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Research on the Development of Plastic Formwork at Home and Abroad

Date: 2018-11-08
Browse times: 39

一、General situation


China is a country lacking in timber resources. According to the results of the eighth (2009-2013) forest resources inventory, the per capita forest area is only 1/4 of the world's per capita level, and the per capita forest stock is only 1/7 of the world's per capita level. In China's timber consumption structure, the construction sector is a major consumer of consumables. The annual consumption of timber accounts for about 1/3 of the total national consumption, reaching 150 million cubic meters. Construction timber is mostly of high quality, but due to the influence of construction technology, usage habits and other factors, the turnover usage is very low, resulting in inefficient utilization and waste of resources. Plastic formwork is a new generation of green building materials with the development of China's plastic industry. It has the characteristics of high turnover, 100% recycling and reuse, easy to shape and so on. It is very suitable for national environmental protection, circular economy and other policies. According to estimates, if 1/3 Wood-bamboo plywood formwork is replaced by plastic formwork in the field of construction, the annual consumption of Wood-bamboo plywood formwork can be reduced by 100 million square meters and the replacement of high-quality wood by 2.5 million cubic meters, which is equivalent to the reduction of 43,000 hectares of deforestation, the reduction of carbon dioxide emissions by 7.6 million tons, and the advantages of low-carbon environmental protection are obvious.

In 2013, with the "Green Building Action Plan" officially landed, green building activities in various regions are in full swing. Many provinces and municipalities have issued supporting policies for green building subsidies to vigorously promote the green process. Green building material is a key item in green building evaluation conditions. In the process of rapid development of building formwork towards diversification and lightweight, plastic formwork is a new fourth generation concrete formwork after wood formwork, bamboo plywood formwork and steel formwork. Because of its green building material characteristics of "environmental protection, safety and recyclability", it has been quickly cleared by many construction and formwork rental enterprises. Note and favor. In Germany, North America, Japan, South Korea and other countries with relatively developed plastic industry, plastic building formwork began to be used in large-scale production as early as several decades ago, gradually replacing wood formwork which wastes forest resources seriously and steel formwork which produces high energy consumption. Therefore, replacing wood with plastic not only accords with the development direction of national green circular economy, but also meets the interests of construction enterprises.


二、Development of Plastic Formwork Abroad


Foreign plastic formwork enterprises are mainly concentrated in Europe, North America and Asia, Korea and Japan. The number of enterprises is small, but the scale of production is large, the production technology is more advanced than that in China, and the varieties of plastic formwork products are more diversified. Foreign plastic template products mainly include steel (aluminum) frame plastic template, engineering plastic large formwork, GMT building template, hollow plastic template, foam insulation plastic template, plastic mold shell, decorative template (lining mold), combined plastic template, etc., which can be widely used for wall, floor, column and other building construction. There are also special-shaped plastic templates processed into various shapes and surface patterns. The products have rich decoration and various shapes. The concrete after forming has unique shape and surface texture. In order to enhance the strength and stiffness of plastic formwork, increase the turnover times of plastic formwork and improve the quality of formwork products. There are usually the following ways: 1) adding reinforcing fibers in the process of preparing plastic template; 2) plastics template surface is covered with reinforcing layer or made into sandwich plastic template; 3) plastics template is added ribs or made into hollow ribbed plastic template.


1.Europe and America


1.1 Composite plastic formwork is a large-scale formwork made up of small formwork modules combined and assembled under the cooperation of assemblies. The formwork can be assembled flexibly according to specific construction needs and has a wide range of applications. It has been widely used in Europe at present.

1.2 Steel (aluminium) frame plastic formwork was born in Germany. It is made of steel frame or aluminium alloy hollow profile panel frame with plastic formwork. Compared with large plastic formwork, the weight only increases the quality of the frame, and the stiffness is greater. It can withstand up to 65 kN/lateral force. The formwork is sprayed with electrostatic powder, which can reduce the adhesion of concrete on the formwork, provide a smoother concrete surface, and make the formwork cleaner. It can be widely used in floor and wallboard construction. Steel frame plastic formwork is more expensive than ordinary plastic formwork because of the increase of frame cost. At present, leasing is the main method.

