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The valorization of local by-products in the manufacture of a new range of sand concrete and the improvement of their properties, will lead to seek an arrangement between performance and cost in order to achieve a resistant material. Waste recycling affects two very important affect namely the environmental impact and the economic impact. The main objective of our work is to contribute to optimize the formulation of sand concrete as part of the recovery of waste, which is harmful to the environment given its bulky and unattractive nature, it is waste plastic. Most PET bottles become waste after use, causing environmental problems. To solve this problem, a method for recycling PET bottles as fibers to strengthen concrete is proposed. Two types of plastic waste are added to sand concrete; the first concerns the recycling of post-consumer bottles in PET, in the form of polyester fiber supplied by the company RET-PLAST and the second type concerns the packaging belts made of polyethylene terephthalate (PET). The properties in the fresh state (workability and density) and in the hardened state (compressive strength, tensile strength and water absorption) of the various produced concretes are analyzed and compared against their respective controls. From the experimental results, it can be concluded that the reinforcement of the cement matrix with PET fibers with a rate of 1% improves the mechanical properties of sand concrete as well as a remarkable decrease in its water absorption capacity.

The reuse of concrete waste as a secondary aggregate could be an efficient solution for sustainable development and long-term environmental protection. However, the variable quality of waste concrete, especially with various compressive strengths, can have a negative effect on the final compressive strength of recycled concrete. In this approach, the major goal of this research is to study the effect of parent concrete qualities on the performance of recycled concrete. To accomplish this task, three grades of different compressive strengths (10 to 15) MPa, (20 to 25) MPa, and (30 to 40) MPa have been analyzed in an experimental test program, in which an unknown compressive strength is introduced as well. The experimental mix use 40% of secondary aggregates (both course and fine) and 60% of natural aggregates. This led to the decreasing of the compressive strength of the test concrete between 14% and 23.7% compared to the normal concrete. This loss was improved by adding an amount of cement equivalent to 4% of the weight of the recycled aggregate used. The achieved results prove that the strength properties of the parent concrete have a limited effect on the compressive strength of the recycled concrete. Additionally, low compressive strength parent concrete, when crushed, generates a high amount of fine aggregate and large percentage of recycled coarse aggregates with less attached mortar, and presents the same compressive strength as an excellent parent concrete.

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