Field testing the strength of thin-layer mortars using the pull-out method

Reinforced steel bar (rebar) mesh and thin-layer mortar are applied to reinforce sintered clay brick walls in a construction site. Their strengths are measured using the pre-installed pull-out method, the post-installed pull-out method and the standard cube compression strength test. Nine strength grades of cement mortars, namely, M10, M15, M20, M25, M30, M35, M40, M45 and M50, are chosen for the test; the pre-installed and post-installed pull-out tests consist of 54 samples of each. By fitting the experimental results, a formula for the compressive strength of the thin-layer mortar for the pre-installed and post-installed pull-out tests is developed. The regression function is validated and an interval prediction of the specific compressive strength for the pre-installed pull-out test is proposed. This study provides a basis for wider application of the pull-out test for thin-layer mortar and the establishment of its technical standards.