JP5332105B2 - Method for reducing drying shrinkage of concrete with high water absorption recycled aggregate - Google Patents
Method for reducing drying shrinkage of concrete with high water absorption recycled aggregate Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
Description
本発明は、吸水率の高い再生骨材を使用したコンクリートの乾燥収縮低減方法、コンクリート用骨材及びそれを用いてなるコンクリートに関する。 The present invention relates to a method for reducing drying shrinkage of concrete using recycled aggregate having a high water absorption rate, an aggregate for concrete, and a concrete using the same.
近年の砂、砂利等のコンクリート骨材資源環境は、骨材採取の禁止や輸入の制限等、様々な制約を受け枯渇化しており、骨材のリサイクル化や代替骨材の使用が喫緊の課題となっている。その流れの中で骨材の種類は多様化しており、再生骨材、軽量骨材、高炉スラグ骨材等の吸水率の高い骨材も使用されている。 In recent years, the environment of concrete aggregates such as sand and gravel has been exhausted due to various restrictions such as prohibition of aggregate collection and restrictions on imports. It has become. In the flow, the types of aggregates are diversified, and aggregates with high water absorption such as recycled aggregates, lightweight aggregates, blast furnace slag aggregates, and the like are also used.
しかしながら、再生骨材を使用すると、一般的に使用されている普通骨材に比べ、コンクリートの乾燥時の収縮が大きくなる傾向にある。
この乾燥収縮を低減する法としては、例えば、再生骨材に対する水性シラン系吸水防止剤による表面撥水性の付与（特許文献１）のように骨材表面を改質する提案もあるが、コストや手間がかかり、一般的なコンクリートへの適用は難しい。
従って、吸水率の高い再生骨材を使用する場合でも、普通骨材使用時に行われている収縮低減剤や膨張材の使用等で乾燥収縮を軽減する方法が実際的である。
However, when recycled aggregate is used, shrinkage during drying of the concrete tends to be greater than that of commonly used ordinary aggregate.
As a method for reducing the drying shrinkage, for example, there is a proposal to modify the surface of the aggregate, such as imparting surface water repellency to the recycled aggregate with an aqueous silane-based water absorption inhibitor (Patent Document 1). It takes time and is difficult to apply to general concrete.
Therefore, even when a recycled aggregate having a high water absorption rate is used, it is practical to reduce dry shrinkage by using a shrinkage reducing agent or an expansion material that is used when using a normal aggregate.
収縮低減剤は、水に対する表面張力低下能があり、コンクリートに使用すると毛細管張力を低下させ、乾燥収縮を低減すると言われている。収縮低減剤の一般的な使用方法は、セメント質量に対して一定割合の量を、練混ぜ水に溶かしてコンクリート製造時に混入する（以下、「一般添加法」ということがある。）。そして、収縮低減剤の標準的添加量は、収縮低減剤の種類によって異なるが、セメント質量に対して概ね１〜６質量％程度である。 The shrinkage reducing agent has a surface tension reducing ability with respect to water, and when used in concrete, it is said to reduce capillary tension and reduce drying shrinkage. A general method of using the shrinkage reducing agent is to dissolve a certain amount of the cement mass in the kneading water and mix it during concrete production (hereinafter sometimes referred to as “general addition method”). And although the standard addition amount of a shrinkage reducing agent changes with kinds of shrinkage reducing agent, it is about 1-6 mass% about cement mass.
収縮低減剤は、添加量が多いほど収縮低減効果を得られるので、吸水率の高い再生骨材の場合、収縮低減剤を高添加量にすることが考えられるが、収縮低減剤の種類によっては空気連行性や消泡性を有するものがあり、強度低下や凍結融解抵抗性の低下に繋がる場合がある。その場合、コンクリートの空気量調整のため消泡剤やＡＥ剤が必要になり、フレッシュ時のコンクリートの品質管理が複雑になる。
また、収縮低減剤の添加量が過大になると、凝結遅延、強度低下等コンクリートの物性に悪影響を及ぼすことがある。
一方、配（調）合の変更による単位水量の減少には、限界があり、コンクリートの大幅な乾燥収縮低減が望めないのが実状である。
なお、膨張材と収縮低減剤を併用して収縮低減を図る方法は、効果的ではあるがコスト増につながるため、あまり実用的ではない。
Since the shrinkage reducing agent has a shrinkage reducing effect as the addition amount increases, in the case of recycled aggregate with a high water absorption rate, it is conceivable to increase the shrinkage reducing agent, but depending on the type of shrinkage reducing agent Some have air entrainment properties and defoaming properties, which may lead to a decrease in strength and a decrease in freeze-thaw resistance. In that case, an antifoaming agent or an AE agent is required for adjusting the air amount of the concrete, and the quality control of the concrete when fresh is complicated.
Moreover, when the addition amount of a shrinkage reducing agent becomes excessive, it may have a bad influence on the physical properties of concrete, such as a setting delay and a strength fall.
