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RH Method

RH-method for Humidity Measurement - (Cement-based floor products)
 

Content
 
General
Principle
Choice of measurement points
Sampling
Maximum humidity in maxit floor products
 
General

In most countries knowledge of the behaviour of concrete as it dries is often applied to levelling products. However applying measurement procedures for concrete to cement-based levelling compound raises a number of problems.

Estimating the extended drying time of concrete treated with levelling compound at an equivalent depth is extremely difficult. This is because the humidity profile of reference samples covered with levelling compound differs markedly. When samples are covered with levelling compound they initially have a humidity profile with RH values nearer the surface higher than, or equal to, those at greater depths. Hence the equivalent depth becomes very hard to estimate, and moreover it will change over time (Abrahamsson A and Tammo K, 2003). In consequence, a measurement method more suitable for levelling compounds is proposed below.
 
Principle                                                                                                            To Top

By a sensor the relative humidity in the vicinity of the sample is measured. The measurement can be carried out either on-site in the drill core or in a test tube.
Choice of measurement points                                                                          To Top


The location and number of measurement points are matched to the needs of the task. It is important to record the thickness of the levelling compound at each measurement point. The thickness is determined by drilling through to the substrate with a small drill.

Thin constructions, t= 50mm (The methods below apply to both single-sided and double-sided drying of the levelling compound.)

  • Cores are drilled out over the total thickness of the levelling compound and crushed to equalise the humidity in the sample. The RH of the sample is determined. A core drill with a diameter of about 36mm should be used. Crushing should achieve a maximum particle size of 2mm.
  • With underfloor heating the sampling points are marked out with the application of levelling compound. With coverings on the substrate that form an air-gap (e.g. ventilation matting type Platon), care must be taken when drilling down to the covering. We recommend stopping drilling about 5mm above the covering. The core can be broken loose without damaging the covering.
Thick constructions, t=50-100mm (This method applies only to single-sided drying.)
  • Cores are drilled from the levelling compound at a measurement depth equivalent to 40% of the thickness of the levelling layer, ±5mm – see below. The extracted sample is crushed. RH is measured after moisture in the sample has been equalised. A core drill with a diameter of about 36mm should be used. The crushing should achieve a maximum particle size of 2mm.
Sampling                                                                                                            To Top

Method 1: Thicknes = 50mm
  1. Taking of samples should be documented on drawings and in quality control records.
  2. With coverings that form an air-gap, establish the thickness first by drilling with a smaller drill.
  3. With the core drill, drill down to the underside of the levelling compound. Drilling with a core drill of inside diameter about 36mm requires no addition of cooling water. Thicker layers should be drilled out in stages, extracting the core in several smaller sections.
  4. Place the samples in tightly closed glass jars or test tubes.
  5. In the laboratory, crush the sample core to a maximum particle size of about 2mm.
  6. Place the powder in the measurement receptacle. The sample should be conditioned for 1 day at the temperature specified for RH measurement.
  7. Read off the RH of the sample once the value in the measurement receptacle has stabilised.
Method 2: Thickness 50-100mm
  1. Taking of samples should be documented on drawings and in quality control records.
  2. Establish the thickness of the levelling compound by drilling with a smaller drill.
  3. With the core drill, drill down to 5mm above the equivalent measurement depth in the levelling compound. Knock out the extracted core and remove dust from the hole with a vacuum cleaner. Drilling with a core drill of inside diameter about 36mm requires no addition of cooling water.
  4. Drill a further 10mm, to 5mm below the equivalent depth.
  5. Release the core and place it in a tightly closed glass jar or test tube.
  6. In the laboratory, crush the sample core to a maximum particle size of about 2mm.
  7. Place the powder in the measurement receptacle. The sample should be conditioned for 1 day at the temperature specified for RH measurement.
  8. Read off the RH of the sample once the value in the measurement receptacle has stabilised.

Maximum humidity in maxit floor products for floor-coverings                            To Top

  Type of floor covering material

Cement-based
Floor product

  Tiles

95% RH

  Glued mats e.g. Linoleum or PVC

90% RH

  Glued parquet and laminates*

60% RH

 
* With special glue e.g. MS-polymer glues, the RH level can be 80%. Always look at the specification from the glue/adhesive producer.