THE EFFECT OF MODIFIED ADDITIVES ON STRENGTH AND FROST RESISTANCE IN FIBROUS CONCRETE OF RIGID ROAD PAVEMENTS

Abstract

Abstract. The research is devoted to the development of compositions of modified fiber concrete of rigid road pavements with high strength and frost resistance through the use of metakaolin and a polycarboxylate type superplasticizer. The compressive strength, tensile strength under bending and frost resistance of concrete and fiber concrete of rigid road pavements were investigated according to the 4-factor optimal plan. In the experiment the amount of concrete components varied: Portland cement, polypropylene fibers, metakaolin, the polycarboxylate type additives Coral ExpertSuid-5. All mixtures had equal mobility P2 and their W/C depended on the composition of concrete. The use of polypropylene fiber and metakaolin necessitates an increase of W/C to maintain the mobility of the mixture. Increasing the amount of Coral ExpertSuid-5 additive in concrete to 0.9-1% allows to reduce significantly W/C of the mixture. Metakaolin as an active mineral additive increases the compressive strength and tensile strength of concrete. Rational in terms of increasing strength is the amount of metakaolin at the level of 20..22 kg/m3. With an increase in the amount of Coral ExpertSuid-5 additive to 0.9..1% due to a decrease of W/C, the compressive strength of concrete increases by 5..7 MPa, and the tensile strength increases by about 0.5 MPa. Due to the introduction of polypropylene fiber, the tensile strength of concrete in bending increases by 0.6..0.9 MPa. But dispersed reinforcement does not affect the compressive strength of concrete. The developed fiber concrete using a rational amount of modifiers, depending on the amount of Portland cement in the composition, has a compressive strength from 55 MPa to 70 MPa and tensile strength from 8 MPa to 9.5 MPa. The high strength of fiber-reinforced concretes allows their use in road pavements with the highest load. Frost resistance of concrete increases by 50 cycles or more when using fiber in an amount of 1.5-2 kg/m3. Due to the use of a rational amount of modifiers (0.8-1% Coral ExpertSuid-5 additive and 15-20 kg/m3 metakaolin), frost resistance of concrete and fiber concrete increases by 50-100 cycles. The developed modified fiber concretes of rigid road pavements depending on the amount of Portland cement in the composition have frost resistance from F350 to F450, which ensures their sufficient durability.