FAQ: Moisture measurement

Question:A Customer has sent us a spring scale, which no longer measures weigths correctly. Can you even set anything there?

Answer:With each CM-Device you get a control weight. If the scale is tared correctly, you can easily chek its function, using the weight, on your own. We cannot really "set" anything else, we would have to send it in.

Question:Do you know if your CM-Ampules are identical to the ones of TROY? In this case, we would like to order some from you. Thank you for your help!

Answer:Our ampoules are in accordance to the DIN 18560-4 sample form. Filling capacity: 7.0g +/- 2 M-%, Graining 0.3 to 1 mm, with minimal dust content. Our ampoules minimaly differ from the ones of TROY in relation to grain size. The filling capacity, however, with TROY is considerably more variable, than with our ampoules. We have found filling capacities between 5 and 6 g. Therefor these ampoules are not ideal for testing the reainess of screeds. However, for moisture measurements of bulk with a completed reaction, the individual filling capacities are not extremely relevant.

Question:Hello CPM-Team, We need 20 Ampoules of calciumcarbide. Can we order them with you? If yes, we would like to get a quote. In addition, we need a new instruction manual for our device. It is already an older device and from Troy. At the bottom of the device, there is the number 52. Do you have any instruction manuals for this device, or is this device compatible with the older device?  

Answer:Thank you for your question. We do not have any instruction manuals for Troy devices, however, our devices are completely compatible with those of Troy. Troy no longer produces CM-Devices. Nowadays, screed readiness is tested in accordance with DIN 18560-4. You can find explanatory videos on our website using this link: Click here for the videos! You can find our carbide ampoules (according to DIN 18560-4) in our Web-Shop.

Question:Is it possible to read the CM value directly off of the manometer and do you have to convert something?

Answer:The outer, black scale of our manometer always shows the pressure. You can read CM-Value directly off of the Manometer, when you use one of the 3 coloured scales for the different sample sizes of 20, 50 or 100g. The measurement value for a 50g sample size (green scale) lies at around 4.8 CM-% (cement screeds and concrete). For a 100g sample (blue scale) of a calcium sulfate or and anhydrite screed, the measurement value lies ar 2.4 CM-%. 20g samples are not aloud to be used for testing the readiness of screeds. , as the chemical reaction cannot be completed with this sample size, and wrong results are presented. 20g samples are only used for moisture measurements of bulk (Sand), wer a chemical reaction can be completed. The blue scale is the outermost scale of the coloured scale, and allows for an easier reading, even for low measurement values. Manometers have to be calibrated once every year. For the evaluation of the calibration there is the red-green crosshatched area. When the pointer is inside the green zone (at 20°C outside temperature). The new Manometer CLASSIC can be found as a replacement manometer in our Web-Shop.

Question: How large is the necessary sample size for the testing of the readiness of anyhdrite screeds?

Answer: Dear Client, I can confirm that a sample size of 50g is more than enough for the testing of the readiness of anydrite screeds. However, a manometer of the accuracy classs 0.1, like our digital manometer "Business" is required. It is important that the tested sample, is actually a sample taken fromm all of the transverse section, not just from the surface. You can find more tips and tricks in our Youtube Videoafter minute 5.

Question:How durable are the carbid and water ampoules?

Answer:If not damaged, the have an endless shelf-life.

Question:Dear Sirs and Madams, for a couple of years now we have been using a Radtke CM-Device CLASSIC to test our screeds. Now I am in a situation wher 2 BV (?) have to determine the exact rest moisture value in plaster (wet rooms, limestone-cement plaster). Can I figure out the exact rest moisture value of the plaster using a Radtke CM-Device, what do I have to observe? I would be thankful for a quick answer.

Answer:Dear Sir, Thank you for your question and thank you for being happy about our products. You can measure plasters. Use 50g of sample material carry out the measurement analogously to the measurement procedure of the readiness of screed according to DIN or with our curshing rod (see Vidoes on our Website). In addition you can do a Material-Climate Measurement. See the vidoe for combined material cliamte/CM-Measurements on our youtube channel. I hope to have been able to help you, and am available for any further questions you might have.

