Durability of concrete and cement composites

Degradation of polymer-cement composites Introduction

Cementitious systems incorporating polymers have received considerable inter- national attention, especially over the last 30 years or so. This interest is reflected in ten international congresses, numerous symposia, workshops and journal publications that are the source of a considerable amount of information, see for example, compilations of the literature (CIRIA, 2000; Ohama, 1997). The reason for this interest can be attributed to the improved engineering properties when compared to the unmodified materials, e.g. tensile/flexural strength, toughness and durability, the latter including resistance to carbonation, chloride penetration, and frost damage. Additionally, these systems may be used as repair materials where a good bond with the existing concrete or steel is required. Many polymer- concrete combinations are available and there are various ways in which to classify them. They will be considered here under the following headings although some systems would fit into more than one category.

· Polymer-modified cement mortar and concrete (PMC): polymer particles in the form of a latex or redispersible powder are added to a fresh cementitious mix which is then cured.
· Polymer concrete (PC): aggregate is mixed with a reactive resin, placed, and then cured.
· Polymer impregnated concrete (PIC): a reactive monomer deeply penetrates a hardened concrete and is then cured.
· Polymer coatings: may include surface impregnation, paint systems and overlays where the polymer-concrete interface is of particular importance.

Excluded from this chapter are: (a) minor additions of polymer (e.g., ad- mixtures) which are used solely to alter the rheological behaviour of the mix; (b) polymer fibre, grids and bars for reinforced concrete; (c) polymer incorporated as aggregate.
Unknowns in product formulations, their application methods, variable environmental conditions, a lack of long-term monitoring of property changes  and a reluctance to disclose failures, result in the use of case histories being of limited value. Additionally, in view of the large amount of literature available, an overview of the topic is considered appropriate here and this draws heavily on the work of the author and his research students.

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