Construction is a kind of production and creation activity with a systematic strong, long operation cycle, multiple projects, labor intensive and environmental impact. Therefore, the factors that determine the quality of construction projects are relatively complex.
I. the significance of quality management of construction projects.
Construction engineering is a special product that provides human life and production space, and the reliability of engineering quality directly relates to the safety of people's life or property. Construction quality is the core of whether the project can fulfill its special mission.
In recent years, the governments at all levels to zero tolerance under the general requirements of the engineering quality accident, serious rite of unit of each responsibility main body, earnestly implement the standardization of construction management measures, the construction of major quality accident nearly disappeared. However, some defects in quality have seriously affected the function of building use, causing disputes between the construction party and the owner. How to eliminate or reduce the quality defects that affect the use of functions has become an urgent task for the project management supervisor and the fundamental requirement for continuous improvement of construction quality.
Ii. Methods and elements of project quality management.
1. Construction quality management method.
The quality of the work determines the quality of the finished product. Therefore, the efficient and reasonable management system and the comprehensive and rigorous implementation attitude are the bridge of the construction enterprise casting fine works.
To apply the idea of total quality management, under the guidance of the quality policy of the top management of the enterprise or organization, the whole process, the whole process, the whole staff participation. The basic principle of quality management is a PDCA cycle, i.e., planning, implementation, inspection and disposal. The general goal of the project is to pass all the procedures at once. In each process, the principle of dynamic control is applied to realize the design of the construction organization in advance, ensuring the quality of the process in the process, and then evaluating and rectifying the process results.
2. Factors affecting the construction quality.
The quality awareness and activity ability of the decision-maker, manager and operator; There are also the qualifications of the main body of responsibility for the project, which is essentially the problem of human quality and ability. Only qualified personnel can manage and produce qualified products.
(2) the technology factors, mainly through the survey and design, construction technology, materials, equipment, test and inspection technologies such as the organization and management, optimize the technical solution, give play to the role of technology for quality assurance. Construction technology, mainly for proposed project drawing test, using the quality acceptance specification and relevant standard atlas quality technical disclosure, the key procedure and difficulties of engineering quality control points of the preset, dynamic tracking check to ensure that the quality control points are always under control.
The management factors, organizational structure, management system and operation mechanism directly affect the realization of the goal of the construction project. The tasks and objectives of the project are decomposed, distributed and delegated properly, which also have an important impact on the project quality objectives. Project management through the post, team, professional subcontractors, each working procedure involving materials, machinery and so on carries on the effective control, to establish three inspection system and the process model is made, efficient collaboration, material, machine operation, is likely to create qualified finished products.
Environmental factors, such as geology, hydrology and meteorology, etc. Lighting, ventilation and safety facilities in the construction site; Multi-unit, multi-professional cross construction organization and coordination management environment. The successful completion of project quality objectives must recognize and grasp these objective environments.
(5) social factors, have the consciousness of material suppliers, mechanical equipment where tenants, degree of specification of construction project transaction, the concept of industry regulations, advisory services, to build a clean government, etc. On the quality of the project.
3. The harm of the quality of construction engineering.
With the continuous development of new technology, new materials and new technology of construction engineering, the construction project also gradually presents the characteristics of oversize, super high level and large span. Construction quality common fault is characterized by: engineering pile fracture, water seepage, the basement post-cast strip shear wall contraction crack, high and low layer joint structure cracks, concrete standard block strength is insufficient, bar spacing deviation is too large, steel welding try to pull a unqualified, thickness deviation is too big, plus or minus shear wall vertical deviation is too big, overall surface cracking of concrete, masonry and concrete place shrinkage crack, masonry ledge of eight crack, empty drum craze, plastering wall wear plate nozzle around oozing, lightning protection grounding resistance on the high side, outside wall, foundation pit and back of inside and outside soil subsidence, etc.
The above questions are divided into two categories:
1, directly related to basic body structure using safe function, can lead to significant losses of lives and property of the accident, must be in construction process to eliminate or rework reconstruction, or according to relevant laws and regulations are strictly prohibited.
2. If it is a local unqualified, it must be eliminated in the construction process or modified according to the standard, and it can be put into use after being tested. If there is a direct impact on the owner's inability to use it, it must be repaired in accordance with the building engineering quality warranty regulations. Rework or reinforcement requires additional quality costs and time, and demolition is the biggest failure of management and investment.
