First, the status quo of the block industry
1. Enterprise profile
According to preliminary understanding, there are more than 200 block factories in our province, with an annual production capacity of about 2 million cubic meters, and the actual annual output is about 6.5438+0 million cubic meters. Single-line production scale is 5,000 ~ 6,543.8+0,000 cubic meters, and the highest annual output is 6,543.8+0,000 cubic meters. The equipment is imported from abroad, mainly producing ordinary concrete small blocks. The production plants are in Daqing and Harbin.
2. Present situation of lightweight aggregate concrete small hollow block
In recent years, with the innovation of wall materials, the deepening of building energy conservation and the development of high-rise buildings, lightweight aggregate concrete small hollow blocks (hereinafter referred to as lightweight aggregate small blocks) have developed rapidly, especially in Harbin, with its advantages of light weight, good thermal insulation performance, high bonding strength of facing, flexible design, convenient construction, fast masonry speed, increased use area and comprehensive project cost, etc., the ceramsite small block factory has reached 65,438+in just a few years. Especially in high-rise buildings, as a peripheral protection structure, it is well received by design, construction and use units. Ultra-light ceramsite small blocks have dominated. In recent years, with the development of high-strength ceramsite, the deepening of "no compaction" and the strict requirements of building energy conservation, Harbin, Qi, Mu and other places attach importance to the development of lightweight aggregate load-bearing thermal insulation and energy-saving small blocks, which have been applied to multi-storey buildings and received good economic and social benefits.
Small blocks made of lightweight aggregate concrete with bulk density not greater than 1 100kg/m3 and light sand, ordinary sand or no sand are called lightweight aggregate concrete small blocks. The classification of lightweight aggregate small blocks can be divided into: artificial lightweight aggregate (shale ceramsite, clay ceramsite, fly ash ceramsite and expanded perlite), natural lightweight aggregate (pumice and volcanic slag) and industrial waste lightweight aggregate (natural coal gangue and cinder). ). According to the purpose, it is divided into thermal insulation type, load-bearing thermal insulation type and load-bearing lightweight aggregate small block. According to the arrangement of block holes, it is divided into solid, single-row holes and multi-row holes. Also, the dry apparent density of ordinary coarse aggregate mixed with light coarse aggregate is less than or equal to 2300kg/m? 3, which is called the second lightweight concrete small block.
3. Present situation of ordinary concrete small blocks
There are four ordinary small concrete block production lines with an annual output of more than 654.38+10,000 cubic meters in our province, including two large oil fields imported from Colombia, 1 from Germany in Daqing Town, 1 from the United States in Harbin Institute of Technology, and about 7-8 small and medium-sized production lines with an annual output of 50-20 million cubic meters in counties and towns in the province. The large-scale production line built in our province is rare in other provinces and cities in China. By the end of 2003, 457 energy-saving block houses had been built in Daqing Oilfield, which played a positive role in promoting wall reform and building energy conservation. From 200/kloc-0 to 2003, two 10 ~ 18-storey small concrete block energy-saving buildings were built in Aji Science and Technology Park, Harbin, with a total construction area of 49,506 square meters, which set a good example for the application of block buildings in high-rise energy-saving buildings in cold areas and opened up new ways.
Second, the existing problems and analysis
1. Small lightweight aggregate block
(1) A large amount of cinder is added to the small ceramsite block.
In recent years, small lightweight aggregate block factories have mushroomed, especially in cold regions. In recent years, there are more than 100 block factories in Harbin alone, among which small ceramsite blocks account for more than 80%. With more manufacturers, there will be competition and mutual price reduction. In order to make money, the cheaper the better raw materials are used, so as to obtain huge profits, thus promoting the rapid decline of product quality. The main reasons are: a large number of civil boiler ash mixed with ceramsite blocks, up to more than 80%; The price difference between cinder and ceramsite per cubic meter is about 10 times. Coal cinder, especially the coal cinder of civil boilers in northern heating areas, has high carbon content due to insufficient combustion, and the water absorption rate of small pieces mostly exceeds 15%, and some of them are as high as 35%. Due to the high water absorption, the destructive power of frost heaving and the poor frost resistance of the block, serious edges and corners appear after 25 times of freezing and thawing, and the strength loss reaches 30%.
(2) Small blocks leave the factory before curing.
In order to increase production and gain profits, some manufacturers naturally maintain small pieces for 7 ~ 10 days before leaving the factory. Before leaving the factory, the block has no waterproof and drainage measures. Therefore, the relative moisture content exceeds the standard, and the drying of the wall after installation leads to cracking, which is an important reason for the wall cracking. In order to prevent the cracks on the upper wall of the block from drying out, the block must be cured for 28 days, preferably 40 days, before leaving the factory.
(3) There are many missing edges and corners, and the appearance quality is poor.
The granularity of some factory pottery is too large, exceeding 20 mm, and the gradation is unreasonable; The cement consumption is small, and the cement consumption of thermal insulation block is only 80 ~ 100 kg/m3, and the compressive strength is not up to standard, which directly affects the appearance quality.
(4) the block type is unreasonable
At present, three rows of small blocks with a hole thickness of 290 mm and a hole width of about 50 mm are widely used in Heilongjiang Province ... However, in order to save materials and reduce the quality, some manufacturers ignore the requirements of thermal insulation performance or do not understand this technical requirement, and change the three rows of small blocks with a thickness of 240 mm and a width of 40 mm to a single row 180 mm, which obviously reduces the thermal insulation performance. When this kind of block is used in Harbin, the whole wall will frost and the decorative veneer material will fall off. Therefore, multi-row porous blocks must be used in cold areas to meet the thermal requirements.
