What is a core test for concrete?

Question

Why?

Answer 1

Physical testing complements the data provided from chemical and microscopic testing, providing important information regarding the physical properties of the member under examination. Most commonly requested, of course, is strength, to enable the Engineer to assess the loading capabilities of a structural element. This is usually supplemented with data on the reinforcement configuration, type and size, from a covermeter survey and localised breakouts.
Core samples are the most common form of sample for this purpose, removed from the structure by diamond drilling. Typically cores will be 100mm in diameter, and should ideally be at least three times the maximum aggregate size in diameter.
The cores are usually visually described and photographed, concentrating especially on compaction, distribution of aggregate, presence of steel etc. and then trimmed to a length to diameter ratio approaching 1:1. Various methods are available to ensure accuracy of the ends of the core; grinding to a perpendicular flat surface, capping with high alumina cement mortar and capping with hot sulphur are all methods which are used.
The capped core is then crushed (after appropriate curing for HAC capped specimens) in a calibrated compression testing machine. The resulting failure load is converted firstly to a cylinder strength and secondly to an equivalent insitu cube strength. This will generally be some 75% or so of the original cube result, depending on where the core was taken, before allowing for any additional correction due to compaction effects.

Answer 2

A core may be removed from concrete with a core saw- usually a cylinder with diamond chunks on the end since diamond is much harder than concrete. Cylinders are usually between 2" to 6" in diameter. After cutting the sample is taken to the lab and placed it in a hydraulic press. They record how much force is being applied until the cylinder breaks or fails. The force divided by the area gives the strength of the conrete. In modern construction the specifications usually call for 3000 or 4000 psi concrete but other "mixes" are also used.

Answer 3

It tests the concrete for integrity, hardness, density, etc. Basically it makes sure your concrete contractor isn't pouring (scat) into those molds.

There is a big lawsuit in Indianapolis right now, where the concrete contractor used bogus stuff in a new parking garage, and the cracks started immediately.