The Way Concrete Recycling Should Be Fuminori Tomosawa1, Takafumi Noguchi2 and Masaki Tamura3

Invited paper The Way Concrete Recycling Should Be Fuminori Tomosawa1, Takafumi Noguchi2 and Masaki Tamura3

Received 20 September 2004, revised 1 December 2004 Abstract Providing excellent performance as a structural material, concrete has long been deemed essential for modern civilization and recognized as a material that will continue to maintain and support the development of human society. Now that recycling of concrete in a completely closed loop has become technically feasible, concrete is being seen in a new light. This paper reviews the background to this development referring to changes in social systems and the introduction of new technologies. In view of the fact that consideration of the global environment will be required in the future at every step of the production of concrete and concrete structures, this paper goes on to overview the methods for identifying social needs related to concrete structures, the manner in which production systems of structures should meet such social needs, lifecycle design techniques for structures, and techniques for expressing the environmental performance of structures. The authors finally discuss the nature of true recycling and a truly recycling-oriented society, based on the above-mentioned discussions.

1. Introduction the establishment of a full-fledged recycling system, as the recycling process principally consisted of simply Concrete is a useful cast material that has a close affinity crushing the waste concrete, which inevitably entailed a to natural materials, consists of only common compo- degradation in quality. Nevertheless, the goal of technical nents, and hardens by itself just by being in contact with development shifted in the mid-1990s to recycling of water in a natural environment. After hardening, it turns concrete into a material having qualities equal to those of into a material with sufficient strength and durability to normal concrete, and recycling of concrete in a com- be applicable to various structures. Recent technology pletely closed loop has now become technically feasible. for high-strength concrete has realized a compressive This paper reviews this development and introduces strength exceeding 150 N/mm2 for reinforced concrete the new technology while discussing the meaning of true skyscrapers. recycling and a truly recycling-oriented society. Concrete has thus grown to be an essential material for modern society with great commonness, usefulness, and 2. Current status and problems of excellent performance characteristics as a structural construction waste material, and will continue to be vital for maintaining and developing human society. 2.1 Analyses of construction waste However, the sheer amount of concrete in use and in According to a White Paper on the Environment, the total stock compared with other materials brings up the issue material input of Japan ranged from 2.0 to 2.2 billion tons of the enormous amount of waste generated when con- annually in 1999 and 2000, of which 1.0 to 1.1 billion crete is disposed of. This issue has existed for a long time, tons (50%) were accumulated every year in the form of as concrete has conventionally been regarded as being buildings and civil structures. These figures indicate the difficult to recycle. Being a major user of concrete, the enormous consumption of resources by the construction construction industry has addressed this problem and car- industry compared with other industries. The production ried out research and development regarding the recy- of concrete, a primary construction material for forming cling of concrete since the 1970s in cooperation with the modern nations, amounted to approximately 500 million public sector. However, the uses of recycled products tons (including 300 million tons of ready-mixed con- have been limited to road bottoming, without leading to crete) in 2000 in Japan, accounting for nearly 50% of the annual resource consumption of the construction industry. In other words, concrete accounts for nearly 25% of

1Professor, Faculty of Science and Engineering, Nihon Japan's total material input. Incidentally, the construction University, Japan. industry's consumption of steel and wood, two other primary construction materials, amounted to 32,530,000 E-mail: [email protected] 3 2Associate Professor, Dept. of Architecture, Graduate and 17,000 tons (34,219 m volume, converted by as- School of Engineering, The University of Tokyo, Japan. suming the density to be 0.5), respectively, in 2001, both 3Research Associate, Dept. of Architecture, Graduate far less than concrete consumption. School of Engineering, Tokyo Metropolitan University, Furthermore, the amount of waste in Japan totaled Japan. approximately 458,360,000 tons in 2000 (general waste: 4 F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005

Non-industrial Other waste Output Input 7300 (16%) 5236 (11%)

Chemical industry Elec.,Gas,Heat, Construction waste Output 1700 (4%) Water supply Input Steel industry Total waste Do Check industry Final disposal of 1280 (28%) 2700 (6%) in Japan Illegal dumping 9200 (20%) industrial waste Pulp,Paper 45836 of industrial Construction Other Other waste 2700 (6%) 10,000 tons 4500 waste Plan Action (Ratio) 3220 (72%) 10,000 tons 16.2 (40%) Output Input 40.3 24.1 (60%) (Ratio) 10,000 tons Construction Agriculture (Ratio) Input Output 7900 (17%) 9100 (20%)

(a) (b) (c) Fig. 1 Construction waste analyses.

