JP4570749B2 - Modified gypsum and cement admixture using the same - Google Patents
Modified gypsum and cement admixture using the same Download PDFInfo
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Description
【0001】
【発明の属する技術分野】
本発明は、石膏の粒子表面を脂肪酸類で被覆して石膏を改質することによって、水溶液中への石膏溶解速度を制御する改質石膏に関し、さらに、改質した石膏とカルシウムアルミネートとを配合することでセメント急硬材としての特性を付与でき、軟弱地盤を強固に改良するためのセメント系注入材やトンネル掘削時の地山安定化のための先受工法用注入材などに使用できる改質石膏及びそれを用いたセメント混和材に関する。
また、本発明で使用する部や%は特に規定しない限り質量基準である。
【0002】
【従来の技術とその課題】
従来、軟弱な地盤の補強や掘削地山の先行補強の目的で、セメントミルクを圧入したり、あるいは、セメントミルクに石膏とカルシウムアルミネートを添加した急硬性セメントミルクを混合注入する工法が提案されている(特開昭59-121144号公報)。
特に最近、施工サイクルの短縮化やセメント注入時のミルクの流出防止の目的などで石膏とカルシウムアルミネートを主成分とする急硬材ミルクが使用されている。
【0003】
一方、我が国の石膏源の多くは火力発電所等から排出される半水石膏や二水石膏が多く、これら石膏は水硬性や反応活性が低いことから、セメント急硬材に適する無水石膏の産出量が少ないという供給上の課題があった。
特に我が国における無水石膏は化学品原料となる弗酸製造時の副生石膏がほとんどであり、セメント急硬材原料として良質の無水石膏が乏しい現状である。
このような情勢下、無水石膏源として海外で多量に産出される天然無水石膏を使用せざるを得ない状況にあるものの、天然無水石膏は弗酸副生無水石膏に比べて、水溶性が著しく高く、セメント急硬材として使用した際、カルシウムアルミネートとの反応性が強く、特に、夏場等の高温施工条件下においてハンドリング時間やゲル化時間を調整しにくいという課題があった。
【0004】
本発明の目的とするところは、石膏の溶解速度や反応速度を調整し、カルシウムアルミネート等と混合した、セメント急硬材の凝結速度を適度に制御することであり、具体的には水溶液中への溶解速度や反応速度が著しく大きい天然無水石膏を弗酸副生石膏並みに制御する技術を得ることである。
【0005】
本発明者は、前記課題を解決するために種々検討した結果、特定の脂肪酸類で石膏粒子表面を被覆することによって石膏の溶解速度や反応速度を制御できるという知見を得て、本発明を完成するに至った。
【0006】
即ち、本発明は、石膏100質量部に対して、 (RCOO)nX(Rは飽和又は不飽和の炭化水素、nは1又は2、Xは水素、アルカリ金属、又はアルカリ土類金属)で示される脂肪酸類0.005〜1.0質量部を被覆してなる改質石膏であり、脂肪酸類が、ラウリン酸、ミリスチン酸、パルミチン酸、ステアリン酸、アラキン酸、ベヘン酸、及びオレイン酸又はそれらの塩の一種又は二種以上であることを特徴とする該改質石膏であり、脂肪酸類が、パルミチン酸、ステアリン酸、及びステアリン酸ナトリウムからなる群のうちの一種又は二種以上であることを特徴とする該改質石膏であり、脂肪酸類が、ステアリン酸であることを特徴とする該改質石膏であり、該改質石膏とカルシウムアルミネートとを配合してなるセメント混和材であり、セメントと、該セメント混和材とを含有してなるセメント組成物であり、該セメント組成物からなる注入材である。
【0007】
【発明の実施の形態】
以下、本発明を具体的に説明する。
【0008】
本発明で使用する脂肪酸類は、(RCOO)nX(Rは飽和又は不飽和の炭化水素、nは1又は2、Xは水素、アルカリ金属、又はアルカリ土類金属)で示される脂肪酸及び/又はその塩であって、具体的には、ラウリン酸、ミリスチン酸、パルミチン酸、ステアリン酸、アラキン酸、及びベヘン酸等の飽和脂肪酸やオレイン酸等の不飽和脂肪酸、又は、これらのナトリウム塩、カリウム塩、及びカルシウム塩等のアルカリ金属塩やアルカリ土類金属塩の一種又は二種以上を配合したものである。
脂肪酸類は水に溶けにくいため石膏の粒子表面に撥水性皮膜を形成し、一時的に水和活性を低下させるため、セメントコンクリートと混合した直後の初期反応を瞬間的に抑制でき、その後は正常な硬化特性を付与するものである。
脂肪酸類は、牛脂、オリーブ油、米糠油、及び動植物脂肪油等を原料とし、精製、硬化、分解、蒸留、及び分留等の工程を経て製造され、一般的には蒸留塔の操作条件等によって、高圧分解法とトイッチェル分解法に分けられる。
