Effects of Asphalt Binder Modifying with Polypropylene on Moisture Susceptibility of Asphalt Mixtures with Thermodynamically Concepts

In this study, the effect of using Polypropylene (PP) as an antistripping additive of asphalt mixtures is investigated. Here, the moisture susceptibility of asphalt mixtures is evaluated by determining the micro-mechanisms using the surface free energy (SFE) concept. The adhesion bond between the aggregate and asphalt binder and the cohesion strength of the asphalt binder are considered as the main factors that affect moisture damage of asphalt mixtures. Test results indicate that the use of PP improves the resistance of asphalt mixtures in both wet and dry conditions. Also, the results of the SFE tests showed that the modifying asphalt binder with PP increases free energy of adhesion that will improve adhesion resistance between asphalt binder-aggregates. The amount of debonding energy in the samples which are modified with PP is lower than the control samples. This shows that by modifying asphalt binders, the tendency of asphalt binder-aggregate stripping can be reduced. The results show the total SFE of the asphalt binders of the modified samples have more free energy rather than the control samples. This phenomenon shows that failure in the asphalt binder film and cohesion failure will be happened more rarely

Providing Laboratory Rutting Models for Modified Asphalt Mixes with Different Waste Materials

Due to the complex behavior of asphalt pavement materials under various loading conditions, pavement structure, and environmental conditions, accurately predicting the permanent deformation of asphalt pavement is difficult. This study discusses the application of artificial neural network (ANN) and the multiple linear regression (MLR) in predicting permanent deformation of asphalt concrete mixtures modified by waste materials (waste plastic bottles and waste high-density polyethylene). The use of waste materials in the pavement industry can prevent the accumulation of waste material and environmental pollution and can reduce primary production costs. The results of a laboratory study evaluating the rutting properties of Hot-Mix Asphalt (HMA) mixtures using dynamic creep tests were investigated. The results indicate ANN techniques are more effective in predicting the rutting of the modified mixtures tested in this study than the traditional statistical-based prediction models. On the other hand, results show that an increase in percentage of waste materials is very effective in reducing the final strain of asphalt mixtures. However, an increase in percentage of additives over 7% does not help to reduce permanent deformation under dynamic loading in the asphalt mixtures

Characterization of permanent deformation resistance of precipitated calcium carbonate modified asphalt mixture

Rutting in asphalt pavements that appears as an indentation in the longitudinal direction continues to create problems for pavement agencies. This paper presents the results of the laboratory study on rutting susceptibility of asphalt mixtures containing Precipitated Calcium Carbonate (PCC) coated by a thin layer of a polymeric compound. To assess the impact of PCC on rutting properties of HMA, control mixtures (without PCC) and mixtures containing PCC were tested using dynamic creep and indirect tensile stiffness modulus tests. The HMA mixtures containing 0%, 5%, 10%, and 15% of PCC were prepared. In this paper, it is shown that the use of PCC can decrease the rutting potential of asphalt mixes. According to the results obtained in this study; using a 5% PCC in HMA is acceptable for heavy traffic volume roads especially in tropical regions

The effects of using recycled concrete on fatigue behavior of hot mix asphalt

Fatigue cracking is the main form of structural damage in flexible pavements. Under the action of repeated vehicular loading, deterioration of the asphalt concrete materials in pavements caused by the accumulation and growth of the micro and macro cracks gradually takes place. The results of a laboratory study evaluating the fatigue properties of hot-mix asphalt (HMA) mixtures using indirect tensile fatigue test (ITFT) were investigated in this paper. The HMA mixtures containing 0%, 35%, 70%, and 100% of recycling concrete aggregate (RCA) were plant prepared with one source of aggregate, limestone, and one type of binder, 60/70-penetration grade. In this paper, it is shown that the use of recycled concrete produced by crushing demolished concrete elements can increase the efficiency of asphalt mixes, reduce primary production costs and prevent much fullness of the recycled materials in the environment. It was found that replacing up to 100% of the virgin aggregate by RCA improved the fatigue properties of the asphalt mixtures