52,360,000 tons; industrial waste: 406,000,000 tons) as shown in Fig. 2, an enormous amount of demolished shown in Fig. 1 (a). Waste from construction accounted concrete lumps will be generated in the near future from for approximately 20% (79,000,000 tons) of the indus- concrete structures mass-constructed during Japan's trial waste. Moreover, in 2000, construction waste ac- rapid economic growth being, which are doomed to counted for nearly 30% (12,800,000 tons) of the demolition due to durability problems. Moreover, road 45,000,000 tons of industrial waste destined for final construction is decreasing and the method of repair is disposal sites as shown in Fig. 1 (b) and approximately expected to shift from replacing to milling and applying 60% (241,000 tons) of the 400,000 tons of illegally an overlay. These trends will lead to an imbalance be- dumped industrial waste as shown in Fig. 1 (c). As con- tween the supply of demolished concrete and the demand crete lumps account for approximately 42% (35,000,000 for road bottoming. Also, the volumetric reduction of tons) of total construction waste, approximately 8% of future infrastructures based on population estimation and total waste in Japan therefore consists of concrete lumps. the extension of the service life of the existing stock by As stated above, concrete accounts for large percent- increased succession, utilization, and conversion will ages of both resource input and waste discharge. Thus keep on reducing the amount of new construction of promotion of the recycling of demolished concrete is a structures and concrete production. Accordingly, this pressing social issue in Japan where the remaining ca- will culminate in the need to recycle aggregate into ag- pacity of landfill sites for industrial waste is diminishing gregate for concrete, and it is no exaggeration to say that every year. recycled aggregate can account for the greatest part of future aggregate for concrete. It is therefore vital to 2.2 Destinations of demolished concrete convert recycling from quantity-oriented to qual- With the aim of solving the construction waste problem, ity-oriented recycling as proposed in the Promotion Plan the Japanese Ministry of Land, Infrastructure and for Construction Waste Recycling 2002 formulated by Transport (MLIT, formerly the Ministry of Construction) the MLIT in 2002. In other words, it is necessary to find formulated an Action Plan for Construction Byproducts optimum recycling methods with due consideration to (Recycling Plan 21) in 1994, which called for halving the the material balance, while promoting the production and amount of final disposal of construction waste by 2000, supply of high-quality recycled aggregate. and a Promotion Plan for Construction Waste Recycling It should also be noted that a large discrepancy exists in 1997, which includes principles, objectives, and between the amount of demolished concrete generated at measures for further promoting recycling of construction waste. Thanks to such active and continual policies, 6 construction waste discharge began to decrease, with the Concrete production recycling ratio of concrete lumps and asphalt concrete 5 lumps exceeding 95%. In view of the still low recycling ratios of waste wood, slime, and mixed waste generated 4 by construction, the MLIT then enforced the Basic Law Demolished concrete for Establishing a Recycling-based Society, the Con- 3 struction Material Recycling Act, and the Law on Pro- From buildings moting Green Purchasing. 2 However, concrete lumps, which boast a high recycling ratio, are entirely destined for bottoming and 1 grading adjusters for arterial high-standard highways, From civil structures 0 urban expressways, and general roads designated by the 1950 2000 2050 year Road Bureau of the MLIT. The quality of recycling is therefore completely different from that of asphalt con- Fig. 2 Estimated amount of demolished concrete (Iida, K. crete lumps, for which level-cycling is accomplished. As 2000). F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005 5

450 produced the Standard for the Use of Recycled Aggre- Estimated generation of aggregate and 400 stone per unit input gate and Recycled Concrete (Draft) in 1977. This stan- Statics discharge of concrete lumps 350 from demolished concrete structures dard requires that the oven-dry density and water absorption of recycled coarse aggregate be not less than 2.2 300 g/cm3 and not more than 7%, respectively, and those of 250 Potential generation recycled fine aggregate be not less than 2.0 g/cm3 and 200 not more than 13%, respectively. This was followed by 150 research and development under two projects promoted

100 by the Ministry of Construction (1981-1985 and Discharge 1992-1996), both titled the Comprehensive Technology 50 Development Project, as well as the investigation of 0 1960 1970 1980 1990 2000 2010 2020 2030 recycled concrete for the suspended World City Exhibi- Year tion in Tokyo (1994), the investigation into authorization Compiled from field survey of construction byproducts, field survey of demand for labor, etc. criteria by the building Center of Japan (1999), the establishment of a prestandard (TR A0006: Concrete con- Fig. 3 Estimated generation and discharge of concrete taining recycled aggregate) by the Japan Standards As- lumps from demolished buildings (Takegahara, K. 2002). sociation, and the organization of the Standardization Committee for Recycled Aggregate in the Japan Con- crete Institute (2002), which is tasked with formulating a demolition sites and the amount discharged from such draft JIS for recycled aggregate for concrete. sites. This may result from the reuse of demolished Table 1 gives the quality criteria established through concrete as a material for road bottoming or backfill on the above-mentioned organizational activities, showing site and its disposal as part of mixed construction waste. the progressive improvement in the qualities of recycled This discrepancy poses no problem if all the dissociation aggregate achieved by advances in the technology for results from reuse on site, but if it includes mixed waste producing recycled aggregate, finally reaching a level and illegal dumping, then the amount of discharged comparable to natural aggregate. concrete may rise by a corresponding amount when such The Recycled Aggregate Standardization Committee practices are rectified in the future. Recycling of demol- classifies recycled aggregate into three classes -- H, M, ished concrete as aggregate for concrete will then be- and L -- by water absorption and oven-dry density, each come even more compelling. being recommended for concrete structures and seg-

ments as given in Table 2. This classification urges a 3. Current state and problems of recycled shift to a design system that permits the use of each class aggregate for concrete for suitable structures and segments. High-quality recycled aggregate is suitable for structures and segments 3.1 Quality standard and uses requiring high durability and strength, while middle- to Research and development aimed at using demolished low-quality recycled aggregate, which can be produced concrete as recycled aggregate for concrete began in the with minimal cost and energy or powdery by-products, is 1970s, dating back to a three-year study from 1974 suitable for other structures and segments. conducted by the Construction Waste Disposal Reuse Committee of the Building Contractors Society, which

Table 1 Quality standard for recycled aggregate and uses for concrete containing recycled aggregate. Coarse aggregate Fine aggregate Year Formulated by Name of standard Density Absorption Stability Density Absorption Stability （g/cm3）（%）（%）（g/cm3）（%）（%） Type 1 － 3 or less 12 or less － 5 or less 10 or less Ministry of Construction Provisional quality stan- 1994 dard for reuse of concrete Type 2 － 5 or less 12 or less － 10 or less － (MOC) byproducts by use Type 3 － 7 or less －－－－ Accreditation criteria of recycled －－ 1999 Building Center of Japan aggregate for building concrete 2.5 or more 3.0 or less 2.5 or more 3.5 or less Ministry of International JIS TR A0006（Low quality recycled －－－－ 2000 Trade and Industry (MITI) aggregate concrete） 7 or less 10.0 or less 2.5 or more 3.0 or less － 2.5 or more 3.5 or less － Draft JIS (Type H recycled aggregate (high quality) and its uses) No limitations are put on the type and segment for concrete and The Committee of stan- structures with a nominal strength of 36 or less － 5.0 or less －－ 7.0 or less － 2004 dardization for structural Draft JIS (Type M recycled aggregate recycled aggregate, Japan (medium quality) and its uses) Members not subjected to drying or freezing and thawing action, such Concrete Institute as piles slabs on grade, and concrete filled in steel tubes Draft JIS (Type H recycled aggregate － 7 or less －－ 13 or less (low quality) and its uses) Backfill concrete, blinding concrete, and leveling concrete JIS A 5005（Crushed stone and sand for concrete） 2.5 or more 3.0 or less 12 or less 2.5 or more 3.0 or less 10 or less JIS A 5308（Ready mixed concrete） Annex1 2.5 or more 3.0 or less 12 or less 2.5 or more 3.5 or less 10 or less 6 F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005

