瑞典专利SE1250760A1 Determination of moisture and pH in concrete

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专利摘要:
The invention relates to a method for determining the amount of moisture in concrete. At least one first concrete sample is taken from a piece of concrete. The test weight is then determined by weighing the concrete sample. Furthermore, the concrete sample is dried so that all liquid leaves the concrete sample. Next step is determination of the dry weight by weighing the dry concrete sample. The dry concrete sample is then placed in test liquid until saturation is achieved. The maximum weight is determined by weighing the saturated concrete sample. Finally, the amount of port fluid in the concrete sample is determined by comparing the sample weight of the concrete sample and its dry weight. The degree of filling of the pores in the concrete thickness is then determined by determining the relationship between the amount of pore fluid in the concrete sample and the maximum weight of the concrete sample. Fig. 1
公开号:SE1250760A1
申请号:SE1250760
申请日:2012-07-04
公开日:2014-01-05
发明作者:Jan Olof Tegnesjoe
申请人:Pentec Nordic Ab；
IPC主号:

专利说明:

15 20 25 30 35 This strongly alkaline and strongly hygroscopic liquid can over time fill the pores of the concrete completely. If the concrete pores are filled and the cement structure of the concrete functions as a semi-permeable membrane, there is a possibility of the formation of osmotic pressure.
Osmotic pressure inside the upper part of a concrete floor, e.g. a concrete slab on the ground can cause reflections of wear layers of floor epoxy or of surface treatments with floor paint or equivalent. An increasing pH value in concrete can initiate a chemical decomposition or decomposition, among other things, of organic additives in the concrete or organic building materials in direct contact with the affected concrete structure.
Organic concrete additives containing ammonia and formaldehyde are normally passive in unaffected concrete. With rising pH values in the concrete, these substances can be released. Potentially, ammonia and formaldehyde can leak into the surrounding air environment above the concrete slab with known effects on people staying in such premises.
Plastic mats on concrete floors with degraded carpet glue and disturbing emissions into the air environment above are well-known problems that are directly caused by increasing pH values in the concrete floors.
Commonly used moisture measurements of RF, Relative Moisture in concrete and / or ambient air environment do not give a satisfactory answer to the presence of aggressive saline solutions inside the concrete that are not evaporable in normal living environment with normal temperatures.
The best known method for determining moisture and pH in concrete slabs involves taking a large concrete sample from the concrete slab or using the entire concrete slab.
The concrete is crushed and pulverized. The pore liquid is then pressed or extracted out of the concrete for measurements and analyzes. The method is energy-intensive, cumbersome and expensive. Finally, the method is destructive, ie. an analysis thus performed on a concrete slab means that a new concrete slab must be cast.
Nowadays, there are newer and cheaper methods described in the Scientific article “The pH measurement of concrete and smoothing mortar using a concrete powder suspension” by Räsänen, V. and Penttala, V. published by the Helsinki University of Technology's unit for road and water construction.
The article describes a method for determining the pH value of a concrete slab where a relatively large sample is taken from the concrete slab. The sample is crushed and weighed to determine its original weight. Then distilled water is added to the crushed sample and the whole solution is shaken until an even solution is obtained. Finally, the pH of the solution is measured by titration or by a pH electrode immersed in the solution.
Although this method of analysis is significantly cheaper than the standard measurement method, it has the disadvantage that it still requires machine equipment to crush and pulverize concrete pieces.
The method does not provide an answer to the amount of pore liquid or pore filling degree in hardened concrete. Another variant is described in the Dutch patent publication NL8901900. The publication describes a method for measuring the amount of moisture in materials. In the example mentioned in the document, the amount of moisture in sand that is intended to be used when mixing concrete is determined.
The method is based on taking a sample from the original moist sand in the first step and weighing the sample. The sample is then protected until all moisture from the sample has evaporated. In the next step, the weight of the dried sample is measured and a value is obtained for the amount of moisture in the original sample by forming a difference between the weight of the sample and its original weight. Since the method is specifically aimed at sand that is to be included in a concrete mix, it cannot be applied to hard materials without any problems. Furthermore, the method is not suitable for determining the pH value in concrete or for determining the degree of filling of pores in hardened concrete.
Thus, there is a need for a simpler and more cost-effective method for controlling moisture and the pH value in concrete, which also does not significantly destroy the concrete.
SUMMARY The present invention seeks to remedy at least some of the shortcomings of the prior art in the art.
