JP3854936B2 - Concrete admixture, mortar admixture and mixed cement - Google Patents

Description

【００８３】
実施例４〜６及び比較例１の結果の分析
上記実施例で得られた割裂引張強度の経時変化を図５に、圧縮強度の経時変化を図６にそれぞれまとめて示す。実施例４（混和剤Ａ添加）では、比較例１（ベースコンクリート）に比べて、材令７日目で６０％近く、材令２８日及び９１日で４０％近くも引張強度が向上した。これに対し、圧縮強度の向上は１０〜２０％程度に留まっていた。また、混和剤Ａよりも粒子寸法が大きい混和剤Ｂを添加した実施例５では実施例４よりも引張強度の向上が小さかった。コンクリート混和剤の添加量が実施例４及び５に比べて倍量であった実施例６でも、強度の向上効果が小さかった。
【００８４】
実施例４（混和剤Ａ添加）と比較例１（ベースコンクリート）で得られた、材令７日、２８日、９１日のそれぞれの強度データについて、圧縮強度を横軸に、割裂引張強度を縦軸にプロットした結果を図７に示す。
その結果、実施例４で得られた強度データは、式（３）において、αを０．３１とした曲線に近似し、比較例１で得られた強度データは、αを０．２３とした曲線に近似した。
すなわち、混和剤Ａを添加した実施例４では、ベースコンクリートに比べてα値が約３５％向上しており、同一圧縮強度から想定される引張強度が３５％も向上していることがわかった。このように、本発明のコンクリートは、圧縮強度の向上に比べて引張強度の向上が顕著である点で、際立った特徴を示している。
【００８５】
実施例４（混和剤Ａ添加）、実施例５（混和剤Ｂ添加）及び比較例１（ベースコンクリート）において、材令２８日の試料の圧縮側弾性係数を測定したが、いずれの試料においても約０．００２の歪で最大圧縮応力を示し、その応力値にも大きな差は認められなかった。すなわち、本発明の混和剤を添加することによって若干圧縮側弾性係数が大きくなっているものの、圧縮挙動に大きな変化は認められなかった。
【００８６】
また、実施例４（混和剤Ａ添加）及び比較例１（ベースコンクリート）で得られたコンクリートについて、ポロシメータによって細孔分布測定を行った結果を図１及び図２にそれぞれ示す。本発明の混和剤を添加することによって、０．５〜１０μｍ程度の細孔が減少し、０．０１〜０．１μｍ程度の細孔が増加する傾向が認められた。
【００８７】
また、実施例４（混和剤Ａ添加）及び比較例１（ベースコンクリート）で得られたコンクリートの引張試験における破断面の写真を図３及び図４にそれぞれ示す。図４から明らかなようにベースコンクリートでは、粗骨材とモルタルとの界面で破断している部分が多く、遷移帯が脆弱点であることを示している。これに対し、図３に示されるように、本発明の混和剤を添加した場合には粗骨材が破断している部分が多く、遷移帯部分での接着強度が大きく改善されていることが示唆されるものである。
【００８８】
実施例７（混和剤Ｃ添加コンクリートの製造・評価）
ベースコンクリートとして使用したレディーミクストコンクリートは以下の原料を使用したものである。
１）セメント
太平洋セメント（株）製普通ポルトランドセメント、密度３．１６ｇ／ｃｍ^３、ナトリウム含有量（Na₂O換算値）０．５８重量％。
２）粗骨材１
八王子産砕石５号、粒の大きさ５〜２０ｍｍ、粗粒率７．０４、表面乾燥時密度２．６７ｇ／ｃｍ^３、吸水率０．５５重量％。
３）粗骨材２
八王子産砕石６号、粒の大きさ２．５〜１０ｍｍ、粗粒率５．８８、表面乾燥時密度２．６７ｇ／ｃｍ^３、吸水率０．６９重量％。
４）細骨材
君津産山砂、粒の大きさ５ｍｍ以下、粗粒率２．６４、表面乾燥時の密度２．６０ｇ／ｃｍ^３、吸水率２．２３重量％。
【００８９】
上記各成分の配合比は以下のとおりである。括弧内の数値は、セメント１００重量部に対する配合量比である。本ベースコンクリートのスランプ値は８ｃｍである。
セメント ３２０．０ｋｇ／ｍ^３（１００重量部）
水 １７６．０ｋｇ／ｍ^３（ ５５重量部）
粗骨材１ ５６４．３ｋｇ／ｍ^３（１７６重量部）
粗骨材２ ３７６．２ｋｇ／ｍ^３（１１８重量部）
細骨材 ８４２．２ｋｇ／ｍ^３（２６３重量部）
【００９０】
前記ベースコンクリートに、実施例２で得られた混和剤Ｃを、セメント１００重量部に対して２重量部となるように添加した以外は実施例４と同様にして、コンクリート試料を作製した。これを複数本用意し、１５℃の空気中で養生した。本実施例７と、以下に説明する比較例３については、同一ロットのベースコンクリートを用いて、同日にサンプルを作製し、同じ環境の下で養生したものである。材令７日及び２８日の試料を実施例４と同様の強度測定試験に供した。得られた引張強度、圧縮強度及びα値を表２にまとめて示す。
【００９１】
比較例３（混和剤無添加コンクリートの製造・評価）
実施例７において、混和剤Ｃを使用せず、ベースコンクリートのみを型枠に流し込んで、コンクリート試料とし、以降は実施例７と同様にして養生した。材令７日及び２８日の試料を実施例４と同様の強度測定試験に供した。得られた引張強度、圧縮強度及びα値を表２にまとめて示す。
【００９２】
【表２】

【００９３】
表２から明らかなように、混和剤Ｃを添加した実施例７のコンクリートでは、混和剤を添加しなかった比較例３のコンクリートと比べて引張強度が明確に向上していた。一方、実施例７のコンクリートの圧縮強度は比較例３のコンクリートと比べて若干低下していた。すなわち、圧縮強度に比べて引張強度のみが選択的に向上しており、この点は、α値の増加によっても示されている。この試験結果は、混和剤の原料のカルボン酸としてフマル酸を使用した実施例４〜６の結果と同様であり、カルボン酸としてクエン酸を使用しても本発明の効果が得られることがわかった。
【００９４】
実施例８（混和剤Ｄ添加コンクリートの製造・評価）
ベースコンクリートとして使用したレディーミクストコンクリートは実施例７と同じ仕様のものである。当該ベースコンクリートに、実施例３で得られた混和剤Ｄを、セメント１００重量部に対して１重量部となるように添加した以外は実施例４と同様にして、コンクリート試料を作製した。これを複数本用意し、２０℃の空気中で養生した。本実施例８と、以下に説明する比較例４については、同一ロットのベースコンクリートを用いて、同日にサンプルを作製し、同じ環境の下で養生したものである。材令７日及び２８日の試料を実施例４と同様の強度測定試験に供した。得られた引張強度、圧縮強度及びα値を表３にまとめて示す。
【００９５】
比較例４（混和剤無添加コンクリートの製造・評価）
実施例８において、混和剤Ｄを使用せず、ベースコンクリートのみを型枠に流し込んで、コンクリート試料とし、以降は実施例８と同様にして養生した。材令７日及び２８日の試料を実施例４と同様の強度測定試験に供した。得られた引張強度、圧縮強度及びα値を表３にまとめて示す。
【００９６】
【表３】

【００９７】
表３から明らかなように、混和剤Ｄを添加した実施例８のコンクリートでは、混和剤を添加しなかった比較例４のコンクリートと比べて引張強度が向上していた。実施例８での混和剤の配合量はセメント１００重量部に対して１重量部と少量ではあるが、それでも明らかに引張強度が向上していた。一方、実施例８のコンクリートの圧縮強度は比較例４のコンクリートと比べて若干低下していた。すなわち、この場合においても圧縮強度に比べて引張強度のみが選択的に向上しており、この点は、α値の増加によっても示されている。このことにより、混和剤として含水率の低いものを使用しても、また少量の添加でも引張強度が向上することがわかった。
【００９８】
実施例９（混和剤Ａ添加モルタルの製造・評価）
本実施例では以下の原料を使用した。
１）セメント
太平洋セメント（株）製普通ポルトランドセメント、密度３．１６ｇ／ｃｍ^３、ナトリウム含有量（Na₂O換算値）０．５８重量％。
２）細骨材
君津産山砂、粒の大きさ５ｍｍ以下、粗粒率２．６４、表面乾燥時の密度２．６０ｇ／ｃｍ^３、吸水率２．２３重量％。
【００９９】
上記のセメント、細骨材及び水を、まず強制練りミキサーで１分間撹拌した後、実施例１で得られた混和剤Ａを後添加して、さらに３０秒間撹拌した。配合比は以下のとおりである。括弧内の数値は、セメント１００重量部に対する配合量比である。
セメント ３２０．０ｋｇ／ｍ^３（１００重量部）
水 １７６．０ｋｇ／ｍ^３（ ５５重量部）
細骨材 ８４２．２ｋｇ／ｍ^３（２６３重量部）
混和剤Ａ ６．４ｋｇ／ｍ^３（ ２重量部）
【０１００】
撹拌した後に、直径５０ｍｍ、高さ１００ｍｍの円柱状の型枠に流し込んで、モルタル試料とした。この試料形態はＪＳＣＥ−Ｆ５０６−１９９９に準拠するものである。これを複数本用意し、２０℃の空気中で養生した。本実施例９と、以下に説明する比較例５については、同日にサンプルを作製し、同じ環境の下で養生したものである。材令７日及び２８日の試料を実施例４と同様の強度測定試験に供した。得られた引張強度、圧縮強度及びα値を表４にまとめて示す。
【０１０１】
比較例５（混和剤無添加モルタルの製造・評価）
実施例９において、混和剤Ａを使用せず、セメント、水及び細骨材のみを配合する以外は実施例９と同様にして、モルタル試料を作製し、実施例９と同様にして養生した。材令７日及び２８日の試料を実施例４と同様の強度測定試験に供した。得られた引張強度、圧縮強度及びα値を表４にまとめて示す。
【０１０２】
【表４】

【０１０３】
表４から明らかなように、セメント１００重量部に対して混和剤Ａを２重量部添加した実施例９のモルタルでは、混和剤を添加しなかった比較例５のモルタルに比べて引張強度が向上していた。その向上の程度はセメント１００重量部に対して混和剤Ａを２．５重量部添加した実施例４のコンクリートでの向上の程度に比べれば小さく、本発明の混和剤の添加による引張強度向上の効果は、モルタルよりもコンクリートの方が大きい。しかしながら、モルタルにおいても明らかに引張強度が向上しており、粗骨材の表面での接着強度の向上ほどではないものの、細骨材の表面においても接着強度が向上しているようである。一方、実施例９のモルタルの圧縮強度は比較例４のモルタルに比べて若干低下していた。モルタルの場合においても、コンクリートの場合と同様に圧縮強度に比べて引張強度のみが選択的に向上しており、この点は、α値の増加によっても示されている。すなわち、本発明の混和剤は、モルタルに添加しても、その引張強度を向上させることができるものである。
【０１０４】
【発明の効果】
以上説明したように、本発明のコンクリート混和剤を添加したコンクリートは、圧縮強度に比較して引張強度が大きく向上しており、コンクリート構造体におけるひび割れの低減や、使用鋼材量の低減を可能にできるものである。このコンクリート混和剤は、流動状態のコンクリートに添加するだけでよく、しかもコンクリートの流動性も維持できる。これによって、大型化、多様化している各種のコンクリート構造物に対して好適に使用されるコンクリートを提供することができる。また、各種のコンクリート製品に対しても好適に使用されるコンクリートを提供することができる。
【０１０５】
また、本発明のモルタル混和剤を添加したモルタルもまた、圧縮強度に比較して引張強度が大きく向上しており、外力や温度応力などによる引張応力を受けやすい製品や、疲労の影響を受けやすい製品に好適に使用される。また、複雑な形状の製品や肉薄の製品などにも有用であり、多様なモルタル製品を提供できる。さらにまた、本発明の混合セメントは、引張強度に優れたコンクリートやモルタルを製造するのに有用である。
【図面の簡単な説明】
【図１】実施例４のコンクリートの細孔分布を示した図である。
【図２】比較例１のコンクリートの細孔分布を示した図である。
【図３】実施例４のコンクリートの破断面の写真である。
【図４】比較例１のコンクリートの破断面の写真である。
【図５】割裂引張強度の経時変化を示したグラフである。
【図６】圧縮強度の経時変化を示したグラフである。
【図７】圧縮強度と割裂引張強度の関係を示したグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a concrete admixture added to concrete. Specifically, the present invention relates to a concrete admixture obtained by mixing a silicate and an acid in the presence of water and then solidifying the mixture, and a method for producing the same. The present invention also relates to concrete using the concrete admixture. Furthermore, it is related with the construction method of the concrete structure using the said concrete admixture, and the manufacturing method of a concrete product.
[0002]
