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Title: Fracture mechanics of concrete
Author: McCreath, Dougal Reid
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1968
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The work reported in this Thesis represents an attempt to analyze the fracture processes of concrete in a rational and quantitative manner. This investigation was concerned primarily with the first "stage' of fracture, termed "fracture initiation". Existing theories concerning the initiation of brittle fracture have had only limited success in the explanation of concrete fracture, primarily because its heterogeneous nature will produce a highly disturbed and complex system of local stresses or strains. To obtain information on the nature and magnitude of the local strains, an experimental program was undertaken which involved the testing of plate-models representing thin two-dimensional slices of concrete. For these tests, the complex structure of concrete was simplified and represented as a two-phase system of large coarse aggregate particles embedded in a homogeneous mortar matrix. The local and average strains in the models were measured using both photo-elastic coating methods and electrical resistance strain gauges. The strain information obtained for models representing various volume fractions of aggregate was analyzed using an experimentally derived "fracture initiation envelope". This envelope defined the combinations of principal strains for which fracture would initiate within the mortar. Predictions were made concerning the position of the point from which fracture was likely to initiate, and the strains necessary to cause such initiation. The fracture processes were observed experimentally using photo-elastic coatings, high speed photography and fluorescent dyeing techniques. Reasonable correlation was found between the predicted and the observed fracture events. Tests of the three-dimensional concrete prototype were undertaken, and the results found to be in acceptable qualitative agreement with the results predicted from the plate-model tests. It was considered that the plate-model tests probably represented a "lower bound" solution for the strains at which fracture would initiate. It was concluded that the analytical and experimental techniques used gave some rational insight to the fracture processes undergone by concrete.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available