1.3 Thermal insulation plastic formwork originated in North America. It is a disposable wall formwork composed of flame retardant moulded polystyrene foam, angle steel and tied parts. The thickness of the formwork is the same as that of the general wall, usually 50 mm to 100 mm. The concrete can form an integrated thermal insulation wall after pouring. The wall has the characteristics of heat preservation, sound insulation, fire prevention and moisture proof. It is a good energy-saving and environmental protection product, and can be widely used in residential, hospital and hotel building walls.


2.Asia Pacific Region


GMT formwork is widely used in engineering construction in Korea and Japan. It is made of thermoplastic polypropylene fiber and glass mat, combined with certain accessories. It can be divided into two types: GMT plate and GMT ribbed template. The thickness of the template is usually 10-15 mm. The strength of the template is better than that of the simple plastic template, wood-plastic board, PVC board, PP plastic board, etc. Under normal use, it can turn around 40-60 times and use more than 100 times after adding frame. The cost of each turnover is 1/2 of Wood-bamboo plywood template, only 2-4 yuan.


三、Research and Development of Plastic Formwork in China


With the rapid development of China's construction industry, the role of building formwork in engineering construction is becoming more and more prominent. Especially since the application technology of new formwork and scaffolding has been selected as one of the 10 new technologies in the construction industry by the Ministry of Construction, the research, development and application of new plastic formwork in China have made great progress. In recent years, a series of standards and regulations have been promulgated. In 2006, China promulgated the "Green Building Evaluation Standard", in 2013 promulgated the "Wood-plastic Composite Board for Building Formwork" national standards and "Plastic Formwork" industry standards, and in 2014 revised the "Green Building Evaluation Standard". At present, plastic formwork has been applied in construction projects in South China, North China, East China, Central China, Northwest China and other regions, with strong repercussions.

The plastic formwork products used earlier in our country mainly include: stereotyped composite reinforced plastic formwork, strong plastic PP formwork and so on. At present, with the technological innovation and continuous development of template, the types of plastic template products in China are gradually diversified. Such as: wood (bamboo, hemp, glass fiber, etc.) fiber reinforced plastic formwork, hollow ribbed plastic formwork, sandwich foamed plastic formwork, large engineering plastic formwork, steel frame plastic formwork, wood-plastic composite formwork and so on, and some enterprises with slag, fly ash and other industrial waste, wood and straw fibers and other agricultural residues. The residue is blended with waste plastics for granulation, and the plastic template is prepared by high temperature moulding. The template can be used 8 to 12 times.

There seem to be many kinds of plastic formwork in our country, but compared with developed countries, there is still a big gap in product quality and production scale between our country and foreign countries. As a new green construction technology in recent years, building plastic formwork has a relatively low market share and uneven quality in China. Many new plastic formwork products and plastic formwork production machinery still remain in patent technology. These patent technologies are mainly concentrated after 2005, including more than 90 invention patents (32 authorizations, 60 under review), and more than 200 utility model patents.

Generally speaking, the number of patent applications for plastic template technology is increasing. Most of the applicants are enterprises, which shows that plastic template is highly valued by template production and leasing enterprises, but the total number of patents is still small, because plastic template enterprises are mostly small and medium-sized, and their R&D capabilities are relatively inadequate. There are fewer research institutes (less than 20) among patent applicants. To some extent, the investment in science and technology of plastic formwork industry in our country is still insufficient, which slows down the development process of plastic formwork to a certain extent, and is also the fundamental reason for the gap between the development of plastic formwork in our country and that of foreign formwork.

