# Life Cycle Assessment of Substitutive Building Materials for Landfill Capping Systems in Vietnam
###### Abstract  
The growing population and urbanization rates in developing countries causes huge pressure on the construction sector to aid the equivalent infrastructure growth. Natural resources are essential to attain the required infrastructure needs. The demand in the construction sector for materials causes significant environmental effects due to the higher consumption rate of finite natural resources. To address such an issue, the study focuses on the landfill capping application demand in Vietnam, based on its extensive landfill presence in its current state and their need to be closed in the years ahead. The study considers utilization of secondary raw materials arising from industrial or anthropogenic waste as an alternative material as a landfill mineral sealing layer, to replace the dependence on conventional clay and bentonite. The selected alternative materials were tested to satisfy the permeability conditions for the landfill sealing layer standards, where results indicated very low permeability values for the mixtures, meeting German quality requirements which require \(\mathrm{k}\leq 5\times 10^{-9}\) m/s for landfill class I (landfills without further environmental requirements) and \(\mathrm{k}\leq 5\times 10^{-10}\) m/s for class II (conventional landfill for non-hazardous waste) for sealing layers of landfills. Further, the various mixes of alternative mineral layers in a life cycle analysis for a functional unit of one hectare landfill mineral sealing layer resulted in lower environmental footprints than the conventional layer. The results of the mineral sealing layer showed that the higher bentonite composition of about 20% in the mix ratio and transport distance of 65 km for the ashes increased the overall environmental footprint of the mix. In this case, mix 6 and mix 7, having 20% bentonite, contended to possess higher impacts, despite the alternative ashes holding zero allocation, along with the 65 km transportation distance associated with ashes. The avoidance factor over the alternative mixes has an effective approximate 25-50% Global Warming Potential (GWP) impact reduction. There was a significant mineral resource scarcity impact reduction on the use of secondary raw materials. substitutive building materials; soil mechanics; life cycle assessment; landfill capping; mineral sealing layer +
Footnote †: journal: Applied Sciences  
from domestic, industrial, and construction sectors is collected and disposed of in Municipal Solid Waste landfills [1; 4]. A properly designed sanitary landfill isolates waste materials from the surroundings. A sanitary landfill might experience long term failure in its liner system efficacy due to long-term environmental effects [5; 6]. Therefore, landfill sealing technologies comprise low hydraulic conductivity engineered layers as part of the covers and bottom liners, for which clays and geosynthetic materials are conventionally used. However, in the last few decades, landfill designers around the world have faced an increasing scarcity of feasible primary raw materials for landfill construction, particularly in terms of the sealing layer with its special technical requirements. Therefore, an increasing number of mixed wastes have been suggested as alternative landfill barrier materials. The general sources of secondary mineral materials might be: (a) residues of agricultural activities, like ashes from agro-waste [7; 8]; (b) metallurgical or mineral waste [7; 9]; and (c) mining waste, for instance tailings' sediments. However, tailings' sediments are excluded due to quality reasons, in case they contain too high metal contents or flocculation agents, as described in [10]. Moreover, for landfill applications, particularly the sealing layer, it is necessary to utilize waste streams with constant availability and suitable soil mechanical properties.