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Slag Cement: Helping Concrete Perform Better

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Jan R. Prusinski, PE

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Slag Cement: Helping Concrete Perform Better

  1. 1. Jan R. Prusinski, PE Vice President of Marketing Skyway Cement Company Nebraska Concrete Paving Association 40th Annual Meeting January 22, 2019
  2. 2. Eagle Materials Cement Central Plains Cement Mountain Cement Nevada Cement Illinois Cement Fairborn Cement Skyway Cement Concrete and Aggregates Wallboard Proppants (Frac Sand) PortlandCementSlag Cement
  3. 3.  Non-metallic product of an iron blast furnace  Granulated  Ground  Cementitious material  Hydraulic cement Granules Slag Cement
  4. 4. Slag Diverted to granulator; quenched with high pressure water (6 - 10 tons water/ton slag) Molten slag floating on top of molten iron
  5. 5. Slag granule dewatering Slag granules Slag granule stockpiling
  6. 6. Roller Press Separator
  7. 7. Roman cements and concrete Aspdin patents portland cement Slag cement produced as a separate material ... 300-500 BC 1824 1950’s 2000’s Sparrow’s Point starts widespread use in Eastern U.S. Loriot makes slag- lime mortar 1774 1890’s First slag- portland blended cements 1982 Rapid expansion throughout U.S.
  8. 8. 3648 3110 0 500 1000 1500 2000 2500 3000 3500 4000 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017-F tons(000's) • Slag cement market share (compared to portland) has grown by 80% since 2000 • Slag Cement Association expects consumption to grow 3-5% over the next 5 years • SCA’s Western Region (including Nebraska) grew by 23% in 2017 2017 U.S. portland cement consumption: 96.8 M tons
  9. 9. Slag Cement + Water + Calcium Hydroxide From Portland Cement More Calcium- Silicate Hydrate Slag Cement + Water Calcium-Silicate Hydrate • Higher strength • Lower permeability • Greater durability
  10. 10. Portland Cement Concrete System Portland-Slag Concrete System Aggregate Portland Cement Slag Cement AggregateVoids Calcium Silicate Hydrate
  11. 11. Attribute Portland Cement Slag Cement Fly Ash Origin Limestone, Clay, etc. Iron blast- furnace slag granules Coal-fired electric power plant byproduct Production Manufactured product Manufactured product Byproduct Classification Hydraulic cement Hydraulic cement Pozzolan Typical Replacement Rates -- 25-50% (80% in mass conc.) 15-30% (50% in mass conc.) 2017 Use in Concrete 96.8 M tons 3.1 M tons 14.1 M tons
  12. 12. Constituent Portland Cement Slag Cement Class C Fly Ash Class F Fly Ash CaO 65 45 25 3 SiO2 20 33 37 58 Al2O3 4 10 16 20 Fe2O3 3 1 7 10 MgO 3 6 7 1
  13. 13. A 50% cement / 50% slag cement is compared to 100% Reference cement at the various ages. The reference cement used helps determine the grade of slag cement (Alkalies: 0.60 – 0.90% & 5,000 psi @ 28 days). The ASTM C989 spec allows for use of a “standard” reference cement.
  14. 14.  Reduced water demand  Better slump retention  Enhanced workability  Easier consolidation  Improved pumpability  Superior finishability  Consistent air content • Particles are dense and smooth • Little water is absorbed during initial mixing
  15. 15. 0 2 4 6 8 10 300 320 340 360 Water Content (lb/cy) Slump(in) 100%Portland 50%Slag Cement
  16. 16.  Slag Cement Mixes Set Slower in Colder Temperatures  Accelerators Can Speed Up Set Times Faster than 100% Portland Cement Mixes  Not Much Difference in Set Times at Higher Temperatures (+90oF)  Decreasing the w/cm with MRWR and HRWR will speed up the set time  Use T-III + Slag cement
  17. 17.  Improved Compressive and Flexural Strengths  Reduced Permeability  Improved Corrosion Resistance  Increased Resistance to Sulfate Attack and Alkali- Silica Reaction  Reduced Heat Generation • Particles are dense and smooth • Little water is absorbed during initial mixing
  18. 18.  Higher 28-day compressive strengths ◦ 1,000-2,000 psi higher  Lower early strengths  Typically matches portland strengths ~7 days  Optimum strength replacement ~35% 0 2,000 4,000 6,000 8,000 10,000 7 Day 28 Day Comp.Strength,psi 100% Portland 25% Slag 50% Slag 0 200 400 600 800 1,000 1,200 7 Day 28 Day FlexuralStrength,psi 100% Portland* 50% Slag**
  19. 19. 0 20 40 60 80 100 120 140 0 7 14 21 28 StrengthasPercentofTypeI at28days Age, days Type I Type IS(25)+15C Type IS(25)+15F Nominal Properties w/cm = 0.45 565 lbs/cu.yd. cementitious material slump 4” air content 6.5% Type I strength at 28 days = 6120 psi (42 MPa)