Moreover, this invention relates to the mortar admixture added to mortar and its manufacturing method. Moreover, it is related with the manufacturing method of the mortar and mortar product which use the said mortar admixture. The invention further relates to a mixed cement.
[0003]
[Prior art]
Concrete has been widely used in the construction field for a long time because it has high compressive strength, is easy to shape, and is inexpensive. In recent years, especially because structures have become larger and diversified, many studies have been made to further increase the compressive strength of concrete. A method of adding various admixtures has been reported as one of the methods for increasing the strength of concrete. This is the same for mortar as well as concrete.
[0004]
Japanese Patent Application Laid-Open No. 61-155237 (Patent Document 1) discloses a method for producing dam concrete characterized by containing an organic acid and a quick setting inorganic salt. It is stated that the strength can be increased without increasing the calorific value by containing organic acids and quick setting inorganic salt, and it is described that it is suitable for the application of large quantities of concrete such as dam concrete. Has been. Examples of the organic acids used here include various carboxylic acids such as citric acid and fumaric acid, and examples of the quick setting inorganic salt include alkali metal salts such as sodium carbonate and sodium silicate. Has been. In the example of the publication, it has been confirmed that the compression strength is specifically improved.
[0005]
Japanese Patent Application Laid-Open No. 2001-294461 (Patent Document 2) describes a concrete modifier obtained by blending water glass with a polyvalent carboxylic acid or a derivative thereof. The concrete modifier is applied to the hardened concrete surface in a solution state. By doing so, it is described that deterioration due to the neutralization or cracking of concrete can be prevented or suppressed.
[0006]
[Patent Document 1]
JP-A-61-155237 (pages 1 to 3, Table 3)
[Patent Document 2]
JP 2001-294461 A (pages 2 to 3)
[0007]
[Problems to be solved by the invention]
The greatest feature of the mechanical properties of concrete is that it has a high compressive strength and a low tensile strength, shear strength and bending strength. Normally, even if the compressive strength of concrete can be increased, it is difficult to increase the tensile strength because of its so-called peak. Therefore, at the site where a concrete structure is constructed, the occurrence of cracks due to insufficient tensile strength is a serious problem.
[0008]
Since the tensile strength of concrete is smaller than the compressive strength, to ensure safety, the tensile strength of the concrete is ignored and a strength design is performed by using a reinforcing material that resists the tensile force. Such reinforcing materials include reinforcing steel and steel for PC (prestressed concrete), and the current situation is that the proof strength is secured as a whole structure using these. However, as described above, since the structures are becoming larger and diversified, it is inevitable that the amount of steel used to secure the proof stress of the concrete structure will increase, resulting in overcrowding. In this case, when concrete in a fluidized state is placed in the mold, the concrete is not sufficiently wrapped around, or the bar arrangement work itself becomes complicated and causes an increase in cost.
[0009]
The concrete that has generated heat due to the hydration reaction after placement and has risen in temperature shrinks during cooling. If both ends of the concrete are constrained at the time of shrinkage, tensile stress will be generated, often inducing cracks. Therefore, it is important to increase the tensile strength of concrete even at a relatively short age when the hydration reaction is in progress. Moreover, although the concrete immediately after placement is in a wet state, when it is exposed to the outside air, it shrinks due to drying. In order to cope with shrinkage such as long-term drying, it is important to increase the tensile strength of concrete.
[0010]
In order to improve the tensile strength of concrete, there is a known method of blending short fiber reinforcements made of inorganic fibers and synthetic fibers such as asbestos and glass fibers. Since the dispersibility of the material is insufficient and may cause lumps, and it causes a cost increase, it is only used for limited purposes.
[0011]
In the method described in JP-A-61-155237, the strength is increased by adding an admixture to concrete, but only the compressive strength is improved, and the tensile strength is related. There is no description. Further, the method described in JP-A No. 2001-294461 is a method of applying a modifier to the concrete surface after curing, and can prevent the progress of concrete deterioration such as cracks, but positively increases the tensile strength. It is not intended to raise.
[0012]
This invention is made | formed in order to solve the said subject, and provides the admixture which can improve tensile strength by adding to concrete, and its manufacturing method. In addition, the present invention further provides concrete using the concrete admixture, a method for constructing a concrete structure, and a method for producing a concrete product.
[0013]
Moreover, each subject in the above-mentioned concrete exists as a subject similarly in mortar. The present invention has been made to solve such a problem, and provides an admixture that can improve tensile strength when added to a mortar and a method for producing the same. In addition, a method for producing a mortar and a mortar product using the mortar admixture is provided. Furthermore, this invention provides the mixed cement used suitably for such concrete and mortar.
