Preliminary study on the upcycle of non-structural construction and demolition waste for waste cleaning

Abstract

This study proposes a method to convert non-structural calcium-rich construction and demolition waste fines into adsorbents of heavy metal ions by mixing waste fines with diammonium hydrogen phosphate solution to produce hydroxyapatite, which has high surface areas and excellent ion-exchange capacity with heavy metal ions. As a result, environmental polluting waste is converted into environmentally cleaning material. Waste putty powders was chosen as the representative waste to investigate the detailed formation process of hydroxyapatite and the key reaction parameters of the reaction. Results showed that hydroxyapatite can be produced on waste putty particles. Higher ageing temperatures or longer ageing duration are beneficial to the yield and crystallinity of the produced hydroxyapatite. Adsorption testing confirmed that Ni 2+ can replace Ca 2+ in the hydroxyapatite lattice, leading to the formation of a new crystal, arupite (Ni 3 (PO 4 ) 2 •8H 2 O), and contributing to a modest adsorption capacity for Ni 2+ (15 mg/g) for the hydroxyapatite-containing waste putty. Citation/Citar como: Chen, P.; Chen, X.; Wang, Y.; Wang, P. (2020) Preliminary Study on the Upcycle of Non-structural Construction and Demolition Waste for Waste Cleaning. Mater. Construcc. 70 [338], e220 https://doi.org/10.3989/ mc.2020.13819 RESUMEN:Estudio preliminar sobre el empleo de residuos de construcción y demolición no estructurales para la eliminación de residuos. Este estudio propone un método para convertir residuos de construcción y demolición no estructurales, ricos en calcio y pulverulentos, en adsorbentes de iones de metales pesados mezclándolos con una solución de hidrógenofosfato de diamonio para generar hidroxiapatita, la cual presenta una elevada área superficial y una excelente capacidad de intercambio iónico de iones de metales pesados. De este modo, un residuo contaminante se convierte en un material que limpia el medio ambiente. Se seleccionó residuo en forma de masilla en polvo como residuo representativo para investigar en detalle los procesos de formación de hidroxiapatita y los parámetros clave implicados en la reacción. Los resultados mostraron que la hidroxiapatita se puede producir en las partículas de los residuos empleados. La producción y la cristalinidad de la hidroxiapatita se ve favorecida por temperaturas de envejecimiento elevadas y prolongadas. Los ensayos de adsorción confirmaron que el Ni 2+ puede sustituir al Ca 2+ en la estructura de la hidroxiapatita, formándose un nuevo mineral, arupita (Ni 3 (PO 4 ) 2 •8H 2 O), y contribuyendo a una adsorción modesta de Ni 2+ (15 mg/g) por parte de la masilla de residuos con hidroxiapatita.

A study on the effects of the fractal characteristics of aggregates on the mechanical behavior of cemented sand and gravel

“…Under the same stress, more ITZ units around the polygonal aggregates will show damage and fracture than around the circular aggregates. This conclusion is consistent with that in the reference works (9,36,37).…”

The use of recycled aggregates in the construction sector: a scientific bibliometric analysis

“…In this context, and in accordance with a framework for sustainable development, this type of waste has received widespread attention around the world, resulting in a significant number of scientific documents published in recent years. The growth in scientific publications has been quick and it has been motivated by the important environmental impacts generated by C&DW (9), focussing on possible applications of recycled aggregates (RA) such as concrete (10)(11)(12)(13), prefabricated concrete (14), non-structural concrete (15), masonry mortars (16)(17)(18) and road or pavement applications (19)(20)(21), among others of the most representative.…”