Challenges and Opportunities

Transcription

1 Challenges and Opportunities Recycled Materials in Ready Mixed Concrete Concrete Sustainability Conference April 2010 Colin Lobo, Ph.D., P.E Concrete Sustainability Conference 1 National Ready Mixed Concrete Association

2 NRMCA Sustainability Initiatives Key Performance Indicators Potable water: 10% reduction by % reduction by 2030 Waste: 30% reduction by % reduction by 2030 Recycled content: t 200% increase by % increase by Concrete Sustainability Conference 2 National Ready Mixed Concrete Association

3 Recycled Content: Where are we today? 0 50% 20% 9% by volume? 0% Increase 200% ~30% by volume? 2010 Concrete Sustainability Conference 3 National Ready Mixed Concrete Association

4 NRMCA Sustainability Initiatives Potable water: 10% reduction by 200% increase by % reduction by 400% increase by Recycled content: Waste: 30% reduction by % reduction by Concrete Sustainability Conference 4 National Ready Mixed Concrete Association

5 Cementitious Materials Supplementary Cementitous Materials Improve fresh concrete properties Strength Durability Good history of use Credit in Green Rating Systems Pre-consumer waste 2010 Concrete Sustainability Conference 5 National Ready Mixed Concrete Association

6 Cementitious Materials Challenges Specifications Maximum limit Minimum limit reduce carbon footprint Restrictions products and properties Performance Setting Rate of strength gain Compatibility The Fly Ash Problem! 2010 Concrete Sustainability Conference 6 National Ready Mixed Concrete Association

7 Waste to Recycled Returned Concrete - estimated 2-10% of production 8 to 12 million cubic yards Truck Washout 50 to 200 gallons per truck Need to manage Storm Water Process Water Aggregates and Cement Solids Comply with environmental regulations 2010 Concrete Sustainability Conference 7 National Ready Mixed Concrete Association

8 Returned Concrete & Wash Water 1. Variable amounts surplus concrete returned to the plant everyday. 2. Must be disposed of or reused somehow. 3. Mixers must be flushed out at the end of each day. 4. BMPs should address both surplus concrete and mixer washout water. 5. More than one method is necessary 2010 Concrete Sustainability Conference 8 National Ready Mixed Concrete Association

9 1950 s: This is Not New! 2010 Concrete Sustainability Conference 9 National Ready Mixed Concrete Association

10 Water & Solids Management 2010 Concrete Sustainability Conference 10 National Ready Mixed Concrete Association

11 Returned Concrete Options Top-loading: Batch on top, re-ship Windrow and crush Sell Reuse Settling ponds Solids Water Pave plant Cast blocks Reclaimer systems Solids Water 2010 Concrete Sustainability Conference 11 National Ready Mixed Concrete Association

12 Concrete Products 2010 Concrete Sustainability Conference 12 National Ready Mixed Concrete Association

13 Blocks 2010 Concrete Sustainability Conference 13 National Ready Mixed Concrete Association

14 Blocks 2010 Concrete Sustainability Conference 14 National Ready Mixed Concrete Association

15 Crushed Concrete Aggregate g (CCA) 2010 Concrete Sustainability Conference 15 National Ready Mixed Concrete Association

16 Crushed Returned Concrete (CCA) 2010 Concrete Sustainability Conference 16 National Ready Mixed Concrete Association

17 CCA - Aggregate in Concrete Sustainability: Reduce landfill burden 15 million yd 3 / year ( high foot ball fields) Economy: $300 Million/yr 2010 Concrete Sustainability Conference 17 National Ready Mixed Concrete Association

18 Specifications ASTM C33 Coarse CCA is recognized May not meet all quality requirements Fine CCA recognized ASTM C125 - manufactured sand 2010 Concrete Sustainability Conference 18 National Ready Mixed Concrete Association

19 NRMCA Research CCA , 3000, 5000 psi Non AE Concrete Sustainability Conference 19 National Ready Mixed Concrete Association

20 NRMCA Research 17 Non-AE mixtures Cement = 500 pcy, slump 5-7 in., w/cm=0.57 CCA as is 300, 600, 900 pcy CCA sieved as coarse - 50/100% of virgin 4AE mixtures Evaluated Cement=564 pcy, slump 6-8 in., w/cm=0.45, HRWR Effects on fresh concrete Hardened concrete strength, durability 2010 Concrete Sustainability Conference 20 National Ready Mixed Concrete Association

21 Effect of CCA on Strength Strengt th, % of contr rol Effect on Strength 1000 psi 3000 psi 5000 psi Control 60 A-300 A-600 A-600 A-900 C-50 C-100 CCA condition C-100 C -100/F-25 C-100 Control Strength = 4200 psi 2010 Concrete Sustainability Conference 21 National Ready Mixed Concrete Association

