JP2007230806A - Frost damage resistant lightweight concrete - Google Patents
Frost damage resistant lightweight concrete Download PDFInfo
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- JP2007230806A JP2007230806A JP2006052489A JP2006052489A JP2007230806A JP 2007230806 A JP2007230806 A JP 2007230806A JP 2006052489 A JP2006052489 A JP 2006052489A JP 2006052489 A JP2006052489 A JP 2006052489A JP 2007230806 A JP2007230806 A JP 2007230806A
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/20—Resistance against chemical, physical or biological attack
- C04B2111/29—Frost-thaw resistance
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/40—Porous or lightweight materials
Abstract
Description
本発明は耐凍害軽量コンクリートに関し、さらに詳しくは、人工軽量骨材等を用いたコンクリート製品の凍結融解抵抗性を向上させる技術に係るものである。 The present invention relates to a frost-resistant lightweight concrete, and more particularly to a technique for improving the freeze-thaw resistance of a concrete product using an artificial lightweight aggregate or the like.
例えば、経年劣化した鋼橋ＲＣ床板打換えに、幅員拡張や活荷重増加による断面増加に伴って上部工の重量が増加する。この重量の増加を小さくするため、掛け替え部に軽量コンクリートを適用することは非常に有効な手段の一つと考えられる。 For example, the weight of the superstructure increases as the cross-section increases due to the expansion of the width or the increase of the live load due to the steel bridge RC floor board replacement over time. In order to reduce this increase in weight, it is considered to be one of the very effective means to apply lightweight concrete to the switching portion.
しかし、軽量コンクリートは、一般に、軽量粗骨材の吸水率が大きいため、軽量粗骨材中に含有する水分が、環境温度の低いときは膨張し、軽量粗骨材の周囲にひび割れを生じさせ、結果的にポップアウトを引き起こすため、一般に、耐凍害性が低いことが知られている。従って、寒冷地で使用する場合に大きな問題となる場合がある。 However, since lightweight concrete generally has a large water absorption rate for lightweight coarse aggregates, the moisture contained in the lightweight coarse aggregates expands when the ambient temperature is low, causing cracks around the lightweight coarse aggregates. As a result, pop-out is caused, and it is generally known that the resistance to frost damage is low. Therefore, it may become a big problem when used in a cold region.
この問題を解決するために、軽量粗骨材の低吸水率化を図る技術、独立気泡を有する軽量骨材の開発、あるいは軽量骨材自体の表面にコーティングを施して吸水を防止する技術などが提案されている。しかし、このような品質を向上させた軽量粗骨材においても、同一バッチにおけるコンクリート中の品質のばらつき等に起因する耐凍害性の低下が懸念される。このため、良質で、かつ、ばらつきの小さい軽量粗骨材の選定方法や耐凍害性低下を抑制するためのコンクリートの補強方法が必要となる。 In order to solve this problem, there are technologies to reduce the water absorption rate of lightweight coarse aggregate, development of lightweight aggregate with closed cells, or technology to prevent water absorption by coating the surface of lightweight aggregate itself Proposed. However, even in such a lightweight coarse aggregate with improved quality, there is a concern that the frost damage resistance may be reduced due to variations in quality in concrete in the same batch. For this reason, it is necessary to select a lightweight coarse aggregate that is of high quality and has little variation, and a concrete reinforcing method for suppressing the frost damage resistance deterioration.
このような課題を解決する技術として、コンクリート中に鋼短繊維を混入したコンクリートが知られている。しかし、この技術では、鋼繊維の腐食により、美観上問題が生じたり、長期耐久性が劣るという問題があった。 As a technique for solving such a problem, concrete in which short steel fibers are mixed in concrete is known. However, this technique has a problem that an aesthetic problem arises due to the corrosion of the steel fiber, and the long-term durability is inferior.
また、１０００℃以上の耐火性能及び耐熱性能を保つコンクリートとして、絶乾状態又は半分程度まで吸水させた軽量骨材を用い、ポリビニールアルコール系繊維等を用いた水硬性複合物（コンクリート）がある（例えば、特許文献１参照。）。 Moreover, there is a hydraulic composite (concrete) using a polyvinyl alcohol fiber or the like using a lightweight aggregate that has absorbed water up to about half or half as a concrete that maintains a fire resistance performance and heat resistance performance of 1000 ° C. or higher. (For example, refer to Patent Document 1).
