JP4248621B2

JP4248621B2 - Manufacturing method of recycled aggregate

Info

Publication number: JP4248621B2
Application number: JP15858698A
Authority: JP
Inventors: 勝史小野; 剛章大神; 悟藤井
Original assignee: Taiheiyo Cement Corp
Current assignee: Taiheiyo Cement Corp
Priority date: 1998-05-22
Filing date: 1998-05-22
Publication date: 2009-04-02
Anticipated expiration: 2018-05-22
Also published as: JPH11335149A

Description

【０００１】
【発明の属する技術分野】
本発明はコンクリート廃材から骨材、とりわけ不純物付着量が少ない細骨材を再生製造する方法に関する。
【０００２】
【従来技術とその問題点】
建造物の解体や改良・改築に伴い、多量のコンクリート廃材が発生する。このようなコンクリート廃材のおよそ半数は道路舗装用路盤材や埋め戻し材等に再利用されているが、その再利用量には限界があり、残りは殆どが廃棄処分にされている。廃棄処分策としては主に埋立処理されているが、昨今では埋立処分場の枯渇、周辺環境に与える影響、廃棄処理に係わるコストの上昇などの諸問題が顕在化し、従来廃棄処分されていたコンクリート廃材についても更なる再資源化への活用策が急がれている。
【０００３】
一方、コンクリートには骨材が大量に使用されており、水和硬化組成物中に骨材が原形のまま固定されている。骨材の中でも砂利、河砂等の良質の天然骨材は枯渇しつつあって、また自然環境保護の点からも採取が困難になっており、骨材資源の枯渇問題解消とコンクリート廃材の有効活用の両面から、コンクリート廃材から含有骨材を回収し、再利用することが検討されている。
【０００４】
しかるに、コンクリート廃材を、例えば含有骨材の最大寸法に近い大きさ以下に破砕しただけの破砕物は、骨材に、骨材を結合していたセメントペーストが付着した粒や塊となっており、加えてセメントペーストの微小粉粒も混在している。セメントペーストは通常の骨材に比べると強度的にもかなり低く脆弱である為、骨材として再利用するとコンクリートの強度や耐久性が著しく低下する。このため、骨材に付着したセメントペースト分や混在するセメントペースト粒を除去する試みが行われているが、従来の機械的除去手法では実用上支障を生じない程度まで付着ペーストを除去するのは骨材粒径が小さくなるほど容易ではない。特開平８−１０９０５２号や特開平８−１９８６５２号には、コンクリート廃材を数百度以上に加熱し、付着セメントペーストを脱水することで脆弱化させたり、骨材とセメントペーストとの熱膨張差から付着強度を低減させたりすることで、後の機械的手法による骨材からのセメントペースト剥離を容易にした再生骨材製造の前処理技術が開示されている。一般にこのような加熱処理は、温度を高くするほど剥離し易くなる。しかし、高温加熱を行うと骨材自身の強度や耐久性が劣化することがあり、また加熱設備や光熱費の面で処理コストが高騰する。更に、骨材からセメントペーストを剥離し易い状態にしても、後の機械的手法によるペースト剥離工程では、例えば最も一般的な粉砕用ミル類を用いた磨砕手法などでは、一旦剥離したセメントペースト微粉が骨材に再付着し易く、また分離したセメントペースト微粉が磨砕中に緩衝材となって磨砕効率が低下する。
【０００５】
【発明が解決しようとする課題】
この発明は、コンクリート廃材から、含有骨材を再生製造するに際し、セメントペースト除去処理工程中での骨材へのペースト再付着が起こらず、また優れたセメントペースト除去効率によって、付着セメントペーストが著しく少なく、かつ混入セメントペースト粒が殆ど無い良質の骨材を高い回収率で比較的安価に再生製造する方法を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明者らは、コンクリート廃材を破砕した破砕物の粒度とセメントペースト含有率との関係に着目した。本発明者らによるこの関係に対する事前調査結果は、セメントペースト含有率が、破砕物粒径が５ｍｍ以上のものでは３％未満（重量比率、以下同様）であり、１．２ｍｍ以上５ｍｍ未満のものでは５％未満、０．１５ｍｍ以上１．２ｍｍ未満では概ね２０％前後、０．１５ｍｍ未満のものでは約７０％以上であり、０．１５ｍｍ未満の破砕物ではセメントペーストのみからなる粒が大量に含まれていた。このことから本発明者らは、コンクリート廃材を概ね含有骨材最大径以下となるように破砕し、粒径０．１５ｍｍの破砕物を排除し、５ｍｍ以上の粒径のものを粗骨材並びに１．２〜５ｍｍの粒径のものを細骨材としてそのまま回収し、粒径０．１５〜１．２ｍｍの破砕物からセメントペースト分を剥離除去することを検討した結果、該破砕物を比較的低温で３％以下の含水率に乾燥せしめ、これを磨砕処理しながら０．１５ｍｍの磨砕粉を除去するだけで、セメントペースト含有量が著しく低減された細骨材が高収率で得られることを見出し、本発明を完成するに至った。
【０００７】
