Department of Civil Engineering

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Browsing Department of Civil Engineering by Subject "Adobe brick"

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    Characterisation and Evaluations of the Mechanical Properties of Alternative Masonry Units
    (Stellenbosch : Stellenbosch University, 2017-03) Fourie, Johannes; De Villiers, Wibke; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: One of the greatest challenges facing the South African government is the provision of adequate and affordable housing to the 1.1 million families still living in informal settlements. Currently, the most widely used method of constructing low income housing (LIH) in South Africa is through the use of cement based masonry units. However, it is well known that concrete and cement have a significant negative impact on the environment due to carbon dioxide emissions from the production of cement clinker, as well as the consumption of natural resources. In order to reduce the environmental impacts, alternative masonry units (AMUs) are required that are structurally viable, environmentally friendly and socially acceptable. To properly begin implementing AMUs in practice the evaluation and characterisation of their mechanical properties are necessary. While standardised tests for conventional masonry units are widely available, it is unclear whether these tests are suitable for use on AMUs due to the large differences in the material properties between certain AMUs and conventional masonry units. Few standards exist that have been designed with AMUs in mind. This study investigates whether the standards and guidelines available for conventional masonry units can be applied to AMUs. Three different AMUs are compared with a conventional concrete masonry unit (CMU) in a variety of tests to determine if the applicable standards are successful at classifying the mechanical properties of the AMUs. The AMUs that were chosen for this investigation are: alkali-activated concrete blocks (AACBs), compressed stabilised earth blocks (CSEBs) and adobe blocks. These materials were chosen so that the mechanical properties of each material varied notably from each other and from the CMU. The AMUs and the benchmark CMU were tested for a large variety of mechanical properties. Not only can the results from these tests be used to determine if the standards and guidelines are applicable to both conventional and alternative masonry units, but the data acquired from the investigation can be used in future numerical modelling. The standardised tests and mechanical properties investigated in this study include the following: • Compressive strength of the masonry units at 7, 14, 28, 56 and 91 days. Including both bedface and headface tests at 28 days. • Modulus of elasticity and Poisson’s ratio tests conducted on masonry cylinders. • Wedge splitting tests to determine the fracture energy of the materials. • Constant mass density tests. • Triplet tests to determine the shear behaviour at the interface of the masonry samples. Including both initial shear strength and internal angle of friction. • Compressive strength tests on small scale masonry wallets to determine both the compressive strength and modulus of elasticity. The outcomes of the study showed that the AACBs and CSEBs satisfy the minimum strength requirements for LIH in South Africa, while the adobe blocks were too weak. The weak adobe masonry units caused the most complications during the test procedures, nevertheless, the investigation found that with small adjustments to the standards, particularly the loading procedures, the tests could be successfully completed on the AMUs. Issues were however, encountered with the tests for Poisson’s ratio. The tests also provided a large variety of mechanical properties for both conventional and alternative masonry units which can be used in future studies for the numerical modelling of masonry for low income housing in South Africa. The knowledge gained in this study can therefore be used to begin laying the framework for the minimum technical specifications for AMUs in South Africa.