22 Performance Issues Water demand Impacts strength Slump loss Sprinkle stockpiles Accelerated set time 30 to 60 min Permeability Can be addressed ASR depends on old concrete Shrinkage Freeze thaw durability 2010 Concrete Sustainability Conference 22 National Ready Mixed Concrete Association

23 Options for Concrete Producer No processing 300 lbs/yd 3 - (10% of aggregate volume) Manage returned loads Strength>3000 psi, crush after 14 days 900 lbs/yd 3 (30%) set times, higher shrinkage, F-T resistance Separate into coarse / fine 100% Coarse CCA 1600 lbs/yd 3 (50%) set time, shrinkage 2010 Concrete Sustainability Conference 23 National Ready Mixed Concrete Association

24 Proportioning mixtures Equivalent Mortar Method Equivalent volume virgin agg Old mortar part of new mortar Similar performance Fresh Mechanical Durability Fathifazl et al, Concrete International, March Concrete Sustainability Conference 24 National Ready Mixed Concrete Association

25 Ultimate Goal Concrete needs to meet Purchasers requirements Specifications Challenges: Economic incentive No credit in green ratings More attention quality control 2010 Concrete Sustainability Conference 25 National Ready Mixed Concrete Association

26 Top-Loading 2010 Concrete Sustainability Conference 26 National Ready Mixed Concrete Association

27 Batching on Plastic Returned Concrete Need to Know: Quantity Batch characteristics Age Cement content Temperature Amount of added water Requirements for new batch 2010 Concrete Sustainability Conference 27 National Ready Mixed Concrete Association

28 Reusing Returned Concrete - No Admix Effect on Strength - 28% Returned Concrete Mixed to Target Slump 6000 psi Strength, Age of Returned Concrete 45 min 3 hrs Original min 90 min 3 hrs Delivery Time 2010 Concrete Sustainability Conference 28 National Ready Mixed Concrete Association

29 Reusing Returned Concrete - No Admix Effect on Strength - 28% Returned Concrete Mixed to Target Slump Setting Time e, hr Age of Returned Concrete 45 min 3 hrs Original 0 45 min 90 min 3 hrs Delivery Time 2010 Concrete Sustainability Conference 29 National Ready Mixed Concrete Association

30 Reusing Returned Concrete with Hydration Stabilizing Admixtures Need to Know: Quantity Batch characteristics Age Cement content Temperature Amount of added water Time to hold Admixture dosage Requirements for new batch 2010 Concrete Sustainability Conference 30 National Ready Mixed Concrete Association

31 Reusing Returned Concrete HSA 28-day Strength, ps 6000 Same Day Recycling 5% % Control min 45 min 3 hr 3 hr HSA Added at Dose, oz/cwt Concrete Sustainability Conference 31 National Ready Mixed Concrete Association

32 Reusing Returned Concrete HSA Setting time, h Same Day Recycling Control 5% 50% 0 45 min 45 min 3 hr 3 hr HSA Added at Dose, oz/cwt Concrete Sustainability Conference 32 National Ready Mixed Concrete Association

33 Reusing Returned Concrete HSA 28-day Str rength, ps Overnight Recycling 7000 Control 5% 50% min 45 min 3 hr 3 hr HSA Added d at Dose, oz/cwt Concrete Sustainability Conference 33 National Ready Mixed Concrete Association

34 Challenges: Top-loading Standards Attempts to revise ASTM C94 Quality Control Resources A real time decision difficult to plan Customer acceptance Credit in green ratings Economic Incentives Cost-benefit 2010 Concrete Sustainability Conference 34 National Ready Mixed Concrete Association

35 Recycling Water 2010 Concrete Sustainability Conference 35 National Ready Mixed Concrete Association

36 Recycled Water Reduce water usage to clean trucks and plants Use recycled cled water Batch water in concrete Plant and truck washing Plant and yard wash down Slump adjustment Aggregate sprinklers Challenge: Disposal of solids 2010 Concrete Sustainability Conference 36 National Ready Mixed Concrete Association

37 Water and Solids Management Vary from simple to complex: 1. Pit or sedimentation ponds 2. Recycle clarified water 3. Basic reclaimers e 4. Reclaimers - Zero-discharge 5. Reclaimers - 100% recycling system w/hsas 2010 Concrete Sustainability Conference 37 National Ready Mixed Concrete Association

38 Typical Truck wash, batch plant or discharge after treatment Settling basin Solids to landfill 2010 Concrete Sustainability Conference 38 National Ready Mixed Concrete Association

39 Sedimentation (Washout) Basin w/water Transfer Capability 2010 Concrete Sustainability Conference 39 National Ready Mixed Concrete Association

40 Basic Reclaimer System 2010 Concrete Sustainability Conference 40 National Ready Mixed Concrete Association

41 Drying Extracted Solids 2010 Concrete Sustainability Conference 41 National Ready Mixed Concrete Association

42 Zero Discharge Reclaimed Aggregates Recycler Plant Clear Water Slurry Pit Clear Water Slurry Water Courtesy: Szecsy 2010 Concrete Sustainability Conference 42 National Ready Mixed Concrete Association

