Theoretical approach to prescribing dosages basalt fiber for dispersed reinforcement of fine-grained cement composites on expanding binders

Abstract

In modern construction the use of basalt fiber as a reinforcing component of fine-grained cement composites is restrained by a number of factors. The main one is the dosage of basalt fiber, namely, the lack of a unified methodology for assigning the optimal amount of fiber introduced into the cement composite in order to increase its physical and mechanical properties. The purpose of this work is to develop a theoretically justified approach to the appointment of doses of basalt fiber, taking into account the peculiarities of formation of cement structure with subsequent experimental approbation. In the introduction, the relevance of the research is indicated. A transit zone has been singled out as a structural component. The specific features of structure formation and the effects accompanying the formation of the transition zone are indicated. Approaches for optimization of the transition zone properties have been suggested, including due to simultaneous introduction of expansive additives on the basis of high-base metakaolin and disperse reinforcement. Basalt fiber has been chosen as disperse reinforcement as a compatible material with cement stone, which has improved adhesion characteristics. And due to commensurability of diameter of a monofilament with diameter of a cement grain it allows realizing the concept of 3D-reinforcement at a microlevel. In the main part of the paper, a calculation model is proposed which is based on a hierarchical representation of the cement composite structure with the transit zone separated into a separate element forming a so-called “effective” filler together with the filler. In this case, the dosage of basalt fiber is assigned on the basis of the condition of reinforcing the active cement matrix while ensuring coverage of each monofilament with a dense layer of cement stone. Verification has been carried out taking into account the available own experimental data and the data of other researchers.