Abstract
Recycled aggregate concrete is a solution used to minimize the environmental impact of the concrete industry. Notwithstanding research worldwide validating structural applications of recycled aggregate concrete, specific design guidelines are lacking and are needed to address reservations of construction agents. Design guidelines should be based on reliability concepts, including the stochastic modeling of material properties and the calibration of design clauses through reliability methods. This paper concerns the concrete cover design of recycled aggregate concrete elements exposed to chloride ingress. Only coarse recycled aggregates produced from concrete waste are studied. The paper describes the chloride ingress model of fib Bulletin 34, presents experiments on the chloride ion migration of several analogue natural and recycled aggregate concrete mixes, tackles the stochastic modeling of the chloride migration coefficient, and calibrates concrete cover design for recycled aggregate concrete using reliability methods. The concrete cover design followed the deemed-to-satisfy provisions of Eurocode 2 and EN 206. The case studies used in the reliability analyses covered several design situations. A 5 mm increase of concrete cover is recommended as a simple option that ensures that the probability of depassivation due to chloride ingress on recycled aggregate concrete elements is equivalent to that for analogue natural aggregate concrete elements.
Highlights
The use of reinforced recycled aggregate concrete for structural purposes has been extensively investigated [1,2,3] and is a suitable solution to reduce the environmental impacts associated with landfill disposals and with the extraction of stone, since recycled aggregate concrete is made by replacing a fraction of natural aggregates (NA)
This paper addresses the consequences of the heterogeneity of RA on the design of concrete cover for chloride ingress-prone environments
(9.28%) and needs to be accounted for when batching; The 10 min water absorption of RA was 6.87% (74% of the 24 h water absorption). This value agrees with what has been reported in other publications [9,18,47] in which the same procedure [40] is used to estimate the water absorption over time; The density of RA (2478 kg/m3 ) is smaller than that of NA (2657 kg/m3 ). This is due to the smaller density of the attached mortar in comparison to the density of limestone
Summary
RA is used to designate coarse recycled concrete aggregates and RAC to designate concrete with replacement of NA with RA. The main environmental benefit of RAC is recycling CDW and the minimization of the consumption of NA (either produced from stone crushing in quarries or from fluvial dredging). Notwithstanding the demonstration of the technical feasibility of RAC through laboratory experiments [3], full-scale testing [5], and through pilot applications [6], the construction industry avoids RAC and opts for NAC. This is partly due to the lack of specific guidelines for RAC design
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