Selection of compositions and investigation of properties of finegrained self-compacting concretes based on secondary (recycling) crushed stone and sand

Introduction. The replacement of traditional (natural) aggregates with industrial waste in the production of concrete is one of the most important reserves for saving material and energy resources in the construction industry of the Russian Federation. Scrap of concrete, reinforced concrete structures and products, which is formed during the demolition of physically and morally outdated buildings and structures, as well as during their destruction after natural disasters and armed conflicts, is one of the most promising wastes from the point of view of recycling in concrete technology. The use of concrete waste will practically ensure the implementation of the most important principle of waste-free technological processes (in the production of prefabricated and monolithic concrete and reinforced concrete structures) and create conditions for the fulfillment of important social, economic and environmental tasks.

Aim. Selection of compositions and study of the standardized parameters of self-compacting concretes based on recycled (concrete) crushed stone and sand using fine fractions of recycled sand as a mineral additive, as well as comparing their properties with self-compacting concretes based on natural crushed stone and sand of a similar composition.

Materials and methods. For the research, recycled (concrete) and granite (natural) crushed stone according to State Standard 8267-93 were used as coarse aggregates. Recycled (concrete) and natural sand according to State Standard 8736-2014 were used as fine aggregates. Fine fractions of recycled sand were used as a mineral additive. Portland cement according to State Standard 31108-2020 was used as a binder. The superplasticizer Polyplast Target according to State Standard 24211-2008 was used as an additive. The mixing water was used according to State Standard 23732-2011.

Results. The rheological properties, frost resistance and abrasion resistance of fine-grained self-compacting concretes based on recycled aggregates are identical to those of self-compacting concretes based on the traditional aggregates. The strength, density and waterproof grade of fine-grained self-compacting concretes based on recycled aggregates are lower than those of fine-grained self-compacting concretes based on traditional aggregates.

Conclusions. Based on the results of the work carried out, it was revealed that secondary (recycled) crushed stone and sand, as well as fine fractions of secondary (recycled) sand (with a specific surface area of at least 230 m²/kg), are suitable for the production of self-compacting concretes. Self-compacting concretes based on secondary (recycled) crushed stone and sand can be used in the construction industry of the Russian Federation along with self-compacting concretes based on traditional crushed stone and sand.

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