Azad Abdulkadir Mohammed

This study explores the potential of natural and organic materials as eco-friendly alternatives to admixtures in concrete production. Concrete, being the second most utilized material globally, often relies on chemical admixtures to enhance its properties, which can pose health and environmental risks. In contrast, natural admixtures derived from fruits, herbs, and animal products offer a sustainable solution, reducing environmental impact and costs. The research highlights various natural additives, including palm liquor, mulberry extract, and okra extract, which enhance the mechanical properties of concrete. The findings emphasize the importance of utilizing naturally occurring materials in concrete construction, advocating for a shift toward organic admixtures that are not only effective but also environmentally friendly. The study concludes that the concrete industry should embrace natural admixtures to enhance performance while addressing ecological concerns. Natural additives like palm liquor, mulberry extract, grape extract, black pulp, cactus, hen egg, cypress tree, water hyacinth, sugarcane juice, and hen egg can enhance the mechanical properties and durability of mortar and concrete. These natural admixtures are more environmentally friendly and less expensive than chemical admixtures, making them suitable for the concrete industry. However, the behavior of natural additives is strongly influenced by the plant or resource source, and advanced technology is not needed to manufacture them.

This study investigates the impact of specimen size on the flexural strength of concrete reinforced with optimized polyethylene terephthalate (PET) fibers. A series of experimental tests were conducted using various PET fiber ratios (0.5 to 1.5% by the total volume of the mix) and lengths (15, 30, and 45 mm) to highlight the optimized PET fiber in concrete. Flexural strength tests were carried out on prismatic specimens of varying sizes (100x100x400 mm, 100x150x500 mm, and 100x200x700 mm) and different concrete grades (20, 35, and 45 MPa). The findings indicate a significant improvement in the splitting tensile strength of the concrete, reaching up to 18.43% with the addition of PET fibers. These fibers effectively act as bridges across cracks, reducing their width and halting their propagation. The optimal PET fiber length was identified as 30 mm, added to the concrete at a rate of 1% by the total volume of the mix. Moreover, the results revealed a noticeable effect of the specimen size on the flexural strength of PET fiber-reinforced concrete, with an inverse relationship between specimen size and measured flexural strength. As the size of the specimen increased, the flexural strength decreased. Based on the experimental data, an empirical relationship was developed to quantify the flexural strength of optimized PET fiber-reinforced concrete considering the size effect. These relationships provide practical tools for engineers to accurately account for the size effect in the design and analysis of fiber-reinforced concrete structures

Anchor bolts are widely utilized in numerous industries, including mechanical, building construction, and mining sectors. Anchor bolt uses range from the installation of permanent objects including hybrid constructions, illumination poles, and directional signs to the installation of temporary structures, such as the construction of formwork and safety netting. Several varieties of destructive testing instruments exist in the construction industry for determining the load-bearing capacity of concrete anchors. However, there has been a lack of attention to the development of non-destructive testing (NDT) techniques for the estimation of pull-out loads. This study highlights the limited research on evaluating the pull-out strength of embedded steel bolts in concrete using non-destructive tests and illustrates their relationship with each other. This critical review has demonstrated that embedded concrete anchor pull-out strength depends on alignment, embedment length, anchor bolt diameter, micro flaws, and bolt geometry. The embedment length of anchor bolts contributes much more to the improvement in pull-out strength than the bolt diameter. The ultrasonic pulse velocity (UPV) assessment and the Schmidt hammer (SH) assessment can be successfully used to monitor the quality of embedded anchor bolts in normal-strength concrete structures by identifying defective anchor bolts with porous bonds. Anchor bolts with insufficient bonding were found to have a lower rebound value and a prolonged ultrasonic pulse time of transit.

In this study, a model was proposed based on calculating the total surface area of aggregate to assess fresh density, compressive, and splitting tensile strengths of plastic aggregate (PA) recycled concrete. The key factor is the change in the total surface area of the natural aggregate by the PA. For a given PA volume, the change in the property could be assessed. The prediction well depends on the natural and plastic aggregates distribution size, specific gravity, and bulk density. The proposed model prediction was accurate when applied to high-strength, and lightweight concretes. The reason is attributed to the relatively good bond between PA and hardened cement paste in these concretes. However, for the majority of concrete mixes investigated, the model moderately underestimated strength loss, and this underestimation could be attributed to the PA- hardened cement paste bond deficiency. An attempt was made to assess the bond deficiency parameter for a more accurate prediction.