Strength of the flexural joint of mortar joints and solid fired clay brick prisms

Abstract

Masonry constructions built with mortar and solid fired clay bricks are subject to: high cement content, excessive water-cement ratio causing problems of mortar shrinkage during curing and differential movements between the brick and mortar caused by movements due to wind or seismic events. Earth movements generate some failures in simple masonry walls and confined masonry in solid brick joints, mainly with failure inclination angles varying from 45 degrees to 50 degrees. The objective of this research work was to estimate the flexural bond strength of the mortar joint and the solid fired clay brick and thus establish design parameters for non-structural masonry in the municipality of Ocanña, Colombia. From the fired clay brick manufacturers, 18 in total, simple random sampling was used to determine the sample size, 4 manufacturers were randomly selected. In addition, the characterization of the solid fired clay brick units was carried out with respect to their compressive strength, initial absorption rate and final absorption, as well as the mortar with respect to its compressive strength at 28 days, according to the Colombian standard for earthquake resistant constructions; for the determination of the flexural strength of the bonding mortar and solid brick units, a semiautomatic machine for flexural strength testing of masonry units, Pinzuar model PC-13, with a force measurement of 1000 N and an accuracy of 0.1 N, was designed. The flexural strength at the masonry joint was obtained for mortar type M with a value of 0.26 MPa, with a standard deviation of 0.01 MPa and a coefficient of variation of 4.72%. As for mortars type N and S, the average strength value was equal to 0.24 MPa for the two types of mortar, with standard deviation of 0.03 MPa and 0.01 MPa respectively, and coefficient of variation of 11.4% and 3.18% respectively. Given the importance of the variables, an interpretation of physical of the relationship between the properties was made: compressive strength of the solid fired clay brick and flexural strength at the masonry joint, since their average values were similar.