Experimental assessment and modeling of static creep behavior of modified asphalt mixture with crumb rubber using gyratory compactor and Marshall method

This study investigates the impact of rubber on the creep compliance and creep modulus of asphalt mixtures, aiming to enhance their mechanical performance and promote environmental sustainability. Rubber was incorporated into the asphalt mixture using the dry process. Asphalt samples were prepared using different content of rubber both the gyratory compactor and the Marshall Method and tested at different temperatures. The results showed that adding a low percentage of rubber (0.25%) improved creep modulus and reduced deformation, while higher percentages led to decreased performance. Additionally, the study utilized advanced machine learning techniques, including Artificial Neural Networks (ANN) and Adaptive Neuro-Fuzzy Inference Systems (ANFIS), to model creep modulus and creep compliance. The ANFIS model demonstrated superior performance in predicting these properties compared to the ANN model. The findings of this research provide valuable insights into the influence of rubber on the creep behavior of asphalt mixtures and offer a robust framework for predicting their performance using machine learning techniques.

The benefits of crumb rubber modification of bituminous binder for asphalt mixture production is well established. Although most research has used high (20–30% by mass of the bitumen) crumb rubber dosages, there is now interest in low (5–15%) dosages for use in local road surfacing, where mechanical properties are less important. This paper quantifies the effects of low-dosage crumb rubber on the mechanical properties of a typical dense graded local road surface mixture. It was concluded that 5–10% crumb rubber dosage significantly increased the deformation (rutting) resistance and crack (fatigue) resistance of the asphalt. The effect of crumb rubber on mixture stiffness (modulus), moisture damage (stripping) resistance and workability (compactability) was mixed but was unlikely to present any practically important benefit or detriment. Consequently, 5–10% was concluded to be the preferred range of crumb rubber dosage for dense graded asphalt for local road surfacing.

Investigation of fatigue cracks on RAP mixtures containing Sasobit and crumb rubber based on fracture energy

Obtaining creep compliance parameters that accurately represent the creep response of asphalt mixtures is critical for proper evaluation of the thermal cracking performance, as well as load induced cracking performance of asphalt pavements. A power law, which uses three parameters to describe the creep compliance curve, is commonly used for asphalt mixtures. However, the specific values of the parameters obtained can depend on both the testing and the data interpretation methods used. Different testing methods (for example, static versus cyclic creep) offer different advantages and disadvantages related to complexity in testing, as well as in the sensitivity of the data obtained from each test to the compliance parameters of interest. In general, cyclic creep tests provide greater sensitivity and accuracy at shorter loading times, while static creep tests are more accurate and reliable for the determination of the long-term creep response.

Obtaining creep compliance parameters that accurately represent the creep response of asphalt mixtures is critical for proper evaluation of the thermal cracking performance, as well as load induced cracking performance of asphalt pavements. A power law, which uses three parameters to describe the creep compliance curve, is commonly used for asphalt mixtures. However, the specific values of the parameters obtained can depend on both the testing and the data interpretation methods used. Different testing methods (for example, static versus cyclic creep) offer different advantages and disadvantages related to complexity in testing, as well as in the sensitivity of the data obtained from each test to the compliance parameters of interest. In general, cyclic creep tests provide greater sensitivity and accuracy at shorter loading times, while static creep tests are more accurate and reliable for the determination of the long-term creep response.

This research has used crumb rubber in asphalt mixture as a part of the coarse and fine aggregate. Three sieve sizes of crumb rubbers were used in asphalt mixture No. 4, No. 8 and No. 50, with five percent of asphalt cements (4, 4.5, 5, 5.5 and 6%) by weight and four percent of crumb rubbers (10, 20, 30 and 40%) by weight used as an aggregate for preparing asphalt mixture specimens. The Hot Mix Asphalt (HMA) Marshal test method for asphalt mixture specimens was used; 72 specimens were prepared for evaluation of Marshall Properties (flow, Stability, bulk density, air void percentage and void in mineral aggregate). Previous studies showed that the crumb rubber has further effects on the performance of asphalt mixture by increasing its Marshall flow, stability, air voids and decreasing the bulk density. It is concluded that the crumb rubber as a fine aggregate improves the stability and flow with respect to a crumb rubber as a coarse aggregate.

