Category: Durability of concrete and cement composites

The purpose of this book is to bring together a series of reviews on topics of current relevance to the durability of concrete and cement-based composites. One might reasonably ask why such a book is now believed to be needed as concrete and related materials have been used with outstanding success in major construction projects for well over two thousand years. Indeed numerous ancient concrete structures, such as the Pantheon in Rome, and masonry structures with mortar joints, such as the Pont du Gard Aqueduct near NõÃmes in southern France (see Fig. 1.1), have survived to the present day in excellent states of preserva- tion. These and other examples of Roman construction works incorporating hydraulic cements made from lime and volcanic earth (or similar vitrified alumino-silicates, known collectively as pozzolanas, after Pozzuoli near Naples where a natural source of such material exists) have shown remarkable dur- ability even where they have been exposed to damp, aggressive environments. An impressive illustration was provided by Davey (1974) whose photograph of part of a Roman breakwater that had been exposed to the sea near Naples for two millennia (reproduced in Fig. 1.2), demonstrates that the mortar joints had endured far more successfully than the now heavily eroded stone blocks which they had been connecting.

Category: Durability of concrete and cement composites Fracture mechanics

Linear elastic fracture mechanics is concerned with predicting conditions that give rise to rapid crack propagation in brittle materials that are considered to be elastic, homogeneous and isotropic at the onset of fracture; it involves the study of stress and displacement at the microscopic level in the region of a crack tip (Mindess and Young, 1981). The field developed from

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Category: Durability of concrete and cement composites Degradation of polymer-cement composites Future trends

Interest in polymer-cement composites has increased considerably in recent years with systems finding widespread use in the concrete repair and main- tenance sector and speciality applications such as bridge deck overlays. In these cases, improved properties such as flexural strength, bond to existing material and durability are paramount. Some sectors which currently have a small market should grow and these

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Category: Durability of concrete and cement composites Characteristics of paints and polymeric surface treatments for concrete

A wide range of products and systems are available and may be classified as pore liners, pore blockers and coatings according to their function, the materials used and method of application. Whilst these systems are generally regarded as beneficial, lack of characterisation of the materials application procedures used makes quantitative comparison between the different products difficult. Similarly, there is little

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Category: Durability of concrete and cement composites Degradation of polymer-cement composites Interfacial characteristics

Although a large amount of data have been obtained for a range of polymer- cement composite properties, relatively little is known, apart from that discussed  in Section 10.2.4, about the nature of polymer-cement interfaces and interactions that may take place between the two components. In the field of composites generally, it is widely accepted that interfaces between different components are important

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Category: Durability of concrete and cement composites Polymer impregnated concrete

A polymer impregnated concrete is produced via a process whereby an existing hardened concrete (structure or factory component) is dried at around 150ëC and then impregnated with a low viscosity monomer, usually methyl methacrylate, which is subsequently cured in situ. Impregnation is often achieved by soaking at atmospheric pressure although the process may be facilitated by evacuation and/or higher pressures.

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Category: Durability of concrete and cement composites Reactive polymer matrix Thermal properties

In general the coefficients of thermal expansion for unfilled (lower modulus) and filled (higher modulus) products are ~40-100 and 20-40  10^-6 C^-1 respec- tively. This compares with ~10 x 10^-6 C’^-1 for typical substrate materials and can lead to the development of significant thermal stresses. Thus for high modulus systems which undergo little stress relaxation, temperature changes ~30ëC can lead to stresses which, over

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Category: Durability of concrete and cement composites Reactive polymer matrix composites Creep

These materials are visco-elastic in nature and thus, over time, may undergo creep and stress relaxation even at ambient temperatures. For many applications, service stresses are low compared to ultimate values and the effects are limited. However, for applications involving adhesive bonding and other load bearing applications, the consequences may have to be considered. Thus, it may be necessary to

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Category: Durability of concrete and cement composites Reactive polymer matrix composites Water absorption

Reactive polymer matrix composite materials generally have a high resistance to water transmission, although the extent depends very much on their formulation. Over the long-term, slow diffusion may lead to reversible equilibrium moisture contents of up to 10%. Eventually this can lead to the creation of pathways for ingress of deleterious species such as chloride ions, reduction in modulus and

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Category: Durability of concrete and cement composites Reactive polymer matrix composites Application

Since there is a very wide range of systems available, it is very important that the right one is chosen for the specific application in mind. Assuming that the correct choice is made, it is then very important that the correct procedures are used on site and in the case of pre-cast factory products. Correct proportioning and thorough mixing of

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Category: Durability of concrete and cement composites Reactive polymer matrix composites Introduction

These materials are quite different from polymer-modified mortars in that they do not contain any hydraulic cement. They consist of a synthetic resin binder incorporating a hardener and filler such as well-graded powder, sand or coarse aggregate. These are mixed on site, placed and then allowed to cure giving a material with generally good mechanical properties (in terms of compressive,

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