43 Reclaimers w/gray Water Recycling 2010 Concrete Sustainability Conference 43 National Ready Mixed Concrete Association

44 Research Use of wash water 2010 Concrete Sustainability Conference 44 National Ready Mixed Concrete Association

45 Wash Water: Effect on Consistency NRMCA Target slump 3 5 in U of Toronto Air-entrained w/c = 0.40, lb/cu.yd. Mixing Water, (mm) Slump Control Clarified 30 lb 60 lb Slurry Solids (kg/m 3 ) 2010 Concrete Sustainability Conference 45 National Ready Mixed Concrete Association

46 Wash Water: Effect on Setting Time NRMCA 8.00 Constant tslump 8 U of Toronto Constant w/c Air-entrained: w/c = 0.40 Set Time, hrs Setting Time (hours) Control Clarified 30 lb 60 lb Slurry Solids (kg/m 3 ) 2010 Concrete Sustainability Conference 46 National Ready Mixed Concrete Association

47 Wash Water: Effect on Strength NRMCA U of ftoronto Constant w/c Constant Slump 40 trength, psi th (MPa) ompressive St Strengt 20 C Control Clarified 30 lb 60 lb Solids, kg/m Concrete Sustainability Conference 47 National Ready Mixed Concrete Association

48 Zero Discharge - HSA Courtesy: Knelson Concrete Recovery Systems 2010 Concrete Sustainability Conference 48 National Ready Mixed Concrete Association

49 Zero Discharge - HSA Courtesy: Knelson 2010 Concrete Sustainability Conference 49 National Ready Mixed Concrete Association

50 Zero Discharge: w/ HSAs 2010 Concrete Sustainability Conference 50 National Ready Mixed Concrete Association

51 Gray Water Recycling Monitoring gray water Specific gravity Temperature Age Plumbing, back-flush Special water meters, Maintenance! QC buy-in Commitment and Training! 2010 Concrete Sustainability Conference 51 National Ready Mixed Concrete Association

52 Wash Water/HSA: Effect on Setting Time Slurry with 45 lb. solids to Mix No Admixture Low Dose High Dose Setting Time Control 4 h 1d 7d Age of Slurry 2010 Concrete Sustainability Conference 52 National Ready Mixed Concrete Association

53 Wash Water/HSA: Effect on Strength Slurry with 45 lb. solids to Mix 28-d Co ompressive Strength, psi No Admixture Low Dose High Dose 4000 Control 4h 1d 7d Age of Slurry 2010 Concrete Sustainability Conference 53 National Ready Mixed Concrete Association

54 ASTM C Mixing Water Types Potable Non-potable Water from ready mixed production Qualify for use Strength Setting time Optional Chemistry Solids Testing Frequency 2010 Concrete Sustainability Conference 54 National Ready Mixed Concrete Association

55 ASTM C 1603 Density and Solids Content Density Solids Content 2010 Concrete Sustainability Conference 55 National Ready Mixed Concrete Association

56 Gray Water Blend Chart based on specific gravity of gray water % Gray Water / Tap Water (Based on sp. gr. of Gray Water) per ASTM C-94 Optional Table 3 (Limit of Total Solids in Mixing Water = 50,000 ppm) Chart Based on 35 gal. Water/ 500 lb. Cement Mix Design Gray Water Specific Gravity % Gray Water % Tap Water % 0% % 0% % 1% % 21% % 36% % 46% % 54% % 59% % 63% % 67% % 69% % 72% % 74% % 75% % 77% % 78% % 79% % 80% % 81% % 82% 2010 Concrete Sustainability Conference 56 National Ready Mixed Concrete Association

57 Challenge: Recycle Water Specification clause Mixing water for use in concrete shall be potable 2010 Concrete Sustainability Conference 57 National Ready Mixed Concrete Association

58 Can we meet these goals??? Key Performance Indicators Potable water: 10% reduction by % reduction by 2030 Waste: 30% reduction by % reduction by 2030 Recycled content: 200% increase by 2020% 9% 400% increase by 2030 ~ Concrete Sustainability Conference 58 National Ready Mixed Concrete Association

59 Challenges Performance Identify Impact Resolve Resources Technology and investment Standards d Do they restrict? Specifications Will they permit? Customer Perception 2010 Concrete Sustainability Conference 59 National Ready Mixed Concrete Association

60 And the biggest challenge Does it make ECONOMIC sense 2010 Concrete Sustainability Conference 60 National Ready Mixed Concrete Association

61 Challenges and Opportunities Recycled Materials in Ready Mixed Concrete Thank you Questions 2010 Concrete Sustainability Conference 61 National Ready Mixed Concrete Association