3.2 Production methods and equipment twin cone are scrubbed by one another. This process is Single toggle-type jaw crushers are generally used for the automatically repeated several times according to the primary crushing of demolished concrete regardless of required quality. A wet scrubber/levigator, shown in Fig. the ultimate quality of recycled aggregate. Impact 4 (d), incorporates a mechanism whereby concrete lumps crushers are used for secondary and tertiary crushing crushed in multiple stages using a crusher and wet when producing middle- and low-quality recycled ag- scrubber are moved up and down in water to separate gregate. While the quality of recycled aggregate pro- mortar and wood chips with a low density from coarse duced by using such equipment is improved as the aggregate. number of treatment processes increases, the recovery percentage of recycled aggregate decreases with in- 3.3 Importance of quality control creased amounts of powder byproducts as the aggregate A quality control system for construction materials has itself is crushed. Special equipment is therefore neces- been established, to ensure that materials, particularly JIS sary for efficient production of high-quality recycled products and products conforming to JIS, are supplied aggregate. Other equipment in practical use for produc- with constant qualities that meet the specifications under ing middle- and low-quality recycled aggregate includes strict quality control, so that contractors and citizens can self-propelled or vehicle-mounted jaw crushers and im- carry out construction and use the resulting structures pact crushers that save the energy normally expended to with peace of mind. While it is essential to establish such haul the demolished concrete. a system for promoting the wide use of recycled aggre- Equipment in the stage of practical use for the efficient gate, a distinctive difference exists between crushed production of high-quality recycled concrete is shown in stone/sand for concrete and recycled aggregate with Fig. 4 (a)-(d). A heating grinder, shown in Fig. 4 (a), regard to material procurement. Whereas crushed incorporates a mechanism using a tube mill to separate stone/sand that is deemed uniform to a certain extent can aggregate from cement paste embrittled by heating con- be procured in large quantities, the grading, density, crete lumps roughly crushed to 40 to 50 mm in diameter water absorption, alkali-silica reactivity, etc., of demol- to 300°C. This is the only device capable of also pro- ished concrete may naturally vary from one lump to ducing fine aggregate for concrete. An eccentric ro- another, particularly when the recycled aggregate pro- tor-type mechanical grinder, shown in Fig. 4 (b), has a duction plant is located away from demolition sites mechanism whereby concrete lumps charged into a space (off-site plant) and accepts demolished concrete from between the inner cylinder that rotates eccentrically and various structures. To promote recycled aggregate as JIS the outer cylinder are made to scrub one another to re- products or JIS-conforming products, it is therefore move cement paste adhering to aggregate surfaces. It is necessary to (1) produce recycled aggregate from only capable of producing 60 tons of recycled aggregate per specific structures at on-site plants; (2) carry out material hour. A screw mill, shown in Fig. 4 (c), has a mechanism control by separately storing concrete lumps from each whereby concrete lumps charged into a cylinder having a structure at off-site plants; or (3) carry out quality control

Concrete lump feed Filling heater Recovery System Bag filter Grinding Eccentric rotor totates Sieve Outer cilinder Motor Tube mill type

Fine aggregate Fine powder Coarse aggregate Recovery Power transmission

a) Heating grinder b) Eccentric rotor-type mechanical grinder

Cylinder casing Inlet Middle cone Concrete lump 450mm×2200mm Discharge cone Surface water level Drum Low density zone High density zone Inlet Rot bar Outlet Low-density recycled aggregate

Water level range High-density recycled aggregate in air chamber Rotary blade Outlet c) Screw mill d) Wet scrubber / levigator

Fig. 4 Equipment for producing recycled aggregate for structural recycled aggregate concrete. F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005 7 by substantially increasing the frequency of acceptance inspections and product inspections at off-site plants. “Element of an organization’s (1.4) activities, products or services that can interact with the en- 3.4 Future issues vironment (1.1)” Apart from the above-mentioned quality control, quite a few problems remain unsolved, warranting further in- *1.1 environment vestigation of methods of recycling demolished concrete Surroundings in which an organization (1.4) operates, into aggregate for concrete, which will be inevitably including air, water, land, natural resources, flora, fauna, required in the future as stated above. These include humans, and their interrelation measures against the alkali-silica reaction and applica- *1.4 organization tion development for powder byproducts. How to deal Company, corporation, firm, enterprise, authority or with the amount of alkali yielded from cement paste institution, or part or combination thereof, whether in- adhering to recycled aggregate is a serious problem for corporated or not, public or private, that has its own functions and administration middle- and low-quality recycled aggregate. The alkali content of concrete made using such aggregate will be well over 3 kg/m3, the limit set by the regulation for total Figure 5 shows a classification and targets of sus- alkali content. It is therefore also necessary to review the tainability considerate of global environmental aspects. effect of Type B blended cement in a highly alkaline According to the above definition, the environment is a environment. Since the production of high-quality recy- concept to be recognized as a factor covering a wide cled aggregate entails a large amount of powder by- range. As environmental aspects are composed of wider products, research and development are necessary for the concepts, possible events to be considered can increase effective use of such powder. The uses under study in- in the future. It should be noted that the construction clude addition to road bottoming, cement material, addi- industry, which is responsible for the activities using tion to concrete, ground-improving material, asphalt products made using recycled aggregate and recycled filler, and inorganic board material, which always com- aggregate concrete, is by nature prone to be involved in pete with other inexpensive natural resources. It is social and environmental events through industrial ac- therefore necessary to stabilize the quality of byproduct tivities due to the properties of the materials and the mass powder and reduce the quality control cost. circulation systems the industry uses. In other words, extensive social responsibilities may be assigned for the 4. Environmental aspect of concrete production of finished articles and raw produce. Stake- structure production holders may therefore be required to monitor market expansion while maintaining continuous awareness of 4.1 Introduction of environmental aspect for the boundaries of environmental aspects. Such practice concrete structures will ultimately lead to risk management for producing Environmental aspect is defined in ISO 14050 (Envi- concrete structures. ronmental management – Vocabulary) as follows: Meanwhile, an essential concept for considering social

