Ar an tógáil suíomh % 2c sé is a an- coitianta rud go clúdach agus uisce an poured coincréit . An meicníocht agus feidhm de a a chlúdach agus uisce caomhnú tá anailís in ordú chun a fháil réidh de roinnt míthuiscintí faoi sé.
Ceann de the misunderstandings:
Tar éis an coincréit is poured% 2c sé ní mór a bheith clúdaithe agus uisce chun freastal an riachtanas de coinneáil an coincréit dromchla in a fliuch stát laistigh de a tréimhse áirithe de am am ag an céanna am céanna 2c in ordú chun cosc a chur an tapa galú de an curing uisce % 2c 2c sé sé a bheith clúdaithe le ábhair mar plaisteach scannán % 2c ach Chomh maith leis sin áirítear fairsing agus as cuimse ábhar. In summary, there are two main points: one is to keep the concrete in a sufficient wet state within a certain period of time to meet the needs of cement hydration The second is ensure that the concrete can maintain a suitable maximum temperature, a suitable internal and external temperature difference, and a suitable temperature difference between the surface and the ambient atmosphere under different ambient temperature conditions, chomh maith mar an cuí fuaraithe ráta agus téamh ráta.
Míthuiscint 2: Is é an is déanaí tús am le haghaidh coincréit uisce agus curing 12 uair an chloig tar éis stealladh.
An "Quality Acceptance Specification for Concrete Structure Engineering" (anseo feasta dá dtagraítear to as "Quality Specification") stipulates that the concrete should be covered and moisturized within 12 hours after pouring. Mar sin féin% 2c go leor tógáil oibrithe míthuiscint go an déanaí tús am le haghaidh uisce agus curing tar éis coincréit pour is 12 uair an chloig ina dhiaidh sin % 2c is go say % 2c mar fada mar an uisce agus curing tá déanta amach roimh 12 uair an chloig tar éis coincréit stealladh % 2c é beidh freastal ar an sonraíocht riachtanais . Dá bhrí sin% 2c ar an tógáil suíomh % 2c teicneoirí tá go minic bhíonn urging cothabháil agus uisce % 2c ach roinnt daoine beidh rá go sé é ach cúpla uair an chloig tar éis an coincréit is poured % 2c agus é tá sé fós i bhfad ar shiúl ó 12 uair an chloig ! Ní in a déan deifir
Mar gheall ar go an leanúnach dul chun cinn agus forbairt de stroighin agus coincréit teicneolaíocht % 2c go háirithe i déanaí blianta % 2c an leathan iarratas de ard-fheidhmíocht coincréit % 2c luath-neart coincréite agus réidh-measctha coincréite % 2c an coincréit neart grád agus stroighin neart grád a úsáidtear tá réasúnta ard an teocht dífhoirmiú % 2c tirim crapadh dífhoirmiú agus féin-crapadh dífhoirmiú de an coincréit tá mór mar gheall ar na cúiseanna den sórt sin ard luath neart % 2c beag uisce-stroighin cóimheas% 2c etc.% 2c agus coincréit scoilteadh ó am am go am go am % 2c agus an déanach uisce agus curing am de coincréit thiocfaidh chun bheith luath scoilteadh . One an tábhachtach cúiseanna le haghaidh seo ní mór arouse an aird de tógála oibrithe .
Go leor blianta ó shin % 2c plaisteach coincréit le ard sreabhacht bhí go minic bhí ar an tógáil suíomh . An stealladh toirt ní mór % 2c an neart an neart grád de coincréit agus stroighin bhí íseal % 2c an méid de stroighin beag % 2c an céim luath hiodráitiú ní ard 2c agus ard tirim crapadh . Tá níl féin-crapadh . In seo cás % 2c sé d'fhéadfadh sé a bheith iomchuí a cheangal den sórt sin plaisteach coincréit a a bheith watered agus leigheas laistigh de 12 uair an chloig tar éis stealladh . Mar sin féin% 2c le haghaidh nua-aimseartha coincréite % 2c déanach uisce agus curing beidh cúis scoilteadh agus damáiste an poitéinseal cáilíocht . a thabhairt díobhálach éifeachtaí.
An tríú míthuiscint: Tá an níos faide an coincréit watered agus cured % 2c an níos fearr.
The "Quality Specification" stipulates that for concrete mixed with Portland cement, ordinary Portland cement or slag Portland cement, the watering and curing time shall not be less than 7 days. The required concrete shall not be less than 14d. It should be pointed out here that what the specification stipulates is only the minimum time for watering and maintenance, but does not give the optimal duration and maximum time for watering and maintenance. However, the longer the watering and curing time, the higher the degree of hydration of the cement, and the greater the irreversible shrinkage of the cement. If the cement particles are fully hydrated, the resulting cement gel will not only increase the strength of the concrete, but will also produce Large shrinkage can cause concrete cracking in severe cases. Like the volume stabilization effect of aggregates in concrete, a certain amount of unhydrated cement particles or other inert substances are required in cement stones to stabilize the volume. Therefore, the watering and curing time is not as long as possible. It is obviously wrong to blindly extend the watering and maintenance time as "enhanced maintenance". The progress and development of modern cement and concrete technology requires "just in time" watering and maintenance.
