Strength of brick masonry column encased with precast ferrocement jackets

Abstract

Brick masonry structures are the most common type of structures built in Bangladesh. Significant increase in load carrying capacity of brick masonry columns is possible through encasement by ferrocement overlay. This study investigates the possibility of using precast ferrocement jackets for brick masonry columns. A total of thirty-two brick masonry columns and two hollow ferrocement columns were constructed and tested in this investigation. The brick columns were divided into four sets. The first set of columns were completely bare, the second set of columns were with plaster, the third set of columns had precast ferrocement jackets divided into two equal halves, around the columns and the fourth set of columns had precast ferrocement jackets divided into three segments, around the columns. The brick columns in a set were made with mortar having different cement-sand ratio and water-cement ratio. The cement-sand ratio of mortar used for plastering and construction of precast ferrocement jacket was 1:2. The thickness of plaster and precast ferrocement jacket was 15mm. The columns were fabricated in the laboratory, cured for 21 days and tested at 28 days using Universal Testing Machine. All the columns were tested under increasing load until failure. From the test results it was observed that the cracking and failure stresses of columns with precast ferrocement jackets were substantially higher than those of the bare brick masonry columns and columns with plaster. It was also observed that the application of rich mortar plaster over bare brick masonry columns does not increase the cracking stress and failure stress significantly. The cracking and failure stresses of columns with precast ferrocement jackets divided into two halves were nominally higher than those of the columns with precast ferrocement jackets divided into three segments. The failure of bare brick masonry columns and column coated with plaster is sudden and crack width increases rapidly after their formation, leading to a brittle failure for the system. On the contrary the failure of column with precast ferrocement jackets occurred slowly, exhibiting much ductile response at failure.