On the other hand, there is a limit to the reduction of the unit water volume due to the change in distribution (condition), and it is actually impossible to expect a drastic reduction in drying shrinkage of concrete.
Note that a method of reducing shrinkage by using an expansion material and a shrinkage reducing agent in combination is effective but leads to an increase in cost, and is not very practical.
本発明は、吸水率の高い再生骨材を使用したコンクリートで問題となる大きい乾燥収縮を低減化する方法であって、従来の収縮低減剤添加法における使用量よりも少量の収縮低減剤で、乾燥収縮の低減ができ、かつ、コンクリートの品質を安定化できる乾燥収縮低減方法を提供することを目的とする。 The present invention is a method for reducing large drying shrinkage, which is a problem in concrete using recycled aggregate having a high water absorption rate, with a small amount of shrinkage reducing agent than the amount used in the conventional shrinkage reducing agent addition method, An object of the present invention is to provide a drying shrinkage reduction method capable of reducing drying shrinkage and stabilizing the quality of concrete.
本発明者は、鋭意検討を行った結果、吸水率３％以上の再生骨材に、収縮低減剤水溶液をプレウェッチングし、これをコンクリートに使用することにより乾燥収縮を低減できることを見出し、本発明を完成した。
すなわち、本発明は、
（１）吸水率３％以上の再生骨材に、低級アルコールのアルキレンオキシド付加物からなる収縮低減剤水溶液をプレウェッチングするコンクリートの乾燥収縮低減方法であって、該再生骨材の表乾質量、該再生骨材の吸水率、及び該収縮低減剤水溶液における収縮低減剤の希釈濃度に基づいて次式（Ｉ）で算出される収縮低減剤添加量が再生骨材に含まれるように溶液散布によりプレウェッチングして得た表面乾燥飽水状態の再生骨材をコンクリートに使用することを特徴とするコンクリートの乾燥収縮低減方法、
収縮低減剤添加量＝再生骨材表乾質量×再生骨材の吸水率×
収縮低減剤希釈濃度 （Ｉ）
（但し、収縮低減剤希釈濃度は０．５〜５質量％）
（２）吸水率３％以上の再生骨材に、低級アルコールのアルキレンオキシド付加物からなる収縮低減剤水溶液をプレウェッチングしてなるコンクリート用骨材であって、
該再生骨材の表乾質量、該再生骨材の吸水率、及び該収縮低減剤水溶液における収縮低減剤の希釈濃度に基づいて次式（Ｉ）で算出される収縮低減剤添加量が再生骨材に含まれるように溶液散布によりプレウェッチングして得た表面乾燥飽水状態の再生骨材としてなるコンクリート用骨材、及び
収縮低減剤添加量＝再生骨材表乾質量×再生骨材の吸水率×
収縮低減剤希釈濃度 （Ｉ）
（但し、収縮低減剤希釈濃度は０．５〜５質量％）
（３）前記（２）記載のコンクリート用骨材を含有してなるコンクリート、
を提供する。
As a result of intensive studies, the present inventors have found that drying shrinkage can be reduced by pre-wetting a shrinkage reducing agent aqueous solution on a recycled aggregate having a water absorption rate of 3% or more and using this in concrete. Completed the invention.
That is, the present invention
(1) A method for reducing dry shrinkage of concrete by prewetting a shrinkage reducing agent aqueous solution comprising an alkylene oxide adduct of a lower alcohol on a recycled aggregate having a water absorption rate of 3% or more, wherein the surface dry mass of the recycled aggregate Spraying the solution so that the amount of shrinkage reducing agent added calculated by the following formula (I) based on the water absorption rate of the recycled aggregate and the dilution concentration of the shrinkage reducing agent in the aqueous solution of shrinkage reducing agent is included in the recycled aggregate A method for reducing drying shrinkage of concrete, characterized by using recycled aggregate in a dry surface saturated state obtained by prewetting with
Shrinkage reducing agent addition amount = reclaimed aggregate surface dry mass x reclaimed aggregate water absorption x
Shrinkage reducing agent dilution concentration (I)
(However, the shrinkage reducing agent dilution concentration is 0.5 to 5% by mass)
(2) A concrete aggregate obtained by pre-wetting a shrinkage reducing agent aqueous solution comprising an alkylene oxide adduct of a lower alcohol to a recycled aggregate having a water absorption rate of 3% or more,
Based on the surface dry mass of the regenerated aggregate, the water absorption rate of the regenerated aggregate, and the dilution concentration of the shrinkage reducing agent in the shrinkage reducing agent aqueous solution, the shrinkage reducing agent addition amount calculated by the following formula (I) is aggregate for concrete comprising a recycled aggregate surface dry water-saturated state obtained by prewetting quenching with a solution sprayed as contained in the wood, and shrinkage reducing agent addition amount = recycled aggregate table dry mass × recycled aggregate Water absorption x
Shrinkage reducing agent dilution concentration (I)
(However, the shrinkage reducing agent dilution concentration is 0.5 to 5% by mass)
(3) Concrete comprising the aggregate for concrete described in (2) above,
I will provide a.