この技術は高温におけるコンクリートの爆裂防止に関する技術である。
軽量粗骨材を使用した軽量コンクリートは、軽量粗骨材に含まれている水の凍結融解の繰り返しにより軽量粗骨材のポップアウトやコンクリートのひび割れにより劣化するという問題がある。 There is a problem that lightweight concrete using lightweight coarse aggregate deteriorates due to pop-out of lightweight coarse aggregate or cracks in concrete due to repeated freezing and thawing of water contained in the lightweight coarse aggregate.
本発明はこのような問題を解決し、耐凍害軽量コンクリートを提供することを目的とする。 An object of the present invention is to solve such problems and to provide frost-resistant lightweight concrete.
本発明は、ポリビニールアルコール繊維（以下ＰＶＡ繊維という）を混入したことを特徴とする耐凍害軽量コンクリートである。 The present invention is a frost-resistant lightweight concrete in which polyvinyl alcohol fibers (hereinafter referred to as PVA fibers) are mixed.
本発明の作用は、軽量コンクリートの凍結融解による膨張収縮に対して、ポリビニールアルコール系繊維を混入することによってコンクリートの靭性が向上し、コンクリートにひび割れ等の発生を抑制することである。この場合、前記ＰＶＡ繊維は繊維径１００〜２００μｍ、繊維長５〜３０ｍｍ、混入量がコンクリート体積の０．１０〜０．２０％とすると好適である。 The effect | action of this invention is that the toughness of concrete improves by mixing a polyvinyl alcohol fiber with respect to the expansion / contraction by freezing and thawing of lightweight concrete, and suppresses generation | occurrence | production of a crack etc. in concrete. In this case, it is preferable that the PVA fiber has a fiber diameter of 100 to 200 μm, a fiber length of 5 to 30 mm, and a mixing amount of 0.10 to 0.20% of the concrete volume.
ＰＶＡ繊維の径を１００〜２００μｍとしたのは、１００μｍ未満では繊維のからまりや凝集を生じやすく補強効果が少なく、２００μｍを越えると繊維のコンクリートとの付着性が不十分となり、凍結防止の効果が小さくなるからである。 The reason why the diameter of the PVA fiber is set to 100 to 200 μm is that if it is less than 100 μm, the fiber is likely to be tangled or aggregated, and the reinforcing effect is small, and if it exceeds 200 μm, the adhesion of the fiber to the concrete becomes insufficient and the effect of preventing freezing is obtained. This is because it becomes smaller.
また、ＰＶＡ繊維の長さを５〜３０ｍｍとしたのは、５ｍｍ未満のような短繊維ではコンクリートの結合力を高める効果が少なく、一方、３０ｍｍを越えると、コンクリート中への分散性が劣るので３０ｍｍ以下とした。 Moreover, the length of the PVA fiber is set to 5 to 30 mm because short fibers such as less than 5 mm have little effect of increasing the binding strength of the concrete. On the other hand, if the length exceeds 30 mm, the dispersibility in the concrete is inferior. It was 30 mm or less.
またＰＶＡ繊維の混入量はコンクリート体積の０．１０〜０．２０％とするのがよい。０．１０％より少ないと結合材としての付着の効果が不足し、０．２０％を上廻って添加してもコンクリートの靱性向上効果が飽和するので、この範囲内とするのがよい。 The amount of PVA fibers mixed is preferably 0.10 to 0.20% of the concrete volume. If it is less than 0.10%, the effect of adhesion as a binder is insufficient, and even if added over 0.20%, the effect of improving the toughness of the concrete is saturated.
本発明によれば、通常の人工軽量粗骨材を用い、混練、製造した軽量コンクリートにおける耐凍害性が大幅に向上し、寒冷地等における軽量コンクリートの使用に著しく貢献するという優れた効果を奏する。 According to the present invention, frost damage resistance in light-weight concrete kneaded and manufactured using ordinary artificial lightweight coarse aggregate is greatly improved, and an excellent effect of significantly contributing to the use of light-weight concrete in cold regions and the like is achieved. .
