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
• Support
• Troubleshooting
Working mechanism shotcrete
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 /
durability
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
Tailor-made
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
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Products Type Effect
Sigunit® Accelerator High early strength
Sika® ViscoCrete® Superplasticizer Water reducing
SikaTard® Retarder Long workability
SikaFiber®
SikaFume
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
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Sigunit-P1 AF • Extremely long shelf life • No transportation of water • Easy and fast just-in-time production • High performance
Tailor-made Solutions
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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
Troubleshooting
Education / Trainings
Quality Management
Guidelines
Logistics
…
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
Troubleshooting
Supplementary products
Nozzleman Training
Application according to EFNARC
Equipment maintenance
EFNARC diploma for experienced nozzlemen
Shotcrete Quality
Stop layering / lamination:
Well-maintained equipment
Don’t go to the limit of the machine.
Use always a free flowing concrete.
Spray only when hopper is more than ¾ full.
Place equipment always as horizontally as
possible.
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
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https://www.youtube.com/watch?v=_gxF7-6dkZY