Influence of Heterogeneity, Typology, and Contaminants of Recycled Aggregates on the Properties of Concrete

Background:

The depletion of raw material resources, the preservation of the environment, and the need to compensate economic imbalances drive research efforts regarding the application of Construction and Demolition Waste (CDW) in concretes.

Objective:

This paper aimed to assess the influence of the heterogeneity, typology, and presence of contaminants of CDW (collected in different seasons and locations) on the mechanical properties and durability of concretes.

Methods:

Characterization procedures were performed for the aggregates (visual quantification and physical properties of the constituents), and for the concretes (compressive strength, splitting tensile strength test, modulus of elasticity, water absorption, porosity, electrical resistivity, carbonation depth, and digital microscopy). The replacement rate of natural aggregate for CDWA was of 20% in three different particle sizes: sand, gravel 0, and gravel 1.

Results:

The characteristics of the samples of CDW were very variable, influenced by the season and location of collection. The presence of materials with elevated porosity (ceramics, mortars) was observed in some samples and required increases in mixing water volume to keep the concretes’ consistency. A wide variation in mechanical properties caused by the CDWA constituents was also observed. Regarding the durability of the concretes, it was proven the greatest sensibility of this property to contaminants, thus requiring the removal of deleterious materials to using CDWA in structural concretes in order to avoid the formation of vesicles and guaranteeing their life span.

Conclusion:

The heterogeneity, typology and contaminant content significantly influence the analyzed properties. Besides, the segregation of waste at source makes the use of CDWA feasible in concretes.

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