Lightweight concrete could be producing by incorporating expanded polystyrene in the conventional concrete. This paper discusses the results of an experimental investigation into the effects of binder materials on the engineering properties of polystyrene aggregate concrete (PAC), having the nominal density of 1800 kg/m3. Four types of binders, namely, general purpose cement, shrinkage limited cement, a combination of 60% general purpose cement and 40% low calcium fly ash, and blended cement with 62% granulated blast-furnace slag, were used. The results showed that as expected, the use of supplementary cementitious materials such as fly ash and slag reduced the early-age strength of the polystyrene aggregate concrete. The strength development of PAC was also affected by the curing condition. Although the use of shrinkage limited cement reduced the shrinkage of PAC by 12%, it increased the creep potential by 76%. The paper also discusses the relationships between: shrinkage and moisture loss; strength and rebound number; and strength and pulse velocity.

The evaluation of the condition of concrete structures suffering reinforcement corrosion lacks proper methods in standards or codes. At present, it is made by using non systematic methodologies and not considering the proportion of concrete or steel section that are damaged. In this paper, a methodology is described that considers the real state of the structure and the loss in steel cross section as well as the loss on steel/concrete bond or the concrete cracked section. The methodology considers two levels of detail. The first, a Simplified Method, is based on the use of corrosion indicators and is applied to make a preliminary assessment of the structural condition or to classify different ratios of damage in a semi-quantitative manner. The second, a Detailed Method, is based on the calculation of the ultimate states considering the reduced section. In both methods three steps are considered in the assessment: inspection, diagnosis or evaluation of present state, and prediction of future evolution. In the inspection phase, the minimum amount of testing needed for a correct characterization is described. In the second step, the simplified method uses “indicators” to classify the damage level, while the detailed method evaluates how corrosion has affected the concrete-steel bond, how much steel cross section has been lost, and the extent cover cracking. Finally, a prediction is made through the determination of the corrosion rate to give guidance on the urgency of intervention. The detailed method verifies the behaviour from the application of the limit-states theory. The whole process is presented in the form of a manual for engineers.

Calcium chloride is an excellent accelerator for concrete, improving both setting time and hardening rate. However, it can not be used for reinforced concrete in efficient dosages because of initiation of rebar corrosion. In the search for other bulk chemicals working as accelerators, calcium nitrate has proven to be a good candidate as set accelerator; however it is not a hardening accelerator (e.g. improving 1 day strength). Efforts have been made to combine calcium nitrate with other admixtures in order to make the mix work as a combined chloride-free setting and hardening accelerator. This paper sums up research over the last 10 years regarding this matter and also compares performance with other chemicals.

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.

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%.