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 describe three well-established tests for […]
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 this is not well defined,
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 fire. We will now consider
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 provides an excellent protective medium
Constituents of Bituminous Materials Bituminous materials consist of a graded aggregate bound together with bitumen. In addition, the mixture contains a small proportion of air. Thus bituminous materials are three-phase materials and their properties depend upon the properties of the individual phases as well as the mixture proportions. The two solid phases are quite different
Types of Bitumen Penetration Grade Bitumens Refinery bitumens are produced with a range of viscosities and are known as penetration grade bitumens. The term derives from the test that is used to characterise them according to hardness. The range of penetration grades for road bitumens is from 15 to 450, although the most commonly used
Aggregates for Bituminous Materials Aggregates make up the bulk of bituminous materials; the percentage by weight ranges from about 92% for a surface course asphalt to about 96% for a dense, heavy-duty and high-modulus base asphalt concrete. The aggregate has important effects on the strength and stiffness of bituminous mixtures. In asphalt concrete mixtures, the
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