This summer, several of our team members took a field trip to Viola Engineering to learn more about what they do. Check out Brian Nixon’s recap below!
Viola Engineering is a geotechnical firm in Harrisonburg, VA. They are contracted by builders to take samples of concrete as it is being poured in order to determine whether not the compressive strength of the concrete is adequate for the application for which it is being poured. Viola collects these samples in cylindrical sample tubes, brings them back to their office, cures them, and then subjects them to a compression test. The shop manager, John Gray, walked us through the curing and testing process.
Once the samples collected in the field have hardened, they’re removed from the sample tubes and are placed in a special curing room. In this room they control the temperature and the humidity to ensure that the sample cylinders are adequately cured. After a minimum of 28 days, the cylinders are removed and subjected to a compression test using a hydraulic press. Before placing the sample in the press, the diameter of the cylinder is recorded and neoprene caps are applied to the top and bottom of the cylinder. The sample is loaded into the press and the press is lowered onto the sample. Once a secure contact is made with the sample, the press is zeroed out, which means the force applied to the cylinder at the point of initial contact is negated, and a constant force is then applied to the cylinder at a rate of about 30 psi/second until the point of failure.
The samples that we observed and tested held about 100,000 – 150,000 pounds before breaking. Once the sample breaks, the force at which the cylinder broke is recorded, the press is retracted, and the sample is removed. A visual observation of the sample is taken and the pattern by which the sample broke is compared to a chart (see included image below). Using the sample diameter and the breaking force, the compressive strength of the sample can be calculated.
For more in-depth information about this process, go here.