I.S. 398 GEOLOGICAL TESTING PROCEDURES, RESULTS and BACKGROUND

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1 I.S. 398 GEOLOGICAL TESTING PROCEDURES, RESULTS and BACKGROUND EurGeol Dr John Kelly, PGeo, MIMMM, MIQ Engineers Ireland 5 th November 2013

2 SWELLING RISK BASICS Pyrite is a form of iron sulphide (FeS 2 ), other forms include pyrrhotite and marcasite. It is a naturally occurring, common and widespread mineral found in many (most) rock types Sulphide minerals may render a rock an unsuitable (swelling) construction material if: Rock is weak and/or foliated (thinly layered) Rock has low resistance to fragmentation Rock has high water absorption Sulphides are present in sufficient quantities Sulphides are reactive Sulphides are exposed to water and air (oxygen)

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4 Pyrite Oxidation - Summary 2FeS 2 + 2H 2 O + 7O 2 2FeSO 4 + 2H 2 SO 4 4FeSO 4 + O 2 + 2H 2 SO 4 2Fe 2 (SO 4 ) 3 + 2H 2 O Fe 2 (SO 4 ) 3 + 6H 2 O 2Fe(OH) 3 + 3H 2 SO 4 + Bacteria incl. Acidithiobacillus ferrooxidans In calcareous rocks (i.e. rocks containing calcium carbonate) the carbonate - acid reaction leads to gypsum formation H 2 SO 4 + CaCO 3 CaSO 4 + CO 2 + H 2 O If the rock is weak and the amount of gypsum formation is excessive, expansion of the rock will occur. The reaction will then continue as fresh pyrite is exposed to more air and water by expansion or if the rock is highly water absorbent

5 45mm

6 TEST SUITES TEST SUITE 0 GEOLOGICAL INSPECTION CHEMICAL TESTING TEST SUITE 1 AS SUITE 0 PLUS MINERALOGY by XRD TEST SUITE 2 AS SUITE 0 and 1 PLUS DETAILED PETROGRAPHY WATER ABSORPTION TESTING

7 TEST SUITE 0 TEST SUITES GEOLOGICAL INSPECTION Basic geological inspection of the recovered material to determine if the sample contains noncompliant rock types (mudstones, siltstones, shales, argillaceous limestones etc.) which have a swelling risk CHEMICAL TESTING Total sulfur Acid soluble sulfate Water soluble sulfate Pyrite estimation

8 TEST SUITES TEST SUITE 0 PASS LIMITS GEOLOGICAL INSPECTION Lithology is non-argillaceous No evidence of secondary gypsum CHEMICAL TESTING Total sulfur 0.3%S Acid soluble sulfate 0.2% Water soluble sulfate 500mg/l SO 4

9 TEST SUITES TEST SUITE 1 X-RAY DIFFRACTION ANALYSIS Determines mineralogical content of the sample MUST BE QUANTITATIVE XRD can be qualitative or quantitative NEED NUMBERS DETECTION LIMITS Depending on mineralogy may be 0.5% - 2.0%

10 LITHOLOGICAL DETERMINATION XRD Analysis - Summary Carbonates Material 01 Material 02 Material 03 Material

11 LITHOLOGICAL DETERMINATION XRD Analysis - Summary Phyllosilicates Carbonates Material 01 Material 02 Material 03 Material

12 LITHOLOGICAL DETERMINATION XRD Analysis - Summary Quartz Phyllosilicates Carbonates Material 01 Material 02 Material 03 Material

13 LITHOLOGICAL DETERMINATION XRD Analysis - Summary Feldspars Quartz Phyllosilicates Carbonates Material 01 Material 02 Material 03 Material

14 LITHOLOGICAL DETERMINATION XRD Analysis - Summary Pyrite Feldspars Quartz Phyllosilicates Carbonates Material 01 Material 02 Material 03 Material

15 LITHOLOGICAL DETERMINATION XRD Analysis - Summary Pyrite Feldspars Quartz Phyllosilicates Carbonates Material 01 Material 02 Material 03 Material

16 LITHOLOGICAL DETERMINATION Quartz and Feldspars Phyllosilicates (Clay Minerals) Carbonates

17 TEST SUITE 1 PASS AND FAIL LIMITS TEST SUITES XRD RESULTS GYPSUM PRESENT? NO YES ARGILLACEOUS CONTENT 10% > 30% CHEMICAL TESTING Total sulfur 0.3 > 1.0 % S Acid soluble sulfate 0.2 > 0.2 % Water soluble sulfate 500 > 1500 mg/l SO 4

18 TEST SUITES TEST SUITE 2 PETROGRAPHIC / DETAILED GEOLOGICAL ANALYSIS Determines detailed lithology and mineralogical characteristics of the sample PETROGRAPHER / GEOLOGIST MUST BE COMPETENT Qualified professional geologist (IGI - PGeo, GSL - CGeol, EFG - EurGeol etc.) with relevant experience WATER ABSORPTION TEST

19 TEST SUITE 2 TEST SUITES PETROGRAPHIC ANALYSIS MINERALOGICAL IDENTIFICATION Amount and form of any pyrite present i.e. reactive or non-reactive forms Evidence of pyrite reaction Presence and nature of clay minerals Presence of carbonate Presence, form and distribution of gypsum primary or secondary and any evidence for expansion Rock structure and assessment of poroperm

20 Euhedral Cubic Pyrite Fine Pyrite Coarse Pyrite 5mm

21 5mm

22 TEST SUITE 2 WATER ABSORPTION TEST SUITES Tests ability of the material to absorb and transmit water and air Weak, water absorbent material will transmit water and air to pyrite contained deep within the rock material

23 TEST SUITE 2 PASS AND FAIL LIMITS TEST SUITES PROFESSIONAL OPINION OF THE CONSULTANT GEOLOGIST BASED ON SUITE 0 TESTING, XRD, PETROGRAPHY AND WATER ABSORPTION RESULTS MUST CONSIDER Lithology, rock strength, clay content, pyrite content, nature of pyrite, evidence of pyrite oxidation, presence of secondary gypsum, nature of rock particles, porosity and permeability, moisture content, other sulfides

24 TEST SUITE 2 PASS AND FAIL LIMITS TEST SUITES WATER ABSORPTION Existing standards set upper limit at 2.0% or Magnesium Sulfate Soundness (MSS) of <25% if WA slightly > 2.0% Now set at 2.0% AND MSS of <25% Values obtained inform geologists opinion

25 TEST SUITE 2 PASS AND FAIL LIMITS TEST SUITES PROFESSIONAL GEOLOGIST CLASSIFIES MATERIAL AS: Pass Not susceptible to expansion Inconclusive Susceptible to limited expansion Fail - Susceptible to significant expansion

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