Search

The crushing process has a major influence on generating the shape properties of mineral aggregates (form, angularity, and texture). It is vital to ensure that the crushing process produces aggregates with no significant variations in shape properties so that the quality and performance of building or pavement materials are not negatively altered. The main objective of this study is to investigate the variations in crushers’ daily production using an imaging technique. Samples from three different crusher sites were collected for 3 consecutive days. Aggregate Image Measurement System (AIMS) was used to analyze one size of coarse aggregate and one size of fine aggregate. The investigation was carried out by comparing the measured shape properties that AIMS quantify which include (sphericity, angularity, texture, and 2-D form). AIMS captured changes in coarse aggregate texture and sphericity, whereas no significant changes in angularity and 2-D form were detected. Variations in shape properties seem to be more apparent in the coarser sizes suggesting that testing of larger sizes might be more appropriate for investigating variations in crushers productions based on aggregate shape. Observed variations in texture and form between samples on a given day while angularity remained unchanged, is evidence that shape properties are independent of each other. These findings might prove the need to use imaging techniques to select the most efficient crushing practices to meet the desired aggregate shape. The authors recommend conducting similar studies using more aggregate sources and sizes, different crusher types, and longer study periods.

The objective of this study is to investigate the effect of using Pozzolan as an asphalt binder modifier and assess its potential physical and rheological improvements. This research also intends to initiate a comprehensive research on the effect of Pozzolan on the rheological characteristics of asphalt binder since only limited studies have used Pozzolan as an asphalt binder modifier. Pozzolan was added to a (60/70) penetration grade asphalt binder at six different percentages in addition to the control asphalt binder. Both traditional and rheological tests on modified and control asphalt binders were performed. The traditional tests included penetration, softening point, flash and fire points, and ductility. The rheological tests, on the other hand, included rotational viscometer (RV) and Dynamic Shear Rheometer (DSR) tests. The outcomes proved that adding Pozzolan to asphalt binder enhanced high-temperature performance. 15% Pozzolan content was found to be the optimum content at which most rheological characteristics of the asphalt binder were enhanced. The experimental outcomes were contrasted and analyzed statistically by the analysis of variance (ANOVA) to discover any significant difference between the influence of Pozzolan and test temperature. The outcomes of one-way ANOVA pointed out that Pozzolan had a significant influence on the rotational viscosity and physical characteristics. Also, the change in Pozzolan content and temperature together showed a significant effect on the rutting parameter according to the two-way ANOVA outcomes.

Distracting activities while driving are common and can result in errors that threaten road users’ safety. The main objectives of this study were to investigate drivers’ perspectives of the factors contributing to distraction, determine the relative rank of types of distractions, recognize the road factors and environmental effects that make distractions more dangerous, and identify the most effective measures to reduce driver distractions. A survey was conducted to assess Jordanian drivers’ experiences with distracted driving, and what solutions they believed could be implemented to solve the problems. The study’s outcomes revealed that drivers perceive visual distractions as the most dangerous, followed by cognitive, manual, and auditory distractions, respectively. It was also found that “mobile phone texting or dialing” was ranked the top most dangerous visual and manual distracting factor. “Baby is crying or kids are fighting in the back seat” was perceived by all demographic groups as the riskiest auditory factor. Regarding cognitive distraction, four factors were perceived as the most serious, of which “Baby is crying”, “Driving while angry or sad or agitated”, “Talking on a cell phone—even a hands-free one” and “Conversing with passengers” were determined to be the top four distracting factors. The results also revealed that drivers believe that “laws and enforcement” is the most effective measure to reduce distractions while driving.

Road traffic signs are part of the road infrastructure components meant to ensure the safe use of roads by motorists and pedestrians alike. A good knowledge and comprehension of road signs helps ensure smooth flow of traffic, improves safety for other motorists and provides drivers with good reaction time to comply with the message dictated by the signs. Abu Dhabi, being the capital of the UAE, brings together people from all over the world for work, business or tourism. Abu Dhabi has quality roads and traffic signage together with an efficient police force that enforces adherence to traffic rules. Despite all these and the reduced fatalities in absolute terms, traffic violations have been increasing exponentially, resulting in five million traffic fines in 2019 for a population of about 2.9 million inhabitants. This study sought to assess motorists’ comprehension of the various traffic signs used across the UAE. The results of the survey (N = 200) revealed that the drivers were able to correctly identify 77% of the road signs in the survey. It was also found that the respondents failed to correctly identify traffic signs within the specific category referred to as “advance warning signs”. Respondents’ education, nationality, gender, and marital status did not have any statistically significant effects on the results compared to earlier studies. It is recommended that more attention be focused on driver education and training.