[0014]
[Means for Solving the Problems]
  The above issues are related to alkali metal silicates, At least one selected from the group consisting of oxycarboxylic acids and polyvalent carboxylic acidsIt contains a reaction product with a carboxylic acid, the ratio [metal / carboxyl group] of the number of metal atoms in the silicate to the number of carboxyl groups in the carboxylic acid is 2 to 200, and the water content is 50 Concrete admixture consisting of a powder or granular material that is 50% by weight or more and 50% by weight or more of particles that do not pass through a 1.25 mm mesh and that passes through a 2.5 mm mesh. Solved by providing. At this time,SaidWith silicateSaidA concrete admixture composed of a powdery or granular material obtained by mixing a carboxylic acid in the presence of water and then solidifying is preferred. The reason why the tensile strength of the concrete after curing is increased by adding such an admixture is not necessarily clear, but a mechanism described below is conceivable.
[0015]
The mechanism of the hydration reaction of cement is complicated and is not completely clarified at present, but a typical chemical model of the hydration reaction is represented by, for example, the following formula (1). In addition, the numerical value currently used in Formula (1) is an illustration, Comprising: It should be taken as a numerical value with a width | variety in an actual reaction. Further, compounds not described here also contribute to the hydration reaction.
2 (2CaO ・ SiO₂) + 4H₂O → 3CaO ・ 2SiO₂・ 3H₂O + Ca (OH)₂    (1)
[0016]
Thus, as a result of the hydration reaction, calcium silicate hydrate [xCaO · SiO₂・ YH₂O] (usually x is a value in the range of 1.5 to 2.0, and y is in a slightly wider range) and calcium hydroxide [Ca (OH)₂] Is formed as the main hydration reaction product. Of these, calcium silicate hydrate is the main component that normally occupies more than half of the volume in fully cured Portland cement. The calcium silicate hydrate is in the form of a fiber or a network, and can be firmly bonded by van der Waals force. On the other hand, since calcium hydroxide is a hexagonal prism-shaped crystal having a small surface area, it has a small van der Waals force and is easily broken due to crystal orientation, and contributes little in terms of adhesive strength.
[0017]
It is said that the place where the strength is the weakest among the concrete and the crack is easily generated by the tensile stress is a so-called transition zone formed mainly at the interface between the coarse aggregate and the mortar. When placing concrete in a formwork, a transition zone is a region where a water film is formed as a result of bleeding, especially in the lower part around the aggregates and rebars of large dimensions, and the ratio of moisture to cement is large. Occurs. In this transition zone, the proportion of calcium hydroxide is larger than that in the mortar part, but this is considered to be one of the factors that lower the strength of the transition zone and thus the tensile strength of concrete. ing.
[0018]
The concrete admixture of the present invention is presumed to be useful for converting calcium hydroxide present in this transition zone into strong calcium silicate hydrate by the following reaction. The following formula (2) shows a model chemical formula of an example of calcium silicate hydrate formation in the reaction between sodium metasilicate and calcium hydroxide.
2Na₂SiO_Three+ 3Ca (OH)₂+ 2H₂O → 3CaO ・ 2SiO₂・ 3H₂O + 4NaOH (2)
In the case of the above formula (1), the actual chemical reaction in concrete is not such a quantitative reaction, and the numerical value in the above formula (2) should be regarded as having a range. It is the same.
[0019]
However, if an aqueous solution containing a mixture of silicate, acid and water is added as it is to the concrete in a fluid state, the fluidity of the concrete will be reduced during the addition, and the concrete will be placed in the mold. It becomes difficult. This is considered to be because the equation (2) proceeds too rapidly in the concrete.
[0020]
The concrete admixture of the present invention is considered to be able to advance the above formula (2) in the transition zone portion at the time of hardening after casting while maintaining the fluidity of the concrete at the time of casting. By adding the solidified silicate and acid in the presence of water, the fluidity is not hindered when added to concrete, and then the hydration reaction proceeds. It is considered that the silicate component can be supplied to the transition zone portion in order to advance the formula (2).
[0021]
In fact, what is obtained by mixing silicate and acid in the presence of water and then drying and solidifying is different from simply drying and solidifying silicate. It has been confirmed by the present inventor that the solution finally dissolves in water. Here, since silicic acids such as orthosilicic acid and metasilicic acid are very weak acids, a weak acid (silicic acid) is liberated by a reaction with a stronger acid (for example, carboxylic acid). It is considered that an acid-base reaction (neutralization reaction) that forms a salt proceeds.
[0022]
  Due to the mechanism presumed above, alkali metal silicate and, At least one selected from the group consisting of oxycarboxylic acids and polyvalent carboxylic acidsA concrete admixture containing a reaction product with a carboxylic acid solves the problems of the present invention. In the concrete admixture of the present invention, the silicate is preferably sodium silicate. The acid is, At least one selected from the group consisting of oxycarboxylic acids and polyvalent carboxylic acidsIt is a carboxylic acid, and the concrete admixture is powdery or granular. At this time,SaidWith silicateSaidIt is preferable to consist of a powdery body or a granular body formed by mixing carboxylic acid in the presence of water and then solidifying.
[0023]
  In addition, the above problem is, At least one selected from the group consisting of oxycarboxylic acids and polyvalent carboxylic acidsCarboxylic acid is mixed in an aqueous solution so that the ratio [metal / carboxyl group] of the number of metal atoms in the silicate to the number of carboxyl groups in the carboxylic acid is 2 to 200, and the mixed aqueous solution The water content is 50% by weight or less and the particles that do not pass through the 1.25 mm mesh are 50% by weight or more and the particles that pass through the 2.5mm mesh are 50% by weight or more. This can also be solved by providing a method for producing a concrete admixture to obtain a powdery or granular material.
[0024]
A preferred embodiment of the present invention is concrete comprising the concrete admixture, cement, aggregate and water. In addition, a method for constructing a concrete structure in which fluid concrete including cement, aggregate, the concrete admixture, and water is placed in a mold and cured is also a preferred embodiment. At this time, it is preferable to post-add the concrete admixture to concrete in a fluid state composed of cement, aggregate, and water and then place it in the mold. Furthermore, a method for producing a concrete product in which a fluidized concrete composed of cement, aggregate, the concrete admixture and water is placed in a mold and cured is also a preferred embodiment. Also at this time, it is preferable to post-add the concrete admixture to concrete in a fluid state composed of cement, aggregate, and water and then place it in the mold.
[0025]
  The above issues are related to alkali metal silicates, At least one selected from the group consisting of oxycarboxylic acids and polyvalent carboxylic acidsIt contains a reaction product with a carboxylic acid, the ratio [metal / carboxyl group] of the number of metal atoms in the silicate to the number of carboxyl groups in the carboxylic acid is 2 to 200, and the water content is 50 A mortar admixture consisting of a powder or granule that is 50% by weight or more and 50% by weight or more of particles that do not pass through a 1.25 mm mesh and that passes through a 2.5 mm mesh. It is also solved by providing. At this time,SaidWith silicateSaidA mortar admixture composed of a powdery or granular material obtained by mixing a carboxylic acid in the presence of water and then solidifying it is preferred. Also, with alkali metal silicate, At least one selected from the group consisting of oxycarboxylic acids and polyvalent carboxylic acidsCarboxylic acid is mixed in an aqueous solution so that the ratio [metal / carboxyl group] of the number of metal atoms in the silicate to the number of carboxyl groups in the carboxylic acid is 2 to 200, and the mixed aqueous solution The water content is 50% by weight or less and the particles that do not pass through the 1.25 mm mesh are 50% by weight or more and the particles that pass through the 2.5mm mesh are 50% by weight or more. The problem can also be solved by providing a method for producing a mortar admixture to obtain a powdery or granular material. A preferred embodiment of the present invention is a mortar composed of the mortar admixture, cement, fine aggregate and water. A method for producing a mortar product in which a mortar in a fluid state composed of cement, fine aggregate, the mortar admixture and water is formed and cured is also a preferred embodiment.
[0026]
  In addition, the above problem is, At least one selected from the group consisting of oxycarboxylic acids and polyvalent carboxylic acidsIt contains a reaction product with a carboxylic acid, the ratio [metal / carboxyl group] of the number of metal atoms in the silicate to the number of carboxyl groups in the carboxylic acid is 2 to 200, and the water content is 50 A powder or granule that is 50% by weight or more and 50% by weight or more of particles that do not pass through a 1.25 mm mesh and that passes through a 2.5 mm mesh is mixed with cement. This problem can also be solved by providing a mixed cement. At this time,SaidWith silicateSaidA mixed cement obtained by mixing carboxylic acid in the presence of water and then solidifying the powder or granular material with cement is preferable. At this time, it is preferable that the water content of the powdery or granular material is 10% by weight or less.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
The concrete admixture of the present invention is obtained by mixing silicate and acid in the presence of water and then solidifying.
