This also requires the concrete to maintain good cohesion in the process of mixing, pumping, pouring and vibration to resist delamination and segregation.
The author believes that the basic conditions for the qualification of concrete mixture are that each component can maintain uniform distribution (i.e.
The author believes that the vast majority of workers are willing not to add water.
Starting from the “interests” of workers, adding water without authorization is mainly for two purposes: reducing labor intensity and shortening pouring time.
First, many mixing plants themselves give a large surplus coefficient to the concrete strength value, and second, they do not have to be responsible for the insufficient strength.
When migrant workers add water, it is easy to cause visible bleeding, layered segregation and other phenomena.
Is it the concrete itself? Or do migrant workers add water? Or the ponding on the site itself? Since my work, the author has been closely connected with the reality of the construction site and maintained good communication with migrant workers.
(3) Reduce the particle size of stone, which can be used for many purposes 25mm Stones below.
Starting from the mix proportion, we can start from the following aspects: (1) appropriately increase the pump slump, but control its water retention and uniformity.
homogeneity) in concrete and basically no visible bleeding (i.e.
Many times, they reluctantly acquiesce to this phenomenon because of the fruitless communication for many times.
There is such a persistent disease on the construction site: almost everyone knows that adding water to the concrete in the tank truck at will has many hazards, but the phenomenon of adding water is repeated.
No matter whether the concrete fluidity is good or poor, workers should add water to facilitate construction operation, which is a serious lack of management of the construction unit.
At present, the evaluation basis of concrete quality is mainly strength and working performance, which is an important direct factor causing the phenomenon of migrant workers adding water.
(4) Properly increasing the sand rate can reduce the viscosity.
The quality of concrete does not depend on the slump (or fluidity) or the amount of water used, but on whether the water can be maintained.
It is not excluded here that some construction sites have irresponsible habit of adding water.
The large slump loss is an important factor causing migrant workers to add water..
If the concrete supplied by the concrete mixing plant has large fluidity, but the workability is good and the water can be kept, and there is basically no visible bleeding after vibration, why not have a large slump? (2) The amount of coarse aggregate in modern concrete is greatly reduced compared with that in the past, and the stone changes from extrusion state to suspension state in concrete.
However, the water adding phenomenon in most construction sites is mainly due to the low fluidity of concrete into the pump and high labor intensity.
The basic characteristics of this water adding phenomenon are: generally, the water adding situation in the construction at night is more serious than that in the daytime, and those without supervision are more serious than those supervised.
The author believes that in addition to the role of skeleton, the more important role of aggregate in modern concrete is to disperse stress.
In practical engineering, there are many components constructed with large fluidity concrete without crack or less crack.
Some scholars believe that reducing slump as much as possible and using less high fluidity concrete is an important principle to do a good job in mix proportion at present.
Therefore, the use of strength, working performance and slump value as the main methods to evaluate the quality of concrete has great limitations.
(5) Control the slump loss of concrete.
Coarse and fine aggregates need to be evenly distributed in mortar and slurry respectively, and the concrete should have appropriate slurry bone ratio and mortar sand ratio to avoid shrinkage cracks caused by excessive concentration of shrinkage stress.
With the development of admixture technology, it is necessary to change some misunderstandings.
In the final analysis, the construction unit believes that the problem of concrete is mainly the responsibility of the mixing plant, but there is a lack of supervision and restriction on migrant workers; At the same time, concrete companies have no direct interest relationship with workers.
It is not necessarily directly related to the impermeability and crack resistance of concrete, because with the development of superplasticizer, the adjustable space of concrete fluidity is very large under the same water consumption and water binder ratio.
To borrow a sentence from a concrete benevolence of a mixing plant: as long as your material is good enough and can fight, workers generally do not add water, and they are too lazy to climb up and down (tank car).
Communication is very important.
good water retention) after vibration.
However, the author believes that if the slump (or fluidity) is large, the concrete is not necessarily bad.
(1) The supervisor or designer at the construction site generally requires that the slump of concrete provided by the mixing plant should not be too large, which is an important indirect factor causing migrant workers to add water.
They even call the migrant workers on the construction site “Uncle”, which is a bad phenomenon.
At this time, the construction unit will actively analyze the causes of this phenomenon.
Workers believe that adding a small amount of water to the tank truck can increase its fluidity and will not have a great impact on the strength.
It is more appropriate to judge the quality of concrete by the state of workability.
(2) Rational use of fly ash and appropriate increase of fly ash can enhance the thixotropy and stability of concrete.
