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The manifestation of sanding on concrete pavement is the pulverization of surface cement slurry, exposure of aggregates, and continuous sand and dust falling off after vehicle rolling, which will gradually develop into rough surfaces and potholes, reducing the bearing capacity and durability of the pavement. The main causes of sanding are concentrated in five aspects: raw materials, mix proportion, construction pouring, maintenance, and later use environment; Governance is divided into preventive measures and disease repair plans. Mild sanding can be treated with permeable curing reinforcement agents, while moderate to severe sanding requires supporting processes such as thin-layer coating and mortar repair. This article systematically sorts out the causes of sanding and provides a graded disposal plan, providing reference for the treatment of concrete pavement diseases in municipal and factory areas.

Analysis of the main causes of sanding on concrete pavement

1.1 Unreasonable mix design

1) Excessive water cement ratio: Excessive mixing water consumption leads to the evaporation of excess free water in the later stage, forming a large number of connected capillary pores on the surface. The structure of cement stone is loose, and its strength is significantly reduced, which is the most common cause.  

2) Insufficient cement usage, selection of low-grade or expired damp cement, decreased cement activity, insufficient hydration reaction, and low strength of surface slurry.  

3) The sand contains excessive mud and stone powder, and the soil wraps around cement particles, hindering hydration and reducing surface wear resistance.

1.2 Defects in mixing, pouring, and vibration construction

1) Add water randomly on site to further increase the water cement ratio; Insufficient mixing time, uneven mixture, and insufficient local slurry.  

2) Insufficient vibration: The surface lacks sufficient cement mortar to lift the slurry; Excessive vibration can cause the mortar to float and segregate, resulting in thick surface slurry, less aggregate, and poor wear resistance.  

3) Improper control of the timing of harvesting: harvesting too early, surface bleeding has not dissipated; Late finishing, the cement slurry has already set, causing disturbance and damage to the hydration structure, forming a loose layer.

1.3 Inadequate maintenance

After the initial setting of concrete, the early water loss is too fast, the hydration of cement is interrupted, and the surface strength cannot increase normally. Failure to timely cover, moisturize, and water for maintenance during hot and windy weather; Insufficient maintenance cycle, early dehydration and pulverization of the road surface. No anti freezing measures were taken during winter construction, resulting in the surface being frozen and the cement stone structure collapsing and sanding.

1.4 External environment and subsequent load damage

1) Freeze thaw cycle: Water infiltrates the pores in northern regions, causing repeated damage to the surface structure due to freezing and expansion;  

2) Carbonization erosion and de icing salt corrosion: damage hydration products, causing surface pulverization;  

3) Opening up traffic too early: Vehicles passing through without meeting the intensity standards, with wheel friction and impact directly grinding down weak surfaces;  

4) Long term heavy load and sudden braking friction of the vehicle exacerbate surface wear and sanding.

1.5 Other factors

Improper selection of release and curing agents can inhibit surface hydration; The settlement and deformation of the base layer cause micro cracks in the road surface, and the infiltration of water vapor accelerates surface damage.

2-level processing measures

According to the severity of sanding, it is divided into mild sanding, moderate sanding, and severe sanding, and different repair techniques are used for each.

2.1 Mild sanding (only surface floating ash, no obvious exposure of aggregate, small decrease in rebound strength)

Applicable materials: permeable concrete sanding treatment agent (lithium based/potassium based silicate curing enhancer) Mechanism: active silicon component penetrates 2 – 8 mm into the concrete surface, reacts with free calcium hydroxide to generate CSH hydrated calcium silicate gel, fills capillary pores, hardens and strengthens inside, has no surface film formation, and is not easy to peel off.  

Construction steps:

1) Cleaning: Sweep and high-pressure air to remove floating sand and dust, rinse off oil stains, dry the base surface, and ensure there is no visible water;  

2) Construction: Low pressure spraying or rolling of the original solution to maintain sufficient infiltration of the road surface, and construction in 1-2 layers as needed;  

3) Static reaction, white frost will precipitate on the surface after rinsing in the later stage;  

4) Maintain for 24-48 hours, reach peak strength growth after 7 days, and then resume normal traffic.

Alternative low-cost solution: Acrylic sand sealing agent (only forms a film on the surface to prevent dust, does not improve the strength of the substrate, has a short service life, and is not recommended for long-term use on heavy-duty roads)

2.2 Moderate sanding (partially exposed aggregate, loose surface, insufficient wear resistance)

Solution: Permeation solidification reinforcement+thin layer wear-resistant mortar cover

1) Polish and remove dust from the base surface, and apply a penetrating curing agent to reinforce the base layer;  

2) Prepare polymer modified cement wear-resistant mortar (it can be mixed with wear-resistant aggregate and a small amount of lotion to improve toughness);  

3) The overall thin cover is 3-8mm, with light absorption molding and moisturizing maintenance;  

4) After meeting the maintenance standards, traffic will be opened to enhance the overall wear and slip resistance.

2.3 Severe sanding (large areas of exposed aggregate, potholes, thick loose layers, significantly insufficient strength)

Solution: Partial excavation or overall milling and re paving

1) Thoroughly mill and remove all loose and sandy layers until a solid and intact concrete matrix is exposed;  

2) Apply cement-based interface agent on the interface to enhance the bond between new and old concrete;  

3) Pour new fine aggregate concrete or wear-resistant surface layer, standardize vibration, finishing and curing;  

4) Large scale diseases can be treated with a thin layer of asphalt overlay as a renovation plan.

3 Preliminary preventive and control measures

1) Strictly control the water cement ratio in the mix proportion, and prohibit adding water randomly on site; Select qualified high-grade cement and strictly control the mud content of sand and gravel;  

2) Standardize mixing and vibration, grasp the time for slurry extraction and surface finishing, and avoid surface bleeding;  

3) After molding, timely cover with geotextile for moisturizing and curing to ensure sufficient curing age; Add anti freezing and insulation measures in winter;  

4) Traffic can only be opened after reaching the design strength, and early restrictions will be imposed on the passage of heavy-duty vehicles;  

5) Optimize anti freezing formula in cold regions, reduce direct corrosion caused by de icing salt, and conduct regular road maintenance inspections.

4 Conclusion

The sanding of concrete pavement is mostly caused by early construction control defects, with excessive water cement ratio and lack of maintenance being the core causes. Engineering treatment should adhere to the principle of “graded disposal”: for mild diseases, priority should be given to using permeable silicate curing agents for internal reinforcement; Moderate use of curing reinforcement+polymer wear-resistant mortar cover; For heavily loose road surfaces, it is recommended to mill and then re lay the surface layer. At the same time, improve the construction control throughout the entire process, prevent sand damage from the source, and extend the service life of concrete pavement.