Search Results (19)

The increasing demand for sustainable practices in road construction has prompted the search for environmentally friendly and cost-effective materials. This study explores the incorporation of reclaimed asphalt pavement (RAP) and Panasqueira mine waste (greywacke aggregates) as full replacements for virgin aggregates in hot mix asphalt (HMA), aligning with the objectives of UN Sustainable Development Goal 9. Three asphalt mixtures were prepared: a reference mixture (MR) with granite aggregates, and two modified mixtures (M15 and M20) with 15% and 20% RAP, respectively. All mixtures were evaluated through Marshall stability, stiffness modulus, water sensitivity, and wheel tracking tests. The results demonstrated that mixtures containing RAP and mine waste met Portuguese specifications for surface courses. Specifically, the M20 mixture showed the highest stiffness modulus, improved moisture resistance, and the best performance against permanent deformation. These improvements are attributed to the presence of stiff aged binder in RAP and the mechanical characteristics of the greywacke aggregates. Overall, the findings confirm that the combined use of RAP and mining waste provides a technically viable and sustainable alternative for asphalt pavement construction, contributing to resource efficiency and circular economy goals. Full article

Compared to traditional dense asphalt concrete mixtures, stone mastic asphalt (SMA) generally offers superior performance in terms of its mechanical resistance and extended pavement lifespan. Focusing on the Norwegian scenario, this laboratory-based study investigated the durability of SMA considering the influence of the aggregate shape and petrography. The rock aggregates were classified according to three different-shaped refinement stages involving vertical shaft impact crushing. Further, the aggregates were sourced from three distinct locations (Jelsa, Tau and Dirdal) characterized by different petrographic origins: granodiorite, quartz diorite and granite, respectively. Two mixtures with maximum aggregate sizes of 16 mm (SMA 16) and 11 mm (SMA 11) were designed according to Norwegian standards and investigated in terms of their durability performance. In this regard, two main functional tests were performed for the asphalt mixture, namely resistance against permanent deformation and abrasion by studded tyres, and one for the asphalt mortar, namely water sensitivity. Overall, the best test results were related to the aggregates sourced from Jelsa and Tau, thus highlighting that the geological origin exerts a major impact on SMA’s durability performance. On the other hand, the different aggregate shapes related to the crushing refinement treatments seem to play an effective but secondary role. Full article

In this study, the engineering properties of basalt aggregate used for asphalt road pavement on Jeju Island were evaluated, and the characteristics of the asphalt mixtures used were evaluated to assess the suitability of Jeju Island basalt as road construction material. Chemical composition and surface morphology analysis of the basalt and granite aggregate, engineering characteristics analysis, and filler property evaluation were performed. Mix design was performed, and the basic properties of three asphalt mixtures for the surface, intermediate, and base layers were evaluated. Permanent deformation resistance was evaluated through a wheel tracking test, and moisture resistance was evaluated through a dynamic immersion test and a tensile strength ratio test. The optimum asphalt contents of the asphalt mixture using low-porosity basalt aggregate and high-porosity basalt aggregate were determined to be 5.7% and 5.9% in the surface layer, 5.3% and 5.4% in the intermediate layer, and 4.7% and 5.1% in the base layer, respectively. It was found that the basic properties of the asphalt mixtures satisfied Korean quality standards. The dynamic immersion test results of low-porosity basalt aggregate and high-porosity basalt aggregate were 20% and 10%, respectively, which fall far below the quality standard of 50%. The tensile strength ratios of the basalt asphalt mixtures for the intermediate layer were 0.69 and 0.40, and they were found to increase significantly to 0.87 and 0.80 after the application of a suitable anti-stripping agent. Therefore, it was concluded that in order to apply Jeju Island basalt to asphalt pavement, an appropriate anti-stripping material must be applied. Full article

