Expert work has been carried out to establish quality indicators for three types of concrete paving slabs: "Auriko", "Paving stone", "New City". The tests were carried out on selected samples in accordance with GOST 17608-2017. According to the test results, it was determined that only the samples of "Paving stones" tiles meet the requirements of GOST, other types of tiles revealed non-compliance of the studied samples with GOST 17608 in terms of water absorption and frost resistance.Frost resistance tests for Aurico and Novy Gorod product samples were interrupted after 15 freeze-thaw cycles due to the destruction of the samples.

Keywords: paving slabs, concrete, compressive strength, frost resistance, surface defect "sink"

The results of studies of the effect of mineral additives of natural and man-made origin on some properties of fine-aggregate concrete with the introduction of a mineral additive from 10 to 25% of the cement weight instead of either a part of cement with an increase in the value of W/ C, or a part of sand with a constant value of the value of W / C are presented. A slight, up to 3%, change in the average density of concrete was revealed. A decrease in the E-modulus from 4 to 14% was recorded when replacing a part of cement, while an increase in the flexural strength, depending on the dosage, was up to 26% (marshallite) and 6% (chemical water treatment sludge), and a decrease in the compressive strength was from 10 to 22%. When replacing part of the sand, an increase of up to 10% of the E-modulus, the flexural strength from 19 to 38% (marshallite) and up to 11% (chemical water treatment sludge) was recorded. The increase in the compressive strength, depending on the type and dosage of the additive, ranged from 8 to 20%. No significant effect of additives on the porosity of cement stone was revealed.

Keywords: mineral additive, fine-aggregate concrete, flexural strength, E-modulus, shrinkage, water absorption