Stone Matrix Asphalt Research Articles

Investigations on Stone Matrix Asphalt Mixes Containing Recycled Concrete Aggregate Treated with Nanosilica

The present work is an attempt to explore use of recycled concrete aggregate (RCA) to replace natural aggregates (NA) in a sustainable way in stone matrix asphalt (SMA) mixes used as a rut resistant bituminous layer. Based on several initial trials, a modified pretreatment procedure has been developed, which involves mixing of RCA with 8% (by weight) nanosilica modified bitumen emulsion solution followed by 24-h curing. The treated RCA (TRCA) has been used as coarse aggregate completely replacing the coarse NA, with two different types of bitumen namely, VG 30 and VG 40 bitumens for preparation of SMA mixes. Marshall method was used to determine optimum bitumen content (OBC) of the respective mix type. The pertinent performance characteristics such as stone-on-stone contact, drain-down, Marshall parameters, indirect tensile strength, moisture susceptibility, resilient modulus and rutting potential have been addressed for various SMA mixes prepared at respective OBCs. It is concluded that TRCA as aggregate and VG 40 bitumen as binder in SMA mix contributed to the best results in terms of various performance parameters considered.

Rheological behavior of asphalt binders and fatigue resistance of SMA mixtures modified with nano-silica containing RAP materials under the effect of mixture conditioning

Due to the environmentally associated issues regarding the construction or rehabilitation of asphalt pavements with merely virgin materials, researchers have proposed the re-utilization of the reclaimed asphalt pavement (RAP) materials. However, their adoption in asphalt pavements is detrimental to the fatigue performance of asphalt pavements. For this, modifying asphalt binders with nanoparticles has been one of the successful choices among researchers. In this study, different compounds of asphalt binders and stone matrix asphalt (SMA) mixtures containing 20%, 30%, 40%, and 50% RAP materials modified with 2%, 4%, and 6% nano-silica were prepared. Moreover, the rheological behavior of each mix was evaluated using several tests, including rotational viscosity (RV) considering the flow activation energy (FAE) method, frequency sweep, Multiple Stress Creep Recovery (MSCR), Linear Amplitude Sweep (LAS), and Bending Beam Rheometer (BBR). Besides, the fatigue performance of aged SMA mixtures was investigated using the four-point beam fatigue (4 PB) test. The results indicated that the temperature susceptibility of binders was decreased by the addition of nano-silica and RAP binder. Also, according to the MSCR and frequency sweep tests results, the rutting resistance of modified binders with the RAP binder was superior to that of the base binder. Besides, due to the establishment of a network by nano-silica within the structure of the asphalt binder in which the functional groups of asphalt binder interact with nanoparticles, the modified binders with RAP binder outperformed their unmodified counterparts regarding the fatigue life. Also, aging had a less detrimental impact on the fatigue life of the RAP contained SMA mixtures. However, the low-temperature performance of binders was degraded by the addition of nano-silica.

Why do clogged porous asphalt pavements give better traffic noise reduction than a dense-graded asphalt pavement?

In Europe, porous asphalt concrete pavements (PAC) are commonly used to reduce traffic noise. Especially the double-layer type (DPAC) provides substantial traffic noise reduction. Unfortunately, PAC pavements compared to dense asphalt pavements have reduced acoustic longevity; the main reason being clogging of the pores and voids, sometimes also more ravelling. The dense-graded pavements considered here are stone mastic asphalts (SMA, in the US known as stone matrix asphalt) which often have surface macrotexture of the same size as the PAC. The main difference is that the PAC has accessible pores/voids providing sound absorption, while the SMA has practically no porosity. One would expect that when the pores in the PAC have become clogged while ravelling is not yet substantial, that the noise property of the PAC would approach that of the SMA. But experimental studies suggest that even when PAC:s are effectively clogged, they retain a certain noise reduction compared to SMA:s. This paper examines this feature of clogged PAC versus SMA and reasons for this unexpected property, for a few Swedish DPAC pavements compared to SMA pavements, with due consideration of possible difference in maximum aggregate size and macrotexture as represented by mean profile depth (MPD) and grading curves.

