Durability of Steel in Concrete Nearly all structural concrete contains steel, either in the form of reinforcement to compensate primarily for the low tensile and shear strength of the concrete, or as prestressing tendons that induce stresses in the concrete to oppose those due to the subsequent loading. Sound concrete Read more…
Degradation of Concrete The degradation agencies that affect concrete can be divided into two broad groups: those whose action is initially chemical, before subsequently leading to loss of physical integrity; these include sulphates, seawater, acids and alkali– silica reactions those which directly lead to physical effects, such as freeze–thaw and Read more…
Durability can be defined as the ability of a material to remain serviceable for at least the required lifetime of the structure of which it forms a part. Standards and specifications increasingly include requirements for a design life, which can typically be 50 or 100 years, but for many structures Read more…
There are a wide variety of methods and techniques available for the non-destructive testing of structural concrete, which can be broadly divided into those that assess the concrete itself, and those which are concerned with locating and determining the condition of the steel embedded in it. We are going to Read more…
Mix design is the process of selecting the proportions of cement, water, fine and coarse aggregates and, if they are to be used, additions and admixtures to produce an economical concrete mix with the required fresh and hardened properties. It is often, perhaps justifiably, referred to as ‘mix proportioning’ rather Read more…
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 Read more…
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 Read more…
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 Read more…
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 Read more…
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 Read more…