Title:
Sustained Load Strength and Short-Term Strain Behavior of High-Strength Concrete
Author(s):
Said Iravani and James G. MacGregor
Publication:
Materials Journal
Volume:
95
Issue:
5
Appears on pages(s):
636-647
Keywords:
strength; strain testing;
DOI:
10.14359/406
Date:
9/1/1998
Abstract:
A test program was carried out on 100 by 200 mm cylinders to study both the compressive strength under high sustained stresses and the short term strain behavior of high-strength concrete. The sustained load specimens were subjected to sustained stresses for three months, if they did not fail sooner. The concretes had 56-day strengths of 65 to 120 MPa (9425 to 17,400 psi). Sustained load stresses ranged from 70 to 95 percent of the short term strength. The effects of strain gradient and silica fume were also studied. In addition, stress-strain curves, volumetric strains, and Poisson’s ratio were measured in monotonic short time tests.The ratio of the sustained load strength for specimens loaded for 90 days to the short term strength of ultra high-strength silica fume concrete was found to be 10 to 15 percent higher than that of normal strength concrete while the sustained load strength ratio for high-strength concrete was found to be similar to normal strength concrete. The sustained load strength ratio for high-strength concrete under small eccentric loads was found to be approximately 5 percent higher than that under concentric loads. There is correlation between the sustained load strength of high-strength concrete and the stress at which the short time stress - strain curves deviate from a straight line. The volumetric strain, Poisson’s ratio, and sustained load studies show that while the short time stress-strain characteristics of high-strength concrete are similar to those of rock, its long term behavior similar to normal strength concrete and is dominated with its composite nonhomogeneous structure, creep of the paste, and time dependent deformation.