Properties of Stone Matrix Asphalt Modified with Polyvinyl Chloride and Nano Silica.

In this study, the effects of polyvinyl chloride (PVC) and nano silica (NS) as modifiers on the properties of stone matrix asphalt (SMA) were studied. The experiment was performed with five modes: 1% NS was mixed into SMA; 5% PVC was mixed into SMA; and the ratio of NS was changed (1, 2, and 3%) with 5% PVC being mixed into SMA. The properties of modified and unmodified SMA materials were determined and compared by performing the penetration test, softening points test, viscosity measurements, dynamic shear rheometry, and multiple stress creep recovery under aging conditions. Moreover, the properties of the modified SMA were also determined in terms of Marshall stability, water stability, and rutting resistance. The obtained results indicate that the physical properties of SMA materials could be significantly improved by using a combination of PVC and NS as a modifier. Moreover, the SMA mixtures modified with PVC and NS exhibited high Marshall stability, good moisture damage resistance, and rutting resistance. Modified SMA mixtures with 5% PVC and 1% NS exhibited the best quality. This research has opened up a new avenue for the development of effective additives for SMA materials.

Performance Evaluation of Stone Matrix Asphalt (SMA) Mixes Using Different Types of Fibers as Additives. (Dept. c)

Stone matrix asphalt (SMA) is a gap graded hot mix asphalt (HMA) which gains its main strength from stone on stone contact. It provides a rut-resistant, durable surfacing material which is suitable for heavily trafficked roads. Typical SMA consists of 70-80 % coarse aggregate, 8-12 % mineral fillers, and 6-7 % binder. Due to this high binder content, stabilizing additives are needed to prevent draindown that might occur during transport and placement. According to SMA standards, cellulose and mineral fibers are the most suitable stabilizing additives to be used in SMA, but due to lack of those specific types of fibers in some countries, another types of fibers are being tested to replace them in the mix. The main objective of this study is to investigate the characteristics of SMA mixtures using fiberglass as a stabilizing additive. Another SMA mix of the best result was prepared using polypropylene fiber instead of fiberglass and tested for comparison purposes. Two different SMA gradations were tested, nominal maximum aggregate size (NMAS) 12.50 mm and NMAS 19.00 mm at four different fiber contents for each gradation 0.00 %, 0.30 %, 0.50 %, and 0.70 % by total weight of the mix. SMA samples were tested through series of performance tests selected to be Marshall stability test, moisture susceptibility test, indirect tensile strength test (ITS), and draindown test.

Coir fiber as a sustainable material in pavement construction.

ABSTRACT
 Traffic is increasing day by day due to increased vehicle ownership and infrastructure development. As the modern highway transportation has high speed, high traffic density, heavy load and channelized traffic, bituminous concrete is subjected to various types of distress such as rutting, fatigue cracking and raveling. Fatigue cracking occurs because bituminous layers are weak in tension. Therefore reinforcement of the bituminous mixes is one approach to improve tensile strength. Natural fibers can be used for reinforcing as a substitute for synthetic fibers due to their lower cost, ecological recycling and low specific gravity. Among natural fibers growing attention is being paid to coir fiber due to its easy availability, good wearing resistance and more durable property. Also rutting along wheel path causes vehicle hydroplaning during rainy seasons due to loss of skid resistance. As well as water accumulated over the longitudinal depressions damages bond between binder and aggregates. Therefore there is a need for a durable mix which can increase the service life of pavement thus reduces life cycle cost. This study is about use of coir fiber in pavement construction to improve the performance characteristics of the asphalt mixture being used. Stone matrix asphalt mixture is a rut resistant and durable mix which is reinforced with coir fiber and tested for various performance characteristics. Coir fiber is a sustainable material which can be used for rutting resistant mixture.
 Keywords: Stone matrix asphalt, Coir fiber, rutting

Investigation of the Effect of Crumb Rubber Powder and Warm Additives on Moisture Resistance of SMA Mixtures