本発明のコンクリートの乾燥収縮低減方法は、吸水率３％以上の再生骨材に、収縮低減剤水溶液をプレウェッチングし、これをコンクリートに使用する方法であり、収縮低減剤はフレッシュコンクリートにおいて主に再生骨材の細孔の内部に水溶液として保持され、一般添加法のように収縮低減剤を練混ぜ水に直接添加混合する方法のような、収縮低減剤が空気連行性や消泡性を有することによる強度低下や凍結融解抵抗性の低下の危惧がなく、また、少量の収縮低減剤で高い効果が得られる、極めて効率的かつ経済的な方法である。
本発明のコンクリート用骨材は、吸水率３％以上の再生骨材に、収縮低減剤水溶液をプレウェッチングしているので、乾燥収縮低減が要求されるコンクリートに利用できる。
本発明のコンクリートは、収縮低減剤水溶液をプレウェッチングした再生骨材を含有しているので、収縮低減剤による空気連行性や消泡性を有する場合の強度低下や凍結融解抵抗性の低下の危惧のない極めて効率的、経済的なコンクリートとして利用できる。
The method for reducing dry shrinkage of concrete according to the present invention is a method of prewetting a shrinkage reducing agent aqueous solution on a recycled aggregate having a water absorption rate of 3% or more, and using this in concrete. The shrinkage reducing agent is mainly used in fresh concrete. In addition, the shrinkage-reducing agent is retained as an aqueous solution inside the pores of the regenerated aggregate, and the shrinkage-reducing agent has air entrainment and defoaming properties, such as the method of adding the shrinkage-reducing agent directly to the kneaded water as in the general addition method. This is an extremely efficient and economical method in which there is no fear of strength reduction or freezing and thawing resistance reduction due to possession, and a high effect can be obtained with a small amount of shrinkage reducing agent.
Since the aggregate for concrete of the present invention is prewetched with a shrinkage reducing agent aqueous solution on recycled aggregate having a water absorption rate of 3% or more, it can be used for concrete that requires a reduction in drying shrinkage.
Since the concrete of the present invention contains recycled aggregate pre-wetched with a shrinkage reducing agent aqueous solution, the strength reduction and freezing and thawing resistance reduction when the shrinkage reducing agent has air entrainment property and defoaming property are reduced. It can be used as extremely efficient and economical concrete without fear.
本発明のコンクリートの乾燥収縮低減方法は、吸水率３％以上の再生骨材に、収縮低減剤水溶液をプレウェッチングし、これをコンクリートに使用することを特徴とするコンクリートの乾燥収縮低減方法である。 The method for reducing dry shrinkage of concrete according to the present invention is a method for reducing dry shrinkage of concrete, characterized by prewetting a shrinkage reducing agent aqueous solution on recycled aggregate having a water absorption rate of 3% or more, and using this for concrete. is there.
再生骨材は、解体したコンクリート塊を破砕、粒度調整をして製造されるもので、原骨材とそれに付着したセメントペースト・モルタル分（以下、原モルタル）とからなる。
再生骨材の表面に付着している原モルタルの品質が低下していたり、付着量が多い場合には、再生骨材自体の品質が低下する。再生骨材は、粒度５ｍｍを境に細骨材と粗骨材に分類される。
また、再生骨材は、再生コンクリートの利用拡大と高品質化を図るために、特開２００３−２７２４号公報に開示されているような加熱すりもみ法やスクリュー磨砕法などの処理によって原モルタルを可能な限り除去したものであってもよいが、本発明方法による収縮低減効果を得るためには、吸水率が３％以上であることを要する。
本発明において吸水率は、粗骨材の場合、ＪＩＳ Ａ １１１０（粗骨材の密度及び吸水率試験方法）に準拠し、細骨材の場合は、ＪＩＳ Ａ １１０９（細骨材の密度及び吸水率試験方法）に準拠して求められる。
Recycled aggregate is produced by crushing a demolished concrete block and adjusting the particle size, and consists of raw aggregate and cement paste and mortar (hereinafter referred to as original mortar) adhering to the aggregate.
If the quality of the original mortar adhering to the surface of the regenerated aggregate is reduced or the amount of adhesion is large, the quality of the regenerated aggregate itself is deteriorated. Recycled aggregates are classified into fine aggregates and coarse aggregates with a grain size of 5 mm as a boundary.
Further, in order to increase the use and quality of recycled concrete, the recycled aggregate can be obtained by processing the raw mortar by a process such as a hot grinding method or a screw grinding method as disclosed in JP-A-2003-2724. Although it may be removed as much as possible, in order to obtain the shrinkage reduction effect by the method of the present invention, it is necessary that the water absorption is 3% or more.
In the present invention, the water absorption is in accordance with JIS A 1110 (Coarse Aggregate Density and Water Absorption Test Method) in the case of coarse aggregate, and in the case of fine aggregate, JIS A 1109 (fine aggregate density and water absorption). Rate test method).
