Sustainable Recycling of Concrete with Environmental Impact Minimization

Transcription

1 Sustainable Recycling of Concrete with Environmental Impact Minimization Takafumi Noguchi The University of Tokyo

2 Content Background Environmental Impact in Concrete-related Industries State-of-the-art of Concrete Recycling Technologies and Standards Closed-loop Recycling System Completely Recyclable Concrete Conclusions

3 Environmental Problems in Construction Materials flow, resource consumption and waste generation Greenhouse gas emissions Destruction of the ozone layer Acidification (Acid rain) Outdoor air pollution Water pollution and soil contamination Disruption of the ecosystem (Biodiversity) Heat island Noise and vibration Landscape destruction (Aesthetic degradation of the landscape) Indoor air pollution

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5 Environmental Problems in Concrete Industries Global warming Resource depletion Waste disposal

6 Building Related CO 2 Emission Japan s total CO 2 emission 1.2 billion tons Other industries 64% Housing construction 5% Commercial building construction Building 6% repair 1% Energy for housing Energy for commercial building operation 13% operation 11% 36%

7 CO 2 Emission from Concrete Industries Portland cement: 1 ton CO 2 : 0.75 ton Decarbonation of limestone (60 %) Fossil fuel combustion (30 %) Concrete: 1 m 3 CO 2 : ton Cement production (0.25 ton) Others ( ton)

8 Resource Input into Construction Industries Total Construction 1,000 (million t/year) 50% of total resources for industries Construction CONCRETE Total: 2,000 (million is the t/year) second most Total: widely 1,000 (million consumed t/year) substances on Earth, after water! LIQUID STONE:NEW ARCHITECTURE IN Others CONCRETE (National Building Museum in Washington D.C.) Wood Steel Concrete 500 (million t/year) 50% of resources for construction

9 Waste Output from Construction Industries Industrial Waste Total: 406 (million t/year) Construction Waste Total: 79 (million t/year) Chemical Steel Others Energy Agriculture Sludge Wood Others Asphalt concrete Pulp Construction 79 (million t/year) 17% of total industrial waste Concrete 35 (million t/year) 42% of construction waste

10 Possible waste in final disposal area Final Disposal Sites for Waste (million m 3 ) Scarcity of residual capacity of final disposal areas Industrial Waste: 412 (million t/year) General Industrial Resource-recycling society

11 Definition and Meaning of Resource Depletion Significant reduction in availability to the next generation Difficulty in acquiring resources as a vast amount of energy is needed to do so Difficulty in carrying out life activities that depend on resources Soaring resource price Increase in environmental destruction through acquisition of a resource Loss of economic advantage regarding the use of a resource

12 Forecast of Limestone Depletion in Japan

13 Production (million t) Change in Aggregate Consumption in Japan Crushed Hill gravel Sea gravel River gravel Pit gravel Others Causing exposure of bedrock on the bottom of the sea erosion of embankments endangering sand spits and fishing grounds Good quality river gravel have become depleted. Year Crushed stone have become major.

14 Content Background Environmental Impact in Concrete-related Industries State-of-the-art of Concrete Recycling Technologies and Standards Closed-loop Recycling System Completely Recyclable Concrete Conclusions

15 Recycling Ratio of Concrete Recycle Disposal Ministry of Construction Action Plan for Construction Byproducts 94 Promotion Plan for Construction Waste Recycling 97 Basic Law for Establishing a Recycling-based Society Construction Material Recycling Act Law on Promoting Green Purchasing Emission of Concrete Lumps (million t) For road subbase For mechanical stabilization underground

16 Production (million t) Predicted Amount of Future Concrete Waste Concrete production Demand for road subbase Concrete waste Greatest part of future aggregate for concrete Imbalance between Year supply of concrete waste demand for road subbase Recycling From Quantity-oriented to Quality-oriented

17 Japan Industrial Standards (JIS) for Recycled Aggregate JIS A 5021 Recycled aggregate for concrete - Class H JIS A 5022 Recycled concrete using recycled aggregate Class M JIS A 5023 Recycled concrete using recycled aggregate Class L Coarse aggregate Fine aggregate Density (g/cm 3 ) Absorption (%) Density (g/cm 3 ) Absorption (%) Class H 2.5 or more 3.0 or less 2.5 or more 3.5 or less Class M 2.3 or more 5.0 or less 2.2 or more 7.0 or less Class L or less or less

