The worldwide annual production of ceramic bricks is currently about 1400 billion units and the demand for bricks is expected to be continuously rising. Quarrying operations for obtaining the clay are energy intensive and adversely affect the landscape. For environmental protection and sustainable development, many researchers have studied the partial/total replacement of natural clays, sands or inert fractions by waste materials to produce bricks through firing. However, there is no relevant bibliography on the use of recycled ceramic fractions (masonry fraction) from construction and demolition waste (C&DW) in the manufacturing of new bricks. This masonry fraction is currently considered as the low-grade fraction of mixed recycled aggregates, since concrete aggregates show a higher strength than masonry aggregates. The establishment of a high-grade product market for this masonry fraction would create an extra incentive for the production of a pure concrete fraction and pure masonry fraction during demolition works, rather than combine them in a mixed stony fraction.
We developed hollow fired clay bricks for interior use with a 10 V% replacement of the raw materials by the complete replacement of the coarser inert sand fraction, which serves as an opening substance, with the masonry fraction of C&DW. In order to assess the feasibility of the replacement of porphyry sand with crushed masonry waste, lab test samples were produced and compared with reference samples (with porphyry sand) in flexural strength tests. A “real life” sample, with crushed commercially available masonry aggregates, was produced to assess the need of further sorting of these aggregates. We established limit values for gypsum and mortar contamination based on quality testing and sulfate limits.
Afterwards, large-scale production tests were performed at the industrial production facilities of Dumoulin Bricks. The regular process for the production of hollow fired clay bricks with Yperian clay was used. Besides of the replacement of the opening substance (porphyry sand) with a crushed masonry fraction from selective demolition, the rest of the recipe was kept the same. The masonry fraction was not further sorted after the demolition process. The crushed mansonry fraction had a particle size <2 mm, but the used materials undergo a further comminution during the mixing process. By completely replacing the porphyry fraction (10 V%) with pre-processed demolition waste (<2 mm), we were able to produce bricks with a higher compressive strength and a slightly lower density. The produced bricks. Tested with the CEN/TS 772-22 procedure, the produced bricks show a freeze-thaw resistance under severe climate conditions (F2).
To conclude, VITO established a robust recycling route for selectively demolished masonry waste that does not require extensive processing steps. The produced bricks show no quality reduction compared with the reference bricks and comply to the quality requirements for the intended application (fired clay bricks for interior use).
This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 642085.
