Preventing cracking in reinforced concrete structures
The crack detection and crack handling were expertly dissected in the scientific conference on "cracking and crack inspection in reinforced concrete structures in construction works" on November 5 in Ho Chi Minh City.
According to Assoc.Prof. Dr. Tran Chung - Vice Chairman of Vietnam Association of Structural Engineering and Construction Technology: Proactively eliminating errors at the design stage, improving the capacity of knowledge and ethics of professionals is a method of prevention. Effective prevention brings sustainable development to the country
The causes of cracking
Sustainable construction is one of the most important requirements in construction works, but during the construction and use of many constructions, cracks cause nuisance to investors, construction units and other authorities. This affects the reputation, time and slow progress of the project. According to Prof. Dr. Huynh Chanh Thien - Senior Advisor of Construction Inspection Corporation of Saigon, said the cause of the damage caused to create cracks in construction works due to: Physical impact, mechanical impact and other impacts. other effects. Therefore, the ability to damage develops over time, according to the load and according to the degradation of bearing capacity, construction rigidity. The formation of cracks is the most damaged form due to many causes. For example, in terms of mechanics, the main cause of the crack is from the disadvantage of concrete with too low compressive strength (about 5% of compressive strength of concrete). Also in the process of hydration cement will create deformation from the shrinkage block, forming physical cracking phenomenon. The shrinkage process occurs unevenly, can be clearly distinguished before and after the end of the mounting process. “The shrinkage of the first concrete is due to the effect of gradation, because the higher the grading rate, the greater the difference between the shrinkage level on the outside and inside the section. Next is the effect of cement on shrinkage. If increasing the amount of cement, the shrinkage of the cement mortar and concrete increases. In addition, physical cracks also appear under the impact of climatic factors, hot and humid environments such as dehydration, deformation or elastic processes ... these processes are related to each other and affect. to the process of forming the initial structure of the concrete as well as the strength of the concrete later, ”Prof. Dr. Thien emphasized.
In addition to the above causes of cracking, Assoc.Prof. Dr. Tran Chung - Vice President of Vietnam Association of Structural Engineering and Construction Technology said that the cause of cracked reinforced concrete was from design. “In structural calculation, the designer carries out design calculations according to current standards in order to design a project that ensures rigidity and stability and ensures economic requirements. However, when applying the calculation standards, there are also causes leading to structural damage such as using calculation standards, using unreliable input survey data, design methods, and solutions. structural measures, designation of unsuitable design materials ... works with causes from the design are often at great risk when the damage causes serious consequences on people and properties. Therefore, the requirement to perfect the management of design quality is a legitimate requirement of society for the Vietnamese construction engineering team, ”Assoc. Prof. Dr. Tran Chuong said.
Assoc.Prof.Dr. Nguyen Van Hiep - Ho Chi Minh City University of Technology said experience in dealing with cracks is a must have preventive solution from the beginning. According to Assoc. Prof. Dr. Nguyen Van Hiep, in order to do that, the investor forces the design consultant to prepare technical instructions and this document must ensure the content and in accordance with the regulations. In fact, up to now, many design consultants have submitted technical instructions to investors from a pre-set file, the same for all projects. This is one of the factors causing inadequacies after the construction works and use.
If the cracks have been identified after the cause, there must be a solution to overcome the factors affecting the bearing capacity, in order to fix the cracks, in the physical crack, it can be carried out right after concrete. has reached the construction intensity. “All cracks (mechanical and physical) if the cause is identified and the defect is corrected, the repair of cracks is usually long-term and does not significantly affect the life of the building. . If the crack is less than 0.1mm (hard to see by the naked eye), use a cutter or chisel to remove the concrete along the crack in the V-groove and re-plaster with an additive mortar to achieve the same concrete strength. If the crack is larger than 0.1mm, it is recommended to inject Epoxy glue (pump by cylinder) deep penetrating type, low pressure according to advanced products in the world. However, strict procedures need to be followed. In case the crack is larger than 0.5mm, high-pressure Epoxy mortar must be sprayed. In all cases, it is necessary to remove the plastering mortar, clean the surface before proceeding to handle the cracks, ”said Prof. Dr. Nguyen Van Hiep.
Facing increasingly complicated developments of the Covid-19 epidemic, the socio-economic situation of the country, including Thai Nguyen, was strongly impacted.
On April 7, 2020 at the Ministry of Construction, Deputy Minister of Construction Nguyen Van Sinh, member of the Steering Committee of Project 896, attended the meeting to review the implementation of the Project 2019.