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Find the source and target it—— Preface to the 8th China Network The (International) precast concrete technology forum was held in Shanghai from May 18 to 19.
On the afternoon of May 19, we visited the industrialization No.
2 base of Shanghai Construction Engineering Group.
Taking this opportunity, we learned about the two mainstream production processes of precast components, looked for the reasons for high production costs, and discussed ways to reduce incremental costs.
Previously, we shared precast components and traditional cast-in-place The huge price difference of components is the main reason for the incremental cost of fabricated structures.
As shown in the figure below, the component price difference accounted for 73% of the incremental cost of a fabricated project in Shanghai in 2017.
(Note: the object discussed in this paper is PC fabricated structure, not the whole fabricated building) the main reason is that the weighted comprehensive unit price of various types of reinforced concrete components is (including reinforcement, concrete and formwork; the comprehensive unit price of the whole cost of supply and installation): (1) traditional cast-in-situ components: 1474 yuan / m3 (100%); (2) prefabricated components: 4000 yuan / m3 (271%).
(special note: the chart data is based on the winning price of a component factory in Zhejiang Province in 2017, which is not the component factory visited this time) further analyzing the supply price of PC components, we will find that in the supply price of prefabricated components, excluding fee and profit tax, labor cost and mold cost account for the highest proportion, 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, to reduce the price of prefabricated components, the first thing to bear the brunt is labor cost and mold cost.
Let’s go deep into the front line of component production 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.
– reinforcement binding is completed – [mold cost of cost thinking] the mold cost of producing prefabricated truss laminated plates is very low.
Because the mold of automatic or semi-automatic assembly line is not customized, but a complete set of equipment.
Even if the laminated plates are produced by fixed platform mold, the bottom mold is also the platform mold surface, only the side mold, and the side mold has regular shape, uniform size and strong universality, so it can be reused for many times.
For the time being, according to the calculation of 100 times of turnover, the mold cost of prefabricated laminated floor slab is within 100 yuan / m3.
Traditional cast-in-situ buildings, The formwork cost of the floor slab is about 500 yuan / m3 (100 thick floor slab, the formwork consumption is 1m2 / m2, i.e.
10m2 / m3, and the formwork unit price is 50 yuan / m2).
That is, the mold cost of the two production modes of cast-in-situ and prefabrication is roughly as follows: (1) traditional cast-in-situ floor slab: 500 yuan / m3 (2) prefabricated truss laminated floor slab: 100 yuan / m3, i.e.
the cost advantage of industrialized production mode in mold (i.e.
the advantages of standardized design and large-scale production) is incisively and vividly displayed on the simplest component such as floor slab.
Therefore, if the molds of all components can reach such turnover times, the cost of industrialized production mode will be greatly reduced.
– this is the advantage of industrialized production mode.
There are at least two ways to realize this advantage.
One way is to standardize design, realize large-scale production and greatly improve the turnover times of molds; 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, so as to improve the turnover times Concrete placing by concrete distributor – manual auxiliary leveling of concrete – steam curing device – [labor cost of cost thinking] plane components such as laminated plate and laminated wall can be produced by automatic (semi-automatic) assembly line, which can reduce the number of workers (taking this semi-automatic assembly line in this paper as an example, the station of a single assembly line is about 6 people).
Calculated according to the labor capacity of 1m3 / day, that is, the labor consumption per m3 component is 1 man day.
According to 300 yuan / man day, the labor cost of component production is 300 yuan / m3 (including reinforcement fabrication and installation, concrete pouring, formwork installation and disassembly, excluding formwork fabrication labor).
However, the labor cost of traditional cast-in-situ components (according to the same caliber as the labor cost in the supply price of prefabricated components) 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 traditional cast-in-situ floor slab: 348 yuan / m3 (100%) (2) Labor cost of prefabricated truss composite floor slab: 300 yuan / m3 (86%) (if considering the labor cost of 60mm cast-in-situ layer above 70mm thick composite floor and reinforcement and concrete pouring process, 100 yuan / m3 shall be added), that is, even the relatively advanced semi-automatic assembly line produces relatively standard plane components (such as truss laminated plate), at present, the labor cost in the production link can only be reduced by 14%, which has not been able to give full play to the labor advantage of industrial production; if the labor cost of reinforced concrete construction of laminated post cast layer is considered, the truss laminated plate has no advantage in labor cost.
(for the full-automatic production line, we have not obtained the corresponding labor consumption data at present) summarize the cost thinking of the semi-automatic production line.
Based on the truss laminated plate of this semi-automatic production line, the mold cost can be greatly reduced, and the labor cost can only be slightly reduced, or even exceed the cast-in-place method.
As shown in the figure below (1) Mold cost: the cost advantage of industrialized production mode in mold (i.e.
the advantages of standardized design and large-scale production) is incisively and vividly demonstrated in the simplest component such as floor.
(2) labor cost: even the relatively advanced semi-automatic assembly line produces relatively standard plane components (such as truss laminated plate), at this stage, the labor cost in the production link can only be reduced by 14%, which has not been able to give full play to the labor advantage of industrial production.
Therefore, based on the semi-automatic assembly line production mode, there are two ways to reduce the die cost of prefabricated component production and realize the advantage of industrial production: standardized design and innovative die design.
One is from building to component Standardized design, realize large-scale production and greatly improve the turnover times of molds; The second is the innovative design of mold, which is innovative in material selection and mold combination design.
In order to reduce the labor cost of prefabrication production of plane components such as laminated plates, we must give full play to the advantages of large-scale and automation of industrial production, so as to reduce labor consumption.
Let’s look at the second production line.
（2） The scene in the figure below is different from the industrialized production mode we imagined, but it is the most common production mode of prefabricated components in the industry.
– completion of mold assembly – [cost thinking] in the case of the Yangtze River Delta in 2017, the weighted average value of various components was 479 yuan / m3.
Is this data high or low? First, let’s see whether the steel mold materials themselves make the best use of their resources.
The comprehensive unit price of the steel mold of the project is 13 yuan / kg, that is, the consumption index of the steel mold of the project is 37kg / m3.
According to the experience According to the inspection data, the mold turnover times of this project are about 50 ~ 60 times.
The theoretical turnover times of such steel molds are more than 100.
Therefore, for this project alone, there is also a waste of molds, which does not give full play to the advantage that industrial production can reduce the cost of molds..