本発明の脂肪酸類はこれらいずれの分解法によっても製造可能である。また、その他工業生産されているものも使用可能であって、特にこれら脂肪酸類の中でもパルミチン酸やステアリン酸又はこれらの塩が、取り扱いが安全で、セメント混和材として使用した際の効果も良好である面から好ましい。
【0009】
脂肪酸類で石膏粒子表面を被覆する方法としては、石膏塊を粉砕する際、脂肪酸類を石膏塊に添加し、ボールミル、ロッドミル、及びローラーミル等の粉砕機で混合粉砕する方法、また、粉砕後の石膏に脂肪酸類を添加し、オムニミキサ、ナウタミキサ、V型ミキサ、二軸ミキサ、及び傾胴ミキサ等の混合機で混合する方法などがあり、なかでも粉砕時に添加する方法が均一に被覆できる面から好ましい。
脂肪酸類の粒度は混合粉砕する場合は特に限定されるものではないが、ミキサ等の混合機で攪拌、混合して被覆する場合は、石膏の平均粒度以下の微粉とすることが好ましく、90μm以下が好ましく、45μm以下がより好ましい。90μmを超えると混合時被覆されなかったり、分散性が不良となる場合がある。
脂肪酸類の使用量は、石膏100部に対して、5部以下が好ましく、セメント混和材として使用した際に著しい凝結低下や強度低下を生じないため、0.005〜1.0部がより好ましく、0.01〜0.1部が最も好ましい。脂肪酸類の使用量が多すぎると、改質石膏の溶解速度が小さくなり、セメン混和材としての反応活性が低下する場合がある。また、脂肪酸類の使用量が少ないと石膏の溶解速度が低下せず、天然石膏の溶解度を弗酸副生石膏程度まで低減できず、セメント混和材としてセメント系注入材やセメント急硬材などに使用した場合に反応性が大きくなりすぎ、ハンドリング時間やゲル化時間の不足、強度発現性の減少など、石膏溶解速度が速いことに起因する問題を生じる場合がある。
本発明の脂肪酸類が所定の割合で添加、被覆されているかについては、EPMA、SEM、ESCA、FT−IR、及びGC−MAS等の表面分析装置で測定可能である。
また、アルコール、エーテル、クロロホルム、ベンゼン、石油エーテル、及び脂肪油等の有機溶媒を用いて抽出後、分離精製してガスクロマトグラフ等の有機物分析によって定量可能である。
【0010】
本発明で使用する石膏とは、半水石膏や無水石膏であり、セメントと反応する反応性石膏である。特に無水石膏は水溶液中での溶解速度が大きく、セメント系注入材やセメント急硬材などとして好ましい。
【0011】
本発明で使用するカルシウムアルミネート(以下、CAという)とは、カルシアを含む原料とアルミナを含む原料を混合してキルンでの焼成や電気炉での溶融などの熱処理をして得られる、CaOとAl2O3を主たる成分とし水和活性を有する物質の総称であり、CaO及び/又はAl2O3の一部が、アルカリ金属酸化物、アルカリ土類金属酸化物、酸化ケイ素、酸化チタン、酸化鉄、アルカリ金属ハロゲン化物、アルカリ土類金属ハロゲン化物、アルカリ金属硫酸塩、及びアルカリ土類金属硫酸塩等と置換した化合物、あるいは、CaOとAl2O3を主たる成分とするものに、これらが少量固溶した物質である。
鉱物形態としては、結晶質、非晶質いずれであっても良い。特に好ましくは12CaO・7Al2O3に相当する非晶質のCAであって、電気炉で溶融したクリンカーを圧縮空気や水に接触させ、急冷することで得られる。
粉末度はブレーン法による比表面積(以下、ブレーン値という)で3,000cm2/g以上が好ましく、5,000cm2/g以上がより好ましい。ブレーン値が3,000cm2/g未満、即ち、CAの粒度が粗いとセメント急硬材としての反応性が低下し、初期強度発現性も低下する場合がある。
CAに含まれる酸化ケイ素等の不純物は少ない方が好ましく、特に酸化マグネシウムや酸化鉄はセメント硬化体に膨張性等の有害特性を与えるため、各々3%以下にすることが好ましい。特に本発明においては酸化ケイ素、酸化チタン、及び酸化鉄等のCaOやAl2O3を除く成分が少ない方が好ましく、特に酸化ケイ素、酸化チタン、及び酸化鉄の合計量が10%以下のものが好ましい。不純物が多くなるとCAの水和活性が低下する場合がある。
【0012】
改質石膏とCAの配合割合は、改質石膏25〜75部、CA75〜25部の割合であることが好ましく、改質石膏40〜60部、CA60〜40部がより好ましい。この範囲外では、セメント系注入材やセメント急硬材として使用した際のゲル化時間や強度発現性が悪化する場合がある。
【0013】
本発明のセメント混和材は、改質石膏とCAを各々単独で粉砕製造した後、ミキサ等で所定割合になるように混合する方法等によって製造可能である。
【0014】
さらに本発明では、必要に応じてセメントの凝結調整やゲル化時間調整などに通常使用されている、炭酸塩や、オキシカルボン酸又はその塩類などの硬化調整剤の他、AE剤、減水剤、AE減水剤、高性能減水剤、及び高性能AE減水剤等の化学混和剤や、高炉スラグ微粉末、シリカフューム、フライアッシュ、石灰石微粉末、及びメタカオリン粉末等のモルタルやコンクリートに用いられる混和材を配合することが可能である。
【0015】