Microstructure analysis and mechanical performance of crumb rubber modified asphalt concrete using the dry process

Crumb rubber for asphalt mixture modification can be used in two ways: incorporate to bitumen (wet process) or incorporate to aggregate (dry process) mixture before adding bitumen to mixer. Wet process has some disadvantages related to need of reasonable modification of asphalt plant. Dry modification process has more potential due to more simple technology and possibility to add higher quantity of crumb rubber comparing to the wet process. The performance of crumb rubber modified asphalt mixture mainly depends on several factors as crumb rubber type, content and rubber particles size. However, limited number of publications reported the results of dry process crumb rubber modified asphalt mixtures performance. This paper analyse the effect of different amount of crumb rubber on modified asphalt mixture air void content, water sensitivity and stiffness. Test results revealed the effect of crumb rubber and maximum recommended amount for asphalt mixture modification by dry process.

The development and production of high quality asphalt are crucial in the effort to meet current demands for the construction of roads. Crumb rubber is an industrial waste and one of the best ways to reduce the amount of this waste is by recycling it in the asphalt industry. Crumb rubber obtained from scrap tyres has been proven to be an effective additive for the modification of the properties of asphalt mixtures. This study presents a laboratory evaluation of the properties of crumb rubber modified asphalt mixture using the dry process method by adding three different sizes of crumb rubber, namely fine (≤1.18mm), coarse (≥1.18 but ≤3.35 mm), and combination of both fine and coarse (50/50), at three different percentages of crumb rubber, 0, 1.5 and 2.5% of the total weight of the aggregate. Crumb rubber was used to modify the dense graded mixture of asphaltic concrete wearing course 14 (ACWC14). The effect of crumb rubber in the mixture was investigated in terms of the volumetric properties using the Marshall Mix Design and mixture performance testing was conducted by means of resilient modulus, dynamic creep, and abrasion loss. Results showed that fine crumb rubber improved most of the properties of asphalt mixtures compared to other types of mixtures; this could be due to the partial interaction between rubber particles and bitumen which simultaneously act as an elastic aggregate in the mixture.

Adaptive Neuro-Fuzzy Inference System modelling for performance prediction of solar thermal energy system

Modeling the effects of ultrasound power and reactor dimension on the biodiesel production yield: Comparison of prediction abilities between response surface methodology (RSM) and adaptive neuro-fuzzy inference system (ANFIS)

In this paper, we evaluate the predictive performance of an adaptive neuro-fuzzy inference system (ANFIS) using six different membership functions (MF). In combination with a geographic information system (GIS), ANFIS was used for land subsidence susceptibility mapping (LSSM) in the Marand plain, northwest Iran. This area is prone to droughts and low groundwater levels and subsequent land subsidence damages. Therefore, a land subsidence inventory database was created from an extensive field survey. Areas of land subsidence or areas showing initial signs of subsidence were used for training, while one-third of inventory database were reserved for testing and validation. The inventory database randomly divided into three different folds of the same size. One of the folds was chosen for testing and validation. Other two folds was used for training. This process repeated for every fold in the inventory dataset. Thereafter, land subsidence related factors, such as hydrological and topographical factors, were prepared as GIS layers. Areas susceptible to land subsidence were then analyzed using the ANFIS approach, and land subsidence susceptibility maps were created, whereby six different MFs were applied. Lastly, the results derived from each MF were validated with those areas of the land subsidence database that were not used for training. Receiver operating characteristics (ROC) curves were drawn for all LSSMs, and the areas under the curves were calculated. The ROC analyses for the six LSSMs yielded very high prediction values for two out of the six methods, namely the difference of DsigMF (0.958) and GaussMF (0.951). The integration of ANFIS and GIS generally led to high LSSM prediction accuracies. This study demonstrated that the choice of training dataset and the MF significantly affects the results.

