Durability of MgO/hydromagnesite mortars -- Resistance to chlorides and corrosion

TL;DR

This study evaluates MgO/hydromagnesite mortars' resistance to chloride penetration and corrosion, showing high chloride resistance and low corrosion rates of embedded steel, indicating potential for durable construction in chloride-prone environments.

Contribution

It provides new insights into the chloride resistance and corrosion behavior of MgO/hydromagnesite mortars, highlighting their suitability for protecting steel in specific conditions.

Findings

High chloride ingress resistance with low chloride migration coefficients.

Corrosion rates of steel are low and unaffected by mortar composition or curing.

Moisture condition is the primary factor influencing steel corrosion in these mortars.

Abstract

The durability of MgO/hydromagnesite mortars was studied with respect to their corrosion performance and resistance to chloride attack and moisture. MgO/hydromagnesite pastes were cured in chloride solution to induce potential formation of Mg-chlorides; however, no such phases were observed. Rapid chloride ingress measurements demonstrated high penetration resistance and low chloride migration coefficients, i.e. D_Cl = 1e-13 to 1e-12 m^2/s. The corrosion rate of carbon steel embedded in MgO/HY mortars, as determined by linear polarization resistance measurements, was in the range icorr = 1e-9 A/cm^2 in dry and 1e-7 A/cm^2 in wet conditions, irrespective of the mortar composition or curing condition.These findings corroborate the hypothesis that, in the absence of chlorides, the moisture condition is the primary predictor of corrosion rate of carbon steel in the MgO/hydromagnesite binder. These accelerated, short-term experiments suggest that the binder may be suited to protect embedded carbon steel from corrosion under specific exposure conditions of practical relevance.