Journal of Engineering <p>The Journal publishes 12 volumes annually; each volume consists of 10 - 12 scientific papers in all engineering specialties.</p> College of Engineering | University of Baghdad en-US Journal of Engineering 1726-4073 Experimental Study of Natural Convection in a Closed Cavity (Static Type Domestic Fridge) <p><strong>T</strong>his work provides an analysis of the thermal flow and behavior of the (load-free) refrigerator compartment. The main goal was to compare the thermal behavior inside the refrigerator cavity to the freezer door (home refrigerator) effect and install a fan on the freezer door while neglecting the heat transmitted by thermal radiation. Moreover, the velocity distribution, temperature, and velocity path lines are theoretically studied. This was observed without affecting the shelves inside the cabinet and the egg and butter places on the refrigerator door as they were removed and the aluminum door replaced with a glass door. This study aims to expand our knowledge about the temperature and flow fields of this refrigerator model. Finally, the development of this work highlights the importance of numerical simulation in the search for improvements in the design of this refrigerator model, which may assist refrigerator manufacturers.</p> Maryem Kanaan Adnan Munther Abdullah Mussa Copyright (c) 2021 Journal of Engineering 2021-10-01 2021-10-01 27 10 1 19 10.31026/j.eng.2021.10.01 Some Geotechnical Properties of Plastic Soil Enhanced with Cement Dust <p><strong>P</strong>lastic soil exhibits unfavorited geotechnical properties (when saturation), which causes negative defects to engineering structures. Different attempts (included various materials) were conducted to proffer solutions to such defects by experimenting in practical ways. On one hand, these attempts aimed to improve the engineering characteristics of plastic soil, and on the other hand, to use problematic waste materials as a stabilizer, like cement kiln dust, and to reduce environmental hazards. This paper explored the shrinkage, plasticity, and strength behavior of plastic soil enhanced with cement dust. The cement dust contents were 0%, 5%, 10%, 15% and 20% by dry weight of soil. An experimental series of shrinkage and plasticity tests and unconfined compression tests were carried out to explore the effects of cement dust on the quantitative amount of shrinkage, plasticity characteristics, and shear strength experienced by plastic soil. The effects of curing on soil strength were also investigated. The finding of this paper showed that the critical behavior and plasticity of plastic soil could be reduced by mixing the soil with 15% or 20% of cement dust. The undrained shear strength, cu, of plastic soil-cement dust mixtures increased with the increasing dust content up to 20%. In fact, this strength was affected by the curing period. The best enhancement was attained when the content of cement dust was 20%, and the undrained shear strength was increased more than three times at this content.</p> Abeer F. Hussein Ahmed S. Ali Abbas J. Al-Taie Copyright (c) 2021 Journal of Engineering 2021-10-01 2021-10-01 27 10 20 33 10.31026/j.eng.2021.10.02 Critical Evaluation for Grading and Fineness Modulus of Concrete Sands used in Sulaymaniyah City-Iraq <p><strong>F</strong>ine aggregates used for concrete works in Sulaymaniyah city frequently fail to meet the standard requirements for gradation and fineness modulus in cement concrete. This paper aims to critically evaluate gradation, fineness modulus, and clay contents of various natural sands produced and used for concrete work in the region.&nbsp; Sixteen field sand samples were collected from various sites in Darbandikhan (5 samples), Qalat Dizah (5 samples), Koysinjaq (5 samples), and Piramagroon (1 sample) confirming to ASTM D75. The field samples were parted into test specimens based on ASTM C702. Then, sieve analysis was carried out on the oven-dry test specimens in compliance with ASTM C136. The test results of fine aggregates were compared with American, British, and Iraqi specification standards using ASTM C33, BS 882, and IQS No. 45. It was revealed that only three sands satisfy the ASTM gradation limits while others do not comply and are on the coarser side. Also, eight samples meet the requirements recommended by BS 882, whereas five samples meet limits by IQS No. 45. It was found that only three sands have the fineness modulus within the ranges recommended by ACI 211.1 and ACI 211.4, while the others have high values. Furthermore, it was found that all sands include an allowable amount of finer particles passing sieve size 0.075 mm. In order to improve particle size distributions, it is recommended to use the blending method to obtain a suitable fine aggregate from two or more failed sands.