corrosivity of soils

7/27/2019 Corrosivity of Soils

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Controlled Document: CT.Env.XX [TECHNOTE/Corrosivity of Soils] Version: Draft, Issue Date 9/1/12 Issuing Officer: P G Robinson

New Zealand Accredited Laboratory Member of the New Zealand Association of Consulting Laboratories

Corrosivity of Soils/Groundwater –

Testing for construction purposes

Soils which come into contact with construction materials may be corrosive, either to concrete or reinforcing

steel, leading to failure of the structure or necessitating special design considerations.

There are a variety of tests which may be carried out for soil corrosivity., and there are a number of different

Standard Methods which may be used, see list at the end of this Technical Note.

Because of the many possible different test methods, based on Standards from different parts of the world,

Hill Laboratories is offering only a limited number of tests for each analyte. The test methods we have

selected are either the ones found in NZ Standard requirements (eg NZS 3101), or ones which has most

commonly been requested by our clients.

The methods tend to be very labour intensive, and often include ‘difficult’ preparation steps such as filtering

large volumes of solution in which a finely ground soil has been suspended in an extracting solution – which

does not happen quickly or easily, so necessitates at least overnight settling of samples before filtration or

centrifugation. This means it is not possible to process these analyses under Urgent or High Priority.

Results are usually compared (by the client) to a suitable reference eg NZS 3101: Part 1 2006





Hill Labs Methods – Soils

Sample preparationTest Description Method Ref

Drysieve Air dry at 35C in a forced air oven, pass through a 2mm

sieve

Sieve425um Pass the above dried sample through a 425um sieve

Synthetic Precipitation

Leaching Procedure

USEPA 1312

Physical tests [NOTE: The commonest tests are shown in blue,Test Description Method Ref

pH Sample is air-dried, 2mm sieved. 30 g sample + 75mL DI water(1:2.5 w:v), mixed, stand at least 8hr. Potentiometric

measurement of pH.

[BS 1377:Part 3:1990 section

Cation Exchange

Capacity

Chemical tests

Test Description Method Ref

ANC

NAPP

MPA

ANC = Acid Neutralising Capacity

NAPP = Nett Acid Production Potential

MPA = Maximum Potential AcidityCarbonate (High

leveltitrimetric method)

Sample is air-dried, 2mm sieved. Further ground to sub-425um.

5g + 100mL 1M HCl, stand 1hr, titrate 25mL with 1M NaOH

using screened methyl orange indicator.

BS 1377:Part 3:1990 section 6

Chloride Sample is air-dried, 2mm sieved. Further ground to sub-

90um.10g + 200mL DI water, boiled 15 min with stirring.

Settled, then an aliquot taken for potentiometric titration with

silver nitrate. DL 50mg/kg dry wt.

DIN 4030 Part 2, 1991 sectio





Acid soluble

sulphate

Sample is air-dried, 2mm sieved. Further ground to sub-

425um. 2G + 200mL 10% HCl, boil gently 4-5min. Add

bromine solution, then ammonium hydroxide. Precipitate as

BaSO4. Gravimetric determination. DL 0.1g/100g dry wt

NZS 4402:1986 Part 3, Test 3

Water soluble

sulphate

Sample is air-dried, 2mm sieved. Further ground to sub-425um.

50g:50mL DI water, ?16hrs, settle, filter or centrifuge. Add

bromine solution, then ammonium hydroxide. Precipitate as

BaSO4. Gravimetric determination. DL 0.1g/100g dry wt

NZS 4402:1986 Part 3, Test 3

1 in NZS)

Water soluble

sulphate

Sample is air-dried, 2mm sieved. Further ground to sub-

425um. 50g:100mL DI water, 16hrs, settle, filter or centrifuge.

Gravimetric as barium sulphate.

BS 1377:Part 3:1990 section

5.5

NB: Requires reporting as “S

!!!!

Organic matter Walkley Black Oxidation (Dichromate oxidation) hasinterferences from sulphides or chlorides. Mass Loss on Ignition

may have positive interferences from some non-organic sources

[BS 1377:Part 3: 1990.

Hill Laboratories has substituted TOC (Total Organic Carbon),

with a calculation to Organic Matter = TPC x 1.72 [Ref???] as

being a more reliable indicator of Organic Content

Baumann Gully

Acidity

Sample is air-dried, 2mm sieved. 100g extracted with200mL 1M

sodium acetate for 1hr. This produces acetic acid which is

titrated with standard NaOH using phenolphthalein indicator

DL 5mL 0.01M NaOH/kg dry wt

DIN 4030 Part 2, 1991 sectio

(modified for <2mm rather th

<90um sample)





Hill Labs Methods - Groundwaters

Physical tests


pH Hydrogen ion concentration, indicator of acidity/basicity

EC Electrical conductivity. Related to dissolved ions eg saltwater

Chemical tests


Filtration for Cl, SO4

Chloride

Sulphate

Filtration for Dissolved

Metals

(If not Field Filtered)

Dissolved magnesium 0.45um filtered sample, ICPMS





Relevant Standards

BS1377: Part 3: 1990 5.3.2.2 – 5.3.2.4 [Requires air drying, then sieving through 425um sieve]

“Methods of test for Soils for civil engineering purposes. Part 3. Chemical and electro-chemical tests”

DIN 4030 Part 2, June 1991 “Assessment of water, soil and gases for their aggressiveness to concrete.

Collection and examination of water samples”

NZS 3101.1&2:2006

Concrete structures standard - Concrete Structures Standard

NZS 4202 Part 3 1986

BS 8500 (and European Standard BS EN 206-1) “Concrete”, which links with BRE Special Digest 1

BRE Special Digest 1 “Concrete in aggressive ground” [UK Building Research Establishment Ltd,www.bre.co.uk]

Other references

Acid soluble chlorides in concrete

• ASTM C1152

• AS1012.20

• BS1881:124

Acid soluble chlorides in aggregate

• AS 1012.20

Water soluble chlorides in aggregate

• ASTM C1218

• BS EN 1744

Acid soluble sulphates in concrete

• AS 1012.20

• BS1881:124

Acid soluble sulphates in aggregate

•AS 1012.20

• BS EN 1744

Water soluble sulphates in aggregate

• BS EN 1744

corrosivity of soils

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