A solution according to the invention is provided by the features of claim 1.
Preferred embodiments of the solution according to the invention are given by the dependent claims.
According to one aspect of the invention, the method of the invention comprises taking at least a first concrete sample from a piece of concrete. The sample weight of the concrete piece is determined by weighing the concrete sample. The concrete sample is then dried so that all the liquid leaves the concrete sample and its dry weight is determined by weighing the dry concrete sample.
Then place the dry concrete sample in sample liquid until saturation is achieved. Upon saturation, the maximum weight of the sample is determined by weighing the saturated concrete sample. Then the amount of pore liquid in the concrete sample is determined by comparing the sample weight of the concrete sample and its dry weight. Finally, the degree of filling of pores in the concrete piece is determined by determining the relationship between the amount of pore liquid in the concrete sample and the maximum pore volume of the concrete sample.
The advantages of the method according to the invention are that it is relatively cheap and quickly feasible. Furthermore, it is negligibly destructive of the conditions to be measured. The method according to the invention enables measurement and control of moisture and pH values at an earlier stage in hardened concrete. It provides sufficiently accurate values for the type of moisture present in the concrete and how much. The method according to the invention also provides a basis for decisions on whether to make the necessary change or rehabilitation on the concrete.
In addition, if the method is carried out at different depths in the concrete, where for example a first sample is taken near the upper part of the concrete piece, a second sample substantially near the middle of the concrete piece and a third concrete sample near the bottom of the concrete piece, one can also get perception of where somewhere in the concrete structure the moisture is accumulated and what damage risks may exist.
It should be mentioned that in buildings and similar concrete structures the first sample can be taken near a floor layer adjacent to the upper surface of the concrete piece and that the third sample can be taken near a ground layer on which the concrete piece can be placed.
In outdoor concrete structures, such as bridges and the like, the first sample can be taken closest to the surface of the concrete piece, the second sample at substantially half the depth of the concrete piece and the third sample near the second interface of the concrete piece on the other side of the concrete piece. It should be mentioned, however, that the number of samples is illustrative only.
One can very well imagine ﬂ er or fewer number of samples as needed.
BRIEF DESCRIPTION OF THE FIGURES Fig. 1 shows a cross section through a concrete slab.
Fig. 2 shows a flow chart illustrating an embodiment of the method according to the invention.
DETAILED DESCRIPTION Fig. 1 shows a cross section through a concrete slab 100. Although the example in Fig. 1 relates to a concrete slab, the invention is not limited to concrete slabs only. In principle, it can be applied to any type of concrete that is strongly alkaline or thoroughly carbonated and that over time absorbs moisture either from the ambient air or from other moisture sources.
The concrete slab 100 comprises an upper part 140 which in buildings is placed closest to a floor layer (not shown) which may be an epoxy layer or other protective layer on top of which floor material may be placed. Furthermore, the concrete slab 100 in the example is placed on a support layer 170 which may have different structure and which is in contact with the lower part of the concrete slab 149.
The concrete slab 100 is generally porous and includes small pores 145 in which there may initially be a small amount of water. The water comes partly from the original concrete mixture and partly from the moisture in the base layer 170 on top of which the concrete slab is placed 100. We assume here that the concrete slab 100 lies directly against the base layer 170. If the concrete or concrete slab is in the open, water in the form of water vapor can also ambient air penetrates into the pores 145 of the concrete slab 100.
Fig. 1 also shows three samples 110, 120 and 130 which have been taken at different depths in the concrete slab 100. The first sample 110 is taken at the upper surface 140 of the concrete slab 100, the second sample 120 substantially in the middle of the concrete slab 147 and the third sample 130 near the lower surface 149 of the concrete slab 100.
The purpose of taking three concrete samples at different depths in the concrete slab 100 is to create an idea of the moisture profile through the concrete slab 100. By studying the moisture content of the concrete slab 100 in the above-mentioned three regions, one can then determine if it is necessary. preventive measures to prevent moisture damage to the concrete slab 100 which may later result in damage to the floor layer closest to the upper surface 140 of the concrete slab 100.
Furthermore, the moisture profile obtained by taking samples 110, 120 and 130 at different depths can give an indication of how close the concrete slab is to developing damage in the case of a reinforced concrete slab.
Fig. 2 shows a fate diagram with a detailed description of how moisture measurement in a concrete slab such as the concrete slab 100 in Fig. 1 can take place.
