustainable alternative to conventional hot mix asphalt(HMA) due to its lower energy consumption and reduced environmental impact. However, CMAs often suffer from high moisture susceptibility, prolonged curing times, and inadequate mechanical performance. This study investigates the potential of calcium alginate capsules (CA capsules) containing waste sunflower oil (WSO) and waste engine oil (WEO) to improve CMA performance. Unlike previous research focusing on self-healing aspect of rejuvenating capsules, this work evaluates the impact of these CA capsules on curing efficiency, strength development, and mechanical behavior under different curing times and compaction methods: Marshall Compacted Mixture (MCM) and Gyratory Compacted Mixture (GCM). CA capsules were characterized using the Field Emission Scanning Electron Microscopy (FESEM)-EDS-Map and Thermogravimetric Analysis (TGA), and mechanical properties of CMA samples were assessed via indirect tensile strength (ITS), tensile strength ratio (TSR), rutting, and semi-circular bending (SCB) fracture tests.Weight measurements taken over the curing period showed that mixtures containing 0.5% CA capsules experienced greater moisture loss, thereby accelerating the curing process. GCM samples exhibited up to 90% higher ITS values than MCM samples, while samples with CA capsules showed an average 7-15% decrease in dry ITS. TSR values increased by up to 10% with 0.5% CA capsule addition, indicating improved moisture resistance. Fracture energy increased by 18-22% at - 20°C in samples with 1% WSO, despite a slight reduction in fracture toughness. ANOVA analysis confirmed that compaction method had the greatest influence on ITS, TSR, and fracture energy, while CA capsule type mainly affected rutting depth. CA capsules with WEO led to deeper ruts than WSO, suggesting better compatibility of WSO with the asphalt matrix. These findings highlight that incorporating oil-based CA capsules-especially at 0.5-1% content-not only improves curing efficiency but also enhances the durability and sustainability of CMAs, particularly under low-temperature and high-moisture conditions.

From the perspective of sustainability and environmental concerns, the use of cold-mix asphalt (CMA) and recycled asphalt pavement (RAP) is more advantageous than the use of hot mix asphalt (HMA) and warm mix asphalt (WMA). Some researchers used a mixture of CMA and RAP to improve the mechanical properties of pavement and made it more economical. However, only a few studies have focused on using a high content of RAP—particularly 100% RAP—as the virgin aggregate. Therefore, this study aims to analyse cold-mix asphalt (CMA) using 100% recycled asphalt pavement (RAP) instead of virgin aggregate raw materials and to determine the best mixture for the production of environmentally friendly asphalt. It is necessary to investigate the performance of CMA mixed with RAP in terms of the resilient modulus, indirect tensile strength, fatigue and rutting resistance. In this study, the percentage of bitumen emulsions added is 2%, 2.5%, 3%, 3.5%, and 4%, along with 100% RAP material. The results indicate that the fatigue life of the RAP mixture increased by 49.34% with the addition of bitumen emulsion (BE) from 2% to 4%, while the wheel tracking test experienced a decrease in rutting depth along with an increase in BE dose of 4%, which was 9 mm. The mixture containing 4% asphalt emulsion has the best performance. The results suggested that increasing the BE dosage increases the resistance against rutting and fatigue.

Although conventional hot mix asphalt (HMA) has good performance, it has many drawbacks, such as gas emission into the environment, high energy for preparation and compaction, and difficulty controlling temperature for long transfer distances. Therefore, some sustainable technologies, such as cold-mix asphalt (CMA), are used. This study aims to develop cold mix asphalt (CMA) using by-products and waste materials. The methodology for this study included using four types of filler material: CKD (cement kiln dust), OPC (ordinary Portland cement), SF (silica fume), and RH (rice husk) as fillers. Laboratory tests were performed to assess the volumetric and mechanical characteristics of the modified mixture using Marshall test, indirect tensile strength, and retaining strength. The findings showed that CMA-CKD has significantly improved in mechanical characteristics. Also, other types of fillers, such as SF, and RH Ash, as activators of CMA-CKD, showed substantial enhancement in their mechanical properties. CMA- CKD -SF showed performance superior to other modified mixtures. It concluded that the updated CMA could be an alternative to the CMA-OPC to gain the required mechanical properties besides other benefits such as cost-effectiveness and environmental impact.