Stone matrix asphalt (SMA) mixtures are one of the most resistant types of asphalt mixtures known to date that the bulk load is borne by the aggregate skeleton. In this research, the effect of crumb rubber powder (CRP), Vestenamer polymer, and warm additives, including Sasobit, ZycoTherm, and a porous and warm mix asphalt (PAWMA), was investigated on the moisture resistance of SMA mixtures. A segregation test was performed to determine the tendency of the polymer to separate from modified polymer bitumen under storage conditions. Also, a drain down sensitivity test was conducted to explore the bleeding phenomena and drain down of SMA mixtures. Finally, a boiling water test, as well as an indirect tensile strength (ITS) test, was applied to examine the sensitivity of mixtures to moisture. The segregation test results indicated that by the use of Vestenamer polymer, a conventional (low speed) mixer can be used instead of using a high-speed mixer, and this will be very important in the cost of rubber bitumen production. The drain down test results showed that cellulose fibers prevented the bitumen bleeding of SMA mixtures. Also, the results of the boiling water test indicated that CRP samples containing ZycoTherm had the highest moisture resistance compared to the other warm additives. Among various mixtures, 8% CRP-modified samples containing ZycoTherm resulted in the lowest amount of stripping in SMA mixtures, even more than the base sample. The ITS test results illustrated that the use of CRP, Vestenamer polymer, and warm additives had a significant effect on the ITS amounts of mixtures. Moreover, the samples containing ZycoTherm had the highest tensile strength ratio (TSR) compared to the other SMA samples.

Comprehensive Study about Effect of Basalt Fiber, Gradation, Nominal Maximum Aggregate Size and Asphalt on the Anti-Cracking Ability of Asphalt Mixtures

There are many parameters that could affect the properties of asphalt mixtures, such as the fiber additive, gradation type, nominal maximum aggregate size (NMAS), and asphalt. To evaluate the influence of these factors on the crack resistance of asphalt mixture, 10 different types of asphalt mixtures were prepared. The indirect tensile asphalt cracking test (IDEAL-CT) and semi-circle bending test (SCB) were adopted to test the anti-cracking ability of the test samples. The parameters of these two test results were also used to conduct the correlation analysis to find the correlation between different parameters, and scanning electron microscope (SEM) test was also used to analyze the micro cracks of asphalt mixture. The results showed that basalt fiber could further enhance the anti-cracking ability of asphalt mixture. Stone matrix asphalt (SMA) showed better anti-cracking performance than Superpave (SUP) asphalt mixtures. The increase in the nominal maximum aggregate size could decrease the anti-cracking ability of asphalt mixtures. Styrene-Butadiene-Styrene (SBS) modified asphalt could better reinforce the anti-cracking ability than pure asphalt. The CTindex of IDEAL-CT test and Flexibility index (FI) value of SCB test results showed better correlation. This paper has certain significance in guiding the design of asphalt mixtures having good crack resistance.

Application of rubber dust in modified asphalts for SMA mixtures

Abstract: The experimental investigation described in the paper refers to the properties of asphalts and asphalt mixtures with addition of rubber wastes. The influence of rubber additive, on rheological properties, viscosity, penetration, softening point of the asphalts were analyzed. An innovative technique based on the combined use of microscopic observations was developed. Tests results were compared to the conventional asphalts. Positive effects of modification were recorded. Two types of asphalt mixtures were prepared on the same mineral aggregate. For reference a Stone Matrix Asphalt (SMA) was used with polymer modified (PM) asphalt 45/80-55. Then the Stone Matrix Asphalt was prepared on the base of asphalt-rubber (45/80-55 AR). These materials were tested on rutting and water and frost resistant. The results indicated that the SMA mixtures prepared on the base of rubber modified asphalt exhibit greater resistance to permanent deformation, at elevated temperatures and greater water and frost resistance than the conventional SMA mixtures. Tests results were compared to technical requirements for SMA layers. It was found that this type of asphalt mixture can be successfully used in road surfaces, especially exposed to freezing. Keywords: Asphalt mixture; SMA mixture; rubber asphalt; Recycling; Dynamic viscosity.

