Properties of concrete with brick waste aggregate

The properties of concrete with brick waste aggregate are considered and it is established that as the amount of large aggregates - brick waste - increases, an increase in the water-cement ratio is observed. The mobility of concrete with a brick waste content of 50% corresponds to class P1, at 40% – P2, at 35% – class P3. Increased water consumption is necessary due to the effect of water absorption of porous brick chips, as well as maintaining the mobility of the concrete mixture, which changes significantly quickly over time. The initial settlement of the concrete mixture cone is 14–15 cm, after 40 minutes it decreases to 3–6 cm, and after 1 hour the mixture completely hardens. An increase in the content of coarse fillers leads to a decrease in the compressive strength of ceramic concrete. Thus, concrete samples with a filler content of 35% can be classified as class B27.5, samples with 40% – to B25, and 50% – to class B22.5. Electron microscopy was used to study the contact zone “cement stone – aggregate” on samples with crushed stone from brick waste and crushed granite aggregate. The results revealed that the adhesion strength of the aggregate to the cement stone is significantly higher than the strength of the aggregate itself, and the high surface roughness of lightweight secondary aggregates from broken bricks ensures good adhesion between the cement stone and the aggregate. In addition, the increased deformability of the aggregate reduces the negative impact on the shrinkage of cement stone, which has a positive effect on the structure of concrete, preventing the appearance of shrinkage microcracks.