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Research field: Aggregates, Bitumen, Asphalt Mix and Concrete
Expert: Mr Gharashi
Phone: 82883965
Address:
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Interest of researchers in using nanomaterials in asphalt mixes is increasing rapidly. In this research, the effects of using various nanomaterials in asphalt mixes were investigated. In addition, the effects of two different types of fillers at their conventional size and their nano-size in asphalt mixes were tested. Four types of nanomaterials, namely nano-CaCO3, nano-hydrated lime, nano-bentonite and nano-silica, and two types of anti-stripping fillers, namely hydrated lime and CaCO3 were selected. Nano-hydrated lime was produced using a planetary ball mill apparatus. In producing nano-hydrated lime, optimum combinations of the main parameters that affect particle size reduction in milling process were determined applying trial and error
Microwave heating/healing is a kind of maintenance technique to repair micro-cracks in asphalt mixes. This method was conducted mostly on unaged materials, and the effects of moisture and freeze-thaw damages have not completely been studied. The fluidity of the asphalt binder, accomplished by heating, increases the ability of binder to fill micro-cracks and heal the asphalt mixes. Moisture and freeze-thaw damage increase the modulus of asphalt binder resulting decrease of fluidity of material. In contrast, moisture and freeze-thaw damages could reduce the ability of mixes to heal. In this research, mixes were prepared using neat and activated carbon modified asphalt binders. In order to assess the microwave heating properties, mixes were su
Cohesion properties of the binder matrix within asphalt mixes and adhesion characteristics of the asphalt binder and aggregate particles are the two major mechanisms resisting against cracking in asphalt mixes. This study is focused on estimating crack resistance of asphalt mixes at intermediate temperatures through evaluation of cohesion and adhesion properties of binder-aggregate systems using Surface Free Energy (SFE) method. Semi-Circular Bending test (SCB) was used to support the SFE analysis. SFE measurements were performed applying Sessile Drop test method. A Granite aggregate type and two asphalt binders (PG64-16, PG58-22) containing various amounts of SBS polymer were used to produce six groups of asphalt mixes. Cohesion and adhesi
Permanent deformation of asphalt mixes is caused as a result of several parameters, including; asphalt mix characteristics, climatic conditions, and traffic loading extent and configuration. For evaluating this distress mode, international institutions and standard codes of practices suggest different processes and testing methods. However, each of these investigates rutting resistance of asphalt mixes at specific conditions. The aim of this research was to investigate the effects of different loading configurations on Hot Mix Asphalt (HMA) in laboratory, applying Repeated Load Permanent Deformation (RLPD) testing method. With this purpose, various loading configuration and load durations and rest periods were applied. In order to simulat
Recycling of Construction and Demolition Waste (CDW) with the purpose of re-using these in construction projects has substantial benefits for the environment and for conservation of natural aggregates resources. Recycled Concrete Aggregates (RCA) that are derived from buildings, concrete structures or distressed PCC pavements can be used in various applications. This paper reports results of the experimental study on the application of demolished concrete aggregates in preparing Hot Mix Asphalt (HMA). RCA materials were used both in their original form; and, treated before that these were added to HMA mix. Two treatment methods were applied to coarse RCA materials. Treatments were consisted of; one, a two-stage treatment of RCAs, using acid
This research investigates the effects of asphalt mixture aging on induced heating-healing processes. Induced healing of asphalt mixes, performed through applying external electromagnetic radiation, is an innovative preventive maintenance technique for repairing cracks in asphalt mixture. The fluidity and crack filling capability of asphalt binders play a pivotal role in induced healing characteristics. In this paper, activated carbon was used to enhance electromagnetic sensitivity of mixes. In order to impose various levels of aging, asphalt concrete specimens were aged in the oven for 3, 5, 7, and 9?days at 85 ℃. The indirect tensile and semicircular bending tests were conducted to evaluate the healing capability of mixes under the cycl
Aging in asphalt pavements results in reduced serviceability and flexibility of pavements. Aging is not commonly considered as distress, but it substantially effects the rate of evolution of various distresses. One of the common distress observed in aged asphalt pavements is cracking. If cracks/micro-cracks are healed during their initial formation, the service life of the pavement will be increased. Otherwise, there will be the risk of crack propagation that results in more cracking and loss of pavement strength. It is well known that asphalt mixes have capability of self-healing their cracks/micro-cracks when they are exposed to high temperatures. Cracks/micro-cracks in asphalt mixes can be healed through an induced healing process. Induc
