Search Results (24)

The transition to a circular economy requires new materials and products with new production designs, technologies, and processes. In order to create new materials with physico-chemical qualities suitable for application in the building materials engineering sector, stone dust and polymer waste—two environmentally hazardous industrial wastes—were combined in this study. The materials obtained were evaluated based on an analysis performed using the Micro-Deval test. The results obtained showed a Micro-Deval coefficient value of 7.7%, indicating that these artificial aggregates can replace the natural aggregates used in road construction. Additionally, it was shown that the stone dust used could be applied as a sorbent for dyes without later leaching this dye from the final synthetic stones. Another category of materials that meets the principles of the circular economy and was developed in this study is bituminous mastic, which is currently used for the hot sealing of joints in road infrastructure. For this purpose, a composite material was developed using stone dust and cooking oil to replace the filler, a non-regenerable source used for obtaining bituminous mixtures. Specific standard methods were used to assess the degree to which the new materials approach the behavior of commercially available products. Full article

Cracks in asphalt mixtures compromise the structural integrity of roads, increase maintenance costs, and shorten pavement lifespan. These cracks allow for water infiltration, accelerating pavement deterioration and jeopardizing vehicle safety. This research aims to evaluate the impact of synthetic fibers, specifically glass fiber (GF) and polypropylene fiber (PPF), on the crack resistance of Hot-Mix Asphalt (HMA). An optimal asphalt binder content of 5% was used in all sample designs. Using the dry mixing technique, GFs and PPFs were incorporated into the HMA at dosages of 0.50%, 1.00%, and 1.50% by weight of the aggregate. The effects of these fibers on the mechanical fracture properties of the HMA were assessed using Semi-Circular Bending (SCB), Indirect Tensile Asphalt Cracking Tests (IDEAL-CTs), and Three-Point Bending (3-PB) tests. This study focused on fracture parameters such as fracture work, peak load, fracture energy, and crack indices, including the Flexibility Index (FI) and Crack Resistance Index (CRI). The results from the SCB and IDEAL-CT tests showed that increasing GF content from 0.5% to 1.5% significantly enhances the flexibility and crack resistance of HMA, with FI, CRI, and CT Index values increasing by 247.5%, 55%, and 101.35%, respectively. Conversely, increasing PPF content increases the mixture’s stiffness and reduces its crack resistance. The PP-1 mixture exhibited higher FI and CT Index values, with increases of 31.1% and 10%, respectively, compared to the PP-0.5 mixture, based on SCB and IDEAL-CT test results. The SCB, IDEAL-CT, and 3-PB test results concluded that fibers significantly influence the fracture properties of bituminous mixtures, with a 1% reinforcement dosage of both PPFs and GFs being optimal for enhancing performance across various applications. Full article

During the production and laying phases of hot-mixing asphalt (HMA), various volatile organic compounds (VOCs) and noxious gases such as H₂S are released into the atmosphere. These emissions are a serious environmental problem, a risk to human health, and expose workers and residents to unfriendly odours. The aim of this study was the development of a fast and sensitive analytical method to detect the H₂S emitted from hot bituminous binder that is generally used in the various stages of asphalt production, processing, handling and during road construction. The method consisted in the analysis of evolved H₂S from a flask with molten bitumen, using nitrogen as a carrier gas to lead the volatile compounds into a residual gas analyser equipped with a quadrupole mass spectrometer. The analysis was performed following the H₂S-specific signals at m/z 33 (HS⁺) and at m/z 34 (H₂S⁺) in real time, directly on the sample without laborious and expensive pre-treatments and with short response times (<6 s). Calibration with a standard mixture of 1000 ppm of H₂S in nitrogen allows semi-quantitative H₂S detection. The sensitivity and rapidity of the method were evaluated by quenching the release of sulphur compounds with commercial odour-suppressing agents. Upon addition of 0.1% of additive in two minutes, the H₂S signal drops about 80% in two minutes, confirming the good response of the method, even with a very complex matrix. Full article

