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

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.

Isolation, Identification and Antimicrobial Susceptibility Tests of E. Coli and Salmonella from Diarrheic Calves in and Around Sebeta Town

Background Calves are important assets for replacement of cows for the future dairy and beef herd sustainability. However, calf hood diseases have a significant financial impact on dairies resulting from treatment costs, genetic loss, and impaired future performance. Objective The purpose of the present research is for isolation and identification of Salmonella and E. coli infection in diarrheic calves, assessing risk factors for occurrence of calf diarrhea and examining antimicrobial susceptibility of isolated bacteria’s. Methodology: A cross- sectional study on the isolation, identification and antimicrobial susceptibility of E. coli and Salmonella was carried out on calves up to two months of age from November, 2018 to March, 2019 in and around Sebeta town, Ethiopia. The detection of E. coli and Salmonella was done by conventional bacteriological method and biolog (semiautomatic machine). The data was analyzed by Stata 12. Results It was found that the detection rate of E. coli and Salmonella from 129 sampled diarrheic calves were 65 (50.3%) and 8 (6.2%) respectively. Age (E. coli, X2 = 9.429, P = 0.024; Salmonella, X2 = 8.161, P = 0.043), sex (E. coli, X2 = 11.225, P = 0.001, though not significant for Salmonella) and feeding time of colostrum (X2 = 7.510, P = 0.023; Salmonella, X2 = 6.678, P = 0.036) were risk factors associated with the incidence of E. coli and Salmonella. The antimicrobial study revealed that most of the E. coli was highly susceptible to sulphamethoxazole˖trimethoprim, chloramphenicol, gentamicin and ampicillin and highly resistant to tetracycline (29.23%) and followed by polymixin B (6.1%), and from isolates of Salmonella all showed 100% susceptibility for sulphamethoxazole˖trimethoprim and polymixin B, 87% to Ampicillin, chloramphenicol and tetracycline while 75% to gentamicin. Conclusion Based on those findings, it can be concluded that calf diarrhea was found to be high and could affect dairy production in the study area. The triggering ecological, social and bacterial genetic factors for the widespread distribution of multidrug resistant Salmonella and E.coli are not known, thus requires comprehensive study.