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Advantages And Disadvantages Of Composite Manhole Cover

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1. Steel fiber reinforced concrete manhole cover is an improved product of the original reinforced concrete manhole cover. It is about 2 cm long steel fiber is added into the concrete, and a large number of steel fibers are dispersed in the concrete to form irregular radial distribution, so as to strengthen the strength of the concrete and greatly improve the toughness of the concrete. Its bending tensile strength and fatigue cracking strength have been greatly improved, and the crack width can be reduced at the same time. In order to reduce the collapse of steel fiber reinforced concrete manhole cover in the process of use, metal frame is usually added outside the manhole cover. The strength of steel fiber reinforced concrete manhole cover is more than 30% higher than that of ordinary concrete manhole cover with the same proportion, and its performance is close to that of cast iron manhole cover. Moreover, the steel fiber reinforced concrete manhole cover has the advantages of low production cost, small recovery value and anti-theft, so it has a certain share in the market, but its most obvious defects are bulkiness and insufficient bearing capacity.
2. Recycled resin composite manhole cover is a kind of synthetic resin based composite material product, which is made of fly ash and waste plastic as raw materials, mixed in molten state and formed by pressing. This kind of composite inspection manhole cover is made of waste materials, without any steel or other recyclable materials, so it has anti-theft function. At the same time, it can digest a large amount of fly ash and waste plastics in the manufacturing process, which meets the requirements of national energy conservation and environmental protection policy, so it is called "green manhole cover". At the same time, its compressive strength, bending strength, impact strength and other properties are better, and it has the advantages of no corrosion and no rust. Its quality reaches the level of similar cast iron products, and its cost is about 30% lower than that of cast iron products. The economic benefits are remarkable, so it has a strong market competitiveness. However, the quality performance of the inspection well cover made of recycled resin composite material is not stable in the process of use, especially in the case of high temperature. The quality change of the manhole cover will occur, which will cause the middle part of the inspection well cover to sink continuously and even fall off, which will produce great safety risks.
3. Glass fiber reinforced plastic inspection well cover is made of unsaturated polyester resin as raw material, glass fiber as reinforcement material and certain filler added. Due to different technology, structural materials and reinforcement materials, the properties of inspection well covers made of are also quite different. The domestic production process of FRP manhole cover generally includes:
(1) Resin transfer molding process. Due to the high resin content, the manhole cover made of is not suitable for use on the roadway due to its insufficient bearing capacity;
(2) Hand paste production technology. Production efficiency is slow, not suitable for large-scale production, and there is no competitive advantage;
(3) Molding process. The molding process is laminating and pressing under certain temperature and pressure. The product structure is relatively dense, and different materials are used in different parts of inspection manhole cover. Continuous fiber reinforcement was used under the manhole cover. To ensure its bearing capacity: use fillers in the middle. In order to improve the anti deformation ability of the product and reduce the production cost: use the material with higher hardness and good wear resistance in the upper part of the product, so as to improve the compression resistance and wear resistance of the upper part of the product. Glass fiber reinforced plastic manhole cover has been gradually popularized due to its advantages of light material, high strength, fatigue resistance, corrosion resistance, brittleness resistance and easy processing.
With the GB /T 23858-2009 inspection well cover standard issued by the state in 2009, the new product quality standard improves the load requirements of manhole cover, which is in line with the international standard en124. After the implementation of the standard from February 1, 2010, the composite manhole cover is defined as a kind of inspection well cover, and its characteristics are described: the manhole cover made of polymer as matrix material, reinforced material, filling material, etc. is compounded by a certain process, and its popularity and application in the market. The polymer all composite material manhole cover has the advantages of light weight, high strength, good fatigue resistance, good damage safety, superior molding technology, low noise, non-corrosion, acid and alkali resistance, beautiful appearance, etc., which makes it an ideal substitute for cast iron manhole cover.
Problems found in the use of composite manhole covers include:
There are many kinds and formulas of composite manhole covers, such as steel fiber reinforced concrete, glass fiber reinforced plastics, recycled resin, silicon plastic composite, polymer based composite, polymer composite, etc. Due to the short development time. Market competition is fierce. Businesses often cut corners in order to make profits. It is difficult for users to judge the quality of the products by simple methods such as appearance and feel. Therefore, the composite manhole cover must not be greedy for cheap choice of non-standard products.
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