Shotcrete Quality Control and Testing for an Underground Mine in Canada

By Dudley R. (Rusty) Morgan

andMazin Ezzet

AMEC Earth & Environmental, a division of AMEC Americas Limited

SHOTCRETE FOR AFRICA CONFERENCEMisty Hills Conference Centre

South Africa2-3 March, 2009

Subject of Presentation

General IntroductionStandards and CodesShotcrete Materials Requirements

– Cementing Materials– Aggregates– Mixing Water– Chemical Admixtures

Shotcrete Performance Requirements

Subject of Presentation (continued)

Quality Control Testing– Aggregates– Batching and Supply (Plastic Shotcrete)– Hardened Shotcrete

Shotcrete Quality Control Organizational Chart

New Underground Gold Mine in British Columbia

Portal at Decline into Underground Mine

Mobile Mass Batcher Unit Discharging into Ready-Mix Concrete Truck

Remixer Unit for Hauling Shotcrete Down Decline

Remixer Unit Discharging into Shotcrete Pump at Back of Shotcrete Sprayer

Remote Control Shotcrete Sprayer

Manipulator Arm on Remote Control Shotcrete Sprayer

Shooting ASTM C1550 Round Test Panels

Ready for Shotcreting Underground

Drilling Face for next Round of Blasting

Note Shotcrete with Bolts and Plates

Standards and Codes

American Concrete Institute (ACI)

American Society for Testing and Materials (ASTM)

Canadian Standards Association (CSA)

National Ready Mix Concrete Association (NRMCA)

Concrete Plant Manufacturer’s Bureau (CPMP)

Standards and Codes

Standard Test Method for Obtaining and Testing Drilled Cores of Shotcrete

ASTM C1604

Standard Specification for Mixing Water Used in Production of Hydraulic Cement Concrete

ASTM C1602

Standard Specification for Flexural Toughness of Fibre Reinforced Concrete (Using Centrally Loaded Round Panel)

ASTM C1550

Standard Specification for Materials for ShotcreteASTM C1436

Specification for Admixtures for ShotcreteASTM C1141

Standard Practice for Preparing and Testing Specimens from Shotcrete Test Panels

ASTM C1140

Specification for Fibre Reinforced ConcreteASTM C1116

Standard Test Method for Specific Gravity, Absorption, and Voidsin Hardened Concrete

ASTM C642-82

Standard Test Methods for Chemical Analysis of Hydraulic Cements

ASTM C114

Standards and Codes (continued)

Cementitious Materials for Use in ConcreteCSA A3001-03

Methods of Test and Standard Practices for ConcreteCSA A23.2-04

Concrete Materials and Methods of Concrete ConstructionCSA A23.1-04

Canadian Standards Association (CSA)

Specifications for Materials Proportioning and Application of Shotcrete

ACI 506.2-95

Guide to ShotcreteACI 506R-05

American Concrete Institute (ACI)

Shotcrete Materials

Cementing Materials– Portland Cement: CSA Type GU– Fly Ash: CSA Type F or CI– Silica Fume: CSA Type SF

Other Cementing Materials– Natural Pozzolans– Calcined Metakaolins– Ground Granulated Blast Furnace Slag

