Resistance of Fine Concrete on Concrete Scrap Aggregate

Every year millions of cubic meters of concrete and reinforced concrete waste are formed worldwide. In Russia, the annual increase in scrap from the accumulation of defective structures and from the dismantling of old buildings is equal to 15–17 million tons. No more than 5% of this amount of reinforced concrete waste is recycled, and the rest is dumped in specialized landfills. Such actions have a negative impact on the environmental situation. Recycling and use of reinforced concrete waste in production reduces the cost of production, frees up land areas currently used as landfills, and thus - significantly improves the environmental situation. Researches on concrete recycling are conducted in our country, Japan, the USA. The influence of concrete scrap aggregate on the performance characteristics of concrete was found out. Features of concrete scrap aggregate are mainly determined by the fact that after crushing the concrete on aggregate grains there are layers of mortar component or thin films of hydrate phases, which leads to increased adhesion of the forming cement matrix to the aggregate. In the process of secondary crushing most of the cement film on the surface of acidic aggregate is carbonized, so that both positively and negatively charged particles of hydrate phases are deposited in the contact zone, which has a beneficial effect on reducing the conductivity of the contact zone for aggressive ions and increasing its durability. The paper shows the possibility of using secondary concrete for concrete products in contact with sulfate environments.