RESISTANCE OF BASALT FIBRE IN THE ALKALINE ENVIRONMENT OF HYDRATING CEMENT SYSTEMS

Abstract

The paper presents studies aimed at substantiating the possibility of using basalt fiber as dispersed reinforcement in cement systems based on expanding binders with high energy of expansion (stressing cements). Alkalinity resistance of basalt fiber by the accelerated method by a four-hour exposure in a saturated solution of Ca(OH)2 at temperature t=95°С, which allows simulating the operation process within 10 years in the environment of the cement stone, has been investigated. Tensile strength of cement samples with basalt fiber treated by the accelerated method has been proposed as one of the criteria for estimating the quality of alkali-resistant fiber. The application of NC on a Portland cement base and expanding additive consisting of a mixture of highly reactive metakaolin and natural gypsum allowing a decrease in pH of the medium from values ≈12.13 to ≈11.25 is an alternative way of reducing the alkalinity of hydrating medium as the most favorable for basalt fiber location. A number of experimental studies have been conducted to determine the strength properties and self-strains of basalt fiber-reinforced selfs-tressing cement. Experimental and theoretical studies have revealed that basalt fiber has high alkali resistance. The introduction of basalt fiber in an amount of 5% of the binder mass makes it possible to increase compressive strength of the SSC by 35%, tensile strength at bending by 68%, with self-strain corresponding to 0.22% of free expansion and 2.74 MPa of self-stressing, respectively.