本発明では、耐凍害性を向上させるために、ＰＶＡ繊維を混入して軽量コンクリートを補強する。ＰＶＡ繊維は繊維径１００〜２００μｍ、繊維長１０〜２０ｍｍの繊維とし、この繊維をコンクリート体積の０．１０〜０．２％を混入することが望ましい。 In the present invention, in order to improve the frost damage resistance, PVA fibers are mixed to reinforce the lightweight concrete. The PVA fiber is preferably a fiber having a fiber diameter of 100 to 200 μm and a fiber length of 10 to 20 mm, and this fiber is desirably mixed with 0.10 to 0.2% of the concrete volume.
本発明を実施するための最良の形態について、試験を行ったので以下説明する。 The best mode for carrying out the present invention was tested and will be described below.
良質で、かつ、ばらつきの小さい軽量粗骨材を選別するために軽量粗骨材の破砕試験を行い、破砕試験後の吸水率試験結果を得た。この試験により選別した軽量粗骨材を用いてＰＶＡ繊維で補強したコンクリートを製造し、その凍結融解試験を行った。 In order to select lightweight coarse aggregates with good quality and small variations, a lightweight coarse aggregate crushing test was performed, and water absorption test results after the crushing test were obtained. Concrete reinforced with PVA fibers was produced using the lightweight coarse aggregate selected by this test, and the freeze-thaw test was performed.
なお、プレキャスト部材として用いることを想定して、製品と同一の軽量コンクリートについて蒸気養生の有無を実験要因として取り上げた。
（Ａ）軽量粗骨材の基礎物性試験について
(Ａ−１)基礎物性試験
４種類の軽量粗骨材について、密度、吸水率、浮粒率、破砕試験および破砕試験後の吸水率試験を実施した。
Assuming that it is used as a precast member, the presence or absence of steam curing was taken up as an experimental factor for the same lightweight concrete as the product.
(A) Basic physical property test of lightweight coarse aggregate
(A-1) Basic physical property test About four types of lightweight coarse aggregates, a density, a water absorption rate, a floating rate, a crushing test, and a water absorption rate test after the crushing test were carried out.
密度及び吸水率試験は、ＪＩＳ Ａ １１００に準拠して実施した。 The density and water absorption rate tests were performed according to JIS A 1100.
浮粒率試験は、ＪＩＳ Ａ １１４３に準拠して行った。まず、試料を２４時間乾燥させ、約２リットルの質量を計り、十分大きなポリエチレン製のバケツに入れ、よく攪拌した。注水してから１０分後、水に浮いている粒を採取し、採取した粒を２４時間乾燥した後に質量を計量して浮粒率を算定した。 The floating rate test was performed according to JIS A 1143. First, the sample was dried for 24 hours, weighed about 2 liters, placed in a sufficiently large polyethylene bucket, and stirred well. Ten minutes after water injection, the particles floating in the water were collected, the collected particles were dried for 24 hours, and the mass was measured to calculate the floating particle ratio.
軽量粗骨材の破砕試験は、ＢＳ８１２に準拠して行った。プランジャーを毎分４０ｋＮで載荷し、４００ｋＮまで加えた後に除荷した。その後に２．５ｍｍふるいを用いてこれを通過する質量を求め、破砕値を算出した。破砕試験後の吸水率試験の試料は２．５ｍｍふるいに残留したものを用いて実施した。
(Ａ−２)基礎物性試験結果
軽量粗骨材の試験結果を表１に示す。
The crushing test of the lightweight coarse aggregate was performed according to BS812. The plunger was loaded at 40 kN per minute and unloaded after adding up to 400 kN. Thereafter, the mass passing through this was determined using a 2.5 mm sieve, and the crushing value was calculated. The sample of the water absorption rate test after the crushing test was carried out using what remained on the 2.5 mm sieve.
(A-2) Basic physical property test results Table 1 shows the light coarse aggregate test results.
表乾密度は軽量粗骨材Ａ，ＢおよびＣはほぼ等しく、軽量粗骨材Ｄはこれらより小さかった。破砕試験前の吸水率は軽量粗骨材Ｄが一番小さく、ＡおよびＣはそれより大きかった。軽量粗骨材の密度は１．０ｇ／ｃｍ３以上であることから、浮粒率の大きい軽量粗骨材ほど同一ロッドでの不良骨材の混入量が多く含むものと考えられる。この試験では軽量粗骨材Ａの浮粒率が最も小さく、Ｃの浮粒率が最も大きかった。 As for the surface dry density, the light coarse aggregates A, B and C were almost equal, and the light coarse aggregate D was smaller than these. The water absorption before the crushing test was the smallest for the light coarse aggregate D, and A and C were larger. Since the density of the light coarse aggregate is 1.0 g / cm 3 or more, it is considered that the light coarse aggregate having a larger floating particle ratio includes a larger amount of defective aggregate in the same rod. In this test, the lightweight coarse aggregate A had the lowest floating particle ratio, and C had the largest floating particle ratio.