Social Small The "environment" dealt with in ISO 14001 People in developing nations Individuals People in industrialized nations Economic Environmental Self-transcendence Earth Groups (religious people, etc.) Targets of Economic Environmental Social sustainable development Hydrological aspect aspect aspect Profit cycle Social /nonpublic-interest corporations Social (business corporations) Nonprofit Humans, flora Economic /nonpublic-interest corporations Human life Corporations and fauna aspect (labour unions) Economic Environmental /public-interest corporations Material Atmospheric Economic Environmental cycle (NPO, public corporations) cycle /public-interest corporations Primary aspects of Targets of (national and local gorvernment) Environment sustainability sustainable buildings Building Social Manufacturers Civil Structure

The Big Bang 20th century Global environmently utility Public of organization, Scale Mass Products City society Age Rocal level Society Nation level Economic Environmental Region level (Asia, Globe, etc.) Targets of

sustainable society Large

Fig. 5 Classification and objects of sustainability with consideration to global environmental aspect. 8 F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005 activities deeply related to the environment is sustainable Individual stability Developing development. The first comprehensive proposal was nations made in Our Common Future, a report prepared by the Group stability Industrialized World Commission on Environment and Development nations that was published in 1987, in which the following prin- Local stability Environmentally conscious ciples were included. Regional stability industrialized nations 1. Social equity (social aspect) Global stability 2. Environmental prudence (environmental aspect) 3. Economic efficiency (economic aspect)

The environmental aspect is regarded as being com- Fig. 6 Order of dependence for stability conditions on a posed of a social aspect, environmental aspect, and global scale. economical aspect. This suggests that conscious consideration of the social aspect and environmental aspect in factor. Stabilization on the individual and organizational addition to the conventional economic aspect will be- levels, for instance, is important for social stabilization in come an important part of production activities. This developing countries, whereas in developed countries, means that any development may be inappropriate from where environmental consideration is mandated by rati- the viewpoint of sustainability unless it is based on these fied treaties, it is necessary to give consideration to sta- three principles to ensure sustainable development. bilization on the regional and global level rather than on The Sustainability Reporting Guideline in the Global the individual and organizational levels. Reporting Initiative (GRI), which is highly regarded for Stabilization on the global level can be achieved by the formulation of environment reports, names three maintaining the three cycles, i.e., the hydrological cycle, factors of sustainability rating, i.e. economic, environ- atmospheric cycle, and material cycle, to maintain mental, and social aspects, and stresses the need for without damaging it the self-cleaning action of the earth extracting specific factors and clarifying their mutual as inferred from the ISO 14000 series. It is relationship. self-explanatory that stability on the global level as a As stated above, the conventional practice of produc- superordinate concept is essential for ensuring stable tion falls short in terms of holistic strategy, specifically conditions in smaller regions as a subordinate concept on the application of a manufacturing strategy in consid- a long-term basis while maintaining equitability between eration of social and environmental aspects in addition to generations. the economic aspect. To put it plainly, an essential condition required of concrete structures for the stabilization of the earth is that 4.2 Grounds for identifying social needs for a system for assuring the three cycles, i.e., the hydro- concrete structures logical, atmospheric, and material cycles, should be From a broad perspective, even in the era of the global inherent in such structures. Focusing on the material environment, the world as a whole makes its way under cycle, which is closely related to the act of production, the banner of the human-oriented goal of leading a sus- the condition is consolidated into a commitment to en- tainable social life premised on the development of sure resource circulation of the structure and its materials economic activities. It is predicated on the theory that a beforehand. As recycled aggregate concrete is a factor system for distributing goods produced through eco- that strongly affects the material cycle of structures, it is nomic activities to markets and benefiting from them is important to extend the radius of influence from indi- necessary for satisfying (or stabilizing) people, in order vidual consumers to organizations/groups and to dis- to achieve an affluent social life in the future. (It has been tricts/regions to give develop efficient resource circula- made clear through past discussions that this cannot be a tion of structures and materials and to capture related universal and optimum form of human activity consid- needs. erate to the global environment.) Systems for such stability and affluence become more complicated and hard 4.3 Factors of social systems composing envi- to accomplish as the range expands from the level of ronmental aspects individuals to organizations, regions, nations, and to the The environmental aspects of concrete structures are earth[8]. It is now vital to recognize that we are, for better embodied by focusing on their social and environmental or worse, at the ultimate stage of active worldwide efforts aspects in addition to conventional economic aspects aiming for global stability, including measures against with respect to various types of information (interna- global warming committed to by the Kyoto Protocol. By tional treaties, laws, rules, policies, and guidelines) that way of explanation, Fig. 6 shows the order of dependence serve as factors for extracting environmental aspects. for the conditions of stability of a global system. This Figure 7 shows the order of dependence for environ- figure does not imply a hierarchical relationship but mental aspects in the broad sense of the word. Although shows an order of dependence in which the upper factor this figure classifies the environmental aspects into three is realized depending on the support from the lower factors (needs of individuals/society, formative factors of F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005 9

