Design and Construction Method of Improving the Crack Resistance of Mass Concrete Floor

Abstract

The invention provides a construction method to strengthen crack resistance of a large-volume concrete baseplate, which effectively controls generation of cracks of the large-volume concrete baseplate during a construction period. The construction method comprises pouring of a concrete cushion, layout of a slide layer, pouring of anti-crack concrete, conservation at a concrete plasticity stage and conservation at a concrete hardening stage, wherein the slide layer is constituted of two layers of plastic thin films between which a mixed fine material layer is sandwiched; a 7d restrained expansion rate in water conservation of the anti-crack concrete is not less than 0.02%, and a 28 d restrained expansion rate in the water conservation is not less than 0.03%; during the conservation at the concrete plasticity stage, a moisture evaporation inhibitor is sprayed after the pouring of the anti-crack concrete, plastering construction is started for one time after drying of the concrete surface, the moisture evaporation inhibitor is sprayed once again after the plastering, and the second time of plastering polishing processing is carried out 2 h before final setting; and during the conservation at the concrete hardening stage, a conservation agent is sprayed after hardening of the anti-crack concrete, the concrete is then covered by a layer of polystyrene board for thermal-preservation conservation, and a conservation period is not be less than 14 days.

Description

technical field [0001] The invention relates to a design and construction method for foundation floor concrete, in particular to a design and construction method for improving the crack resistance of a large-volume concrete floor. Background technique [0002] At present, with the rapid development of the economy and the advancement of science and technology, construction projects are developing towards super-large and multi-functional. Oversized concrete slab foundations are increasing day by day. Due to the ultra-long and ultra-thick floor foundation, and the different geological stress conditions of the foundation, the technical difficulty of concrete crack control is increasing. The crack problem of the floor concrete structure is a fairly common quality problem. How to suppress the cracking risk of large-volume bottom slab concrete is a topic that many engineers and technicians are currently working hard to discuss. [0003] Super long and super large (that is, the le...

AI Technical Summary

Problems solved by technology

In order to avoid cracking, the current main measures for controlling cracks in mass concrete floor are: using layered and segmented pouring to reduce the concrete center temperature, and setting post-casting belts to prevent structural shrinkage and cracking. It brings some troubles and has the following deficiencies: (1) In the design, it is generally required that the post-cast belt can only be poured after 60 days of construction on both sides of the structure, prolonging the total construction period, slow template turnover, and increasing construction management costs; (2) The post-cast belt is placed on both sides of the concrete After pouring, it needs to be protected. Before the pouring belt is poured, the basement is always in a state of water leakage. The post-casting belt is filled with various sewage and construction waste. The cleaning work is difficult, and the soil must be dewatered for a long time. There are long-term safety hazards of anti-floating stability; (3) It is difficult to clean the construction joints on both sides of the post-casting belt, and the time interval between new and old concrete pouring is too long, so it is difficult to guarantee the bonding strength at the construction joints, and cold construction joints are easy to occur, resulting in weak impermeability links; ⑷There is a contradiction between the retention of the post-casting belt and the prestressed construction. When the prestressed tendons cross the post-casting belt, the prestress must wait for the post-casting belt to be closed and reach strength before it can be stretched, which seriously affects the construction progress

For example, in terms of structural design: unreasonable design of the sliding layer, weak sliding capacity, and large foundation constraints, resulting in an increased risk of cracking of the floor concrete constraints; in terms of raw materials and mix ratios: unreasonable mix ratios of concrete, increased hydration temperature, and large internal and external temperature differences , Significant shrinkage and deformation, leading to increased risk of concrete shrinkage and cracking; construction process: concrete performance during pouring, unreasonable maintenance plan, etc., resulting in increased risk of cracking on the concrete surface of the bottom slab

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