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  • State of the Art of Shotcrete Technologies; Experiences and References Markus Jahn, Corporate Product Engineer, Sika Services AG

  • Content

    Global Trends

    Requirements on Shotcrete

    Accelerator Development

    Case Studies



  • Working mechanism shotcrete


    A) fills joints and evens out irregularities of the substrate

    B) its flexural strength prevents blocks from falling out

    C) seals, that prevents water from washing out fines and small rocks

    D) supports the rock mass by arching effect

    E) builds a beam/panel effect with the rock bolts

    Source: Sprayed Concrete for Rock Support, no. 7, Norwegian Concrete Association

  • 5 Markus Jahn Shotcrete

    Tunneling & Mining Process: dense-flow Output: 15-25 m3/h Agg. Size 12 mm Rebound: < 15 % Accelerator: 25-35 kg/m3

  • 6 Markus Jahn Shotcrete

  • 7 Markus Jahn Shotcrete

  • 8 Markus Jahn Shotcrete

  • Global Shotcrete Trend

    Ordinary Portland cement Blended cement CO2 and cost

    500 kg/m3 binder 400 kg/m3 binder CO2 and cost

    Alkaline Accelerator Alkali free Accelerator EH&S and durability

    Solutions Suspensions Cost efficient

    Steel mesh Fibre reinforced Cost efficient

    Steel fibres Macro synthetic fibres Cost efficient /


    General Solution Customized Solution Sharper optimization

    Penetrometer / Hilti Ultra sound measurement Reliability

  • Requirements on Shotcrete

    Fast setting No negative impact on 28 d compressive strength High durability Few rebound Good bonding to substrate High energy absorbtion Sustainable Cost-performance optimized Austrian Shotcrete Guideline : The compressive strength of shotcrete should fulfill: 0.1-0.2 N/mm2 at 2 minutes for building up layers overhead 0.2 N/mm2 at 2 minutes for reducing dust and rebound

  • Source: Testing Gallery Hagerbach, Switzerland

    High aggregate surface Compressive strength development

    Bonding to the substrate

    Smaller hose diameters

    High Binder Content Why?

  • Challenges in the Future

    New Mix Designs Reduced clinker content

    Sustainability (CO2 reduction)

    Tunnel maintenance (sintering)

    Cost reduction (clinker, high costs)

    High activities in development of shotcrete admixtures and additives

  • Product Year Chemical basis Appearance

    Sigunit Silicate Powder; akaline

    Sigunit-L Silicate Solution; alkaline

    Sigunit-L20 1985 Aluminate Solution; alkaline

    Sigunit-49 AF 1994 Aluminumsulphate Powder

    Sigunit-L50 AF 1995 Aluminumsulphate Solution

    Sigunit-L53 AF 1996 Aluminumhydroxi-sulphate Solution

    Sigunit-P1 AF 2000 Aluminumhydroxi-sulphate Instant

    Sigunit-L72 AF 2007 Aluminumsulphate Solution

    Sigunit-L83 AF 2009 Aluminumhydroxi-sulphate Solution

    Sigunit-L93 AF 2011 Aluminumsulphate Suspension

    Sigunit-P10 AF 2012 Aluminumhydroxi-sulphate Instant

    Sigunit-L87 AF 2013 Aluminumhydroxi-sulphate Solution

    Sigunit L-5601 AF 2014 Aluminumsulphate Suspension

    Sigunit L-5401 AF 2015 Aluminumsulphate Suspension

    Sigunit L-2301 AF 2015 Aluminumhydroxi-sulphate Solution

    Sigunit-39 AF 2015 Aluminumsulphate Powder

    Sigunit-59 AF 2015 Aluminumhydroxi-sulphate Powder

    Sigunit L-5710 AF 2015 Aluminumhydroxi-sulphate Solution

    Sigunit-P20 AF 2015 Aluminumhydroxi-sulphate Instant

    Sigunit L-5602 AF 2016 Aluminumsulphate Suspension

    Sigunit L-5711 AF 2016 Aluminumhydroxi-sulphate Solution 13

  • ultra sound spectrometer which determines the shear modulus as a measure of the strength evolution, non-destructive and continuously.

