Abstract
The paper focuses on the reuse of crushed asphalt (GA) as a partial replacement (up to 20%) of natural aggregates for concrete manufacture. Addition of GA aggregates produced a positive effect on workability loss. The GA mixes, however, showed a significant tendency to bleed and segregate at the highest replacement percentage applied. GA led to a decrease of compressive strength in concrete (with respect to that of the reference concrete) up to 50% due to the weakness of the cement paste / recycled aggregate interface. To compensate for this negative effect, a reduction of w/c for the GA concretes was necessary. A decrease of w/c allowed the GA concretes to show drying shrinkage values substantially similar to those of reference concrete with the same cement factor. The experimental results confirmed the possibility of partial substitution (max. 15%) of natural aggregates with crushed asphalt for making concrete.
Highlights
In the last 15 years, sustainability has become an important research topic in the field of construction and building materials
Despite the higher water absorption of GA with respect to natural aggregates, the GA addition produced positive effects on workability retention. This could probably be attributed to the rounded shape of natural aggregates and to the presence of oil traces that act to superplasticizer for granting higher initial fluidity and prolonged workability
The compressive strength decrease is evident for the highest substitution of natural aggregates; at 20% substitution, the compressive strength decrease of GA concrete was about 50% with respect to reference concrete (RC). This could probably be ascribed both to the presence of oils in bitumen that adversely affect the kinetics of cement hydration and to a poor aggregate-cement paste interface, as evidenced by the failure paths during the compressive strength tests
Summary
In the last 15 years, sustainability has become an important research topic in the field of construction and building materials. 40% arises as construction and demolition waste (C&DW) [1]. The building industry, represents a significant nature-consuming activity [2], with the quarrying activities for the production of aggregates for concrete being expensive in terms of “environmental costs”. In this view, in the last decade, much research [3,4,5,6,7,8,9,10,11] has been oriented to.
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