(5) Some production lines do not meet the needs of production development.
The production of small lightweight aggregate blocks for building envelope is generally a simple workshop of indigenous production line, and the factory has no quality assurance system, so the product quality is low and discrete.
In order to better implement the wall reform policy and ensure the quality of products, it is necessary to strengthen the quality management of small blocks, strictly control the entry of blocks, and prohibit unqualified products from entering the construction site and climbing over the wall. The product price should be reasonable, and the price can not be reduced at will, which will affect the product quality; Strengthen the management of small block industry, improve quality of enterprise in an all-round way, support enterprises in scale and level, and improve the scientific and technological content of block products.
2. Ordinary concrete small blocks
(1) Small ordinary concrete blocks are used for external walls in cold areas alone. Because the thermal insulation performance is not as good as that of clay bricks, it can only be used for fences and interior walls, but the dosage is small. Therefore, the development of small block factories in counties and townships is not good.
(2) Small ordinary concrete blocks used for external walls must be combined with efficient thermal insulation materials. If sandwich external insulation is used, connecting steel bars must be used. In order to prevent cracks, the amount of steel bars is large and the cost is high, which also affects its popularization and use. Now it is gradually improving.
(3) External thermal insulation can solve the problem of large amount of thermal insulation and steel bars, but it is not widely used in our province (except Daqing). The main reason is that there are still some problems in people's understanding of ordinary concrete small blocks, and the lack of comprehensive technical and economic analysis and related support policies has also affected the popularization and application.
III. Development Trends and Prospects
1. Market demand forecast
With the development of wall reform and the prohibition of the use of solid clay bricks, the development prospect of building masonry in our province is prospected, and the situation is gratifying. According to experts' prediction, by 2005, the total output of all kinds of building blocks in China will reach 92 million square meters, which will replace about 60 billion solid clay bricks, and our province is no exception. Block is also the main product to replace clay solid brick. According to the statistics of major cities in our province in 20001year, about 654.38+0.28 billion standard bricks were used as wall materials. If 30% of them are replaced by blocks, 5.83 million cubic meters will be needed. At present, the annual output of our province is only about 6,543,800 cubic meters. It will take 9 ~ 10 years to meet the needs of wall reconstruction. With the rapid development of real estate development, it will provide favorable conditions for the development of building blocks.
2. Accelerate the development of thermal insulation and load-bearing lightweight aggregate small blocks according to local conditions.
With the deepening of wall reform, the task before us is how to replace solid clay bricks with new wall materials in multi-storey buildings. In addition to using ordinary concrete blocks, it is urgent to develop lightweight aggregate small blocks with heat preservation and load bearing. It is understood that 60% ~ 70% of the current residential buildings in China are multi-storey buildings. Generally, the frame structure is not used, and the inner wall of prefabricated hollow floor is not used for bearing, but the whole floor is used. So the external wall block must bear part of the weight. It can be seen that it is necessary to vigorously develop high-strength ceramsite, coal gangue, pumice and volcanic slag small blocks, matt concrete, domestic waste small blocks and construction waste small blocks according to local conditions.
3. Effective ways and problems that should be paid attention to With the introduction of a series of national building energy-saving policies, strict requirements have been put forward for the construction, design, construction, engineering quality inspection and the implementation of energy-saving standards by the construction administrative departments, and new requirements have also been put forward for small lightweight aggregate concrete blocks. Therefore, according to the requirements of local energy-saving standards, various localities put forward effective ways to meet the energy-saving standards of small lightweight aggregate blocks. There are five main types:
(1) Single ultra-light ceramsite concrete small block meets the energy-saving standard. It is convenient, efficient and ideal to use a single material in the outer envelope structure in cold areas. But first of all, it is an effective way to produce the ultra-light ceramsite with the required density grade locally, prepare the corresponding ultra-light ceramsite concrete small blocks, and use them to make a single material wall to meet the requirements of external wall energy-saving standards.
(2) Light aggregate small block external thermal insulation composite wall. For the external thermal insulation wall of small lightweight aggregate blocks, the thermal insulation performance of small blocks can be used to reduce the thickness of thermal insulation layer, and at the same time meet the decoration needs of any nail row family, which is more popular in cold areas. Because of its good external thermal insulation performance, it can reduce the influence of thermal bridge, which is a widely used method at present. Last year, the Ministry of Construction issued the standard JC 149-2003, which has a unified standard for external thermal insulation wall, and will promote the development of external thermal insulation wall. However, the quality of polystyrene board and adhesive in the market changes greatly, so special attention should be paid to quality management, which will directly affect the engineering quality.
(3) Small lightweight aggregate blocks are alternately assembled into sandwich panels, which can meet the energy-saving standards. According to the requirements of local energy-saving standards, small lightweight aggregate blocks with different densities are used to compound polystyrene boards with different thicknesses to meet the requirements of energy-saving standards. In order to avoid or reduce the use of connecting steel bars, building blocks are used alternately to prevent the occurrence of "thermal bridge" which is seamless horizontally and vertically, can meet the average heat transfer coefficient, and meets the requirements of energy saving and codes.
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