[0028]
The silicate used in the present invention is not particularly limited. The cation species is not limited to a metal ion but may be an ammonium ion or the like, but a metal ion is preferred. Among the metal ions, alkali metal ions are preferable, and sodium ions are more preferable from the viewpoint of availability of raw materials and cost. Further, the anion species of the silicate used in the present invention is not particularly limited, and orthosilicate anion [SiO_Four ^Four-] Or metasilicate anion [SiO_Three ^2-As well as anionic species such as silicic acid [SiO₂A plurality of units may be connected to form an anionic species.
[0029]
Specific examples of the compound include sodium orthosilicate, potassium orthosilicate, lithium orthosilicate, sodium metasilicate, potassium metasilicate, lithium metasilicate, and water glass.
[0030]
Among these, water glass is preferably used in the present invention. Water glass is an aqueous solution of alkali metal silicate, which is silicic acid [SiO₂A plurality of units are connected to form an anionic species. The alkali metal used here may be potassium, but is usually sodium. The general formula for solids in the case of sodium silicate is Na₂O ・ nSiO₂Indicated by
[0031]
The ratio of the number of metal atoms to the number of silicon atoms in the silicate [metal / silicon] is preferably in the range of 0.1-2. When the ratio [metal / silicon] is less than 0.1, the water solubility decreases, and it may be difficult to mix in the presence of carboxylic acid and water. More preferably, it is 0.2 or more, and further preferably 0.3 or more. Conversely, when the ratio [metal / silicon] exceeds 2, the water solubility of the silicate is too high, and the fluidity of the concrete may deteriorate. More preferably, it is 1.5 or less, and more preferably 1 or less.
[0032]
  Also, the acid mixed with silicate in the present inventionIscarboxylic acidAndCarboxylic acid usedas,Oxymonocarboxylic acids such as glycolic acid, lactic acid and gluconic acid; polyvalent carboxylic acids such as oxalic acid, malonic acid, succinic acid, pimelic acid, adipic acid, glutaric acid, maleic acid, fumaric acid, phthalic acid and terephthalic acid; Hydroxy polycarboxylic acids such as malic acid and citric acid; polyhydric carboxylic acid polymers such as acrylic acid polymer and maleic anhydride polymer can be used.. That is,An oxycarboxylic acid or polyvalent carboxylic acid having low volatility and good water solubility is preferred, and a polyvalent carboxylic acid is more preferred. Also suitable are unsaturated polyvalent carboxylic acids such as maleic acid and fumaric acid.
[0033]
When the metal salt of silicate and carboxylic acid are used in the concrete admixture of the present invention, the ratio [metal / carboxyl group] between the number of metal atoms in the silicate and the number of carboxyl groups in the carboxylic acid is 1 to 1. 200 is preferable. When the ratio [metal / carboxyl group] is less than 1, the silicic acid component becomes insoluble in water, and when the silicate and carboxylic acid are mixed in the presence of water, insoluble matter is generated and uniform. There is a possibility that it cannot be mixed. More preferably, it is 2 or more, more preferably 5 or more, and most preferably 10 or more. Conversely, if the ratio [metal / carboxyl group] exceeds 200, the water solubility of the silicate is too high, and the fluidity of the concrete may deteriorate. More preferably, it is 100 or less, More preferably, it is 50 or less.
[0034]
The concrete admixture of the present invention is produced by mixing the silicate and acid as described above in the presence of water. By mixing in the presence of water, a neutralization reaction (formation of salt) proceeds between the cationic species forming the silicate and the acid, and the water solubility of the silicate is moderately reduced. Seems to be able to. The amount of water to be present at the time of mixing is preferably 1 part by weight or more, more preferably 10 parts by weight or more, and more preferably with respect to 100 parts by weight of the total weight of silicate and acid. Is 100 parts by weight or more. The mixing method is not particularly limited as long as these components can be mixed in a fluid state, but a method of mixing and stirring silicate and acid in an aqueous solution state is preferable. For example, a method of adding and stirring carboxylic acid or an aqueous solution thereof to water glass is exemplified. In order to facilitate stirring, it is also preferable to increase the temperature and mix.
[0035]
The concrete admixture of the present invention is produced by solidifying after mixing as described above. It may be solidified by removing water or may be solidified by cooling. Among these, a method in which water is removed from the aqueous solution and solidified after mixing the silicate and the acid is preferable. The method for removing moisture is not particularly limited, and the moisture may be volatilized by standing at room temperature, or the moisture may be volatilized by heating. The water content after removing the water is preferably 50% by weight or less. The water content is more preferably 40% by weight or less, and further preferably 30% by weight or less. The concrete admixture of the present invention can contain a considerable amount of moisture even in the solid state. Further, as will be described later, when a mixed cement previously blended with cement is produced, it is preferable to further reduce the moisture content. In addition, the moisture content here is a value measured by the method described in JIS K0101-16.2.
[0036]
Moreover, the concrete admixture of the present invention is a concrete admixture composed of a powdery or granular material containing a reaction product of silicate and acid. A reaction product here is a product by an acid-base reaction (neutralization reaction) in which a weak acid (silicic acid) is liberated to form a stronger acid salt. The concrete admixture of the present invention can exhibit the effects of the present invention by containing such a reaction product. As described above, it is preferable to manufacture by a method in which silicate and acid are mixed in the presence of water and then solidified. What is necessary is just to contain the thing. Moreover, the powdery body or granular body containing such a reaction product can be used as a mortar admixture described later or as a raw material for mixed cement.
[0037]
The concrete admixture of the present invention is preferably a powdery body or a granular body. There are no particular limitations on the method of forming the powder or granule, and examples include a method of solidifying and then pulverizing, and a method of solidifying droplets. Moreover, it is good also as a powdery body or a granular body in the middle stage to solidify. The size of the particles in the case of a powder or granule is not particularly limited, but it is preferable not to use fine powder, for example, particles having a particle size of less than 100 μm as the main constituent particles, and conversely coarse particles, It is preferable not to use particles whose particle diameter exceeds 10 mm as the main constituent particles.
[0038]
If the particle size is too small, the fluidity of the concrete may be reduced when the concrete admixture of the present invention is added to the concrete. Conversely, if the particle size is too large, the hardened concrete may be inhomogeneous. Further, if the particle size is too small or too large, the effect of improving the tensile strength tends to decrease, and the effect of improving the tensile strength is increased by using particles having a certain range of particle sizes. The reason for this is not clear, but because the particle size is appropriate, the silicate component can be appropriately supplied to the transition zone at the right time when the hydration reaction is proceeding after concrete placement. It is thought that there is not.
[0039]
The suitable particle size varies depending on the chemical composition and water content of the concrete admixture, and also varies depending on the method of addition to the concrete, so it must be adjusted accordingly. It is preferable that there are not too many fine particles. For example, particles that do not pass through a 1.25 mm mesh are preferably 50% by weight or more, more preferably 80% by weight or more. On the other hand, it is preferable that there are not too many particles having a large particle size, and those that pass through a 2.5 mm mesh are 50% by weight or more, more preferably 80% by weight or more. The dimensions of the mesh are those specified in JIS Z8801.
[0040]
The concrete obtained by the present invention is composed of cement, aggregate, water and the concrete admixture. The term “concrete” as used herein includes both fluid concrete before being placed (fresh concrete) and hardened concrete after being placed.
[0041]
At this time, the cement used may be a hydraulic cement containing calcium silicate, and Portland cement, blast furnace cement, or the like can be used.
[0042]
The concrete of the present invention is blended with aggregates. As described above, the concrete admixture of the present invention is presumed to improve the adhesive strength mainly at the transition zone that is the interface between the coarse aggregate and the mortar. It is meaningful to add to it. The aggregate to be used is not particularly limited. In addition to aggregates obtained from natural minerals, aggregates made from blast furnace slag, fly ash, waste concrete, or the like, or artificial aggregates can be used. The amount of aggregate is preferably 300 to 1200 parts by weight and more preferably 500 to 800 parts by weight with respect to 100 parts by weight of cement.
[0043]
The size of the aggregate is not limited, but fine aggregates (those that pass through a 5 mm mesh and usually stay at 75 μm mesh) and coarse aggregates (those that stay at 5 mm mesh, usually up to about 200 mm) ) Or both of them may be used in combination. Since an aggregate having a larger size is more likely to form a transition zone portion around the aggregate, there is a great advantage in using the concrete admixture of the present invention in concrete mixed with coarse aggregate. The amount of the coarse aggregate is preferably 100 to 800 parts by weight and more preferably 150 to 500 parts by weight with respect to 100 parts by weight of cement. It is preferable to further contain fine aggregate in addition to coarse aggregate, and the blending amount is preferably 100 to 800 parts by weight, and 150 to 500 parts by weight with respect to 100 parts by weight of cement. More preferred.