即ち、本発明は、コンクリート廃材を該廃材中の含有骨材の最大径の約０．８〜１．２倍以下に破砕し、破砕物を分級し、粒径５ｍｍ以上の粒を粗骨材、粒径１．２ｍｍ以上で５ｍｍ未満の粒を細骨材としてそれぞれ回収し、また粒径０．１５ｍｍ未満の粒を除去し、粒径０．１５〜１．２ｍｍ未満の粒については含水率３％以下に乾燥させた後、これを粒径０．１５ｍｍ未満の粒子を排出除去しながら磨砕して付着セメントペーストを骨材から剥脱除去せしめ、粒径０．１５ｍｍ以上の粒を細骨材として回収することを特徴とする再生骨材の製造方法である。
【０００８】
また本発明は、乾燥が１００℃以下の加熱により行うことを特徴とする前記の再生骨材の製造方法である。
【０００９】
また本発明は、磨砕が磨砕助剤を添加して行うことを特徴とする前記何れかの再生骨材の製造方法である。
【００１０】
【発明の実施の形態】
本発明に於けるコンクリート廃材の発生源や採取法は特に限定されないが、一般には建造物の解体や改良・改築等により発生した廃材からコンクリート廃材を任意の手段で選別する。
【００１１】
選別された該コンクリート廃材を破砕する。破砕物の大きさは該廃材中の含有骨材の最大径の約０．８〜１．２倍以下、好ましくは１０ｍｍ以下にする。破砕物粒径が廃材中の含有骨材の最大径の約０．８〜１．２倍を越えるものがあると破砕粒中のセメントペースト含有量が相対的に多くなりすぎるため後工程でのセメントペースト除去処理が困難となることがあるので望ましくない。また、概ね１０ｍｍ以下に破砕した場合は、５ｍｍ未満の粒子について次工程以降の細骨材回収処理がより行い易くなる。破砕に使用する破砕機はコンクリート廃材の大きさに応じて適宜選定すれば良く、特に限定はされないが、一例として大型廃材であればジョークラッシャーやジャイレトリークラッシャー、比較的小型の廃材であればインパクトクラッシャーやコーンクラッシャー等を用いると破砕粒径の制御が比較的行い易い。破砕物は、公知の任意の分級手法、例えば楕円振動篩やジャイロシフター等を用いて分級し、粒径５ｍｍ以上の破砕粒は粗骨材、粒径１．２ｍｍ以上で５ｍｍ未満の破砕粒は細骨材としてそのまま回収する。又、粒径０．１５ｍｍ未満のものは大部分がセメントペースト成分であるため、生産効率の点から除去するのが望ましい。
【００１２】
粒径０．１５ｍｍ未満の粒子を除去した粒径１．２ｍｍ未満の破砕粒については、乾燥し含水率を３％以下にする。乾燥温度は処理コストの上昇を防ぎ、また骨材成分の熱変質を防ぐ理由から低温が好ましく、１００℃以下、より望ましくは５０℃前後で加熱するのが良い。乾燥は対象とする破砕粒の含水率が３％以下になる迄行う。含水率が３％以下となった粒は骨材付着セメントペースト中の付着水や結晶水の一部が概ね除去されて付着強度が低下しセメントペーストが骨材から剥脱し易くなる。乾燥後速やかに乾燥粒を、例えばチューブミル、ボールミル又はロッドミル等の公知の粉砕機を用いて磨砕処理を行い、骨材付着セメントペーストを骨材から剥離させ、更には混在するセメントペースト粒や剥離物を粒径０．１５ｍｍ未満となるように磨砕する。磨砕処理は、一般の粉砕用媒体を用いても或いは粉砕媒体を用いることなく被処理物による共擦りを行っても良い。更に磨砕処理に於いては磨砕助剤を内容物全量の約０．０５〜０．２重量％程度加えても良い。該磨砕助剤としては、公知の粉砕用助剤であれば特に限定されないが、例えば、ジエチレングリコール、エタノール並びにトリエタノールアミンなどが好適である。磨砕処理は処理時に発生する０．１５ｍｍ未満の微粉を磨砕容器外部へ常時排出しながら行う。これは磨砕によって骨材から剥脱されたセメントペースト粉は磨砕中の応力により微粒子になるほど骨材へ物理的再付着が起こり易いのでこれを避けることと、このような微粉が磨砕媒体と被処理物或いは被処理物との間の緩衝材となって磨砕効率が低減しセメントペースト剥脱効率が著しく低下するのを防ぐためである。磨砕時に発生した０．１５ｍｍ未満の微粉を磨砕中に磨砕容器外部へ常時排除する方法は、例えば磨砕容器に０．１５ｍｍのスリットなどの開口部を設けることによって対応できる。該スリットは比較的小規模なものでも十分効果が見られるが、余りに多いと容器壁による磨砕効果が低下することがあるので開口部面積は破砕機容器内表面積の概ね２％以内とするのが望ましい。磨砕時間、磨砕力等は処理量や処理物の平均粒径等に応じて定めることができるが、目安の一例としては、ボールミル粉砕機を用いての共擦り処理の場合、処理物量：１０Ｋｇ、ミル容積：０．０７ｍ³、処理物の平均粒径：０．３ｍｍ、ミル回転速度：４０ｒｐｍである場合、処理時間は２０〜３０分程度とすることができる。また前記ミルの場合では０．１５ｍｍ幅のスリット部を長さ１５０ｍｍに渡ってミル側壁面に有したものを用いる。この磨砕処理を終えた粒はそのまま細骨材として回収しても良いが、より望ましくは再度分級を行い、０．１５ｍｍ以上の粒のみを細骨材として回収する。
【００１３】
【実施例】
以下、本発明の製造方法を実施例を用いて具体的に説明する。
［実施例１］含有骨材の最大直径約２５ｍｍ、粗骨材含有率４０重量％、細骨材含有率３０重量％のコンクリート廃材２５Ｋｇをジョークラッシャー破砕機で約２０ｍｍ以下に破砕した。破砕粒を振動篩により分級し、各粒度別に骨材に付着するセメントペースト含有率を調べた。破砕粒の粒度分布とセメントペースト含有率を表１に示す。尚、セメントペーストの含有率は、ＪＩＳＲ−５２０２に準じた化学分析法により求まるＣａより算出した。
【００１４】
【表１】