This study focuses on the investigation of the effect of a reclaimed asphalt material (RAP) and a bio-rejuvenator (mix of vegetable oils) on the stiffness modulus and indirect tensile strength (ITS) values of eight bituminous mixtures produced by using three types of compaction, with different RAP amounts (25% and 50%) and rejuvenator (0%, 0.20%, 0.40% and 0.60% by mass of RAP). A conventional hot mix asphalt was considered as the reference mix. All tests were performed on cylindrical samples produced using: Marshall compaction with 50 blows/side, cored cylindrical specimens from slabs compacted using a roller compactor (39 passes), and, respectively, gyratory compaction on 80 gyrations. Stiffness modulus and ITS values showed strong linear variation with the increase in rejuvenator content, independently of test temperature and type of compaction. The rejuvenating effect of the bio-rejuvenator was observed to counterbalance the impact of RAP. The results at 20 °C for gyratory specimens for the mix with 50% RAP and 0.40% bio-rejuvenator were comparable/closer (under 5% relative difference) to those obtained for the reference mix. A strong correlation between stiffness modulus values of mixes and penetration values of the corresponding binder blends was obtained (${\mathrm{R}}^2\ge 0.977$). Full article

When designing settlements according to the “Green Building” principle, it is necessary to develop a heating system based on climatic conditions. For example, in areas with a sharply continental climate (cold and prolonged winters), it is sometimes necessary to use solid fuel boilers (in the absence of gas). However, to use these, it is necessary to use biomass or biomass-coal blends as fuel to increase their combustion heat. The addition of biomass waste to coal can be aimed at achieving various objectives: utilization of biomass waste; reduction of solid fossil fuel consumption; improvement of environmental performance at coal-fired boiler houses; improvement of the reactivity of coals or to improve the technical and economic performance of heat-generating plants due to the fact that biomass is a waste from various types of production, and its cost depends only on the distance of its transportation to the boiler house. In this work, combustion of various biomass wastes, including sewage sludge, was carried out on a fire bench emulating the operation of a boiler furnace. Fuel particles were ignited by convective heat transfer in a stream of hot air at a velocity of 5 m/s in the temperature range of 500–800 °C, and the experimental process was recorded on a high-speed, color video camera. The obtained values were compared with the characteristics of different coals used in thermal power generation (lignite and bituminous coal). The aim of the work is to determine the reactivity of various types of biomass, including fuel mixtures based on coal and food waste. The work presents the results of technical and elemental analysis of the researched fuels. Scanning electron microscopy was used to analyze the fuel particle surfaces for the presence of pores, cracks and channels. It was found that the lowest ignition delay is characteristic of cedar needles and hydrolyzed lignin; it is four times less than that of lignite coal and nine times less than that of bituminous coal. The addition of hydrolysis lignin to coal improves its combustion characteristics, while the addition of brewer’s spent grain, on the contrary, reduces it, increasing the ignition time delay due to the high moisture content of the fuel particles. Full article

Hot-gas drum heating (HDH) of bituminous mixtures is a new approach to heating bituminous mixtures that is influenced by the parameters of the hot gas and drum. A fluid thermal numerical model was developed to evaluate the effects of heating bituminous mixtures with HDH using a finite-volume method (FVM). The FVM was verified through the heating test of a bituminous mixture. The effects of the drum rotating speed and hot-gas speed on the efficiency of heating the bituminous mixture during HDH were analyzed using Fluent. The results indicated that the drum rotating speed directly influenced the formation of a bituminous-mixture curtain, which had a significant effect on the efficiency of heating the bituminous mixture. The efficiency of the heat exchange between the hot gas and the bituminous mixture was high, with full contact between the hot gas and the bituminous mixture. With an increase in the hot-gas speed, the heating time became shorter; however, the rate of hot-gas utilization was reduced. A symmetrical temperature distribution and a superior heating efficiency of the bituminous mixture were achieved when the drum rotating speed was 7 rpm and the hot-gas speed was 1.4 m/s. Full article