At present, the mainstream plastic formwork used in China's construction market mainly includes injection-moulded modular plastic formwork, hollow plastic building formwork, PVC foam plastic formwork, etc.


四、Performance advantages and characteristics of plastic formwork


The quality of formwork and the speed of installation (disassembly) directly affect the quality of the project and the construction progress. The following table is a comparison of several performance indicators of building formwork:

Table 1 Performance comparison of several building formwork

Performance index

Product type

Plastic formwork

Aluminum formwork

All steel formwork

竹木胶合模板

Composite steel formwork

Plank sheathing

Flame retardancy

Y

Y

Y

N

Y

N

water uptake

and deformation

Non absorbent

No deformation

Non absorbent

No deformation

Non absorbent

No deformation

吸水

易变形

不吸水

No deformation

吸水

易变形

脱模过程

适中

偏难

适中

适中

适中

脱模剂

需要

需要

需要

需要

需要

耐腐蚀性

重复次数

>50

>300

40

6~8

30~40

3~5

可回收性

100%回收

100%回收

100%回收

不易回收

不易回收

不易回收

尺寸定制

可以

可以

不可以

不可以

不可以

不可以


竹木类模板,周转次数偏少,素面的木竹胶合板模板一般使用3~5次,资源利用率偏低,浪费严重,废弃后的模板回收利用困难,大量的模板堆积还会影响施工管理进度;钢模板使用次数较高,但是钢模板比重大,是塑料模板的6~8倍,施工操作难度大,且变形后维护保养成本高,一定程度拖慢工程进度、延长工期,增加施工成本。

塑料模板是21世纪新型绿色施工材料,整体性能优异,具有如下优点:

塑料模板强度高。耐冲击、韧性强,可钉可锯可钻孔,拼接紧密;

质量轻。安装、拆卸所需劳动力较少,施工进度更快,可以减少模板工程费用;

表面光洁。不需要使用脱模剂,表面清理方便,混凝土表面质量可达到清水混凝土效果;

周转次数高。塑料模板周转次数可达50次以上,与钢(铝)框搭配使用可达上百次,单次使用成本低,可比竹木胶合模板节省50%左右;

环保无污染。废弃后的模板可100%回收利用,二次加工制成与原始模板质量相同的模板成品,节能环保。


五、塑料模板发展前景及展望


随着国家绿色建筑的不断推进和日益加强的环境硬约束,建筑领域推广使用塑料模板等绿色建材是必然趋势,以塑代木不仅是响应国家加强生态文明建设的重要举措,更有利于资源高效利用、节能降耗,实现绿色可持续发展。

据中国基建物资租赁承包协会测算,2013年全国建筑模板保有量约4.7亿平方米,其中钢模板拥有量1.4亿平方米,市场占有率30%;木竹胶合板模板拥有量3亿平方米,市场占有率超过65%;塑料模板等新型建筑模板市场应用份额还比较小。而塑料模板是一种绿色环保建筑材料,必将有更为强劲的增长空间和更加广阔的发展前景。值得一提的是,我国塑料消费量目前已居世界第二位,每年有大量废弃的PVC,而建筑模板正好可以消化废弃资源,变废为宝。因此,我国塑料工业迅猛发展也将为塑料模板发展提供源源不断的原材料基础。

需要看到的是,目前我国塑料模板市场发展尚处于起步阶段,产品质量参差不齐,一定程度上对消费者产生误导,阻碍了其推广应用。解决我国塑料模板推广应用问题主要从以下几方面着手:1)必须从模板的设计、生产、施工和租赁等各方面严格把关,根据中国施工实际条件对国外发展较快的塑料模板技术有选择性的吸收,“取之精华,去其糟粕”,实现“为我所用”;2)收集、分析工程施工第一线反馈信息,通过技术创新,不断改进产品设计;3)研发具有自主知识产权的新型塑料模板产品,构建产学研一体化平台,及时将知识产权转化应用于实际生产,塑料模板在我国才会走得更远。




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