【００１５】
分級後、粒径５ｍｍ以上の粒は粗骨材として、粒径１．２ｍｍ以上５ｍｍ未満の粒は細骨材としてそれぞれそのまま回収した。粒径１．２ｍｍ未満のものについては４５℃で３日間乾燥させた後、乾燥物の全量を、磨砕機として長さ１５０ｍｍで幅０．１５ｍｍのスリットを設けた内容積０．０６６ｍ³のボールミルに鉄製の直径約２０ｃｍ球形磨砕媒体総量約０．００７ｍ³と共に投入し、回転速度４０ｒｐｍで１０分間磨砕を行った。磨砕後、被磨砕物を篩に通し、粒径０．１５ｍｍ以上のものを細骨材として回収した。回収できた粗骨材及び細骨材の全量、回収率、及びセメントペースト含有率、ＪＩＳＡ−１１０９、ＪＩＳＡ−１１１０に準じてそれぞれ測定した比重及び吸水率の各結果を表２に表す。
【００１６】
【表２】

【００１７】
［実施例２］磨砕の際にボールミル内容物総重量の約０．２重量％相当のジエチレングリコールを加えた以外は前記実施例１と同様の方法で得た同様のコンクリート廃材破砕物を実施例１と同様の方法・条件で処理し、細骨材と粗骨材を回収した。回収できた粗骨材及び細骨材の全量、回収率、及び実施例１と同様の方法により求めたセメントペースト含有率、比重、吸水率を表３に表す。
【００１８】
【表３】