Investigation of the performance properties of asphalt binders and mixtures modified by Crumb Rubber and Gilsonite

The mechanical performance properties of asphalt binders and mixtures can be enhanced by utilizing several modifiers, including Crumb Rubber (CR) and gilsonite. The current study evaluated the effects of CR and gilsonite additive on the rheological behavior of gilsonite and CR/gilsonite composite modified binders and Stone Matrix Asphalt (SMA) mixtures. In this research, to modify original binder, gilsonite (0%, 10%, 20%, 30% and 40% by weight of binder), and CR (5%, 10%, 15%, and 20% by weight of binder) were used. The modified binders were subjected to rotational viscosity (RV), dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), and linear amplitude sweep (LAS) tests. Also, the gilsonite and CR/gilsonite modified mixtures were subjected to four-point beam fatigue (FPBF), resilient modulus (Mr), indirect tensile strength (ITS), dynamic creep, and wheel track tests. The results revealed that the utilization of gilsonite reduced the low temperature cracking resistance of binders while adding CR to gilsonite modified binders, the low-temperature cracking of modified binders enhances. According to the results, utilization of gilsonite causes a decrease in the resistance of binders against fatigue cracking, while adding CR to gilsonite modified binders, the fatigue life of binders increases. Results revealed that both gilsonite and CR enhance the elasticity and recovery properties of binders, and consequently, the strength of binders versus permanent deformation improves. Mixture test results revealed that using gilsonite and CR increases the Mr, permanent deformation resistance, tensile strength, fracture energy, and intermediate temperature performance of specimens. It can be concluded from the results that CR has a positive impact on enhancing the gilsonite modified binders and mixtures performance.

The Effect of the use of Gypsum Waste as a Filler Substitution on Stone Matrix Asphalt Coarse

This research is intended to test the use of gypsum waste as a cement filler substitution in a mixture of coarse stone matrix asphalt (SMA). The methodology in this research is to conduct a series of tests for the characteristics of coarse, fine, and filler aggregates, then design the composition of the coarse Stone Matrix Asphalt (SMA) mixture as well as Marshall immersion testing to obtain the remaining Marshall Stability. The results of research conducted at the Road and Asphalt Laboratory of the Faculty of Engineering, Department of Civil, Indonesian Christian University, Paulus Makassar, through the Marshall immersion test obtained a mixture of rough Stone Matrix Asphalt (SMA) with the proportion of gypsum waste as cement filler substitution, namely 100%: 0%, 75%: 25%, 50%: 50%, 25%: 75%, 0%: 100% meets the requirements issued by the Directorate General of Highways of the Ministry of Public Works of the Republic of Indonesia, General Specifications 2018. Test results for Marshall Immersion mixture of Stone Matrix Asphalt (SMA) coarse in all proportions of gypsum waste to obtain Marshall Stability Time meet the limit requirements, namely ≥ 90% so that the mixture is resistant to immersion in water.

Characteristics of the Stone Matrix Asphalt Coarse using the Tabu River Stone North Toraja Regency

The purpose of this research is to make use of Tabu River’s stones as a Stone Matrix Asphalt (SMA) mixture. The methodology used in this research is to do multiple inspections and examining characteristics of course, fine, and filler aggregates and devise a mixture composition of Stone Matrix Asphalt. The Marshall testing method was used to determine the mixture characteristics and Marshall Immersion Testing to ascertain Immersion Index (IP) / Residual Strength Index (IKS) / durability of the mixture with optimum asphalt content. The research was done at Road and Asphalt Laboratorium, Department of Civil Engineering, Christian University of Indonesia, Makassar, Indonesia. The research demonstrated that the composition of aggregates produced by Tabu River’s Stones at Tikala Sub-District fulfills the specifications of Bina Marga 2018 as a paving material. Marshall Examination showed the characteristic mixture of Stone Matrix Asphalt with asphalt levels of 6.00%, 6.25%, 6.75%, 7.00%. The Marshall Immersion Examination determined that the optimal asphalt level of 7.00% with an immersion index (IP)/Residual Strength Index (IKS)/Durability as high as 95.05% satisfies the Bina Marga 2018 requirements of at least 90%.