さらに本発明のセメント混和材には、施工時の粘性改良や粉塵低減の目的で汎用の分離防止剤や粉塵低減剤を配合することが可能である。
【0016】
【実施例】
以下、実験例に基づいて本発明をさらに説明する。
【0017】
実験例1
石膏を5mm以下の粒度に調整した後、表1に示す脂肪酸類を添加して、ボールミルを用いて、ブレーン値約6,000cm2/gまで混合粉砕して改質石膏を製造し、その石膏溶解度を測定した。結果を表1に併記する。
比較のため、脂肪酸類を添加せずに粉砕したブレーン値6,000cm2/gの無水石膏を使用して同様に行った。結果を表1に併記する。
【0018】
<使用材料>
石膏α :タイ産天然石膏、
石膏β :弗酸副生石膏、市販品
脂肪酸類A:ラウリン酸、試薬
脂肪酸類B:ミリスチン酸、試薬
脂肪酸類C:パルミチン酸、試薬
脂肪酸類D:ステアリン酸、試薬
脂肪酸類E:アラキン酸、試薬
脂肪酸類F:ベヘン酸、試薬
脂肪酸類G:オレイン酸、試薬
脂肪酸類H:ステアリン酸ナトリウム、試薬
脂肪酸類J:ステアリン酸カリウム、試薬
脂肪酸類K:ステアリン酸カルシウム、試薬
【0019】
<測定方法>
石膏溶解度:20℃恒温室内で、飽和水酸化カルシウム水溶液100mlをマグネットスタラで攪拌しながら、製造した改質石膏4g加え、経過時間毎に分取し、吸引濾過した濾液中の石膏濃度(SO4イオン量をCaSO4量に換算)を高周波誘導結合プラズマ発光分析(ICP)によって測定
【0020】
【表1】
【0021】
表1に示すように、本発明の改質石膏は天然無水石膏の欠点であった石膏溶解度を抑制でき、弗酸副生石膏とほぼ同等の反応性を付与できる。
【0022】
実験例2
脂肪酸類D又は脂肪酸類Hを被覆した改質石膏とCAを表2に示す割合で配合し、本発明のセメント混和材を製造した。
このセメント混和材30部に対して、あらかじめ硬化調整剤をセメント混和材100部に対して2.5部になるように溶解した水を、200部配合して急硬材スラリーを調整した。
一方、水セメント比(W/C)60%に調製したセメントミルク100部に対して、急硬材スラリー100部を混合し、20℃恒温室内で、ゲル化時間とホモゲル強度を測定した。結果を表2に併記する。
【0023】
<使用材料>
セメント :普通ポルトランドセメント、市販品
遅延剤 :市販のクエン酸と炭酸カリウムの等量混合物
【0024】
<測定方法>
ゲル化時間:B型粘度計で粘度を測定し、ゲル化(30cps)に到達するまでの時間ホモゲル強度:型枠に充填して脱型後、ホモゲルの一軸圧縮強度を測定
【0025】
【表2】
【0026】
表2に示すように、本発明のセメント組成物は適度なゲル化時間を要し、強度発現も良好であった。
【0027】
【発明の効果】
本発明の改質石膏を使用すると無水石膏の反応性を制御することができ、これまで使用できなかった天然無水石膏を、セメント系注入材やセメント急硬材などのセメント混和材に、弗酸副生石膏の代替として適用可能となった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a modified gypsum for controlling the gypsum dissolution rate in an aqueous solution by coating the surface of gypsum particles with fatty acids to modify the gypsum, and further comprising the modified gypsum and calcium aluminate. By blending, it can give properties as a cement hardener, and can be used as cement-based injection material for improving soft ground firmly and injection material for pre-receiving method for stabilization of ground during tunnel excavation. The present invention relates to a modified gypsum and a cement admixture using the same.
Further, the parts and% used in the present invention are based on mass unless otherwise specified.
[0002]
[Prior art and its problems]
Conventionally, for the purpose of strengthening soft ground or pre-reinforcing excavated ground, there has been proposed a method of injecting cement milk or mixing and injecting cemented milk with gypsum and calcium aluminate added to cement milk. (JP-A-59-121144).
