Improving the operational characteristics of reinforced concrete products through the use of dispersed reinforcement and active mineral additives

Abstract

The service life of a precast reinforced concrete product results from both the resistance of concrete to destructive actions and the ability of the section to restrain the opening of normal cracks under sustained loading. Separate assessment of the effect of dispersed reinforcement and the effect of an active mineral additive leaves open the question of which component governs the increase in service life and how these components interact. The aim of the study is a quantitative separation of the contributions made by fibre reinforcement and by a mineral additive to the strength and corrosion characteristics of a factory-produced element. The calculation relies on the author's two-factor model calibrated against the normalised characteristics of SP 63.13330.2018, SP 360.1325800.2017 and GOST R 59535-2021, followed by verification of a model solid-section slab for the strength of the normal section and for crack opening. At a steel hooked-end fibre volume content of 1,5% and a replacement of 10% of the binder with condensed silica fume, the cube strength rises by 38,9%, the residual flexural tensile strength reaches 3,90 MPa, the frost resistance grade increases from F2200 to F2400, and the section utilisation ratio for sustained crack opening falls from 0,921 to 0,636. The time to reinforcement depassivation at a 25 mm cover grows from 33,0 to 63,9 years. Replacing 20% of the binder with fly ash, at a comparable strength gain, shortens this period to 31,5 years: the decrease in chloride diffusivity is accompanied by accelerated carbonation of the cover layer. The gain in service life is governed by the coincidence or divergence of the degradation mechanisms addressed by the two techniques and therefore does not reduce to the sum of their separately measured effects.