Civil Engineering Materials

Successful placing of concrete is not enough. It is necessary to ensure that it comes through the first few days of its life without mishap, so that it goes on to have the required mature properties. Immediately after placing, before the cement’s initial set the concrete is still in a plastic and at least semi-fluid […]

Deformation of concrete results both from environmental effects, such as moisture gain or loss and heat, and from applied stress, both short- and long-term. A general view of the nature of the behaviour is given in Fig. 1, which shows the strain arising from a uniaxial compressive stress applied to concrete in a drying environment.

Stress–strain Behaviour  of Concrete Elasticity of Hardened Cement Paste HCP has a near linear compressive stress–strain relationship for most of its range and therefore a modulus of elasticity can readily be determined from stress–strain data. Water-saturated pastes generally have a slightly higher modulus than dried pastes, indicating that some of the load is carried by

Creep Behaviour of Concrete The magnitude of the creep strains can be higher than the elastic strains on loading, and they therefore often have a highly significant influence on structural behaviour. Also, creep does not appear to tend to a limit, as shown in Fig. 1 for tests of more than 20 years duration. This

Strength is probably the most important single property of concrete, since the first consideration in structural design is that the structural elements must be capable of carrying the imposed loads. The maximum value of stress in a loading test is usually taken as the strength, even though under compressive loading the test piece is still

Strength Influencing Factors of Cement Concrete In this article we will consider the strength of concrete with Portland cement as the sole binder. The effect of additions will be discussed as well. Transition/Interface Zone  Before looking at the relationships between the strength of concrete and the many factors that influence it, we need to introduce

Cracking and Fracture in Concrete  Development  of Microcracking  The non-linear stress–strain behaviour of concrete in compression is largely due to the increasing contribution of microcracking to the strain with increasing load. Four stages of cracking behaviour have been identified (Glucklich, 1965): Stage 1, up to about 30% maximum stress. The pre-existing transition-zone cracks remain stable,

Admixtures are chemicals that are added to concrete during mixing and significantly change its fresh, early age or hardened state to economic or physical advantage. They are usually defined as being added at rates of less than 5% by weight of the cement, but the typical range for most types is only 0.3 – 1.5%.

Concrete units have been made since the 1920s and were widely used, in the form of the ‘breeze block’, to build partitions in houses in the building boom of the 1930s. In the past 40 years, however, the range of products has expanded enormously to cover facing bricks and blocks, high-strength units, simulated stone units,