Dottorato in INGEGNERIA ELETTRICA, DEI MATERIALI E DELLE
NANOTECNOLOGIE

Titolo della tesi: Rub/Crete: Mechanical properties of scrap to reuse tire-derived as rubber and granule in concrete for the production of a brick suitable for architecture and construction applications.

In the last ten years, the Portland cement industry has received wide criticism due to its related high embodied energy and carbon dioxide footprint. Recently, numerous “clean” strategies and solutions were developed. This doctoral research project covers an overview of sustainable material recycling solutions important for the environment from different material aggregation, processes, and industries. Among these, a research work conducted on recycling rubber tire powder as a substituted material within the concrete aggregate mixture, as it is gaining growing interest as a functional way to design eco-friendlier construction materials and for waste management issues suffered by various industries. In addition to that, this recycling process offers several advantages related to the construction and architectural sectors; such as economic; environmental; social; and engineering benefits. Moreover, the recycling of waste tires is of paramount importance for environmental protection and economic reasons, as the number of scrapped tires in the United States has reached 550 million per year and is still rising. Even higher numbers are estimated in the European Union, reaching 1 billion tires per year. Disused tires create waste with a highly negative environmental impact. Tire disposal mainly involves highly polluting treatments (e.g. combustion processes to produce fuel oil), with only a small percentage of waste (3% to 15%) destined for less-invasive treatment such as powdering. This research project aims to show in detail through a study conducted at the Sapienza Engineering laboratory in collaboration with Fab Lab Sapienza and ETRA tire recycling organization, where it sheds the light on incorporating shredded/powdered rubber tires of different grain sizes substituted with sand in concrete for developing rubber concrete aggregate mixture for the production of Rub/Crete Brick, a brick useful for wall partition as well as for acoustic insulation. A lightweight brick useful for wall partitions in construction depends on the characteristics, mechanical properties, and the fundamental requirements of Rub/Crete material (fresh and hardened properties), and state-of-the-art aesthetic and architectural projects with functional properties. The conducted mechanical test work conducted on material samples has shown that a good compressive strength can be achieved through substituting 30% sand and 70% rubber granule with a water/cement ratio of 0.42, to be replaced totally from the amount of sand concerning the evolution of the mechanical tests shown in this research where it achieved 5.813 MPa as related to compressive strength compared to control 44.7 MPa, on the other hand, we can see signs that total replacement of rubber with sand using Rp50Rg50 sample achieved 2.883 MPa, from insulation properties where the sample 50% RP – 50% RG showed 9.65 Hrz to a lightweight density where the sample 50 RP 50% RG showed 1.2 kg/m3, The reason behind performing a final brick using and focusing on the Rp50Rg50 sample with total replacement of sand is to recycle the huge amount of rubber granules and powder tires in order to perform real and great environmental, sustainable and ecological recycling process. Correspondingly; first, as the percentage of aggregation between rubber powder and sand increases, compressive strength decreases. Second, aggregation replacement of rubber powder and sand shows a reduction in density. Third, the modulus of elasticity depends on the percentages added: the more rubber added to concrete, the less elastic the product will be. In addition, less tough concrete means higher strength. However, on the other side, as related to acoustic insulation performance, the test results shown the average value in comparison between white free measure, control, and Rub/Crete samples, where the maximum average value of White free sound upon all frequencies is 5.0625, the control sample shown the average value of 5.325 Hrz, however, the Rub/Crete samples as 30%RP- 70% RG have shown the highest effective value of sound insulation which have reached 9.8375 Hrz, whereas 50% S - 50% RP have shown 8.675, as well as 50% RP 50% RG, resulted in 9.65 Hrz, and 100 % RP performed 8.175 Hrz. Therefrom, this project shows a dual functionality: economic–environmental benefits and technological functionalization of the building material.