4 edition of Determination of moisture levels in structural concrete using pulsed NMR found in the catalog.
Cover title.Southwest Research Inst.; Portland Cement Assoc.--1st prelim. p.Final report.April 1982.Contract no. DOT-FH-11-9487.Report no. FHWA/RD-82/008.Includes bibliographical references.
|The Physical Object|
|Pagination||xvi, 109 p. :|
|Number of Pages||94|
nodata File Size: 1MB.
Duden. Die englische Rechtschreibung. Orthographie des Englischen und Amerikanischen. (Lernmaterialien)
Spectrometer 10 is preferably of the same type as the CoreSpec-1000, currently available from NUMALOG LTD. During hydration a part of the mixing water is chemically combined in hydration products and the residual water is confined in pores, which gradually decrease in size as cement hydration proceeds.
DETERMINATION OF MOISTURE LEVELS IN STRUCTURAL CONCRETE USING PULSED NMR An investigation has been conducted of nuclear magnetic resonance NMR as the basis for nondestructively measuring moisture content in concrete. By using OSA NMR, profiles of moisture and density can be determined on-line during panel fabrication. Furthermore, changes in the chemical structure of the bituminous coal samples with different moisture content subjected to HVEP were investigated by Fourier transform infrared spectroscopy FTIR.
The amplitude A of the 1H-NMR signal is a measure for the hydrogen density and with it for the water content see Fig. Nowadays, the raw density profile in wood panels can be measured on-line with devices based on Compton backscattering .Analysis of Complex H-1 NMR Relaxation Measurements in Developing Porous Structures--A Study in Hydrating Cement, J.
Another preferred embodiment includes a probe which can make the NMR T2 distribution measurements in a sensitive volume below the surface of the concrete. state that "the spin-spin relaxation times of water in these rehydration experiments is only a few milliseconds, so the quality of traditional spin-echo images is disappointing.
: The Division ; Springfield, Va. Measurement techniques mainly based on electrochemistry and electromagnetics.
The test is used to determine the corrosion activity of reinforcement bars in concrete structure, which is an indicative of permeability of concrete. A different behavior of the time dependent T2 distribution leads to a different final strength, or other property, of the concrete. If in the final analysis, the concrete does not meet the standards, the building may have to be reinforced or even torn down, perhaps incurring major additional costs. The premature addition of load bearing members could lead to cracking of the concrete structure.
By comparing measurements made Determination of moisture levels in structural concrete using pulsed NMR a new concrete sample with the known tables, one can measure or predict the strength, or other property of the new concrete sample.
Spin-lattice relaxation is an energy effect, and is the loss of the excess energy resulting from the excitation pulse to the surroundings, or lattice, as thermal energy. This result indicates a water content increasing strongly in depth. And the results of weighing are consistent with those of LF-NMR.
Apparatus 20 is preferably provided with an RF shield 30 for isolating the magnets 22 and coil 24 from environmental noise. There is also provided in accordance with a preferred embodiment of the present invention, a method for predicting a property of a porous material while curing, the porous material including therein a liquid which undergoes metamorphosis and which is present in the porous material in different phases during curing, the method including the steps of: performing a low frequency, spin-echo nuclear magnetic resonance NMR measurement of each phase of the liquid; and extrapolating the property based on a predetermined relationship between the property and the NMR measurement.
NMR relaxation measurements could help to accurately control concrete work production and mixing as well as to monitor workability and strength development after setting.
The physical background is described.
The concern of the present study was to demonstrate the feasibility of monitoring the hardening in concrete by conducting T 2 measurements not only with laboratory NMR equipment but also with OSA NMR, offering the possibility to inspect early-age concrete on a building side.