In the design and construction of modern structures such as high-rise buildings and long-span bridges, it is extremely important that realistic creep behaviour of concrete is known and used. In the 2003-2004 revision of the Australian Standard for concrete structures AS 3600, a new set of ‘basic creep factors’ or ‘basic creep coefficients’ are given to cover a wide range of concrete with characteristic strengths up to 100 MPa. This paper presents the background work undertaken to determine the basic creep factors. As part of this research, the suitability of various methods of extrapolating long-term creep from short-term creep tests were evaluated. The creep characteristics of a range of concretes were measured under sustained load in accordance with AS 1012.16. The concrete mixtures cover a range of constituent materials including a general purpose (GP) cement, an Australian version of an ordinary portland cement, binary and tertiary blends of GP with ground granulated blast furnace slag (slag), fly ash and silica fume. The coarse aggregates were either basalt from New South Wales and Victoria, or river gravel or air-cooled blast furnace slag from New South Wales. The mixtures cover a wide range of characteristic compressive strengths from 15 to 90 MPa. Of the three methods commonly used to extrapolate the long-term creep strain, the power model was found to be the most suitable method with good accuracy and a conservative overestimation of the creep strain. Two practical periods of measurement of short-term creep strain, 2-month and one-year, were examined from the 17 sets of medium-term (3-5 years) creep data. Based on the power model, the predicted ultimate creep strain from 2-month creep data tends to overestimate the basic creep factor by an average of 22% compared with measured values at the end of the 3-5 years of testing. Extending the measurement to one-year improves the accuracy with the average overestimation reduced to an average of 15%.

This study was aimed at evaluating an industrial production system of rice husk ash (RHA) with low carbon level. The system, developed in partnership with a local industry, consists of a continuously rotating furnace that can reduce the carbon level of residual RHA through re-burning. Different temperature bands, retention time in the furnace interior, and grinding degree were studied. The results indicate the feasibility of producing a material with reduced carbon levels, which is highly reactive and can be commercially used in the production of high performance concrete.

In recent years, extensive research on the influence of the saturation degree (SD) on the diffusion of chloride ions has demonstrated the importance of including this factor in models used to forecast the service life of reinforced concrete structures. The current study aims to propose changes to the test method devised by GUIMARAES (3) in order to allow analyses under unsteady-state flow conditions in the form of Fick’s Second Law and then assess the actual influence of the SD of concrete on the diffusion of chloride ions. The results obtained confirm that the SD is a major factor of influence on the diffusion of chloride ions. The curve proposed to account for the influence of the SD on the diffusion of chloride ions showed good accuracy when used as a model of service life applied to a reinforced concrete structure in a maritime pier with 22 years of use.

This article outlines an extensive number of laboratory tests on long-term deformations of Self Consolidating Concrete, SCC. For this purpose 4 SCC and 4 vibrated concrete, VC, were fabricated, in all 88 creep specimens. The water-cement ratio, w/c, of the concrete varied between 0.27 and 0.80 and strength between 14 and 171 MPa. Studies on shrinkage, strength and relative humidity, RH, were performed in parallel. The effect of late start of drying on creep was also incorporated in the studies. The results show creep and shrinkage of SCC of the same range of order as for VC at constant strength. No significant difference between the elastic modulus of SCC and that of VC was observed at constant strength. The creep coefficient , o, developed similarly in SCC as in VC .

In order to satisfy the needs of concrete durability, it is important to know the deterioration mechanisms to which the material could be submitted. Among the different mechanisms of concrete deterioration, biodeterioration is one of the most recently observed in structures. Its study is complex and demands a multidisciplinary research which involves different disciplines. This paper addresses biodeterioration concepts, the mechanisms involved, and the impact on concrete phases (cement paste and aggregate). An example of aesthetic and microstructural impacts on the mortar phase of a normal concrete when it is colonised by the Cladosporium sphaerospermum fungus is presented.