Japanese Standardization of recycling materials to concrete

Transcription

1 Japanese Standardization of recycling materials to concrete Y Tsuji*, Gunma University, Japan Y Suzuki, Sumitomo Osaka Cement, Japan 27th Conference on OUR WORLD IN CONCRETE & STRUCTURES: August 2002, Singapore Article Online Id: The online version of this article can be found at: This article is brought to you with the support of Singapore Concrete Institute All Rights reserved for CI Premier PTE LTD You are not Allowed to re distribute or re sale the article in any format without written approval of CI Premier PTE LTD Visit Our Website for more information

2 271J1 Conference on OUR WORLD IN CONCRETE & STRUCTURES: August 2002, Singapore Japanese Standardization of recycling materials to concrete Y Tsuji*, Gunma University, Japan Y Suzuki, Sumitomo Osaka Cement, Japan Abstract Researches on utilization of recycled materials have been advanced regarding recycled aggregate, Eco-cement, municipal solid waste, incineration ashes of sewage sludge, crushed stone powder and so on. For the widespread usage of these recycled materials, standardization is indispensable. This paper presents the circumstances and the summary of each establishment regarding the Japanese Industrial Standard(JIS) on Eco-cement, Technical Report(TR) on concrete using recycled aggregate, molten-slag fine aggregate and crushed stone powder for concrete by which a draft proposal was stipulated in two research committees for standardization of technology to utilize recycled materials for concrete established in the Japan Concrete Institute(JCI). Keywords: standardization, recycled aggregate, Eco-cement, crushed-stone powder, molten-slag aggregate, Japanese Industrial Standard (JIS), Technical Report(TR) 1. Introduction Utilization of recycled materials such as demolished concrete, industrial by-products, municipal solid waste and so on have been a keen and urgent interest for researchers and engineers in construction fields. Researches on utilization of these recycled materials have been advanced. For the widespread usage of these recycled materials, standardization is indispensable. This paper presents the circumstances and the summary of each establishment regarding the Japan Industrial Standard(JIS) on Eco-cement and the Technical Report (TR) on concrete using recycled aggregate, crushed stone powder and molten-slag aggregate by which a draft proposal was stipulated in the research committee for standardization of technology to utilize recycled materials for concrete (hereafter called as the recycling standardization committee) established in JCI. 2.First and Second Recycling Standardization Committees in JCI After the Agency of Industrial Science and Technology of the previous Ministry of International Trade and Industry commissioned Japanese Standards Association, JCI established the first recycling standardization committee in response to re-consignment through the Japanese Standards Association for three years from fiscal year. The purpose of the consignment is to stipulate the draft proposal of JIS. Also, to make a draft proposal of the TR, and attain standardization of recycling materials used for concrete. In 2001 fiscal year JCI established the second recycling standardization committee to make a draft proposal of the TR on molten-slag aggregate based on the JCI Standard Proposal which was a research results of the first recycling standardization committee in response to re-consignment through the Japanese Standards Association. 91

3 The theme for the first committee is "standardization of technology to utilize recycled materials for concrete ", and what recycled materials can be utilized for concrete was examined at the first stage. The following six materials were examined. (1) Recycled Aggregate (2) Crushed Stone Powder (3) Municipal-Solid-Waste Incineration Ashes (4) Sewage Sludge (5) Eco-cement (6) Ground-Granulated Waste Glass Concerning (3), the use of slag aggregate in which molten municipal-solid-waste incineration ash, and the practical use of the incineration ash itself were examined. Moreover, concerning (4), the use of slag aggregate made from processed sewage sludge, and practical use of its incineration ash were considered. Concerning material (6), we examined utilizing waste glass which was broken into a very fine powder to be used as an admixture for concrete. Of the six materials, recycled aggregate was recognized by the recycling standardization committee as being closest to the proposal of JIS. Although it was difficult to list the recycled materials which are stipulated by JIS, as a provisional standard and since data was also accumulated to some extent, crushed stone powder, municipal-solid-waste incineration ashes, sewage sludge, Eco-cement, etc. might be summarized in the TR. The above examination was performed at the first 3 meetings of the committee. The members of the first recycling standardization committee consisted of a total of 28 people from each field such as producer, user and neutral person. However after 4. times, the committee was divided into five working groups (WG) with the exclusion of (6), and whose activity was to stipulate the standard draft proposal of JIS, or the draft proposal of TR, respectively. In addition, because of the budget each WG mainly utilized experiment data accumulated until now. However, some of the budget was allotted to WG2's common mortar experiments of the crushed-stone powder. Until the end of 2000 fiscal year, the first recycling standardization committee stipulated the draft proposal of TR on Eco-cement, concrete using recycled aggregate and crushed stone powder and the draft of JCI Standard Proposal of molten-slag aggregate. In 2001 fiscal year, JCI established the second recycling standardization committee to make a draft proposal of the TR on molten-slag aggregate based on the JCI Standard Proposal. 3. Difficulties at Time of Stipulating JIS of Recycling materials When using recycled materials for concrete, generally the quality of the concrete with recycled material is sub-standard. Although it was a big difficulty at the time of stipulating JIS, these difficulties have still not been solved at this time. Since existing concrete-related JIS does not assume the above-mentioned situations, when stipulating JIS of recycling materials or standardizing, it was made to recognize that the obstacle is serious. For example, when JIS was stipulated for recycling materials (such as recycled aggregate, molten-slag aggregate, crushed sand powder and Eco-cement), if neither the Japan Society of Civil Engineers nor the Architectural Institute of Japan publishes a manual, it is felt that confusion will arise. And, on the other hand, the view that the application of recycled materials should have been restricted in the specifications of JIS should also be taken out. In the existing concrete-related JIS, specifying restrictions was not made in the main body of it. Therefore, it could only start with the argument about recycled materials changing the character of the standard of JIS. The committee members had to unify on how the concrete with recycled materials is used. Therefore, in the first recycling standardization committee, we stopped stipulating the draft of JIS and decided to stipulate the draft of TR classified into type II of the TR in the order of Eco-cement, recycled aggregate, molten-slag aggregate and crushed stone powder. Since the technical information 92

