Current Situation and Future Development of China Wall Materials Industry |
| FROM： CREATEDATE：2009-02-04 |
Wall materials industry ranks the second of all building materials industries in China in terms of output value, which accounts for over 20 per cent of the total.
The weight of wall generally accounts for over 50 per cent of the total weight of a building, or even higher in buildings with load-bearing wall. Modern buildings use more glass, plastic and metal as structural materials. Although conventional wall material is the heaviest of all building materials used in construction, it is still most often used. Conventional wall uses large quantity of raw materials and has the characteristics of heavy weight and low cost. In China , conventional wall materials are manufactured with local resource for local market.
Building construction uses large quantity of wall materials of many different types, which are mostly local-manufactured. The wall material development has to keep up with the development of construction industry.
1. Current Situation
China used mostly solid burnt clay brick as wall material. The brick history can be traced back to 2000 years ago in Qin Dynasty, when the world famous Great Wall was built using large quantity of burnt clay bricks. Since 1960s, China has been engaged in the development of other wall materials, generally referred to as new wall materials.
China is a big country with a large population and it has been developing rapidly these years. About 1.4-1.6 billion square meters of new buildings are constructed each year in China , ranking the first in the world. As a result, China consumes the largest amount of wall materials in the world. The annual output of wall materials in China is around 900 billion in terms of standard brick. Among this quantity, about 600 billion is solid burnt clay brick, accounting for 65 per cent of the total, however, new wall materials only account for about 35 per cent of the total.
The Chinese government has put forward policies that stipulate new wall materials to replace solid burnt clay brick as major wall materials. In 1992, the State Council issued policies to strictly limit the use of solid burnt clay brick. The State Tax Bureau issued preferable tax policies to promote the development of new wall materials, which contribute to energy conservation and waste utilization. However, in most rural and less developed areas with abundant clay resources, burnt clay brick will remain the major wall material.
In near future, while new wall materials will develop rapidly in China , burnt clay brick will continue to hold a considerable market share for the time being.
China has developed many different kinds of wall materials. They can be categorized into different groups:
by sintering methods: burnt brick, including solid and hollow clay brick, coal spoil brick, fly ash brick, shale brick, and burnt clay lath brick; and non-burnt brick, including brick, block and slab made from cement, limestone, gypsum or other organic plastering agent together with other materials.
by shape: slab, including slab, cored slab, aerated concrete slab, GRC slab, metal sheet; and block, including all kinds of solid or hollow brick and block.
by raw material: cement, gypsum, lime, magnesite, coal gangue, fly ash, sand, clay and vegetable fiber etc.
by part of the building: exterior wall, interior wall, and walls for kitchen and bath room.
by wall structure: single solid structure, composite/sandwich structure
by function: capacity insulation, heat retaining, water proofing, damp proofing, fire proofing, decoration, load-bearing and non load-bearing etc.
Due to imbalanced economic development of different areas, there exist both advanced and outdated technologies. Generally speaking, China still lags behind western countries in wall material development. Take brick for example, the cavity ratio of load-bearing hollow bricks produced by developed countries is 15-40 %, and the compression strength is 20-55 MPa. The compression strength of the bricks produced in China , however, is only 10-25 MPa. Average labor productivity is only 100,000 – 150,000 pieces per year in China . The figure was already 2,500,000 pieces per year in the developed countries during 1970s. China wall materials industry should develop lighter products with better performances in energy conservation, waste utilization, and decoration.
2. Future Development
2.1 Solid burnt clay brick
The Chinese government has set a basic national policy of developing new energy-saving wall materials and reducing the production of traditional solid burnt clay bricks. Burnt clay brick is allowed when there is easy access to clay resource without destroying farmland. However, the output of hollow clay brick should be increased. At the same time, new wall materials, including all kinds of masonry materials and slabs, which use less or no clay, should be developed. According to the development strategy set by former State Bureau of Building Materials Industries, the proportion of new wall materials should reach 35 per cent, 40 per cent, and 60 per cent in year 2005, 2010, and 2030 respectively.
2.2 New wall materials
Building construction calls for wall materials with characteristics of lightweight, high strength, long durability, and easy construction, which should be the focus of R & D on new wall materials. At the same time, wall materials for cold, hot, damp or dry weather condition in different areas should be developed with local resources.
2.3 Composite wall materials
While energy consumption should be reduced in wall material manufacturing, building energy conservation by wall materials is also one of the development focuses. In China , average heat transmission of exterior wall accounts for about 1/4 of the total energy consumption of the building. In Beijing , it is required that the heat transfer coefficient should be less than 0.82 w/(m2·k) – 1.16 w/(m2·k) for residential buildings with heating apparatuses. For extremely cold area, the heat transfer coefficient should be less than 0.40 w/(m2·k) – 0.52 w/(m2·k). Yangtze River Delta is located in subtropical zone of China, where air conditioner is widely used for hot summer and heatproof wall materials are required for cold wintertime. Composite wall material instead of single wall material is the key to building energy conservation. China has been conducting R & D in composite wall materials. Using masonry materials, slab, and thermal insulating materials to construct composite wall on site is one of the practices.
2.4 Utilization of solid waste
Industrial or agricultural solid waste can be utilized in wall material manufacturing. China has earned substantial experiences in utilizing fly ash, breeze, and coal gangue to produce wall materials. Utilization of mine waste, steel slag, phosphogypsum, fuel gas desulphurized gypsum, and all kinds of vegetable fiber has also been developed. In China , wall material industry will follow the guidelines of Recycle Economy, i.e. energy conservation, farmland protection, waste utilization and high product quality, to achieve sustainable development.
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