Impact resistance of polypropylene fibre-reinforced concrete was investigated using the repeated drop weight impact test recommended by ACI Committee 544. The results were analysed based on a statistical approach. The variation in results was examined within the same batch and between different batches. Statistical parameters were compared with reported variations in impact resistance of concrete composites reinforced with other types of fibres such as carbon and steel fibres. Statistical analysis indicated that the results obtained from this test had large variations and it is necessary to increase the number of replications to at least 40 specimens per concrete mix to assure an error below 10%. It is concluded that this test with its current procedures and recommendations should not be considered a reliable impact test. This study has highlighted the need for modifying this test in such a way as that increases its accuracy and reduces the large variation in results.

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Reviews the problems created by the presence of moisture in buildings, including thermal performance, humidity, structural performance, and visual appearance. Examines the fundamental concepts of moisture ingress and transfer, and the factors that control them. Concludes that it is now possible to compare absorption of various materials with a simple test, and that faster computer processing is now capable of modelling building behaviour under various environmental and material factors.

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