The motivation behind this work is to evaluate the impact of nano-magnesium calcite (NMC) waste on
the performance of cement mortar (CM) and its resistivity to sulfate attack. The addition of urea and
urease enzyme to ground water resulted in the removal of Ca2+ and Mg2+ as NMC precipitate (byproduct
of treatment process). As a beneficial recycling method, NMC with different proportions were individually
blended with CM to enhance its performance in normal and sulfate-rich media. The results revealed
that the NMC has a positive impact on the early-ages compressive strength of CM. Where, the addition of
1 wt% of NMC led to a significant enhancement in the rates of strength development and total porosity
reduction at all ages of hydration. Comparing with reference mixture, a highest performance in sulfate
medium was obtained in case of all CMs containing NMC. Complementary, the CM incorporated with
1 wt% NMC showed the highest resistance to sulfate attack (up to 12-months) which associated with
lower compressive strength regression, total porosity increment, sulfate expansion and consequently
lower ettringite formation rate.