The extensive use and promo of business concrete, significantly enhanced the building and construction speed and constructing quality, and promote the vigorous development of industrial concrete innovation.
Nevertheless, the resulting early breaking of industrial concrete, but up until the end has actually not been an efficient option to the quality of construction tasks in recent years is the focus of debate and problems, has actually triggered excellent issue to the market and society.
Initially, the reason for fractures in business concrete is naturally complex and diverse
The absence of understanding of the use of industrial soil and inappropriate upkeep, is the main factor for the prevalence of fractures in commercial concrete, this paper on the splitting of business concrete and upkeep issues to go over the views.
Second, the value of the beginning of the upkeep time to control the early shrinkage of commercial concrete
1, for normal concrete not mixed with water-reducing representative, early shrinking is small, early sprinkler upkeep is generally to make the cement totally hydrated to make sure the development of concrete strength, for that reason, China's concrete structure building quality acceptance requirements, the beginning of concrete upkeep time is within 12 hours after putting.
2, for a great deal of contemporary business concrete blended with water-reducing representative, it is proved by relevant tests that the shrinking increases greatly within 8 hours after initial setting, and in the real task, the most a great deal of large volume of floor fractures mainly appear within a few hours after preliminary setting of concrete, therefore, a great grasp of the beginning treating time is the crucial to manage the early shrinking of industrial concrete cracks.
If we continue to wait 12 hours after pouring and then spray upkeep, we will lose the very best time to manage early shrinking fractures, and in terms of early shrinking crack control, we will lose any function. Many of the current building and construction system is still accustomed to the conventional building upkeep experience, not according to the qualities of the present commercial concrete, that is, in the concrete just preliminary set (prior to the surface water loss), on the adoption of sensible upkeep procedures, effectively reduce shrinkage, lower splitting.
Third, The need for prompt and sufficient wetting of commercial concrete maintenance
1, The so-called prompt curing is mainly: to curing the concrete before the surface does not lose water.
In the actual operation, it is difficult to master prompt curing, however it ought to be figured out according to the efficiency of the concrete mix and the climate, and so on (Usually, damp treating must be performed when the concrete is first set), and if water loss has happened on the surface throughout treating, the problems triggered by water loss must be dealt with prior to curing to guarantee the impact of treating
2, the so-called full treating, generally: to ensure that in the entire specific upkeep duration, concrete can not lose water, no water loss is the complete curing; Otherwise, water loss is insufficient treating.
Concrete curing the more appropriate, then the existence of concrete problems is less; concrete treating is not adequate, then the existence of concrete defects more. Many of the present building unit of the concrete maintenance are in the putting of the next day after the start of watering, 2-5 times a day, so that the upkeep is neither timely nor adequate, resulting in a lot of fractures.
Fourth, wet curing 7-day period, the impact of the various stages of industrial concrete curing.
1, according to the test information and production experience, the 7d strength of business concrete is probably 28d strength (65% ~ 85%), so the requirements requires damp curing 7 days is reasonable, it is best to keep 7 days without water loss.
According to our production experience, in these 7 days, the earlier the time, the much easier it is for the concrete to lose water, the most likely to form defects, the more important it is to prevent water loss.
2, 3-d strength has to do with 28d strength (45% ~ 60%), so the very first 3 days to prevent water loss is especially important. If the first 3 days do not lose water, then continue to water and moisturize to 7 days, from the project in fact, the results are great.
3, the first day is really crucial, if the very first day too much water loss, the defects caused by the future might be difficult to fix.
4, we discovered that some sites, the first day do not pay attention to maintenance, the next day before the start of water preservation, upkeep is over, the board still has a great deal of fractures, the analysis of its causes: since the very first day has actually been a fracture, which means that the first day of the non-maintenance of the fairly coarse pores have actually been formed, it is tough to recover.
7 days of wet upkeep, the secret is the first 3 days, the most important is the very first day, so we have to make sure that the first day is not water loss, no matter what kind of maintenance we use.
Fifth, The value of secondary concrete power troweling.
1 、 Smoothing in one go. Instantly smooth the surface with a wood trowel, called "main smoothing".
2 、 2nd smoothing. When smoothed, if not immediately after the concrete curing procedures, then to the very first set of concrete, must be smoothed at least once again, this time not only smoothed, however also "pressure", the concrete surface smoothed and compacted (concrete internal secretion channels, capillary channels, wipe pressure, eliminate.), called "secondary wiping". This is called "secondary cleaning".
The primary role of secondary cleaning has 3 points.
( 1) Remove surface area flaws, internal secretory channels (i.e., capillary channels) and early plastic cracks in concrete.
( 2) Improve the density of the concrete surface layer.
( 3) Improve the surface compaction, slow down the migration and evaporation of water in concrete, and enhance the anti-cracking ability of concrete.
3 、 From the very first smoothing to the 2nd smoothing, it is the process of gradual preliminary setting of concrete.
4 、 The development of fractures. In an extended period of time, as long as the relative humidity of the environment is listed below 100%, the concrete surface area will lose water, the development of internal flaws - capillary channels. These defects are not removed, when it comes to continued water loss on the concrete surface, the pore will be more deepened, the more expansion of fractures, splitting, severe cases will trigger penetrating cracks, resulting in flooring leak.
5, we found that in the wet treating is appropriate and not timely (such as traditional damp treating), only a smoothing without secondary erasure, concrete cracking will be really serious.
With secondary troweling, the degree of cracking is significantly reduced. Unless the application of instant curing, so that the concrete surface area can not create water loss problems, otherwise the secondary wiping process is required.
6, the conventional trowel manual trowelling. In the secondary cleaning process, now frequently utilized to trowel manual wiping, not just inefficient, not strong enough, when the problem from the surface area and inside the development of deeper, it will be tough to remove
.
7, Disc type
Concrete trowel machine: the best secondary cleaning utilizing disc type power trowel, the elimination of surface area flaws (and concrete internal secretion channels) and compacted surface area than the trowel, the role of much better, high efficiency.
There are two types of power trowel: stroll behind power trowel and
concrete ride on trowel machine, that makes the secondary trowel more efficient and more precise. Better end up the ground leveling.
8, After the secondary cleaning, the concrete should be instantly treated with sufficient dampness to avoid the concrete losing water once again, only in this way, can ensure the early hydration of concrete, enhance the quality of hardened concrete, and lay an early quality foundation for the improvement of concrete resilience.
Sixth, early membrane curing is extremely essential.
Practice has shown that using membrane treating after concrete putting is a easy and effective way of curing. Especially in the large northern areas, heat, wind speed, dry air, water loss quickly, using membrane curing, you can quickly seal the concrete moisture in the interior, and in the membrane and the concrete surface to form a long-lasting damp curing environment, after the final set concrete surface area temperature cracks, survival cool and neat.
The membrane treating building needs to focus on the timeliness, and should finish the membrane lamination prior to the preliminary setting of concrete. Film and concrete surface ought to be carefully bonded without bubbles, no gap in between the membrane and the membrane cover, no large area overlap, and do an excellent task of later surface watering upkeep, keep the membrane surface moist.
In the element of film coating upkeep, Weinan Hongji Da did a great task in the building of Purple Emperor House and other jobs, and attained the detailed movie finish upkeep of concrete putting, no structural concrete cracking phenomenon, which made sure the quality and safety of concrete structure and beautiful image.
To summarize, as long as the building and construction is carried out strictly according to the building and construction specification, the concrete surface area is secondary smoothed, and enough and prompt membrane moisture conservation is carried out, the fractures of concrete can be minimized to a big extent, so that the concrete cracks can be effectively controlled.
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