A research-based approach to exploring the adoption of novel UK-based concrete test methods in Chinese construction sector

As part of a UK-China science bridge project - a UK government funded initiative linking leading universities and businesses in selective partnering countries in 2009 a collaborative research programme was initiated between Queen's University and the Research Institute of High Performance Concrete (part of the Central Research Institute of Building and Construction) in Beijing.

For further details email b.magee@ulster.ac.uk

A durability performance-index for concrete: developments in a novel test method

Implementation of both design for durability and performance-based standards and specifications are limited by the lack of rapid, simple, science based test methods for characterising the transport properties and deterioration resistance of concrete. This paper presents developments in the application of electrical property measurements as a testing methodology to evaluate the relative performance of a range of concrete mixes. The technique lends itself to in-situ monitoring thereby allowing measurements to be obtained on the as-placed concrete. Conductivity measurements are presented for concretes with and without supplementary cementitious materials (SCM’s) from demoulding up to 350 days. It is shown that electrical conductivity measurements display a continual decrease over the entire test period and attributed to pore structure refinement due to hydration and pozzolanic reaction. The term formation factor is introduced to rank concrete performance in terms of is resistance to chloride penetration.

238.2T-14 Concrete Thixotropy

Fresh concrete can exhibit different rheological behavior when at rest than when flowing. This difference is due to thixotropy, which can have important consequences for formwork pressure, multi-lift casting, slip-form paving, pumping, and segregation resistance. This TechNote defines thixotropy and distinguishes it from other changes in rheological properties; discusses the origins of, test methods for measuring, and factors affecting thixotropy; and concludes with its applications.

Test methods for concrete durability indicators

Durability of concrete structures is primarily dependent on the environmental influences, i.e. the penetration of aggressive substances in the structural element from the environment. Penetrability is an important durability indicator of concrete and by specifying different classes of penetrability of concrete it should be possible to design a structure with the required resistance to environmental loads. This chapter covers descriptions of the available and commonly applied in situ and laboratory, non-invasive and semi-invasive test methods for evaluating concrete penetrability properties.

Principles of the performance-based approach for concrete durability

In general, design approaches for durability can be divided into prescriptive design concepts and performance-based design concepts.

The Modern Ordinary: Changing culture of living in Egypt’s traditional quarters at the turn of the twentieth Century

Having experienced social and political structures of the 19th century Europe, Western- educated Egyptian elite used public institutions to force legislative structures and procedures that ruled out traditional housing forms and spatial systems. This essay detects direct and indirect impact of these changes that informed the spatial change of modern living in Egypt in the first quarter of the twentieth century. It offers analysis of socio-spatial practices and change in ordinary Cairenes’ modes of everyday living, using social routine and interaction to explain spatial systems and changing house forms during the first quarter of the 20th century. In doing so, the essay utilized archival documents, accounts, formal decrees, and novels of the time as well as conducting survey of house forms and spatial organizations in Old Cairo.

Concrete damage plasticity model for modeling FRP-to-concrete bond behavior

The technique of externally bonding fiber-reinforced polymer (FRP) composites has become very popular worldwide for retrofitting existing reinforced concrete (RC) structures. Debonding of FRP from the concrete substrate is a typical failure mode in such strengthened structures. The bond behavior between FRP and concrete thus plays a crucial role in these structures. The FRP-to-concrete bond behavior has been extensively investigated experimentally, commonly using a single or double shear test of the FRP-to-concrete bonded joint. Comparatively, much less research has been concerned with numerical simulation, chiefly due to difficulties in the accurate modeling of the complex behavior of concrete. This paper presents a simple but robust finite-element (FE) model for simulating the bond behavior in the entire debonding process for the single shear test. A concrete damage plasticity model is proposed to capture the concrete-to-FRP bond behavior. Numerical results are in close agreement with test data, validating the model. In addition to accuracy, the model has two further advantages: it only requires the basic material parameters (i.e., no arbitrary user-defined parameter such as the shear retention factor is required) and it can be directly implemented in the FE software ABAQUS.

Finite element modelling of FRP-to-concrete bond behaviour using the concrete damage plasticity theory combined with a plastic degradation model

The technique of externally bonding fibre reinforced polymer (FRP) composites has been becoming popular worldwide for retrofitting existing reinforced concrete (RC) structures. A major failure mode in such strengthened structures is the debonding of FRP from the concrete substrate. The bond behaviour between FRP and concrete thus plays a crucial role in these structures. The FRP-to-concrete bond behaviour has been extensively investigated experimentally, commonly using the pull-off test of FRP-to-concrete bonded joint. Comparatively, much less research has been concerned with the numerical simulation of this bond behaviour, chiefly due to difficulties in accurately modelling the complex behaviour of concrete. This paper proposes a robust finite element (FE) model for simulating the bond behaviour in the entire loading process in the pull-off test. A concrete damage plasticity model based on the plastic degradation theory is proposed to overcome the weakness of the elastic degradation theory which has been commonly adopted in previous studies. The model produces results in very close agreement with test data. © Tsinghua University Press, Beijing and Springer-Verlag Berlin Heidelberg 2011.