Chem M250 is a special hydraulic binder, which, when mixed with clean aggregates and water, has the properties to harden in a few hours and to dry perfectly at whatever thickness within 24 hours. Because of these characteristics and the very high mechanical strength, Chem M250 is the ideal binder for screeds onto which resilient, textile, wood, ceramic or stone floorings must be installed within 24 hours.
Field of Application
· Preparation of screeds set to light foot traffic after 2-3 hours and totally dry after 24 hours.
· Preparation of screeds ready to receive ceramic tiles and natural stone after only 3-4 hours.
· Patching and repairing screeds in areas subject to continuous traffic.
· Preparation of screeds incorporating under floor heating systems.
COVERAGE / CONSUMPTION
Preparation of the substrate
All substrates are suitable as long as they are not subject to rising damp, in which case install a suitable vapour barrier. For non floating screeds from 10 to 35 mm, which have therefore to be anchored, the substrate must be dry, free from cracks, resistant to compressive and tensile strength, free from dust, loose materials, paints, wax, oil, traces of gypsum.
Preparing the product
Chem M250 must be mixed carefully and quickly, with water and graded aggregates 0-8 mm in diameter or with Gravel 0-8, for a maximum of 3-4 minutes, in a mixer or batcher. The mix must be spread and leveled in the shortest time possible and not more than 30 minutes after mixing. Special care must be taken with the quantity of water that must be enough to form a cohesive mass so that tamping gives a flat surface without a cement film. Chem M250 aggregates and water can be mixed:
· in a drum mixer;
· in an ordinary concrete mixer;
· in a screw mixer;
· manually, with a shovel.
The Chem M250 mix can be placed using an automatic pressure pump. In any case it is absolutely necessary to strictly follow the instructions regarding the dosage and mixing time.
Applying the product
The Chem M250 mix is placed onto a substrate like any ordinary concrete. A polyethylene sheet must be laid in order to create an easily flowing layer between the Chem M250 screed and the existing substrate and to prevent any rising damp. If the Chem M250 screed is crossed by pipes, it is necessary to lay a light metal mesh over the screed as a reinforcement and ensure a minimum thickness of 2.5 cm.
Chem M250 screeds are prepared using the same methods as those for ordinary cement screeds: preparing leveling strips, spreading the mix and accurately compacting it and then tamping to obtain a better surface finish. Around the perimeter of the area and around the columns etc., it is recommended to insert a 1 cm thick anti-fracture material. If work is interrupted for more than 1 hour, it is necessary to cut the screed perpendicularly and insert pieces of rod into the edge of the screed. They should be inserted 20-30 cm apart to guarantee perfect bonding and to avoid cracks and differing levels and prepare a suitable bonding slurry.