18 Applications of Recycled Aggregate Scope of application Class - H Class - M Class - L No limitations for structural concrete with a nominal strength of 45MPa or less JIS A 5308 (Ready-mixed concrete) allowing to use Class-H RA for normal strength concrete Members not subjected to drying, such as piles, underground beam, and concrete filled in steel tubes with a nominal strength of 36MPa or less Backfill concrete, blinding concrete, and leveling concrete with a nominal strength of 24MPa or less

19 Recycling Process of Concrete Rubbles Demolished Concrete Rubbles Jaw Crusher Impact Crusher Vibratory Sieves Heating Tower Vibratory Sieves Cone Crusher Coarse Aggregate Scrubber Road Subbase, Backfill Vibratory Sieves Fine Aggregate Scrubber Low Quality Recycled Coarse Aggregates Low Quality Recycled Fine Aggregates High Quality Recycled Coarse Aggregates Vibratory Sieves High Quality Recycled Fine Aggregates Powder (a) Road Subbase (b) Low Quality Recycled Aggregates (c) High Quality Recycled Aggregates

20 Problems in Conventional Technology to Produce High-quality Recycled Aggregate Water Absorption (%) Repeated crushing Recovery percentage decreasing Fine aggregate and powder generation increasing 5-10mm not less than 10mm Recovery Percentage (%) Recycled Fine Aggregate Size of Supplied Concrete Lumps Recycled Coarse Aggregate Coarse Aggregate Fine Aggregate Fine Powder Powder No 1st 2nd 3rd Number of Crushing Treatment No 1st 2nd 3rd Original Concrete Crushing Treatment

21 Mechanism of Heated Scrubbing Heating at 300 C Rubbing process Concrete rubble Weakening of hardened cement paste Removal of powdered cement hydrate

22 Heated Scrubbing Equipment for High-quality Recycled Aggregate Hot Elevator Dust Chamber 2 nd Scrubbing Machine 1 st Scrubbing Machine Rotary Kiln Sieve Filler Tank By-product Powder Recycled Fine Aggregate -5mm Recycled Coarse Aggregate 5-20mm

23 Application of Heated Scrubbing Method F- Project Completed in 2003 Laboratory : Structure : Steel structure (7 Stories) Building area : 9,800m 2 Total floor area : 51,000m 2 Total volume of recycled concrete: 10,000m 3

24 Mechanical Scrubbing Equipment for High-quality Recycled Aggregate Concrete lumps Eccentric tubular mill External cylinder Scrubbing Motor Recovery Transmission gear

25 Application of Mechanical Scrubbing Method Old apartment Houses 12 x 4-storied Concrete lump: 11,500 t New apartment Houses 7 x 9-19-storied Recycled coarse aggregate: 3,000 t Recycled concrete volume: 3,000 m 3 ( Total concrete volume:40,000 m 3 )

26 Utilization of By-product Powders Large amount of by-product powders generated Possible uses Raw material for clinker Ground improving material Addition to road bottoming Concrete addition Asphalt filler Inorganic board material Demands Quality stabilization Reduction of quality control cost

27 Content Background Environmental Impact in Concrete-related Industries State-of-the-art of Concrete Recycling Technologies and Standards Closed-loop Recycling System Completely Recyclable Concrete Conclusions

28 Problems in Current Recycling Forwardprocess production Existing technology Nosotropic technology No recycling-conscious design applied Materials diffused into a wide range of industries Finally disposed Quality degradation, Unstable supply, Unstable price, Unstable distribution, Increasing environmental impact

29 Concept of Completely Recyclable Concrete New technology Proactive Technology Upstream (inverse) processes incorporated Components of concrete completely recycled into concrete Resource conserved Resource circulated in a closed system

30 Cement-recovery Type Completely Recyclable Concrete Demolition Operation Production of CRC Crushing & Milling Calcination Semi-closed-loop Clinker Gypsum Construction Recycled cement Aggregate Concrete whose binders, additives and aggregates are all made of cement or materials of cement, and all of these materials can be used as raw materials of cement after hardening