Feasibility of 9.5-mm Stone Matrix Asphalt for Thin Lift Overlays in Washington State

Due to budget constraints, highway agencies tend to use thin lifts as a primary rehabilitation strategy. The construction of a thin lift requires a small nominal maximum aggregate size (NMAS), e.g., 9.5 mm or smaller. However, hot-mix asphalt (HMA) with a small NMAS is prone to rutting and/or studded tire wear. Stone matrix asphalt (SMA) is a gap-graded asphalt mixture with interlocking aggregate that enhances the mixture’s mechanical properties compared with HMA, especially with regard to resistance to both rutting and studded tire wear. Therefore, SMA mixes with a small NMAS may provide a viable solution to these distress types. Few studies have evaluated the performance of small NMAS SMA for thin overlays, especially for high levels of studded tire traffic. To address this gap in the literature, this study assessed the laboratory performance of 9.5-mm NMAS SMA compared with that of commonly used 12.5-mm NMAS SMA and 9.5-mm NMAS HMA mixtures to determine the feasibility of using 9.5-mm NMAS SMA in thin lift overlays subjected to heavy traffic in the State of Washington, where the use of studded tires is widespread in winter. Three types of mixtures were tested for their resistance to bottom-up fatigue cracking, top-down fatigue cracking, thermal cracking, rutting and moisture susceptibility, and studded tire wear. The resistance to top-down fatigue cracking of the 9.5-mm SMA was comparable to that of the 9.5-mm HMA and the 12.5-mm SMA. The 9.5-mm HMA and 9.5-mm SMA had comparable resistance to bottom-up fatigue cracking and performed better than the 12.5-mm SMA. Both the 9.5-mm HMA and the 9.5-mm SMA had better thermal cracking resistance than the 12.5-mm SMA. The 12.5-mm SMA had better rutting and moisture susceptibility resistance than the 9.5-mm SMA and 9.5-mm HMA. Both the 9.5-mm SMA and 12.5-mm SMA had comparable resistance to studded tire wear and performed better than the 9.5-mm HMA. Overall, the results showed that 9.5-mm NMAS SMA is a viable material for thin-lift overlays, outperforming 9.5-mm NMAS HMA in terms of resistance to rutting, moisture, and studded tire wear. Further studies are needed to assess the field performance, constructability, and life-cycle costs of 9.5-mm SMA.

Shear Fatigue Performance of Epoxy Resin Waterproof Adhesive Layer on Steel Bridge Deck Pavement

In this study, the effects of temperature, shear stress, and coating quantity of waterproof adhesive layer on the shear fatigue performance of a steel bridge deck pavement were investigated. Direct shear fatigue tests of a pavement comprising an epoxy resin waterproof adhesive layer with stone matrix asphalt were conducted at different temperatures, stress levels, and coating quantities. The results show that temperature and stress have significant effects on the shear fatigue life. With increasing temperature and stress, the shear fatigue life of the waterproof adhesive layer decreased gradually. Therefore, for steel bridge deck pavements under high temperatures and heavy loads, the use of asphalt waterproof adhesive layers or pavement layers should be evaluated carefully while limiting the traffic of heavily loaded vehicles. Shear failure occurs at the waterproof adhesive layer–pavement interface and not at the steel–waterproof adhesive layer interface. The shear strength of the epoxy resin waterproof adhesive layer is mainly provided by the bond strength between the waterproof adhesive and pavement mixture as well as the interlocking force between the cured epoxy resin and the bottom interface of uneven pavement mixture. The shear strength increases with the coating quantity of the waterproof adhesive layer; however, after reaching the maximum value, the shear strength becomes stable. In contrast, the interlaminar shear fatigue life increases continuously with the coating quantity of the waterproof adhesive layer. Appropriately increasing the coating quantity is beneficial for improving the resistance of the waterproof adhesive layer to interlaminar shear fatigue failure.