4 concerned with type II of TR is in the development stage, JIS cannot be stipulated in the present condition. Therefore, type II of TR compiles such technical information in order to encourage us to stipulate JIS in the near future [1]. This judgment has led to the good situation that the draft of TR on Eco-cement was released as TR R 0002 at May 22nd 2000, and TR R 0002 will be converted to JIS R 5214 on Eco-cement for a typical example. 4. JIS and TR Stipulations of Eco-cement Eco-cement is resources circulation type cement in which Taiheiyo Cement Corp., Aso Cement, and Ebara Corp. cooperated on research and which they developed together as an enterprise of New Energy and Industrial Technology Development Organization (NEDO). From April, 2001, the world's first Eco-cement factory started in Chiba Prefecture, and 110,000 tons of cement per year is produced. Moreover, in the Tokyo Tama area, a plan to operate in the 2004 fiscal year is advancing. Corresponding to change in the social situation, early public presentation of technical know-how, pros and cons, and the standardization of the technology concerned, the draft of TR was stipulated. Table 1 Quality of Eco-cement (TR R 0002:2000 and JIS R 5214:2002) Normal-type Regulated-set-type Item Eco-cement Eco-cement Density g/cm 3 1) _-- Specific surface area cm 2 /g 2500 or more 3300 or more Initial setting min 60 or more 5 or more 6 ) Setting time Final setting hour 10 or less 1 or less Soundness 2) Compressive strength N/mm2 Heat of hydration JIg Putting method Goodness Goodness Le Chatelier's method 10 or less 10 or less 1 day or more 3 days 12.5 or more 22.5 or more 7 days 22.5 or more 25.0 or more 28 days 42.5 or more 32.5 or more 7 days -_... 5) ) 28 days 5) 5) Magnesium oxide % 5.0 or less 5.0 or less Sulfur trioxide (as S03) % 4.5 or less 10.0 or less Ignition loss % 3.0 or less 3.0 or less Total alkali % Chloride ion % Note 1): Measured value is reported. 3) 4) 0.75 or less 0.75 or less 0.1 or less 0.5 or more and 1.5 or less Note 2): Measurement of soundness is based on the pad method of the main part of JIS R 5201, or the Le Chatelier's method of the attached Annex in this standard. Note 3): From the result of a chemical analysis, the total amount of alkali (%) is computed by the following formula, and is rounded to 2 figures below a decimal point by JIS Z 8401; Na20eq=Na K20 in which Na20eq is total alkali content in Eco-cement (%), Na20 is content of the oxidization sodium in Eco-cement (%), and K20 is content of the oxidization potassium in Eco-cement (%) Note 4): Measured value is based on the fixed quantity method of the chlorine of JIS R Note 5): Measured value is reported. Note 6): Item is deleted in JIS R 5214:2002. In addition to the mineral composition of usual cement, the Eco-cement developed at the 93

