PCE Deutschland building moisture meter / screed moisture meter (CM method) PCE-PMI 3

The screed moisture meter / screed moisture meter is a small and reliable measuring device for determining the moisture present in screed, concrete and wood, for example. Corresponding scales for measuring moisture are already stored in the library of the measuring device. After selecting the scale, the required measurement can be carried out with the moisture meter. The measurement result is displayed on the screed moisture meter after a few seconds both numerically and graphically. A separate alarm limit can be stored for each scale on the moisture meter. As soon as the set alarm limit is exceeded, an acoustic alarm is triggered on the screed moisture meter. In order to protect the inserted batteries, the test device switches itself off after 5 minutes of non-use. Another special feature of the measuring device is the possibility of displaying the calcium carbide method (CM% / CM method) for screed. For this measurement, too, the moisture meter is placed on the surface to be tested. The measured value is converted into a CM% value (calcium carbide method) using the corresponding scale. This gives the floor layer a reference value for the calcium carbide method. Calcium carbide method (CM method) for screed residual moisture measurement It is a well-known method for indirect moisture measurement. The carbide method is subject to clearly error-prone influencing variables. Since practitioners on site have been used to this method of moisture measurement for decades, it still plays a role, albeit a decreasing one, for example in assessing the ability of floor coverings to be bonded to the screed. In this method, calcium carbide reacts with water to form calcium hydroxide and acetylene. The water comes from the previously obtained sample material (10 ... 50 g), which is crushed in the reaction vessel by shaking steel balls that are also placed in the vessel for about ten minutes and allows the moisture in the vessel to react with the calcium carbide. The gaseous acetylene causes a pressure increase that can be measured and directly correlated to the moisture content. Reaction tanks made of stainless steel are used with a pressure gauge displaying the tank pressure. The readiness for laying a screed can thus be determined indirectly but with sufficient accuracy using the CM method. Advantages of the CM method / disadvantages of the CM method The advantages of the CM method for moisture measurement in the screed are that the test can be carried out quickly on site (in contrast to the time-consuming drying test), the sufficient accuracy and the results can be used in court in the event of a dispute. Due to heavily changed cement-screed mixtures (significantly changed water content / moisture content) in modern building construction, the informative value of the CM method can no longer be rated as very selective and the limit value of 2% moisture in the cement screed used to date for moisture evaluation can lead to wrong decisions lead to the assessment of eligibility. Additional benefits of the screed moisture meter from PCE Instruments The screed moisture meter from PCE Instruments offers the practitioner several options for measuring moisture on site or evaluating the residual moisture in the screed. The pure relative value measurement (relative scale), the reference to weight percentages and additionally the evaluation of the screed moisture using an evaluation approximated to the CM method. The screed moisture measuring device is therefore the ideal tool for checking the residual moisture in the screed or for determining whether the floor layer is ready for covering.

The screed moisture measuring device is adjusted and calibrated by PCE Instruments and can also be recalibrated at regular intervals according to specifications, for example in the ISO manual. The calibration confirms and certifies that the screed moisture meter / screed moisture meter always works in the specified measuring range with the stated accuracy. Screed moisture content In new buildings, when renovating old buildings or even in a separate room, quality must always come first. One of the top items on the list of things to pay special attention to is floors. Driven by the desire to finish a construction sooner, mistakes are often made and neglect of requirements such as applying the screed, respecting the time it takes to dry, and monitoring the drying process. As a result, major problems can arise shortly after the renovation. Although the screed is a material that is not obvious to see, one should not skimp on it. The quality of the floor determines the comfort and long-term durability of the entire structure. Screed is used to level a floor, to warm it, to eliminate cracks, or to prepare it before applying the main layer, which can be completely different (cork, parquet, linoleum, tiles, etc.). The most important point to consider when screeding concrete is to take your time when working.

The use of the auxiliary measuring devices contributes significantly to monitor the drying process and to get an accurate result instead of an approximate evaluation. Even if the screed appears dry enough on the surface, it doesn’t mean that the entire layer is ready to be covered! Various factors influence the drying process of the screed: the method of applying the screed, the material used, the time of year, the temperature and humidity in the room, the thickness of the screed layer or the number of layers (if necessary). Depending on what material is used for the screed and what material is laid on top of it, a so-called finishing floor, the optimal value for the residual moisture in the screed can vary. A concrete screed takes a long time to dry. Therefore, it should always be noted that this process must not be intentionally accelerated or slowed down. The generation of very dry room air accelerates the evaporation of moisture, which leads to cracks in the screed. On the other hand, excessive humidity leads to additional wetness of the screed and a considerable increase in drying time. That is why it is important to create favorable conditions, because this is the only way to ensure correct drying of the screed (no drafts, no direct sunlight, no frost in the room, etc.). The most common problems that arise due to insufficient drying of the screed are: odor nuisance, bubbles and waves on floor coverings, ”rising” of the covering material, waves, loss of strength, mold growth, the floor covering loses its adhesion to the screed, color change of the covering material, etc. A moisture meter , which works with the calcium carbide method, makes it much easier to control the residual moisture in the screed. Depending on the type of screed, the most suitable measuring method can be selected. The calcium carbide method helps, for example, to precisely determine the residual moisture at any depth. On the other hand, this method takes more time and determines moisture by weight. Handling an electronic measuring device is very simple, which allows any user to carry out many measurements in a very short time, especially if the layer thickness is not very large. Regardless of the method chosen, the main point to note is that a correct determination of the moisture level in the screed is very important, which is why a double check should be carried out with every screed application.