【００１９】
［比較例１］前記実施例１と同様の方法で得た同様のコンクリート廃材破砕粒を振動篩で分級し、分級後、粒径５ｍｍ以上の粒は粗骨材として、粒径１．２ｍｍ以上５ｍｍ未満の粒は細骨材としてそれぞれそのまま回収した。粒径１．２ｍｍ未満のものは４５℃で３日間乾燥させた後、乾燥物を、磨砕機としてスリット等の微粉排用開口を有しない内容積０．０６６ｍ³のボールミルに鉄製の直径約２０ｃｍ球形磨砕媒体総量約０．００７ｍ³と共に投入し、回転速度４０ｒｐｍで１０分間磨砕を行った。磨砕後、被磨砕物を篩に通し、粒径０．１５ｍｍ以上のものを細骨材として回収した。回収できた粗骨材及び細骨材の全量、回収率、及び実施例１と同様の方法により求めたセメントペースト含有率、比重、吸水率を表４に表す。
【００２０】
【表４】

【００２１】
［比較例２］前記実施例１と同様の方法で得た同様のコンクリート廃材破砕粒を振動篩で分級し、粒径５ｍｍ以上の粒は粗骨材として、粒径１．２ｍｍ以上５ｍｍ未満の粒は細骨材としてそれぞれそのまま回収し、１．２ｍｍ未満の粒は吸水率を測定後、乾燥させずに実施例１と同様のボールミル磨砕機に実施例１と同じ磨砕媒体約０．００７ｍ³と共に全て入れ、回転速度４０ｒｐｍで６０分間磨砕を行った。磨砕後、被磨砕物を分級し、粒径０．１５ｍｍ以上のものを細骨材として回収した。回収できた粗骨材及び細骨材の全量、回収率、及び実施例１と同様の方法により求めたセメントペースト含有率、比重、吸水率を表５に表す。
【００２２】
【表５】