本発明のコンクリートの乾燥収縮低減方法、骨材及びコンクリートに用いられる収縮低減剤としては、特に限定されず、１価の低級アルコールのアルキレンオキシド付加物、２〜８価のアルコールのアルキレンオキシド付加物、低級アルキルアミンのアルキレンオキシド付加物、アルコール系化合物、グリコールエーテル・アミノアルコール誘導体、ポリエーテル系化合物、低分子量アルキレンオキシド共重合体など、公知の収縮低減剤をいずれも使用することができる。
これらの中でもポリオキシエチレンポリオキシプロピレンモノブチルエーテル、ポリオキシエチレンモノメチルエーテルなどの低級アルコールのアルキレンオキシド付加物が好適に用いられる。
The method for reducing drying shrinkage of concrete according to the present invention, and the shrinkage reducing agent used for aggregate and concrete are not particularly limited, and alkylene oxide adducts of monovalent lower alcohols and alkylene oxide adducts of 2 to 8 alcohols. Any known shrinkage reducing agent such as an alkylene oxide adduct of a lower alkylamine, an alcohol compound, a glycol ether / amino alcohol derivative, a polyether compound or a low molecular weight alkylene oxide copolymer can be used.
Among these, alkylene oxide adducts of lower alcohols such as polyoxyethylene polyoxypropylene monobutyl ether and polyoxyethylene monomethyl ether are preferably used.
本発明のコンクリートの乾燥収縮低減方法、骨材及びコンクリートにおいて、高吸水率再生骨材の収縮低減剤水溶液によるプレウェッチングは、予め再生骨材の吸水率Ｑ（％）を前記ＪＩＳの方法に準拠して測定し、再生骨材の表乾質量（ｋｇ）に、吸水率Ｑ（％）と収縮低減剤の希釈濃度（％）を乗じた量を対象骨材に散布する。配合コンクリートにおける収縮低減剤の添加量は、
収縮低減剤添加量＝再生骨材質量×再生骨材の吸水率×収縮低減剤希釈濃度
で表される。
一般添加法における収縮低減剤の使用量は、水セメント比（Ｗ／Ｃ）によって異なるが、通常、２〜９ｋｇ／ｍ3（対セメントの１〜２質量％）であるが、本発明の高吸水率再生骨材への収縮低減剤水溶液のプレウェッチング（以下、「溶液散布法」ということがある。）によれば、Ｗ／Ｃ、骨材の吸水率によって異なるが０．５〜８ｋｇ／ｍ3で一般添加法よりも少量の使用量で同等以上の乾燥収縮低減効果を得ることが可能である。その際、上記収縮低減剤希釈濃度としては、通常０．５〜８質量％、より好ましくは１〜５質量％である。
一般に生コン工場では、骨材を湿潤状態でサイロやストックヤードに貯蔵しており、吸水率の大きい骨材は、コンクリートを製造する前に水でプレウェッチングが施され、湿潤状態を保つようにしている。本発明では、それらの設備を利用して一般的な水のみによるプレウェッチングに替えて、高吸水率再生骨材に予め収縮低減剤水溶液をプレウェッチングすればよい。
In the method of reducing dry shrinkage of concrete according to the present invention, aggregate and concrete, pre-wetting with an aqueous solution of shrinkage reducing agent for recycled aggregate with high water absorption rate is obtained by using the water absorption rate Q (%) of recycled aggregate in advance according to the method of JIS. Measure in accordance with the above, and spray the target aggregate with an amount obtained by multiplying the dry mass (kg) of the recycled aggregate by the water absorption Q (%) and the dilution concentration (%) of the shrinkage reducing agent. The amount of shrinkage reducing agent added to the blended concrete is
Shrinkage reducing agent addition amount = regenerated aggregate mass × recycled aggregate water absorption × shrinkage reducing agent dilution concentration.
The amount of the shrinkage reducing agent used in the general addition method varies depending on the water cement ratio (W / C), but is usually 2 to 9 kg / m 3 (1 to 2% by mass of cement). According to the pre-wetting of the shrinkage reducing agent aqueous solution to the water-absorbing recycled aggregate (hereinafter sometimes referred to as “solution spraying method”), it varies depending on W / C and the water-absorbing ratio of the aggregate, but 0.5-8 kg. It is possible to obtain a drying shrinkage reduction effect equal to or higher than that of the general addition method at / m 3 . In that case, as a shrinkage | contraction reduction agent dilution density | concentration, it is 0.5-8 mass% normally, More preferably, it is 1-5 mass%.
Generally, raw concrete factories store aggregates in silos and stock yards in a wet state. Aggregates with a high water absorption rate are prewetched with water before producing concrete, so that they remain moist. ing. In the present invention, instead of pre-wetting only with general water using these facilities, a shrinkage reducing agent aqueous solution may be pre-wetched on the high water-absorption regenerated aggregate in advance.