5 beginning contained C 11 A 7 and CaCI 2 as a calcium aluminate system clinker mineral, and the amount of chloride ion was 5000 ppm or more, and it was a regulated set type. Then, progress of dechlorine technology was made and the normal type Eco-cement which also usually controlled the amount of chloride ion from portland cement to many grades was developed. In standardization, we decided to usually specify two kinds, a normal and a regulated set type (Table 1). When stipulating the draft proposal of TR, the name "Eco-cement" became a problem. However, as this name has been used in the official documents even though not registered after standardization, it was decided to use it as it is. Eco-cement was defined as "manufactured cement from clinker which was made up of mainly city garbage incineration ashes, and added wastes such as sewage sludge". It is estimated that about at least 500kg of such wastes is used per 1 ton of cement. As stated above, the type and quantity of raw materials were specified. At the time of cement manufacture, the heavy metal in Eco-cement volatilized mist as a chloride, and was collected. Heavy metal was not detected although the leach-out of heavy metal from the JIS mortar using the Eco-cement was measured using the previous Environment Agency notification No. 46. Therefore, it became clear that the leach-out of heavy metal from the mortar using Eco-cement has satisfied the environment quality controls (1 st clause of Article 16 of Basic Environmental Law and the water quality standard based on regulation of Article 4 of Water Supply Law). The draft of TR was released as TR R 0002 (Eco-cement) on May 22, 2000, and May 21, 2003 is the end of validity. JIS R 5214(Eco-cement) will be published in 2002 after the Japan Cement Association has examined and prepared the draft of JIS based on TR R 0002 (Eco-cement). 5_ TR Stipulation of Concrete Using Recycled Aggregate In Japan, as much as 40 million tons of concrete demolition material is generated every year. Presently, the reuse rate of such concrete waste exceeds over 90 %. But its usage is generally limited to a backfill material and a base material for pavements, and is rarely utilized for concrete structures. The use of technology for recycled aggregate for concrete has reached a level of utilization through the results of previous research etc. However, when an arrangement of standards such as JIS was not made, it was not used. In order to incorporate recycled aggregate into the JIS system of conventional concrete, the TR of the concrete using recycled aggregate (hereafter called as recycled concrete) was stipulated first. The quality of the recycled aggregate produced by crushing concrete lumps from demolished concrete structures is shown in Table 2. In addition, the recycled aggregate produced by crushing hardened lumps of residues from ready mixed concrete is also included, but with some restrictions. And as for the use of the standard type of which the nominal strength is 12MPa, it is desirable to limit to the components of high strength or high durability, such as backfilling concrete, between stuffing concrete, leveling concrete, and sub-slab concrete are not required. In addition to the standard type, the salinity-control type (less than 0.3 kg/m 3 ) and the customized type (the maximum of nominal strength is 18MPa) are prepared. As the application record of recycled concrete is still not enough, considerable margin should be allowed for the usable range of this concrete and data acquisition should be facilitated. Item Rate of water absorption % Amount of material passing standard sieve 75 /.1 m in aggregates % Table 2 Quality of Recycled Aggregate (TR A 0006:2000) Recycled coarse aggregate Recycled fine aggregate 7 or less 10 or less 2 or less 7) 10 or less 7).8) 94

6 Note 7) :Since this value is usually satisfied when the manufacture method of aggregate is wet-type, it is not necessary to confirm especially. By the dry-type manufacture method, since the amount of material passing standard sieve 75 ij. m in aggregates may increase remarkably or the amount of mud may mix, this is checked by examination. Note 8):ln using JIS A 1801 instead of a particle part examination in an everyday quality control, the sand equivalent value may be 65% or more. Applications of recycled concrete are generally limited to the members or positions that do not require higher strength or higher durability. Specifically, the standard type and the salinity-control type are intended for regions not affected by the freeze-thaw action or for positions below the ground not exposed to this action. Table 3 compares the quality requirements of recycled concrete with those of ready mixed concrete specified by JIS A As the standard type and the salinity-control type of recycled concrete are each represented by one type, the nominal strength is set to 12 MPa, the slump below 15cm, the air content 5.0±2.0%, the maximum size of coarse aggregate 20 mm or 25 mm. In addition to these values, the chloride ion content in the fresh concrete to be below 0.3 kg/m 3 is added to the quality requirements of the salinity-control type. With regard to the customized type of recycled concrete, the values for the strength, the maximum size of coarse aggregate, the slump, the chloride ion content are to be determined by the purchaser after consulting with the manufacturer of the concrete. The maximum value for the nominal strength is set to IBM Pa. The draft of TR was released as TR A 0006 (Recycled concrete) on November 20, 2000, and is valid until November 19, After the TR is stipulated, the recycled aggregate as shown in Table 2 is used, and we hope to fully acquire data, such as the variation grade of quality. We expect to stipulate JIS in the following stage extension of use and use for some reinforced concrete. Now, JCI is preparing to establish the standardization committee in which the draft of JIS regarding recycled concrete will be stipulating based on TR A Table 3 Recycled Concrete and JIS A 5308 (maximum size of coarse aggregate:20 mm or 25 mm) Slump(cm) 8-12 ; Nominal strength (MPa) 12 (16) Recycled ready mixed concrete --- standard type Recycled ready mixed concrete ---- customized type JISA5308 ready mixed concrete 6.TR Stipulation after JCI Standard Proposal of the Molten-Slag Aggregate Manufactured from a Municipal Solid Waste and a Sewage Sludge The issue of standardization of molten slag which utilizes the incineration ashes of a municipal solid waste and a sewage sludge to concrete was taken up. Although it is common to consider the use of aggregate as a molten slag, there is the problem of marketability. Although molten-slag-ization is highly expensive, as it avoids the problems of the disposal of such large quantities of incineration ashes, use in concrete seems to be an attractive and efficient alternative. The manual of the application of molten-slag for concrete has already been released by Chiba Prefecture etc. 95

