Abstract
The huge increase in production of construction and demolition waste (CDW) worldwide is leading to the valorisation of as recycled aggregates. One of the most promising alternatives is its use as a recycled aggregate in the manufacture of structural concrete, which motivates the study of the dynamic behaviour of these materials in order to ensure their suitability for use in elements subjected to dynamic loads. This work evaluated the resonant compressive fatigue behaviour of structural concretes with 25% or 50% recycled mixed aggregates, either individually or in combination with 25% recycled cement of clay-based materials both from CDW. All mixes were subjected to compressive fatigue tests using the accelerated Locati method. Regarding the fatigue limit, the results showed that for all mixes, it was between 30% and 45% of the compressive strength. In addition, a correlation was also found between the resonance frequency of the test and the deformation suffered by the specimen. This correlation enabled the estimation of the fatigue limit through a more stable parameter than the strain measured by strain gauges, namely, the resonance frequency. In addition, it was found that the resonance frequency of the test changed as the specimen damage increased. This observation enabled the estimation of the fatigue limit through a more stable parameter than the strain measured by strain gauges, namely, the resonance frequency.
Highlights
Concrete is the most widely used and versatile material in construction [1]
The presence of mixed recycled aggregates in the concretes increased the strain recorded during the resonance compressive fatigue tests
The resonance frequencies were lower in the concretes with mixed recycled aggregates (MRA) because the stiffness of the system provided by the presence of MRA increased the strain suffered by the specimen
Summary
Concrete is the most widely used and versatile material in construction [1]. In 2019 ~27 Gt of concrete was consumed worldwide [2], requiring the production of ~19 Gt of natural aggregates (NA) and ~4.1 Gt of Portland cement [3]. The recent review by Tang et al [39] shows that the partial substitution of up to 30% by weight of recycled clay waste from CDW as SCM in the manufacture of concrete can improve, if the fineness of the waste is adequate, the properties of new concretes incorporating these new SCMs in the cement with respect to conventional concrete, as well as being an effective solution to mitigate the pollutant emissions associated with cement production, with a reduction of up to 8.1% of cement produced [40] With this objective, the innovation of this research is to analyse the individual and joint effects of the incorporation of mixed recycled finely ground clay-based waste as SCM to cement (RPW-CDW) and the coarse fraction of mixed recycled aggregates in the study of resonant fatigue behaviour from structural concretes.
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