The morphology of coarse aggregate has a significant impact on the road performance of asphalt mixtures and aggregate characterization studies, but many studies were based on the two-dimensional morphology of coarse aggregate, which failed to consider morphological characteristics in a holistic manner. In order to quantitatively analyze the shape, angularity, and texture characteristics of roadway coarse aggregates, a rapid and accurate multiparameter characterization method of coarse aggregate 3D morphology is explored in this article. A 3D laser scanner is used to obtain the 3D point cloud data of pebble, granite, and basalt, and the solid models of the three coarse aggregates are reconstructed. In addition, the fitted ellipsoidal algorithm and Laplace smoothing algorithm are proposed for the characterization analysis of the overall shape, angularity, and surface roughness of coarse aggregate, and the variation rules of multicharacteristic parameters of coarse aggregate are summarized. The results of the study show that the ratio of the three axes of the fitted ellipsoid can be used to classify the shape of coarse aggregate into four types, among which the cubic shape accounts for the majority of the coarse aggregate. By analyzing the fitted ellipsoidal value and the change rate of angularity of coarse aggregate, it is concluded that the larger the values of both, the more angular the aggregate is. Moreover, the study finds that the fitted ellipsoidal value can characterize not only the shape of coarse aggregate, but also its angularity to some extent. Compared with the spherical value, the fitted ellipsoidal value has better variability and is more “sensitive” to the overall data. The change in surface area can well characterize the texture of coarse aggregate. When the particle size is small, the larger the surface area change rate of the coarse aggregates, the better the roughness of the aggregates, among which the surface area change rate of basalt is the largest. The influence of aggregate morphology was not adequately considered in previous studies of asphalt-aggregate adhesion, and this study provides parameter help for subsequent quantitative analysis of the relationship between asphalt-aggregate adhesion and coarse aggregate morphology. Full article

The asphalt mastic–aggregate interaction plays an important role in the overall properties of asphalt mixtures and their durability in service in flexible pavements. This paper aims to study the influence of the physico-chemical features of fillers and the rheological properties of asphalt mastics on the bonding behavior between asphalt and aggregate, and the interfacial deterioration mechanism when subjected to static water immersion and pressured water immersion. It was found that the filler type (limestone powder, basalt powder, and granite powder) had a certain influence on the complex modulus of asphalt mastics, and its pore volume and specific surface area had significant effects on the phase angles and permeability of asphalt mastics. The effect of water pressure can accelerate the deterioration of bond strength of the asphalt mastic–aggregate interface in the short term, indicating that the dynamic water pressure generated by the driving load promotes the water damage process in asphalt pavements. In comparison, the residual bond strength ratio of the granite–asphalt mastic aggregate was the highest, while its bond strength was lower than that of the interface between limestone–asphalt mastics and limestone aggregate. This demonstrated that a low asphalt mastic complex modulus and a high phase angle are helpful in improving the durability of asphalt mixtures subjected to static and pressured water immersion conditions. Full article

Warm Mix Asphalt (WMA) technology can effectively reduce carbon emissions and energy consumption during road project construction. However, it may have a negative impact on the binding properties of asphalt mixtures. In order to effectively evaluate the adhesion performance of asphalt binders and aggregates under the combined influence of WMA and traditional polymer-modified asphalt, this paper provides a comprehensive evaluation at the micro and macro levels. The adhesion between three different modified asphalts (warm mix crumb rubber/ Styrene-Butadiene-Styrene (SBS) composite modified asphalt, warm mix crumb rubber asphalt, and warm mix SBS modified asphalt) and two different aggregates (limestone and granite) under both virgin and short-term aging conditions were analyzed. Regardless of the type of modified asphalt, the results showed that limestone aggregates have better adhesion properties with asphalt binders. In addition, the short-term thermal oxidation aging behavior is conducive to enhancing the asphalt-aggregate adhesion characteristics. Furthermore, WMA additives, crumb rubber, and SBS compound modification can improve the adhesion performance between asphalt and aggregate. Full article