Limits for Deleterious Substances and Physical Properties of Aggregates

1216MgSO4 soundness lossA23.2-9A

50-Impact and abrasion lossA23.2-16A

6-Unconfined freeze-thaw testA23.2-29A

1720Micro-Deval testA23.2-23A

20-Flat and elongated particles Procedure A, ratios 4:1

A23.2-13A

1.03.0Material finer than 80 µmA23.2-5A

0.50.5Low-density granular materialsA23.2-4A

0.251Clay lumpsA23.2-3A

Coarse Aggregate

Fine AggregateStandard RequirementsCSA Test Method

Maximum Percentage byMass of Total Sample

Property

Grading Limits for Fine Aggregate

0-380 µm

2-10160 µm

10-35315 µm

25-65630 µm

50-901.25 mm

80-1002.5 mm

95-1005 mm

10010 mm

FA1Sieve Size

Total Passing Sieve, Percentage by Mass

Grading Limits for Coarse Aggregate

0-51.25 mm

0-102.5 mm

10-305 mm

85-10010 mm

10014 mm

Total Passing Sieve, Percentage by MassNominal Size of Aggregate

Grading Limits for Combined Aggregates

0-380 µm

2-10160 µm

8-20315 µm

20-35630 µm

35-551.25

50-702.5 mm

70-855 mm

90-10010 mm

10014 mm

Total passing sieve, percentage by massSieve Size

Graph of ACI No. 1 & No. 2 Gradings

0

20

40

60

80

100

120

0.08 0.16 0.315 0.63 1.25 2.5 5 10 14

Metric Sieve Size

Perc

ent P

assi

ng

ACI Gradation 1 Limits

ACI Gradation 2 Limits

Combined % Passing

Chemical Limits for Mixing Water

C160350,000Total solids by mass

C114600Alkalies as (Na2O + 0.658 K2O)

C1143000Sulphate as SO

C1141000Chloride as Cl

ASTM Test MethodLimitsMaximum Concentration In Mixing Water, ppm

Chemical Admixtures

Water Reducing AdmixturesSet Retarding or Hydration Controlling AdmixturesAir Entraining AdmixturesSet Accelerators Added at Nozzle

Fibres

Steel Fibres: ASTM C1116 Type I and ASTM A 820

Synthetic Fibres: ASTM C1116 Type III

Typical Shotcrete Performance Requirements

2 MPaMinimum early age compressive strength before re-entry under shotcrete

Penetrometer as calibrated against beams tested as

equivalent cubes

*Minimum Joules energy at 40 mm deflection in round panel test

ASTM C1550

9 %18 %

Maximum values of boiled absorptionMaximum volume of permeable voids

ASTM C642

10MPa30 MPa40 MPa

Minimum compressive strength of shotcrete cores

1 Day7 Days28 Days

ASTM C1604 & CSA A23.2 –14C

2-5 %Air content – as shotCSA A23.2 – 4C

10-30oCTemperature(at discharge into shotcrete pump)

-

170 ±20 mmSlump(at discharge into shotcrete pump)

CSA A23.2 – 5C

0.40Maximum water/cementing materials ratio-

Performance RequirementPropertyTest Method

Fibre Reinforced Shotcrete Testing in North America

Steel fibre synthetic macro-fibre reinforced shotcrete in NorthAmerica has been tested to the following ASTM Standards:

ASTM C1018: Standard test method for flexural toughness and first-crack strength of fiber-reinforced concrete (using beam with third point loading) first published 1984, withdrawn 2006

ASTM C1609: Standard test method for flexural performance of fiber-reinforced concrete (using beam with third point loading) first published 2005

ASTM C1550: Standard test method for flexural toughness of fiber reinforced concrete (using centrally loaded round panel)

ASTM C1018 and ASTM C1609 Beam Test

ASTM C1018 Load vs Deflection Curve

Test Results Include:– First crack and ultimate flexural strengths (MPa)– Toughness Indices I5, I10, I20, etc– Residual Strength Factors R5,10, R10,20, etc.

Problems of reliability with this test method and withdrawn in 2006

Fibre Shotcrete Tests

Flexural Toughness Performance LevelsMorgan and Chen, 1995

Fibre Shotcrete Beam Tests

ASTM C1609 Load vs Deflection Curve

ASTM C1550 Round Panel Test

ASTM C1550 Round Panel Test

Technical Report

Typical Shotcrete Mixture Design

1.0105Yield (m3) =2354Total

0.0202-2.0At Shot (%)

--2.5Air Content:At Pump (+/- 1.5%)

0.00669106.0Macro Synthetic Fibre

0.001210001.2Hydration Controlling Admixture, L

0.002510002.5High Water Reducing Admixture, L

0.18501000185Estimated Water, L

0.494526491310Fine Aggregate (SSD)

0.13852744380Coarse Aggregate (10-2.5mm, SSD)

0.0205220045Silica Fume

0.13653150430Cement Type GU

Volume[m3]

Density [kg/m3]