The use of reclaimed asphalt pavement (RAP) in manufacturing asphalt concrete has become indispensable all over the world. This is due to the limited number of areas that are required to stockpile scraped pavement, as well as a lack of natural aggregate, which is necessary in manufacturing asphalt concrete. Thus, this research aims to evaluate the mechanical characteristics and environmental impact of using RAP and waste polyethylene in hot mix asphalt (HMA). RAP was added to hot mix asphalt in proportions of 25%, 50%, 75%, and 100% instead of the same amount of coarse aggregate. Then, the optimum RAP hot mix asphalt was modified by adding polyethylene in proportions of 1%, 2%, 3%, and 4% into the hot mix asphalt. The Marshall mix design was used to define the optimum asphalt content. As a final point in this experimental work, tests on the loss of stability, indirect tensile strength, and wheel loading tracking were performed to assess the performance of asphalt mixes modified with RAP and polyethylene in different conditions. A life cycle assessment (LCA) was applied using the ReCipe 2016 Endpoint method to evaluate the environmental impacts of these mixtures using the SimaPro software, V9.1. The laboratory tests showed that the mixture containing 50% RAP instead of the same amount of coarse aggregate and 2% polyethylene recorded better Marshall characteristics than the control mixture and the mixture with RAP alone. Finally, the modified hot mix asphalt with added RAP and polyethylene not only achieved superior performance in rutting, water damage resistance, and the stiffness modulus of bituminous mixtures, but it has been verified that there is no serious risk to the environment. Full article

The rapid growth of the world population and the rapid diversification of consumption habits due to technological advancements have increased waste production. An investigation of the effects of biomass products, such as waste vegetable oil and waste agricultural ash, on bitumen’s physical and chemical properties was conducted in this study. By recycling biomass products, this study aimed to improve the performance and stability of bituminous hot mixtures, optimize the number of additives, and create more economical designs. Using the Taguchi method, 0%, 2%, 4% by weight of waste vegetable oil and 0%, 3%, and 6% by weight of waste agricultural ash were added to 70/100 penetration pure bitumen with an orthogonal array of L9. For 10, 20, and 30 min, modified bitumen samples were prepared at 170 °C, 180 °C, and 190 °C with a constant mixing speed of 3000 RPM. The samples were tested for penetration, softening point, flash point, rolling thin film oven (RTFOT), FTIR, and Marshall Design stability and flow. Based on the obtained performance statistics, 95% confidence levels were assigned to the predictions. The stability and softening point values decreased as the oil content increased, while flash and penetration values increased. With increasing ash content, stability, flash, and softening point values increased, and penetration values decreased. Compared to oil and ash additives, mixing temperature and time had relatively little effect on the modification process. Overall, the optimum parameter levels were 4% for oil, 0% for ash, 170 °C for temperature, and 10 min for time. Full article

In recent years, both dry and wet processes to include waste rubber (WR) in bituminous mixtures have had little success in Italy due to technical and economic reasons. However, the necessity to recycle this waste material and the increasing interest in low-noise emitting pavement is encouraging researchers and stakeholders to explore new solutions. In this context, a hot-mix asphalt (HMA) manufactured with polymer-modified bitumen and fine WR added through a dry method has been recently developed. This paper deals with the rheological characterization and modeling of this innovative HMA, in comparison with two reference mixtures, with ordinary polymer-modified bitumen and with an asphalt rubber binder produced through a wet process. The complex modulus was measured through uniaxial cyclic compression tests at different temperatures and frequencies. The Huet-Sayegh rheological model was used to simulate the experimental data. The results showed that the time-temperature superposition principle is valid, despite the presence of polymers and WR. The Huet-Sayegh model allows a good fitting of the dynamic modulus and loss angle data to be achieved. The viscous response of the mixture including polymer-modified bitumen and rubber powder is higher than the other HMAs, which is mainly associated with the nature of the modifiers, the binder content in the mix and the less severe short-term aging. Full article

