When the concrete mixture is poured, it should be vibrated with depth vibrators in order to remove all air bubbles from the mixture and to obtain a homogeneous concrete. When vibrating, the concrete becomes more plastic and penetrates into all unfilled areas of the formwork. To compact the concrete mixture, the tip of the vibrator working part should be immersed in the previously placed layer. The vibrator should be moved at a distance of 30-50 cm, while the vibrating zones should overlap one another, the vibrating time is from 0.5 to 2 minutes, depending on the mobility of the concrete mixture or convenient compaction. When vibrating, it is necessary to avoid contact of the vibrator with reinforcement bars and their supports, as well as with formwork elements. After all areas have been vibrated and the concrete mixture has been thoroughly compacted, the vibrating should be stopped; overzealousness may lead to delamination. When coarse aggregate particles sink into the concrete and cement milk is released along the formwork, it is possible to stop vibrating.
Pouring the concrete mixture into the formwork is not the end of concrete work, as previously written poured concrete requires further care, to acquire the required strength in a certain period of time. Increase in the strength of concrete at the initial stages is fast and concrete prepared on Portland cement already on 7 – 10 days after pouring, gaining 60-70% of its design strength, which comes on 28 days. After that, the rate of strength gain slows down. Under optimal conditions of hardening concrete is best to gain strength at t=20 C and humidity of at least 80%) and it is especially important to maintain such conditions during the first 3-5 days. For more information about concrete care and its necessity, please see “Why Concrete Care?”.
Uncracking
To disassembly work can begin after the concrete has gained 70-80% of its design strength, under normal curing conditions, this occurs on the 7th day. But this is for general monolithic works including massive structures, in private construction, in private construction, in compliance with the technology of concreting and subsequent care for the laid concrete, depending on the massiveness of the structure, decompression can be carried out on 4-5 days.
Formwork removal, disassembling
The formwork should be carefully dismantled in order to avoid the destruction of the formwork and concrete structures. The surfaces of the formwork, which will still be used, should be cleaned with metal brushes and scrapers from the remains of concrete mixture and lubricated with a special emulsion. In case of large sinks and spalls on the concrete surface, it can be cleaned and grouted with cement-sand mortar. Remove the formed concrete surface buildup with a trowel.
