Journal of Civil Engineering Beyond Limits (CEBEL)

Saad Issa Sarsam Nazar Sajad Khadim

Asphalt concrete practices heavy loading and environmental impacts through the service life of the pavement. Micro cracks usually initiate and accumulate to form various types of distresses. However, asphalt concrete has the ability of self-healing under rest period and environment conditioning. Asphalt concrete is a composite material consisting of aggregates, bitumen, and air voids. Its mechanical behavior is complex due to its dependency of temperature, loading frequency, and strain level. In this investigation, asphalt concrete specimens of wearing course have been prepared in the laboratory and subjected to repeated indirect tensile stresses to initiate the micro-cracks. The test was stopped after 1200 load repetitions, and the specimens were stored in an oven at 60°C for 120 minutes to allow the crack healing process by external heating to start. Specimens were returned to the testing chamber and were subjected to another round of load repetitions. Specimens were tested before and after load repetitions and crack healing with the aid of ultrasonic pulse velocity traversing the specimen using pundit instrument. The healing indicator was the change in pulse velocity before and after the repeated load test and before and after healing process. It was concluded that the velocity decreases as the loading cycles proceeds indicating the start of damage, while the ultrasonic pulse velocity increases after the micro-crack healing process.

https://doi.org/10.36937/cebel.2021.001.001

Ali Al-Ghalib Dhia Ghailan

The aim of this research is to investigate the sustainability of design for deconstruction on saving: natural raw materials, embodied energy and carbon emission of steel buildings. A methodology is devised to account for designed for future reuse at the early design phase. The procedure is based on PAS2050 method. A steel structure building of two bays of size (6m x 8m) and of 4m height is devoted as a case study to assess the methodology. In this case study, three different floor systems are suggested: composite steel deck, hollow core precast concrete planks, and demountable precast composite floor system. The percentage reduced in embodied carbon energy is estimated through considering the steel building. The calculation of embodied carbon of the three models is relied on records of the Inventory of Carbon and Energy (ICE). The results show that CO2 emissions from the building can be dropped in so far as 50%, when design for deconstruction strategy is considered. Design standards and codes lack a little procedure to follow. Therefore, this study also outlines some helpful specifications, guidelines, and detailing of design for deconstruction of steel buildings.

https://doi.org/10.36937/cebel.2021.001.002

Afroja Sultana Md. Roknuzzaman Aysha Afrose Tapti Dev

Concrete structures are integral parts of modern civilization. Every year a huge amount of concrete waste is generated due to demolition of old concrete structures for replacing them with new high rise buildings or other structures, which consequently, increasing the environmental loads. Recycling of demolished concrete is found to be an effective way for sustainable development which can also minimize the disposal problem associated with concrete waste. Recycling of demolished concrete to produce usable aggregate, therefore, has drawn attention of researchers in the field of concrete technology. However, most of the studies in this field are focused on 1st generation recycled aggregate. Effect of multiple recycling on the properties of aggregate is merely studied. In this study, the effect of multiple times recycling on aggregate strength is observed. Strength of aggregate is evaluated in laboratory by Aggregate Crushing Value (ACV) test and Aggregate Impact Value (AIV) test after each generation of recycling. The ACV and AIV values of 1st generation, 2nd generation and 3rd generation recycled aggregates are compared with the natural source aggregate. Strength degradation after each stage of recycling is recorded. In addition, the test results of 1st generation, 2nd generation and 3rd generation recycled aggregates are interpreted, investigated and compared with standard requirement to outline their corresponding applications. ACV value for natural aggregate is found to increase by 2.5% after 1st stage of recycling and it increased by 4.64% and 6.79% after 2nd and 3rd stage of recycling respectively. On the other hand, AIV value for natural aggregate is found to increase by 7.04% after 1st stage of recycling and it increased by 10.35% and 12.47% after 2nd and 3rd stage of recycling respectively. The study reveals that the strength of 1st generation recycled aggregates are quite similar to that of natural aggregate and can be used for concreting in general purposes. 2nd generation recycled aggregate cannot be used in the production of concrete in heavy duty floor but can successfully be used in concrete for wearing surface and 3rd generation recycled aggregates are too weak for road surfacing.

https://doi.org/10.36937/cebel.2021.001.003

Ahmet ATALAY Ömer Faruk BİRCİK

The increasing number of urban centers and the increasing number of vehicles caused by industrialization caused problems such as lack of infrastructure in traffic, environmental pollution and an increase in energy requirements. This situation led the city administrators to search for solutions in order to improve the efficiency of public transportation systems and increase their efficiency. In this study, it is aimed to determine the functional efficiency of the bus lines used in urban public transportation. For this purpose, the lines are classified according to their functional activities by using the functional data of the lines. Both classical cluster analysis and self-organizing mapping (SOM) method were used for classification. Data from Erzurum main public transport lines were used to implement the methods. According to the findings of this study, it was determined that the two methods achieved similar results. As a result, it has been determined that classification of public transportation lines used in cities according to their functional efficiency will be beneficial for decision makers to make correct planning. With the right planning in public transport lines, significant economic and environmental benefits will be obtained.

https://doi.org/10.36937/cebel.2021.001.004

Nitish Bastola Mena Souliman Zabi Mohammed

Finite element modeling (FEM) has been an integral tool for civil engineering researchers. The simplification of day to day engineering problems with known scientific validation makes this tool more appropriate. In the field of pavement engineering, the use of FEM has been a relatively new tool. Various conditions of pavement materials, which are complex in nature, makes the modeling more challenging. This study aims to develop a basic beam model as per AASHTO T321 for evaluating the performance of asphalt material under fatigue loading. The necessary conditions and parameters are best optimized to match the research on National Cooperative Highway Research Program Project 9-44A (NCHRP Report 762). Various mechanical and fatigue-related properties of asphalt materials were studied to develop a simplified finite element approach through ANSYS. It is observed that stiffness induced behavior and fatigue performance can be predicted in advance and in a timely fashion with the utilization of FEM when compared to performing actual laboratory testing. In this study, different life and damage analyses were performed for different sets of the beam. It was found that stiffness plays a significant role in enhancing the minimum critical life of asphalt materials. A higher stiffness of the asphalt beam characterized a higher minimum critical life, and lower stiffness characterized the lower minimum critical life.

https://doi.org/10.36937/cebel.2021.001.005