Abstract
This work analyzes the technical and economic viability of using coarse recycled aggregates from crushed concrete in shotcrete, as a primary lining support in tunnels. Four incorporation ratios of coarse natural aggregate (CNA) with coarse recycled concrete aggregates from concrete (CRCA) were studied: 0%, 20%, 50% and 100%. The mechanical properties of the dry-mix shotcrete were obtained in an independent experimental campaign. Initially, the technical viability of CRCA shotcrete was validated for deep rock tunnels, based on the convergence-confinement method. Two cases were studied to determine the equivalent thickness for each combination of replacement ratio using CRCA shotcrete: (i) similar stiffness and (ii) similar yield stress. Subsequently, an economic assessment was performed. The stiffness criterion increased the thickness below 10% in both the 20% and 50% replacement ratios, which shows their technical viability with very marginal cost increase (<5%). On the other hand, the maximum pressure criteria required higher increments, close to 30% in the 50% replacement ratio. A full replacement was proven to be impracticable in both analyses.
Highlights
The construction sector is considered one of the main players in the generation of environmental impact
Chan [4] and Bravo et al [2] evaluated the performance of recycled aggregate concrete (RAC), finding that the nature of recycled aggregates (RA) strongly influences their binding capacity to the new cement paste, affecting the mechanical properties of the resulting concrete
It should be referred that the mechanical tests were always performed on core specimens with a diameter of 98 mm
Summary
The construction sector is considered one of the main players in the generation of environmental impact. Chan [4] and Bravo et al [2] evaluated the performance of recycled aggregate concrete (RAC), finding that the nature of RA strongly influences their binding capacity to the new cement paste, affecting the mechanical properties of the resulting concrete. These authors concluded that the use of these aggregates in concrete production is feasible. A technical and economic assessment of different dry-mix shotcrete compositions, incorporating coarse recycled concrete aggregates (CRCA). It is demonstrated that limited incorporation ratios of CRCA can be a valid alternative from a technical and economic perspective
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