CONCRETES ON SECONDARY CRUSHED STONE AS A PROMISING MATERIAL FOR THE RIGID PAVEMENT BASE

Abstract

In the course of research, the efficiency of application of plasticizers of different type in concretes for bases of highways on secondary crushed stone is defined. In studies of concrete compositions, the type of crushed stone, secondary or granite, changed, which allowed to compare the properties of concrete on secondary crushed stone with the properties of concrete of similar composition on granite crushed stone. In addition, the type of sand changed: Bilyaevsky or Voznesenski quarry. As modifiers used additive lignosulfonate or superplasticizer polycarboxylate type MC-PowerFlow 3200. All concrete mixtures had equal mobility P2, which was provided by variation W/C (water-cement ratio). It was found that the concrete on the secondary crushed stone is characterized by a significantly higher W/C mixture due to greater porosity and damage to the surface of the coarse aggregate. The average density of concrete on secondary crushed stone is 4.2-4.4% lower compared to the average density of concrete on granite crushed stone. The average density of concrete on the larger sand of the Voznesenski quarry is 25-30 kg/m3 higher than the average density of concrete on similar gravel and finer sand of the Bilyaevsky quarry. In composites based on CEM III/A and using lingosulfonate additives, the compressive strength of concrete on secondary crushed stone is 12-13% lower compared to the strength of concrete on granite crushed stone and similar sand. However, when using the more efficient MC-PowerFlow 3200 additive, the difference in concrete strength on secondary and granite crushed stone is only 5.4% (29.8 MPa and 31.4 MPa, respectively). The strength of concrete on the sand of the Voznesenski quarry is 4-6% higher than the strength of concrete on similar gravel and finer sand of the Bilyaevsky quarry. It was found that the tensile strength when bending concrete on secondary and granite gravel when using the additive MC-PowerFlow 3200 was 2.75 MPa and 2.87 MPa, respectively, which differs by only 4%. Thus, the tensile strength of bending concrete on secondary crushed stone was almost no different from the tensile strength of similar concrete on granite crushed stone. This can be explained by the peculiarities of the aggregate with a porous surface, which is characterized by high adhesion to the cement-sand matrix. In general, the strength of concrete on secondary crushed stone using slag-containing cements allows them to be used effectively for road bases.