Evaluation of an Improved Rotavapor Aging Apparatus Using a Morton Flask for Simulation of Hot-Mixing on Modified Asphalts

A modified Rotavapor apparatus and method had been previously developed at the Universityof Florida for simulation of short-term aging of modified asphalts. Due to the great potentialof this aging procedure, further refining of this procedure had been undertaken. This paperpresents the evaluation of an improved Rotavapor aging apparatus using a Morton flask. Itwas observed that greater temperature uniformity was obtained in the oil bath when theMorton flask was used. The equivalent aging severity between the modified rotavapor agingprocess and the standard short-term aging methods (TFOT and RTFOT) was established

Evaluation of Combined Excavation Waste and Reclaimed Asphalt Pavement Aggregates for Use in Road Bases and Sub-bases

More than 15 million tons of aggregates are imported each year to Qatar from neighbouring countries. Large quantities of waste materials (around 20 million tons/year) from excavation waste, demolition rubble and reclaimed asphalt pavement (RAP) are being generated. The main objective of this paper is to present the results on the use of combined excavation waste (EW) and RAP aggregates in the construction of road bases and sub-bases. Physical and chemical properties were determined. Different combinations of both materials were subjected to compaction and California Bearing Ratio (CBR) testing in accordance with Qatar Construction Specifications. Results indicated that, for the materials tested, it is not feasible to use excavation waste, RAP aggregates or a combination of the two materials in road bases and sub-bases. The materials failed to meet some Qatari standards such as Los Angeles abrasion, liquid limit, plasticity index and CBR specified for road construction.Qatar National Research Fund , UREP 12-014-2-00

Recycling of Local Qatar’s Steel Slag and Gravel Deposits in Road Construction

Every year, the State of Qatar generates about 400,000 tons of steel slag and another 500,000 tons of gravel as a result of steel manufacturing and washing sand, respectively. The two materials (by-products) are not fully utilized to their best market values. At the same time, infrastructural renewal will take place in Qatar over the next ten years, and there will be a greater demand for aggregates and other construction materials as the country suffers from the availability of good aggregates. This paper presents results obtained on the use of steel slag, gravel and gabbro (control) in hot mix asphalt concrete (HMAC) paving mixtures and road bases and sub-bases. Tests were conducted in accordance with Qatar Construction Specifications (QCS-2010) and results were compared with QCS requirements for aggregates used in these applications. Based on the data obtained in this work, steel slag and gravel aggregates have a promising potential to be used in hot mix asphalt concrete paving mixtures on Qatar’s roads, whether in asphalt base and asphalt wearing courses or as unbound aggregates in the base and sub-base pavement structure

Development of Warm Mix Asphalt with the Aid of Microstructural Characterization

The polymer-modified asphalt (PMA) reveals different types of advantageous properties depending on the type of polymer. However, one of the unwanted changes in PMA is the required higher temperature for mixing and compaction. To reduce these temperatures, different percentages of warm mix additive (WMA) have been utilized. However, the addition of WMA can lead to different micro-nano structural changes in the PMA and can subsequently affect overall performance of the asphalt pavement. Therefore, understanding the microstructural behavior of the polymer and additive modified asphalt is crucial to achieve the desired performance. This study attempts to substantiate the effect of WMA in three different PMAs and subsequent changes in different properties. These changes can be scrutinized from different perspectives; however, correlating a basic microstructural property to the rheology of asphalt is an effective way to understand the mechanism and predict performance. In this regard, the need for microstructural evaluation in terms of nano-adhesive properties is recommended. It is expected that assessing the adhesive properties by simulating the field condition can address the phase integrity and crystal structure of PMA and subsequent desired performance of the asphalt pavement. Finally, the observed adhesive properties can be further evaluated to find the prospects of other mechanical properties. Therefore, the need for a standard microstructural evaluation method of the adhesive properties has also been addressed in this study

International Conference on Civil Infrastructure and Construction (CIC 2020)

This is the proceedings of the CIC 2020 Conference, which was held under the patronage of His Excellency Sheikh Khalid bin Khalifa bin Abdulaziz Al Thani in Doha, Qatar from 2 to 5 February 2020. The goal of the conference was to provide a platform to discuss next-generation infrastructure and its construction among key players such as researchers, industry professionals and leaders, local government agencies, clients, construction contractors and policymakers. The conference gathered industry and academia to disseminate their research and field experiences in multiple areas of civil engineering. It was also a unique opportunity for companies and organizations to show the most recent advances in the field of civil infrastructure and construction. The conference covered a wide range of timely topics that address the needs of the construction industry all over the world and particularly in Qatar. All papers were peer reviewed by experts in their field and edited for publication. The conference accepted a total number of 127 papers submitted by authors from five different continents under the following four themes: Theme 1: Construction Management and Process Theme 2: Materials and Transportation Engineering Theme 3: Geotechnical, Environmental, and Geo-environmental Engineering Theme 4: Sustainability, Renovation, and Monitoring of Civil InfrastructureThe list of the Sponsors are listed at page 1

