Hardened cement paste (HCP) formed from the hydration of mixtures of Portland cement, admixtures and additions has strength and other properties that could make it suitable for use as a construction material in its own right. However, it suffers from two main drawbacks – high dimensional changes, in particular low modulus, high creep and shrinkage, […]
Civil engineers are responsible for the production, transport, placing, compacting and curing of fresh concrete. Without adequate attention to all of these the potential hardened properties of the concrete, such as strength and durability, will not be achieved in the finished structural element. It is important to recognise that it is not sufficient simply to
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,
This article is concerned with how masonry is built, the architectural forms used and the resulting appearance. The basic structural form of many types of masonry is expressed on the surface of buildings and other structures and can be a very attractive and reassuring aspect of these. Appearance is a synthesis of the size, shape