7 Table 4 Quality of molten-slag aggregate (JCI standard proposal) Classification Item Coarse aggregate Fine aggregate Chemical component Physical character Calcium oxide (as CaO) % 45.0 or less All sulfur (as S) % 2.0 or less Sulfur trioxide (as S03) Metal aluminum % % 0.5 or less Expansion ratio of the mortar by JSCE-F must be 2.0% or less. Metal iron (as Fe) % 1.0 or less Amount of chlorides (as NaCI) % 0.04 or less Density under oven-dry g/cm or more 2.5 or more Rate of water absorption % 3.0 or less 3.0 or less Soundness % 12 or less 10 or less Solid volume percentage for shape determination % Percentage of abrasion % 40 or less 55 or more 53 or more 40 Amount of material passing standard sieve 75!J m in 1.0 or less 7.0 or less aggregates 9) Note 9):Amount of material passing standard" sieve 75 f-l m in aggregates when wearing the surface of concrete out is made into 1.0% or less with molten-slag coarse aggregate, and is made into 5.0% or less by the molten-slag fine aggregate. Table 5 Quality of molten-slag fine aggregate (TR A 0016:2002) Classification Item Fine aggregate Chemical component Physical character Calcium oxide (as CaO) % 45.0 or less All sulfur (as S) % 2.0 or less Sulfur trioxide (as S03) % 0.5 or less Metal aluminum % Expansion ratio of the mortar by Annex must be 2.0% or less. Metal iron (as Fe) % 1.0 or less Amount of chlorides (as NaCI) % 0.04 or less Density under oven-dry g/cm or more Rate of water absorption % 3.0 or less Soundness % 10 or less Solid volume percentage for shape determination % 53 or more Percentage of abrasion Amount of material passing standard sieve 75!J m in aggregates 10) 7.0 or less Note 10) :Amount of material passing standard sieve 75 f-l m in aggregates when wearing the surface of concrete out is made into 5.0% or less by the molten-slag fine aggregate. When using municipal-solid-waste incineration ashes, a sewage sludge and its incineration ashes, the leach-out problem of toxic substances, such as heavy metals, was a big problem. Although based also on the manufacture method, it is becoming clear by melting and slag-izing municipal-solid-waste incineration ashes, a sewage sludge and its incineration ashes that the leach-out of toxic substance does not pose so big a problem. We decided to examine the leach-out of toxic substance using fine aggregate (adjusting the particle size of fine aggregate in the case of coarse aggregate) bearing in 96

