by The number of words is 4300.
The reading time is 8 minutes to find the source—— The 8th China (International) Precast Concrete Technology Forum was held in Shanghai from May 18 to 19.
On the afternoon of the 19th, I visited the second industrialization base of Shanghai Construction Engineering Group.
We take this opportunity to learn about the two mainstream production processes of prefabricated components on the spot, find out the reasons for high production costs, and explore ways to reduce incremental costs.
Previously, we shared that the huge price difference between prefabricated components and traditional cast-in-place components is the main reason for the incremental cost of prefabricated structures.
As shown in the figure below, the component price difference accounted for 73% of the incremental cost of a prefabricated project in Shanghai in 2017.
(Note: the object of the whole discussion is PC prefabricated structure, not the whole prefabricated building) The main reason is that the weighted comprehensive unit price of all types of reinforced concrete components is (including reinforcement, concrete, formwork; comprehensive unit price of the full cost of supply and installation): (1) traditional cast-in-place components: 1474 yuan/m3 (100%); (2) Prefabricated components: 4000 yuan/m3 (271%).
(Special note: the chart data is based on the 2017 bid price of a component factory in Zhejiang Province, not the component factory visited this time.) Further analysis of the supply price of PC components shows that, in addition to the cost and profit tax, the labor cost and mold cost account for the highest proportion of the supply price of prefabricated components, accounting for 32% in total, exceeding the proportion of main materials (25% in total for reinforcement and concrete): (1) labor cost: 600 yuan/m3, accounting for 17%, ranking first; (2) Mold cost: 479 yuan/m3, accounting for 15%, ranking second.
Therefore, in order to reduce the price of prefabricated components, labor costs and mold costs are the first to bear the brunt.
Next, let’s go deep into the component production line to find out.
（1） The following figure shows the semi-automatic assembly line in the building component industrialization base (No.
2 base) of Shanghai Construction Engineering Group Steel bar binding completion – [mold cost of cost thinking] The mold cost of producing prefabricated truss composite plate is very low.
Because the molds of automatic or semi-automatic assembly lines are not customized, but complete sets of equipment.
Even if the laminated plate is produced by fixed bench mold, the bottom mold is also the bench mold surface, and there is only the side mold.
The side mold has regular shape, uniform size, and strong versatility, so it can be used repeatedly.
For the time being, the mold cost of prefabricated laminated floor slab is within 100 yuan/m3 based on 100 times of turnover.
Traditional cast-in-place buildings, The formwork cost of the floor slab is about 500 yuan/m3 (100 thick floor slab, the amount of formwork is 1m2/m2, that is, 10m2/m3, and the unit price of formwork is 50 yuan/m2), that is, the mold cost of the two production methods of cast-in-situ and prefabricated is roughly as follows: (1) traditional cast-in-situ floor slab: 500 yuan/m3 (2) prefabricated truss composite floor slab: 100 yuan/m3, that is, the cost advantage of industrial production mode in mold (that is, the advantage of standardized design and large-scale production) The floor is the simplest component.
Therefore, if the mold of all components can reach such turnover times, the cost of industrial production mode will be greatly reduced—— This is the advantage of industrial production mode.
There are at least two ways to realize such advantages.
One way is to standardize design, realize large-scale production and greatly increase the number of mold turnover; The second way is to innovate mold design, innovate in material selection and mold combination design, either select appropriate mold materials according to the specific turnover times of the project, or refine mold combination design to improve the compatibility of mold components, thus improving the turnover times Concrete placing machine pouring concrete – manual auxiliary paving concrete – steam curing device – [labor cost of cost thinking] The plane components such as composite plates and composite walls can be produced using automatic (semi-automatic) assembly lines, which can reduce the number of workers (taking the semi-automatic flow line in this article as an example, the number of stations in a single assembly line is about 6).
According to the labor capacity of 1m3/day, that is, the labor consumption per m3 of component is 1 workday.
According to 300 yuan/workday, the labor cost of component production is 300 yuan/m3 (including reinforcement and installation, concrete pouring, formwork installation and removal, excluding formwork production labor).
The labor cost in the traditional cast-in-place components (according to the same caliber as the labor cost in the supply price of prefabricated components) is about 348 yuan/m3.
Under the same caliber as the labor cost required for the production of prefabricated components (including reinforcement fabrication and installation, concrete pouring, formwork installation and removal, excluding formwork fabrication), The labor cost of the two production methods is roughly as follows: (1) the labor cost of the traditional cast-in-place floor slab: 348 yuan/m3 (100%) (2) the labor cost of the prefabricated truss composite floor slab: 300 yuan/m3 (86%) (if the labor cost of the cast-in-place floor slab with a thickness of more than 70 mm and a thickness of more than 60 mm, as well as the labor cost of the reinforcement and concrete pouring process, it will also add 100 yuan/m3), that is, even the relatively advanced semi-automatic assembly line produces relatively standard plane components (such as truss laminated plate), the labor cost in the production process can only be reduced by 14% at this stage, and the labor advantage of industrial production has not been brought into play; If the labor cost for the construction of reinforced concrete in the post-cast layer is considered again, the truss composite plate has no advantage in labor cost.
(For the fully automatic production line, we have not obtained the corresponding labor consumption data at present) Summary of the cost thinking of the semi-automatic production line.
Based on this semi-automatic production line, the truss laminated plate can significantly reduce the mold cost, and the labor cost can only be slightly reduced, or even reverse the cast-in-place method.
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