Mass per m3 SSD Agg [kg]Material

Shotcrete Quality Control Certification and Testing

AggregatesBatch PlantMixersPlastic ShotcreteHardened Shotcrete

Shotcrete Aggregates Testing Frequency

Each daySurface Moisture in Fine and Coarse AggregatesA23.2-11A

6 monthsRelative Density and Absorption of Coarse AggregateA23.2-12A

1 weekOrganic Impurities Colour TestA23.2-7A

6 monthsRelative Density and Absorption of Fine AggregatesA23.2-6A

Each deliverySieve Analysis of Fine and Coarse AggregatesA23.2-2A

1 yearAlkali Silica ReactivityA23.2-25A

1 yearPetrographic AnalysisA23.2-15

6 monthsMgSO4 Soundness LossA23.2-9A

6 monthsImpact and Abrasion LossA23.2-16A

6 monthsUnconfined Freeze-thaw TestA23.2-24A

6 monthsMicro-Deval TestA23.2-23A

6 monthsFlat and Elongated ParticlesA23.2-13A

1 weekMaterial Finer than 80 µmA23.2-5A

6 monthsLow Density Granular MaterialsA23.2-4A

6 monthsClay LumpsA23.2-3A

Testing FrequencyPropertyCSA Test Method

Shotcrete Batching and Supply Certification and Testing

Each batch of shotcrete produced

Batch records with solid materials in kg and liquids in L

NRMCA CPMB 100 M-07

Before use and every 6 months

Certification of ready mix concrete truck mixers and remixer units

NRMCA CPMB 100 M-07

At start of project and every 2 years

Certification of ready mixed concrete production facilities using truck mixing

NRMCA CPMB 100 M-07

Testing FrequencyTest ProcedureTest Method

Plastic Shotcrete QC Testing

At start of project and with any change in fibre type or dosage

Wash-out test to determine uniformity of fibre distribution at discharge from remixer unit

CSA A23.2-7C Modified

At start of project and with any change of mixture proportions

Air Content as-shot (without accelerator)

CSA A23.2-7C Modified

At start of project and with any change in mixture proportions

Air content of plastic shotcrete at discharge into remixer unit and at shotcrete pump

CSA A23.2-7C

Each batch of shotcrete produced

Shotcrete and ambient temperatures at discharge into remixer unit and at shotcrete pump

At beginning of each shiftSlump at discharge into shotcrete pump

CSA A23.2-5C

Each batch of shotcrete produced

Slump at discharge into remixer unitCSA A23.2-5C

Testing FrequencyTest ProcedureTest Method

Hardened Shotcrete QC Testing

Two panels at 28 days for each week of shotcrete production or at any change in fibre type or dosage

Round panel test to 40 mm deflectionASTM C1550

Two panels at each of ages 7 and 28 days at start of project for one fibre type and dosage

Round panel test to 40mm deflectionASTM C1550

One heading per week for each shotcrete robot used

Boiled absorption and volume of permeable voids

ASTM C642

One heading per week for each shotcrete robot and each shotcrete crew used

Compressive strength of cores extracted from shotcrete test panel at age 1 day (1 core), 7 days (1 core) and 28 days (2 cores)

ASTM C1140ASTM C1604

One heading per shiftEarly age compressive strength estimate using penetrometer

Penetrometer

At start of project and with any change in mixture proportions or accelerator type or dosage

Early age compressive strength of beams as equivalent cubes

Ref. 1

Testing FrequencyTest DescriptionTest Method

Quality Assurance Plan

Shotcrete Quality Control– Shotcrete Materials Check List– Inspection and Test Plan (ITP)

a) Materialsb) Batching and Supplyc) Hardened Shotcrete

Shotcrete Quality Audit– Non-conformance Report (NCR)– Opportunity for Improvement Report (OFI)– Corrective Action Report (CAR)– Audit Report

Conclusions

Production of quality shotcrete in an undergroundenvironment requires:

Rigorous shotcrete specificationsImplementation of a quality management plan (follow ISO 9000 approach)Pre-production qualification of all materials and shotcrete mixture designImplementation of a systematic quality control inspection and testing plan for the aggregates, mix water and plastic and hardened shotcreteUse of nozzlemen and shotcrete batching, supply and application crew properly trained and qualified