The excessive permanent deformation (rutting) in asphalt-concrete pavements resulting from frequent repetitions of heavy axle loads is studied in this paper. Rutting gradually develops with additional load applications and appears as longitudinal depressions in the wheel path. There are many causes of the rutting of asphalt roads, such as poor asphalt mixing and poor continuous aggregate gradation. All factors affecting the mixture resistance to permanent deformation must be discussed, and all must be properly considered to reduce the rutting propensity of asphalt-aggregate mixtures. In this study, several mixtures were produced with the most common techniques in rutting resistance (using the most effective additives for each mixture), and their performance was compared with the (conventional) mixture currently used in Iraq. The tests focused on the asphalt-concrete mixture for wearing courses. Different mixtures types were tried, namely, dense hot asphalt mixture (HMA) with two different asphalt contents (4.7% and 5.3%), Open-Grade Friction Course (OGFC) mixture, Stone Mastic Asphalt (SMA) mixture, and Beton Bitumineux a Module Eleve (BBME). The modifiers included natural Sisal Fibers (SFs), Carbon Fibers (CFs), and mineral filler (hydrated lime, HL). Marshall test was carried out to find stability and flow values. Rutting was evaluated by the repeated load test for cylindrical specimens under two temperatures (40°C and 60°C) to obtain the permanent deformation parameters. The parameters were used as input to the VESYS 5W software to evaluate the rut depth during different times of design life under 7×10^6 Equivalent Single Axle Loads (ESALs). The results of the selected mixtures were compared with the mixture designed in the laboratory dense gradation mix Job-Mix Formula (JMF)) within the limits of the Iraqi specification (SCRB,2003). Manipulation of the aggregate gradation that is customary in the implementation of the local mixture showed that the best performance regarding rutting resistance was exhibited by JMF, which decreased the rut depth at 40°C and 60°C by 21.63mm and 44.304mm respectively, in comparison with the conventional mixture. Changing the aggregate gradation of the local mixture gives better performance in rutting resistance without additives or changing the percentage of asphalt, at the same cost.
Reflection cracking in asphalt concrete (AC) overlays is a common form of pavement deterioration that occurs when underlying cracks and joints in the pavement structure propagate through an overlay due to thermal and traffic-induced movement, ultimately degrading the pavement’s lifespan and performance. This study aims to determine how alterations in overlay thickness and temperature conditions, the incorporation of chopped fibers, and the use of geotextiles influence the overlay’s capacity to postpone the occurrence of reflection cracking. To achieve the above objective, a total of 36 prism specimens were prepared and tested using an overlay testing machine (OTM). The variables considered in this study were the thickness of the
... Show MoreChina occupies an area of 906 million square km. and lies east Asia. Its population approximately 1,388 people, according to census 2010. China was a global great power for centuries , then shrank its jurisdiction and occupied by European countries and Japan in the 19th century. It regained its strength and independence under the leadership and rule of the Chinese Communist Party since 1949. In the 21st century , the Chinese positions has risen universally due to its achievements in the economic and trade affairs . Nowadays, China became a largest exporting state in the world and a second economic power after USA.
The study of an urban street scene of the life cycle is one of the important things in urban scene studies and there are four vocabularys that are the basis for the life cycle of an urban scene and these vocabulary are (the street, transformation, land uses and urban scene).
the first vocabulary addressed in the research is the street where street classes were studied and its classifications in terms of morphology and function and study of street standards in cities.
The second term, are transformations, where the concept of transformation and its patterns and
... Show MoreThe performance and durability of the asphalt pavement structure mainly depend on the strength of the bonding between the layers. Such a bond is achieved through the use of an adhesive material (tack coat) to bond the asphalt layers. The main objective of this study is to evaluate the effect of moisture in conjunction with repeated traffic loads on the strength of the bonding between asphalt layers using two types of tack coats with different application rates. Using the nominal maximum size of aggregate (NMAS), the layers were graded (25/19) and (19/9.5) mm. The slabs of multilayer asphalt concrete were prepared using a roller compactor using two types of tack coats to bond between layers, namely rapid curing cut back a
... Show Morehis study aimed to investigate the usability of Recycled Concrete Aggregate (RCA) in warm mix asphalt (WMA) as the implementation of sustainable construction technology. Five replacement rates (0%, 25%, 50%, 75%, and 100%) were tested for the coarse fraction of virgin aggregate (VA) with 3 types of RCA: untreated RCA, HL-treated RCA, and HCL-treated RCA. Scanning electron microscopy (SEM) analyses were performed to investigate the surface morphology for both treated and untreated RCA. The optimum asphalt cement content for every substitution rate was determined using Marshall mix design method. Thereafter, asphalt concrete specimens were prepared using the optimum asphalt cement content, followed by the evaluation of their performance prope
... Show MorePermanent deformation, fatigue and thermal cracking are the three typical distresses of flexible pavement. Using hydrated lime (HL) into the conventional limestone mineral additive has been widely practiced, including in Europe, to improve the mechanical properties of hot mix asphalt (HMA) concrete and as the result the durability of the constructed pavement. Large number of experimental studies have been reported to find the optimum addition of HL for the improvement on HMA concrete mechanical properties, moisture susceptibility and fatigue resistance. Pavement in service is under complex thermomechanical stress-strain conditions due to coupled atmospheric and surrounding environment temperature variation and the traffic loading. To predic
... Show MoreConsuming of by-product or waste materials in highway engineering is significant in the construction of new roads and/or in renovations of the existing ones. Pulverised Fuel ash (PFA), which is a by-product material of burning coal in power stations, is one of these materials that might be incorporated instead of mineral filler in hot asphalt mixtures.
Two types of surface course mixtures have been prepared one with conventional mineral filler i.e. ordinary Portland cement (OPC) while the second was with PFA. Several testings have been conducted to indicate the mechanical properties which were Marshall Stability and Indirect Tensile Strength tests. On the other hand, moisture damage and ageing have been evaluated
... Show MoreBackground: The World Health Organization was declared COVID-19 a pandemic on March 11, 2020. As a result, to keep the coronavirus under control, protective technique like face covering is required. Vaccination, on the other hand, is regarded as a preventative and effective measure. As nursing students play an important role in the future of nursing, their perception regarding wearing mask and taking vaccine can be crucial in preventive measures regarding COVID-19. Objective: The purpose of this study was to assess the perception of nursing students’ regarding wearing mask and coronavirus vaccines. Design: A descriptive correlational design was used to guide this study. Settings and Participants: A total of 255 undergraduate
... Show MoreAbstract
Language is one of God’s blessings to human beings through which he
distingushed them from other creatures, then how if this language was arabic.
God honored this language and in which he descended his Gracious Boole
that gave it glory and magnificance, and made it an immortal revelation to the
arab nation in their poetry, oration, history and human tendency to the life of
knowledge, mind leadershipe, innovation and progress.
This study aimed at evaluating the arabic language come program for
the new teachers. The sample was of (25) participants who were shown a
questionaire consisting of (60) items distributed on (9) fields. Then, the data
was processed statisically by using preauency rate, Kai s
Hydrated lime has been recognized as an effective additive used to improve asphalt concrete properties in pavement applications. However, further work is still needed to quantify the effect of hydrated lime on asphaltic concrete performance under varied weather, temperature, and environmental conditions and in the application of different pavement courses. A research project was conducted using hydrated lime to modify the asphalt concretes used for the applications of wearing (surface), leveling (binder), and base courses. A previous publication reported the experimental study on the resistance to Marshall stability and the volumetric properties, the resilient modulus, and permanent deformation at three different weather temperatures. This
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