Extract essential functions of structures Stakeholders as a whole

Desire for self-fulfilment Desire for acknowledgement Inherent desire Needs of individuals of individuals and society Desire for affiliation and organizations Desire for safety Physiological desire Primary Technique aspects of Technical Information Technical factors sustainability Specification Guidelines ・Social aspect Principles, Policies Formative factors Policy factors of social systems National policies ・Environmental Domestic laws (regulations) aspect Domestic laws (constitution) Legal factors International treaties ・Economic aspect Local environment National environment Area factors Regional environment Formative factors of global systems Material, Hydrologic, Atomosheric cycles Cycle factors

Fig. 7 Order of dependence for environmental aspects in a broad sense. social systems, and formative factors of global systems), factors primarily comprise specifications, methods, and this section deals with the formative factors of social techniques, whose contents and spread steer social trends. systems that can be used to clearly define environmental Note that information on the needs of individuals and aspects. Note that the global systems at the bottom of the society can be fed back to design techniques for struc- pyramid consist of the three cycles of the earth and re- tures through technical factors (e.g., architectural design gional factors, but that the environmental aspects may briefing). These permit investigation in specific terms vary widely depending on the country and area. The into the needs of individuals and society derived from radius of influence of the same environmental aspect can their inherent desires. vary widely depending on the effect of factors on the regional level. It can therefore be said that the contents 4.4 Formative factors of individual and social and degrees of the needs of individuals and society based needs on such global and social systems can also vary from one The factors forming the needs of individuals and society society to another. are considered to be the inherent desires of individuals The formative factors of social systems are roughly and organizations. It is therefore desirable to extract classified into three categories. The first category con- various needs from the inherent desires of individuals sists of legal factors primarily comprising international and society to identify the needs for structures, which are charters/treaties, domestic laws (fundamental laws and to be ultimately reflected in the essential functions of the normal laws), and local regulations. In a law-abiding structures. Figure 8 shows the order of dependence of society, the boundaries of acceptable social/economic inherent desires of individuals and society that affect the activities and industrial activities are defined by these essential functions of structures. Inherent desires of in- legal factors. dividuals can be objectively grasped by Maslow's theory The second category covers policy factors that are of motivation and human needs and the concept of the deeply involved in the formation of actual social order. need for self-transcendence to change oneself into Policy factors, which form a concept smaller than that something beyond one's present state. Maslow's theory formed by legal factors, comprise national poli- of motivation and human needs consists of levels of cies/measures, principles/strategies, and guidelines. needs for physical safety and security, social safety and Since these factors directly affect the boundaries of security, communication and response, self respect and activities, they concretely shape the way society func- acceptance, and fulfillment of goals and dreams, in tions. which the fulfillment of the lower level is essential for The third category comprises technical factors for fulfilling the next higher level. conducting social activities safely and rationally under It is not easy to grasp inherent desires of organizations the influence of the legal and policy factors. Technical and society, but the existence of such desires is indubi- 10 F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005 table. Their needs can be clarified to a certain extent by 5. Lifecycle design techniques for concrete research. For instance, when an enterprise, a typical structures social group, is explained as integrating production factors and continuously operating a business with the aim 5.1 Future production systems of production and profit making, or the subject of such This section objectively discusses the production system activities, the fundamental desire of enterprises corre- for existing concrete structures. A conventional manu- sponding to the needs on the bottom level as defined by facturing system can be regarded as a system focusing on Maslow (physical needs of enterprises) may be the desire cost saving and efficiency without consideration of ease to conduct a business operation that is economically of disassembly of the products and component materials, viable and does not cease to produce profits, and this is based on which most existing concrete structures have considered to be an essential desire of enterprises. En- been produced. Since the technology for recycling the terprises are therefore understood as groups that seek for products of such a system is inevitably required to treat their identities driven by the bottom needs defined by used products not intended for recycling at the design Maslow (physiological needs of enterprises). In this case, stage, recycling can be regarded as an alternative for the likelihood that their activities will fulfill the desires waste disposal. This is a typical end-of-pipe approach of the upper levels is considered very low. This explains leading to down-cycling, but is still essential, as the the difference between individuals and organizations enormous stock of existing concrete structures will from the aspect of needs. somehow demand treatment of concrete lumps in the A large number of firms recently carry out their in- future. If, recycled products happen to be in great de- dustrial activities while promoting environment protec- mand with a low level of performance requirements, tion. These can be recognized as activities for fulfilling down-cycling can be an effective solution for a certain the desire for self-respect and acceptance, which com- period until such demand disappears. Road bottoming plements the physiological desire of enterprises. On the can be regarded positively as an instance of such a solu- other hand, the activities of environmental nonprofit tion. Despite continuous research and development since organizations can be recognized as activities for fulfilling the early 1970s, structural recycled aggregate has not their desire for self-transcendence placing top priority on been actively used. This is presumably due to the absence the global environment. Although the desires of organi- of application development based on social needs for the zations and societies differ from the order of dependence product or technological development in view of equi- of individual desires as explained above, organizational tability between generations. activities are important, as they produce large-scale and In consideration of the problems inherent in the con- immediate effects on actual activities for solving envi- ventional end-of-pipe approach, a new solution should be ronmental problems. an integrated inverse manufacturing system defined as a The production of structures generally has a strong manufacturing system in which downstream processes impact on society. Moreover, interests in structures in- are consistent with upstream processes for the purpose of clude individuals as well as their relationships with so- ensuring resource circulation using component materials ciety. It is therefore important to simultaneously extract that can be assembled and disassembled by similar work the needs of individuals and society and fulfill them in loads. This system is characterized by ease of disassem- the form of essential functions of structures. bly as well as assembly incorporated at the design stage. Figure 9 shows a model concept of integrated inverse