</p> Muhammad Arf Muhammad Bilal K. Mohammed Faris R. Ahmed Bayan S. Al Numan Copyright (c) 2021 Journal of Engineering 2021-10-01 2021-10-01 27 10 34 49 10.31026/j.eng.2021.10.03 Influence of Using Various Percentages of Slag on Mechanical Properties of Fly Ash-based Geopolymer Concrete <p><strong>I</strong>n order to implement the concept of sustainability in the field of construction, it is necessary to find an alternative to the materials that cause pollution by manufacturing, the most important of which is cement. Because factory wastes provide siliceous and aluminous materials and contain calcium such as fly ash and slag that are used in the production of high-strength geopolymer concrete with specifications similar to ordinary concrete, it was necessary for developing this type of concrete that is helping to reduce CO<sub>2</sub> (dioxide carbon) in the atmosphere. Therefore, the aim of this study was to study the influence of incorporating various percentages of slag as a replacement for fly ash and the effect of slag on mechanical properties. This paper showed the details of the experimental work that has been undertaken to search and make tests the strength of geopolymer mixtures made of fly ash and then replaced fly ash with slag in different percentages. The geopolymer mixes were prepared using a ground granulated blast-furnace slag (GGBFS) blend and low calcium fly ash class F activated by an alkaline solution. The mixture compositions of fly ash to slag were (0.75:0.25, 0.65:0.35, 0.55:0.45) by weight of cementitious materials respectively and compared with reference mix of conventional concrete with mix proportion 1:1.5:3 (cement: sand: coarse agg.), respectively. The copper fiber was used as recycled material from electricity devices wastes such as (machines, motors, wires, and electronic devices) to enhance the mechanical properties of geopolymer concrete. The heat curing system at 40 <sup>o</sup>C temperature was used. The results revealed that the mix proportion of 0.45 blast furnace slag and 0.55 fly ash produced the best strength results. It also showed that this mix ratio could provide a solution for the need for heat curing for fly ash-based geopolymer.</p> Sarah Sameer Hussein Nada Mahdi Fawzi Copyright (c) 2021 Journal of Engineering 2021-10-01 2021-10-01 27 10 50 67 10.31026/j.eng.2021.10.04 The Use of SBS-Modified Binder to Eliminate the Aggregate Gradation Deviation Effects in Asphalt Mixtures <p>&nbsp;</p> <p><strong>A</strong>sphalt Hot Mix (HMA) is mainly applied in highway construction in Iraq because of its economic advantage and easy maintenance. Various factors impact the performance of HMA in the field. It is one of the significant impacts on aggregate gradation. The Universal Specification for Roads and Bridges in Iraq (SCRB) limits the different types of asphalt layers and allows for designed tolerance aggregate gradation. It is quite hard for contractors in the present asphalt industries to achieve the required job mix because of sieves' control problems. This study focuses on the effects on the required specification performance of aggregate deviations by using original and modified asphalt binder with AC(40-50) and 4% SBS, respectively. A mid gradation of the base asphalt mixture was selected as a reference mix, and more than 24 deviated mixtures were then prepared. Typical Marshall routine studies on prepared compounds were performed to assess the properties of the mixture. Bailey's theory (CA, Fac ratios) was also employed for understanding the impact of these deviations on the arrangement of particles and blending performance. Results show that the mixture performance is not affected greatly by minor aggregate deviations. However, a significant deviation in coarse aggregates leads to a decrease in Marshall properties. Results showed that a good tool for understanding mixing performance is the Bailey performance assessment method. This paper aims to study the effects of using &nbsp;4% Styrene Butadiene Styrene (SBS) and eliminating the effect of aggregate gradation deviations on the mixture performance.</p> Dhuha F. Abbas Hasan Al Mosawe Copyright (c) 2021 Journal of Engineering 2021-10-01 2021-10-01 27 10 68 85 10.31026/j.eng.2021.10.05 Analytical and Experimental Study of the Piles Cap Normal and Light Weight Aerated Concrete: Literature Review <p><strong>T</strong>he main objective of this study is to understand the work of the pile caps made of lightweight aerated foam concrete and study the many factors affecting the ability and the capacity of the shear. The study was done by analyzing previous practical and theoretical experiences on the reinforced concrete pile caps. The previous practical results indicated that all specimens failed by shear diagonal compression or tension modes except one specimen that failed flexural-shear mode. Based on test specimens' practical results and behavior, some theoretical methods for estimating the ultimate strength of reinforced concrete pile caps have been recommended, some of which evolved into the design documents available on the subject. A theoretical and practical study of compression concluded that the shear capacity is limited by the nodal zone bearing stresses. The flexural capacity can be described by the column load that would cause the yielding of the tie (i.e., steel reinforcement). Therefore, the design of pile caps should include a check on bearing strength to be added to the traditional section force approach for pile cap design.</p> Noor Ali Hussien Mohammed Mosleh Salman Husain Khalaf Jarallah Copyright (c) 2021 Journal of Engineering 2021-10-01 2021-10-01 27 10 86 105 10.31026/j.eng.2021.10.06