8 mind the case where molten slag is kept as aggregate. And the leach-out examination result must satisfy the environment quality control (the previous Environment Agency) concerning contamination of soil. The quality of molten-slag aggregates specified by JCI Standard Proposal is shown in Table 4. Regarding the Standard Proposal of the JCI, it expects to progress to the stipulation of TR or JIS in consideration of the activity result of the molten-slag standardization committee in the "standardization investigation about construction materials-related recycling system" committee currently established in the Japan Testing Center for Construction Materials (the committee chairman is Professor Akihiko Yoda at Ashikaga Institute of Technology) etc. In November 2001, JCI established the second recycling standardization committee in co-operation with the Japan Testing Center for Construction Materials to make a draft proposal of TR. After 4 months active investigation and discussion, the draft of TR regarding molten-slag fine aggregate could be published. The quality of molten-slag fine aggregates specified by TR A 0016 is shown in Table 5. Table 5 is almost the same as Table 4 regarding to the quality of molten-slag fine aggregate. The content of Annex in TR A 0016 is a same one of JSCE-F mentioned in Table 4. In TR A 0016, through practical experience we found that the application of molten-slag fine aggregate is limited to the concrete products. We expect not only stipulating JIS of molten-slag fine aggregate but also stipulating JIS of molten-slag coarse aggregate in the following stage extension of use. 7. TR Stipulation of Crushed Stone Powder JCI A 5004 (Manufactured sand for concrete) was standardized in Crushed sand has since then been used as a substitute for natural fine aggregate, with the annual product amounting to 34million tons in 1998, which accounts for 16% of the total fine aggregate for concrete in Japan. When crushed stone/sand is manufactured, fine crushed stone powder equivalent to 1 to 2% of the finished products is said to be generated. JCI Standard Proposal of limestone ground-granulated powder for concrete generated during crushing of limestone have already become available as "Limestone powder for concrete", making the resource 1 00% recyclable [2]. However, powder generated from other types of stones are mostly wasted or dumped. Equipment for crushed sand production is roughly classified into two types: dry systems and wet systems with different post-production treatment procedures. Powders generated from dry and wet systems are referred to as "crushed stone powder" and "sludge", respectively. Utilization and recycling of crushed stone powder and sludge are in urgent demand at stone mills, as they incur a high cost of post-production treatment of such powders. Table 6 Quality of crushed stone powder (TR A 0015:2002) Item Regulation value Moisture % 1.0 or less Density gfcm or more Flow value ratio % 90 or more Degree index of activity (at 28 days) % 60 or more Parts for 75.u m residue % 5 or less Amount of methylene blue adsorption mgfg 10.0 or less Meanwhile, increases in the varieties of concrete (e.g., increased strength and fluidity) and aggregate (e.g., crushed stone, crushed sand, and aggregates of various slag) have substantially changed the performances required of mineral admixtures. For instance, excessive cement and mineral admixtures are used for high fluidity concrete to impart segregation resistance, resulting in 97

9 production and use of concrete with a strength higher than required. Development of a mineral admixture that imparts segregation resistance without increasing the strength is therefore anticipated for high fluidity concrete. Increased use of crushed sand also poses a problem of possible segregation due to insufficient fine powder content. Active research on the utilization of crushed stone powder was conducted in the 1990s by Japanese researchers and engineers. Concerning crushed stone powder, it is limited to what passes through a 75 J.L m sieve in which the by-product is separated by dry process at the time of manufacture of a crushed stone or a crushed sand, and the draft proposal of TR was proposed. Such crushed stone powder may be used for the purpose of increasing the material's separation resistance of concrete. The cause of the limitation as mentioned above is that the direction of the fine powder which passes through a 75 J.L m sieve can lessen a unit weight of water from the examination results of mortar and concrete. Moreover, although it was thought possible to also use the crushed stone powder from drying cake manufactured by wet process, experiment data was insufficient, so it was limited to dry type. The quality of specified crushed-stone powder is shown in Table 6. In addition, regarding limestone ground granulated powder, JCI Standard Proposal of "Limestone powder for concrete" is already stipulated by JCI, and if it depends on this, 100% recycling is possible [2]. 8. Conclusion The results of the research committee's investigation into the standardization of the practical use of technology of recycling materials in concrete which was established in JCI in 1998 and 2001, have been shown. From the results of the first recycling standardization committee,..lis R 5214 (Eco-cement), TR R 0002 (Eco-cement) and TR A 0006 (Concrete using recycled aggregate) have already been released. The draft of TR of crushed-stone powder was presented, and the specifications of the molten-slag aggregate of municipal solid waste and sewage sludge were also presented as a JCI Standard Proposal. From the results of the second recycling standardization committee which was established in 2001, TR A 0016 (Molten-slag fine aggregate for concrete) is determined to be released in TR A 0015 (Crushed stone powder for concrete) is also determined to be released at the same day of TR A The paper focused on the areas which resulted in this standardization. Unfortunately, it seems that concrete made using recycled materials would result in a reduction in quality. Even the quality of concrete would be varied. However, in appreciating the worries of our society regarding environmental problems, we would like to propose the standardization of recycling materials used in concrete. It would be tremendous if this proposal could be adopted by JIS from now on, and at the same time be accepted by the people of Japan, so a new industry can be born. As members of the recycling standardization committee, we received great cooperation and great support from the convenor of WG, and other committee members. Our gratitude is to all involved. References [1] Standards Department in Agency of Industrial Science and Technology, "About foundation of the Technical Report (TR) system," Standardization journal, Vo1.27, 1996,p.7 [2] JCI Standard Proposal "Limestone powder for concrete", Japan Concrete Institute,