Influence of Recycled Precast Concrete Aggregate on Durability of Concrete’s Physical Processes

Abstract

The research presented in this article analysed the influence of incorporating precast concrete waste as an alternative to coarse aggregate in self-compacting concrete to generate new precast elements. The experimental study involved the characterization of recycled aggregate and the design of the mix of the new self-compacting concrete (SCC). The experimental study evaluates the physical processes that affect the durability of concrete with percentages of incorporation such as 20%, 50% and 100% of recycled aggregate. Two types of SCC were manufactured with minimum compressive strength of 30 MPa and 45 MPa. The properties analysed were density of hardened SCC, shrinkage cracking, freeze-thaw resistance, resistance to ageing by thermal shock and abrasion resistance. The results obtained were compared with those of the control concrete, observing great capacity of the SCC under physical aggressions that affect durability. The results of this research show that it is possible to use the recycled aggregate coming from precast pieces in order to the manufacture of self-compacting recycled concrete in the same precast industry. However, high loss of proprieties occurs for a 100% substitution, while for 20% and 50%, the variations with respect to control concrete are smaller. In addition, taking advantage of this waste to incorporate it back into the production chain contributes to more sustainable construction.

¿Por qué el efecto del árido de hormigón reciclado en la resistencia a compresión del hormigón autocompactante no es homogéneo? Una revisión bibliográfica

“…• La fracción gruesa (>4 mm) tiene mortero adherido al propio AN, lo cual explica la mayor densidad, la menor absorción de agua y la mayor porosidad de esta fracción en comparación con el AHR fino (24). Este mortero adherido también provoca la aparición de las Zonas Interfaciales de Transición (ZIT), zonas de unión entre el árido y la matriz cementicia, menos densas y más débiles que al utilizar AN (25).…”

“…El hormigón utilizado en la industria de los prefabricados suele tener una mayor resistencia debido a las características singulares de los elementos que se fabrican en ella. Además, la presencia de los contaminantes antes mencionados suele ser notablemente menor (24). Por lo tanto, el AHR procedente de la industria de la prefabricación tiene mejores propiedades para su uso (mayor resistencia, menor cantidad de componentes nocivos...), lo que conduce al desarrollo de HAC de mayor resistencia y, en general, con un mejor comportamiento en estado endurecido (43).…”

“…Así, el uso de un 100 % de AHR sin una compensación total del agua absorbida a mayores como consecuencia de la mayor absorción de agua de este residuo en comparación con el AN puede permitir la obtención de un HAC con una resistencia a compresión superior a la del hormigón fabricado con un 100 % de AN (8). Esta solución es generalmente adecuada para el AHR grueso, ya que la presencia de componentes de naturaleza diferente al hormigón (ladrillo, yeso…) es generalmente reducida, incluso si procede de trabajos de demolición, por lo que no alteran el comportamiento esperado del AHR (24). Sin embargo, la situación es completamente diferente en relación con el uso del AHR fino, debido a su mayor influencia en la microestructura y la porosidad del HAC.…”

Environmental Performance of Deconstructable Concrete Beams Made with Recycled Aggregates

“…About 7% of the world's carbon dioxide emissions come from the cement industry [1]. Added to this, there is still great concern about the extraction of raw materials and the large amount of unexploited Construction and Demolition Waste (CDW) [2,3]. There are also studies that analyze the feasibility of using natural by-products as aggregates for concrete, such as wood shavings [4], bamboo waste [5], rice husk [6] and palm oil clinker [7].…”

Effects of Freeze-Thaw and Wet-Dry Cycles on Tension Stiffening Behavior of Reinforced RAC Elements

“…The continuous development of the construction and infrastructure sectors has become a global concern in regards to sustainability issues, due to the high consumption of nonrenewable natural resources as raw materials and the massive production of Construction and Demolition Waste (CDW). The use of CDW to produce Recycled Concrete Aggregate (i.e., RCA identifying recycled aggregate obtained from concrete debris) can be an effective way to mitigate these negative environmental impacts [1][2][3].…”