Desire for self-fulfilment Raising of profits for corporations Desire for acknowledgement through affiliation

Desire for affiliation Expend stakeholders

Desire for safety Physical Physiological desire for corporations NPOs, etc. Physiological desires desire

Self-transcendence desire Metaphysical Self-transcendence desire desire a) Inherent desire of individuals b) Inherent desire of organizations

Fig. 8 Inherent desires of individuals and society affecting the essential functioning of structures. F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005 11 a) Forward-process b) Forward-process manufacturing c) Integrated forward-and -inverse manufacturing system system with added inverse process manufacturing system

Physical performance Physical performance Physical performance Metaphysical performance Metaphysical performance Metaphysical performance

Ease of Ease of assembly Ease of assembly Ease of assembly disassembly Assembly/disassembly performance

Ease of disassembly Design of maximizing integrated process

Fig. 9 Concept of integrated inverse manufacturing. manufacturing. A characteristic of construction products Accordingly, the resource recycling through concrete distinctive from those in other industrial segments is that structures based on integrated inverse manufacturing their overall performance can be brought into full per- suggests the possibility that concrete can be efficiently spective by substituting the quality of the members and recycled, inspiring hope for the closed-loop recycling of component materials for physical performance and the concrete structures. quality of human work and deeds for metaphysical performance. 5.2 Inherent needs of structures In view of this characteristic, the application of the Generally speaking, if a structure can retain the required concept of minimizing the number of separate processes performance throughout its lifecycle, then it can be used in the design method by aiming for ease of assem- semi-permanently without losing its value. In the lifecy- bly/disassembly to concrete structures is attempted in cle design technique taking into consideration the re- this section. This design method includes common source values of materials to be discussed in this section, processes whereby the ease of disassembly is propor- an integrated inverse manufacturing system should be tional to the ease of assembly, with easy-disassembly derived while achieving long service life for structures design leading to easy-assembly design, and and component material conservation. It is therefore counter-processes whereby the ease of disassembly is necessary to clarify the essential functions the structures inversely proportional to the ease of assembly, with possess. easy-disassembly design making assembly difficult. Table 2 gives the relationship between the essential Minimization of counter-processes is a design technique functions of the components and the individual design whereby the effects of the latter design factors are factors for reinforced concrete buildings. Figure 10 minimized to derive a rational disassembly-assembly shows the order of dependence of lifecycle design performance. Assuming that various metaphysical per- composed of individual design factors. From the bottom formances are included as information among the mate- up, the order of dependence of building components rial performances as the structure that is the ultimate consists of raw materials, materials, member elements, result, (a) the disassembly performance is not included in members, and buildings. Focusing on the elements of the metaphysical performance in a conventional system structures, eight functions ((1) to (8)) are derived as through the end-of-pipe approach, as the ease of disas- essential functions, as well as four individual design sembly is not considered by the designers; and (b) in a factors (A to D) to introduce the functions to structures. conventional system with an added inverse manufactur- In other words, the essential functions of buildings and ing approach, the work load at the demolition stage in- member elements lead to reducing design under items (1) evitably increases, as the ease of disassembly, which is a and (2); the essential functions of buildings, members, metaphysical performance, is introduced a posteriori. On and member elements lead to maintenance design under the other hand, (c) in an integrated inverse manufacturing items (3) and (4); the essential functions of member system, disassembly and assembly are carried out with elements and materials lead to reuse design under items similar levels of work load, as the ease of disassembly is (5) and (6); and the essential functions of materials and ensured at the design stage without significantly altering raw materials lead to recycling design under items (7) the ease of assembly. and (8) (see Table 2). The four individual design ele- The metaphysical performance integrated by the sys- ments permit the composition of a lifecycle design hier- tem is thus rationalized, resulting in a manufacturing archy in consideration of the resource values of the ma- system with an excellent resource-recycling capability. terials. 12 F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005

Table 2 Essential functions of components of structures and individual design factors derived from the functions. Building elements Fundamental functions of building elements Design contents Long life, stable and durable against earthquakes (1. Long life) Structural frame Reduce Use of suitable amount of natural resources in construction (2. Resource saving) Structural frame, Maintain quality toward required performances (3. Maintain quality) Maintenance Beams and Columns Easily changed into a high grade level at replacement (4. Upgrade) Beams, Columns and Reusable as member with no degraded quality (5. Level-cycle reuse) Reuse Concrete Reusable as member with degraded quality (6. Down-cycle reuse) Concrete and Constitu- Recyclable as material with no degraded quality (7. Level-cycle recycle) Recycle tion materials Recyclable as material with degraded quality (8. Down-cycle recycle)

O r d e r o f d e p e n d e n c e f o r b u i l d i n g O r d e r o f d e p e n d e n c e f o r li f e - c y c le - d e s i g n c o n t e n t s D e s i g n a im s ( T a r g e t s )

Whole Building Reduce design (for structure) construction Long life (Skeleton) Reduce materials (Infill) Unit Maintenance design (for skeleton,infill) assembly Maintain quality (Parts of skeleton) Factors of unit Upgrade (Parts of infill) manufacturing Reuse design (for member) Level-cycle reuse (Structural member) Intended material Down-cycle reuse (Non-structural member) manufacturing Recycle design (for material) Level-cycle recycle (Aggregate, Cement) Raw material Part Down-cycle recycle (Low-quality aggregate)

Fig. 10 Order of dependence of lifecycle design composed of individual design factors.