The objective of this study was to identify the most salient driver faults that cause crashes on some Jordanian rural and suburban roadway segments, to examine crashes with distracted driving as the driver’s fault, and to investigate the differences between crashes caused by distracted driving. Data for more than 10,200 crashes on nine roadway segments (five rural and four suburban) were accessed from the relevant government agency, but only n = 2472 were used for analysis after controlling for crashes specified as being caused by drivers’ distracted driving. IBM SPSS version 22 was used to perform descriptive analysis and independent samples’ t-tests. The results revealed that distracted driving was the second most common driver fault to cause crashes and the second main cause of fatalities and injuries on both rural and suburban roadways. Distracted driving on rural highways appears to be more fatal, whereas it caused more crashes with severe injuries on suburban roads. The variables at junction, road grade, number of lanes, weather condition, crash type, and number of vehicles involved were found to be statistically significant but with a small effect size. The following categories showed high percentages of distracted driving crashes on rural and suburban roadways: males, drivers 25–39 years old, non-holidays, weekdays, tangent sections, two-way divided roads, not at junction, level roads, two-lane roads, clear weather, dry surface, daylight, and automobile vehicles showed high percentages of distracted driving crashes on rural and suburban roadways. Differences between crashes on rural and suburban roadways caused by distracted driving were found to be small.

This research investigates the effect of adding three different modifiers to laboratory-prepared Superpave asphalt concrete mixtures to evaluate their ability to strengthen and reinforce asphalt co...

[EN] Pedestrian safety is a major concern throughout the world because pedestrians are considered to be the most vulnerable roadway users. This paper sought to identify the main factors in pedestrian-vehicle crashes that increase the risk of a fatality or severe injury. Pedestrian-vehicle crashes which occurred in urban and suburban areas in Jordan between 2009 and 2011 were investigated. Extracted rules from Bayesian networks were used to identify factors related to severity of pedestrian-vehicle crashes. To obtain as much information as possible about these factors, three subsets were used. The first and second subsets contain all types of collisions (pedestrian and nonpedestrian), in which the first subset used collision type as a class variable and the second subset used injury severity. The third subset contains pedestrian collisions only and used injury severity as the class variable. The results indicate that when using collision type as the class variable, better performance was obtained and that the following variables increase the risk of fatality or severe injury: roadway type, number of lanes, speed limit, lighting, and adverse weather conditions.

This paper reports an experimental investigation into the inherent anisotropy and particle breakage of natural Aqaba sand. The natural sand specimens were subjected to one dimensional compression to induce breakage. The grain size distributions of the specimens were obtained before and after the application of the stresses. Thereafter, the sand shear strength parameters were assessed using direct shear box tests. The results indicate that peak shear strength parameters show little decrease with increasing particle breakage. However, the dilatancy component of the shear strength diminishes with increasing particle breakage and a considerable amount of dilation occurs on samples with a higher bedding plane, regardless of the extent of particle breakage.

Form, texture, and angularity are among the properties of aggregates that have a significant effect on the performance of hot-mix asphalt, hydraulic cement concrete, and unbound base and subbase layers. Imaging techniques have provided a good means to quantify aggregate shape properties rapidly in spite of the fact that they might differ in the mathematical procedure and the instrumental setup they utilize. The validity of the mathematical procedure is essential for the results to be useful in quantifying aggregate shape. Some of the most widely used aggregate shape analysis techniques were evaluated in this paper. The analysis results revealed that some of the available analysis methods are influenced by both angularity and form changes and, consequently, are not suitable to distinguish between these two characteristics. Also, some of the analysis methods are quite adequate to measure both texture and angularity when changes are made to the image resolution and magnification level. The following analysis methods are recommended: wavelet analysis of gray images for texture; both the gradient method and tracing the change in slope of a particle outline method for angularity; aspect ratio for 2-dimensional form; and sphericity or the proportions of the three particle dimensions for 3-dimensional form.

This paper presents the development of a methodology for the classification of aggregates based on their shape, angularity, and texture characteristics. This methodology utilizes the Aggregate Imaging System (AIMS) to measure aggregate characteristics, and the clustering statistical method to analyze the measurements. The outcome of this analysis method is the percentage of aggregate particles that belong to groups or clusters that have statistically different characteristics. The “Categorical Counts” method is employed in this study for comparing the characteristics of different aggregate samples. This method detects not only the statistical difference between aggregate samples, but it is also capable of identifying differences in each of the clusters. The quality of AIMS measurements is evaluated through the analysis of repeatability and reproducibility. Finally, statistical analysis was conducted to determine whether aggregate properties are significant enough to influence the measured mechani...

Aggregate shape characteristics play a major role in determining the structural and functional properties of asphalt mixes. A comprehensive, statistically based methodology for the analysis and classification of the shape characteristics of both fine and coarse aggregates is presented. These characteristics are form (three dimensions of coarse aggregates), angularity, and surface texture. The methodology was developed by measuring the distribution of the shape characteristics of aggregates from a wide range of sources and varying sizes. The limits for the classification groups were determined with the use of a cluster analysis. The new methodology offers several advantages over current methods used in practice. It is based on the distribution of shape characteristics in an aggregate sample rather than on average indices of these characteristics. The coarse aggregate form is determined with the use of a three-dimensional analysis of particles, which allows particles to be distinguished between flat, elongated, or flat and elongated particles. The fundamental gradient and wavelet methods were used to quantify angularity and surface texture, respectively. The classification methodology can be used to evaluate the effects of different processes, such as crushing techniques and blending, on aggregate shape distribution. It also lends itself to the development of aggregate specifications on the basis of the distribution of shape characteristics.