Study of the strength and durability of sand concrete with the use of secondary mineral raw materials

Abstract

The replacement of natural sand and part of the clinker binder with secondary mineral raw materials alters the structure of sand concrete unevenly across durability criteria, and this divergence stays outside the field of view in mix design. Strength and frost resistance respond to ash-slag mixture, crushed concrete screenings and ground ceramic brick in a manner opposite to carbonation resistance, so an assessment based on one indicator overstates the service potential of the material. The aim is to relate the type and proportion of the secondary component to the strength, frost resistance and predicted service life of sand concrete under the carbonation criterion. An author's strength model with factor decomposition by chain substitutions has been built, frost resistance calculated against GOST 10060-2012, and carbonation depth predicted for six mixes. Replacing 20% of the sand with ash-slag mixture raises the residual strength after 200 freezing and thawing cycles from 90.9 to 93.7%, while reducing the predicted service life at a 20 mm cover from 85 to 59 years. The divergence shows that secondary raw materials shift the limiting degradation mechanism towards carbonation, and the required cover thickness becomes a function of the replacement ratio.