Long life, Resource saving Maintenance, Upgrade

5.3 Lifecycle design technique Table 3 gives the properties of structures derived from lifecycle design. Component details and reuse techniques after renewal can be clarified to a certain extent by de- Short life, Resource disposing Maintenance free termining the eight design objectives representing the A) Reduce design B) Maintenance design essential functions in the physical performance hierarchy Level-cycle reuse Level-cycle recycle and establishing the basic components to be designed. Figure 11 shows the relationship between design objectives representing the essential functions of structures. Waste Waste This schematically expresses the eight design objectives included in the four individual design elements while Down-cycle reuce Down-cycle recycle incorporating the side factors of the essential functions C) Reuse design D) Recycle design (resource wasting, disposal, etc.). This scheme serves as the basic factors for indexing the degree of satisfaction of Fig.11 Relationship between design objectives repre- the essential functions of structures while permitting the senting the essential functions of structures. assumption of appropriate methods of renewal and disposal of the structures and their components. For instance, when a structure is produced with the design the introduction of recycling technology to accelerate objective of level-cycling (D7), materials that permit resource cycling within closed systems. recycling into structural concrete at the time of renewal are selected, and methods of demolition and disposal 5.4 Examples of lifecycle design with low work loads are selected and carried out. Application examples of the lifecycle design technique The lifecycle design taking into consideration the are described in this section. The following two social resource values of materials thus succeeds in realizing a needs derived from the environmental aspects closely mechanism to incorporate the essential functions derived related to current concrete structures in Japan are ex- from the environmental aspect the structure is involved tracted: 1) the durable use of structural framing premised with. As a result, the lifecycle design technique inher- on resource conservation to address the issues of re- ently incorporates the concept of recycling, which is the source depletion and the global environment; and 2) so-called inverse manufacturing and which characterizes active recycling into structural concrete when the de- the technique and distinguishes it from existing manu- mand for road bottoming disappears, in view of the di- facturing. In other words, this technique can be recog- minishing capacities of final disposal sites. Let us now nized as a factor of recycling design strategy aiming for try to find the essential functions of structures to meet F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005 13 these needs and carry out lifecycle design giving priority degree, is applied, leading to level-cycling concrete to these functions as the design objectives. The design structures. procedure begins with the specification of the design At level 3, resource-conserving and life-considering level determined from the combination of the individual design with limitations as to the uses of recycled mate- design factor and the design objective, through selection rials is applied, leading to down-cycling concrete struc- from the combination matrix. Select A1: Service life tures from which low-quality recycled aggregate and extension of the structure in reducing design and B3: road bottoming are produced after demolition. Performance retention of the structure components in At level 4, resource-conserving and life-considering maintenance design to satisfy the first requirement, and design premised on material disposal is applied, leading select D7: Level-cycling of concrete materials in recy- to concrete structures to be disposed of after demoli- cling design to satisfy the second requirement. Select D8: tion. Note that for structures made of level-cycling con- Down-cycling of concrete materials in recycling design crete, the use of a concrete capable of material conser- and Final disposal result as secondary factors of essential vation as given in Table 5 is a prerequisite for retaining functions. Therefore, four design levels were finally the resource value of the materials in consideration of specified including these two. equitability between generations. This permits the estimation of the recycling conditions Cement recovery type completely recyclable concrete and product properties (see Table 4). was applied for the first time to an actual structure in At Level 1, resource-conserving and life-extending 2000 (Fig. 12). The target structure consisted of the design, which permits the use of recycled materials with foundations of a residential building constructed as part no limitations as to applications is applied and a renewal of the project for completely recyclable houses mainly form of level-cycling after demolition is ensured, leading promoted by Ojima Laboratory at Waseda University. to level-cycling concrete structures from which recycled Due to the strong need to promote structures that reduce structural aggregate and cement materials are produced. environmental impact by reducing waste, completely At Level 2, resource-conserving and life-considering recyclable concrete is considered to be an essential ma- design, which permits the use of recycled materials as terial for such structures. component materials for equivalent products with no limitations as to applications by processing to a high

Table 3 Properties of structures derived from lifecycle design. Order of Design contents Design aims dependence of lifecycle de- for developing Building elements Example of building elements Utilization after replacing of building sign design contents 1. Long life Structural frame Reinforced concrete beams, Same as the left Reduce de- Column and wall etc. Building A sign 2. Resource Structural infill Dynamic core, Air conditioning unit, Same as the left saving Electronic units, Water supply unit 3. Maintenance Composed units Concrete Unit, Non-structural wall, Same as the left Flame B Maintenance quality for structural frame Sub-member, Concrete club, etc. design 4. Upgrade Composed units Air condition unit Same as the left for structural infill Part of water supply unit 5. Level-cycle Reinforced concrete col- Unit C Reuse design reuse Beams and column Concrete Unit, Non-structural wall, umn and beam 6. Down-cycle of concrete Sub-member, Concrete club, etc. Non-structural wall, reuse Sub-member 7. Revel-cycle Original aggregate Material D Recycle recycle Concrete constitu- Coarse aggregate, Fine aggregate, Cementitious materials design 8. Down-cycle tion materials Cementitious materials, etc. Low quality recycled recycle aggregate, Additives

Table 4 Classifications of design levels and concrete types by life cycle design. Reduce Maintenance Recycle design Conditions of recycling Properties of products Design design design level Long-life Maintain Level cycle Down cycle Property of A1 quality B3 D7 D8 original material Property of crushing Type Application Prior selection ● ● ● and surface im- Simple crushing for Level-cycle con- Aggregate for struc- Level 1 --- provement of collecting aggregate crete (recyclable) tural concrete aggregate

● ● ● ● Highly crushing for Level-cycle con- Aggregate for struc- Level 2 No way collecting aggregate crete (recycling) tural concrete

Simple crushing for Aggregate for ● ● ● Down-cycle con- non-structural con- Level 3 --- No way collecting crusher crete crete, run Road subbase ● ● Simple crushing for Disposing Level 4 ------No way disposing concrete Waste 14 F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005

Table 5 Examples whereby a type of concrete that enables level cycle recycle. Types Definition Cement Recovery Type - Concrete whose binders, additives and aggregates are all made of cement or cementitious materials, and all of Completely Recyclable these materials can be used as raw materials of cement. Concrete Aggregate Recovery Type- Concrete whose aggregate surfaces are improved by emulsion-type coating agent without excessively reducing Completely Recyclable the mechanical properties in order to reduce the bond strength between aggregate and the matrix and thereby Concrete permitting easy recovery of original aggregate.

lifecycle design technique described in the previous section. As the degree of inclusion of the essential functions in the design objectives increases, the occupied area generally increases, resulting in increases in the volume ratio of the colored portion of the stereoscopic index. The form of Level 1, which shows an ideal structure, is conical, representing a structure designed taking into consideration the environment and equitability between generations while achieving structural safety. This can be recognized as an index for a stable condition. Conversely, (d) the form of Level 4 is poorly balanced, giving an impression of instability.