Modelling of Asphalt's Adhesive Behaviour Using Classification and Regression Tree (CART) Analysis

The modification by polymers and nanomaterials can significantly improve different properties of asphalt. However, during the service life, the oxidation affects the constituents of modified asphalt and subsequently results in deviation from the desired properties. One of the important properties affected due to oxidation is the adhesive properties of modified asphalt. In this study, the adhesive properties of asphalt modified with the polymers (styrene-butadiene-styrene and styrene-butadiene) and carbon nanotubes were investigated. Asphalt samples were aged in the laboratory by simulating the field conditions, and then adhesive properties were evaluated by different tips of atomic force microscopy (AFM) following the existing functional group in asphalt. Finally, a predictive modelling and machine learning technique called the classification and regression tree (CART) was used to predict the adhesive properties of modified asphalt subjected to oxidation. The parameters that affect the behaviour of asphalt have been used to predict the results using the CART. The results obtained from CART analysis were also compared with those from the regression model. It was observed that the CART analysis shows more explanatory relationships between different variables. The model can predict accurately the adhesive properties of modified asphalts considering the real field oxidation and chemistry of asphalt at a nanoscale.publication of this article was funded by the Qatar National LibraryScopu

Evaluation and calibration of dynamic modulus prediction models of asphalt mixtures for hot climates : Qatar as a case study

DATA AVAILABILITY : No data was used for the research described in the article.Please read abstract in the article.Qatar University and Texas A&M University at Qatar (International Research Collaboration Co-Fund). Qatar National Library funded the open-access publication of this article.https://www.elsevier.com/locate/cscmhj2023Civil Engineerin

Evaluation of Short-Term Aging Protocol for Asphalt Mixtures

Asphalt mixtures are subjected to short-term aging during the production, placement, and compaction processes. Proper evaluation of asphalt pavement performance relies on the accurate characterization of asphalt mixtures during the design stage. In this study, three different loose asphalt mixtures often used in Qatar were evaluated to develop a laboratory short-term aging procedure. Sample mixtures 1 and 3 were collected from a construction site, while mixture 2 was obtained from an asphalt plant. Virgin aggregates and binders were also collected to reproduce the mixtures in the laboratory. Laboratory-produced mixtures were conditioned at 135 °C using various time durations. The mechanical properties of laboratory-produced mixtures were compared to those of mixtures produced on site. The results of the mechanical and binder testing demonstrated that the proper short-term aging protocol for asphalt mixtures often used in road construction in the State of Qatar would involve heating asphalt mixtures for 4 h at 135 °C before laboratory compaction

State-of-the-Art Review on Sustainable Design and Construction of Quieter Pavements—Part 2: Factors Affecting Tire-Pavement Noise and Prediction Models

Traffic noise is a combination of noises produced from a number of sources. Of all the traffic noise sources, tire-pavement noise, which is emitted as a result of the interaction of rolling, slipping, or dragging tires and the pavement surface, is the dominant contributor of overall noise, particularly when vehicles are moving at higher speeds. Therefore, a number of research studies have been conducted to identify and analyze the factors affecting the generation of tire-pavement interaction noise. This helps in identifying and selecting appropriate noise mitigation techniques. In this paper, an extensive literature survey on the factors affecting tire-pavement noise is presented, and different views on the impact of each individual factor are discussed. From the literature survey, it is also evident that there is a potential correlation between pavement’s material characteristics and tire-pavement noise. A comprehensive discussion about this correlation is presented in the paper. In addition, this paper discusses various mathematical models for predicting pavement noise, and their advantages and shortcomings

Effect of Pavement Surface Aging on Tire-Pavement Noise: A Case Study in the State of Qatar

The acoustical performance of asphalt pavements changes with time due to combined effects of environmental conditions and various distresses induced by repeated and heavy traffic. This study examined the changes in the acoustical performance of dense graded asphalt (DGA) pavements over time in the State of Qatar. Tire-pavement noise was measured using on board sound intensity (OBSI) method. The OBSI noise measurements were conducted on DGA pavements with different age and the results were analyzed to evaluate the effect of aging on tire-pavement noise. The results demonstrated that the tire-pavement noise increased with pavement age. The frequency analysis of three road segments showed that at early stage of pavement service life, the noise level is more affected at higher frequency due to the densification and increased air pumping mechanism. At later stage of pavement service life, the noise level is more affected at lower frequency due to the change in pavement surface conditions (e.g., cracking and raveling)