CONCRETE IN HOT ENVIRONMENTS - CHAPTER 9

Durability of Concrete - Khả năng của bê tông để chịu được các tác hại của các yếu tố môi trường, và để thực hiện thỏa đáng trong điều kiện dịch vụ, được gọi là "độ bền". Rõ ràng là độ bền của bê tông là quan trọng hàng đầu trong tất cả các ứng dụng kỹ thuật, và kết quả làm việc của bê tông phải được bảo đảm trong suốt cuộc đời dịch vụ dự kiến của nó. | Chapter 9 Durability of Concrete . INTRODUCTION The ability of concrete to withstand the damaging effects of environmental factors and to perform satisfactorily under service conditions is referred to as durability . Clearly the durability of concrete is of prime importance in all engineering applications and the satisfactory performance of the concrete must be ensured throughout its expected service life. Giving the concrete the required durability in aggressive environments is by no means easily achieved and requires careful attention to details during all stages of its mix design and production. This is particularly the case under hot-weather conditions where environmental factors may further aggravate the problem and make it more difficult for the concrete to attain the required quality. Chemical corrosion of concrete and that of the reinforcing steel as well are conditional on the presence of water moisture and their intensity is very much dependent on concrete permeability. Dense and impermeable concrete reduces considerably the ingress of aggressive agents into the concrete and thereby limits their corrosive attack to the surface only. The same applies to the penetration of air . oxygen and carbon dioxide and chloride ions both which play an important role in the corrosion of the reinforcing steel. Porous concrete on the other hand allows the aggressive water to penetrate and the attack proceeds simultaneously throughout the whole mass. Hence such an attack is much more severe. Similarly a porous concrete allows air and chloride ions to reach the level of the reinforcement and thereby promotes corrosion in the steel bars. Hence durability-wise and regardless of the Copyright 1993 E FN Spon specific conditions involved dense and impermeable concrete is always required when the latter is intended for use in aggressive environments. In view of its general relevance the discussion of permeability precedes that of the corrosion of the concrete and the .

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