Definitions

Definitions   Floor Definitions Smoothing Compound Thickness 0-5mm. Can be feather-edged down to 0mm. Only for manual application. Either self-smoothing or paste consistency. Levelling Compound Thickness 2-30 mm. Can be self-levelling, fluid or non-fluid consistency. Screeding Compound Thickness 5-50mm. Can be self-levelling, fluid or non-fluid consistency. Base Screed Screed that is covered by a smoothing or levelling compound. Low-alkali Levelling Compound Levelling compound that has a binder content of more than 50% aluminous cement and/or gypsum. Normal drying Requires external drying before floor covering is applied Self-drying Compound with such a high binder content that significant internal chemical drying occurs even after moisture is released. Rapid drying Installation of floor covering after 24 hours (at +20ºC and 50% RH). Ultra rapid drying Installation of floor covering after 1 hour (at +20ºC and 50% RH). Fast setting Compound ready to take pedestrian traffic 1 hour after application (at +20ºC). Fast hardening Compound hard enough to take pedestrian traffic within 5 hours. Light industry Non-compact wheel loads. Mainly pedestrian traffic. Heavy-duty industry Compact wheel loads, impact and stationary loads, chemical reaction. Underlayment Thin layer applied to a base or screed in order to provide a smooth surface to receive floor-covering. Wearing Surface (overlayment) End use without floor covering. Self-smoothing Ability of fresh screed material to naturally form a smooth surface. Self-levelling   Capacity of fresh screed material to spread out naturally to form a flat horizontal surface. Humidity Measures Moisture ratio (u)* The ratio between the weight of free water and the weight of the dry material (kg/kg,% by weight). Moisture content (w)* The ratio between the weight of free water and the volume of the material (kg/m³). Relative humidity (RH)* The ratio between the water vapour concentration in the air voids of the material and the saturation vapour concentration (kg/m³/kg/m³,%). RHCRIT Critical humidity level: The limit of RH under, which a material may be continuously exposed and still retain acceptable functional performance. Carbide method (CM) Measures the moisture content (see above). Normally performed by the CM tester working according to the carbide method while using the reaction of calcium carbide in water. Acetylene gas is formed that causes an increase of pressure in the steel cylinder during this reaction. * Moisture ratio and moisture content are statistical concepts, while RH indicates the ability of moisture to move around in a material   Moisture equilibrium If a completely dry material is placed in air with a certain RH, the moist air will penetrate into the pores of the material. Water will bind to the walls of the pores. After some time, equilibrium will be established between the humidity level in the air of the pores and that of the air outside. The water vapour concentration will be the same in the pores and in the air outside. Equilibrium is also established between the humidity level in the air of the pores and the amount of water absorbed by the pore walls. The relationship between the moisture content in the material and RH in the environment (and in the material) is given by an equilibrium humidity curve with the basic shape shown in the Drying section. This is normally known as the sorption curve. Moisture transportation Convective Transportation This refers to the fact that moisture is transported by air movements. For example, if there is a leakage of air between a warm and a cold area, moisture is carried by the air currents. This involves a condensation risk since cold air cannot hold as much moisture as warm air. Convective transportation gives relatively quick moisture transportation in building structures. Capillary transportation This refers to the fact that moisture is transported in a material's capillaries (fine interconnecting air channels). This takes place, for example, in slabs laid on the ground in older cellars. Capillary transportation is a relatively fast means of moisture transportation in building structures. Vapour Transportation This involves the transportation of water molecules from a place with high vapour concentration to a place with lower vapour concentration. This can also be expressed as transportation from a material with high RH to a material with lower RH. Vapour transportation is slow compared with convective transportation and capillary transportation. Equivalent Measurement Depth Equivalent Measurement Depth Equivalent measurement depth is the situation in, which the depth from the surface of a concrete or levelling compound to the moisture level is the same as that in the surface after application of flooring and redistribution of the moisture.