Particularly recently, hard-cured milk composed mainly of gypsum and calcium aluminate has been used for the purpose of shortening the construction cycle and preventing milk from flowing out during cement injection.
[0003]
On the other hand, most of the gypsum sources in Japan are hemihydrate gypsum and dihydrate gypsum discharged from thermal power plants, etc., and these gypsums have low hydraulic properties and low reaction activity, so they produce anhydrous gypsum suitable for cement rapid hardening materials. There was a supply problem that the amount was small.
In particular, anhydrous gypsum in Japan is mostly by-product gypsum during the production of hydrofluoric acid, which is a raw material for chemical products, and high-quality anhydrous gypsum is poor as a raw material for cement rapid hardening materials.
Under such circumstances, natural anhydrous gypsum produced in large quantities overseas must be used as a source of anhydrous gypsum, but natural anhydrous gypsum is significantly more water-soluble than hydrofluoric acid by-product anhydrous gypsum. When used as a cement hardener, it has a high reactivity with calcium aluminate, and there is a problem that it is difficult to adjust the handling time and gelation time under high temperature construction conditions such as summer.
[0004]
The purpose of the present invention is to adjust the dissolution rate and reaction rate of gypsum and to moderately control the setting rate of cement hardened material mixed with calcium aluminate or the like, specifically in an aqueous solution. The technology is to control natural anhydrous gypsum with a remarkably high dissolution rate and reaction rate in the same way as hydrofluoric acid byproduct gypsum.
[0005]
As a result of various studies to solve the above problems, the present inventor obtained the knowledge that the dissolution rate and reaction rate of gypsum can be controlled by coating the surface of gypsum particles with specific fatty acids, and the present invention has been completed. It came to do.