Granite is very widely distributed in the world, but granite is an acidic aggregate with poor adhesion to asphalt. In untreated asphalt mixtures, asphalt pavement water damage and loose disease are more prominent, affecting the service life of the pavement and service level. Enhancing the road performance of granite asphalt mixture generally improves the adhesion properties of asphalt and granite. Qingchuan rock asphalt, anti-stripping agent KH5, aliphatic amine anti-stripping agent AJ-1 and two groups of the composite anti-stripping agents were used to modify the asphalt and analyze the effect of different anti-stripping agents on the improvement of asphalt-granite aggregate adhesion properties based on the surface free energy (SFE) theory. Second, the effect of anti-stripping agents on the rheological properties of asphalt were analyzed by rheological tests, and the modification effect of granite asphalt mixture road performance was evaluated by Marshall tests. The aging of asphalt and asphalt mixture was simulated by thermal oxygen aging, and the durability of different anti-stripping agents was investigated by comparing the performance of asphalt and asphalt mixtures before and after aging. The results showed that Qingchuan rock asphalt can effectively enhance the high-temperature stability and anti-aging properties of asphalt mixes, but the low temperature performance was relatively poor. KH5 and AJ-1 can make up for the lack of low temperature performance of rock asphalt, but the water stability of asphalt mixes decreases after aging. All five groups of anti-stripping agents improve the adhesion of granite-asphalt and the water stability of the asphalt mixture to some extent. Considering the aging effect, the order of granite-asphalt mixture water stability is: KH/RAMA > AJ/RAMA > RAMA > KHMA > AJMA. Full article

This study investigates the effects of two waste materials from construction and industry, namely recycled concrete aggregate (RCA) and Type C fly ash, on the overall performance of a special type of pavement surface mixture, porous asphalt mixture. Mixtures of different combinations of RCA (for partial aggregate replacement) and fly ash (for filler replacement) were prepared in the laboratory and tested for a variety of pavement surface performance parameters, including air-void content, permeability, Marshall stability, indirect tensile strength, moisture susceptibility, Cantabro loss, macrotexture, and sound absorption. The analysis of the results showed that incorporating RCA or fly ash in a porous asphalt mixture slightly reduced the air-void content, permeability, and surface macrotexture of the mixture. A 10% replacement of granite aggregates with RCA in the porous asphalt mixtures led to a reduction in mixture stability, indirect tensile strength, resistance to raveling, and sound absorption. The further substitution of mineral filler with fly ash in the mixture, however, helped to offset the negative impact of RCA and brought the mechanical properties of the mixture with 10% RCA to levels comparable to those of the control mixture. Full article

Coarse aggregate is the main component of asphalt mixtures, and differences in its morphology directly impact road performance. The utilization of standard aggregates can benefit the standard design and performance improvement. In this study, 3D printing technology was adopted to prepare artificial aggregates with specific shapes for the purpose of making the properties of artificial aggregates to be similar to the properties of natural aggregates. Through a series of material experiments, the optimal cement-based material ratio for the preparation of high-strength artificial aggregates and corresponding manufacturing procedures have been determined. The performance of the artificial aggregates has been verified by comparing the physical and mechanical properties with those of natural aggregates. Results indicate that using 3D printing technology to generate the standard coarse aggregate is feasible, but its high cost in implementation cannot be ignored. The 3D shape of the artificial aggregate prepared by the grouting molding process has a good consistency with the natural aggregate, and the relative deviation of the overall macro-scale volume index of the artificial aggregate is within 4%. The average Los Angeles abrasion loss of artificial cement-based aggregate is 15.2%, which is higher than that of diabase aggregate, but significantly lower than that of granite aggregate and limestone aggregate. In a nutshell, 3D printed aggregates prepared using the optimized cement-based material ratio and corresponding manufacturing procedures have superior physical and mechanical performance, which provides technical support for the test standardization and engineering application of asphalt pavements. Full article

