What kinds of technical jobs have been added to precast concrete construction compared with cast-in-place concrete construction?

You can often see some articles introducing the advantages of prefabricated buildings on the internet, in which it is mentioned that prefabricated components of prefabricated buildings are all produced in factories and hoisted and spliced on site. The mechanization of construction and assembly is high, which greatly reduces the on-site workload and has the advantages of shortening the construction period, saving resources and low cost.

Is that really the case? The answer is no.

Second, misunderstanding 1: prefabricated buildings save time.

First of all, we compared the technological process of cast-in-place structure, including construction setting-out, steel binding, water and electricity embedding, formwork binding, support erection, concrete pouring, maintenance and formwork removal. Next, let's take a look at the technological process of prefabricated buildings, which not only includes the above steps, but also has several more processes than cast-in-place. The technological process of prefabricated buildings is divided into: construction setting-out, external wall panel hoisting, wall column steel binding, wall column water and electricity embedding, formwork installation, support erection, composite beam and slab hoisting, concrete pouring and maintenance and form removal.

Compared with traditional prefabricated buildings, prefabricated buildings have more hoisting steps. The standard floor of traditional cast-in-place structure usually takes 4~5 days, while the standard floor of assembled building usually takes more than 7 days.

From the progress of the above standard floor, it can be found that it takes about two days for the external wall panel to be hoisted, and it takes about one day for the composite panel to be hoisted relatively quickly. Moreover, during the hoisting operation, the tower crane can't carry out other operations, and the steel bar binding and water and electricity embedding can't be completed before it. Hoisting is the key process of prefabricated building construction.

Third, the second misunderstanding: the production cost of the project is low

It is indeed a fabricated building in engineering, and the complexity of the working environment and the degree of mechanization on site are better than that of cast-in-place construction. However, when we calculate the cost of prefabricated components, we still need to consider the cost of making molds. Due to the low standardization of high-rise residential buildings, the molds of prefabricated components need to be customized, and they cannot be recycled after being used once, which leads to the increase in the cost of prefabricated components.

According to statistics, the cost of prefabricated buildings is obviously higher than that of cast-in-place structures, and the higher the prefabrication rate, the higher the cost. Refer to the following prefabricated building scheme:

Scheme 1: the assembly rate is 0%, the prefabrication rate is 0%, and there are no prefabricated components.

Scheme 2: The assembly rate is 6%, the prefabrication rate is 20%, and prefabricated components (laminated board, prefabricated balcony, stairs, air conditioning board, prefabricated decorative parts) are adopted.

Scheme 3: The assembly rate is 6%, the prefabrication rate is 25%, and the prefabricated components (sandwich panels, prefabricated balconies, stairs, air conditioning panels, prefabricated decorative pieces and sandwich beams).

Scheme 4: The assembly rate is 24%, the prefabrication rate is 40%, and the prefabricated components (sandwich panels, prefabricated balconies, stairs, air conditioning panels, prefabricated decorative pieces, sandwich beams, and facing external walls).

Scheme 5: The assembly rate is 50%, the prefabrication rate is 60%, and the prefabricated components (sandwich panels, prefabricated balconies, stairs, air conditioning panels, prefabricated decorative pieces, sandwich beams, facing external walls and prefabricated internal walls).

Scheme 6: The assembly rate is 70%, the prefabrication rate is 60%, and the prefabricated components (sandwich panels, prefabricated balconies, stairs, air conditioning panels, prefabricated decorative pieces, sandwich beams, facing external walls, prefabricated internal walls and prefabricated caissons).

Scheme 7: The assembly rate is 90%, the prefabrication rate is 70%, and the prefabricated components (laminated board, prefabricated balcony, stairs, air conditioning board, prefabricated decorative parts, laminated beam, sandwich outer wall, prefabricated inner wall and prefabricated caisson).

With the increase of prefabrication rate, the construction cost is increasing. The cost per square meter of ordinary cast-in-place structure is around 1 100, while that of assembled structure is above 1300 or even 1400.

Fourth, summary.

From the above analysis, prefabricated buildings are not fast and the cost is not high. Why does the country push prefabricated buildings? In fact, prefabricated buildings have their own advantages. As the price of labor is getting higher and higher, it is bound to be a development trend for factories to manufacture prefabricated buildings. In addition, the impact of prefabricated buildings on the urban environment has been significantly improved, and prefabricated buildings are bound to be the direction of development, which only takes time.