Concrete Quality & Strength Testing

Quality of sound concrete is generally assessed from its penetrability. Generally it is water penetrability that is of concern either due to leakage or carrying of contaminates. However diffusion and dispersion are also important mechanisms. Penetrability can be by “permeability” or “sorptivity”. Permeability is a measure of the flow of gas or liquid under a pressure head and can provide a useful rate function to predict how quickly water will penetrate concrete under ground or sea water pressure. The flow of air is often measured and then water flow interpreted from that.

Sorptivity is a measure of how quickly concrete will draw water in by capillary action with no pressure head. This is a sensitive measurement method. Sorptivity can sometimes be estimated from absorption or volume of permeable voids but other parameters may negate this. PCTE recommend direct measures of Sorptivity or ISAT’s Concrete compressive strength is useful for many reasons. Whether for structural analysis, early age stripping, matching with repair mortars or indirect assessment of other parameters the surveyor needs to balance the advantages of NDT’s and cores. Cores are not necessarily more accurate than NDT’s as a combination of NDT’s can give a much better spread of results for the same cost. NDT’s are certainly less intrusive and very often can provide sufficiently accurate results without calibration.

Abrasion resistance of the top surface is particularly important in slabs. Poor concrete practices can lead to the surface having a strength 30% less than the bulk. The BCA (Chaplin type) tester provides a quick measure of abrasion resistance of the surface and there are established correlations between the abrasion number and performance.

Schmidt Hammers

The Schmidt Hammer (also known as concrete test hammer or rebound hammer) is used to find the compressive strength of concrete using the Rebound technique. This technique correllates the rebound or surface hardness of the concrete with the concrete strength. Using a the various Schmidt Hammers the total measuring range of compressive strength is 2 to 100 MPa. Available in many models the N Type Schmidt Hammer is for general testing, whereas the L Type Schmidt Hammer is for thinner elements (less than 100mm). The models of Schmidt Hammers include the Original Schmidt, Silver Schmidt and the Digi-Schmidt.

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DYNA Pull-Off Tester

The DYNA Z is a pull off tester for measuring concrete or shotcrete tensile strength, the bond of overlays, renders or repairs and coating adhesion. Simply bond the "dolly" to the test surface, locate the dolly tip in the DYNA Z and rotate the handle to pull the dolly off.

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Pundit Ultrasonic Tester

The pulse velocity in a material depends on its density and its elastic properties, which in turn are related to the quality and the strength of the material. It is therefore possible to obtain information about concrete uniformity, cracks, defects and strength.

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Resonance Modulus Tester

The Resonant Tester (RT-1) is a simple, rugged, battery powered unit designed for easy, fast, and reliable operation to find;  Young’s modulus, shear modulus and Poisson’s ratio of concrete, rock, masonry, carbon and other cylindrical (inc. cores), or beam specimens, as well as the dynamic properties for freeze-thaw durability. Consisting of three simple components, this digitally based handheld RT-1 tester is faster, simpler, easier and more economical than older analog vibrator technology.

Surfer Ultrasonic Pulse Velocity Tester

The Surfer Ultrasonic Tester is suitable for the measuring of time and velocity of ultrasonic p-waves in hard materials including concrete, rocks and ceramics. The Surfer has major advantages of other products on the market in that it doesn’t require coupling gel and takes seconds to perform the test.  This improves work flow, especially where a large volume of testing is to be carried out.

The Chaplin (BCA) Abrasion Tester

The abrasion tester gives a guide to the abrasion resistance of concrete floors. It can also be used to test the effectiveness of surface treatments used to protect or up-grade sub-standard floors. The depth of wear in the concrete floor brought about by the action of 75mm diameter by 20mm wide hardened steel wheels is used as a guide to the abrasion resistance.

TORRENT Gas Permeability Tester

The particular features of the TORRENT method are a two-chamber vacuum cell and a pressure regulator, which ensure that an air flow at right angles to the surface is directed towards the inner chamber. This permits the calculation of the permeability coefficient kT.

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