This research effort is geared towards revealing the latent potential of discarded shoe polish that might be repurposed as an asphalt fluxing agent for the construction of durable and sustainable road surfaces. To drive this creative invention, the effect of various proportions of waste shoe polish (e.g., 5, 10 and 15 wt. % WSP) on the performance of base AP-5 bitumen was inspected in great detail. A meticulous investigation of the chemical, physical, and rheological properties of the resultant combinations was carried out using a variety of state-of-the-art laboratory techniques, specifically: thin-layer chromatography-flame ionization detection (TLC-FID), Fourier transform-infrared spectroscopy (FT-IR), needle penetration, ring-and-ball softening point, Brookfield viscometer, ductility, flash/fire points, dynamic shear rheometer (DSR), multiple stress-creep recovery (MSCR), and bending beam rheometer (BBR) tests. The Iatroscan data disclosed that the continuous feeding of binder with WSP had a minor impact on SARA fractional distribution, regardless of aging. According to the FT-IR scan, the stepwise addition of WSP to the binder did not result in any significant chemical alterations in the blends. The combined outcomes of the DSR/BBR/empirical test methods forecasted that the partly bio-sourced additive would greatly improve the mixing–compaction temperatures, workability, and coating–adhesion properties of bituminous mixtures while imparting them with outstanding anti-aging/cracking attributes. In short, the utilization of waste shoe polish as a fluxing agent for hot asphalt mix production and application is not only safe, feasible, and affordable, but it has the potential to abate the pollution caused by the shoe-care market while simultaneously enhancing the overall performance of the pavement and extending its service lifespan. Full article

Concerns about the environment, the cost of energy, and safety mean that low-energy cold-mix asphalt materials are very interesting as a potential replacement for present-day hot mix asphalt. The main disadvantage of cold bituminous emulsion mixtures is their poor early life strength, meaning they require a long time to achieve mature strength. This research work aims to study the protentional utilization of waste and by-product materials as a filler in cold emulsion mixtures with mechanical properties comparable to those of traditional hot mix asphalt. Accordingly, cold mix asphalt was prepared to utilize paper sludge ash (PSA) and cement kiln dust (CKD) as a substitution for conventional mineral filler with percentages ranging from 0–6% and 0–4%, respectively. Test results have shown that the incorporation of such waste materials reflected a significant improvement in the mixture’s stiffness and strength evolution. The cementitious reactivity of PSA produces bonding inside the mixtures, while CKD is used as an additive to activate the hydration process of PSA. Therefore, based on the results, it will be easier to build cold mixtures by shortening the amount of time needed to reach full curing conditions. Full article

The incorporation of reclaimed asphalt (RA) in hot mix asphalt mixtures is widely considered a sustainable solution for road infrastructure development. Under the scope of the circular economy (CE), the multiple recycling capability of RA has to be assessed in order to ensure its performance at each recycling cycle and also its viability with different additives. The performance of asphalt mixtures with RA strongly depends on the type of rejuvenator, binder, and their degree of blending in the mix. For this reason, it is essential to know the properties of the aged binder extracted from RA to better understand its rheological properties and optimal dosage of rejuvenation to design a satisfactory blend design for the recycled mixture. To analyse the multi-recycling potential of the recycled mixture with high RA content, it is imperative to study its characteristics at every recycling cycle. Therefore, in this study, a preliminary binder-scale study is carried out to better understand the ageing, rejuvenating effects and morphological changes that occur on the bituminous binders at every recycling cycle. The study has been conducted on a RA binder, extracted from RA from a rural road in Italy and the simulation of multiple recycling is conducted through a laboratory ageing protocol on both binder and asphalt mixture scales. The long-term binder level ageing is performed by a pressure ageing vessel (PAV) after the short-term ageing by the rolling thin film oven test (RTFO). The asphalt mixture ageing is performed through a protocol similar to the National Cooperative Highway Research Program (NCHRP) and the aged binder is extracted from the mixture for further investigations. Multiple recycling is simulated by repeating the ageing procedure after rejuvenating both the aged binder and aged mixture up to the amount of recycling needed for the study. The rheological properties of the aged binder obtained from both binder-scale and mixture-scale ageing methods are evaluated using a dynamic shear rheometer (DSR) and bending beam rheometer (BBR). Moreover, the morphological changes that occurred are analysed using SARA (saturates, aromatics, resin and asphaltenes) fractionation and atomic force microscopy (AFM). The results of the study can help towards answering the uncertainties regarding the performance of high RA% in asphalt mixtures and establishing its viability in multi recycling towards the full-scale implementation of this sustainable approach. Full article