    Sika MiniShot

  • Development of taylor-made shotcrete admixtures

    Creating cost-performance optimized shotcrete mix designs

    Quality control for running construction projects

    Sika MiniShot

  • New Shotcrete Accelerator stand for

    Better cost-performance, due to Optimized production Better logistics New formulations Improved performance No negative impact to durability and final compressive strength Higher stability


    Perform with local cement types Harmonize with local admixtures and additives

    More respect in terms of EH&S

    Do not attack human tissue Environment-friendly Reduced leaching

  • 17

    Products Type Effect

    Sigunit Accelerator High early strength

    Sika ViscoCrete Superplasticizer Water reducing

    SikaTard Retarder Long workability



    Macro fibers

    Silica fume

    Energy absorption

    High final strength

    SikaPump-Start 1 Lubricant agent Avoids blockages

    SikaShot-3 Ready mix gunite High accelerated shotcrete

    SikaTell Colloidal SiO2 Rebound reduction

    FlexoDrain Flexible channels Water drainage system

    Aliva Equipment Rotor machines Application devices

    Sika-PM Shotcrete pumps Application devices

    SikaCare Paraffin oil Equipment protection

  • Kiruna Mine, Sweden Requirements: 4 MPa at 4h

    28 d strength > 40 MPa

    Accelerator dosage < 10%

    Accelerator stability > 6 months

    Open time > 4h

    Energy absorption according to ASTM 1550-05 of 490 J

    Sikament EVO 26S Superplastcizer (HRWR)

    SikaTard-930 Consistency stabilizer

    Sigunit-L53 AF (CC) Shotcrete accelerator

    Sika FastMix 225 HRWR (powder)

  • Gotthard Base Tunnel, Switzerland Requirements: Early strength: J2

    Final strength: B 40/30

    Aggregates: 0-8 mm

    Workability time: 4-8 hrs

    Exposure class: XA2

    Sika ViscoCrete Superplasticiser

    Sigunit Shotcrete Accelerator

    SikaTard-930 Long Time Retarder

    Sika-PM Shotcrete Spraying System

    Aliva TBM-Robotor

    SikaPlan Waterproofing Membrane

    Sikacrete Fire Protection Mortar

  • Brenner Base Tunnel, Italy Requirements: SpC 30/37 (28) II/J2 XC2 XF1

    GK8 F59

    w/c-ratio: 0.50

    Open Time: 60 min

    Compressive Strength after 48 hrs: 10 MPa

    Compressive Strength after 28 d: C 30/37

    Sigunit-L53 AF Accelerator

    Sigunit-LT Accelerator

    Sika ViscoCrete SC-305 BBT Superplasticizer

    Sika-PM 500 Spraying Equipment

    SikaPump-Start 1 Lubrication agent

    Aliva FlexoDrain W Drainage System

  • Karanjukar, Iceland Requirements: Early strength: J2

    Final strength: C 32/40

    Aggregates: 0-8 mm

    Workability time: 2-4 hrs

    Exposure class: XC2, XF3

    Sika ViscoCrete SC-305 Superplasticizer

    SikaTard-930 Retarder

    Sigunit-P1 AF Accelerator

  • Milk Milk Powder

    Liquid Accelerator Instant Accelerator


    Sigunit-P1 AF Extremely long shelf life No transportation of water Easy and fast just-in-time production High performance

    Tailor-made Solutions

  • 23

    Sweden India Australia

    Mixing of Sigunit-P1 AF

  • Nassau, Germany Requirements: C 25/30

    Early Strength Class: J2

    Minimal Working Space: 2 m

    Open Time: ca. 24h

    Delivery Distance (thin-flow): 100 300 m

    Exposition Classes: XC4 / XF1 / XA1

    SikaTard-930 Retarder

    Sigunit-L93 AF Accelerator

    Aliva-263 Application System

  • Supplementary Services from the Industry

    Mix design development


    Education / Trainings

    Quality Management



  • Troubleshooting of highly optimized systems

  • Troubleshooting: Who is Guilty?

  • Quality Management

    Cement chemistry: Shotcrete performance-testing based on all chemically relevant factors from site: cement, fines (from sand & aggregates), batching water, Sigunit and ViscoCrete (MiniShot)

    Cement fineness and particle size distribution: Blaine value, specific surface area (BET) and particle size analysis (Laser Granulometry)

    Chemical analysis of the cement (chemical composition & mineralogy)

    1st at the beginning of the project

    2nd when troubles occur

  • Sika Academy

    Shotcrete Training

    Mix designs

    Quality management


    Supplementary products

    Nozzleman Training

    Application according to EFNARC

    Equipment maintenance

    EFNARC diploma for experienced nozzlemen

  • Shotcrete Quality

    Stop layering / lamination:

    Well-maintained equipment

    Dont go to the limit of the machine.

    Use always a free flowing concrete.

    Spray only when hopper is more than full.

    Place equipment always as horizontally as


    Clean always the injector holes before spraying.

    Apply shotcrete according to the spraying rules.

  • Conclusion

    1. Shotcrete is a technology in change regarding mix design and quality measurement.

    2. Clients demand for more than only products. They want solutions and support.

    3. As more optimized the technology as more sensitive against fluctuating parameters

  • 32

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