[0006]
That is, the present invention represents (RCOO) nX (R is a saturated or unsaturated hydrocarbon, n is 1 or 2, X is hydrogen, an alkali metal, or an alkaline earth metal) with respect to 100 parts by mass of gypsum. Is a modified gypsum formed by coating 0.005 to 1.0 part by weight of a fatty acid, wherein the fatty acid is lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and oleic acid or a salt thereof Or the modified gypsum characterized by being two or more, wherein the fatty acids are one or more of the group consisting of palmitic acid, stearic acid, and sodium stearate a reforming gypsum, fatty acids is a reforming gypsum, which is a stearic acid, a cement admixture obtained by mixing the said modified gypsum and calcium aluminate, cement, The A cement composition comprising a cement admixture, and an injection material comprising the cement composition .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be specifically described below.
[0008]
The fatty acids used in the present invention are fatty acids represented by (RCOO) n X (R is a saturated or unsaturated hydrocarbon, n is 1 or 2, X is hydrogen, an alkali metal, or an alkaline earth metal) and / or Or a salt thereof, specifically, a saturated fatty acid such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid, an unsaturated fatty acid such as oleic acid, or a sodium salt thereof, One or two or more of alkali metal salts and alkaline earth metal salts such as potassium salt and calcium salt are blended.
Since fatty acids are difficult to dissolve in water, a water-repellent film is formed on the surface of the gypsum particles, temporarily reducing the hydration activity, so that the initial reaction immediately after mixing with cement concrete can be instantaneously suppressed, and thereafter normal Imparts excellent curing properties.
Fatty acids are made from beef tallow, olive oil, rice bran oil, animal and vegetable fatty oils, etc., and are manufactured through steps such as purification, hardening, decomposition, distillation, fractional distillation, etc. The high-pressure decomposition method and the Toichel decomposition method.
The fatty acids of the present invention can be produced by any of these decomposition methods. In addition, other industrially produced products can also be used, and among these fatty acids, palmitic acid, stearic acid or their salts are safe to handle and have good effects when used as cement admixtures. It is preferable from a certain aspect.
[0009]
The method for coating the surface of gypsum particles with fatty acids is to add fatty acids to the gypsum lump when crushing the gypsum lump, and then mix and crush it with a pulverizer such as a ball mill, rod mill, or roller mill. There are methods such as adding fatty acids to gypsum and mixing with a mixer such as an omni mixer, nauta mixer, V-type mixer, biaxial mixer, and tilting cylinder mixer. To preferred.
The particle size of the fatty acids is not particularly limited when mixed and pulverized, but when stirring and mixing with a mixer such as a mixer, it is preferable to use fine powder having an average particle size of gypsum or less, and 90 μm or less. Is preferable, and 45 μm or less is more preferable. If it exceeds 90 μm, it may not be coated during mixing or the dispersibility may be poor.
The amount of fatty acids to be used is preferably 5 parts or less with respect to 100 parts of gypsum, and when used as a cement admixture, it does not cause a significant decrease in setting or strength, so 0.005-1.0 part is more preferable, 0.01-0.1 Part is most preferred. When the amount of fatty acids used is too large, the dissolution rate of the modified gypsum is reduced, and the reaction activity as a cement admixture may be reduced. In addition, if the amount of fatty acids used is small, the dissolution rate of gypsum will not decrease, and the solubility of natural gypsum cannot be reduced to the level of hydrofluoric acid byproduct gypsum, and it can be used as a cement admixture for cement-based injection materials or cement rapid hardening materials. In this case, the reactivity becomes too high, and problems due to a high gypsum dissolution rate, such as insufficient handling time and gelation time, and reduced strength development, may occur.
Whether the fatty acids of the present invention are added and coated at a predetermined ratio can be measured by a surface analyzer such as EPMA, SEM, ESCA, FT-IR, and GC-MAS.
In addition, after extraction using an organic solvent such as alcohol, ether, chloroform, benzene, petroleum ether, and fatty oil, it can be quantified by organic matter analysis such as gas chromatography after separation and purification.
