FROM:Behind The Scenes Of A Precast Concrete Plant | Oldcastle Precast

Precast concrete structures are manufactured in a factory then delivered to a job site, ready to be installed. But, have you ever wondered how precast concrete products are made? In this video, you’ll get a behind-the-scenes look at one of our Oldcastle Infrastructure, a CRH Company, plants and gain first-hand experience on the manufacturing process.

Precast concrete structures are used in many types of construction and for many different purposes, including electrical and communication utilities, stormwater storage and conveyance, wastewater applications, bridges, building structures, and more.

There’s good reason for using precast concrete – it provides many benefits on a project, including quick and easy installation since there are no on-site forms to construct or waiting for the concrete to cure in the field, improving jobsite safety by decreasing the amount of time an excavation is open, and providing a high-quality, higher-strength product since it is produced in a controlled environment.

預製混凝土結構在工廠製造,然後運送到工地,準備安裝。但是,你有沒有想過如何製作預製混凝土產品?在這段視頻中,您將獲得我們的Oldcastle基礎設施(一家CRH公司)的幕後工作,並獲得製造過程的第一手經驗。

預製混凝土結構用於許多類型的建築和許多不同的目的,包括電氣和通信設施,雨水儲存和運輸,廢水應用,橋樑,建築結構等。

使用預製混凝土是有充分理由的 – 它為項目提供了許多好處,包括快速簡便的安裝,因為沒有現場表格來構建或等待混凝土在現場固化,通過減少現場的數量來提高工地安全性挖掘開放的時間,並提供高品質,高強度的產品,因為它是在受控環境中生產的。

Engineering & Design
The process starts with engineering. On each project, a design engineer or owner (such as a Department of Transportation, DOT) sets requirements for their precast components. When we get the drawings and requirements, every product is engineered in-house according to the design engineer and owner’s specifications.

The engineers ensure each precast structure has the appropriate steel reinforcement (rebar) and meets the structural requirements for the area in which it will be installed. Some important considerations include the soil type, whether the precast structure will be adjacent to a building or other structure, and the water table of the area.

Once the calculations are complete, the drafting team creates detailed drawings. These drawings, called submittals, are then sent to the design engineer or owner for approval. When the submittal drawings are approved, the engineering and drafting teams create production drawings which are sent to the factory floor and used to manufacture the product. The production drawing set includes a bill of materials, or BOM, which includes all the components that go into the product, including sizes and lengths of each piece of rebar and how much concrete (measured in cubic yards) will be used.

工程設計
該過程從工程開始。在每個項目中,設計工程師或所有者(例如交通部,DOT)為其預製組件設定要求。當我們得到圖紙和要求時,每個產品都是根據設計工程師和業主的規格在內部設計的。

工程師確保每個預製結構都具有適當的鋼筋(鋼筋),並滿足其安裝區域的結構要求。一些重要的考慮因素包括土壤類型,預製結構是否與建築物或其他結構相鄰,以及該地區的地下水位。

計算完成後,起草小組會創建詳細的圖紙。這些稱為提交的圖紙然後被發送給設計工程師或所有者以供批准。提交圖紙獲得批准後,工程和起草小組會製作生產圖紙,並將其發送到工廠車間並用於製造產品。生產圖紙集包括物料清單或物料清單,其中包括進入產品的所有組件,包括每塊鋼筋的尺寸和長度以及將使用多少混凝土(以立方碼為單位)。

Prepping the Rebar Cage
When the production team receives the drawings, the first step is to assemble the rebar cage. To do so, they must cut all rebar to the appropriate lengths according to the BOM and then bend and tie them together. Rebar wheelchairs, sometimes called wagon wheels, are round plastic components that hook onto the rebar and ensure it is properly positioned inside the walls of the precast product – not too close to either side of the wall – matching the engineer’s design and meeting the structural requirements.

準備鋼筋籠
當生產團隊收到圖紙時,第一步是組裝鋼筋籠。 為此,他們必鬚根據BOM將所有鋼筋切割成適當的長度,然後將它們彎曲並系在一起。 鋼筋輪椅,有時也稱為馬車輪,是圓形塑料部件,可以掛在鋼筋上,確保它正確定位在預製產品的牆內 – 不要太靠近牆的任何一側 – 符合工程師的設計並滿足結構要求。

Prepping the Form
While the rebar cage is being made, another team preps the forms. This team reviews the drawings to see if the structure has any openings or knockouts and places foam inserts (which are removed after the concrete cures) into the form.

Openings are used where pipes connect or where other junctions are needed. Knockouts are thinner wall sections which allow openings to be “knocked out” in the field once the subcontractor knows where electrical conduit or communication lines would enter the vault. These inserts, along with the proper lifting hardware, are embedded and secured to the form so they don’t move when the concrete is being poured.

Next, the team applies a form oil which is used to ensure the concrete releases easily from the form after it’s cured. Finally, the rebar cage is lifted using a crane and is lowered down into the form. Before concrete can be poured, each product undergoes a pre-pour inspection by a certified quality control technician to ensure it conforms to the production drawings. Once approved, the technician signs off and flags the form, indicating approval to pour the concrete.