Tástálacha tá cruthaithe go an crapadh de coincréit ag éagsúla aois is go bunúsach an céanna le haghaidh caighdeán curing de 7 lá agus caighdeán de 14 laethanta % 2c mar léirithe in Tábla 1% 2c ach ró fada curing ní féidir a thuilleadh a laghdú an crapadh . uisce curing% 2c mar gheall ar an méadú an méadú de an coincréit go a áirithe méid. Fadtéarmach fliuch curing ní féidir go héifeachtach laghdú an triomú crapadh de coincréite % 2c agus cé sé is féidir moill an tús am de crapadh % 2c an éifeacht íosta .
As we all know, early cracking of concrete is a new problem brought about by the progress and development of cement and concrete technology, and autogenous shrinkage and temperature shrinkage are the main reasons for early cracking of high-performance concrete, high-strength concrete and high-early-strength concrete.
The size of the concrete self-shrinkage depends on the self-drying degree of the cement stone, the elastic modulus and the creep coefficient of the cement stone. In the early stage after concrete pouring, especially the first 24 hours after initial setting, its elastic modulus is low and its creep coefficient is large. Therefore, the degree of self-drying becomes the main factor determining self-shrinkage. When the concrete is initially set, the wet curing of its surface can make the curing water and the moisture in the capillary pores of the concrete connect as a whole, so as to supply the cementitious material inside the concrete for hydration. The further hydration of the cementitious material promotes the refinement of the capillary pores. When the resistance of the capillary wall exceeds the surface tension of the water and cannot continue to migrate to the interior of the concrete, the supply of water stops. It can be seen that the water replenishment effect of early watering and curing can well inhibit the early shrinkage of concrete.
The self-shrinkage of concrete has already started from its initial setting, and the early development is very fast, and most of it can be completed within 24 hours, and then rapidly decays, and its value can reach (0.025~0.050) × 10-3, and also with water glue increases with decreasing ratio and increases with increasing temperature. At the same time, with the gradual increase of concrete strength, the ultimate tensile strain also drops sharply from 4.0×10-3 2 hours after forming, and can drop to 0.04×10-3 in 6~12 hours, reaching the risk period of concrete cracking. If according to the provisions of the "Quality Standards" and the requirements of traditional plastic concrete, the latest start time within 12 hours after pouring is mistakenly used to start watering and curing. The time has obviously lagged behind the dangerous period of concrete cracking. The latest time to start watering and curing is no longer suitable for the curing requirements of modern concrete. Many people mistakenly believe that the watering and curing of concrete can be started at any time within 12 hours after the concrete is poured. The plasticity of human beings is very large, and this kind of understanding and practice is obviously wrong.
Más rud é an luath ard neart de coincréit tá mar an inmheánach cúis de a luath scoilteadh % 2c ansin an seachtrach uisce athshlánú agus briseadh de uisce athshlánú tar éis an an uisce an an t-uisce an luath scoilteadh de coincréit . Dá bhrí sin, it is very necessary to greatly advance the time of concrete watering and curing, so that the outwardly evaporated water on the concrete surface can be replenished in time, so as to achieve "early and timely" watering and curing. Specifically speaking, after the concrete has been poured and the initial setting begins, watering and curing should be done "as soon as possible" as as long as the surface de an coincréit ní a bheith go saorga damáiste . Leordhóthanach uisce soláthar coinníollacha chun a sheachaint an comhpháirteach gníomh de plaisteach crapadh % 2c autogenus crapadh agus tirim crapadh de coincréit.
Míthuiscint cúig: Is é an uisce agus cothabháil de coincréit is fearr pour le uisce % 2c mar sin go an uisce is féidir a bheith go hiomlán athlíonta.
The covering after concrete pouring is to prevent the rapid evaporation of curing water to save water; the second is to prevent the rapid loss of cement hydration heat during the cooling stage, so as to ensure a suitable temperature gradient on the concrete section. In order to save covering materials, some people do not cover the concrete and pour it with high-pressure water. This not only wastes water, but also easily damages the concrete surface. The most important thing is that the pressure water flows through the concrete surface and quickly takes away its heat. , leading to a sudden drop in the surface temperature of the concrete. If it is in the peak period of concrete hydration heat, if the temperature difference between the curing water and the concrete surface is large, it may be caused by the sudden drop in the temperature of the concrete, which will cause the temperature difference between the inside and outside of the concrete and the temperature difference between the concrete surface and the environment to be too large. "Thermal shock" will cause the concrete surface to crack; at the same time, it must be remembered that maintenance and watering should not be intermittent, and repeated "thermal shock" may aggravate the cracking of the concrete. The appropriate watering and maintenance method should be small water flooding.
