Cemented backfill with low-grade natural sand

Abstract

The subject of this research is cemented backfill mixtures made using fine and very fine natural sand with increased content of clay and flour particles. Aimed to study optimizability of grain size composition of low-grade fine and very fine natural sand, the physical and mechanical properties of sands from Bolshie Mayachki deposit in the Belgorod Region and blast-furnace granulated slag from metallurgical processing at Severstal were analyzed. Optimization of granular composition included enlargement of size modulus, reduction of specific surface of grains and decrease in the content of clay and flour particles. Initial sand was brought to standard quality level by introduction of slag sand (fractions of 0-5 mm). Then, the grain composition, particle size modulus, clay and dust-like particles content and specific surface area of each composite aggregate grain were determined using the methods described in the article. According to the test results, the increase in the proportion of slag in the composite aggregate leads to the decrease in the water demand due to enlargement of particles and lower content of clay components, which makes it possible to obtain compositions for cemented backfill with strength of 1–10 MPa at the reduced consumption of cement (by 7% on average) and with the preserved rheological characteristics.