[0010]
The gypsum used in the present invention is hemihydrate gypsum or anhydrous gypsum, and is reactive gypsum that reacts with cement. In particular, anhydrous gypsum has a high dissolution rate in an aqueous solution, and is preferable as a cement-based injection material, a cement rapid hardening material, or the like.
[0011]
The calcium aluminate (hereinafter referred to as CA) used in the present invention is a CaO obtained by mixing a raw material containing calcia and a raw material containing alumina and performing a heat treatment such as firing in a kiln or melting in an electric furnace. And Al 2 O 3 as main components and a general term for substances having hydration activity, CaO and / or a part of Al 2 O 3 is an alkali metal oxide, alkaline earth metal oxide, silicon oxide, titanium oxide , Iron oxide, alkali metal halides, alkaline earth metal halides, alkali metal sulfates, compounds substituted with alkaline earth metal sulfates, etc., or those containing CaO and Al 2 O 3 as main components, These are substances dissolved in a small amount.
The mineral form may be crystalline or amorphous. Particularly preferred is amorphous CA corresponding to 12CaO · 7Al 2 O 3 , which is obtained by bringing a clinker melted in an electric furnace into contact with compressed air or water and rapidly cooling it.
Fineness specific surface area by Blaine method (hereinafter, referred to as Blaine value) is preferably at least 3,000 cm 2 / g in, 5,000 cm 2 / g or more is more preferable. If the brane value is less than 3,000 cm 2 / g, that is, if the CA particle size is coarse, the reactivity as a cement hardener may decrease, and the initial strength development may also decrease.
It is preferable that impurities such as silicon oxide contained in CA are small, and in particular, magnesium oxide and iron oxide are each preferably 3% or less in order to give harmful properties such as expansibility to the hardened cement. In particular, in the present invention, it is preferable that there are few components excluding CaO and Al 2 O 3 such as silicon oxide, titanium oxide, and iron oxide, and particularly the total amount of silicon oxide, titanium oxide, and iron oxide is 10% or less. Is preferred. If the amount of impurities increases, the hydration activity of CA may decrease.
[0012]
The blending ratio of the modified gypsum and CA is preferably 25 to 75 parts of modified gypsum and 75 to 25 parts of CA, more preferably 40 to 60 parts of modified gypsum and 60 to 40 parts of CA. Outside this range, the gelation time and strength development may be deteriorated when used as a cement-based injection material or cement rapid hardening material.
[0013]
The cement admixture of the present invention can be produced by a method in which the modified gypsum and CA are separately pulverized and mixed with a mixer or the like in a predetermined ratio.
[0014]
Furthermore, in the present invention, AE agent, water reducing agent, in addition to curing regulators such as carbonates, oxycarboxylic acids or their salts, which are usually used for adjusting the setting of cement and adjusting the gelation time as required. Chemical admixtures such as AE water reducing agents, high performance water reducing agents, and high performance AE water reducing agents, and admixtures used in mortar and concrete such as blast furnace slag fine powder, silica fume, fly ash, limestone fine powder, and metakaolin powder. It is possible to mix.
[0015]
Furthermore, the cement admixture of the present invention can be blended with general-purpose separation preventing agents and dust reducing agents for the purpose of improving viscosity during construction and reducing dust.
[0016]
【Example】
Hereinafter, the present invention will be further described based on experimental examples.
[0017]
Experimental example 1
After adjusting the gypsum to a particle size of 5 mm or less, the fatty acids shown in Table 1 are added, and a ball mill is used to produce a modified gypsum by mixing and grinding to a brain value of about 6,000 cm 2 / g. Was measured. The results are also shown in Table 1.
For comparison, the same procedure was performed using anhydrous gypsum having a brain value of 6,000 cm 2 / g pulverized without adding fatty acids. The results are also shown in Table 1.