31 Changes in CO 2 Emissions and Dumped Concrete 5% of concrete replaced with cement-recovery type CRC every year CO2 Emission Dumped concrete 150 CO2 Emission Dumped concrete Dumped Concrete 50 0 CO 2 Emission Elapsed year (1) As it is 50 0 Calcined limestone never emits CO Elapsed year (2) Production of CRC

32 Application of Cement Recovery Type CRC for Eco-Pole Supply of Pole Remove and Transportation Use and Operation Manufacture of Pole Placing of concrete Closed Recycle of Concrete Pole Crushing and Classifying Steel Recycling Limestone Supply Cement Supply Steam cured Raw Material for Cement Limestone Mining Circulation of Cement Manufacture of Cement Removal of form

33 Aggregate-recovery Type Completely Recyclable Concrete Demolition Operation Construction Production of CRC Crushing & Sieving Calcination Recycled Closed-loop aggregate Clinker Recycled cement Surface modified aggregate Concrete which is designed to reduce the adhesion between aggregate and the matrix to an extent that does not adversely affect the mechanical properties of concrete by modifying the aggregate surfaces beforehand, thereby facilitating recovery of original aggregate

34 Mechanism of Aggregate-recovery Type CRC Chemical treatment Physical treatment The principal ingredient of the coating agent is mineral oil. The agent hydrolyzes in alkali conditions of fresh concrete, forming acidic matter and indissoluble amalgam on the surface of the aggregate. The surface coating results in decreased amounts of cement hydrate, and leads to decreased adhesive strength between aggregate and paste matrix, allowing easy recovery of the original aggregate. The coating agent is a water-soluble synthetic resin emulsion, which is applied in process of abrasion, and which is chemically stable in fresh concrete. The uneven surfaces of virgin aggregate become smoother, the shape of the aggregate being roughly maintained. This decreases adhesive strength between aggregate and paste matrix, allowing easy recovery of the original aggregate.

35 Recovery and Mechanical Property of Aggregate-recovery Type CRC No treatment Chemical Physical No treatment Chemical Physical Recovery ratio (%) Crushed stone W/C=60% Gravel Strength (MPa) Trade-off relationship remained Aggregate recoverability increased Crushed stone Mechanical properties of concrete decreased W/C=40% Gravel

36 Advanced Aggregate Recovery-type CRC Concrete strength enhancement Aggregate surface modification Increase bonding force between coarse aggregate and mortar Fine SCM: pozzolanic reaction Mineral powder: mechanical friction 330 C 610 C at 10sec 30sec Surface modification treatment Aggregate Mortar Aggregate recoverability Inclusion of dielectric material Selective heating by microwave Weakening aggregate surface Recovery of aggregate with low energy < Microwave heating > < After microwave heating >

37 Mechanical Properties in Advanced Aggregate Recovery-type CRC Increase

38 Aggregate Recovery Ratio in Advanced Aggregate Recovery-type CRC Recovery ratio (%) Original coarse aggregate Fine aggregate Paste Decrease Increase O1 O2 O3 SP80

39 CO 2 Emission in Concrete Recycling Process CO2 emission (kg/t-concrete) Heatedscrubbing Mechanicalscrubbing Decrease Others Scrubbing Microwave heating 30sec 60sec 90sec

40 Sustainable Resource Recycling Concrete Society Concrete structure Long-lived Demolition and recovery Complete separation Recycled coarse aggregate Coarse aggregate Fine aggregate Modification Modified coarse aggregate Fine aggregate Microwave heating Little CO 2 emission Cement factory High-purity Ca Recycled fine aggregate (under technology development) Use as raw material of cement clinker Demolition and recovery By-product powder Cement Completely recyclable structure

41 Content Background Environmental Impact in Concrete-related Industries State-of-the-art of Concrete Recycling Technologies and Standards Closed-loop Recycling System Completely Recyclable Concrete Conclusions

42 Conclusion Toward sustainable resource-recycling society Concrete recycling in closed system Current method: Some technical and social problems Adoption of technology enhancing resource conservability at the stage of design Completely recyclable concrete New technology with aggregate surface modification and microwave radiation Overcoming inherent conflicting properties in concrete recycling Achieving high performance of concrete Energy saving and small CO 2 emission in concrete recycling Fully recovering original aggregate Generating cement raw materials which never emit CO 2

43 Thank you for your kind attention!