Some new and updated testing devices measure fresh concrete properties quickly enough to let quality-control personnel rapidly detect changes in the concrete.
By using a nuclear Water/Cement Gauge, technicians can quickly measure water and cement content on-site, thus reducing the risk of out-of-spec concrete being placed in a structure. The device contains one probe that measures water content and another that measures cement content. The water probe emits neutrons that slow significantly when they collide with hydrogen atoms, found predominantly in concrete mixing water. A detector inside the probe counts slow neutrons. The cement probe emits low-energy photons that collide with various atoms found in concrete. After a collision, the photon is either absorbed by the atom or bounced off it (scattered). A detector in the probe indicates cement content by measuring the number of photons that scatter back from the concrete elements. After the readings, the control unit automatically calculates and displays the water-cement ratio and cement and water contents in either U.S. customary or metric units.
ALKALI AND CHLORIDE CONTENT
How can the concrete producer or user be assured that fresh concrete has the desired low amounts of alkali (sodium and potassium oxides)? A rapid alkali test answers this question in about 30 minutes. The rapid alkali test kit weighs about 8 pounds, and contains electrodes, electrometer, calibration liquids, and other equipment needed to determine alkali content of fresh concrete on-site.
The Flowmeter is an electronic version of the K-Slump tester, giving flow values that correlate with standard slump-test results. A temperature sensor also permits the operator to measure concrete temperature electronically.