Note: Descriptions are shown in the official language in which they were submitted.
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CA 02276617 1999-06-29
7
G PSM/Mv2/K39 PCT/NL97/00719
I9EUf PRF.ADD~L~ TO THE DESCRIETIQN
The invent=on relates to a method =or measuring
the quality of porous material, for znstance concrete.
Such a method is 3enerally known.
According to said prior art: method a cylinder
is removed from said body to be examined, after which
said cylinder is tested in a laboratory. Thus there is
question of destructive testing.
Further) an LSAT investiganion is known) in
which the quality of the concrete, in particular the
permeability thereof is determined b;~ the quantity of
25 water which is absorbed by the conerrate. However. this
concerns a ratheY inadequate method.
US-A-4 979 390 describes a method for measuring
the quality of conc=ete, wherein a blody produced of said
material is brough>r into contact with water, and wherein
subsequently the migration of said water into said porous
rnatQrial is determined after which the quality is
ascertained from the information thus obtained.
The aim of the present invention is to provide
such a method for testing the quality of concrete which
is not destructive, and which is sufficiently accurate.
It is noted that the determination of the pezmeability of
concrete has a large economic value. In particular in the
case of existing buildings the quality of the concrete,
in particular the permeability thereof, gives an in-
dication of the remaining life time o~ the concrete, and
the information can also be used as an indication far
possible reconstructive measurQS.
Thus the present invention provides a method
which is characterized by a nuclear magnetic resonance
apparatus for measuring the distribution of hydrogen
atoms in said body by means of nuclear magnetic
AMENDED SHEET
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resonance, and in that 'at least one detection element or
excitation element of the NMR. apparatus is connected with
the side of the vessel) opposite the open side of said
vessel.
As a consec,~:ence of said features it is
possible to determine precisely the rnigXation of the
water into said concrete in which. w:Lth the help with the
thus obtained inforntation, statement:3 can be derived
relating to the permeability of the c~encrete, after wrich
the remaining life time of the Concrf~te can be estimated,
and that possible reinstating measur~as, like the new
application of an outside coat, the ~3pplication of a
paint coat or the injecting with pla;~tics.
In this respect it is noted that from US-A-5
055 767 and from US-A-4 291 271 rneth~~ds and apparatuses
are lu:own using NMR for exploration of sail and rock, and
wherein the presence of hydrogen atoms is measu=ed. It
applies, however) to the measurement of a steady state.
See further original description page 2, line 5
AMENDED SHEET
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WO 98/29731 PCT/NL97I00719
d
2
possible reinstating measures, li ew application '
of an outside , a application of a paint coat or
The present invention also relates to an apparatus
for measuring the quality of porous material, for instan-
ce concrete, characterized by a nuclear magnetic resonan-
ce apparatus for measuring the concentration and the
distribution of hydrogene atoms in a body made from said
porous material by means of nuclear magnetic resonance,
and by means for bringing said body made of said porous
material into contact with water.
Subsequently, the present invention will be elucida-
ted with the help of the accompanying figures, in which
are depicted:
figure 1: a schematic cross-sectional view of an
apparatus according to the present invention which is
used with the execution of a method according to the
present invention; and
figure 2: a diagramm for elucidating the action of
the apparatus according to the present invention.
In figure 1 a concrete body 1 is shown, which is on
one side delimited by a surface to air 2. As discussed
before, the permeability of the concrete changes during
its life time; with increasing age the permeability for
water increases. To measure this permeability use is made
of a method for measuring the permeability comprising a
vessel 3 which is filled with water. The vessel 3 is
opened on one side, at which side it is located against
the wall 2 of the body 1 to be examined. At the opposite
side of the vessel 3 an NMR apparatus 4 is located. In
this respect it is noted that this concerns only the
probe of an NMR apparatus; it is very well possible that
the exitation quills of the NMR apparatus are located
elsewhere relative to the body 1 to be examined. By means
of a supply channel 5, connecting the vessel 3 with a
hopper 6 water is supplied to the vessel 3. Hydrostatic
pressure may be used as well.
CA 02276617 1999-06-29
WO 98/29731 PCT/NL97/00719
3
According to an embodiment use can be made of a pump
for maintaining a pressure within the vessel 3. When the
method is executed the following procedure is applied.
The apparatus described above is located with the
open side of the vessel 3 against the wall 2 of the body
1 to be examined. The body 1 to be examined can be a
concrete building, for instance a viaduct, a bridge, a
constructive part of a power station or another concrete
construction. Subsequently, at a time to water is supplied
from the supply vessel 6 to the vessel 3 after which the
water starts entering the concrete. The speed with which
this entering process is executed is of course dependent
of the permeability of the concrete. It is noted that
normally already a certain amount of water is present in
the concrete. This water will give rise to an NMR-signal
So.
This amount of water comprises the so-called cristal
water of the concrete, whereas it is not necessary, but
very likely, that as a consequence of the normal humidity
of the air "free" water is present in the concrete.
For measuring the water concentration in a volume 7
located in some depth under the surface, use is made, as
stated before, of an NMR apparatus. Such an apparatus is
known per se) for instance for medical applications. The-
rein such an apparatus is used for localising
irregularities in a living body to be examined.
In the present application such an NMR apparatus is
used for determination of the density of water, differen-
tiated to place and time in the concrete.
To make things more clear figure 2 shows the signal
of the NMR-apparatus at a certain location in the
concrete as a function of time. At a time tl, an increase
of the signal is observed due to the arrival of some of
the supplied water in volume 7. At the time tl the
increase of the signal and the shape of the curve are
used to estimate the quality of the concrete. It is noted
that by means of an NMR apparatus a constant magnetic
field is applied onto which is superposed a secondary
CA 02276617 1999-06-29
WO 98/29731 PCT/NL97/00719
4
magnetic field varying in time and location. The H-atoms
which are influenced by the magnetic field configuration
mentioned above give thereon a certain reaction which
reaction is measuring by means of the detection quills
(probe). By varying the distance between the NMR probe
and the surface of the body to be examined it is possible
to scan certain areas of the concrete body. Thus it is
possible to obtain a depiction of the concentration of
the H-atoms, and thus the H20-molecules as a function of
depth, the lateral coordinates and time. Thus, the
present invention allows to obtain a three-dimensional
depiction in the time of the migration of the water;
thus, an image can be made of the permeability of the
concrete after which statements can be drawn relating to
the quality of the concrete.
It will be clear that besides for concrete the
present invention is also applicable to other porous and
permeable materials.
Further it is noted that the humidification of a
part of the surface can also be made by other means.
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