破砕試験後の吸水率は破砕により粒子表面にひび割れ等の損傷を受けた軽量粗骨材の試験結果であり、試験前の吸水率との差が小さい場合にはポップアウトやコンクリートのひび割れ発生による劣化に対して有利であると考えられる。 The water absorption rate after the crushing test is a test result of lightweight coarse aggregate that has been damaged such as cracks on the particle surface due to crushing. If the difference from the water absorption rate before the test is small, it may be caused by pop-out or cracking of concrete. It is considered advantageous for deterioration.
以上の観点から、試験結果が良好な軽量粗骨材Ａを用いた場合についてコンクリートの圧縮強度、ヤング係数および凍結融解試験をそれぞれ実施した。また、比較のため、品質のばらつきがあると考えられる軽量粗骨材Ｄを用いた場合について圧縮強度と凍結融解試験を実施した。 From the above viewpoint, the compressive strength, Young's modulus, and freeze-thaw test of concrete were carried out for each case where the light weight coarse aggregate A with good test results was used. For comparison, the compression strength and the freeze-thaw test were conducted for the case of using the light coarse aggregate D, which is considered to have quality variations.
（Ｂ）硬化コンクリートの試験
（Ｂ−１）使用材料および配合
表２に使用材料及び配合表を示す。
(B) Hardened concrete test (B-1) Materials used and formulation Table 2 shows the materials used and the formulation table.
結合材βには早強ポルトランドセメントＨ（密度３．１４ｇ／ｃｍ３，比表面積４４８０ｃｍ２／ｇ）と高炉スラグ微粉末ＢＦＳ（密度２．８８ｇ／ｃｍ３，比表面積６２２０ｃｍ２／ｇ）を、繊維ＰＶＡには、繊維径１００μｍ，繊維長１２ｍｍ，密度１．３０ｇ／ｃｍ３のＰＶＡ繊維をそれぞれ使用した。前述の表１と同じ品質の軽量粗骨材Ａ，Ｄを使用した。なお、空気量測定に必要な骨材修正係数は軽量粗骨材Ａでは２．２％、軽量粗骨材Ｄでは０．３％であった。 High-early-strength The binder β Portland cement H (density 3.14 g / cm 3, a specific surface area of 4480cm 2 / g) and ground granulated blast furnace slag BFS (density 2.88 g / cm 3, a specific surface area of 6220cm 2 / g) and, As the fiber PVA, PVA fibers having a fiber diameter of 100 μm, a fiber length of 12 mm, and a density of 1.30 g / cm 3 were used. Lightweight coarse aggregates A and D having the same quality as in Table 1 were used. It should be noted that the aggregate correction coefficient required for air volume measurement was 2.2% for the light coarse aggregate A and 0.3% for the light coarse aggregate D.
配合Ａは軽量粗骨材Ａを使用した軽量コンクリート、配合Ａ−ＰＶＡと配合Ｄ−ＰＶＡは、それぞれ軽量粗骨材ＡとＤを使用したＰＶＡ繊維補強軽量コンクリートである。各配合の単位容積質量は１８８０ｋｇ／ｍ３とした。ＰＶＡ繊維の混入量はコンクリート１ｍ３あたり１．９５ｋｇ（０．１５容積％）とした。軽量粗骨材Ｄは絶乾状態として使用し、単位水量に３０分吸水率０．３９％にあたる水量１ｋｇ／ｍ３を補正水として加えた。 Blend A is a lightweight concrete using lightweight coarse aggregate A, and blends A-PVA and D-PVA are PVA fiber reinforced lightweight concrete using lightweight coarse aggregates A and D, respectively. The unit volume mass of each formulation was 1880 kg / m 3 . The amount of PVA fibers mixed was 1.95 kg (0.15% by volume) per 1 m 3 of concrete. The light coarse aggregate D was used in an absolutely dry state, and a water amount of 1 kg / m 3 corresponding to a water absorption rate of 0.39% for 30 minutes was added to the unit water amount as correction water.
