BS/EN 13892-9-2018 pdf download.Methods of test for screed materials Part 9 : Dimensional stability.
6 Curling profile apparatus
The curling profile apparatus, shown in Figure 1, features a stainless steel, distortion-resistant mould 50 mm in depth and 100 mm in width with an effective specimen length of 1 000 mm.
At one end of the mould, the specimen is restrained horizontally and vertically by two stainless steel dowels cast within the specimen whilst the opposite end is unrestrained and the specimen connected to a length variation sensor. The two horizontal dowels, comprising 10 mm thick stainless steel bar, are located within the mould, perpendicularly to its length and vertically central within the depth of the mould:
— the first dowel is fixed at a horizontal distance of 17 mm from the restrained end of the mould, this support is attached to the mould;
— the second dowel is located at a horizontal distance of 260 mm from the restrained end of the mould and extends through holes in the mould on each side, where it rests and can slide freely upon flat stainless steel anvils. Horizontal freedom of movement  ± 4 mm exists in the axis of length measurement.
At the unrestrained end of the mould, a stainless steel striker plate is attached to the specimen by means of a stainless steel tang which protrudes into the specimen. The striker plate is unrestrained and transmits horizontal movement directly to the length variation sensor.
NOTE 1 A vertical deflection sensor can be installed to monitor vertical movement at the unrestrained end of the specimen, which represents curling of this specimen.
NOTE 2 Spacers are initially placed between the striker plate and the end of the mould; these are removed after the mould has been filled and directly before the start of measurement.
The length variation sensor shall measure change in length over a distance of not less than 5 mm with an accuracy of < 0,001 mm.
The mould is lined with a 2 mm thick polychloroprene sheet to separate the specimen from the mould and in order to prevent obstruction to free movement even if the specimen should swell.
7 Procedure
7.1 General
The dimensional stability (i.e. shrinkage and swelling) of screed materials depends on climatic conditions. Therefore, the entire test procedure shall be carried out in the standard laboratory climate, temperature (23 ± 2)°C, relative humidity (50 ± 5)%.
7.2 Preparation of specimen
The screed material shall be prepared in accordance with EN 13892-1.
Within 5 minutes of the mixing process being completed, the consistency of the screed material shall be determined according to EN 13454-2.
The filling of the mould shall he done without delay.
The fresh screed material shall be carefully compacted into the curling profile apparatus mould, which
has first been lined with a thin (<0,2 mm) polyethylene film.
The mould shall be filled to a depth of 50 mm unless it is determined that a lesser depth is necessary.
If the intended application for the screed material (according to manufacturer’s information) does not permit a specimen depth of 50 mm, the test may be carried out using the greatest possible depth. Use smaller dowels if the depth of the screed material is smaller than 20 mm. When specimens less than 50 mm in depth are tested, it shall be ensured that the two stainless steel support bars are located centrally In relation to the specimen’s depth.
In order that a single material characteristic is tested, no change of curing or other treatment (e.g. covering the surface) is permitted.
7.3 Length change
The measurement of change in length shall commence directly after the mould is filled and at the moment the horizontal length sensor is positioned and spacers removed from the striker plate. The change in length is thereafter continuously monitored and recorded at predetermined time intervals.
The predetermined time intervals between length measurements may be decided within permitted limits, providing that the relationship between length change measurements and time may be recorded with sufficient accuracy and comparable during evaluation. Initially and until the local maximum length has been reached, the time interval should be 10 mm. following which the time interval may be increased to a period of not more than 6 h.
The length variation curve shall record local extremes (local minimum Lmin and local maximum Lmax).
Length variation shall be recorded until the end of length change Lend. This is the condition of equilibrium moisture content having been reached. The end of length change Lend is determined as being when change of length, monitored over a period of 5 days, differs by less than 3 % from the obtained shrinkage value.
NOTE The test to determine shrinkage and swelling can last for a long period of time. For cementitious and magnesite screed materials, the test will typically last 8 weeks. For calcium sulfate screed materials, the test will typically last 11 weeks.
Immediately after the end of length change measurement the moisture content of the screed material test specimen shall be determined by drying a sample (>300 g total cross section) until the weight remains constant. Constant weight is defined as when the loss of weight is less than 0,1 % between 2 measurements over a 24 h period. The drying temperature of cementitious screed material and magnesite screed material is (105 ± 2)°C and for calcium sulfate screed material (40 ± 2)°C. Different temperatures may be given by the manufacturer. The weight shall be measured with an accuracy of≤ 0,05g.BS/EN 13892-9-2018 pdf download.