Build Daily

Building Materials

August 12, 2017 18:08

Cold weld concreting - minimize the scars of our buildings

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device construction joints during concreting - why is it done?

known that the fresh concrete should be the entire volume set formwork fences.But their stacking layers can be produced, and it is allowed to fill the next layer until the previous setting.In this case, the strength of the concrete monolith is not deteriorated.

But if stacking of layers was conducted with such intervals that the previous layer has had time to harden, then the next casting already underway to meet a number of requirements.Their purpose is to reduce the negative influence on the working seam strength between the solid structure and the liquid new old concretes.

Only at first glance it seems as if nothing special in these works there.In fact, they represent a complex process that requires knowledge of the technology and compliance with the stringent requirements of its implementation.The formation of cold joints, also known as workers, construction joints or concrete, is a real headache.This is understandable, given their negative impact on durability.

Worker concreting seam may be formed as a result of the causes of organizational, technological, constructive.Obviously, you can move the working hours, eliminate downtime required to replicate the technique and increase the carrying capacity of forests.But completely eliminate the formation of very hard concrete joints, at least in terms of accepted practices create complex designs connects individual blocks.

Worker concreting seam - the rules for obtaining a quality seam

already mentioned rules set: in the case of works intermittently over two hours of their being renewed after the previous layer-quarter strength (1.5 MPa) in order to maintain its structure.This certainly clears hardened surfaces of cement films mechanically (metal brush, milling, sandblasting), with the obligatory washing with water jet and air jet drying space such treatment.

necessary to take into account the opinion of practitioners, claiming that the device is working joints during concreting, even after five hours give a stronger joint than the same set of surface treatment fully cured concrete.Typically, the mixture poured concrete layers and horizontally.

In the case of a large mass of used machinery concrete step, when the laying of a new layer of no more than the previous setting.The general rule of admissibility of the working place is its joint device in cross-section, not critical to the strength of the structure, but the inadmissibility of the seams in relevant areas with the largest shear force.

For complex codes, bunker, bridge and arch designs, and other similar structures, devices and places sutures do strictly specified in the work projects.For the elements of the seams are arranged in agreement with the designers.The rules set, for example, columns, the ability to weld on top of the support base, the lower or upper boundary runs between beams or columns, etc.

for walls and columns are horizontal seams considering appearance of the building.Not allowed layer arrangement angle: vertical seams necessarily use restrictors at minimum length.To determine the exact locations of joints used project documents and recommendations of the rules and regulations of the carrying and enclosing constructions (SNIP 3.03.01-87).

cold seam concreting - how to increase the reliability of construction with seams

If necessary, increase the time setting retarders special curing layers are used, called plasticizers.Slower setting using sulfite-yeast mash is permissible only in the summer and is not recommended in other seasons.

methods and practical ways of increasing the strength of the seam between the bundles of fibers, other than those described above mandatory mechanical treatments, there are many.For example, the use of horizontal or a stepped joint.This method is recommended when casting small items of tape designs.

For greater adhesion primer formulations are used on hardened concrete.A similar result is achieved by adhesive or bitumen compositions.

one obvious task - to increase joint strength.For the concrete work of high-rise housing, in agreement with the technical supervision authorities, the process can be applied seam concreting, involving the use of special methods of reinforcement with one or more grids (frame of reinforcement, fine-mesh, etc.), bilateral dowels their galvanized metal, etc..P.

Also discussed sutures, project of concrete structures can be provided for the organization of various types of joints.If temperature fluctuations linear dimensions are changed in order to avoid critical stress in concrete structures, arranged thermal expansion joints (compression, expansion, warpage).

These joints are located across the (expansion and contraction), along (warping) of the elements and cut on hardened concrete using diamond disc.Stitches after pre filled by special elastic expansion joints on various bases (mastic, rubber cords, polymers) capable of easily deformed.

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