Question:"Dear Mr Radtke You have already been able to answer my questions concerning the Measurement of aerated concrete. Thank you again for your quick answer. Now I have another sample measurement with a „new“, by the building materials trade stored stone. Result: 0,25 Mass%/ 0,13 Now I have a questions on this topic, but also generally about measurements, as it is the first time I have done a CM-Measurement. It would be really nice of you to answer me these, even though these questions might be extremely simple.
1) Since I should carry out an evaluation of an earlier wet aerated concrete block to give the approval for a coating, I should know if I can directly compare the measurement results (maximum 5%, I have to ask whether Darr method or CM Measurement) with the manufacturer's information or if something else has to be taken into account in the evaluation of the measured value, since the material has a certain absorption temperature or equilibrium humidity/ equilibrium constant as screed, or possibly has a different amount of proportionate free water.
2)Is the measurement different of a CM-measurement in comparison with the Darr Method of aerated concrete also set at around 1.5?
3)As the sample is extremely light, 50g was just about one sample cup, can more than one sample cut be poured in, if the material should be even lighter?
4)Questions about the Measurements generally: I have a digital manometer and a mixing rod. Should I measure without the mixing rod, as I barely even need it for aerated concrete any way, as the sample is so fine, (or should the sample of aerated concrete not be made much smaller anyway to stop any water from evaporating). When do I have start the manometer? immediately after the closing the bottle, or only after I have started shaking the bottle. Can the result be wrong, when I start my measurement later? the pressure should stay the same.
5)Cleaning of the Utensils: On the bottom of the manometers, the balls and maybe also the bottle, small bits of material samples settle. I could remove them with either water or with a spatula. How clean do the components have to be for the next measurement?
6)Amount of Balls: In every single explanation, you talk about the use of 4 balls (3 large, 1 small) however, I have 5 balls (3 large, 2 small). Should I use all, or is the second small one an extra?
7)Is there any trick to release some of the pressure in the bottle before opening them after a measurement? Sorry for the weird questions, but it would be nice if you could answer them.
Thank you in Advance, all the best. "

Answer:Answer to 1) You have to find out how the 5 M-% have been determined, and depending on that evaluate the situation.
Answer to 2) the difference between the Darr method and the CM-Measurement is the result of the Cement-lend-part of a sample and lies between 0.8 and 1.6 M-% (See the PDF-Sample).
Answer to 3) The conversion of pressure to humidity depends on the material density. The current conversion formula is for concrete and creeds. For foamed material the system would have to be calibrated in a new way.
Answer to 4) You can’t make any sample material to fine. The manometer always has to be started before you start shaking the bottle. By starting the manometer, you set the zero point. If the reaction has already begun, before the manometer has been started, it will start at a wrong zero point and will show you a too low pressure.
Answer to 5) It is enough for you to use the brush. Strong sticking material can be removed using a steel brush. It is more important that no carbide or water stays inside the bottle.
Answer to 6) When you have to small balls you only have to use one and keep the second in case you lose the first.
Answer to 7) Open the lid in a controlled fashion, so the pressure can escape slowly.

Question:One of our clients is having problems with a measurement. Here his question: "... for a cement (very dense) and only 4 cm strong, who can 3 innert 3 months, the client gets a value of 2.6 CM-% when using 20g. How is that possible? or is there a different table I have to use?" Can you understand the question an help us out? Thank You!

Answer:Dear Sir, Thank you for your question. Your Client has to work with 50g sample sizes when working with cementious systems. 20g deliver a result that is too high and are wrong! Have a look at the Vidoes on our Website, we never talk about 20g of sample size.

The clients answer: Good Morning Mr Radtke, thank you for your quick answer and the Solution to our problem!

Question:Dear Mr. Radtke Thank you for your answers and the PDF. I have looked at your PDF and received a lot of information through it. In reference to the Measurement of the aerated screed block, I am still not quite sure about what I should do. In reference to the comment on point 3: 
„The conversion of pressure to humidity depends on the material density. The current conversion formula is for concrete and creeds. For foamed material the system would have to be calibrated in a new way. „ Would a measurement or an interpretation of the measurement value with such a light building material as aerated concrete, without a recalculation, not possible? What I really don’t understand: 
- due to the low density i automatically have mor material volume. -The carbide (defined amount) reacts with the free water amount and therefor creates the respective pressure. Therefore, due to the pressure and the amount of water, the amount of the available amount/mass of the sample material could be defined. -or does the larger volume of the material sample in relation to the size of the bottle and the pressure development? In case of doubt I would have to pack up a material sample and let it exactly be determined with the darr method. However it would be a lot better to be able to determine it on-site via the cm-method. I have one more question concerning measurements with digital manometer: -Should the measurement process of the manometer be started right before breaking the carbide ampoule, or only after shaking it 3 times, after 10 minutes. Thank you, and all the best.

