Japan Concrete InstituteActa Medica Okayama1346-80142252024Freeze-thaw Resistance of Concrete using Ground Granulated Blast-furnace Slag and Blast-furnace Slag Sand in Salt Water253266ENToshikiAyanoFaculty of Environmental, Life, Natural Science and Technology, Okayama UniversityTakashiFujiiFaculty of Environmental, Life, Natural Science and Technology, Okayama UniversityKanakoOkazakiDivision of Social Engineering and Environmental Management, Graduate School of Environmental and Life Science, Okayama UniversityThe freeze-thaw resistance of concrete is significantly lower in salt water than in fresh water. Concrete deteriorates through repeated freezing and thawing, but in salt water, freezing alone leads to destruction. This paper investigated the effect of calcium hydroxide in concrete on the failure of concrete under such low temperatures. Calcium hydroxide precipitates at the transition zone between aggregate and cement paste due to the hydration of cement. The lower the temperature and the higher the concentration of salt water, the more calcium hydroxide dissolves. From concrete, more calcium hydroxide is eluted in salt water than in fresh water. This accelerates the deterioration of mortar and concrete due to freeze-thaw action. Mortar and concrete using ground granulated blast-furnace slag produces less calcium hydroxide. In mortar and concrete using blast-furnace slag sand, calcium hydroxide precipitated around the aggregate reacts with cement paste and blast-furnace slag sand to modify the transition zone. From these results, it was clarified that concrete using blast-furnace slag exhibits high freeze-thaw resistance even in salt water.<br>
This paper is the English translation of the authors’ previous work [Ayano, T., Fujii, T. and Okazaki, K., (2023). “Freeze-thaw resistance of concrete using ground granulated blast-furnace and blast-furnace slag sand in salt water.” Japanese Journal of JSCE, 79(12), 23-00042. (in Japanese)].No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2013Strength and Durability of Concrete with Blast Furnace SlagT4-6 2ENPaweenaJARIYATHITIPONGKazuyoshiHOSOTANITakashiFUJIIToshikiAYANOThe properties of concrete using blast furnace as binder and fine aggregate have been
investigated in this study. The experiments focus on the properties of concrete such as
compressive strength and young's modulus, carbonation, diffusion of chloride ions,
resistance to sulfate attack and resistance to freeze and thaw. The experimental results show
that when blast furnace slag is used in concrete, it improves the durability properties of
concrete. However, the combination of using both blast furnace slag as binder and fine
aggregate shows a greater improvement of those properties of concrete.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2013Effect of chemical admixture on property of fresh mortar using sludge waterW1-7 3ENTakashiFUJIITadashiSAITOToshikiAYANOAddition of sludge water as a part of mixing water had little influence on strength and
durability of hardened concrete, but caused a slump decrease of fresh concrete. The decrease
of slump was improved by addition of a certain set retarder such as gluconate into sludge
water due to control of cement hydration. Some of polymers were also effective in
improvement of slump. However hydration of cement was observed in those cases of
polymers. Therefore it is presumed such the polymers improve slump not by hydration
control effect but by another one.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2013THE SULFURIC ACID RESISTANCE OF CONCRETE WITH BLAST FURNACE SLAG581586ENPaweenaJARIYATHITIPONGKazuyoshiHOSOTANITakashiFUJIIToshikiAYANOThe deterioration of concrete by sulfuric acid attack in sewage environments has become a serious problem. In this
study, it was shown that the resistance to sulfuric acid of mortar and concrete can be improved by using a
blast-furnace slag fine aggregate to the total amount of fine aggregate. When mortar or concrete reacts to sulfuric
acid, dihydrated gypsum film is formed around the particulate of the fine aggregate. This dihydrated gypsum film
could retard the penetration of sulfuric acid, thus improving the resistance to sulfuric acid. However, the resistance
to sulfuric acid depends on the hardness of the dihydrated gypsum film.No potential conflict of interest relevant to this article was reported.日本材料学会Acta Medica Okayama132013コンクリートの耐久性に及ぼす高炉スラグ細骨材の影響16ENTakashiFUJIIPaweenaJARIYATHITIPONGKazuyoshiHOSOTANIToshikiAYANO本研究は，高炉スラグを用いたコンクリートの中性化，耐硫酸塩性および凍結融解
抵抗性の検討を行ったものである．高炉スラグを細骨材に用いることで，細骨材周辺に集
積する水酸化カルシウムがなくなり，骨材表面とペーストとの界面が強固なものとなるた
め，コンクリートの中性化および耐硫酸塩性が向上する．また，結合材の一部を高炉スラ
グ微粉末に置き換えるか，または，細骨材に高炉スラグ細骨材を用いたコンクリートでは，
AE 剤を用いることなく，また，蒸気養生を行っても，十分な凍結融解抵抗性が得られる．No potential conflict of interest relevant to this article was reported.岡山大学環境理工学部Acta Medica Okayama1341-9099612001Influence of Coarse Aggregate on the Shrinkage of Normal and High-Strength Concretes4145ENKenjiSakataToshikiAyano10.18926/fest/11529Inclusion of aggregates leads to a reduction in drying shrinkage of cement paste. This is due to the elastic deformation of the aggregates that partly restrains the shrinkage deformation of cement paste. Hence, concrete with higher aggregate content exhibits smaller shrinkage. In addition, concrete with aggregates of higher modulus of elasticity or of rougher surfaces is more resistant to shrinkage process. In this paper the effects of the type of coarse aggregate on the shrinkage of normal and high-strength concretes are investigated. Two different types of crushed stone were used as coarse aggregates to produce the concrete mixtures used in this study. For each coarse aggregate type, two normal-strength concrete (NSC) mixtures and two high-strength concrete (HSC) mixtures were prepared. The 28-day compressive strength values of NSC mixtures were about 35 and 50 MPa, while those of HSC mixtures were 70 and 100 MPa, respectively. All shrinkage specimens were cured in water for 14 days after casting, then exposed to drying under the conditions of constant temperature (20℃) and relative humidity (60%). It has been shown that the type of the coarse aggregate influences shrinkage behaviour of both normal and high-strength concretes.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama1993コンクリートの乾燥収縮およびクリープの予測とその設計への適用に関する研究ENコンクリー卜構造物において、クリープや乾燥収縮等の時間に依存する変形挙動は、コンクリートのたわみやひびわれに重大な影響を及ぼす。従って、コンクリート構造の限界状態設計法においては、コンクリー卜の強度特性のみならず、変形特性をも正しく把握する必要があるとされている。すなわち、クリープや乾燥収縮等の時間に依存する変形挙動を正しく理解しておくことが、コンクリート構造物の使用性の検討上のきわめて重要な要件となる。また、プレストレス卜コンクリート構造物においてはクリープひずみおよび乾燥収縮ひずみが、プレストレスト力減退の原因となるため、その適切な予測が設計上の要諦となる。しかし、設計に用いるクリープひずみまたは乾燥収縮ひずみは、原則として、実験によって求めなければならず、多大な時間， 労力および経費を費やす。従って、これら時間に依存するひずみの影響を設計において考慮するために、複雑なクリープ問題を簡単化した手法に頼らざるをえないのが現状である。本研究は、一定持続応力下におけるコンクリートのクリープ予測式および乾燥収縮ひずみ予測式の確立と変動応力下におけるクリープひずみの解析手法を確立することを目的とし、その設計への適用性を検討するものである。No potential conflict of interest relevant to this article was reported.