再生骨材に収縮低減剤水溶液をプレウェッチングした本発明のコンクリート用骨材は、コンクリートの製造に際して、骨材として他の細骨材、粗骨材と混合使用できる。混合比率は、要求されるコンクリートの性能によって決定される。 The aggregate for concrete of the present invention in which the shrinkage reducing agent aqueous solution is pre-wetched on the recycled aggregate can be used in combination with other fine aggregates and coarse aggregates as aggregates in the production of concrete. The mixing ratio is determined by the required concrete performance.
本発明において、セメントとしては、普通・早強・中庸熱・低熱ポルトランドセメント等の各種ポルトランドセメント、高炉セメント、フライアッシュセメント等の各種混合セメント等が使用できる。 In the present invention, as the cement, various portland cements such as normal / early strong / medium heat / low heat Portland cement, various mixed cements such as blast furnace cement and fly ash cement can be used.
なお、本発明においては、必要に応じて、コンクリート製造時にＡＥ剤、消泡剤、膨張材など、一般的に使用されているコンクリート混和剤を併用添加することができる。 In addition, in this invention, the concrete admixture generally used, such as AE agent, an antifoamer, and an expander, can be used together as needed at the time of concrete manufacture.
細骨材および粗骨材として、解体したコンクリート塊を破砕、粒度調整して製造された再生細骨材及び再生粗骨材、普通細骨材として山砂、砕砂、普通粗骨材として砕石（大）、砕石（小）を準備した。これらの密度、吸水率、粒度を表１に示す。
また、セメントとして、普通ポルトランドセメント〔住友大阪セメント（株）製、密度３．１５ｇ／ｃｍ3〕、主成分がリグニンスルフォン酸化合物とポリオールの複合体であるＡＥ減水剤〔（株）エヌエムビー製、商品名：ポゾリスＮo．７０〕、低級アルコールアルキレンオキシド付加物である収縮低減剤〔住友大阪セメント（株）製、商品名：テスタＦ〕を準備した。
Recycled fine aggregates and recycled coarse aggregates produced by crushing and breaking down the crushed concrete mass as fine aggregates and coarse aggregates, mountain sand, crushed sand as normal fine aggregates, and crushed stones as normal coarse aggregates ( Large) and crushed stone (small) were prepared. These density, water absorption, and particle size are shown in Table 1.
Further, as a cement, ordinary Portland cement (manufactured by Sumitomo Osaka Cement Co., Ltd., density 3.15 g / cm 3 ), an AE water reducing agent whose main component is a complex of a lignin sulfonic acid compound and a polyol (manufactured by NMB Co., Ltd., Product name: Pozoris No. 70], a shrinkage reducing agent [trade name: Tester F, manufactured by Sumitomo Osaka Cement Co., Ltd.] which is an adduct of lower alcohol alkylene oxide was prepared.
各種試験は、以下に記載の方法で行った。
・空気量試験：ＪＩＳ Ａ １１２８「フレッシュコンクリートの空気量の圧力による試験方法」に準拠した。
・圧縮強度試験：ＪＩＳ Ａ １１０８「コンクリートの圧縮強度試験方法」に準拠した。
・乾燥収縮試験の長さ変化試験：ＪＩＳ Ａ １１２９−２「モルタル及びコンクリートの長さ変化試験方法」に準拠した。
Various tests were conducted by the methods described below.
-Air quantity test: Conforms to JIS A 1128 "Test method by pressure of air quantity of fresh concrete".
Compressive strength test: Conforms to JIS A 1108 “Concrete compressive strength test method”.
-Length change test of drying shrinkage test: Conforms to JIS A 1129-2 “Test method for length change of mortar and concrete”.
実施例１、２及び比較例１、２
表２、表３で示すように実施例１、２では、粒度５ｍｍ以下で吸水率が１５．２％の再生細骨材に、それぞれ１質量％濃度、３質量％濃度の収縮低減剤水溶液を溶液散布（プレウェッチング）することで得た、表面乾燥飽水状態の再生細骨材を６６０ｋｇ用いた。
一方、収縮低減剤無添加で、水をプレウェッチングして得た表面乾燥飽水状態の再生細骨材を６６０ｋｇ用いた場合を比較例１とし、水をプレウェッチングして得た表面乾燥飽水状態の再生細骨材を６６０ｋｇ用い、コンクリート製造時にセメントの質量を基準にその１質量％の収縮低減剤を練混ぜ水に加えて使用した場合（一般添加法）を比較例２とした。
Examples 1 and 2 and Comparative Examples 1 and 2
As shown in Tables 2 and 3, in Examples 1 and 2, a shrinkage reducing agent aqueous solution having a concentration of 1% by mass and a concentration of 3% by mass was respectively added to recycled fine aggregate having a particle size of 5 mm or less and a water absorption of 15.2%. 660 kg of regenerated fine aggregate in a surface-saturated, saturated state obtained by spraying the solution (pre-wetting) was used.
On the other hand, the case of using 660 kg of dry fine aggregate in a surface-dried saturated state obtained by pre-wetting water without adding a shrinkage reducing agent was used as Comparative Example 1, and the surface was obtained by pre-wetting water. Comparative Example 2 is a case where 660 kg of regenerated fine aggregate in a saturated state is used, and 1% by mass of the shrinkage reducing agent is added to the kneaded water based on the mass of the cement during the concrete production (general addition method). .
