Plastics are a vast group of synthetic or semi-synthetic materials that are often made of polymers. Because of their plasticity, plastics can be molded, extruded, and pressed into solid objects of different sizes. Its extensive use is due to its flexibility, as well as a number of other properties such as light weight, durability, and low manufacturing costs. The high use of plastics has resulted in an increase in solid waste, with domestic waste accounting for a significant portion of it. Since this waste is not biodegradable and takes up a lot of space, it is considered a serious environmental problem. To overcome these adverse effects, recycling plastic waste and using it in concrete can be an effective way to protect the environment. In this study, an attempt was made to experimentally evaluate the mechanical properties of concrete with recycled PET plastic wastes. The effect of this type of plastic waste was investigated by adding it in three different lengths: 22 mm, 45 mm, and a combination of both lengths 22 + 45 mm. For each length of fiber, it was added in three percentages to concrete 0.1, 0.3 and 0.5 % of cement weight. Several experiments were carried out on concrete mixtures such as slump test, compressive test, splitting tensile test, flexural test, and ultrasound pulse velocity test. The findings showed that PET waste in the form of fibers could be incorporated into concrete and achieve adequate compressive strength. When the ultrasound test results were compared to the results of previous tests, it was discovered that normal concrete containing plastic waste in the form of fibers performed exceptionally well.

In the building process, the recycling of aggregates arising from building and demolition debris is one of the best alternatives to maintain the environment and the areas needed to bury these debris. It also helps to preserve natural concrete sources from depletion efficiently. The use of recycled aggregates in new concrete manufacturing, however, leads to a decrease in concrete\\\’s strength characteristics. This reduction rises with the rise in the percentage of recycled aggregates used in concrete, which has caused many researchers to undertake many researches on how to enhance the characteristics of recycled aggregate-containing concrete. This paper presents several studies that examined the effect of adding steel fiber to improve the properties of concrete containing a coarse recycled aggregate.

The current research includes practical results of study and investigated the subject of strengthening the shear strength through uniaxial confinement (one direction) using GFRP Sheets. This study was carried out by casting eight specimens (the push-off specimens group) which was divided in to four groups, the first non confined, being the reference group, the remaining groups consisted of two specimens each with only one variable being the degree of strengthening that is the numbers of confinement layers. The second, third, and fourth group were confined with one, tow, and three layers respectively. All specimens were tested through the application of a vertical load up to failure. The result indicated that there is a clear indication of shear strength increase amounting to 33% relative to the reference specimens (non confined), also there was a noticeable increase in the absorption capacity as a function of the number of confinement layers.

In recent years, the use of nanotechnology materials has increased in strengthening and enhancing the behavior of concrete and its mechanical properties. This is due to the special characteristic of these materials such as its tiny size that considerably improves the microstructure of concrete, which in return gives concrete new properties and dramatically enhances its behavior. The present study seeks to review several previous studies that investigated the effect of adding nano-silica on the mechanical properties, durability, transport properties, and microstructure of lightweight concrete. Based on the results, it has been noted that the addition of nano-silica material has a vital role in improving the properties of lightweight concrete. Moreover, it was observed that there is an increase in the compressive strength, tensile strength, and flexural strength due to the addition of nano-silica material. It has also been concluded that there is an improvement in the durability and transport properties of lightweight concrete.

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