Advantages and disadvantages of GRP manhole cover
There are three categories: steel fiber reinforced concrete manhole cover, recycled resin GRP manhole cover and fiberglass manhole cover
1. Steel fiber reinforced concrete manhole cover is an improved product of the original reinforced concrete manhole cover. It is to add about 2cm long steel fiber into the concrete, a large number of steel fibers are dispersed in the concrete, forming irregular radial distribution, so that the concrete strength is strengthened, greatly improving the toughness of the concrete, its bending tensile strength, fatigue cracking strength, etc. are greatly improved, and at the same time, the crack width can be reduced. In order to reduce the phenomenon of edge collapse in the use of steel fiber reinforced concrete manhole cover, a metal frame is usually added outside the manhole cover. The strength of the steel fiber reinforced concrete manhole cover is more than 30% higher than that of the common concrete manhole cover with the same proportion, and its performance is close to that of the cast iron manhole cover. Moreover, the steel fiber reinforced concrete manhole cover has the advantages of low production cost, small recovery value, anti-theft, etc., so it has a certain share in the market, but it is the most obvious
The obvious defects are bulkiness and insufficient bearing capacity.
2. Recycled resin composite manhole cover is a kind of synthetic resin based composite product, which is made of fly ash and waste plastic, mixed in the molten state and formed by pressing. This kind of composite manhole cover is made of waste materials, without any steel or other recyclable materials, so it has the function of anti-theft. At the same time, it can digest a lot of fly ash and waste plastics in the manufacturing process, which meets the requirements of national energy conservation and environmental protection policies. Therefore, it is called "green well 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 rust. Its quality has reached the level of similar cast iron products, and its cost is about 30% lower than that of cast iron products. Its economic benefits are significant, so it has a strong market competitiveness. However, the quality and performance of the recycled resin composite inspection well cover is not stable in the use process, especially in the case of high temperature, vehicles continue to roll. The quality of the well cover will change, causing the middle part of the inspection well cover to sink and even fall off, which will produce a great potential safety hazard.
3. Glass fiber reinforced GRP manhole cover is made of unsaturated polyester resin as raw material, glass fiber as reinforcement material and certain filler. Due to different technology, structural materials and reinforcement materials, the properties of manhole cover products are also very different. Generally, the process of producing fiberglass manhole cover in China includes:
(1) Resin transfer molding process. Due to the high resin content, the manhole cover is not suitable for use on the roadway due to its insufficient bearing capacity;
(2) Hand paste making process. It is not suitable for large-scale production and has no competitive advantage;
(3) Molding process. The product structure is relatively dense. It uses different materials in different parts of the manhole cover. Use continuous fiber reinforcement under the manhole cover. To ensure its bearing capacity: use filler in the middle part. In order to improve the deformation resistance and reduce the production cost of the product: use the materials with high hardness and good wear resistance on the upper part of the product to improve the compression resistance and wear resistance of the upper part of the product. Glass fiber reinforced plastic manhole cover is gradually popularized because of its light material, high strength, fatigue resistance, corrosion resistance, not easy to brittle failure, easy to process and shape.
With the GB / t23858-2009 inspection well cover standard issued by the state in 2009, the new product quality standard improves the load requirements of the well cover, which is in line with the internationally accepted en124 standard. After the implementation of the standard from February 1, 2010, it is clear that the composite well cover is one of the inspection well covers, and its characteristics are described as follows: polymer is used as the matrix material, reinforcement material and filler are added, and the inspection well cover compounded by a certain process is popularized and applied in the market. The polymer all composite well cover has the advantages of light weight, high strength, good fatigue resistance, good damage safety, superior molding technology, low rolling noise, non corrosion, acid and alkali resistance, beautiful appearance and so on. It has become an ideal substitute for cast iron well cover.
Problems found in the use of composite well covers:
There are many kinds and formulations of composite manhole covers, such as steel fiber 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 very difficult for users to check and judge the quality by simple methods such as appearance and hand feeling. Therefore, composite manhole covers must not be cheap to choose non-standard products.