There are abundant granite reserves in China, but the adhesion between granite and asphalt is poor, and there are problems such as insufficient water stability, which seriously restrict the application and promotion of granite in asphalt pavement. In order to improve the adhesion between granite and asphalt, as well as the water stability of asphalt mixture, amines and polymers were selected as anti-stripping agents. First, silane coupling agent modified asphalt (SCAMA), rock asphalt modified asphalt (RMA), SBS modified asphalt (SBS), and double rock composite modified asphalt (SCA&RMA) were produced; the modification effect of different anti-stripping modified asphalts was evaluated. Then, the adhesion of different types of asphalts and granite aggregates before and after aging was evaluated by time-delayed water immersion method. Finally, AC-10 and AC-16 granite–asphalt mixtures were designed, through indoor performance test and 1/3 scale accelerated loading test, evaluating the improvement effect of granite–asphalt mixture on pavement performance. The results show that the asphalt modified by amine or organic polymers anti-stripping agent could significantly improve the adhesion between granite and asphalt. The Hamburg wheel-tracking test failed to fully reflect the whole process of high-temperature rutting failure. When evaluating the high-temperature performance and water stability of asphalt mixtures, it is recommended that the evaluation method should cover the whole failure stage of asphalt mixtures; considering the coupling effect of water and high temperature, the order of water stability of granite–asphalt mixture is proposed as follows: SCA&RMA > RMA > SBS > SCAMA > 70-A, and SCA&RMA has the best modification effect. Full article

Steel slag is a byproduct generated as waste during the steelmaking process and can be considered a cost-effective and environmentally acceptable alternative to replace natural aggregates. Using steel slag aggregates (SSA) to produce asphalt mixtures promotes sustainability and circular economy principles by using an industrial byproduct as a raw material. Thus, this work mainly aims to design more sustainable asphalt mixtures with high amounts of SSA that fit the circular economy expectations. This work developed two asphalt mixtures with SSA for surface (AC 14 surf) and binder/base (AC 20 bin/base) courses. Initially, the excellent wearing and polishing resistance of SSA and their good affinity with bitumen demonstrated the potential of this byproduct to be used in asphalt mixtures. Then, when analyzing the influence of using two different SSA incorporation rates (50% and a percentage close to 100%) in both asphalt mixtures, it was concluded that the use of SSA should be limited to 75% to avoid excessive air void contents and durability problems. The importance of considering the different particle densities of SSA and natural aggregates was highlighted during the mix design by defining a relationship between an effective and equivalent binder content. Finally, the mechanical performance of AC 14 and AC 20 with 75% SSA incorporation was compared to identical conventional mixtures produced with natural granite aggregates. The results obtained showed that the asphalt mixtures with 75% SSA have some workability problems due to the rough and porous surface of SSA. However, they present an excellent water sensitivity and permanent deformation resistance, surpassing the performance of the conventional asphalt mixtures. Full article

Two of the main problems encountered in flexible pavements are the stripping of coarse aggregates and the formation of rut depth due to increases in the volume of road traffic and heavy vehicle loads, especially in areas where speeds are low. The existence of rut depth also affects the comfort and safety of road users due to the water accumulation on the pavement surface and reducing tire/pavement friction, which can lead to hydroplaning phenomena. In this research, it was proven that the use of fillers of different origins influences the affinity between aggregates and the binder. The effect of an adhesion promoter in the mix design (such as the amine included in cellulosic fiber pellets) was also studied. Several tests were carried out to determine the binder/aggregate adhesiveness, water sensitivity and resistance to permanent deformation, to evaluate the performance of different blends. It was found that the addition of this additive increased 10% of the aggregate surfaces covered with bitumen when compared with the aggregates without this addition. As expected, the water sensitivity tests showed that the mixture with granitic filler had the lowest indirect tensile strength ratio (ITSR) value (70%), while the mixtures with limestone filler led to the highest percentages (ranging from 83 to 93%). As for the results of the wheel tracking tests (WTT), it was confirmed that the use of limestone filler translates into an improvement in the performance against the permanent deformation of the asphalt mixtures. The mixture with higher bitumen content and adhesion promoter revealed the best average results. Full article