準備表格
在製造鋼筋籠的同時,另一支隊伍準備了這些形式。該團隊檢查圖紙,看結構是否有任何開口或敲落,並將泡沫嵌件(在混凝土固化後將其移除)放入模板中。

在管道連接或需要其他連接處的地方使用開口。敲擊器是較薄的壁部分,一旦分包商知道電導管或通信線路將進入拱頂的哪個位置,就允許開口在現場被“敲出”。這些嵌件與適當的提升硬件一起嵌入並固定在模板上,因此在澆注混凝土時它們不會移動。

接下來,該團隊使用一種成型油,用於確保混凝土在固化後很容易從模板中釋放出來。最後,使用起重機吊起鋼筋籠並將其下降到模板中。在澆注混凝土之前,每個產品都要經過認證的質量控制技術人員進行預澆注檢查,以確保其符合生產圖紙。一旦獲得批准,技術人員將簽字並標記表格,表明批准澆築混凝土。

Mixing and Pouring the Concrete
Precast concrete is made up of coarse and fine aggregates, cement, water, and admixtures. It is mixed in the factory’s batch plant according to the concrete mix design specified by the engineer.

Each Oldcastle Infrastructure plant has a concrete laboratory used to conduct routine raw material testing and control exact quantities of each material in a given batch. This is especially important when using high-flow self-consolidating concrete, or SCC, which is used so the concrete flows quickly and easily, filling the mold completely and minimizing the possibility of air pockets.

The lab collects sample cylinders to check the compressive strength and verify the quality of every batch. The concrete also undergoes a variety of additional tests including a spread test to verify the mix has the proper flow and that there is no segregation of the aggregate.

The approved batch of concrete is transported in a dispensing machine to the molds using an overhead crane. When the crane is positioned over the mold, the production team fills each form with the required amount of concrete, taking care to fill the mold completely without trapping air voids. Many plants use vibrating tables to ensure the concrete is completely settled into the form. Once the form is filled, the top is leveled off and the specified finish is applied.

混凝土和澆築混凝土
預製混凝土由粗骨料和細骨料,水泥,水和外加劑組成。它根據工程師指定的混凝土混合設計在工廠的批處理工廠中混合。

每個Oldcastle基礎設施工廠都有一個混凝土實驗室,用於進行常規原材料測試並控制給定批次中每種材料的精確數量。當使用高流量自固結混凝土或SCC時,這一點尤其重要,因為混凝土可以快速,輕鬆地流動,完全填充模具並最大限度地減少氣穴的可能性。

實驗室收集樣品瓶以檢查抗壓強度並驗證每批的質量。混凝土還經過各種附加試驗,包括鋪展試驗,以驗證混合物具有適當的流動,並且沒有骨料的分離。

批准的一批混凝土使用高架起重機在分配機中運輸到模具中。當起重機定位在模具上方時,生產團隊用每種形式填充所需數量的混凝土,注意完全填充模具而不會堵塞空氣空隙。許多工廠使用振動台來確保混凝土完全沉入地下。填充表格後,頂部平整併應用指定的表面處理。

Curing the Concrete
Immediately after the concrete is poured, the curing process begins. This may include putting a tarp over the product overnight to capture the heat generated as part of the hydration process which speeds up curing. The controlled environment of a precast factory enables the product to properly cure and reach the full design strength much quicker than in the field.

固化混凝土
在澆注混凝土後,立即開始固化過程。 這可能包括將防水布過夜放置在產品上以捕獲作為水合過程的一部分產生的熱量,這加速了固化。 預製工廠的受控環境使產品能夠比現場更快地正確固化並達到完整的設計強度。

Stripping the Forms and Inspecting the Product
Once the QC technician confirms that the product has reached the desired strength required (2500 – 3000 psi) to remove the concrete from its form, the stripping process can begin. This involves opening the outer jacket of the mold and collapsing the inner core, attaching the crane’s hooks to the lifting hardware, and moving the product via crate to the post-pour inspection and finishing area.

There, the structure is reviewed by the QC technician to ensure the final product matches the production drawings and that there are no visual defects. Once it passes the final QC inspection and the technician signs off, the product is labeled and transported to the yard, awaiting delivery to the project site.

剝離表格並檢查產品
一旦質量控制技術人員確認產品已達到所需的強度(2500 – 3000 psi)以從其形式中移除混凝土,就可以開始剝離過程。 這包括打開模具的外護套並折疊內芯,將起重機的鉤子連接到提升五金件,並通過板條箱將產品移動到澆注後檢查和完成區域。

在那裡,QC技術人員對結構進行審查,以確保最終產品與生產圖紙相匹配,並且沒有視覺缺陷。 一旦通過最終質量控制檢查並且技術人員簽字,產品就會貼上標籤並運到院子裡,等待交付到項目現場。

FROM:https://www.buildingsolutions.com/industry-insights/how-precast-concrete-is-made-video

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