This paper aims at comparing the 3D discrete element modelling of the indirect tensile (IDT) strength of asphalt mixtures with and without considering the air void size and distribution. Micromechanical models for predicting the IDT strength of asphalt mixtures, with and without considering the air void size and distribution, were established using X-ray computed tomography and 3D discrete element method (DEM) incorporated with a cohesive zone model (CZM). The IDT strength of three asphalt mixtures were simulated at three different temperatures on the basis of these models. Simulation results were verified against known experimental IDT tests. The results show that air void characteristics affected greatly the IDT strength of asphalt mixtures, and with the same material parameters, the IDT strength with considering the real air void size and distribution was lower and closer to the experimental IDT strength than that without considering the real air void size and distribution. Furthermore, aggregate size and temperature also significantly affected the IDT strength. IDT strength increased with increasing aggregate size or decreasing temperature. Aggregate size had an increased impact on the IDT strength with increasing temperature, whereas air void characteristics had a decreased influence on the IDT strength with increasing temperature.

Characterization and correlation analysis of mechanical properties and electrical resistance of asphalt emulsion cold-mix asphalt

The quest to developing a universally acceptable mix design procedure for cold mix asphalt (CMA) is in the spotlight of continuous research. Moreover, the performance improvement of CMA coupled with sustainable construction drives had witnessed the inclusion of industrial by-products and biomass waste alike in CMA. Nonetheless, various transportation departments in different countries tailor CMA’s design to suit their geographic regions’ peculiar challenges. Despite such efforts, mix designs need to produce laboratory results replicative of service conditions capable of ameliorating the high void content, weak early strength, and slow rate of strength gain of CMAs. This study proposed a performance-based mix design based on the combined result of indirect tensile stiffness modulus (ITSM) and Cantabro loss tests compared to the standard Marshall mix design. The mixtures contain binary blending of 1–4% palm oil fuel ash (POFA) with 3–6% granite filler by total aggregate weight in a fine dense-graded CMA using a polymer-modified cationic quick set (CQS-1h) and an unmodified rapid set (RS-1K) emulsified asphalt. A gradation with a nominal maximum aggregate size (NMAS) of 4.75 mm (FGCMA-4.75 mm) was employed. In addition to Cantabro and ITSM, the designed mix was tested for Indirect Tensile Strength (ITS), and modified Lottman’s test. Results revealed a significant correlation between the usual Marshall design with the proposed design based on the established optimum emulsion contents (OEC). An optimal 3% POFA yielded moisture-resistant mixtures with enhanced mechanical and Marshall volumetric properties in void reduction, increased stability, and adequate early strength.KeywordsCold mix asphaltFine dense-graded cold mix asphaltPalm oil fuel ashCQS-1hRS-1K

Cold mix asphalt (CMA) can be a quick, environmentally friendly, and low-cost option for utility-cut backfilling on urban streets and most highway agencies prefer it as a pothole patching and pavement surface repairing material over hot mix asphalt (HMA) during winter and wet seasons. However, applying poor quality CMA may result in premature patching and backfilling failures, reduce pavement’s integrity and longevity, and impair drivers’ safety. Additionally, CMA’s lack of stability and durability while exposed to heavy traffic, moisture, and freeze-thaw conditions may accelerate further deterioration. This paper focused on evaluating and comparing twelve CMAs through laboratory tests to determine properties that may cause poor performance in cold climatic regions. Taking into consideration the identified CMA distresses, this study conducted Marshall Stability and flow, indirect tensile strength (ITS), cohesion, and adhesiveness tests on nine proprietary and three conventional cold mixes, including both open- and dense-graded materials. Most mixes had low adhesion properties and high sensitivity to freeze-thaw cycles. An analysis of variance showed that aggregate grain size distribution and bitumen content had a significant effect on CMA’s performance.

Effect of curing and compaction on volumetric and mechanical properties of cold-recycled mixture with asphalt emulsion under different cement contents