6. Toward a veritable recycle-oriented society

As stated above, conventional concrete recycling through low-quality recycled aggregate has yet to be marketable, whereas recycled aggregate having qualities equal to normal aggregate can be used for general structural concrete, though with drawbacks related to the cost. Promotion of recycling is essential for establishing a recycling-oriented society. However, it is difficult for low-quality products to achieve marketability simply Fig. 12 Cement recovery-type completely recyclable because they are recycled, as illustrated by this example. concrete applied to completely recycle house. The authors consider that recycling technology should fulfill the following principles. 5.5 Evaluation of the fulfillment of lifecycle de- 1. Recycling should be of high quality. sign requirements 2. Recycling should be repeatable. In order to retain the essential functions of structures for The former means that recycled products are not a long time, an index is necessary at least for the user and marketable unless they are of a quality that satisfies users, purchaser of the structure, with which the design objec- and recycling is not a viable proposition in spite of the tives representing the essential functions can be recog- accurate description as a "recycled product." Low quality nized. A system of performance evaluation/indication is of recycled products should be considered to indicate the therefore important. Recent proposals include BEES for immaturity of the recycling technology and the need for evaluating the degree of environmental impact technology improvement or new technology develop- throughout the entire lifecycle of materials by NIST and ment to achieve quality recycled products. CASBEE, a comprehensive environmental evaluation The latter means that, if a recycled product has to be system incorporating the effects of environmental load dumped in a landfill after use with no chance of recycling, factors other than physical performance of buildings. then the recycling is no better than producing waste of Figure 13 shows a stereoscopic index expressing the the following generation, contradicting the formulation degree of inclusion of the design objectives in the indi- of a recycling-oriented society. Such a product also vidual design factors. These are configured by the su- burdens the purchaser with the responsibility of waste perposition of individual design factors, serving as an disposal. Potential purchasers will hesitate to purchase index to the degree of inclusion of the design objectives, the product the moment they realize this pitfall, pre- as well as a simple tool for expressing the essential venting the recycling loop from closing (Old Maid rule). functions of structures. Accordingly, to be repeatable, recycling must aim for the Figure 14 shows four typical forms of mass hierarchy reproduction of the same product in the original sense of of design levels in the implementation models by the the word to form a loop. F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005 15

A) Reduce design A) Reduce

B) Maintenance design Downgrade B) Maintenance

Levelgrade C) Reuse C) Reuse design Upgrade D) Recycle D) Recycle design

a) Set the design aim b) Selection of the grade variation c) Generation of conbination patterns d) Composition of mass hierarchy

Fig.13 Stereoscopic index expressing degree of design objectives in individual design factor.

a) Level-cycle recyclable b) Level-cycle recyclable c) Down-cycle recycled d) Disposal concrete concete (Level 41) concete (Level 42) concrete (Level 43) (Level 44) Fig.14 Example of mass order of dependences in some design levels.

Care should be exercised regarding so-called cascade when evaluating and developing recycling technology. recycling, mixed/compound recycling, recycling into other industries, and byproduct utilization, as these tend 7. Concluding remarks to be unrepeatable. When a product utilizing a byproduct is repeatedly recycled, the byproduct as a material will Recycling technology for concrete has significantly de- become useless, ending up as waste. What is a truly veloped in recent years, making the material sufficiently recycling-oriented society? Humans live on a cycle of recyclable. Though problems remain regarding the cost, resource use in which they take various resources from distribution, and system, the prospect appears to be fa- nature into their society, obtain benefits from them for a vorable. given period by processing and using them, and return Through many years of research and development of them back to nature as waste when their cease to be concrete recycling and investigation of the difficulties useful. Once taken into human society, the resources are and problems of recycling practice, the authors learned altered or modified and by the time they are returned to that the two principles above-mentioned are vital for nature for final disposal, their state has changed to a recycling to be a viable proposition. This approach to certain extent. Just one or two recycling phases represent recycling has long been practiced for electric steel, alu- a short stay of resources in human society, which ends up minum, and paper and has been adopted for various types with disposal (return) to nature. True recycling should of products including PET bottles recycled into PET eliminate such return of resources to nature. Unrepeat- bottles, and the reuse and recycling of materials for able recycling merely extends their stay on the human automobiles and electrical appliances. Efforts for side without contributing to the basis for a truly recy- closed-loop recycling have also begun in the fields of cling-oriented society. The only acceptable case for this glass, gypsum board, and other construction materials. type of cycle is the use of resources in such a way that the This trend will eventually prevail in all fields in the fu- product returned to nature does not represent an envi- ture, leading to a society in which materials recyclable in ronmental load. closed loops or disposable in a nature-friendly form A recycling-oriented society in the true sense of the banish those that are not, as illustrated by chlorofluoro- word is a society that continues to use resources, once carbons, which are being driven out of the market. they are taken from nature into the society, without re- In this sense, the greatest challenge for mankind is the turning them unless they do not represent an environ- formulation of a recycling system for carbon dioxide gas mental load. In such a society, the intake of resources and other greenhouse gases, which account for the vast from nature is minimized and products and materials that majority of waste on earth. cannot be recycled repeatedly are rejected. While this vision may be overly idealistic, it should be kept in mind 16 F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005

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