（Ｂ−２）供試体種別および養生方法
供試体種別と養生方法を表３に示す。供試体寸法は、圧縮強度試験とヤング係数試験ではφ１００×２００ｍｍとし、凍結融解試験では１００×１００×４００ｍｍとした。各試験の供試体本数は３本とした。供試体の養生方法を以下の２種類とした。
(B-2) Specimen type and curing method Table 3 shows the specimen type and the curing method. The specimen dimensions were set to φ100 × 200 mm in the compressive strength test and Young's modulus test, and 100 × 100 × 400 mm in the freeze-thaw test. The number of specimens for each test was three. The following two types of specimen curing methods were used.
１）室内でコンクリート打設後、材齢１日まで室内養生し、その後脱型し、所定の試験材齢まで水中養生した供試体（水中養生）
２）コンクリート打設後、蒸気養生を行い、その後脱型し、所定の試験材齢まで水中養生した供試体（蒸気＋水中養生）
1) Specimen (underwater curing) after concrete placement in the room, indoor curing until the age of 1 day, then demolding and underwater curing to the specified test material age
2) Specimen that was steam-cured after placing the concrete, then removed from the mold, and cured under water until the specified test material age (steam + water curing)
（Ｂ−３）圧縮強度とヤング係数試験および凍結融解試験
圧縮強度とヤング係数試験は、それぞれ、ＪＩＳ Ａ １１０８及びＪＩＳ Ａ １１４９に準拠して実施した。
(B-3) Compressive strength, Young's modulus test and freeze-thaw test The compressive strength and Young's modulus test were carried out in accordance with JIS A 1108 and JIS A 1149, respectively.
凍結融解試験は水中凍結融解試験方法であるＪＩＳ Ａ １１４８［Ａ法］に準拠し、材齢１４日から実施した。試験の終了は３００サイクルとし、それまでに相対動弾性係数が６０％となった場合や破断した場合は、そのサイクルで終了とした。
（Ｃ）試験結果
（Ｃ−１）圧縮強度およびヤング係数
コンクリートの材齢と圧縮強度の関係を図２に、軽量粗骨材Ａを用いたコンクリートの圧縮強度とヤング係数の関係を図３にそれぞれ示す。図中Ａ、Ａ−ＰＵＡ等は表２に示す配合名を示すものである。
The freeze-thaw test was carried out from the age of 14 days in accordance with JIS A 1148 [Method A], which is an underwater freeze-thaw test method. The test was completed for 300 cycles, and when the relative kinematic modulus reached 60% or when it broke, the cycle was completed.
(C) Test results (C-1) Compressive strength and Young's modulus Fig. 2 shows the relationship between concrete age and compressive strength, and Fig. 3 shows the relationship between compressive strength and Young's modulus of concrete using lightweight coarse aggregate A. Each is shown. In the figure, A, A-PUA, etc. indicate the formulation names shown in Table 2.
凍結融解試験開始材齢での圧縮強度は、配合Ａで６３Ｎ／ｍｍ２、配合Ａ−ＰＶＡでは蒸気養生の実施有無によらず約６５Ｎ／ｍｍ２となり、配合Ｄ−ＰＶＡで蒸気養生した供試体は７０Ｎ／ｍｍ２であった。配合Ａ−ＰＶＡで蒸気養生を実施した圧縮強度は材齢１日で約４５Ｎ／ｍｍ２となっていることから、導入時強度３５Ｎ／ｍｍ２、設計基準強度５０Ｎ／ｍｍ２のプレテンション部材にも十分適用することができる。 Compressive strength of freeze-thaw test start material age, 63N / mm 2 in formulation A, about 65N / mm 2 next regardless of whether or not to perform the in steam curing formulations A-PVA, specimens were steam curing in formulation D-PVA Was 70 N / mm 2 . Compressive strength was carried out steam curing in formulation A-PVA from it is about 45N / mm 2 in one day the age, introduced during strength 35N / mm 2, the pretensioning member design strength 50 N / mm 2 Can be applied well.
