1.Overview of diseases of concrete hydraulic buildings
The frequent diseases of concrete hydraulic buildings include cracks, freezing up, wear and weathering, rust and corrosion, etc. Different diseases have their performance characteristics.
Concrete cracks. In water conservancy projects will be barrage dams, bridge sections, gates, culverts and other concrete construction, these concrete buildings are prone to cracks, so that the building because of cracks and began to leak and freeze-thaw, a serious threat to the safety performance of water conservancy engineering buildings. Cracks are especially serious in the barrage dam body, gate bottom plate and retaining wall, etc.
Freeze-thaw damage. When the soil is in a water-filled state, the alternating effect of the forgiving and thawing cycle, in the cold climate, so that the soil and water contact and lead to freeze-thaw damage to the building. Usually, in the “three norths” area often occur in the concrete hydraulic buildings of freezing and thawing, and the damage of the concrete in the freezing and thawing cycle will occur freezing and cracking and surface spalling phenomenon, resulting in the elastic modulus of the concrete, strength and other mechanical properties reduced, thus endangering the safety of the building structure.
Wear and weathering. In the cold region of the river, dams and other water conservancy buildings, will often be subject to the collision of ice, or by the long-term wash of water, in such a collision, wash and other external forces for a long time, so that the water conservancy building long-term contact with the water part of the spalling, resulting in the concrete structure of the reinforcement exposed or concrete grinding into the honeycomb, reducing the life of the concrete structure, most concrete dams, gates Most concrete dams, locks, side piers, etc., the life of only l0 years, part of the tube can only be 5 to 6 years to maintain the repair.
Erosion, rust and corrosion. Once the cracks in the concrete structures of water conservancy projects, in the water and air wetting, so that the internal reinforcement of the concrete rust condition, coupled with industrial drainage in the water body will aggravate the erosion of concrete buildings, resulting in safety accidents of hydraulic buildings.
2.Concrete disease analysis
First, physical analysis. Concrete hydraulic structures in the long-term by external forces such as ice floating collision, mud flow abrasion, water impact scouring, etc., will make the concrete table spalling phenomenon, manifested as aggregate off, the formation of concrete surface cavities. Secondly, under the action of load external force, in the process of long-term temperature constantly changing, make the concrete building produce cracks, sink, fracture and other deformation.
Secondly, chemical analysis. For the concrete building of water conservancy project itself, three kinds of erosion phenomena will be produced.
① dissolution erosion, in the production of soil mix, its raw material calcium hydroxide contained in silicate cement has a large solubility, when in the flow of water, will make the calcium hydroxide in the soil mix slowly dissolve, and then reduce the concentration of lime in the soil mix, and the hydrated calcium silicate and hydrated calcium aluminate in the soil mix must be in a certain concentration of calcium hydroxide solution to maintain stable performance, once the calcium hydroxide decreases and disappears, it makes the hydrated calcium silicate and hydrated calcium aluminate start to decompose, which reduces the strength of the mix and cement mortar, and further destroys the mix structure under the invasion of external erosion medium.
② ion exchange erosion, the acid in the cement mix is in water for a long time, it occurs ionization, which makes it produce hydroxide ion exchange reaction to generate water and salt. Salt is easily carried away by water, which increases the voids within the concrete, reducing the strength of the mix, and the body of water then intensifies the erosion of the mix; in addition, non-soluble substances are produced during the chemical exchange reaction, which also does not cause volume expansion, but will soften the cement paste, and also increases the voids within the mix, increasing the penetration of water into the mix. In the water body inside, the cement soil will also occur in another chemical reaction, that is, ionization of magnesium ions, which then ionized with cement stone, producing a very small solubility of hydroxide ions, accelerate the decomposition of cement stone, and magnesium hydroxide itself is soft, no cementing properties, will soften the cement paste
③ sulfate erosion, the sulfate in the mix will react with the hydration products in the cement to produce calcium alumina and gypsum, after the wetting began to swell, the internal stress of the mix to destroy, if encounter and then meet sulfate and magnesium ions, but also to accelerate the destructive effect, because magnesium sulfate and hydrated calcium aluminate reaction to produce gypsum, aluminum glue, magnesium hydroxide, they all carry great destructive. In the concrete mix with voids, its reinforcement will produce rust, which is also damage to the concrete another factor.
3.Maintenance management of concrete hydraulic buildings
Take the concrete to construct the building, which is the mix itself has a good dense, seepage resistance, frost resistance and other properties, its strength is high, very durable. If the production of concrete mix is designed and experimented in advance, it can produce excellent performance of concrete mix, which can effectively prevent the aging of concrete mix and prolong the life of concrete structures. Strengthening the maintenance and management of concrete mix structures can be done by a combination of prevention and treatment.
First of all, we should strictly select the raw materials for making concrete mixes, and the best choice of cement is silicate cement, and ensure that all kinds of raw materials for concrete mixes meet the relevant standards and requirements.
Secondly, before making the mix, the best ratio of raw materials should be studied, and the test of strength and other properties should be passed before making a lot of mixes.
Finally, in the construction process, the construction plan should be selected scientifically and reasonably to ensure that the concrete construction can meet the relevant requirements, which can improve the quality of the concrete construction. In the specific construction process, it is necessary to do a good job of construction technology management and construction quality supervision, and timely check the construction quality against the design requirements to achieve standardized construction, which can effectively ensure the quality of the concrete mixing project.
For the anti-freezing performance of concrete, you can make the concrete mix, moderately reduce the amount of water and water-cement ratio, so that the concrete mix construction moisture, reduce free water, which can effectively reduce the chemical reaction about the destructive, reduce the free water brought about by the destruction of the structural void of the concrete mix. Appropriate addition of aerator, which produces micro-fine bubbles can block the water penetration channel in the mix. In addition, the bubbles have deformation function, which can effectively alleviate the freeze-thaw expansion. During the construction, it is necessary to flatten and vibrate the concrete mix evenly and densely to strengthen the performance of the mix.
Once the surface of the concrete structure is damaged, repair measures should be taken immediately. Usually, practical repair mortars include cement mortar and pre-shrunk mortar, while the repair methods include slurry spray repair method and vacuum operation repair method.
In the event of cracks, it is necessary to take the groove chiseling inlay method and the spray slurry repair method to coat the concrete table and then sticky patch. And the cracks need to be filled by grouting inside, and there are two kinds of grouting, cement and chemical. For crack leakage, it is necessary to analyze the cause of cracks, the degree of affected and the amount of leakage and its dispersion and concentration, and then choose to take buried pipe or borehole infiltration method to repair, and can also take filling method to repair. Culvert (pipe) crack leakage, need to paste epoxy adhesive in rubber, and then grouting, reinforcement of culvert foundation or structural reinforcement. Scattered seepage type concentrated seepage phenomenon should choose grouting measures and combine with surface coating and repairing impermeable layer to carry out comprehensive treatment. For water-stop structural joints leakage, asphalt patching method, chemical grouting method or building water-stop facilities again are needed to deal with it.
For concrete hydraulic buildings in the beginning of construction to the use of the period, will involve a variety of construction and management and maintenance work, and maintenance costs are relatively high, the worse the use of time, the higher the repair and reinforcement costs required, must strengthen the preliminary construction design and construction management, control the quality of concrete construction, can effectively reduce the repair and reinforcement costs later. In addition, it is also necessary to regularly and timely inspection and management of hydraulic buildings, in order to timely maintenance for the relevant problems.