This investigation is dedicated to unlocking the hidden potential of discarded cosmetics towards building green sustainable road pavements in the future. It is particularly aiming at exploring waste lipstick (WLS) as a high-quality functional additive for advanced asphalt mix technologies. To fuel this novel innovation, the effect of various WLS doses (e.g., 5, 10, and 15 wt.%) on the performance of base AP-5 asphalt cement was studied in detail. A wide array of cutting-edge analytical lab techniques was employed to inspect in-depth the physicochemical, microstructural, thermo-morphological, and rheological properties of resultant admixtures including: elemental analysis, Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thin-layer chromatography-flame ionization detection (TLC-FID), scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), needle penetration, ring and ball softening point, Brookfield viscometer, ductility, and dynamic shear rheometer (DSR) tests. Unlike the unstable response of asphaltenes, the additive/artificial aging treatments increased the fraction of resins the most, and decreased that of aromatics; however, asphaltenes did not impair the saturates portion, according to Iatroscan research. FT-IR scan divulged that the WLS-asphalt interaction was physical rather than chemical. XRD diagnosis not only revealed an obvious correlation between the asphaltenes content and the fresh-binder crystallinity but also revealed the presence of fillers in the WLS, which may generate outstanding technical qualities to bituminous mixes. According to AFM/SEM analyses, the stepwise incorporation of WLS grew the magnitude of the “bee-shaped” microstructures and extended the roughness rate of unaged/aged binders. The prolonged consumption of the high thermal-stable additive caused a remarkable drop in the onset degradation and glass transition temperature of mixtures, thus enhancing their workability and low-temperature performance, according to TGA/DTGA/DSC data. The DSR and empirical rheological experiments demonstrated that the WLS could effectively lower the manufacturing and compaction temperatures of asphalt mixes and impart them with valuable anti-aging/fatigue-cracking assets. In a nutshell, the use of waste lipstick as an asphalt modifier is viable and cost-effective and could attenuate the pollution arisen from the beauty sector, while improving the performance of hot/warm asphalt mixes (HAM/WAM) and extending the service life of roadways. Full article

This study evaluates the influence of polymer-modification on the induction heating capability of asphalt mastic in a microwave field, and investigates how effectively this approach can be utilized for ice melting and self-healing purposes. To this end, different asphalt mastic mixtures with different polymer-modification and mixing procedures were tested under microwave field exposure for induction heating capability, ice-melting ability, and self-healing capacity. The mixtures were made through warm-mix and hot-mix procedures with four bituminous binders, including virgin (unmodified) asphalt and the same binder modified with three types of polymers. The results showed the effectiveness of microwave induction heating of asphalt mastic for both crack-healing and deicing purposes. The binder type was found to influence the ice melting and crack healing rates, such that using a warm-mix asphalt binder resulted in a more efficient heat generation and conduction than using a virgin asphalt binder. While polymer-modification undermined induction-heating, ice-melting, and self-healing performances, SBS-modified asphalt binders exhibited better performance than the other polymer-modified binders. Full article

This study investigated the viability of quantifying the affinity between aggregate and bitumen by means of different imaging techniques. Experiments were arranged in accordance with the rolling-bottle test, as indicated in UNI EN 12697-11, “Test methods for hot bituminous conglomerates—Part 11”. Digital image processing (DIP) techniques have only recently been used for such quantification. The data gathered with a multi-sensor optical platform equipped with VIS–NIR and SWIR spectrometers were compared with DIP outcomes. Data were processed using the unsupervised ISODATA and the supervised parallelepiped algorithms. The exposed aggregate index (EAI) and the bitumen index (BIT) were calculated to retrieve the bitumen percentage coverage of different mixtures. The comparison with the results obtained employing the traditional 6, 24, 48 and 72 testing hours reveals the possibility to implement a standardized analysis methodology combining digital and hyperspectral imagery to highlight potential inaccuracies deriving from the visual interpretation. Full article