Interactions among the characteristics of concretes containing a high portion of micro-filler
Keywords:fine grain C&DW, micro-filler, concrete of high fluidity, density, compressive strength
Utilization of the construction and demolition waste (C&DW) for the production of building materials is discussed for a longer time worldwide, whether in the form of coarse aggregates or in the fine-grain form as a micro-filler/additive. The valorization of waste/by-products in the production of building materials can be improved by their modification using some treatment technologies.
The article presents the results of testing the concretes containing a high dosage of the C&DW that were previously adjusted into fine-particle powders. Those powders were prepared by the grinding and sorting of concrete, brick and glass to specific dimensions – under 250 μm. They were intended as a micro filler substitution of natural aggregate (NA) within the 0/4 fraction to the extent permitted by technological rules. Except for environmental reasons (saving the natural sources of NA), the high dosage of micro-fillers was intended for improving the technical parameters of concrete. The main goal was to attain a concrete of high fluidity, as it is in great demand by constructors. That is why also other parameters of concrete mixtures were optimized; the amount of water as well as the dosage of plasticizer were adjusted during mixing in order to keep the standard criteria.Next, a positive impact on the properties of hardened concrete was expected due to the effect of micro-fillers in the concrete microstructure. The results of these properties are presented and discussed in the paper, namely density, compressive strength, water absorption capacity and frost resistance. The analysis of the results is focused on the effect of an individual powdered material, on the interaction of the resulting properties of concretes, as well as on the changes of those properties in time, since the data were collected at 7, 28 and 365 days of hardening. Positive effect of fine-grain form of brick, glass and concrete on the compressive strength and partially on the frost resistance was found compared to the reference concrete, while it is not the case of water absorption capacity.