ヤング係数は圧縮強度６０Ｎ／ｍｍ２において２４ｋＮ／ｍｍ２を超える結果となった。ヤング係数Ｅ（ｋＮ／ｍｍ２）と圧縮強度σ（Ｎ／ｍｍ２）と単位容積質量γ（ｇ／ｃｍ３）との関係について、下記式（１）の関数関係が提案されている。（日本建築学会：鉄筋コンクリート構造計算基準・同解説）
Ｅ＝３３．５ｘ（γ／２．４）２×（σ／６０）１／３……（１）
図３にはγを１．８８ｇ／ｃｍ３とした場合の計算結果もあわせて示した。ヤング係数の実験結果は上記式（１）を用いて算出したヤング係数より大きくなり、この試験で使用した軽量粗骨材Ａの場合には上記式（１）の約１．１７倍となった。
（Ｃ−２）凍結融解試験結果
表３に繊維補強の有無による凍結融解試験における劣化状況を併せて示した。ＰＶＡ繊維補強を実施していない供試体はポップアウトに起因すると思われる剥落部分が多く発生し、かつ、破断している。ＰＶＡ繊維補強を行った供試体はほとんど劣化を生じない結果となった。
The Young's modulus exceeded 24 kN / mm 2 at a compressive strength of 60 N / mm 2 . As for the relationship among the Young's modulus E (kN / mm 2 ), the compressive strength σ (N / mm 2 ), and the unit volume mass γ (g / cm 3 ), a functional relationship of the following formula (1) has been proposed. (The Architectural Institute of Japan: Reinforced concrete structure calculation standards and explanation)
E = 33.5x (γ / 2.4) 2 × (σ / 60) 1/3 (1)
FIG. 3 also shows the calculation results when γ is 1.88 g / cm 3 . The experimental result of the Young's modulus is larger than the Young's modulus calculated using the above formula (1), and in the case of the lightweight coarse aggregate A used in this test, it is about 1.17 times that of the above formula (1). .
(C-2) Results of freeze-thaw test Table 3 also shows the deterioration status in the freeze-thaw test with and without fiber reinforcement. A specimen not subjected to PVA fiber reinforcement has a lot of peeled portions that are thought to be caused by pop-out and is broken. The specimen subjected to PVA fiber reinforcement almost did not deteriorate.
図１にサイクル数に伴う相対動弾性係数の変化を供試体３本の平均値として示す。配合Ａと配合Ａ−ＰＶＡの蒸気養生を実施しない供試体とを比較すると、配合Ａはサイクル数２５０回において相対動弾性係数が８０％を下回る結果となったのに対して、配合Ａ−ＰＶＡはサイクル数３００回においても相対動弾性係数の低下はほとんど認められない結果を示した。 FIG. 1 shows the change in the relative dynamic elastic modulus with the number of cycles as an average value of three specimens. Comparing Formulation A with a specimen that was not subjected to steam curing of Formulation A-PVA, Formulation A resulted in a relative kinematic modulus of less than 80% at 250 cycles, whereas Formulation A-PVA Shows a result that almost no decrease in the relative dynamic elastic modulus was observed even at 300 cycles.
相対的に良質な軽量粗骨材を選別した場合においても水中凍結融解試験の場合にはコンクリートの劣化が認められたが、ＰＶＡ繊維で補強することにより凍結融解抵抗性の向上が認められた。配合Ａではわずかに混入した品質の劣る軽量粗骨材粒子の寸法の大きいポップアウト発生後に、そこに残留した軽量粗骨材粒子の吸水と凍結融解による膨張収縮の繰り返しによりモルタル部のひび割れが急激に発生し、破断した。 Even in the case of selecting relatively high-quality lightweight coarse aggregate, deterioration of concrete was observed in the case of the underwater freeze-thaw test, but improvement in freeze-thaw resistance was recognized by reinforcing with PVA fibers. In compound A, after the occurrence of pop-out with a small size of light coarse aggregate particles of poor quality mixed slightly, the cracks of the mortar part suddenly cracked due to repeated water absorption and freezing and thawing of the remaining light coarse aggregate particles. Occurred and broke.