【００２３】
【発明の効果】
本発明の製造方法によれば、コンクリート廃材からセメントペースト含有量が少ない粗骨材と、とりわけ従来困難であったセメントペースト分が著しく少ない細骨材を、優れた生産効率と高い回収率で比較的安価に得ることができる。また本発明の製造方法では磨砕処理によって骨材と分離された特定粒径以下のセメントペースト微粉も回収することも可能であるため、例えば固化材やフィラー材原料などとして再利用することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for regenerating and manufacturing an aggregate, in particular a fine aggregate with a small amount of impurities, from concrete waste.
[0002]
[Prior art and its problems]
A lot of concrete waste materials are generated with the dismantling, improvement and reconstruction of the building. Approximately half of such concrete waste is reused for road pavement and backfill materials, but the amount of reuse is limited, and most of the remainder is discarded. The landfill treatment is mainly used as a disposal measure. However, in recent years, various problems such as depletion of the landfill site, the impact on the surrounding environment, and an increase in costs related to the disposal process have become obvious, and the concrete that has been disposed of in the past. There is an urgent need to utilize waste materials for further recycling.
[0003]
On the other hand, aggregate is used in large quantities in concrete, and the aggregate is fixed in its original form in the hydrated and cured composition. Among the aggregates, high-quality natural aggregates such as gravel and river sand are depleting, and it is difficult to collect them from the viewpoint of protecting the natural environment, eliminating the problem of depletion of aggregate resources and effective use of concrete waste. From both sides of utilization, it is considered to collect the aggregate from the concrete waste and reuse it.
[0004]
However, for example, the crushed material that has just been crushed to a size close to the maximum size of the aggregates contained in the concrete waste has become grains and lumps with cement paste attached to the aggregate. In addition, fine particles of cement paste are also mixed. Since cement paste is considerably low in strength and fragile compared to ordinary aggregates, the strength and durability of concrete are significantly reduced when reused as aggregates. For this reason, attempts have been made to remove cement paste adhering to aggregates and mixed cement paste grains. However, the conventional mechanical removal method removes the adhering paste to such an extent that it does not cause practical problems. It is not as easy as the aggregate particle size becomes smaller. In JP-A-8-109052 and JP-A-8-198652, concrete waste is heated to several hundred degrees or more, and the adhering cement paste is dehydrated, or the thermal expansion difference between the aggregate and the cement paste is considered. There has been disclosed a pretreatment technique for producing recycled aggregates that facilitates peeling of the cement paste from the aggregates by subsequent mechanical techniques by reducing the adhesion strength. In general, such heat treatment becomes easier to peel off as the temperature increases. However, when high-temperature heating is performed, the strength and durability of the aggregate itself may deteriorate, and the processing cost increases in terms of heating equipment and utility costs. Further, even if the cement paste is easily peeled from the aggregate, the cement paste once peeled off in the paste peeling process by a mechanical method later, for example, by the grinding method using the most common grinding mills, etc. The fine powder easily reattaches to the aggregate, and the separated cement paste fine powder becomes a buffer material during grinding, resulting in a reduction in grinding efficiency.
[0005]
[Problems to be solved by the invention]
In the present invention, when the contained aggregate is regenerated from waste concrete, the paste is not reattached to the aggregate during the cement paste removal process, and the cement paste is significantly removed due to the excellent cement paste removal efficiency. It is an object of the present invention to provide a method for regenerating and producing a high-quality aggregate with a small amount and almost no cement paste grains at a relatively low cost with a high recovery rate.
[0006]
[Means for Solving the Problems]
The inventors paid attention to the relationship between the particle size of the crushed material obtained by crushing the concrete waste material and the cement paste content. As a result of preliminary investigation on this relationship by the inventors, the cement paste content is less than 3% (weight ratio, the same applies hereinafter) when the particle size of the crushed material is 5 mm or more, and 1.2 mm or more and less than 5 mm. Is less than 5%, approximately 20% when 0.15 mm or more and less than 1.2 mm, approximately 70% or more when 0.15 mm or less, and a crushed material less than 0.15 mm contains a large amount of grains consisting only of cement paste. It was included. From this, the present inventors crushed the concrete waste material so as to be approximately equal to or less than the maximum aggregate diameter, excluded crushed material having a particle size of 0.15 mm, and coarse aggregates having a particle size of 5 mm or more and As a result of examining the removal of the cement paste from the crushed material having a particle size of 0.15 to 1.2 mm as a fine aggregate, the particles having a particle size of 1.2 to 5 mm were collected as they were. The fine aggregate with significantly reduced cement paste content can be obtained in high yields by simply drying at a low temperature to a moisture content of 3% or less and removing 0.15 mm of grinding powder while grinding this. As a result, the present invention was completed.
[0007]
That is, the present invention crushes concrete waste into about 0.8 to 1.2 times the maximum diameter of the aggregate contained in the waste, classifies the crushed material, and particles having a particle size of 5 mm or more are coarse aggregate. The particles having a particle size of 1.2 mm or more and less than 5 mm are collected as fine aggregates, and the particles having a particle size of less than 0.15 mm are removed. After drying to 3% or less, this is ground while discharging and removing particles with a particle size of less than 0.15 mm, and the attached cement paste is exfoliated and removed from the aggregate. A method for producing a recycled aggregate, characterized in that the recycled aggregate is recovered.
[0008]