Is é an tosaigh stealladh teocht de coincréit an tábhachtach cuid de an uasmhéid teocht de coincréit . fuarú an coincréit in a plaisteach state ní amháin laghdú an uasmhéid teocht % 2c ach freisin laghdú an scoilteadh teocht de coincréit dá réir sin. Dá bhrí sin% 2c fuarú an coincréit in a plaisteach state is one de an éifeachtach modhanna chun cosc a chur coincréit scoilteadh.
Míthuiscint seacht: Insliú clúdach tosaíonn nuair uisce agus clúdach, I don't know when to start.
Achoimre an thuas fadhbanna % 2c sé is féidir a bheith le feiceáil go roimh an coincréit sroicheann an uasmhéid teocht de stroighin hiodráitiú % 2c sé sé ba chóir a bheith i an teas dissipation céim in in ordú a a níos ísle níos ísle uasmhéid teocht agus teocht níos ísle =níos ísle teocht =níos ísle a a a bheith chun cinn .
Ceann de na críocha de chur i bhfeidhm teirmeach insliú in an coincréit fuarú céim is chun laghdú an teas caillteanas taobh istigh an coincréit % 2c mar mar a a laghdú an teocht grádán ar an an alt an dara cuspóir is go moill an teas dissipation am de coincréite mar go go héifeachtach agus go hiomlán go moill an teas go hiomlán moill an teas agus a inmheánach teanntachta strus is féidir a bheith laghdaithe dá réir sin . Ag an céanna am % 2c mar gheall ar an méadú de coincréit aois 2c an teanntachta feidhmíocht de coincréit feabhsaíonn níos tapúla ná a comhbhrúite feidhmíocht % 2c cé acu is féidir freisin cosc agus laghdú coincréit scoilteadh.
Is é an teocht grádán de an coincréit dromchla amháin de na cúiseanna tábhachtacha srian na scoilteanna ar an coincréit dromchla . An ardú agus titim de an atmaisféarach timpeallacht teocht teocht tionchar an teocht gradient ar an inmheánach alt de an coincréite % 2c agus an steepness agus an steepness agus an teocht athrú idir an coincréit dromchla agus an atmaisféarach timpeallacht teocht. Éifeachtach clúdach de teirmeach insliú ábhair is féidir laghdú an Teocht grádán trasna a coincréit alt.
Chun suim suas% 2c sé is féidir a bheith le feiceáil go níl ábhar an comhthimpeallach teocht ard nó íseal % 2c go bhfuil go say % 2c no matter cibé acu an taobh amuigh aer teocht ard nó íseal in earrach % 2c fómhar agus geimhreadh % 2c an teirmeach insliú agus cothabháil de coincréit ni coincréit agus cothabháil de coincréit gan ach teocht drop, agus reduce the temperature difference between the inside and outside and the temperature difference between the concrete surface and the atmospheric environment. Dá bhrí sin, seo "outer insliú agus istigh mall drop" curing method can prevent agus reduce concrete cracking.
Botún No. 8: Gan de réir leis an sonrach iarbhír staid de an coincréite % 2c iarratas a dhéanamh na rialacha agus rialacháin meicniúil.
In order to prevent early cracks in concrete, it is usually achieved by controlling the technical indicators such as the maximum temperature of concrete, the temperature difference between inside and outside, the temperature difference between the surface and the environment, the heating rate and the cooling rate. The temperature difference with the ambient atmosphere should not be greater than 20 degree . However, there are some discrepancies in the previous specifications for the application in actual engineering. Some think that both should not be greater than 25 degree ; some think that they should not be greater than 30 degree ; The instantaneous temperature difference caused by water spraying and form removal should not exceed 15 degree . Engineering practice has proved that some projects have a temperature difference between the inside and outside of the concrete greater than 25 degree , but the structure has not cracked; while some projects have a temperature difference between the inside and outside of the concrete that is less than 20 degree , but the concrete has cracked. This can also explain the reason why the revised "Quality Standards" did not make rigid regulations on this.
At the same time, the control indicators of the daily cooling rate are also different. Some believe that the daily cooling rate should not exceed 3 degree , some believe that the daily cooling rate should not exceed 2 degree , and some even think that it should not exceed 1.5 degree .
An teacht chun cinn de difríochtaí idir an thuas-luaite teicniúil sonraí is iarbhír an- gnáth . Bíodh cé roinnt sonraí tá sonraithe ag an noirm ag na noirm ag na noirm ag ag an randamacht % 2c agus ilchineálacht de coincréit ábhar comhdhéanamh% 2c an ilchineálacht de coincréite % 2c agus an difríocht i tógáil cáilíocht % 2c é é ní iontas go bhfuil ann roinnt difríochtaí i an teicniúil sonraí shown. Éilíonn sé seo ar an láthair teicneoirí go Ag tabhairt teocht rialú isteach comaoin % 2c roinnt normatach forálacha ní féidir a bheith meicniúil chóipeáil.