上記のようにプレウェッチングした再生細骨材及びその他の骨材及びセメント、収縮低減剤、ＡＥ剤を用い、水セメント比を５０％、骨材の細骨材率（ｓ／ａ：％）〔細骨材／（細骨材+粗骨材）；容積比〕を４５％として、表３に示すような配合でコンクリートミキサによりコンクリートを製造し、供試体を作製した。 Recycled fine aggregate and other aggregates and cement, shrinkage reducing agent and AE agent prewetched as described above, water cement ratio 50%, fine aggregate ratio of aggregate (s / a:%) [Fine aggregate / (fine aggregate + coarse aggregate); volume ratio] was set to 45%, and concrete was produced by a concrete mixer with the composition shown in Table 3 to prepare a specimen.
実施例３〜５及び比較例３、４
表４、表５に示すように、実施例３〜５では、粒度５〜２０ｍｍで吸水率が６．２％の再生粗骨材にそれぞれ１質量％濃度、３質量％濃度及び５質量％濃度の収縮低減剤水溶液を溶液散布（プレウェッチング）して得た、表面乾燥飽水状態の再生粗骨材を８８６ｋｇ用いた。
一方、収縮低減剤無添加で、水をプレウェッチングして得た表面乾燥飽水状態の再生粗骨材を８８６ｋｇ用いた場合を比較例３とし、水をプレウェッチングして得た表面乾燥飽水状態の再生粗骨材を８８６ｋｇ用い、コンクリート製造時にセメントの質量を基準にその１質量％の収縮低減剤を練混ぜ水に加えて使用した場合（一般添加法）を比較例４とした。
Examples 3 to 5 and Comparative Examples 3 and 4
As shown in Tables 4 and 5, in Examples 3 to 5, the recycled coarse aggregate having a particle size of 5 to 20 mm and a water absorption rate of 6.2% was 1%, 3% and 5% by weight, respectively. 886 kg of recycled coarse aggregate with a dry surface and saturated water obtained by spraying (pre-wetting) an aqueous solution of a shrinkage reducing agent was used.
On the other hand, the surface dryness obtained by prewetting water was set as Comparative Example 3 using 886 kg of recycled coarse aggregate in the surface dry saturated state obtained by prewetting water without adding a shrinkage reducing agent. Comparative Example 4 is a case where 886 kg of recycled aggregate in a saturated state is used, and 1% by mass of the shrinkage reducing agent is added to the kneaded water based on the mass of the cement when the concrete is produced (general addition method). .
上記のようにプレウェッチングした再生粗骨材を用い、表５に示すような配合でコンクリートミキサによりコンクリートを製造し、供試体を作製した。 Using the recycled coarse aggregate pre-wetted as described above, concrete was produced by a concrete mixer with a composition as shown in Table 5 to prepare a specimen.
比較例５〜１２
表６、表７に示すように、普通骨材を用い、収縮低減剤無添加の場合を比較例５とし、コンクリート製造時にセメントの質量を基準にその１質量％の収縮低減剤を練混ぜ水に加えて使用する場合（一般添加法）を比較例６とした。また、比較例７〜９では、普通細骨材としての山砂及び砕砂に３質量％濃度、５質量％濃度及び１０質量％濃度の収縮低減剤水溶液で表面乾燥飽水状態にした骨材を使用し、同様に、比較例１０〜１２では、普通粗骨材（大）及び普通粗骨材（小）にそれぞれ３質量％濃度、５質量％濃度及び１０質量％濃度の収縮低減剤水溶液で表面乾燥飽水状態にした骨材を使用した。
Comparative Examples 5-12
As shown in Table 6 and Table 7, the case where ordinary aggregate is used and no shrinkage reducing agent is added is referred to as Comparative Example 5, and 1% by weight of the shrinkage reducing agent is mixed with water based on the mass of cement during the production of concrete. When used in addition to (general addition method), it was designated as Comparative Example 6. Moreover, in Comparative Examples 7-9, the aggregate which made the surface dry saturated state by the 3 mass% density | concentration, the 5 mass% density | concentration, and the 10 mass% density | concentration reducing agent aqueous solution to the mountain sand and crushed sand as a fine fine aggregate. Similarly, in Comparative Examples 10 to 12, the ordinary coarse aggregate (large) and the ordinary coarse aggregate (small) were respectively used with an aqueous shrinkage reducing agent solution having a concentration of 3% by mass, 5% by mass and 10% by mass. Aggregates that had been dry and saturated with water were used.
上記の実施例１〜５及び比較例１〜１２について、収縮低減剤使用量（ｋｇ／ｍ3）、得られたコンクリート供試体の材齢９１日後の乾燥収縮ひずみ及び収縮低減率を表８〜１１に示す。 About said Examples 1-5 and Comparative Examples 1-12, the shrinkage | contraction reducing agent usage-amount (kg / m < 3 >), the drying shrinkage strain and shrinkage | reduction reduction rate after 91 days of age of the obtained concrete test body are shown in Table 8- 11 shows.
