How to Make Prefabricated Apron for House

The production of prefabricated aprons for houses should follow the following structural layers and construction points:

I. Compacted Soil Layer The compacted soil layer is the foundation of the apron, and its uniform density directly affects the overall stability, with the core indicator being the compaction coefficient. When there are no special design requirements, the compaction coefficient should be ≥0.9. During construction, it should be compacted in layers to ensure that there are no weak underlying layers in the soil, preventing apron cracking due to later settlement.

II. Cushion Layer Construction

1. Material Selection:
   • Under normal circumstances, the cushion layer height is 150 millimeters, and 3:7 lime-soil (a volume ratio of 3 parts lime to 7 parts clay) or pebbles filled with cement mortar are preferred.
   • If the groundwater level is higher than 1.5 meters below the outdoor ground level, 3:7 lime-soil is susceptible to groundwater erosion, and a 0.3-meter to 0.45-meter natural graded sand and gravel cushion layer should be used instead to enhance drainage and erosion resistance.
   • In severely cold or frost-heaving soil areas, the cushion layer should use medium-coarse sand, sandy gravel, slag, and other frost-heaving-resistant materials to prevent damage to the apron structure due to soil expansion in winter.
2. Construction Requirements: The width of the cushion layer should exceed the edge of the surface layer by 100 millimeters to provide operating space for surface layer construction and enhance edge shear resistance. During laying, it should be vibrated and compacted in layers to avoid hollow or loose areas.

III. Surface Layer Treatment

1. Materials and Processes:
   • Commonly, 50-millimeter-thick permeable concrete (such as diluted C20 concrete) or 1:1:1 diluted surplus concrete is used, and the surface should be compacted and smoothed. Decorative practices such as inlaying pebbles with ink cement mortar or pasting granite can also be adopted, with the specific material determined by the design.
   • When the surface layer is completed, the outer edge of the apron should be at least 20 millimeters higher than the outdoor ground level to form a reverse slope and prevent rainwater from flowing back into the foundation.
2. Slope Control: The overall slope of the apron should be controlled between 3% and 5% to ensure smooth drainage. The slope can be achieved by adjusting the thickness of the surface layer concrete or mortar, and a level should be used for detection during construction.

IV. Anti-Cracking Measures

1. Structural Reinforcement:
   • Reinforcing bars should be pre-embedded in the ring beam, and a steel wire mesh should be laid on the surface before pouring concrete. The stress can be dispersed through the steel bar framework to reduce cracks caused by uneven settlement.
   • Using reinforced concrete entirely to make the apron (with a reinforcement ratio meeting design requirements) can significantly improve its crack resistance and is suitable for areas with complex geological conditions or heavy loads.
2. Setting of Expansion Joints: An isolation joint (expansion joint) should be set at the junction of the apron and the plinth, with a width generally of 20-30 millimeters, filled with asphalt hemp fiber or elastic sealing materials. A transverse expansion joint should be added every 6-12 meters to release temperature stress and prevent cracking due to thermal expansion and contraction.

V. Other Requirements

• The total thickness of the apron should preferably be 60-70 millimeters, balancing strength and economy.
• After construction is completed, it should be covered and cured for at least 7 days to prevent early water loss and cracking.
• During winter construction, insulation measures should be taken to prevent the concrete from freezing and ensure that the strength meets the standards.