Poor durability of high performance concrete with water-cement ratio <= 0.30?

Title: Poor durability of high performance concrete with water-cement ratio <= 0.30?
Author(s): B. Hillemeier, M. Schroder
Paper category : conference
Book title: International RILEM Workshop on Durability of High Performance Concrete
Editor(s): H. Sommer
Print-ISBN: 2-912143-03-9
e-ISBN: 2351580125
Publisher: RILEM Publications SARL
Publication year: 1994
Pages: 70 - 75
Total Pages: 6
Nb references: 2
Language: English

Abstract: Are we facing a problem combined with the durability of concrete with very low water-cement ratio? The question addressed to the theory of Powers /1,2/ could be relevant for water-cement ratios below w/c = 0.30. The phenomenon refers to an additional hydration of cement in a dense hardened cement paste without capillary pores. The late hydration products do not get the pore volume necessary to expand into. As a consequence microcracking by expanding hydration products could occur. To prove the theory that describes this particular kind of damage, tests have been carried out. Concrete cubes of two HPC-mixtures with w/c = 0.30 and w/c = 0.25 have been stored under curing conditions in compliance with the German standard DIN 1048 for minimum 56 days. Two opposite cube surfaces have been ground for the compressive strength testing. To accelerate the additional hydration of this normally hardened concrete the test cubes have been stored in hot water (90 OC). After 7 days of treatment the following results have been determined for both HPC-mixtures: a fine uniformly distributed crack structure was visible on the ground cube surfaces. In the case that the microcracking is a process of destruction it will be controlled by a very slow crack propagation speed. The compressive strength should be affected by the mentioned type of microcracking. In spite of the short period of initial testing a decrease in strength seems to be significant. The phenomenon can not be realized in a dry environment.

Online publication: 1996-02-02
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/2351580125.008