表８より、実施例１及び２の再生細骨材に収縮低減剤水溶液を散布する本発明の方法では、材齢９１日での乾燥収縮ひずみが、無添加で９９１×１０-6、セメントの質量を基準に練混ぜ水に配合する一般添加法である比較例２では８２８×１０-6であるのと比較して、実施例１では８４１×１０-6、実施例２では７７７×１０-6であり、少ない収縮低減剤の使用量で、同等に近い又は同等以上の収縮低減率を得ることができる。
同様に、表９に示す再生粗骨材に溶液散布した実施例３〜５は一般添加法である比較例４との比較においても、同様に少ない収縮低減剤の使用量で、同等に近い又は同等以上の収縮低減率を得ることができる。
一方、表１０に示すように、吸水率が１．３７％の普通細骨材に溶液散布した場合は、濃度を１０％（比較例９）まで上げても、十分な収縮低減効果は得られず、同等の収縮低減剤の使用量である実施例１との収縮低減率の比較からもわかるように、再生骨材に使用した場合のような効果は得られなかった。
また、表１１に示すように、吸水率が０．５４の普通粗骨材に溶液散布した場合は、濃度を１０％（比較例１２）まで上げても、十分な収縮低減効果は得られず、同等の収縮低減剤の使用量である比較例８と同等の低い収縮低減率の値であり、再生骨材に使用した場合のような効果は得られなかった。
以上より、本発明の溶液散布による方法は、高吸水率再生骨材に限り一般添加法よりも少ない収縮低減剤使用量で同等又は同等以上の乾燥収縮低減効果が得られるのでコストの削減ができる。
From Table 8, in the method of the present invention in which the regenerated fine aggregates of Examples 1 and 2 were sprayed with the shrinkage reducing agent aqueous solution, the dry shrinkage strain at the age of 91 days was 991 × 10 −6 without addition, mass compared as to the general addition method 828 × 10 -6 Comparative example 2 is formulated into mixing water based on example 1, 841 × 10 -6, example 2, 777 × 10 - 6. With a small amount of shrinkage reducing agent used, a shrinkage reduction rate close to or equal to or equivalent can be obtained.
Similarly, in Examples 3 to 5 where the solution was sprayed on the recycled coarse aggregate shown in Table 9, even in comparison with Comparative Example 4 which is a general addition method, the amount of shrinkage-reducing agent used is similarly small, A shrinkage reduction rate equal to or higher than that can be obtained.
On the other hand, as shown in Table 10, when the solution is sprayed on ordinary fine aggregate having a water absorption rate of 1.37%, even if the concentration is increased to 10% (Comparative Example 9), a sufficient shrinkage reduction effect is obtained. In addition, as can be seen from the comparison of the shrinkage reduction rate with Example 1, which is the amount of the same shrinkage reducing agent used, the effect as in the case of using the recycled aggregate was not obtained.
In addition, as shown in Table 11, when the solution was sprayed on ordinary coarse aggregate having a water absorption rate of 0.54, even if the concentration was increased to 10% (Comparative Example 12), a sufficient shrinkage reduction effect could not be obtained. The value of the shrinkage reduction rate is the same as that of Comparative Example 8, which is the use amount of the equivalent shrinkage reducing agent, and the effect as in the case of using the recycled aggregate was not obtained.
As described above, the solution spraying method of the present invention can reduce the cost because the drying shrinkage reduction effect is equal to or equal to or higher than that of the general addition method only for the high water absorption regenerated aggregate with the amount of shrinkage reducing agent used. .
次に、再生粗骨材を使用した実施例３〜５、比較例３、４について、フレッシュコンクリートにおける空気量及び、材齢２８日の圧縮強度試験を行った。これらの結果を表１２に示す。 Next, for Examples 3 to 5 and Comparative Examples 3 and 4 using recycled coarse aggregate, an air amount in fresh concrete and a compressive strength test on the age of 28 days were performed. These results are shown in Table 12.
表１２より一般添加法（比較例４）では、空気量が７．３％と増大しているが、溶液散布法の実施例３〜５では空気量が４．５±１．５％のＪＩＳ Ａ ５３０８(レディーミクストコンクリート)の規格内に収まっており、コンクリートの空気量に対する悪影響が解消された。
さらに、一般添加法（比較例４）では、収縮低減剤無添加のものと比較して圧縮強度が低下するが、溶液散布法の実施例３〜５では収縮低減剤無添加と比べても強度に差が生じておらず、一般添加法において問題であった強度低下に対する悪影響も解消された。
From Table 12, in the general addition method (Comparative Example 4), the air amount increased to 7.3%, but in Examples 3 to 5 of the solution spraying method, the air amount was 4.5 ± 1.5%. A 5308 (ready-mixed concrete) is within the specification, and the adverse effect on the air volume of concrete has been eliminated.
