Cement concrete pavement(also known as rigid pavement) is composed of cement concrete faceplate and base (bed) course, including plain concrete pavement(PCCP), reinforced concrete pavement(RCP), steel fiber reinforced concrete pavement, prestressed concrete pavement, continuous reinforced concrete pavement (CRCP), fabricated concrete pavement,etc. It has the characteristics of high strength, good durability, high stability, good flatness and roughness, low maintenance and transportation cost, bright in color, strong reflecting power, etc.
Materials used in cement concrete surface layer include plain concrete, reinforced concrete, continuous reinforced concrete, steel fiber reinforced concrete, roller compacted concrete and so on. You can use the bright degumming 425 or 525 common Portland cement, medium sand or coarse sand and GradeⅠor Ⅱ broken stone(gravel). Requirements for materials used in the double-layer concrete pavement can be appropriately reduced. In order to improve concrete performance, you can add a small amount of early strength agent, air entraining agent, plasticizer, water reducing agent or polymer and other additives. Fillers used in the joints upper part are usually asphalt, slag, asbestos, cork or rubber powder, asphalt grout (also known as asphalt mastic). In addition, there are also using neoprene hollow belt, plastic moulding or PVC cement as fillers, and they can also get better effect.
Because the strength and stiffness of cement concrete pavement are both too high and the stress delivered to soil base is very small (generally not more than 0.05MPa), its requirement for strength is lower than asphalt pavement. Its requirement for supporting capacity is mainly to ensure the stability of base course(especially water stability and roadbed stability). Particularly, appearing no uneven support can ensure that the cement concrete plate is supported by a uniform surface and in a stable state. Therefore, the roadbed (soil base) should be dense, stable and even. It generally requires that soil base uses materials that possess good water stability, the roadbed is in the dry or medium wet state and subside stably.
The base course types of cement concrete pavement: Aggregates(crushed stone, gravel); Stabilized Materials(cement, lime, fly ash or asphalt stabilized aggregates); Poor Concrete and Roller Compacted Concrete
Note: Above base courses have different stiffness, resistance to flushing, and water permeability, so you should select the most appropriate one according to traffic levels, local conditions and economic factors.
Cement concrete surface course should possess the features of sufficient strength, durability, skid resistance, wear resistance and smoothness. The surface course generally use plain concrete and set joints; if the surface layer plate has a larger size or an irregular shape, and there are underground facilities under the pavement structure, and high fill, soft soil foundation and the subgrade of soft soil foundation may appear uneven subsidence, you should use reinforced concrete surface course and set joints too. The projects of other surface course types can be implemented according to applicable conditions.
When the raw materials have been prepared, they will be sent to the central mixing station according to the pre-set formula. The most important equipment of the central mixing station is one or more mixers. The raw materials stored in the barrel will be fed into the mixer by a screw conveyor. The central control room can regulate and control the proportion of raw materials and the time of stirring. After the raw materials are stirred and mixed, next step can go on.
install side formwork, joint insertion strip, dowel bar and reinforcing mesh
mix concrete mixtures and transport them to construction site
pave and vibrate concrete mixtures
level the concrete surface and carve grooves
preserve and joint filling