4. Cause and control of quality common diseases.
The following is a brief analysis of several quality common diseases.
1. Water seepage in the basement after pouring.
In terms of the drawings, the construction unit must be carried out according to the approved construction drawing, and accurately grasp the waterproofing and additional layer quality, the post-pouring belt retention practice, the sealing time and the technical requirements.
After a long period of time before pouring the pouring belt, it is necessary to remove the rust and drainage of the steel bar in the rear pouring belt, and remove the debris when pouring, which is higher than the concrete on both sides, and the compaction is compacted and strengthened. It is not suitable to carry freight vehicles in 14 days after pouring the roof.
Quality control of commercial concrete. Including concrete strength, workability, slump, aggregate gradation, silt content, proportion, the varieties of cement, fineness, strength, setting time, soundness, alkali content, date of production, inspection reports, quality of admixture, water cement ratio, etc.
After that, water seepage treatment. During the rainy season, the underground water seeps through the cracks in the concrete to the surface or wall, affecting the normal use of the garage. The water seepage point is found in the treatment, and the seepage channel is blocked.
2. The strength of the concrete marking test block is insufficient.
The quality and strength control measures must be effective. Commonly used additive have pumping agent, water reducing agent, retarder, early strength agent, anti-permeability agent, antifreeze, expansion agent, etc., the same mixing between batches of admixture, compatibility between cement and admixture to do test.
The control of the concrete from stirring and transporting to the mold time. The concrete must enter the template before the initial coagulation (the cement slurry begins to lose its plasticity) and complete the casting vibration. The mold height should not be more than 2 meters, so as to avoid concrete segregation. Vibrating compaction determines the quality of concrete pouring. The wall column beam board had better not leave construction seam, the strength grade of wall column and beam board is not at the same time, through organizing measure to avoid to produce cold seam.
The curing of concrete. Generally, the concrete before the final set to start natural curing liquid (water, thin film, keeping in good health), P, P.O, p. mixing of concrete curing 7 days, P.F, P.P, P.C mixing or retarding the requirements of the permeability of concrete curing 14 days. While maintaining the floor, the maintenance of the wall column is the most important.
In view of some unreasonable progress node requirements of the developer, the construction period of high-rise residential structure is about 4 ~ 5 days. When the floor after the positioning of pay-off, followed by the wall column reinforcement, templates and scaffolds of returnable, hard to avoid in the process of tower crane unloading floor vibration, and beam slab concrete just result in strength and is very low, will result in the crack of the floor vibration influence concrete strength development.
The strength of the test block is not enough. In the field, the strength of the physical component is tested, and the sampling quantity is considered to be increased appropriately. When the physical detection strength is still insufficient, the original design unit must be asked to carry out the security review; When the review fails to meet the requirements of the specification, it is necessary to issue a structural reinforcement plan, which can be checked and accepted after the test is qualified.
3. Crack of masonry and concrete members.
The shrinkage ratio is caused by the elastic modulus of different materials between the masonry and the bottom of the beam, the masonry and the concrete wall columns. The usual practice is to set aside 170 ~ 200mm from the bottom of the masonry, and after the strength of the masonry is no longer shrunk for 7 days, then the closure is called "rolling brick". The masonry can also be set aside 30mm from the bottom of the beam, and then the masonry will be filled with micro expansion mortar after the masonry is no longer shrunk.
Before the wall is brushed, the anti-crack wire mesh is posted at the joints of concrete and masonry materials, with a height of 300 ~ 400mm, and ensure that the mesh is not moved after the bottom gray. In the treatment of the cracks in the bottom of the beam, the decoration layer material is removed to the masonry base layer by layer, and the gap is filled with non-shrinkage grouting material (or special high strength glue), and then the decoration layer is restored layer by layer.
In view of the importance of quality management of construction engineering, this paper analyzes the hazards and prevention and treatment of quality common diseases, and puts forward some methods and measures for quality management and prevention and control. Construction quality is the life and property safety and vital interests of the owner, the construction enterprise must comprehensive participation and dynamic quality management, the whole process of every working procedure to ensure that each material qualified, can build the products comply with the design to use a function, and then carry out the mission of the era have entrusted to the heavier than mount tai.