Laboratory investigation of the performance of binders and asphalt mixtures modified by carbon nano tube, poly phosphoric acid, and styrene butadiene rubber

This study evaluated the performance characteristics of binders and Stone Matrix Asphalt (SMA) Mixtures modified by Poly Phosphoric Acid (PPA), Carbon Nano Tube (CNT), and Styrene Butadiene Rubber (SBR). In order to investigate the rheological behavior of bitumens, linear Amplitude Sweep (LAS), rotational viscosity, Dynamic Shear Rheometer, Bending Beam Rheometer, Multiple Stress Creep Recovery (MSCR), and storage stability tests were implemented. Moreover, Resilient modulus (Mr), Indirect tensile strength (ITS), dynamic creep, wheel track, and Four-Point Beam Fatigue (FPBF) tests were performed to investigate the properties of asphalt mixtures. LAS and MSCR tests result revealed that the addition of SBR/PPA and CNT leads to improved fatigue life and rutting properties of binders at both strain levels. Additionally it was found that modification of SBR/PPA with 85–100 binder enhances the intermediate temperature behavior of bitumens. The results indicate that the addition of SBR/PPA enhances the Mr, rutting properties, ITS, fracture energy, and fatigue performance of specimens. By increasing the CNT contents, the rutting behavior improves.

Evaluation of the Influence of Antistripping Agents on Water Sensitivity of the Stone Matrix Asphalt Mixture Modified by Recycled Ground Tire Rubber and Waste Polyethylene Terephthalate

This research intends to evaluate the effects of the waste polyethylene terephthalate (PET), antistripping agents (ASA), and ground tire rubber (GTR) on the performance properties of the stone matrix asphalt (SMA) mix binder/water damage resistance. Liquid antistripping agents, added to 85/100 penetration grade binder to evaluate the ASA effects, were A (M500), B (EvothermM1), and C (LOF‐6500). Tests conducted to study the modified bitumen’s rheological properties included softening point, penetration, rotational viscosity (RV), and dynamic shear rheometer (DSR), and tests performed in order to examine the moisture sensitivity of the modified mix were the Texas boiling and resilient modulus (MR), fracture energy (FE), and indirect tensile strength (ITS) ratio tests. Results showed that the MR, ITS, and FE of asphalt mixes modified with crumb rubber (CR), ASA, and PET were improved. Adding 50% PET, 50% CR, and ASA (B) led to the highest tensile strength, resilient modulus, and fracture energy ratios showing a perfect water susceptibility of the mentioned mix.

Avaliação do escorrimento e da resistência à tração na compressão diametral de uma mistura tipo SMA com adição de cal cálcica e fibra de vidro tipo E

Com a crescente demanda por estruturas que suportam elevados volumes de tráfego, excesso de carga, melhor desempenho e menor necessidade de intervenções para reparos ou manutenções, é necessário que novos materiais sejam estudados ou desenvolvidos para sanar tais necessidades. Dentre as misturas asfálticas usinadas a quente, pode-se destacar a Stone Matrix Asphalt (SMA) que foi desenvolvida e melhorada ao longo do tempo para atender rodovias com pesado volume de tráfego. Neste trabalho, foram analisados os efeitos da adição da cal hidratada sobre a resistência à tração da mistura SMA e o efeito da utilização da fibra de vidro tipo E na mitigação do escorrimento do ligante betuminoso. Utilizou-se ligante asfáltico modificado por polímero (CAP 60/85-E), fibra de vidro tipo E, areia artificial, agregado basáltico e cal. Os corpos de prova foram submetidos aos ensaios para definição dos parâmetros Marshall, ensaio de escorrimento (Schellemberg) e resistência à tração por compressão diametral. O teor de ligante foi fixado em 7% devido aos resultados obtidos nos parâmetros Marshall. No ensaio de escorrimento foi observado teor adequado para a mistura com 0,5% fibra de vidro. Já no ensaio de resistência à tração foi constatada perda de resistência do teor de 1,5% de cal quando comparado a 1%, entretanto ambos percentuais apresentaram resistência superior ao prescrito pela ET-DE-P00/031.

