Post-War Construction Demolition Wastes Recycling and Reusing in Sustainable Practices

Abstract

One of the major consequences of the recent war on Lebanon in 2023-2024 is the vast destruction of infrastructure and habitations in various towns and villages, mainly in South Lebanon, the Beqaa region, and the Southern Suburb of Beirut. The full or partial demolitions that ensued resulted in massive amounts of construction rubbles and debris of all kinds which, for the most part, are still lying on site. Solutions are now urgently awaited, and some are being proposed to manage the waste debris, ranging from large-scale to local interventions that are still under investigation. The American University of Beirut (AUB) in partnership with South for Construction (SFC) - “الجنوب للإعمار” -, and with the engagement of the affected communities, are herewith proposing a practical and rapid solution for the recycling/reuse of the construction demolition wastes (CDW) that will have a valuable outcome to impact positively on the built environment, the financial benefits, and the social fabric of communities.

Technically, the solution that is here being explored aims at repurposing the waste debris to be recycled and used as justifiable construction materials in the reconstruction/ retrofitting of the demolished/damaged habitations. In particular, the process to be adopted considered the crushing of the debris to transform into construction aggregate sizes, then to be used as a partial substitute for conventional aggregates consisting of natural fine sands and coarse gravels. Such an environmentally sound process will inherently contribute to the reduction of natural resource depletion, and thus present itself as one viable and sustainable construction practice.

In the present circumstances, and for practicable and efficient reasons, the waste debris were kept assembled on site “as is”, thus not sorted by material constituents and sizes. In this research, rubbles from 5 demolished sites in South Lebanon from Zraryieh and Ansar and the Southern Suburb of Beirut from Laylaki, Bir El Abed, and Sayed Hadi Highway were identified and studied. Then samples of these materials were taken to the crushing site, where part of each sample was crushed once and the other part was crushed twice. Then these samples were investigated in the labs and their physical, mechanical, and chemical properties validated as substitute construction aggregates (fine and coarse).

Multiple tests in stages and phases were conducted similarly per site to evaluate the physical, mechanical, and chemical properties of the crushed materials (Stage 1), with the aim to reach the optimal cementitious and concrete mixes from preliminary testing for each site, with the crushed aggregates at the two levels/sizes and considering the various replacement percentages considered (Stage 2). And using this optimal mix, further required tests on the concrete samples were conducted to assert the soundness and validity of the crushed debris or alternate aggregates as viable sustainable construction materials (Stage 3).

The current research and thesis focused on the technical aspect of CDW. This is complemented with other parallel work which has been or is being concurrently conducted on CDW management, economic feasibility, and policy advocacy with the proper authorities.