[0044]
The amount of water blended in the concrete of the present invention is preferably 20 to 75 parts by weight and more preferably 30 to 60 parts by weight with respect to 100 parts by weight of cement.
[0045]
The concrete of the present invention is obtained by adding the above-mentioned concrete admixture in addition to cement, aggregate and water. The addition amount is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of cement. If the amount added is less than 0.1 parts by weight, the effect of improving the tensile strength may be insufficient. The addition amount is more preferably 0.5 parts by weight or more, and even more preferably 1 part by weight or more. If the added amount exceeds 20 parts by weight, the fluidity of the concrete may be lowered, and the effect of improving the tensile strength may be lowered. The addition amount is more preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less.
[0046]
You may mix | blend components other than the above with concrete in the range which does not inhibit the effect of this invention. Depending on the application and required performance, known additives such as water reducing agents, air entraining agents (AE agents), fluidizing agents, setting retarders, and the like can be blended. Further, depending on the use, it is also preferable to blend a short fiber reinforcing material made of inorganic fiber such as asbestos or glass fiber or synthetic fiber.
[0047]
The method for producing the concrete of the present invention is not particularly limited. The aforementioned materials may be blended and kneaded at the same time, or may be added and blended sequentially. For example, it may be manufactured by batch kneading in a ready mixed concrete (fresh concrete) plant. However, in order to keep the flow state before placing well, it is preferable to post-add the concrete admixture of the present invention to the flow state concrete composed of cement, aggregate and water. By doing so, it becomes easy to improve the tensile strength of the concrete after curing while maintaining good fluidity of the concrete at the time of placing. Specifically, ready-mixed concrete manufactured at a ready-mixed concrete plant is transported to a construction site with a concrete mixer truck, and the concrete admixture of the present invention is introduced into the mixer at the construction site, and then immediately placed after kneading. The method to do is illustrated as a suitable thing. In addition, as will be described later, a mixed cement formed by mixing a powdery or granular material obtained by mixing a silicate and an acid in the presence of water and then solidifying the cement is used as a raw material. You may mix | blend aggregate and water.
[0048]
The concrete of the present invention thus obtained is placed in a mold in a fluid state and cured. Since the concrete after hardening has an increased tensile strength, the amount of steel used for reinforcement can be reduced as compared with a conventional concrete structure. On the other hand, even when the steel material is placed in a formwork in which the steel material is arranged, particularly in a formwork in which the steel material is arranged in a complicated manner, the actual benefit of implementing the present invention is great. This is because by adding the concrete admixture of the present invention, it is possible to reinforce the weak point derived from bleeding that occurs on the lower side of the reinforcing bar.
[0049]
The concrete of the present invention can be used to construct various structures. Since the concrete structure using the concrete of the present invention has high tensile strength, it is particularly effectively used for a member that easily generates tensile stress due to external force or temperature stress, or a member that is easily affected by fatigue. It is also used effectively when constructing a structure having a complicated shape. Specific applications include roads and railway facilities such as pavements, piers, and tunnels; port facilities; airport facilities; river and coastal facilities such as retaining walls and embankments; energy facilities such as nuclear power plants and thermal power plants; Examples include water treatment facilities such as waterways; general buildings.
[0050]
The concrete of the present invention can also be used to produce various concrete products (concrete secondary products). In this case, the same shape can be mass-produced at the factory. After placing the concrete of the present invention in a mold, it is cured to produce a concrete product. Since it can be produced in the factory, various molding methods such as extrusion molding, press molding, pressure molding, vibration molding, roller rolling molding, and centrifugal force molding can be employed. Since the concrete product using the concrete of the present invention has high tensile strength, it is useful as a product susceptible to tensile stress due to external force or temperature stress or a product susceptible to fatigue. It is also useful as a product having a complicated shape or a thin product. Specific examples of concrete products include blocks, pipes, columns, piles, retaining walls, and grooves.
[0051]
The concrete admixture and its production method and application have been described above. Hereinafter, the mortar admixture will be described. Mortar should be said to be concrete that does not contain coarse aggregate, and usually uses cement, fine aggregate (sand) and water as its main raw materials.
[0052]
The mortar admixture of the present invention is obtained by mixing a silicate and an acid in the presence of water and then solidifying them. As the mortar admixture of the present invention, the same concrete admixture described above is used.
[0053]
The mortar obtained in the present invention is composed of cement, fine aggregate, water and the mortar admixture. The mortar here includes both a mortar in a fluidized state before being cured and a cured mortar. The cement used here is the same as that used in the above concrete.
[0054]
The mortar of the present invention contains fine aggregates but does not contain coarse aggregates. As described above, in the concrete admixture of the present invention, it is presumed that the improvement of the adhesive strength in the transition zone, which is the interface between the coarse aggregate and the mortar, is a factor in improving the tensile strength. Since the tensile strength is also improved in the mortar of the present invention, it seems that the adhesive strength is also improved at the interface between the fine aggregate and the cement paste.
[0055]
The fine aggregate passes through a 5 mm mesh and usually stays at 75 μm mesh. The fine aggregate used in the mortar of the present invention is not particularly limited, in addition to fine aggregate obtained from natural minerals such as sand, fine aggregate made from blast furnace slag, fly ash, waste concrete, etc., Artificial aggregates can also be used. The blending amount of the fine aggregate is preferably 100 to 800 parts by weight, more preferably 150 to 500 parts by weight with respect to 100 parts by weight of cement.
[0056]
The amount of water blended in the mortar of the present invention is preferably 20 to 75 parts by weight and more preferably 30 to 60 parts by weight with respect to 100 parts by weight of cement. The amount of the mortar admixture added to the mortar of the present invention is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of cement. If the amount added is less than 0.1 parts by weight, the effect of improving the tensile strength may be insufficient. The addition amount is more preferably 0.5 parts by weight or more, and even more preferably 1 part by weight or more. If the addition amount exceeds 20 parts by weight, the fluidity of the mortar before curing may be lowered, and the effect of improving the tensile strength may be lowered. The addition amount is more preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less.
[0057]
You may mix | blend components other than the above with mortar in the range which does not inhibit the effect of this invention. Known additives such as a water reducing agent, an air entraining agent (AE agent), a fluidizing agent, a setting retarding agent, a swelling agent, and a quick setting agent can be blended depending on the application and required performance. Further, depending on the use, it is also preferable to blend a short fiber reinforcing material made of inorganic fiber such as asbestos or glass fiber or synthetic fiber.
[0058]
The method for producing the mortar of the present invention is not particularly limited. The aforementioned materials may be blended and kneaded at the same time, or may be added and blended sequentially. In addition, as will be described later, a mixed cement formed by mixing a powdery or granular material obtained by mixing a silicate and an acid in the presence of water and then solidifying the cement is used as a raw material. Fine aggregate and water may be blended.
[0059]
The fluidized mortar thus obtained is molded and then cured to produce a mortar product. The molding method is not particularly limited, and may be cured after being injected into a mold, and various molding methods such as extrusion molding, press molding, pressure molding, vibration molding, roller compaction molding, and centrifugal force molding. Can also be adopted. Moreover, the mortar in a fluid state can be sprayed or troweled on the substrate.
[0060]
Since the mortar product using the mortar of the present invention has high tensile strength, it is useful as a product susceptible to tensile stress due to external force or temperature stress or a product susceptible to fatigue. It is also useful as a product having a complicated shape or a thin product. Specific examples of mortar products include blocks, pipes, retaining walls, curbs, side grooves, and formwork.
[0061]
The concrete admixture and the mortar admixture have been described above. Hereinafter, a mixed cement which is another embodiment of the present invention will be described. The mixed cement of the present invention is a mixed cement obtained by mixing a powdery or granular material obtained by mixing a silicate and an acid in the presence of water and then solidifying the cement.
[0062]
As the powder or granule used in the mixed cement of the present invention, the powder or granule used as the above-mentioned concrete admixture or mortar admixture is used. However, since it is necessary to prevent cement blocking or weathering over a long period of time in a state of being mixed with cement, it is more preferable that the moisture content is lower. Accordingly, the preferred water content is 20% by weight or less, more preferably 10% by weight or less, more preferably 5% by weight or less, and most preferably 1% by weight or less.
[0063]
The blending ratio of the cement and the powdery or granular material in the mixed cement of the present invention is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the cement. If the amount added is less than 0.1 parts by weight, the effect of improving the tensile strength may be insufficient. The addition amount is more preferably 0.5 parts by weight or more, and even more preferably 1 part by weight or more. If the added amount exceeds 20 parts by weight, the fluidity of the concrete or mortar before curing may be lowered, and the effect of improving the tensile strength may be lowered. The addition amount is more preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less. Moreover, the cement used here is the same as that used in the above-mentioned concrete and mortar.
