How to prevent flatness problems on concrete pavement?

To prevent the problem of flatness of concrete pavement, it is necessary to strictly control the quality in various links such as construction preparation, concrete pouring, pavement paving and subsequent maintenance. The specific measures are as follows:

🌲 Construction preparation

- Do a good job of roadbed treatment: The roadbed is the foundation of the road surface and must be guaranteed to be solid, stable and uniform. Before construction, the original ground should be carefully cleaned, weeds, tree roots, garbage and other debris should be removed, and the soft soil, silt and other unfavorable geological areas should be replaced and reinforced. Fill and compact the roadbed according to the design requirements, control the moisture content of the fill, fill and compact in layers, ensure that the compaction meets the standard, and avoid uneven settlement of the roadbed in the later stage and affect the flatness of the road surface.
- Precise measurement and layout: Use high-precision measuring instruments, such as total stations, levels, etc., to accurately measure and lay out the center line, side line, elevation, etc. of the road surface. During the construction process, the measurement control points should be reviewed regularly to ensure the accuracy of the measurement data. At the same time, according to the measurement results, set the road template or the guide line of the paver to provide an accurate benchmark for road construction.
- Check construction equipment: Ensure that the performance of construction equipment such as concrete mixing equipment, transport vehicles, pavers, and rollers is good and can operate normally. Carry out regular maintenance and maintenance of the equipment, and conduct a comprehensive inspection and commissioning of the equipment before construction. For example, check whether the screed of the paver is flat, whether the vibrating device is working properly, whether the roller wheel of the roller is evenly worn, etc., to ensure that the equipment operates stably during the construction process and avoid problems with the flatness of the road surface due to equipment failure.

🌲 Concrete preparation and transportation

- Control concrete mix ratio: According to the road design requirements and construction conditions, determine the reasonable concrete mix ratio through experiments. Strictly control the quality and amount of raw materials such as cement, sand and gravel, water, and admixtures to ensure that the workability, strength, and durability of the concrete meet the requirements. In particular, attention should be paid to controlling the slump of concrete. The slump should not be too large or too small. If it is too large, it will easily cause concrete segregation and surface water seepage, affecting the smoothness of the road surface; if it is too small, it will make it difficult to spread and vibrate the concrete.
- Ensure the quality of concrete mixing: Use a forced mixer to mix to ensure that the concrete is mixed evenly. Strictly control the mixing time. Determine the appropriate mixing time according to the mix ratio of concrete and the performance of the mixer. Generally, it should not be less than 90 seconds to ensure that the various components of the concrete are fully mixed to avoid uneven distribution of cement slurry and stone clumping, which will affect the working performance of the concrete and the smoothness of the road surface.
- Reasonably arrange concrete transportation: Choose appropriate transportation vehicles to ensure that concrete does not segregate or leak during transportation. According to the distance and traffic conditions of the construction site, reasonably arrange the number of transportation vehicles and transportation routes to ensure that concrete can be supplied to the construction site in time, avoid waiting for too long during transportation, resulting in excessive slump loss, and affecting the quality of concrete spreading and vibration.

🌲 Concrete paving and vibration

- Standardize paving operation: When using a paver for concrete paving, adjust the working parameters of the paver, such as the elevation angle of the screed, vibration frequency, paving speed, etc. The paver should move forward at a uniform speed, and the speed is generally controlled at 2-3m/min to avoid too fast or too slow speed. During the paving process, a special person should be arranged to follow the machine and deal with the leakage and uneven parts on both sides of the paver in time. If manual paving is used, the paving thickness and surface flatness must be strictly controlled. Use tools such as scrapers and shovels to roughly flatten the concrete, and then vibrate it with a vibrating beam or a flat vibrator.
- Strengthen vibration control: Vibration is a key link to ensure the density and flatness of concrete. According to the slump and paving thickness of the concrete, choose the appropriate vibration equipment and vibration method. Generally, a combination of an inserted vibrator and an attached vibrator is used for vibration. The inserted vibrator should be inserted vertically into the concrete, and the vibration points should be evenly distributed. The spacing should not be too large, generally about 1.5 times the radius of the vibrator. The vibration time is based on the concrete surface no longer having bubbles, slurry and sinking, generally 20-30 seconds. The attached vibrator should be installed on the formwork to make the concrete dense by vibrating the formwork. During the vibration process, the vibrator should be prevented from colliding with the formwork, steel bars and force transmission rods, so as not to affect the flatness and structural dimensions of the road surface.

🌲 Pavement finishing and roughening

- Do a good job of finishing: After the concrete is vibrated, the finishing operation should be carried out in time. The finishing is generally done in two times. The first finishing is done after the concrete surface absorbs water. A wooden trowel is used to scrape the surface slurry, gravel, etc. to make the road surface flat. The second finishing is done before the concrete is initially set. An iron trowel is used for fine finishing to make the road surface flatter and smoother. At the same time, attention should be paid to controlling the strength and number of finishing to avoid excessive finishing, which may lead to excessive thickness of cement slurry on the surface, cracks, peeling, etc.
- Standard roughening treatment: After finishing, roughening should be done in time to increase the roughness of the road surface and improve driving safety. The depth and spacing of roughening should be uniform. Generally, the depth of roughening is 2-3mm and the spacing is 2-4cm. Roughening can be done with tools such as a roughening machine or a broom. The roughening direction should be consistent with the driving direction of the road surface to ensure uniform and beautiful roughening quality.

🌲 Maintenance and traffic control

- Timely maintenance of the road surface: After the concrete road surface is poured, it should be maintained within 12 hours. The maintenance method can be to cover with moisturizing materials such as geotextiles and straw mats, and regularly sprinkle water to keep it moist, or spray curing agents for maintenance. The maintenance time is generally not less than 7 days. For high-strength concrete or concrete constructed in high temperature and dry environments, the maintenance time should be appropriately extended. During the maintenance period, it is necessary to ensure that the concrete surface is always moist to avoid shrinkage cracks caused by water loss in the concrete, which will affect the flatness of the road surface.
- Strict traffic control: During the maintenance of the concrete pavement, strict traffic control must be carried out, and all vehicles and pedestrians are prohibited from passing on the road surface until the concrete reaches the design strength. Before the road surface is opened to traffic, the road surface must be inspected and accepted to ensure that the various indicators such as the flatness and strength of the road surface meet the design requirements. At the same time, obvious warning signs should be set up on the road surface to guide vehicles and pedestrians to bypass the construction area to avoid damage to the road surface that has not been fully formed.

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