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TESTING TECHNOLOGY

The relevant international Standards forElastic Modulus (EM) test on concrete areessentially the ISO 6784 of 1982, the BS1881:121 of 1983, the ASTM C469 of1994, the DIN 1048:1 of 1978, the NordTest Build 205 of 1984 and the UNI 6556of 1976. Actually there is not a ENStandard but a dedicated technical commit-tee is working on one. For the mortar sectorthe recent EN 13412 of 2007 is wellknown and used.

Basically all the above Standards are thesame with respect to the specimen dimen-sions giving the possibility to use cylindricalor cube specimens. For the specimen defor-mation measurement the Standards requirethe use of two, three or four sensors to befixed on the sides of the cubes or cylinders.The Standards prefer the calculation of theEM after a specified number of cycles.

The cycle amplitude, to be performed bet-ween a minimum and a maximum stress, isdefined referring to the compressivestrength, estimated as the average valuetesting three other specimens having thesame mix. The cycles are a common pointof all the Standards: the reason seems evidentdue to the stabilization of the EM valueafter the second cycle, whilst it is very low ifcalculated on the first cycle. The aim of theStandards is therefore to obtain a stabiliza-tion of the specimen and therefore of theEM.

Increase precision and decrease testing time

Controls, the Italian based manufacturer oflaboratory testing equipment, has recentlyintroduced the new 55-C0222/F magneto-strictive linear position sensors for specimendeformation measurement as an excellentalternative to the traditional strain gauges.So much time and great attention has to bepaid during the gluing and welding of eachstrain gauge. A common inconvenience du -

r ing the test is the propagation of microcracksacross the strain gauges causing their failureand the loss of the measurements.

The 55-C0222/F sensors do not have thisproblem: the main user benefit is the simpleand quick set up as well as the high sensiti-vity and accuracy of this new technology.The fixing to the surface of the sample is viatwo elastic straps which apply a slight pres-sure and a pair of conical points made ofhardened steel which prevent any slippageThe aluminium and steel structure that hou-ses the displacement transducer providesfriction-free movement between the fixedand mobile parts in any test condition. Thestructure acts as a mechanical full scaledevice and stops the transducer being acti-vated beyond its full scale.The sensors are connected to the MCC8servo hydraulic console, and allow highlyaccurate measurements of axial deformationsboth on concrete specimens and mortarspecimens whilst saving time given its rapidand easy set up. In a few minutes two or

more, depending on the Standard, sensorscan be positioned and fixed to the sampleand be ready for the test.The sample deformation is the signal usedby the MCC8 servo-hydraulic console toacquire the deformations data to automa-tically calculate the EM value.The oil flow is accurately controlled by theservo valve reacting immediately to smallvariations which are corrected instanta-neously, so as to provide a linear distributionthroughout the test cycles without sharpfluctuations, which are typical problemsusing other solutions such as an integratedinverter electric motors. Servo valve systems allow the control ofboth the direction and quantity of the oilflow and thus, the load exerted on the spe-cimen, based on its stiffness.

Software package for quick and easytest reports

The manufacturer also offers E-Module, aWindows-based software package desi-

Automating concrete and mortar elastic modulus test reports

Controls S.R.L., 20063 Cernusco s/N. (MI), Italy

Whilst the severity of the recession in the construction sector seems never ending, new testing technologies can represent the key to thefuture. Ideally the elastic modulus is measured directly on concrete specimens under compression by recording the load-deformation curve.However, this is not always easy: the procedure up till now is quite complicated and time-consuming when compared to normal compressivestrength tests. Laboratory Managers may not like to admit it, but reporting on concrete testing is not nearly as fast as producing concrete.That’s why many laboratory managers will be interested in a new technology that increases testing precision and decreases report times.

Fig. 1: Concrete and mortar specimens fitted with high precision 55-C0222/F sensors for EMtest

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TESTING TECHNOLOGY

gned to help speed and organize the EMtesting of concrete and mortar specimens.The software allows the remote control fromPC of the command console and the auto-matic determination of EM. It’s easy todownload and upload the calibration set-tings for each of the eight channels availa-ble, four for pressure transducers or loadcells and four for strain or displacementtransducers, potentiometers or LVDTs.This software allows the laboratory techni-cian to assign specimen ID and job numbersand enter a variety of field data in presetfields, including supplier information, mixdesign, date and time, placement location,temperature, slump, air content, and otherfactors. Generating specimen schedulescan be a big help with specimen manage-ment. When it’s time to test the specimens,the software reduces overall test cycle timeby importing setting data from the MCC8servo-hydraulic console via the RS232 seri-al port. Both paper and electronic testreports, including stress-time and stress-strainplot (hysteresis cycles), which can be custo-mized to meet different customers’ needs,can be generated immediately.

The program can also be set to automatic -ally post electronic reports to a password-protected web portal where project person-nel, onsite or in the office, can view thedata using a Web browser. This featurealone can save days in the testing cycleand reduce postage or other delivery costs.It also eliminates data entry errors.

Employing testing systems that automaticallyperform the tests according to specifications,calculate results and seamlessly communi-cate with other computers and programsrunning on their corporate network, ensuresconsistency within and amongst laborato-r ies creating a distinctive product and lea-ding straight to success.

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Literature

[1] ISO 6784: 1982. Concrete. Determination of staticmodulus of elasticity in compression.

[2] BS 1881-121:1983. Testing concrete. Method fordeter mination of static modulus of elasticity in com-pression.

[3] ASTM C469-94. Standard test method for StaticModulus of Elasticity and Poisson's Ratio of concrete incompression.

[4] DIN 1048/1:1978. Testing concrete; testing of freshconcrete.

[5] NT BUILD 205:1984. Concrete, hardened: Modulus ofElasticity in compression.

[6] UNI 6556:1976. Testing concrete. Determination ofSecant Modulus of Elasticity in compression.

FURTHER INFORMATION

Controls S.R.L.Via Aosta, 620063 Cernusco s/N. (MI), ItalyT +39 029 21841 · F +39 029 2103333controls@controls.it · www.controls.it

Fig. 2: MCC8 servo-hydraulic automaticcontrol unit

Fig. 3: Main window of the E-Module soft-ware for the automatic determination of theElastic Modulus.

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