Warm-mix asphalt (WMA) technology and recycling of asphalt pavement, i.e.,?reclaimed asphalt pavement (RAP), have been becoming more popular in recent years due to their economic and environmental benefits. Similarly, bio-oil rejuvenators seem to be a viable solution when the usage of high percentages of RAP is desired. However, employing a high percentage of RAP in WMA using bio-oil rejuvenator remains very limited. This experimental study investigates the use of high percentages of RAP (i.e.,?up to 90%) in WMA using bio-oil rejuvenator. To this end, rheological tests including rotational viscosity (RV), multiple stress creep recovery (MSCR), and linear amplitude sweep (LAS) were carried out on different combinations of binders. Wheel trac
The present work was drawn aimed at addressing the role of RAP materials on fracture and mechanical properties of foam WMA mixes. Fracture testing in the geometry of SCB and Pull-Off adhesion tests were performed coupled with mechanical testing in order to address cracking failure, internal bonding characteristics, and moisture susceptibility of asphalt mixes. The results of SCB testing were assessed through Flexibility Index, fracture energy, and Cracking Resistance Index of foam WMA mixes. Results of Pull-Off testing showed that increased RAP materials resulted in reduced adhesion between foam bitumen and aggregate particles. This indicates the adverse impact of excessive RAP contents (i.e., at 70%) in mixes on flexibility of foam-WMA mix
Dynamic modulus of asphalt mixtures is one of the most important input parameters in design and rehabilitation of asphalt pavements. Dynamic modulus predictive models are alternative methods for laboratory determination of this parameter. These models were developed based on laboratory data. Due to sophisticated and laborious laboratory testing methods, there is a need to develop new models to determine dynamic moduli of in-service asphalt layers. In this study, nine different asphalt pavement sites were selected in two southern provinces of Iran. Falling weight deflectometer (FWD) testing was performed at each site and core samples were taken from the asphalt layers for volumetric analysis. Using the results, dynamic moduli of asphalt laye
Aging phenomenon affects pavement performance that results in reduced flexibility of the pavement. Aging can cause asphalt binder stiffness in asphalt mixes and increases the risk of cracking. Cracks can be healed by the induction heating method. The ability of asphalt binder in flowing and filling cracks plays a dominant role in the induced healing of asphalt mixes. With this regard, activated carbon (AC) is added to asphalt concrete in order to enhance the electromagnetic radiation absorption of mixes. In order to apply age conditioning, both the control and modified asphalt concrete samples were kept in oven for 5 days at 85℃. It was found that heating rate of activated carbon modified asphalt mixes is 55 percent greater than control m
Application of Warm Mix Asphalt (WMA) together with presence of Reclaimed Asphalt Pavement (RAP) is increased because of their environmental and economic benefits. However, lack of an accepted approach to obtain the optimum mix design of WMA reported as one of main challenges in this way. Presence of RAP particles in WMA would increase this challeng with respect to the interaction of virgin asphalt binder and RAP aged binder. So, the interaction between different testing variables (i.e. RAP content, Asphalt binder content and mixing temperature) was considered to present the mix design. The foam bitumen technology was applied in this work to fabricat the WMA mixes containing various RAP contents (30%, 50% and 70%). In addition, the optimiza
The two traditional methods to incorporate crumb rubber into asphalt mixes are the dry process and wet process. Although dry process has greater advantages including more crumb rubber usage, conservation of natural resources, and so on, there is less desire to apply dry process compared to wet process because of its poor performance. This study aims to evaluate the usage of high contents of crumb rubber powder (CRP) as filler in asphalt mixes and provide further development in the dry process method by considering the curing process effect, different CRP contents and micro-scale size of CRP filler. The conventional filler of mixes was replaced with 20, 40 and 60% CRP by weight of filler and the mechanical properties of modified mixes, inclu
Resilient behavior of Unbound Granular Material (UGM), as defined with stiffness modulus, is considered to be one of the major parameters in pavement analysis. This itself is affected by several other factors.In this research, the effects of compaction level, moisture content and stress state were investigated on UGM resilient behavior using a Light Weight Deflectometer (LWD). For each of these parameters, three levels were selected. Response Surface Method (RSM) was applied and based on the results 17 test designs were determined.The results showed good correlation between stiffness modulus and compaction level, moisture content, compaction-moisture interaction and stress state (drop weight of LWD in this research) at 90% significant level
Recycled Concrete Aggregate (RCA) is considered to be a potential substitute for natural aggregates in asphalt mixtures. Despite some contradictory results achieved by researchers, it is believed that RCA treatment can improve quality of recycled asphalt mixes considerably. In this research, a two-stage treatment was applied on coarse RCA materials in order to improve their properties. The treatment was consisted of first soaking RCAs in Hydrochloric Acid (HCl); second impregnating the treated RCAs into Calcium Metasilicate (CM). The pores of RCAs were filled with CM particles. Substituting virgin aggregates with different amounts of coarse RCA materials into HMA resulted in increased tensile properties of mixes as tested in