[0064]
The mixed cement thus obtained is suitably used as a raw material for concrete and mortar. Since an appropriate amount of the powdery or granular material is blended in advance with cement, it is only necessary to knead with water, aggregate, etc., as in ordinary cement, and the blending operation of raw materials is easy. . Moreover, it can be made to distribute | circulate similarly to normal cement as mixed cement, and concrete and mortar with improved tensile strength can be easily manufactured at a construction site or a factory.
[0065]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1 (Production of Admixtures A and B)
In a container containing 15 kg of water having a water temperature of 60 ° C., 120 g of fumaric acid was charged and dissolved by stirring. Subsequently, 25 kg of water glass “JIS No. 3 sodium silicate” manufactured by Toso Sangyo Co., Ltd. was added while stirring was continued. At this time, the viscosity temporarily increased greatly in the portion where water glass was added, but the whole was homogenized by stirring. This operation was repeated to add the whole amount of water glass to prepare an aqueous solution having no uniform insoluble matter as a whole.
[0066]
The water glass used here is sodium oxide (Na₂O: MW = 61.98) 9 to 10% by weight of component, silicon dioxide (SiO₂: MW = 60.09) containing 28 to 30% by weight of the component. When the median value is adopted and the sodium oxide component is 9.5 wt% and the silicon dioxide component is 29 wt%, the ratio [metal / silicon] is 0.64. In addition, the number of sodium atoms and fumaric acid (C_FourH_FourO_Four: MW = 116.07), the value of the ratio [metal / carboxyl group] to the carboxyl group was 37.
[0067]
The obtained aqueous solution was poured into a plastic tray with a thickness of about 5 mm and left at room temperature for 3 days to evaporate moisture and solidify. The solidified product thus obtained was hydrogel and had some flexibility. The solidified product was placed in a 2.5 mm mesh sieve and extruded from between the meshes using a bar. The extruded particles were spread on a vinyl sheet and dried by blowing hot air at 50 ° C. for 24 hours with a fan. After drying, the particles that were slightly stuck together were separated and then passed through a 2.5 mm mesh sieve. The particles that passed through the sieve were used as the admixture A used in this example, and the particles remaining on the sieve were used as the admixture B used in this example. When Admixture A was passed through a 1.25 mm mesh screen, about 10% by weight passed through the screen and about 90% by weight remained on the screen. The admixture B contained particles having a maximum size of about 7 mm.
[0068]
The water content of the admixtures A and B thus obtained was measured based on JIS K0101-16.2 and found to be 25.5% by weight. Since these admixtures A and B are hygroscopic, when they are stored in a polyethylene bag together with a desiccant and mixed with ready-mixed concrete, or when mixed with fine aggregate and sand to produce mortar, I took it out and used it each time.
[0069]
Example 2 (Production of Admixture C)
In Example 1, an aqueous solution was prepared in the same manner as in Example 1 except that 1440 g of citric acid was used instead of 120 g of fumaric acid. The number of sodium atoms and the trivalent acid citric acid (C₆H₈O₇: MW = 192.13) The ratio [metal / carboxyl group] ratio to the carboxyl group was 3.4.
[0070]
The obtained aqueous solution was solidified and dried in the same manner as in Example 1. After drying, the particles slightly stuck to each other were separated, passed through a 2.5 mm mesh sieve, and the particles that passed through the sieve were used as the admixture C used in this example. When Admixture C was passed through a 1.25 mm mesh screen, about 10% by weight passed through the screen and about 90% by weight remained on the screen. The water content of the admixture C thus obtained was measured based on JIS K0101-16.2 and found to be 30% by weight. Since this admixture C has hygroscopicity, it was stored and used in the same manner as in Example 1.
[0071]
Example 3 (Production of Admixture D)
Admixture A produced in Example 1 was put into a frying pan and heated on a gas stove. By heating, the admixture particles expanded due to evaporation of water in the admixture, but after 5 minutes, such expansion was not observed, and the heating was terminated. After cooling, the particles slightly stuck to each other were separated and then passed through a 2.5 mm mesh sieve. The particles that passed through the sieve were used as the admixture D used in this example. When Admixture D was passed through a 1.25 mm mesh screen, about 10% by weight passed through the screen and about 90% by weight remained on the screen.
[0072]
The water content of the admixture D thus obtained was measured based on JIS K0101-16.2 and found to be 0% by weight. Since this admixture D is hygroscopic, it was stored and used in the same manner as in Example 1. In addition, since the admixture D does not contain moisture, blocking or weathering will not occur even if the admixture is added to the cement in advance, and it can be stored for a long time, and can be distributed as a mixed cement. Is possible.
[0073]
Example 4 (Manufacture and evaluation of admixture A-added concrete)
The ready-mixed concrete used as the base concrete uses the following raw materials.
1) Cement
Normal Portland cement manufactured by Ube Industries, Ltd., density 3.16 g / cm³, Sodium content (Na₂O conversion value) 0.68% by weight.
2) Coarse aggregate
Kuzukaku crushed stone (2005), grain size 5-20mm, actual volume ratio 60.0%, surface dry density 2.70g / cm³Water absorption 0.89% by weight.
3) Fine aggregate 1
Kuzu production crushed sand, grain size 5mm or less, coarse grain ratio 3.20, density at the time of surface drying 2.63g / cm³Water absorption 1.22% by weight.
4) Fine aggregate 2
Sahara land sand, grain size 1.2mm, coarse grain rate 1.80, surface drying density 2.58g / cm³Water absorption 2.16% by weight.
5) AE water reducing agent
“Darlex WRDA” manufactured by Grace Chemicals
[0074]
The blending ratio of the above components is as follows. The numerical value in the parenthesis is the blending ratio with respect to 100 parts by weight of cement. The slump value of this base concrete is 8 cm.
Cement 283kg / m³(100 parts by weight)
162 kg / m of water³(57 parts by weight)
Coarse aggregate 1058kg / m³(374 parts by weight)
Fine aggregate 1 491kg / m³(173 parts by weight)
Fine aggregate 2 321kg / m³(113 parts by weight)
AE water reducing agent 1.698kg / m³(0.6 parts by weight)
[0075]
To the base concrete, the admixture A obtained in Example 1 was added to 2.5 parts by weight with respect to 100 parts by weight of cement, and after stirring for 30 seconds with a forced kneading mixer, The concrete sample was poured into a cylindrical mold having a thickness of 200 mm. A plurality of these were prepared and cured in air at 20 ° C. For Example 4, Example 5, Example 6 and Comparative Example 1 described below, samples were prepared on the same day using the same lot of base concrete and cured under the same environment. .
[0076]
Samples on the 7th, 28th, and 91st days were subjected to a strength measurement test. The compressive strength test was measured according to JIS A1108-1999, and the split tensile strength test was measured according to JIS A1113-1999. At this time, three samples were measured for each test (n = 3), and the average value was obtained. The obtained tensile strength, compressive strength and α value are summarized in Table 1. Here, the α value is a value represented by the following formula (3), and is a value indicating a correlation between the tensile strength and the compressive strength.
(Tensile strength) = α × (Compressive strength)^2/3      (3)
[0077]
Based on JSCE-G502-1999, the compression-side elastic modulus was measured for a sample with a material age of 28 days using a compression meter. Elastic modulus is about 30000 N / mm²The strain was about 0.002 when the maximum value of the compressive stress was shown. Moreover, the result of having cut out the sample of material age 91 and measuring the pore distribution with a porosimeter is shown in FIG. FIG. 3 shows a photograph of the fracture surface of the 28-day-old sample fractured in the split tensile strength test.
[0078]
Example 5 (Production and evaluation of admixture B-added concrete)
In Example 4, instead of using 2.5 parts by weight of Admixture A, a concrete sample was prepared in the same manner as in Example 4 except that 2.5 parts by weight of Admixture B obtained in Example 1 was used. . Samples on days 7 and 28 were subjected to the same strength measurement test as in Example 4. The obtained tensile strength, compressive strength and α value are summarized in Table 1. The compression-side elastic modulus was measured in the same manner as in Example 4 for the sample with a material age of 28 days. Elastic modulus is about 29000 N / mm²The strain was about 0.002 when the maximum value of the compressive stress was shown.
[0079]
Example 6 (Production and Evaluation of Admixture A and Admixture B-added concrete)
In Example 4, instead of using 2.5 parts by weight of Admixture A, 2.5 parts by weight of Admixture A obtained in Example 1 and 2.5 parts by weight of Admixture B were added (a total of 5 parts by weight of the admixture). A concrete sample was prepared in the same manner as in Example 4 except that the addition was performed. Samples on days 7 and 28 were subjected to the same strength measurement test as in Example 4. The obtained tensile strength, compressive strength and α value are summarized in Table 1.