Further, the present invention is the above-described method for producing a recycled aggregate, wherein drying is performed by heating at 100 ° C. or less.
[0009]
Further, the present invention is the method for producing any one of the above-mentioned recycled aggregates, wherein the grinding is performed by adding a grinding aid.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
There are no particular limitations on the source and collection method of the concrete waste material in the present invention, but in general, the concrete waste material is selected by any means from the waste material generated by the dismantling, improvement or reconstruction of the building.
[0011]
The selected concrete waste material is crushed. The size of the crushed material is about 0.8 to 1.2 times or less, preferably 10 mm or less, of the maximum diameter of the aggregate contained in the waste material. If there is one whose crushed particle size exceeds about 0.8 to 1.2 times the maximum diameter of the aggregate contained in the waste, the cement paste content in the crushed grain will be too much, so in the subsequent process This is not desirable because the cement paste removal process may be difficult. Moreover, when it crushes to about 10 mm or less, it becomes easier to perform the fine aggregate recovery process after the next process for particles of less than 5 mm. The crusher used for crushing may be appropriately selected according to the size of the concrete waste material, and is not particularly limited. For example, if it is a large waste material, it will be a jaw crusher or a gyratory crusher, if it is a relatively small waste material. When an impact crusher, a cone crusher, or the like is used, the crushing particle size can be controlled relatively easily. The crushed material is classified using any known classification method, for example, an elliptical vibrating sieve or a gyro shifter, etc., crushed particles with a particle size of 5 mm or more are coarse aggregate, and crushed particles with a particle size of 1.2 mm or more and less than 5 mm are It is recovered as a fine aggregate. Moreover, since the thing with a particle size of less than 0.15 mm is mostly a cement paste component, it is desirable to remove from the point of production efficiency.
[0012]
The crushed particles having a particle size of less than 1.2 mm from which particles having a particle size of less than 0.15 mm have been removed are dried to a moisture content of 3% or less. The drying temperature is preferably a low temperature for the purpose of preventing an increase in processing cost and preventing thermal deterioration of the aggregate component, and heating at 100 ° C. or lower, more desirably around 50 ° C. is preferable. Drying is performed until the water content of the target crushed grains is 3% or less. Grains having a moisture content of 3% or less are substantially removed of the adhering water and crystallization water in the aggregate adhering cement paste, the adhering strength is lowered, and the cement paste is easily detached from the aggregate. Immediately after drying, the dried grains are subjected to a grinding treatment using a known pulverizer such as a tube mill, a ball mill, or a rod mill to separate the aggregate-attached cement paste from the aggregate, and further to the mixed cement paste grains or The exfoliated material is ground to a particle size of less than 0.15 mm. In the grinding treatment, a general grinding medium may be used, or co-rubbing with an object to be processed may be performed without using a grinding medium. Further, in the grinding treatment, a grinding aid may be added in an amount of about 0.05 to 0.2% by weight based on the total content. The grinding aid is not particularly limited as long as it is a known grinding aid. For example, diethylene glycol, ethanol, triethanolamine, and the like are suitable. The grinding treatment is performed while constantly discharging the fine powder of less than 0.15 mm generated during the treatment to the outside of the grinding container. This is because the cement paste powder exfoliated from the aggregate by grinding is more susceptible to physical reattachment to the aggregate due to the stress during grinding. This is because it becomes a buffer material between the object to be processed or the object to be processed, and the grinding efficiency is reduced to prevent the cement paste exfoliation efficiency from being significantly reduced. A method of constantly removing fine powder of less than 0.15 mm generated during grinding to the outside of the grinding container during grinding can be achieved by, for example, providing an opening such as a 0.15 mm slit in the grinding container. Even if the slit is relatively small, a sufficient effect can be seen, but if it is too large, the grinding effect by the container wall may be reduced, so the opening area should be within about 2% of the surface area in the crusher container. Is desirable. Grinding time, grinding power, etc. can be determined according to the amount of treatment and the average particle size of the treated material. As an example of the standard, in the case of co-rubbing treatment using a ball mill grinder, the amount of treated material: In the case of 10 kg, mill volume: 0.07 m ³ , average particle diameter of processed material: 0.3 mm, and mill rotational speed: 40 rpm, the processing time can be about 20 to 30 minutes. In the case of the mill, a slit having a width of 0.15 mm over a length of 150 mm is used on the side wall of the mill. The grains after the grinding treatment may be collected as fine aggregates as they are, but more desirably, classification is performed again, and only grains having a size of 0.15 mm or more are collected as fine aggregates.
[0013]
【Example】
Hereinafter, the production method of the present invention will be specifically described with reference to examples.
[Example 1] A concrete scrap 25 kg having a maximum aggregate diameter of about 25 mm, a coarse aggregate content of 40 wt%, and a fine aggregate content of 30 wt% was crushed to about 20 mm or less by a jaw crusher crusher. The crushed particles were classified with a vibrating sieve, and the cement paste content adhering to the aggregate was examined for each particle size. Table 1 shows the particle size distribution of the crushed grains and the cement paste content. In addition, the content rate of the cement paste was calculated from Ca obtained by a chemical analysis method according to JIS R-5202.
[0014]
[Table 1]

