Changes

|Thickness (mm)||This is the thickness of just the pre-cast blocks (or depth of asphalt/concrete poured in place).

|Thickness (mm)||This is the thickness of just the pre-cast blocks (or depth of asphalt/concrete poured in place).

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|Void ratio||This most commonly refers to the jointing material used between precast blocks. Suggest 0.35 unless otherwise tested. Where a pervious product is poured in place, an appropriate figure should be obtained from the manufacturer.

|Void ratio||This most commonly refers to the jointing material used between precast blocks. Suggest 0.4 unless otherwise tested. Where a pervious product is poured in place, an appropriate figure should be obtained from the manufacturer.

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|Impervious surface fraction||This is the proportion of the total pavement taken up with the pre-cast blocks and will vary between products; an example value may be 0.85.  

|Impervious surface fraction||This is the proportion of the total pavement taken up with the pre-cast blocks and will vary between products; an example value may be 0.85.  

|Thickness (mm)||Depth of bedding layer

|Thickness (mm)||Depth of bedding layer

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|Porosity (fraction)||Suggested range 0.35 – 0.4 unless otherwise tested

|Porosity (fraction)||Suggested range 0.4 unless otherwise tested

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|Field capacity (fraction)||Suggested range 0.10 - 0.12 for sand<ref name = SWMM/>

|Field capacity (fraction)||Suggested range 0.10 - 0.12 for sand<ref name = SWMM/>