1. INTRODUCTION
-The process of making a building comprises the phases of design, implementation and use.
-The occurrence of failures in one or more of these stages causes defects that can compromise safety and durability of the project.
-The concrete requires some care in its preparation to optimize the lifetime and performance. The study involves proper execution trace, in addition to strength, handling and proper healing, periodic preventive maintenance and protection against aggressive agents.
2. MAJOR MEDICAL CONDITIONS OF CONCRETE STRUCTURES
Structural-strain
Corrosion of reinforcement
Leaching-hydrated compounds
Lack of quality and thickness of coatings
Fault-geometric elements of reinforced concrete
Segregation of concrete-
-Cracks
3. Structural Deformation
Second-Sabatine (1998), the structures performed in the 70's will had a mean of four meters, and will the current average is seven feet between supports, as a consequence have higher deformation structures.
3.1 Excessive deformation in the Balance Sheet
4. Reinforcement corrosion
-Corrosion of reinforcement is an electrochemical process that needs to occur simultaneous presence of moisture and oxygen.
-The permeability of concrete due to high water / cement ratio and inadequate dosing, and failure in the development of structural design and / or execution of work, when not guarantee the standard reinforcement cover, are the main causes of reinforcement corrosion.
4.1 Corrosion of Armor Base of the Pillar
High-density armor with insufficient concrete cover causing general corrosion and expansion of the section of armor with subsequent rupture of the stirrups. (Jefferson Maia Lee)
4.3 Slab reinforcement corrosion in
- Slab run without a minimum of coatings for protection of the armor that coincided with the joints of the formwork causing general corrosion and expansion of the section of armor.(Jose Pacha RS)
4.4 Corrosion of Armor Beams
5. Leaching of hydrated compounds
-A leaching is the extraction or dissolution action that the compounds of hydrated cement paste can suffer when in contact with water, especially pure or acidic.
-The leaching of calcium hydroxide, with the consequent formation of insoluble calcium carbonate are responsible for the appearance of efflorescence characterized by white deposits on the surface of the concrete.
5.1 Leaching of hydrated compounds
6. Lack of quality and thickness of coatings
-NBR 6118:2003 states that the durability of structures is highly dependent on the quality and thickness of concrete overlay of armor.
-Helene (1993) points out that the actual quality of concrete surface coatings and protection also depend on the suitability of the mold, the mold release additive and, especially, the proper cure of this surface.
7. Irregularities of the geometric elements of reinforced concrete
-Modifications are specified in relation to the structural design and / or molds, the geometry of the elements, which may occur at the level of flatness, square or changes in the dimensions of the pieces of concrete.
-The wood quality and care in the execution of the formwork and shoring may prevent irregularities of geometric elements in reinforced concrete.
7.1 plumb in Pilar
7.2 Beam Embarrigamento
8. Segregation of Concrete
It's the segregation of fresh concrete so that its distribution is no longer uniform compaction compromising essential to achieve the potential maximum strength and durability.
Main Causes:
High-density armor;
-Inadequate conditions of transport, launching and compacting concrete;
-Consistency inadequate.
- Nests of concrete in the abutment against the beam, then
filled with ceramic bricks. (Jose Pacha RS)
- Concrete runs with high water / cement, resulting in high porosity of concrete and shrinkage cracks.
9. Cracks
-The cracks are a major pathological problems in relation to buildings, mostly of concrete.They can manifest themselves from the concrete to back after the same year.
-According to NBR 6118:2003, the openings of the cracks should not exceed:
A0, 2 mm exhibits very strong in aggressive environment (industrial spills and tidal);
A0, 3 mm for parts exposed to moderate and strong aggressive environment (urban, marine and industrial);
A0, 4mm exhibits weak in aggressive environment (rural and submerged).
-Cracks are inevitable phenomena themselves and the concrete and can manifest itself in each of the three phases of his life:
9.2 Causes of Cracks
Transactions-thermal;
Transactions-hygroscopic;
-Overload;
-Excessive deformation of the structure;
-Repression of the foundation;
-Changes of chemical materials (such as corrosion of reinforcement);
-Fire on the structure.
9.4 Settlement Measurements of Cracks Caused by Foundations
-In general, the settlements generate cracks in the pillars of the variable aperture beams attached to them, and these larger openings at the top of the beams. Cracks resulting from these settlements depend on the magnitude.
The repression-cracking will be even more significant when the armors are deficient or even when they are poorly positioned in the element.
9.4 Settlement Measurements of Cracks Caused by Foundations
9.5 Cracks Caused by Corrosion of Armor
-The cracks caused by corrosion of reinforcement tend to appear over the bars in the oxidation process.
-The use of appropriate coatings and a concrete compact impede the process of reinforcement corrosion, and therefore alleviate (or prevent) the problem of cracking caused by oxidation of the armor.
9.6 Cracks due to structural loads
9.6.1) - Draw
-The cracks caused by tensile loads are generally orthogonal to the direction of the effort and go through the entire section. The concrete material is very susceptible to this type of cleft, because the tensile strength of this material is very small.
9.6.2) - Compression
-Cracks caused by compression stresses are generally parallel to the direction of effort.When the concrete is very heterogeneous, cracks can cut up the second acute angles. The cracks due to compressive stress are made visible efforts to lower the break, and continuously increase.
9.6.3) - Flexion
They begin in-board pulled the pieces and move forward toward the neutral line. This type of crack opening is variable: they are more open section of the board pulled open and diminish as they arrive near the neutral line.
9.6.4) - Shear Force
-Cracks caused by shear are generally inclined (between 30 ° and 45 °, approximately), run throughout the piece, and are located near the supports of the elements (regions of high shear force).
9.7 Excessive Cracking States
10. Conclusion
-Most of the pathologies in buildings occur in consequence of failure to execute and the lack of an effective quality control.
-For best results it is important that manufacturers invest in training workers, providing better working conditions and also the improvement of professionals, especially in the areas of pathology.
Authors;
Andreia Dias de Oliveira
Marina De Sá Santos Time
Other posts;