これに対して、配合Ａ−ＰＶＡはＰＶＡ繊維を混入することにより、ポップアウトの発生数が少なく、ポップアウトが発生した場合でも寸法が小さく、繊維を混入しない場合と比較してひび割れ幅をかなり抑制することができ、結果として相対動弾性係数の低下を小さくすることができたと考えられる。 On the other hand, the blend A-PVA has a small number of pop-outs by mixing PVA fibers, the size is small even when pop-outs occur, and the crack width is considerably smaller than when no fibers are mixed. It can be suppressed, and as a result, it is considered that the decrease in the relative dynamic elastic modulus could be reduced.
蒸気養生を実施した供試体においても、相対動弾性係数の低下がほとんど認められない結果となり、蒸気養生による耐凍結融解抵抗性の低下は認められなかった。軽量粗骨材の物性試験で軽量粗骨材個々の品質にばらつきがあると考えられた配合Ｄ−ＰＶＡについては、ＰＶＡを混入した場合においてもサイクル数２３２回で破断する結果となった。 In the specimens subjected to steam curing, the relative kinematic modulus was hardly decreased, and the resistance to freezing and thawing due to steam curing was not observed. The blended D-PVA, which was considered to have variations in the quality of each lightweight coarse aggregate in the physical property test of the lightweight coarse aggregate, resulted in rupture at 232 cycles even when PVA was mixed.
凍結融解作用によるコンクリートの劣化を防止するためには、繊維補強するのみならず、軽量粗骨材粒子個々の品質のばらつきが小さい軽量粗骨材を選定する必要があると考えられる。このために、浮粒率試験や破砕試験後の吸水率試験は有効である。 In order to prevent deterioration of the concrete due to the freeze-thaw action, it is considered necessary to select not only fiber reinforcement but also lightweight coarse aggregate with small variations in the quality of individual lightweight coarse aggregate particles. For this reason, the floatability test and the water absorption test after the crushing test are effective.
ＰＶＡ繊維補強軽量コンクリートの凍結融解抵抗性試験、破砕試験後の吸水率試験および圧縮強度試験から以下のことが明らかになった。
（１）良質で、かつ、ばらつきの小さい軽量コンクリートをＰＶＡ繊維で補強することにより、水中養生および蒸気養生において、サイクル数３００回においても相対動弾性係数の低下が認められず、凍結融解抵抗性の向上が認められた。
（２）しかし、軽量粗骨材粒子個々の品質のばらつきが耐凍害性に与える影響が大きく、品質のばらつきが大きい場合には、ＰＶＡ繊維補強してもコンクリートの劣化が認められた。
（３）軽量粗骨材粒子個々の品質のばらつきを判定する試験として、浮粒率試験、破砕試験および破砕試験前後における吸水率の差が有効な手法であることが認められた。
（４）本試験で実施した配合Ａ−ＰＶＡは力学的には導入時強度３５Ｎ／ｍｍ２、設計基準強度５０Ｎ／ｍｍ２とする工場製作のプレテンション部材にも適用することができる。
（５）ヤング係数は単位容積質量と圧縮強度の関数で示すことができる。
From the freeze-thaw resistance test, the water absorption test after the crushing test, and the compressive strength test of the light-weight concrete reinforced with PVA fiber, the following was revealed.
(1) Reinforcement of lightweight concrete with good quality and small variation with PVA fibers, no decrease in relative dynamic elastic modulus was observed even under 300 cycles in water curing and steam curing, and resistance to freezing and thawing Improvement was observed.
(2) However, the variation in the quality of the individual lightweight coarse aggregate particles has a great influence on the frost damage resistance. When the variation in the quality is large, deterioration of the concrete was recognized even if the PVA fiber was reinforced.
(3) It was recognized that the difference in water absorption before and after the flocculation rate test, the crushing test, and the crushing test is an effective technique as a test for judging the quality variation of the individual lightweight coarse aggregate particles.
(4) blending A-PVA was conducted in this study is the mechanical introduction strength at 35N / mm 2, it can also be applied to a pre-tensioning member factory fabrication and design strength 50 N / mm 2.
(5) Young's modulus can be expressed as a function of unit volume mass and compressive strength.
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| JPH11268973A (en) * | 1998-01-09 | 1999-10-05 | Diamond Engineering Kk | Fiber-reinforced lightweight concrete |
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| JP2001253749A (en) * | 2000-03-08 | 2001-09-18 | Taiheiyo Cement Corp | High-strength light weight cement hardened body |
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