Estimation of Portland cement mortar compressive strength using microcores. Influence of shape and size

•We estimate the compressive strength of mortar in situ compared to standard specimens.•We applied ANOVA statistical analysis on microcores of different shapes and size.•ANOVA establishes a clear difference between reference specimens and microcores.•Values determined by microcores 1 and 0.5 thick overestimate the compressive strength.

This work analyses the possibility of estimating the compressive strength of hardened cement mortars extracted from buildings compared to normalized specimens using conversion coefficients. Once we obtained microcores of different shapes and size manufactured from mortars of known dosage, the mechanical assays were performed for normalized specimens and microcores. A statistical treatment of the data was carried out using one-way ANOVA with the Tukey’s test for multiple comparisons.The results establish a clear difference between the strength for normalized specimens and microcores, indicating that values determined through microcores overestimate the compressive strength, so the conversion coefficients range from 0.53 to 0.86.