n Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Strength, variability and failure mechanisms of rubble masonry concrete under compression : technical paper

Volume 41, Issue 2
  • ISSN : 1021-2019



Criteria that govern the failure mechanisms, variability and strength of rubble masonry concrete (RMC) are explored with reference to the behaviour of analogous particulate composites. Contiguous particle interaction and the potential for anisotropy are noted as two distinguishing characteristics that may account for much of this material's unique behaviour. Failure appeared to be initiated by debonding of the stone-mortar interface parallel to the principal stress long before the specimens attained their maximum stress. Variability of mechanical properties was found to be a function of anisotropy and heterogeneity. Although the interfacial surface area (between phases) in RMC is at leas 10 times smaller than in conventional 19mm stone concrete, it is demonstrated that this is not accompanied by a corresponding increase in the interfacial bond stress. However, it is argued that RMC strength is probably more adversely affected by phenomena that inhibit good interfacial bond than is conventional concrete. Finally, it is concluded that much of the RMC currently placed is probably weaker than its mortar matrix but that an appropriate material specification and good site practice will go a long way towards ensuring that the compressive strength of RMC exceeds that of its mortar matrix.

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