[0080]
Comparative Example 1 (Production and evaluation of admixture without additive)
In Example 4, the admixture A was not used, and only the base concrete was poured into the mold to obtain a concrete sample. Thereafter, the curing was performed in the same manner as in Example 4. The samples on the 7th, 28th and 91st days of the material age were subjected to the same strength measurement test as in Example 4. The obtained tensile strength, compressive strength and α value are summarized in Table 1. The compression-side elastic modulus was measured in the same manner as in Example 4 for the sample with a material age of 28 days. Elastic modulus is about 26000 N / mm²The strain was about 0.002 when the maximum value of the compressive stress was shown. Moreover, the result of having cut out the sample of material age 91 and measuring the pore distribution with a porosimeter is shown in FIG. FIG. 4 shows a photograph of a fracture surface of a sample with a material age of 28 that was fractured in the split tensile strength test.
[0081]
Comparative Example 2 (Manufacture of concrete added with aqueous solution before solidification)
In the same manner as in Example 1, the aqueous fumaric acid solution and water glass were mixed and stirred and dissolved. The aqueous solution thus obtained was added to the base concrete used in Example 4 without solidifying. The amount added was 5 parts by weight with respect to 100 parts by weight of cement. As a result, the fluidity of the concrete decreased significantly immediately after the addition, and it was difficult to pour into the mold.
[0082]
[Table 1]

[0083]
Analysis of the results of Examples 4-6 and Comparative Example 1
The time-dependent changes in the split tensile strength obtained in the above examples are shown in FIG. 5, and the time-dependent changes in the compressive strength are shown in FIG. In Example 4 (admixture A addition), compared with Comparative Example 1 (base concrete), the tensile strength was improved by nearly 60% on the 7th day of the material age and nearly 40% on the 28th and 91st days of the material age. On the other hand, the improvement of the compressive strength was limited to about 10 to 20%. In Example 5 in which Admixture B having a particle size larger than that of Admixture A was added, the improvement in tensile strength was smaller than in Example 4. In Example 6 in which the amount of the concrete admixture added was double that of Examples 4 and 5, the effect of improving the strength was small.
[0084]
About each strength data obtained in Example 4 (additive A addition) and Comparative Example 1 (base concrete), the compressive strength is plotted on the horizontal axis and the split tensile strength is plotted on the horizontal axis. The results plotted on the vertical axis are shown in FIG.
As a result, the intensity data obtained in Example 4 approximated to a curve in which α was set to 0.31 in Equation (3), and the intensity data obtained in Comparative Example 1 set α to 0.23. Approximate the curve.
That is, in Example 4 to which the admixture A was added, the α value was improved by about 35% compared to the base concrete, and the tensile strength assumed from the same compressive strength was improved by 35%. . As described above, the concrete of the present invention shows an outstanding feature in that the improvement of the tensile strength is remarkable as compared with the improvement of the compressive strength.
[0085]
In Example 4 (Admixture A addition), Example 5 (Admixture B addition) and Comparative Example 1 (Base concrete), the compression-side elastic modulus of the sample on the 28th day of the age was measured. The maximum compressive stress was exhibited at a strain of about 0.002, and no significant difference was observed in the stress value. That is, although the compression-side elastic modulus was slightly increased by adding the admixture of the present invention, no significant change was observed in the compression behavior.
[0086]
Moreover, about the concrete obtained in Example 4 (admixture A addition) and the comparative example 1 (base concrete), the result of having performed pore distribution measurement with the porosimeter is shown in FIG.1 and FIG.2, respectively. By adding the admixture of the present invention, it was recognized that pores of about 0.5 to 10 μm decreased and pores of about 0.01 to 0.1 μm increased.
[0087]
Moreover, the photograph of the fracture surface in the tensile test of the concrete obtained in Example 4 (admixture A addition) and the comparative example 1 (base concrete) is shown in FIG.3 and FIG.4, respectively. As is clear from FIG. 4, the base concrete has many portions that are broken at the interface between the coarse aggregate and the mortar, indicating that the transition zone is a weak point. In contrast, as shown in FIG. 3, when the admixture of the present invention is added, there are many portions where the coarse aggregate is broken, and the adhesive strength at the transition zone portion is greatly improved. It is suggested.
[0088]
Example 7 (Production / Evaluation of Admixture C-added Concrete)
The ready-mixed concrete used as the base concrete uses the following raw materials.
1) Cement
Taiheiyo Cement Co., Ltd. normal Portland cement, density 3.16 g / cm³, Sodium content (Na₂O conversion value) 0.58% by weight.
2) Coarse aggregate 1
Hachioji crushed stone No. 5, grain size 5-20mm, coarse particle ratio 7.04, surface dry density 2.67g / cm³Water absorption 0.55% by weight.
3) Coarse aggregate 2
Hachioji crushed stone No. 6, grain size 2.5-10mm, coarse grain ratio 5.88, surface dry density 2.67g / cm³Water absorption 0.69% by weight.
4) Fine aggregate
Kimitsu mountain sand, grain size of 5mm or less, coarse grain ratio of 2.64, density at surface drying of 2.60g / cm³Water absorption rate 2.23% by weight.
[0089]
The blending ratio of the above components is as follows. The numerical value in the parenthesis is the blending ratio with respect to 100 parts by weight of cement. The slump value of this base concrete is 8 cm.
Cement 320.0kg / m³(100 parts by weight)
Water 176.0kg / m³(55 parts by weight)
Coarse aggregate 1 564.3kg / m³(176 parts by weight)
Coarse aggregate 2 376.2kg / m³(118 parts by weight)
Fine aggregate 842.2kg / m³(263 parts by weight)
[0090]
A concrete sample was prepared in the same manner as in Example 4 except that the admixture C obtained in Example 2 was added to the base concrete so as to be 2 parts by weight with respect to 100 parts by weight of cement. A plurality of these were prepared and cured in air at 15 ° C. For Example 7 and Comparative Example 3 described below, samples were prepared on the same day using the same lot of base concrete and cured under the same environment. Samples on days 7 and 28 were subjected to the same strength measurement test as in Example 4. The obtained tensile strength, compressive strength and α value are shown together in Table 2.
[0091]
Comparative Example 3 (Production / Evaluation of Additive-Free Concrete)
In Example 7, the admixture C was not used, and only the base concrete was poured into a formwork to obtain a concrete sample. Thereafter, curing was performed in the same manner as in Example 7. Samples on days 7 and 28 were subjected to the same strength measurement test as in Example 4. The obtained tensile strength, compressive strength and α value are shown together in Table 2.
[0092]
[Table 2]

[0093]
As is clear from Table 2, the concrete of Example 7 to which the admixture C was added had a clearly improved tensile strength compared to the concrete of Comparative Example 3 to which no admixture was added. On the other hand, the compressive strength of the concrete of Example 7 was slightly lower than that of the concrete of Comparative Example 3. That is, only the tensile strength is selectively improved as compared with the compressive strength, and this point is also indicated by an increase in the α value. This test result is the same as the results of Examples 4 to 6 in which fumaric acid is used as the carboxylic acid as a raw material for the admixture. It was.
[0094]
Example 8 (Manufacture and evaluation of admixture D-added concrete)
The ready mixed concrete used as the base concrete has the same specifications as in Example 7. A concrete sample was prepared in the same manner as in Example 4 except that the admixture D obtained in Example 3 was added to the base concrete so as to be 1 part by weight with respect to 100 parts by weight of cement. A plurality of these were prepared and cured in air at 20 ° C. For Example 8 and Comparative Example 4 described below, samples were prepared on the same day using the same lot of base concrete and cured under the same environment. Samples on days 7 and 28 were subjected to the same strength measurement test as in Example 4. The obtained tensile strength, compressive strength, and α value are summarized in Table 3.
[0095]
Comparative Example 4 (Production / Evaluation of Additive-Free Concrete)
In Example 8, the admixture D was not used, and only the base concrete was poured into the formwork to obtain a concrete sample. Thereafter, curing was performed in the same manner as in Example 8. Samples on days 7 and 28 were subjected to the same strength measurement test as in Example 4. The obtained tensile strength, compressive strength, and α value are summarized in Table 3.
[0096]
[Table 3]

[0097]
As is apparent from Table 3, the concrete of Example 8 to which the admixture D was added had improved tensile strength compared to the concrete of Comparative Example 4 to which no admixture was added. Although the blending amount of the admixture in Example 8 was as small as 1 part by weight with respect to 100 parts by weight of cement, the tensile strength was clearly improved. On the other hand, the compressive strength of the concrete of Example 8 was slightly lower than that of the concrete of Comparative Example 4. That is, even in this case, only the tensile strength is selectively improved as compared with the compressive strength, and this point is also indicated by an increase in the α value. Thus, it was found that the tensile strength was improved even when a low water content was used as an admixture or when a small amount was added.
