混凝土Paving-General

为一般的头

混凝土路面有四种类型:

  1. Plain pavements with dowels that use dowels to provide load transfer and prevent faulting,
  2. 没有销钉的平坦人行道, in which aggregate interlock transfers loads across joints and prevents faulting,
  3. Conventionally reinforced pavements that contain steel reinforcement and use dowels in contraction joints, and
  4. Continuously reinforced pavements that have no contraction joints and are reinforced with continuous longitudinal steel.
准备铺路, the subgrade-the native soil on which the pavement is built-must be graded and compacted. Preparation of the subgrade is often followed by the placing of a subbase-a layer of material that lies immediately below the concrete. The essential function of the subbase is to prevent the displacement of soil from underneath the pavement. Subbases may be constructed of granular materials, 室内外试验材料, lean concrete, 或open-graded, 高渗透材料, 稳定或不稳定的. Once the subbase has hardened sufficiently to resist marring or distortion by construction traffic, dowels, tiebars, or reinforcing steel are placed and properly aligned in preparation for paving.

There are two methods for paving with concrete—slipform and fixed form. 在滑模摊铺, a machine rides on treads over the area to be paved-similar to a train moving on a set of tracks. Fresh concrete is deposited in front of the paving machine which then spreads, shapes, consolidates, screeds, and float finishes the concrete in one continuous operation. This operation requires close coordination between the concrete placement and the forward speed of the paver.

在固定形式铺平道路, stationary metal forms are set and aligned on a solid foundation and staked rigidly. Final preparation and shaping of the subgrade or subbase is completed after the forms are set. Forms are cleaned and oiled first to ensure that they release from the concrete after the concrete hardens. Once concrete is deposited near its final position on the subgrade, spreading is completed by a mechanical spreader riding on top of the preset forms and the concrete. The spreading machine is followed by one or more machines that shape, consolidate, 并浮在混凝土表面. After the concrete has reached a required strength, the forms are removed and curing of the edges begins immediately.

After placing and finishing concrete pavements, joints are sawcut to control cracking. Once joints have been inserted, the surface must be textured. To obtain the desired amount of skid resistance, texturing should be done just after the water sheen has disappeared and just before the concrete becomes non-plastic. 纹理是用粗麻布拖动完成的, 人造草皮拖, wire brooming, grooving the plastic concrete with a roller or comb equipped with steel tines, 或者这些方法的组合. The chosen method of texturing depends on the environment, and the speed and density of expected traffic. Curing begins immediately after finishing operations and as soon as the surface will not be marred by the curing medium. Common curing methods involve using white pigmented liquid membrane curing compounds. Occasionally, curing is accomplished by waterproof paper or plastic covers such as polyethylene sheets, 或湿棉垫或粗麻布.

As the concrete pavement hardens, it contracts and cracks. If the contraction joints have been correctly designed and constructed, 裂缝会出现在接缝下方. 否则,就会产生收缩裂缝. 因为混凝土在不断收缩, the joints and/or cracks will open-providing room for the concrete to expand in hot weather and in moist conditions. 一旦路面变硬, the joints are cleaned and sealed to exclude foreign material that would be damaging to the concrete when it expands. The pavement is opened to traffic after the specified curing period and when tests indicate that the concrete has reached the required strength. Immediately before the pavement is opened to public traffic, the shoulders are finished and the pavement is cleaned.