[0018]
<Materials used>
Plaster α: Thai natural plaster,
Gypsum β: By-product gypsum hydrofluoric acid, commercially available fatty acids A: lauric acid, reagent fatty acids B: myristic acid, reagent fatty acids C: palmitic acid, reagent fatty acids D: stearic acid, reagent fatty acids E: arachidic acid, reagent Fatty acids F: behenic acid, reagent fatty acids G: oleic acid, reagent fatty acids H: sodium stearate, reagent fatty acids J: potassium stearate, reagent fatty acids K: calcium stearate, reagent
<Measurement method>
Gypsum solubility: In a constant temperature room at 20 ° C., 100 g of a saturated calcium hydroxide aqueous solution was stirred with a magnetic stirrer, and 4 g of the modified gypsum produced was added. The gypsum concentration (SO 4 Measure the amount of ions (converted to the amount of CaSO 4 ) by high frequency inductively coupled plasma optical emission spectrometry (ICP).
[Table 1]
[0021]
As shown in Table 1, the modified gypsum of the present invention can suppress the solubility of gypsum, which was a drawback of natural anhydrous gypsum, and can impart almost the same reactivity as hydrofluoric acid byproduct gypsum.
[0022]
Experimental example 2
The cement admixture of the present invention was manufactured by blending modified gypsum coated with fatty acids D or fatty acids H and CA in the proportions shown in Table 2.
To 30 parts of this cement admixture, 200 parts of water in which a curing modifier was dissolved in advance to 2.5 parts with respect to 100 parts of cement admixture was blended to prepare a quick hard material slurry.
On the other hand, 100 parts of cemented carbide slurry was mixed with 100 parts of cement milk prepared at a water cement ratio (W / C) of 60%, and the gelation time and homogel strength were measured in a constant temperature room at 20 ° C. The results are also shown in Table 2.
[0023]
<Materials used>
Cement: Ordinary Portland cement, commercial product retarder: Equivalent mixture of commercially available citric acid and potassium carbonate [0024]
<Measurement method>
Gelation time: Viscosity is measured with a B-type viscometer, and the time until gelation (30 cps) is reached. Homogel strength: uniaxial compressive strength of homogel is measured after filling into a mold and demolding.
[Table 2]
[0026]
As shown in Table 2, the cement composition of the present invention required an appropriate gelation time and exhibited good strength.
[0027]
【The invention's effect】
When the modified gypsum of the present invention is used, the reactivity of anhydrous gypsum can be controlled, and natural anhydrous gypsum that has not been used so far can be used as a cement admixture such as cement-based injecting material or cement quick-hardening material. Applicable as a substitute for by-product gypsum.
Claims (7)
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Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
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JPS5339323A (en) * | 1976-09-24 | 1978-04-11 | Idemitsu Kosan Co | Setup method of modified gypsum |
JPS59121144A (en) * | 1982-12-28 | 1984-07-13 | 日本鉄道建設公団 | Retarder and cement rapid setting process therewith |
JPH06115987A (en) * | 1992-10-05 | 1994-04-26 | Denki Kagaku Kogyo Kk | Cement material |
JPH06127991A (en) * | 1992-10-16 | 1994-05-10 | Denki Kagaku Kogyo Kk | Injection material |
JPH0769698A (en) * | 1992-07-15 | 1995-03-14 | East Japan Railway Co | Quick curing cement bituminous grouting material for railroad and installation thereof |
JPH07144942A (en) * | 1993-11-18 | 1995-06-06 | Ohbayashi Corp | Method for inhibiting hydration reaction of cement by coating |
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Publication number | Priority date | Publication date | Assignee | Title |
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JPS5339323A (en) * | 1976-09-24 | 1978-04-11 | Idemitsu Kosan Co | Setup method of modified gypsum |
JPS59121144A (en) * | 1982-12-28 | 1984-07-13 | 日本鉄道建設公団 | Retarder and cement rapid setting process therewith |
JPH0769698A (en) * | 1992-07-15 | 1995-03-14 | East Japan Railway Co | Quick curing cement bituminous grouting material for railroad and installation thereof |
JPH06115987A (en) * | 1992-10-05 | 1994-04-26 | Denki Kagaku Kogyo Kk | Cement material |
JPH06127991A (en) * | 1992-10-16 | 1994-05-10 | Denki Kagaku Kogyo Kk | Injection material |
JPH07144942A (en) * | 1993-11-18 | 1995-06-06 | Ohbayashi Corp | Method for inhibiting hydration reaction of cement by coating |
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