HIGH STRENGTH CONCRETE BLOCKS STRUCTURAL MASONRY COMPRESSION STRENGHT

Abstract

Although the use of high strength concrete blocks for the construction of tall buildings is becoming current in Brazil, characteristics and some behavior aspects are not fully understood. The literature shows a gap in experimental studies with the use of higt strength concrete blocks above 16 MPa. The work presented here was carried out in order to study the behavior of higt strength structural masonry. Therefore, compressive strength and modulus of elasticity of concrete block walls tested under axial load, divided into hollow, grouted, with a grouted bond beam at the wall half height and and partial and full-bed mortar joint that was struck flush, built and tested in the laboratory of CESP and the Structures laboratory.of the UNESP Civil Engineering department of Ilha Solteira (NEPAE) were studied. Concrete blocks were used with nominal compressive strength of 16 (B1), 24 (B2) and 30 (B3) MPa. Hollow masonry wall were built with a height of 220 cm and a width of 120 cm, while grouted masonry walls were built with a height of 220 cm and width of 80 cm using traditional mortar with cement, sand and lime. 36 blocks, 18 prisms, 9 hollow masonry walls (6 with mortar only on the side of the blocks and 6 with mortar on all the face of these), 9 grouted masonry walls, and 12 hollow masonry wall with a grouted bond beam at wall half height, were tested. The analysis of the experimental results made possible to check the relationship between masonry unit’s compressive strength, prisms and masonry walls. The cracking pattern, the masonry mode of rupture at ultimate load and the shape of the graph Stress-strain deformation, were also analyzed. From the tests results it was found that prism/unit ratio strength varies according to the block strength; Executive procedure with face shell-bed mortar joint is suitable for high strength concrete blocks, and 20% decrease in resistance as compared with full-bed mortar joint being conservative; Using a grouted bond beam at half height of the walls has not led to compressive strength decreased, but it changed the rupture mode and the shape of the stress-strain curve; an estimated of E = 800 fp was shown to be conservative considering hollow masonry walls, and reasonably accurate considering grouted masonry walls and no need to limit the maximum value of E to 16 GPa; And finally wall/prism strength ratio equal to 0.7 may be used for high strength concrete blocks.