The effects of gilsonite and crumb rubber on moisture damage resistance of stone matrix asphalt mixtures

The current study was performed to investigate the influence of gilsonite on properties of binder and moisture resistance of SMA mixtures modified by Crumb Rubber (CR) additive. For this purpose, softening point, penetration, and Dynamic Shear Rheometer tests were implemented to investigate the performance of different binders. To evaluate the water sensitivity of modified mixtures, four different methods were performed, including Resilient Modulus Ratio (RMR), Fracture Energy Ratio (FER), Tensile Strength Ratio (TSR) and Texas boiling. To analyze the data, two-factor analysis of variance (ANOVA) was carried out. Based on the results, utilization of Gilsonite additive enhances the Resilient Modulus (Mr), Indirect Tensile Strength (ITS), and Fracture Energy (FE) of asphalt mixtures. The results also revealed that by utilization of CR, ITS and FE values increase. While, the MR values increase by addition of 10% CR, and by addition of higher percentages of CR (15 and 20%), the MR values decrease. Among different specimens fabricated, mixtures containing 30% Gilsonite and 20% CR have the highest ITS and FE values. Also, according to the results, 30% Gilsonite mixture modified by 20% CR has the highest TSR, and FER value, which indicates that the mentioned specimens have better resistance to water susceptibility.

Effects of anti-striping agents on performance of binder and stone matrix asphalt (SMA) mixtures containing polyphosphoric acid/styrene-butadiene rubber composite polymer blends and warm mixture additives

This work evaluated the effect of Anti-Stripping Agents (ASAs) on performance behavior of bitumen and high and intermediate temperature performance of SMA mixtures modified by Poly Phosphoric Acid (PPA), Warm Mix Asphalt (WMA) and Styrene-Butadiene Rubber (SBR) additive. Through this paper, the AC-60/70 and AC-85/100 penetration grade bitumens were used as base bitumen. Moreover, three liquid ASAs (ASA (1), ASA (2), ASA (3)), PPA (1% by weight of bitumen), SBR (2% by weight of binder), and two types of warm mix additives (3% Sasobit and 0.3% Zycotherm) were used as a mixture modifier. For evaluating the performance behavior of bitumen, the rotational viscosity, Dynamic Shear Rheometer, and Bending Beam Rheometer, Multiple Stress Creep Recovery (MSCR), and linear Amplitude Sweep (LAS) tests were implemented. Moreover, Resilient Modulus (Mr), Indirect Tensile Strength (ITS), dynamic creep, wheel track, and Four-Point Beam Fatigue (FPB) tests were performed to investigate the performance of mixture samples. Based on the outcomes of the MSCR test, the utilization of SBR/PPA additive and ASAs decreased the Jnr value. Among modified binders, the binders modified by ASA (2) have the lowest Jnr value followed by binders modified by ASA (1) and ASA (3). According to the outcomes of LAS test, the utilization of ASAs leads to increase in the fatigue life of the original binder. According to the outcomes, the utilization of WMA additives and ASAs caused the Mr, ITS, rutting resistance, and fatigue life to increase. Among ASAs, the ASA (2) has the greatest influence on enhancing the performance of mixtures. Based on results, Sasobit additive has a better effect than Zycotherm on enhancing the properties of samples.

Analysis of Long-Term Performance and Snowmelt Capacity of Anti-Freezing Asphalt Pavement

Abstract Anti-Freezing Asphalt Pavement (AFAP) has good snow-melting performance and is used widely in many countries around the world. The objective of this study was to analyze AFAP’s long-term performance and predict its snow-melting ability. Two types of anti-freezing stone matrix asphalt (SMA) mixtures (SMA-13 with Iceguard and SMA-13 with Mafilon) were prepared with the Marshall method. Water stability, high-temperature stability, low-temperature crack resistance, and freeze-thaw split tests were conducted to evaluate mixtures’ performance. Meanwhile, the effect of anti-freezing filler, asphalt content, and soaking temperature on the salt dissolution of anti-freezing asphalt mixtures was analyzed, and the snow-melting ability of AFAP was predicted based on the Back Propagation (BP) neural network. The results illustrated that water stability of anti-icing asphalt mixture reduced, and the dynamic stability after short-term aging was improved. The tensile strain and tensile strength ratio of the anti-icing asphalt mixture reduced after long-term aging and soaking in water. In addition, the salt dissolution rate increased with the increase of anti-freezing filler content and the decrease of asphalt content. The research conducted suggests that the BP Neural Network can be utilized to predict the snow-melting ability of the anti-freezing asphalt mixture, and the regression coefficient of the predicted and measured salt dissolution was higher.