In step 200, one or two smaller concrete samples are taken from a piece of concrete such as the concrete slab 100 in Fig. 1. The sample need not be very large if it is assumed that the moisture in the region of the concrete slab where the sample is taken is evenly distributed. Then, in step 210, the weight of the concrete sample is determined. This can be easily achieved by weighing the concrete sample. In this way, the starting weight for the concrete sample has been determined, which will be used in later calculations where the moisture content of the concrete sample will be determined.
In order to be able to compare the moisture content of the concrete sample with dry concrete, the concrete sample is dried in step 220 so that all moisture evaporates from the concrete sample. For example, the concrete sample can be heated in a laboratory oven at a temperature of 105.2 ° C or higher. It should be mentioned, however, that any method can be applied to evaporate the oil from the concrete sample, such as microwaves and other materials.
Then, in step 230, the dry weight of the concrete sample is determined. In order to then be able to determine how much moisture the now dry concrete sample can absorb at most, the concrete sample is placed in step 240 in sample liquid until the sample is saturated. The sample liquid may be distilled or deionized water. Once the sample has been saturated in step 240, the maximum weight of the sample is determined by weighing the saturated concrete sample in step 250.
In step 260, the amount of pore liquid in the saturated concrete sample is determined by determining the difference between the dry weight of the concrete sample and its sample weight. The result is the weight of the pore liquid expressed in grams. A very simple way to calculate the weight of the pore liquid is to form a difference between the two weights.
The amount of pore liquid is already an indicator of impending problems in, for example, concrete base plates which can result in cracked floor layers above the concrete slab or in av-coated epoxy layers or degrading saponification and saponification of, for example, carpet adhesive.
By determining the degree of pore filling in step 270, an even more accurate measurement value is obtained on how saturated the pores of the concrete sample are and within what time frame one can expect moisture-based problems in buildings and other concrete structures. One way of determining the degree of pore filling is to form a ratio between the determined amount of pore liquid in the concrete sample in grams and the difference between the maximum weight of the concrete sample and its tonnage.
However, the above method should only be seen as an example of an embodiment of the method according to the invention and not as a limitation of the invention. It is also possible in the same step 240 to determine the pH value of the pore liquid in the concrete. In this way, three measurement values are obtained which give a very detailed characteristic of the concrete slab to be measured, namely the amount of pore liquid in the analyzed concrete sample, the degree of pore filling and the pH value of the pore liquid. The latter measurement value provides information on how prone the concrete block is to attract water. In cases with very high pH values of the pore liquid (up to pH 14), it is necessary to take preventive measures that prevent moisture from penetrating into the pores of the concrete block at all. A high value of the pore filling degree can indicate impending problems with cracks in layers closest to the concrete slab and corrosion of the screed in the concrete (if the concrete has such a structure) which ultimately results in cracks in the concrete due to the expansion of the screed.
Furthermore, it is possible to determine in step 270 or in a later step (not shown) the pore volume in the concrete piece. This value in combination with one or both of the values the amount of pore liquid and the degree of pore filling can provide a more accurate information about when the pores of the concrete piece will be filled and create potential problems in buildings or concrete structures (lined or not). The pore volume can be determined, for example, by forming a difference between the maximum weight of the concrete sample and its dry weight divided by the specific density of concrete. pH determination in sample liquid can be done either via a measuring electrode or by titration. It can be assumed that when the dry concrete sample has been saturated by the test liquid, the measured pH value at this time is stable. Regardless of the method, the pH of the sample liquid can be measured by determining the hydrogen ion concentration in it.
It should also be mentioned that the method gives an even more reliable result by taking ﬂ your concrete samples at different depths in the concrete slab as described in Fig. 1. The steps in Fig. 2 then become identical for each concrete sample taken. Taking ﬂ your concrete samples has the advantage that at an even earlier stage you can identify potential moisture problems that are ﬂ your years ahead in time and take action at an early stage before these problems emerge.
The method can just as well be applied to concrete floor slabs as to concrete floors and concrete structures in general. Furthermore, the method can be applied to concrete with a suspected or proven risk of degradation based on so-called Alkali - Silica - Reaction (ASR or AKR).

