The most common concrete testing approaches in most typical construction applications are slump tests, cylinder tests, and beam breaks.
Slump tests measure how quickly a concrete mix ‘slumps’ over when removed quickly from a slump cylinder. This test tells the contractor and inspector on site how ‘stiff’ or ‘wet’ the mix is. The slump isn’t really an accurate indication of water-cement ratio however because of the many types of water reducers and plasticizer admixtures in use today. After adjustments for these admixtures, slump is simply an engineering testing concept which specifies what condition the concrete mix should be in before it’s placed as higher slump mixes can be indicate of too much water and vice versa.
A cylinder test or cylinder break happens when a testing agency breaks a 6” diameter specimen of hardened concrete in a controlled laboratory environment, for the purpose of obtaining its compressive strength in pounds per square inch (psi). Exterior air entrained concrete for example is often specified to reach a strength of 4000psi in 28 days. To assure a certain mix of concrete is on the right track in terms of curing, cylinders may be taken at 3, 7, 14, 21, or 28 day increments, or anywhere in between. Sometimes engineers require that only ACI (American Concrete Institute) Certified technicians prepare on site samples for cylinder breaks; otherwise the contractor can simply make the samples and drop them off to the testing laboratory.
Beam breaks are concrete beams cast on site that are taken to a controlled laboratory environment and broken for the purpose of determining the tensile and flexural strength of a batch of concrete. This test is useful for determining when newly placed concrete is ok to operate heavy equipment or vehicles on or around.