Answer:Dear Mr L, the pressure can also develop in the pores of the material, so they count to the free volume of the bottle. If a certain amount of water reacts with carbide, a new amount of gas gets created, which, in a sealed, fixed container (CM-Device) can build pressure or in a flexible closed container (a balloon that can change its volume). Depending on the volume of the fixed container a pressure A or a pressure B gets created. This pressure can always put into correlation to the reaction of water. Is the same amount of Water only in the porous sample material X and Y, and is the Pressure of the sample material (not only the raw-pressure!) between the samples different, so the pressure out of the measurement of sample X is larger than that of sample Y, when the pressure of sample X is smaller than the pressure of sample Y. The Sample Y needs more space than sample X. aerated concrete is a mineral building material. In relation to aerated concrete, the standard translation could be used. With foamed material it is different. There, the pressure is a lot below one. You put a lot of thought into details which may have a possible influence to the second decimal point. If you want to make a simple comparison between the Darr method and the CM-Method, you dry out the Darr sample at 40°C(ca. 25%rF). This is in accordance to exactly that specific CM-Value. Concerning the handling of the digital manometer I would like to refer you to our video of: „On-Site Calibration of the digital Manometer“. In it, you can see that the manometer has to be made hot, bevor you can start measuring something with it. Here you can find this, and other videos. All the best

Question:Dear Mr Radtke, From our expert for flooring technologies, Mr XY, who speaks of you in the highest notes, I have been told to consult you if I have any questions or problems: 

We have been using your measurement device for a long time now. Our measurement results have always been logical and we have not had any struggles or problems. With this building site we have now, we taken around 15 measurements in the past couple of weeks. There is an upper and a lower floor. The lower floor had about a 7 cm thick cement screed, the last measurement had a value of 1.6 cm %, so a readiness according to german standard (heating screeds without accelerators) which lies at 1.8 CM%. The upper floor still has a value of 2,1 CM%. Here, the screed has a thickness of 9,7, rather high (and it was a winter building site). Now to the problem: The Architect does not believe our measurement results, as the screed layers say, at a temperature of 26 °C, you can take off 1% of the Results. In addition he has sent us a measurement manual, in which, on page 24, there is talk about reducing the pressure when confronted with Temperature in-balances. In what way does this concern the moisture measurement results? We have a floorer expert, whom we sent a sample who confirmed the measurements. FYI: We wear gloves to avoid any unnecessary extras humidity, fill the samples directly into sample bags, and take the material out of an overall average, where we leave out the top 0,5 cm to avoid any unnecessary dirt and throw that part away. The sample gets taken up to the resisitive laayer.

Answer:"Good Evening, Thank you for you question, I can give you a quick and easy answer. Concerning the temperature of 26°C, it is possible to remove not only 1% but 2% of the pressure value (or CM-Value), (please don’t be surprised), but this means not taking of 2% of the absolute value, but to relatively take of 2% of said value. Example: CM-Value is at 2.1 CM-% at 26°C (Beginning and End Temperature). you can take of 2% of that value so: 2.1* 2/100 CM-% = 0,042. I think, you did everything correctly, and in this case, it is the screed floorers fault, due to the excessive thickness of the layer screed. The screed on the upper floor will need about twice as long to dry, in comparison with the screed on the lower floor ((9.7/7 squared = 1.9). I would recommend to do an On-Site Calibration in front of the architect and the either show him the respective video on our website, or show im the page in the instruction manual concerning the temperature effect. I hope I have been able to help you with this, all the best.

Question:Dear Sirs and Madams, we have a CM-Device of yours. Normally we use it to measure screeds. Now we are supposed to measure the moisture of aerated concrete. Is this possibl using the CM-Measurement Method, or only using the Darr method? Thank you for a quick answer, or even better a quick explanation.

Answer:Dear Sir, Thank you for your question. Quick answer: Yes, you can use it to determien the amount of free water in an aerated concrete. Work with a 50g sample and using the normal measurement procedure according to DIN 18560. Why is it important to use said correct measurement procedure? When testing the readiness of screed of mineral building materials, the chemical reaction, as is common in the measurement procedure according to DIN, is not completed. Thats why you will receive different measurements using the CM-Method than when you use the Darr Method. When using the Dar Method (Drying at 105°C) you determine the evaporable watercontent. When using the CM-Method according to DIN 18560, you determine the free water content of a mineral sample. I hope I have been able to help you with this, and am here if you have any further questions.

Question: Dear Mr. Radtke l Maybe you will be able to help me out here. I have the following problem: We want to lay a prefabricated parquet in a single family home. The cement screed without additives was played here about 12 weeks ago, 6-9.5 cm thick. The heating program has run through. However, after multiple measurements we still haven’t been able to reach a CM Value underneath 2.1 CM-%. The developers have, in response to this, set up industrial space heaters and filed down the screed. We don’t know what else to do, and hope for your help, about what we could do next. Could it be that the screed has been put in in too thick of a layer? Thank you for a quick answer All the best.