权利要求:
Claims (10)
[1]
A method for determining the amount of moisture in concrete, comprising: - taking at least a first concrete sample from a piece of concrete; determination of the sample weight by weighing the concrete sample; - drying the concrete sample so that all liquid leaves the concrete sample; determination of the dry weight by Weighing the dry concrete sample; placing the dry concrete sample in sample liquid until saturation is achieved; determination of the maximum weight by weighing the saturated concrete sample; determining the amount of pore liquid in the concrete sample by comparing the sample weight of the concrete sample and its dry weight, and - determining the degree of filling of pores in the concrete thickness by determining the relationship between the amount of pore liquid in the concrete sample and the maximum weight of the concrete sample.
[2]
The method of claim 1, further comprising determining the volume of pores in the concrete piece by comparing the maximum weight of the concrete sample and its dry weight relative to the specific density of concrete.
[3]
A method according to any one of claims 1 or 2, further comprising taking a second and a third concrete sample from the concrete piece, wherein the concrete samples are taken at different depths in the concrete piece.
[4]
A method according to claim 3, wherein the first concrete sample is taken near an upper surface of the concrete piece, the second substantially in the middle of the concrete piece and the third near a lower surface of the concrete piece.
[5]
A method according to claim 3 or 4, comprising determining the concrete profile of the concrete piece by associating the amount of pore liquid to the degree of filling of the pores in the concrete piece for each concrete sample.
[6]
A method according to any one of claims 1-5, further comprising determining the pH value of the concrete piece by measuring the hydrogen ion concentration in the sample liquid in which the dry concrete sample is placed.
[7]
Method according to claim 6, wherein determination of the pH value of the concrete piece is performed at the same time as the determination of the maximum weight of the concrete sample.
[8]
Method according to claim 6 or 7, wherein the determination of the pH value of the concrete piece takes place continuously until a stable pH value has been reached.
[9]
A method according to any one of claims 1-8, wherein drying of the concrete sample takes place by heating at a temperature of at least 105.2 ° C.
[10]
A method according to any one of claims 1-9, wherein the sample liquid comprises distilled water or deionized water.

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同族专利:

公开号 | 公开日

SE536511C2|2014-01-14|

引用文献:

公开号 | 申请日 | 公开日 | 申请人 | 专利标题

法律状态:
2017-03-07| NUG| Patent has lapsed|

优先权:

申请号 | 申请日 | 专利标题

SE1250760A|SE536511C2|2012-07-04|2012-07-04|Determination of moisture and pH in concrete|SE1250760A| SE536511C2|2012-07-04|2012-07-04|Determination of moisture and pH in concrete|

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