Modern society demands more sustainable and economical construction elements. One of the available options for manufacturing this type of element is the valorisation of end-of-life waste, such as, for example, the recycling of polymers used in industry. The valorisation of these wastes reduces costs and avoids the pollution generated by their landfill disposal. With the aim of helping to obtain this type of material, this work describes a methodology for recycling polyethylene for the manufacture of fibres that will later be used as reinforcement for structural concrete. These fibres are manufactured using an injection moulding machine. Subsequently, their physical and mechanical properties are measured and compared with those of the material before it is crushed and injected. The aim of this comparison is to evaluate the recycling process and analyse the reduction of the physical-mechanical properties of the recycled polyethylene in the process. Finally, to determine the properties of the fibre concrete, three types of concrete were produced: a control concrete, a reinforced concrete with 2 kg/m3 of fibres, and a reinforced concrete with 4 kg/m3 of fibres. The results show an enhancement of mechanical properties when the fibres are incorporated, particularly the tensile strength; and they also show excellent performance controlling cracking in concrete.

Cement-treated bases are soils, gravels or manufactured aggregates mixed with certain quantities of cement and water in order to improve the characteristics of a base or sub-base layer. Due to the exploitation of natural aggregates, it is a matter of importance to avoid shortage of natural resources, which is why the use of recycled aggregates is a practical solution. In this paper we studied the feasibility of the use of untreated electric arc furnace slags and foundry sand in the development of cement-treated bases and slag aggregate concrete with a lower quantity of cement. We analyzed the physical, mechanical and durability characteristics of the aggregates, followed by the design of mixes to fabricate test specimens. With cement-treated bases, results showed an optimal moisture content of 5% and a dry density of 2.47 g/cm3. Cement-treated bases made with untreated slag aggregate, foundry sand and 4% of cement content showed an unconfined compression strength at seven days of 3.73 MPa. For siderurgical aggregate concrete mixes, compressive strength, modulus of elasticity and flexural strength tests were made. The results showed that the mixes had good mechanical properties but durability properties could be an issue.

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This research aimed at ascertaining the performance of raw dura species of Palm Kernel Shells (PKS) in comparison to a different species of PKS (tenera) as a replacement for known aggregates for pervious lightweight concrete. Using limestones as the known aggregates, control pervious concrete was batched, and relevant tests were conducted. Major tests conducted on the composites concerned compressive, tensile, and flexural strength, as well as permeability, densities, and absorption. Logistic constraints on transporting the dura-PKS limited the quantity needed to ascertain the variety of replacements of the dura-PKS. With a 25% replacement known to be the most suitable ratio for related investigations, we adopted that ratio and compared to the extreme ratio of 100% dura-PKS. The tests revealed that a 100% replacement of known aggregates by the dura-PKS resulted in high porosity and permeability, although the resistances to compression, tension, and flexural loads read low for the same mixture. Instead, pervious concrete 25% of dura-PKS replacement yielded optimum water permeability rate and flexural and compressive stresses. However, the flakiness index recorded for the dura-PKS was almost half that of the tenera species and was not reflected in the mechanical properties as the results gave relatively lower strengths. The results in the case of the dura species do not differ significantly compared to the tenera-PKS in terms of strength and permeability.

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