Microwave Radiation as a Pre-Treatment for Standard and Innovative Fragmentation Techniques in Concrete Recycling

Abstract

Recent advances in concrete recycling technology focus on novel fragmentation techniques to obtain aggregate fractions with low cement matrix content. This study assesses the aggregate liberation effectiveness of four different treatment processes including standard and innovative concrete fragmentation techniques. Lab-made concrete samples were subjected to either standard mechanical crushing technique (SMT) or electrodynamic fragmentation (EDF). For both fragmentation processes, the influence of a microwave weakening pre-treatment technique (MWT) was investigated. A detailed analysis of the particle size distribution was carried out on samples after fragmentation. The >5.6 mm fraction was more deeply characterized for aggregate selective liberation (manual classification to separate liberated aggregates) and for cement matrix content (thermogravimetric measurements). Results highlight that EDF treatment is more effective than SMT treatment to selectively liberate aggregates and to decrease the cement matrix content of the >5.6 mm fraction. EDF fully liberates up to 37 wt.% of the >5.6 mm natural aggregates, while SMT only liberates 14–16 wt.%. MWT pre-treatment positively affects aggregate liberation and cement matrix removal only if used in combination with SMT; no significant effect in combination with EDF was recorded. These results of this study can provide insights to successfully implement innovative technology in concrete recycling plants.

Effect of Crushing Method on the Properties of Produced Recycled Concrete Aggregates

“…It is also used to reduce waste dimensions before crushing. The produced aggregates are mainly used in less demanding applications such as bulk fill, fill in drainage, primary foundations, embankments and levelling work [9,[12][13][14] which leads to concrete "down cycling".…”

Experimental Investigation of Concrete with Recycled Aggregates for Suitability in Concrete Structures

“…In European countries, 320-380 million tons of this type of waste is generated every year [4] and in China alone this is about 640 million tons annually [5,6]. A lot of research has been conducted all over the world on recycled aggregates and their application in the production of structural concrete [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Nevertheless, new possibilities of using various types of waste for the production of aggregates used in structural concrete are constantly being sought.…”