Mechanical properties and acoustic behaviour of screed Essay

Mechanical properties and acoustic behaviour of screed - Essay Example The topping thus made is a layer of high strength concrete, with better mechanical properties than other finishing matrial used ordinarily on the surface bases........(1) However, due to the poor surface finishes available at sites, it is advisable to use screed adequately while making correct leveling for the laying of screed to get the required smooth finish. Proper tools like trowels are used for this purpose. The general guidelines for laying a screed layer provide that there should not be any deviation of more than 3mm over a length of 3 meters, to get the smooth and level floor of good quality. The figure shows the deviation curve for the screed layer on a concrete surface over a 3-meter length, with datum level as reference point...........(2) There are mainly two types of screeds, bonded and monolithic screeds. The difference lies in their application. While bonded screed is applied to a hardened concrete floor surface, monolithic screed is applied at the time of laying the concrete flooring itself. This type of screed is applicable only on strong and hardened concrete that has a characteristic strength of more than 20MPa, as the bonding of adhesive is not possible for screed with weak concrete. Moreover, the screed layer cannot fill any cracks on the base floor and therefore the crack will show up over a period. The base concrete surface should be smooth and level to allow a screed layer of approximately 25 mm. thickness, being in the range of 15 to 40 mm.. The preparation of base concrete should be such that it is hardened uniformly, free of oil or dirt, If there is a presence of any earlier screed layers, then same need to be removed by scrapping allover, as the cleaning at edges or pecking at intervals will not be sufficient. The surface should be vacuum cleaned with high air pressure to free it of all dust particles. For this purpose, a mixture of sand and cement should be