[0015]
After classification, the particles having a particle size of 5 mm or more were collected as coarse aggregates, and the particles having a particle size of 1.2 mm or more and less than 5 mm were collected as fine aggregates as they were. For those having a particle size of less than 1.2 mm, after drying at 45 ° C. for 3 days, the entire amount of the dried product was a ball mill having an internal volume of 0.066 m ³ provided with a slit having a length of 150 mm and a width of 0.15 mm as a grinder. Was added together with a total of about 0.007 m ^{3 of} spherical grinding media made of iron and having a diameter of about 20 cm, and grinding was performed at a rotational speed of 40 rpm for 10 minutes. After grinding, the material to be ground was passed through a sieve, and those having a particle size of 0.15 mm or more were collected as fine aggregates. Table 2 shows the results of the total amount of recovered coarse aggregate and fine aggregate, the recovery rate, the cement paste content, the specific gravity and the water absorption measured according to JIS A-1109 and JIS A-1110, respectively.
[0016]
[Table 2]

[0017]
[Example 2] The same concrete waste crushed material obtained in the same manner as in Example 1 except that diethylene glycol corresponding to about 0.2% by weight of the total weight of the ball mill contents was added during grinding. It processed by the method and conditions similar to 1, and collect | recovered the fine aggregate and the coarse aggregate. Table 3 shows the total amount of recovered coarse and fine aggregates, the recovery rate, and the cement paste content, specific gravity, and water absorption determined by the same method as in Example 1.
[0018]
[Table 3]

[0019]
[Comparative Example 1] The same concrete waste material crushed particles obtained by the same method as in Example 1 were classified with a vibration sieve, and after classification, the particles having a particle size of 5 mm or more were coarse aggregates, and the particle size was 1.2 mm or more. Grains smaller than 5 mm were collected as they were as fine aggregates. Those having a particle size of less than 1.2 mm were dried at 45 ° C. for 3 days, and then the dried product was applied to a ball mill having an internal volume of 0.066 m ³ without a fine powder discharge opening such as a slit as a grinder, and an iron diameter of about 20 cm. The total amount of spherical grinding media was charged together with about 0.007 m ³ , and grinding was performed at a rotational speed of 40 rpm for 10 minutes. After grinding, the material to be ground was passed through a sieve, and those having a particle size of 0.15 mm or more were collected as fine aggregates. Table 4 shows the total amount of recovered coarse aggregate and fine aggregate, the recovery rate, and the cement paste content, specific gravity, and water absorption determined by the same method as in Example 1.
[0020]
[Table 4]

[0021]
[Comparative Example 2] The same concrete waste material crushed particles obtained by the same method as in Example 1 were classified with a vibration sieve, and particles having a particle size of 5 mm or more were coarse aggregates having a particle size of 1.2 mm or more and less than 5 mm. The grains are collected as fine aggregates as they are, and the grains less than 1.2 mm are measured by measuring the water absorption rate, and then dried in a ball mill grinder similar to that in Example 1 without measuring drying. All were put together with ³ , and grinding was performed at a rotational speed of 40 rpm for 60 minutes. After grinding, the materials to be ground were classified, and those having a particle size of 0.15 mm or more were collected as fine aggregates. Table 5 shows the total amount of coarse and fine aggregates recovered, the recovery rate, and the cement paste content, specific gravity, and water absorption determined by the same method as in Example 1.
[0022]
[Table 5]

[0023]
【The invention's effect】
According to the production method of the present invention, a coarse aggregate having a low cement paste content from a concrete waste material and a fine aggregate having an extremely low cement paste content, which has been difficult in the past, are compared with an excellent production efficiency and a high recovery rate. Can be obtained inexpensively. Further, in the production method of the present invention, it is also possible to collect cement paste fine powder having a specific particle size or less separated from the aggregate by grinding treatment, so that it can be reused, for example, as a solidifying material or a filler material raw material. .

Claims

The concrete waste is crushed to about 0.8 to 1.2 times the maximum diameter of the aggregate contained in the waste, the crushed material is classified, and particles with a particle size of 5 mm or more are coarse aggregate, particle size 1.2 mm The particles smaller than 5 mm are collected as fine aggregates as described above, and the particles smaller than 0.15 mm are removed. The water content of the particles smaller than 0.15 to 1.2 mm is heated by heating at 100 ° C. or lower. After drying to 3% or less, this is ground while discharging and removing particles with a particle size of less than 0.15 mm, and the attached cement paste is exfoliated and removed from the aggregate. A method for producing a recycled aggregate, characterized in that the recycled aggregate is collected.

2. The method for producing a recycled aggregate according to claim 1, wherein grinding is performed by adding a grinding aid.