Browsing by Author "Schmidt, Jacob Michal"
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- ItemTensile and shear characterisation of the joint interface of alternative masonry(Stellenbosch : Stellenbosch University, 2020-04) Schmidt, Jacob Michal; De Villiers, Wibke; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: One of the biggest challenges that the South African government is confronted with is providing adequate housing for approximately 2.3 million households still living in informal settlements. Currently, the most popular building material for low income housing (LIH) in South Africa is cement-based masonry units. However, the cement manufacturing industry is considered to be one of the largest carbon dioxide releasing industries in the world. This shows that the usage of cement-based masonry, as construction material, is unsustainable and alternative masonry materials are required. Nonetheless, if alternative masonry units (AMUs) are to replace conventional masonry units (CMUs), these AMUs would need to be structurally viable, environmentally friendly and socially and economically acceptable. If AMUs should replace CMUs in the South African housing market, minimum mechanical specifications are required. The goal is to develop performance-based regulation for AMU construction. Common mechanical properties like strength and stiffness, of different AMUs are regularly studied. However, concepts like the tensile and shear characterisation of the masonry unit/mortar interface are not researched frequently. This study investigates whether certain standards and benchmark tests used on conventional masonry can be successfully applied to alternative masonry. It also aims to determine certain mechanical properties. The focus of this study is the tensile and shear characterisation of the masonry unit/mortar interface on three different types of AMUs with two different mortars. These AMUs include the geopolymer (GEO) unit, cement stabilised earth (CSE) unit and adobe (ADB) unit. Results from the AMUs are compared to conventional concrete (CON) units which act as the benchmark material in this study. The main mechanical properties investigated in this study include the following: • Tensile strength and tensile fracture energy of masonry units/mortar interfaces. • Initial shear strength, friction angle, shear fracture energy and initial dilatancy angle of masonry units/mortar interfaces. Results from the tensile tests show that the water absorption characteristics of the masonry unit have a larger influence on the bond strength than the surface roughness. The shear tests indicate that the linear relationship defined by the Mohr-Coulomb friction law, between the shear stress and the pre-compression stress, continues for a higher pre-compression load of 2N/mm2. The tensile and shear tests caused complications for determining the respective fracture energies in tension and shear. In contradiction to suggestions from literature, non-zero dilatancy values were obtained for shear tests at a pre-compression load of 2N/mm2 for CON and GEO masonry. The tests were conducted successfully in most cases and this confirmed the test setups as satisfactory, bar certain aspects, which are recommended for future studies. The findings of this study can be used to add reliable data to literature, of the mechanical properties of the masonry unit/mortar interface of alternative masonry. This can complement other studies in developing a finite element model to simulate and analyse structures with different geometries constructed of AMUs on a perfomance basis. Additionally it can contribute towards the regulation of construction with AMUs in South Africa.