- Author
- Carino, N. J. | Guthrie, W. F. | Lagergren, E. S. | Mullings, G. M.
- Title
- Effects of Testing Variables on the Strength of High-Strength (90 MPa) Concrete Cylinders.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Sponsor
- Federal Highway Administration, Washington, DC
- Book or Conf
- American Concrete Institute. High Performance Concrete. ACI International Conference. Proceedings. ACI SP 149-34. November 15-18, 1994, Malhotra, V. M., Singapore, 589-632 p., 1994
- Keywords
- concretes | building technology | capping | high strength concrete | compressive strength | cylinders | cylinder size | experiments | standards | statistical analysis | stress rate | test equipment | high strength concretes
- Abstract
- A full factorial experiment design was used to investigate the effects of the following variables on cylinder strength: end preparation (sulfur capping versus grinding), cylinder size (100 versus 150 mm diameter), type of testing machine (1.33-MN capacity versus a 4.45-MN capacity), and nominal stress rate (0.14 versus 0.34MPa/s). Two levels of strength were used (45 and 90MPa), and three replicates were tested for each run. Specific gravities were measured to check on the consistency of cylinder fabrication. Statistical analyses indicated that all the factors had significant effects on the measured compressive strength. On average, the 100-mm cylinders resulted in 1.3% greater strength, the faster stress rate produced about 2.6% greater strength, the ground cylinders were 2.1% stronger, and the 1.33-MN testing machine resulted in about 2.3% greater strength. There were significant interactions among the factors, so that the effects were greater than the average values for particular factors settings. For example, the effect of end preparation depended on the strength level. For the 45-MPa concrete, there was no difference due to the method of end preparation, but for the 90-MPa concrete, grinding resulted in as much as 6% greater strength in certain cases. Analysis of dispersion indicated that the 100-mm cylinders had higher within-test variability, but the differences were not statistically significant. Recommendations for modifications to testing standards are provided.