Further, in the general addition method (Comparative Example 4), the compressive strength is lower than that in the case where no shrinkage reducing agent is added, but in Examples 3 to 5 of the solution spraying method, the strength is higher than that in the case where no shrinkage reducing agent is added. Thus, the adverse effect on strength reduction, which was a problem in the general addition method, was also eliminated.
本発明のコンクリートの乾燥収縮低減方法は、吸水率３％以上の再生骨材に、収縮低減剤水溶液をプレウェッチングし、これをコンクリートに使用する方法であり、一般添加法のように、練混ぜ水に直接収縮低減剤を添加混合しないので、収縮低減剤が空気連行性や消泡性を有する場合の強度低下や凍結融解抵抗性の低下の危惧がなく、少量の収縮低減剤で高い効果が得られる極めて効率的かつ経済的な方法であり、解体したコンクリートによる再生骨材を骨材として再利用できる極めて有用な方法である。
本発明のコンクリート用骨材は、吸水率３％以上の再生骨材に、収縮低減剤水溶液をプレウェッチングしているので、乾燥収縮低減が要求されるコンクリートに利用できる。
本発明のコンクリートは、収縮低減剤水溶液をプレウェッチングした再生骨材を含有しているので、収縮低減剤による空気連行性や消泡性を有する場合の強度低下や凍結融解抵抗性の低下の危惧のない極めて効率的、経済的なコンクリートとして利用できる。
The method for reducing dry shrinkage of concrete according to the present invention is a method of prewetting a shrinkage reducing agent aqueous solution on recycled aggregate having a water absorption rate of 3% or more, and using this in concrete. Since no shrinkage reducing agent is added directly to the water mixture, there is no risk of a decrease in strength or freezing and thawing resistance when the shrinkage reducing agent has air entrainment and defoaming properties. A small amount of shrinkage reducing agent is highly effective. This is an extremely efficient and economical method that can be obtained, and is a very useful method that can recycle recycled aggregates from demolished concrete as aggregates.
Since the aggregate for concrete of the present invention is prewetched with a shrinkage reducing agent aqueous solution on recycled aggregate having a water absorption rate of 3% or more, it can be used for concrete that requires a reduction in drying shrinkage.
Since the concrete of the present invention contains recycled aggregate pre-wetched with a shrinkage reducing agent aqueous solution, the strength reduction and freezing and thawing resistance reduction when the shrinkage reducing agent has air entrainment property and defoaming property are reduced. It can be used as extremely efficient and economical concrete without fear.
Claims (3)
収縮低減剤添加量＝再生骨材表乾質量×再生骨材の吸水率×
収縮低減剤希釈濃度 （Ｉ）
（但し、収縮低減剤希釈濃度は０．５〜５質量％） A method for reducing dry shrinkage of concrete by pre-wetting a shrinkage reducing agent aqueous solution comprising an alkylene oxide adduct of a lower alcohol to a recycled aggregate having a water absorption of 3% or more, wherein the surface dry mass of the recycled aggregate, the regeneration Based on the water absorption rate of the aggregate and the dilution concentration of the shrinkage reducing agent in the aqueous solution of the shrinkage reducing agent, pre-wetting is carried out by spraying the solution so that the amount of shrinkage reducing agent calculated by the following formula (I) is included in the recycled aggregate. A method for reducing drying shrinkage of concrete, characterized in that recycled aggregate in a dry and saturated state obtained by ching is used for concrete.
Shrinkage reducing agent addition amount = reclaimed aggregate surface dry mass x reclaimed aggregate water absorption x
Shrinkage reducing agent dilution concentration (I)
(However, the shrinkage reducing agent dilution concentration is 0.5 to 5% by mass)
該再生骨材の表乾質量、該再生骨材の吸水率、及び該収縮低減剤水溶液における収縮低減剤の希釈濃度に基づいて次式（Ｉ）で算出される収縮低減剤添加量が再生骨材に含まれるように溶液散布によりプレウェッチングして得た表面乾燥飽水状態の再生骨材としてなるコンクリート用骨材。
収縮低減剤添加量＝再生骨材表乾質量×再生骨材の吸水率×
収縮低減剤希釈濃度 （Ｉ）
（但し、収縮低減剤希釈濃度は０．５〜５質量％） A concrete aggregate obtained by pre-wetting a shrinkage reducing agent aqueous solution comprising an alkylene oxide adduct of a lower alcohol on a recycled aggregate having a water absorption rate of 3% or more,
Based on the surface dry mass of the regenerated aggregate, the water absorption rate of the regenerated aggregate, and the dilution concentration of the shrinkage reducing agent in the shrinkage reducing agent aqueous solution, the shrinkage reducing agent addition amount calculated by the following formula (I) is aggregate for concrete comprising a recycled aggregate surface dry water-saturated state obtained by prewetting quenching with a solution spray to be included in the wood.
Shrinkage reducing agent addition amount = reclaimed aggregate surface dry mass x reclaimed aggregate water absorption x
Shrinkage reducing agent dilution concentration (I)
(However, the shrinkage reducing agent dilution concentration is 0.5 to 5% by mass)
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