The Structural Engineer's Corner

Eng. Onorio Francesco Salvatore

Design for durability, part I – surface of members in contact with the ground

Written By: Lexatus - Oct• 19•13

Concrete durability - Onorio

Similarly to European Codes, the Australian Standards specify the durability requirements according to the exposure classifications. In the following, the requirements for the surface of members in contact with the ground.

  • Members protected by a damp-proof membrane;
    • Exposure classification = A1;
    • Minimum concrete strength, f’c = 20 MPa;
    • Minimum initial curing = continuously for at least 3 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 15 MPa;
    • Required cover where standard formwork and compaction are used = 20 mm.
  • Residential footings in non-aggressive soils;
    • Exposure classification = A1;
    • Minimum concrete strength, f’c = 20 MPa;
    • Minimum initial curing = continuously for at least 3 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 15 MPa;
    • Required cover where standard formwork and compaction are used = 20 mm
  • Other members in non-aggressive soils;
    • Exposure classification = A2;
    • Minimum concrete strength, f’c = 25 MPa;
    • Minimum initial curing = continuously for at least 3 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 15 MPa;
    • Required cover where standard formwork and compaction are used = 30 mm.
  • Members in aggressive soils with Sulfate bearing (magnesium content < 1 g/L), sulfates (expressed as SO4) in soil ppm <5000 or in groundwater ppm <1000, pH > 5.5, soil conditions with high permeability (e.g. sands and gravel) which are in ground water;
    • Exposure classification = A2;
    • Minimum concrete strength, f’c = 25 MPa;
    • Minimum initial curing = continuously for at least 3 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 15 MPa;
    • Required cover where standard formwork and compaction are used = 30 mm.
  • Members in aggressive soils with Sulfate bearing (magnesium content < 1 g/L), sulfates (expressed as SO4) in soil ppm <5000 or in groundwater ppm <1000, pH > 5.5, soil conditions with low permeability (e.g. silts and clays) or all soils above groundwater;
    • Exposure classification = A1;
    • Minimum concrete strength, f’c = 20 MPa;
    • Minimum initial curing = continuously for at least 3 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 15 MPa;
    • Required cover where standard formwork and compaction are used = 20 mm.
  • Members in aggressive soils with Sulfate bearing (magnesium content < 1 g/L), sulfates (expressed as SO4) in soil ppm between 5000 and 10 000 or in groundwater ppm between 1000 and 3000, pH between 4.5 and 5.5, soil conditions with high permeability (e.g. sands and gravel) which are in ground water;
    • Exposure classification = B1;
    • Minimum concrete strength, f’c = 32 MPa;
    • Minimum initial curing = continuously for at least 7 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 20 MPa;
    • Required cover where standard formwork and compaction are used = 40 mm.
  • Members in aggressive soils with Sulfate bearing (magnesium content < 1 g/L), sulfates (expressed as SO4) in soil ppm between 5000 and 10 000 or in groundwater ppm between 1000 and 3000, pH between 4.5 and 5.5, soil conditions with low permeability (e.g. silts and clays) or all soils above groundwater;
    • Exposure classification = A2;
    • Minimum concrete strength, f’c = 25 MPa;
    • Minimum initial curing = continuously for at least 3 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 15 MPa;
    • Required cover where standard formwork and compaction are used = 30 mm.
  • Members in aggressive soils with Sulfate bearing (magnesium content < 1 g/L), sulfates (expressed as SO4) in soil ppm between 10 000 and 20 000 or in groundwater ppm between 3000 and 10000, pH between 4.0 and 4.5, soil conditions with high permeability (e.g. sands and gravel) which are in ground water;

    • Exposure classification = B2;
    • Minimum concrete strength, f’c = 40 MPa;
    • Minimum initial curing = continuously for at least 7 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 25 MPa;
    • Required cover where standard formwork and compaction are used = 45 mm.
  • Members in aggressive soils with Sulfate bearing (magnesium content < 1 g/L), sulfates (expressed as SO4) in soil ppm between 10 000 and 20 000 or in groundwater ppm between 3000 and 10000, pH between 4.0 and 4.5, soil conditions with low permeability (e.g. silts and clays) or all soils above groundwater;

    • Exposure classification = B1;
    • Minimum concrete strength, f’c = 32 MPa;
    • Minimum initial curing = continuously for at least 7 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 20 MPa;
    • Required cover where standard formwork and compaction are used = 40 mm.
  • Members in aggressive soils with Sulfate bearing (magnesium content < 1 g/L), sulfates (expressed as SO4) in soil ppm > 20 000 or in groundwater ppm > 10 000, pH <4.0, soil conditions with high permeability (e.g. sands and gravel) which are in ground water;

    • Exposure classification = C2;
    • Minimum concrete strength, f’c = 50 MPa;
    • Minimum initial curing = continuously for at least 7 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 32 MPa;
    • Required cover where standard formwork and compaction are used = 65 mm.
  • Members in aggressive soils with Sulfate bearing (magnesium content < 1 g/L), sulfates (expressed as SO4) in soil ppm > 20 000 or in groundwater ppm > 10 000, pH <4.0, soil conditions with low permeability (e.g. silts and clays) or all soils above groundwater;

    • Exposure classification = B2;
    • Minimum concrete strength, f’c = 40 MPa;
    • Minimum initial curing = continuously for at least 7 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 25 MPa;
    • Required cover where standard formwork and compaction are used = 45 mm.
  • Members in aggressive soils with Sulfate bearing (magnesium content ≥ 1 g/L);
    • Exposure classification = U.
  • Other members in aggressive soils;
    • Exposure classification = U.
  • Salt rich soils and soils in areas affected by salinity with soil electrical conductivity between 4 and 8 deciSiemens per metre;
    • Exposure classification = A2;
    • Minimum concrete strength, f’c = 25 MPa;
    • Minimum initial curing = continuously for at least 3 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 15 MPa;
    • Required cover where standard formwork and compaction are used = 30 mm.
  • Salt rich soils and soils in areas affected by salinity with soil electrical conductivity between 8 and 16 deciSiemens per metre;

    • Exposure classification = B1;
    • Minimum concrete strength, f’c = 32 MPa;
    • Minimum initial curing = continuously for at least 7 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 20 MPa;
    • Required cover where standard formwork and compaction are used = 40 mm.
  • Salt rich soils and soils in areas affected by salinity with soil electrical conductivity >16 deciSiemens per metre;

    • Exposure classification = B2;
    • Minimum concrete strength, f’c = 40 MPa;
    • Minimum initial curing = continuously for at least 7 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 25 MPa;
    • Required cover where standard formwork and compaction are used = 45 mm.

 

For any issues or questions, you can contact the author at:

onorio@strutturista.com

Eng. Onorio Francesco Salvatore

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