Answer:Good Morning, Thank you for your question. 12 weeks of drying time for a screed with a thickness of up to 9.5 cm is rather short. The drying process can be supported by continuously heating. Has the screed been vacuumed after the filing down? In such a situation, the KRL Measurement Method would be an interesting addition, to see, if the screed even „wants“ to continue drying A screed with a high cement value can store more rest moisture than one with a low cement value, and will be ready for laying even though he might have a higher value. I suggest you use a „combined KRL-/CM Measurement“. How it works, what you need for it, and how you can interpret the results can be found on our youtube chanel. Should you be interested in owning your own equipment to try this out in future, you can find everything from simple beginners equipment up to professional ones on our website. All the best.

Question:Dear Mr. Radtke, Thank you for your quick answer. I will discuss this with the developers. You say that 12 weeks are not enough time for such a screed to dry? Are there any empirical values I could show them? I have one more question: How high of a temperature is a screed maximally aloud to have, and how does this influence a measurement?
Thank you for your help!

Answer:No problem! As long as I have time, I like to help- To your additional questions: 
1. The drying time of a screed is always in proportion to its thickness, squared. So: a 4cm thick screed would theoretically need 4 weeks to dry. A 6cm thick screed would then need 1.5x1.5x4 cm, meaning 9 cm, and therefore ann 8 cm thick screed would need 2x2x5 weeks, 16. A 9.5cm thick screed would need 2,25x2,25x4 weeks, so over 20 weeks. And this only if the conditions stay the same for all those weeks, as they were in the first 4. 2. A restriction for the screed temperature for CM-Measurements doesn’t actually exist. The higher the temperature, the more careful you have to be during the sampling process. Higher temperatures allow water to mobilizes. It can therefore move around and away more easy, and thats why you have to be more careful. All the best.

Question:In one of your videos you show how a manometer looks like after an explosion in a bottle which was due to a spark. You also tell us how it can be prevented. I don’t quite understand how and what it has to do with the sampling, the crushing and the chemical reaction of carbide with water. The reaction always happens, and the spark gets created by the balls of the bottle grinding the material. The carbide is in there allready as well… A spark could therefor always happen when you shake the bottle. I would be thankful for another explanation

Answer:Thank you for your question If there is any flint stone, that comes into contact with the balls during the crushing process, there will be a spark. The spark, however, is not going to do anything, as there hasn’t been any reaction, therefor no acetylene, yet. This piece of flint won’t create another spark. Through the crushing of the sample material before the reaction, the mixture only has to be shaken for an additional minute, so only a third of the original time. According to our thoughts and studies, the chance of any more sparks can be reduced dramatically.

Question:Nowadays there are solace „Turbo Systems“ as a supplement for quicker drying of screeds (cement/anhydrite). Do such chemicals falsify the CM-Measurements? Where do you have to be careful? Does this have to be noted in the measurement protocol?

Answer:The only chemicals which can falsify a CM-Measurements is methanol. Only methanol reacts with water the same way as calcium carbide. Methanol does not get used when construction screeds. Thats why CM-Measurements measure very specific amounts of water. Through the dictated measurement procedure the amount of free water of both mineral and plaster based systems can be accurately determined. Thats why additives don’t actually influence the measurements and the results. It needs to be considered, that next to the known additives in cements, which reduce the amount of water found in them, there are also so called quick cements. They create ettringite when they dry. Ettringite is about 50% Water. The crystalline bound water, however, is rather unproblematic, as it isn’t mobile. Manufacturers of additives often offer there own CM-Measurement services, through their own field workers. It is always a good idea to write down any and all additives in your protocol. Everything known should be put down in the protocol, as it might help to a later point in time.

Question:Could you please tell us the netto amount of CALCIUM CARBIDE which is in a 25-ampoule set. We need it for the dangerous goods specifications for the forwarders.

Answer:You can find this information on the package itself, on the delivery order, as well as the invoice. One package contain s 175g of Calcium Carbide UN1402 (25x7g) and can generally be forwarded as EQ E2.

Question: Hi! How are you? I have a question. I own a CM - Measurement Device by Riedel - de Haën. When it was broken, my previous boss replaced the original manometer with a product by Troy. For the second manometer I don't have an instruction manual or a conversion table - gas pressure with moisture values in percent, only that of Riedel-de Haën. Are there any differences? It would be great if you could help me out, so I an avoid any errors when reading the moisture values of screeds. I would be really happy to get an answer.



Answer: Dear Mr A., Your Troy manometer works perfectly with the Riedel bottle, and the conversion calculations as well. Troy is a successor of Riedel, so there aren't any problems! Does this help you? All the best, Dr. Fränk

Answer from customer: Oh ok! So I have to read off of the black scale? Only asking, as my last CM-measurement was about 17 years ago. Thank you very much! By the way, great YouTube Video’s!