(1) The ice, snow and garbage on the formwork and reinforcement should be removed before the concrete is poured, especially at the junction of old and new concrete (such as the junction of beams and columns), but no water should be flushed.
(2) Before pouring, the concrete should be prepared to cover with insulation materials, such as plastic film, colored cloth, cotton felt and grass curtain, etc., and do the corresponding anti-freezing insulation measures. And take the necessary wind-blocking, closure measures to improve the insulation effect.
(3) shall not be concrete pouring on the permafrost layer, before pouring, must try to warm up so that the permafrost thaw. When the concrete hew, should preheat the old hew, and strengthen the insulation after pouring to prevent the hew from freezing.
(4) If the slump of concrete is too small to meet the construction requirements, it can be adjusted by using admixtures under the guidance of the technical personnel of the concrete company, and it is strictly forbidden to adjust the slump of concrete by adding water.
The reason why the concrete mix gradually sets and hardens after being poured until the final strength is obtained is the result of the hydration of cement. And the speed of cement hydration, in addition to the concrete itself and the composition of materials and ratio, mainly with the temperature changes.
When the temperature rises, the hydration is accelerated, the strength growth liquid faster; and when the temperature drops to 0 ℃, part of the water present in the concrete begins to freeze, gradually from the liquid phase (water) into the solid phase (ice). At this time, the water involved in the hydration of cement is reduced. As a result, hydration slows down and strength growth is correspondingly slower. Temperature continues to fall, when the presence of water in the concrete completely into ice, that is, completely liquid phase into solid phase, cement hydration basically stopped, at this time the strength is not growing.
After the water becomes ice, the volume increases by about 9%, while generating an expansion stress of about 2500 kg/cm2. This stress value is often greater than the initial strength value formed inside the cement stone, so that the concrete receives different degrees of damage (i.e., early freezing damage) and reduce the strength.
We have been in this Concrete Pump Pipe line many years, about concrete pump pipe , there is four kinds of concrete pump pipes , including single wall seamless pipe, harden pipe, twin wall pipe and welded pipe !
(1)About the concrete pump seamless pipe , usually we have 20# material pipe , st52 seamless pipe , which material is 16Mn, or Q235 seamless pipe. Usually this kind of single seamless pipe service life is 15000cbm-20000cbm, which is used on the stationary pump .
(2)About the harden pipe , inner wall through heat treatment, the hardness is more higher than the formal seamless pipe . Service life is 25000cbm-30000cbm.
(3)About the twin wall pipe , inner wall pipe material is very important, material is 65Mn, and the outer pipe material is 20# , service life is 50000cbm-60000cbm.
(4).About the concrete pump welding pipe, which is not formal for exporting, except customer requirement. There is one welding line internal of the pipe, which is used on the low pressure stationary pump.Service life is usually 10000cbm.
The information is provided by the concrete pump pipe supplier.
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