[0098]
Example 9 (Production and evaluation of admixture A added mortar)
In this example, the following raw materials were used.
1) Cement
Taiheiyo Cement Co., Ltd. normal Portland cement, density 3.16 g / cm³, Sodium content (Na₂O conversion value) 0.58% by weight.
2) Fine aggregate
Kimitsu mountain sand, grain size of 5mm or less, coarse grain ratio of 2.64, density at surface drying of 2.60g / cm³Water absorption rate 2.23% by weight.
[0099]
The above cement, fine aggregate and water were first stirred with a forced kneading mixer for 1 minute, and then the admixture A obtained in Example 1 was post-added and further stirred for 30 seconds. The blending ratio is as follows. The numerical value in the parenthesis is the blending ratio with respect to 100 parts by weight of cement.
Cement 320.0kg / m³(100 parts by weight)
Water 176.0kg / m³(55 parts by weight)
Fine aggregate 842.2kg / m³(263 parts by weight)
Admixture A 6.4kg / m³(2 parts by weight)
[0100]
After stirring, the mixture was poured into a cylindrical mold having a diameter of 50 mm and a height of 100 mm to obtain a mortar sample. This sample form conforms to JSCE-F506-1999. A plurality of these were prepared and cured in air at 20 ° C. For Example 9 and Comparative Example 5 described below, samples were prepared on the same day and cured under the same environment. Samples on days 7 and 28 were subjected to the same strength measurement test as in Example 4. Table 4 shows the obtained tensile strength, compressive strength, and α value.
[0101]
Comparative Example 5 (Production / Evaluation of Additive-Free Mortar)
In Example 9, a mortar sample was prepared and cured in the same manner as in Example 9 except that admixture A was not used and only cement, water, and fine aggregate were blended. Samples on days 7 and 28 were subjected to the same strength measurement test as in Example 4. Table 4 shows the obtained tensile strength, compressive strength, and α value.
[0102]
[Table 4]

[0103]
As is apparent from Table 4, the tensile strength of the mortar of Example 9 in which 2 parts by weight of admixture A was added to 100 parts by weight of cement was improved compared to the mortar of Comparative Example 5 in which no admixture was added. Was. The degree of improvement is small compared to the degree of improvement in the concrete of Example 4 in which 2.5 parts by weight of admixture A is added to 100 parts by weight of cement, and the improvement in tensile strength is achieved by the addition of the admixture of the present invention. The effect is greater for concrete than for mortar. However, even in mortar, the tensile strength is clearly improved, and although it is not as high as the adhesive strength on the surface of the coarse aggregate, it seems that the adhesive strength is also improved on the surface of the fine aggregate. On the other hand, the compressive strength of the mortar of Example 9 was slightly lower than that of Comparative Example 4. Also in the case of mortar, only the tensile strength is selectively improved as compared with the compressive strength as in the case of concrete, and this point is also indicated by an increase in the α value. That is, the admixture of the present invention can improve its tensile strength even when added to mortar.
[0104]
【The invention's effect】
As explained above, the concrete to which the concrete admixture of the present invention is added has greatly improved tensile strength compared to the compressive strength, enabling reduction of cracks in the concrete structure and reduction of the amount of steel used. It can be done. The concrete admixture only needs to be added to the concrete in a fluid state, and the fluidity of the concrete can be maintained. Thereby, the concrete used suitably with respect to the various concrete structures which are increasing in size and diversified can be provided. Moreover, the concrete used suitably also with respect to various concrete products can be provided.
[0105]
In addition, the mortar to which the mortar admixture of the present invention is added also has a greatly improved tensile strength compared to the compressive strength, and is susceptible to fatigue due to products susceptible to tensile stress due to external force or temperature stress. It is suitably used for products. It is also useful for products with complex shapes and thin products, and can provide various mortar products. Furthermore, the mixed cement of the present invention is useful for producing concrete and mortar excellent in tensile strength.
[Brief description of the drawings]
1 is a diagram showing the pore distribution of concrete in Example 4. FIG.
FIG. 2 is a view showing the pore distribution of the concrete of Comparative Example 1.
3 is a photograph of a fracture surface of concrete in Example 4. FIG.
4 is a photograph of a fracture surface of concrete in Comparative Example 1. FIG.
FIG. 5 is a graph showing changes with time in splitting tensile strength.
FIG. 6 is a graph showing changes in compressive strength over time.
FIG. 7 is a graph showing the relationship between compressive strength and split tensile strength.

Claims (16)

Containing a reaction product of an alkali metal silicate and at least one carboxylic acid selected from the group consisting of oxycarboxylic acid and polyvalent carboxylic acid, the number of metal atoms in the silicate and the carboxylic acid The ratio [metal / carboxyl group] to the number of carboxyl groups in the acid is 2 to 200, the water content is 50% by weight or less, and the particles that do not pass through the 1.25 mm mesh are 50% by weight or more. A concrete admixture comprising a powdery or granular material in which particles passing through a 2.5 mm mesh are 50% by weight or more. Concrete admixture according to claim 1, wherein comprising a powder, or granules comprising solidifying are mixed in the presence of the silicate and the carboxylic acid water. An alkali metal silicate, and at least one carboxylic acid selected from the group consisting of oxycarboxylic acid and polyvalent carboxylic acid, the number of metal atoms in the silicate and the number of carboxyl groups in the carboxylic acid And mixed in an aqueous solution so that the ratio of [metal / carboxyl group] is 2 to 200, and after removing water from the mixed aqueous solution and solidifying, the water content is 50% by weight or less and 1.25 mm A method for producing a concrete admixture to obtain a powdery or granular material in which particles that do not pass through the mesh are 50% by weight or more and particles that pass through a 2.5 mm mesh are 50% by weight or more.   A concrete comprising the concrete admixture according to claim 1, cement, aggregate and water.   A method for constructing a concrete structure in which a concrete in a fluid state comprising cement, aggregate, concrete admixture according to claim 1 or 2 and water is placed in a mold and cured.   6. The method for constructing a concrete structure according to claim 5, wherein the concrete admixture is post-added to a fluidized concrete composed of cement, aggregate, and water and then placed in a mold.   A method for producing a concrete product, wherein a concrete in a fluid state comprising cement, aggregate, the concrete admixture according to claim 1 or 2 and water is placed in a mold and cured.   The method for producing a concrete product according to claim 7, wherein the concrete admixture is added afterwards to concrete in a fluid state composed of cement, aggregate and water and then placed in a mold. Containing a reaction product of an alkali metal silicate and at least one carboxylic acid selected from the group consisting of oxycarboxylic acid and polyvalent carboxylic acid, the number of metal atoms in the silicate and the carboxylic acid The ratio [metal / carboxyl group] to the number of carboxyl groups in the acid is 2 to 200, the water content is 50% by weight or less, and the particles that do not pass through the 1.25 mm mesh are 50% by weight or more. A mortar admixture comprising a powdery or granular material containing 50% by weight or more of particles passing through a 2.5 mm mesh. Mortar admixture according to claim 9, consisting of powdery material or particulate material comprising solidifying are mixed in the presence of the silicate and the carboxylic acid water. An alkali metal silicate, and at least one carboxylic acid selected from the group consisting of oxycarboxylic acid and polyvalent carboxylic acid, the number of metal atoms in the silicate and the number of carboxyl groups in the carboxylic acid And mixed in an aqueous solution so that the ratio of [metal / carboxyl group] is 2 to 200, and after removing water from the mixed aqueous solution and solidifying, the water content is 50% by weight or less and 1.25 mm A method for producing a mortar admixture that obtains a powder or granule having 50% by weight or more of particles that do not pass through the mesh and 50% by weight or more of particles that pass through the 2.5 mm mesh.   A mortar comprising the mortar admixture according to claim 9 or 10, cement, fine aggregate, and water.   A method for producing a mortar product, comprising molding and curing a mortar in a fluid state comprising cement, fine aggregate, the mortar admixture according to claim 9 or 10 and water. Containing a reaction product of an alkali metal silicate and at least one carboxylic acid selected from the group consisting of oxycarboxylic acid and polyvalent carboxylic acid, the number of metal atoms in the silicate and the carboxylic acid The ratio [metal / carboxyl group] to the number of carboxyl groups in the acid is 2 to 200, the water content is 50% by weight or less, and the particles that do not pass through the 1.25 mm mesh are 50% by weight or more. A mixed cement obtained by mixing a powder or granular material in which particles passing through a 2.5 mm mesh are 50% by weight or more and cement. The silicate and the carboxylic acid becomes mixed and made to solidify from powder material or granules in the presence of water are mixed to cement claim 14 mixed cement according.   The mixed cement according to claim 14 or 15, wherein the water content of the powder or granule is 10% by weight or less.

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