Evaluation of environmental friendliness of concrete paving eco-blocks using LCA approach

Abstract

Purpose: The demand for green construction materials and eco-products is burgeoning globally due to the shortage of natural materials and the relevant environmental consequences of natural materials. In addition, the management of rapidly increasing construction and demolition (C&D) waste and waste glass is in serious concern due to the shortage of landfills and associated environmental burdens for landfill disposal. Concrete paving eco-blocks using recycled materials derived from locally generated C&D waste and waste glass have been developed in Hong Kong and achieved its current advanced form with the continuous improvement. Therefore, this study aims to assess and compare the environmental impacts and sustainability associated with the natural blocks manufactured with virgin materials and three generations of the eco-blocks manufactured with recycled C&D waste and waste glass by the lifecycle assessment (LCA) techniques. Methods: For evaluating the environmental performance of concrete paving blocks, the IMPACT 2002+ method was used for lifecycle impact assessment with the functional unit of 1 t of blocks production. This study considered the “cradle-to-site” system boundary, which includes raw material extraction/production, raw material collection and transport to blocks manufacturing site, blocks manufacturing, and transport of the produced blocks to use sites. First-hand data were collected from a local eco-block manufacturer. Sensitivity analysis was conducted for different raw material inputs to investigate the variation of the results. Results and discussion: The findings demonstrated that as compared to the natural blocks, the eco-blocks consumed 26–32 % lower energy, emitted 17–20 % lower greenhouse gases (GHG) in CO2 eq. as global warming potential, 22–29 % lower SO2 eq. as acidification potential, and 20–26 % lower PM2.5 eq. as respiratory inorganics potential, depending on the types of eco-blocks. The proposed manufacturing process has the higher savings for all impacts categories for the eco-blocks. In addition, second generation eco-blocks induced the lowest impacts compared to other two types of eco-blocks. Conclusions: In summary, the eco-blocks have significant environmental gains which could help minimize the waste management problem, reduce natural resource depletion, and promote green consumption. The paper provides a method to facilitate the construction industry to choose sustainable materials to minimize environmental damages and promote the sustainable management of wastes. In addition to establishing a basis for choosing materials, the paper compares alternative manufacturing processes of concrete paving blocks for promoting green construction.