The aggregate in an asphalt mixture is coated with mastic consisting of bitumen (dilute phase) and filler (particulates phase). The interaction of bitumen and filler and packing of filler plays an important role in the properties of mastics. The micromechanics models from composite rheology can be used to predict the stiffening effect of a suspension. In this research, the stiffening effect of fillers was investigated based on the rheology of mastic. The frequency sweep tests in a dynamic shear rheometer at different temperatures were performed within a linear viscoelastic range to construct the master curves. The volume fractions were expressed as compositional volumes of filler in mastic. The particle shape and surface texture are determined through microscopy. We used six micromechanics-based models to predict the stiffening potential of fillers in mastics. The models include Maron–Pierce, Lewis Nielsen, Mooney, Krieger–Dougherty, Chong, Robinson, and Hashin Models. The results show that the same volume content of filler has a different effective volume. The fillers increase the stiffening effect of the composite, especially at high temperatures. The behaviour of fillers with similar effective volume and packing is identical. The filler type affects the stiffening of mastics. Micromechanics modelling results show that most models show an accurate stiffening effect at lower concentrations with the exception of the Chong Model. The Maron–Pierce Model under-estimates the stiffening potential for granite mastic at higher concentrations beyond the 30% filler content fraction. The value of maximum packing fraction (ϕ_m) and Einstien coefficient (K_E) in the Mooney model are significantly different from other models for limestone and granite, respectively. The line of equality graph shows good agreement of measured and predicted stiffness. It is difficult to precisely model the mastic data with any single model due to the presence of complex stiffening effects beyond volume filling. Full article

Workability is of importance during asphalt construction, which plays a role in increasing stability and other performances. Using different mineral fillers can result in different asphalt workability in the same mix design. While fillers can increase stability, viscosity with regards to asphalt mastic needs to be considered for working in the field. Nowadays, waste natural materials can allow agriculturists to get more income by recycling in many industries. In this study, the objective is to determine the effect of using bagasse and coconut peat as filler on mastic viscosity and the resistance to failure performances. Findings show that the viscosities of asphalt mastic with coconut peat and bagasse fillers are relatively similar to those with limestone filler for all temperatures at 20 percent filler content. Additionally, the stabilities and flows of asphalt mixtures mixed with waste natural fillers were close to those mixed with mineral fillers at equivalent temperatures. In conclusion, the mastic viscosity is vital for determining the workability of asphalt mixture. The waste natural fillers including bagasse and coconut peat give similar mastic viscosity to limestone filler and higher than granite filler, which shows less difference to performance results. Full article

Acidic aggregates have the merits of high strength and good abrasion resistance capacity. However, its poor adhesion with asphalt binder constrains its application in pavement construction. Among these, the granite aggregate is the typical one. Therefore, this study modified granite aggregates’ surface to improve their adhesion property with the asphalt binder. Specifically, the silane coupling agent (SCA) KH-560 was adopted to achieve the modification purpose. Subsequently, asphalt mixtures with modified and unmodified granite, basalt, and limestone were subjected to the boiling test, immersion test, and freeze-thaw splitting test to estimate the asphalt adhesion property. Moreover, a molecular dynamic simulation was employed to characterize the asphalt-aggregate interface from the molecular scale. The radius distribution function (RDF) and interaction energy were used as the primary indicators. The results showed that the SCA could efficiently improve the adhesion between asphalt and granite aggregates, comparable with the alkaline aggregates. In terms of the molecular scale, the incorporation of SCA could significantly increase the concentration distribution of asphalt molecules on the aggregate surface. Meanwhile, the interaction energy was correspondingly increased due to the considerable growth of non-bond interaction. Full article