Viscoelasticity property of bitumen is closely related to the service life of bituminous pavement. This paper evaluated the impact of one of the most efficient and widely used nanomaterials in various industries called hydrophobic nanosilica on the viscoelasticity property of bitumen and asphalt mixture. In this paper, three hydrophobic nanosilica modified bitumens and asphalt mixtures were researched by conventional physical properties test, SEM test, FTIR test, DSC test, DSR test, static creep test and dynamic creep test. The results showed that the introduction of hydrophobic nanosilica could strengthen the viscosity of asphalt more effectively and had better dispersion than hydrophilic nanosilica in asphalt. From conventional physical properties test and rheological performance test, hydrophobic nanosilica could weaken the temperature susceptibility of bitumen observably. From DSR test, hydrophobic nanosilica modified asphalt had a lower sensitivity and dependence on temperature and frequency than hydrophilic nanosilica modified asphalt. The Cole–Cole diagrams indicated that hydrophobic nanosilica exhibited good compatibility with asphalt compared with hydrophilic nanosilica. Newly formed chemical bonds were found in the hydrophobic nanosilica modified asphalt and its mixture with stone according to SEM test, FTIR test, and DSC test, which is the biggest difference from the modification mechanism of hydrophilic nanosilica modified asphalt. Through static and dynamic creep test, it found that the addition of hydrophobic nanosilica can significantly reduce the creep strain at the same temperature.

The advancement of technology and the increasing growth of environmental threats have led experts in the field of transportation to find alternatives for hot mix asphalts (HMAs). One of these alternatives is low-energy asphalt (LEA) mixtures. LEA mixture consists of hot asphalt binder and coarse aggregates and wet sand, which, having a lower mixing temperature, has caused a significant reduction in energy consumption and pollutants emitted from asphalt binder. According to previous studies, the influence of crumb rubber (CR) on the rutting and moisture performances of LEAs has not been investigated so far. In this regard, due to the softness of this type of asphalt mixture and its weakness against rutting and moisture, in this study, as an innovation, CR was used to modify LEA mixtures in three weight percentages of 10, 15, and 20. Considering the high moisture sensitivity of LEA mixtures due to the presence of water, the ability of CR to overcome this weakness and its potential to be replaced with antistriping additives were also investigated using the indirect tensile strength (ITS) test. In addition, in order to evaluate the rutting resistance, LEA mixtures were subjected to the dynamic creep test at a temperature of 54.4°C and at two stress levels of 270 and 310 kPa. According to ITS test results, it was found that although the modified LEA mixtures with 10 and 15% CR met the minimum requirement, the tensile strength ratio (TSR) value recorded for mentioned mixtures was still lower than that for HMA. Therefore, it is recommended to use antistripping additives in the use of LEA-containing CR, especially in areas with a high probability of moisture damage. The results of creep curves and flow numbers (FNs) extracted from four different models of three-stage, Fnest, Francken, and stepwise showed that although the LEA sample without additive had lower rutting resistance than HMA, the modification of this mixture to 15% CR significantly increased the rutting resistance. Moreover, considering the variety of variables in the process of making LEA compared to HMA, the comparison of FN determination models and the introduction of the most stable model were conducted in this research. According to the laboratory and statistical analysis results, it was found that the Francken model had less sensitivity to the variables, so it is suggested to determine FN for LEA mixtures.

One of the ways to modify bitumen and asphalt mixture characteristics is to use recycled Crumb Rubber (CR). Although using CR improves the mechanical properties of asphalt mixtures and rheological behavior of bituminous binders, it increases binder viscosity. Warm Mix Asphalt (WMA) is a practical technology to ameliorate the disadvantage of Rubberized-Asphalt (RA) mixtures. This study aimed to investigate the effect of zeolite as a WMA additive on Hot Mix Asphalt (HMA) and RA mixtures. These modifiers' effect on the properties of asphalt mixtures and binders was studied utilizing different tests such as resilient modulus, indirect tensile fatigue, dynamic creep, moisture susceptibility (TSR and RMR), and rotational viscosity (RV). The findings indicate that the addition of zeolite and CR improved mechanical properties. 16% CR along with 6% zeolite is the optimum dosage to enhance durability. Moreover, the addition of CR to mixtures without zeolite decreased the TSR, RMR, and workability of mixtures, while zeolite increased the durability and workability of HMA and RA mixtures. The cost-effective analysis results also indicated that not only does the simultaneous proper use of zeolite and CR decreases energy consumption, but it also decreases the production cost of modified asphalt mixture.