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Pervious Concrete Installation Process Step 2: Placing
A stone reservoir is installed as a subbase for the pavement, creating large air voids and allowing for further water infiltration and storage. Prior to concrete placement, this layer is compacted to 92-96% of its maximum density, so as to provide maximum support while maintaining permeability. The level of compaction depends on the soil properties, pavement design, and infiltration requirements.
Soil with high clay content has low permeability, requiring a thicker stone reservoir to compensate for decreased water retention. Engineering fabrics are often used to separate the soil and stone layers. The subbase must be kept moist in order to prevent the lower portion of the pavement from drying out too quickly. The longer the drying time, the greater the strength and durability of the concrete.
Because of its thick, rocky consistency, discharge from concrete mixers is slower for pervious concrete than for dense. Since it cannot be pumped, it must flow, usually requiring worker assistance. The pouring of the mixture into the framework should be rapid and continuous. Once it’s in place, a vibrating screed is used to level off the fresh pavement, resulting in a smooth final surface. The vibrations increase the compaction, and therefore density, of the concrete.
Vibrating screeds also allow for the use of extremely thick, low-slump mixtures, which produce maximum strength and durability. Manual screeding methods lack the force necessary to smooth over such thickness.
>>Next Step: Compaction
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