  20. 20.  For concrete exposed to deicing chemicals: ◦ Use good finishing practices (no premature finishing) ◦ Appropriate, timely curing essential ◦ Adequate air entrainment 4.5% to 7.5% air ◦ W/Cm ≤ 0.45 ◦ Compressive strength ≥ 4,500 psi Any concrete will be susceptible to deicer scaling if the surface is not finished and cured properly
  21. 21. SCM Used % Portland Replacement Average 14- day expansion % Expansion < 0.10? Class F Fly Ash 20% 0.1250 No Slag Cement 25% 0.1197 No Slag Cement 35% 0.0830 Yes  Buno Road, Michigan
  22. 22.  Reconstructed 7 miles of 8-lane freeway, 6 interchanges w on/off ramps  37 bridges rehabilitated or replaced  Slag cement used at over 30% to mitigate potential ASR and achieve specified flexural and compressive strengths  Lighter color enhances night time visibility  Consistent, reliable performance contributed to completion of project ahead of schedule
  23. 23.  Slag cement can mitigate sulfate attack in concrete by: ◦ Decreasing the total C3A in the system ◦ Decreasing the permeability of the concrete which prevents the ingress of sulfates into the concrete ◦ Reacting with calcium hydroxide to form CSH  Proper addition can: ◦ Type I+S => TII or TV ◦ Type II+S=> TV 50% slag in Na2SO4 OPC in water OPC in Na2SO4 OPC in MgSO4 OPC in K2SO4
  24. 24. 0.00 0.03 0.05 0.08 0.10 0 50 100 150 200 Expansion(percent) Days Type I Type II 20% Slag* 35% Slag* 50% Slag* Moderate Sulfate Resistance (6 months) High Sulfate Resistance (6 months) *With Type I Portland cement
  25. 25.  Denser hydrated cementitious structure  Reduced porosity  Decreased permeability  Greater durability
  26. 26. Item Original Final Portland Cement 658 lbs/yd3 306 lbs/yd3 Slag Cement 305 lbs/yd3 Fly Ash 282 lbs/yd3 Silica Fume 94 lbs/yd3 Coarse Aggregate - 1900 lbs/yd3 Fine Aggregate - 1176 lbs/yd3 Water - 28.5 gals/yd3 Admixture - 6 oz/cwt Air Entraining Agent - 0.6 oz/cwt Field Results Total cementitious reduced from 940 to 611 lb/cy 28-day compressive strength: 5,350 to 5,590 psi 56-day chloride permeability: 824 to 1,110 coulombs
  27. 27.  Slag cement makes whiter concrete  More reflective  Improved safety  Has been used to replace partially/fully white cement for some applications Portland Cement Slag Cement 0.540.53 0.50 0.62 0.46 0.6 0.64 0.69 0.63 0.20 0.30 0.40 0.50 0.60 0.70 Portland Fly Ash Slag Cement Slag + White Portland White Portland SolarReflectance
  28. 28.  Slower set time in colder temperatures  Lower early strengths precast, pipe, masonry accelerated curing  Potential deicer salt scaling at higher replacements (+25%) due to slower set times and slower bleeding  Additional silo space (blended cement can help)  Greening – goes away over time (oxidizes)
  29. 29. • Rehab asphalt runway with 18” concrete pavement overlay • Runway extended by 700’ and widened by 50’ to provide 12,700 ft by 200 ft new runway • Concrete Specifications • 700 psi min 28-day flexural • 550 lb/cy max cementitious • Mixture • ASTM C595 Type IS (40) slag blended cement • 4-aggregate mixture yielded • 1,300 psi flexural strength at 28-days • Improved strength, durability and smoothness
  30. 30.  Concrete mixture with 40% slag cement  2015-2018  Average flex strength > 900 psi
  31. 31. Cement/Slag Cement 50/50 40/60 Cement (lbs) 282 226 Slag Cement (lbs) 282 338 Total Cementitious (lbs) 564 564 Sack Content 6 6 Coarse Aggregate (lbs) 1920 1920 Fine Aggregate (lbs) 1260 1260 Water (gals) 34 34 Air (oz/cwt) 6 6 WRDA (oz/cwt) 3 3 Slump (inches) 5 5 Air Content (%) 4 - 6 4 - 6 7 Day (psi) 2220 2600 28 Day (psi) 4560 4740 56 Day (psi) 4740 5250 0 1000 2000 3000 4000 5000 6000 7 Day (psi) 28 Day (psi) 56 Day (psi) Strength(psi) Age (Days) 50/50 40/60
  32. 32.  30% slag cement  Built 2004  Project engineer: HWS  Finishers: excellent workability at low w/cm and low slump
  33. 33.  13,000 cy  Gehring Construction and Ready Mix  Colorado Structures  Parking lot  And city street around Walmart
  34. 34. 20-35%, with some C Ash (2004) East Granville St. Memorial Park Dr. 47 B Mixtures 28 Day 56 Day 20% Slag 5,522 6,112 30% Slag 5,708 6,165 35% Slag 5,837 6,272 30/20 Slag/C Ash 5,896 6,691
  35. 35.  Jan R. Prusinski, PE ◦ 832-265-7130 cell ◦ Jprusinski@skywaycement.com  Joel Sedlacek ◦ 402-305-3709 ◦ jsedlacek@centralplainscement.com  Megan Dangel ◦ 918-896-0598 ◦ mdangel@centralplainscement.com

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