SHRINKAGE MECHANISMS, CRACK FORMATION, AND SERVICE LIFE OF REINFORCED CONCRETE STRUCTURES
Shrinkage of concrete and other cement-based materials often is at the origin ofcrack formation. There is a characteristic difference between cracks induced by dryingshrinkage and those induced by autogenous shrinkage. But in any case cracks are preferentialpaths for ingress of aggressive substances such as chlorides or sulphates into the compositestructure of concrete. In this contribution a brief review on shrinkage mechanisms is presented.It is important to know the shrinkage mechanism in order to be able to minimize shrinkage.Reduced shrinkage means extended service life of reinforced concrete structures. It is shownthat the concept of capillary under-pressure,as formally predicted by a combination ofLaplace and Kelvin equation,is not a valid explanation of shrinkage of concrete. Shrinkagedepends essentially on the disjoining pressure of the pore solution in the nano pores. Thedifferent components of disjoining pressure are briefly introduced and discussed. Disjoiningpressure and hence shrinkage can he influenced by changing the calcium or the alkaliconcentration in the pore solution. This finding also explains the origin of carbonationshrinkage. The complex physical and chemical interactions are summarized in a simplifyingmodel. This model is useful to explain in a phenomenological way the influence ofcomposition of pore solution on shrinkage. Optimized composition of the pore solution willcontribute to more durable and sustainable constructions.
shrinkage nano-structure disjoining pressure crack formation service life
Folker H. Wittmann Francoise Beltzung Tie-jun Zhao
Aedificat Institute Freiburg,Freiburg,Germany;Qingdao Technological University,Qingdao,PR China University of Applied Sciences Northwestern Switzerland,Muttenz,Switzerland Qingdao Technological University,Qingdao,PR China
国际会议
The International Conference on Durability of Concrete Structures(2008年混凝土结构耐久性国际学术会议)
杭州
英文
52-63
2008-11-01（万方平台首次上网日期，不代表论文的发表时间）