CONCRETE

UDC 624.21

[:en]Bonin K.[:ru]Бонин К.[:] [:en]Wacker Chemie AG, Burghausen, Germany[:]

Alitinform №1 (66) 2022 г. 50-57 p.

Abstract

Self-filling concrete compounds (SFCCs) are a kind of two component systems, consisting of coarse aggregates and special drymix mortar compositions. Those customized drymix mortars are formulated with additives and specific, flowable dispersible polymer powders to obtain the required performance — mainly compressive strength, setting time, flow behavior and abrasion resistance.
In the application of SFCC the desired particulate material: Aggregates, such as gravel or grit (component 1) and the drymix mortar (component 2) — are present separately. On the construction site, the grit is first spread on or into the prepared casting mold, the drymix mortar is mixed with water and then pumped over the grit layer. The highly flowable mass quickly fills the air voids between the grit particles, which constitute about 50 % of the volume, and binds them to form a solid concrete structure. Instead of fully filling, it’s also possible to generate a porous agglomeration while spraying the SFCC onto the aggregate and generate single particle bonding, to get a previous structure. Depending on the formulation, the system sets very quickly, in even less than an hour, if so desired.
The flow characteristics, or the rheology, of the SFCC are particularly important. The SFCC has to contain a flowable dispersible polymer powder that promotes flow and stabilizes the very liquid mixture in order to prevent segregation or separation during the mold filling process.
In contrast to conventional concrete, SFCC is almost free of shrinkage, as particles are already fully in direct contact with each other. The shrinkage in regular concrete is usually up to two percent. The filled voids in the SFCC application experiment are at most one centimeter long and shrinkage is correspondingly small — tension or cracks therefore cannot occur in the casted element easily.

Key words:

self-filling concrete mixtures, concrete shrinkage, use of gravel and crushed stone, dry building mixtures