- 著者
- Ahmad N. Mohammed Megat Azmi Megat Johari Abdullah M. Zeyad Bassam A. Tayeh Moruf O. Yusuf
- 出版者
- Japan Concrete Institute
- 雑誌
- Journal of Advanced Concrete Technology (ISSN:13473913)
- 巻号頁・発行日
- vol.12, no.4, pp.127-137, 2014-04-24 (Released:2014-04-24)
- 参考文献数
- 34
- 被引用文献数
- 7 72
Ground treated ultrafine-POFA obtained from palm oil industry was heat-treated to remove excess carbon. The varied proportion (17%, 30% and 40%) of UPOFA was incorporated into the ultra-high strength concrete (UHSC) to study its effects on the UPOFA-UHSC (Ux-UHSC) in comparison with OPC-UHSC (U0-UHSC) engineering and transport properties. The Ux-UHSC has an increasing workability tendency with a retarded setting times as compared to U0-UHSC. Besides, Ux-UHSC registered higher compressive strength than the U0-UHSC. The 90-d strength of 156 MPa was achieved in U17-UHSC which was 4.7%, 7.5% and 12.2% higher than the values obtained for U30-UHSC, U40-UHSC and U0-UHSC, respectively. The U40-UHSC exhibited the greatest improvement at 90 days in transport properties such as porosity, water absorption, initial surface absorption, rapid chloride permeability, gas permeability and water permeability while the highest strength was recorded with U17-UHSC. Thus, the pozzolanic UPOFA is capable of improving the engineering and transport properties of UHSC.
- 著者
- Ivan Sandi Darma Takafumi Sugiyama Michael Angelo B. Promentilla
- 出版者
- 公益社団法人 日本コンクリート工学会
- 雑誌
- Journal of Advanced Concrete Technology (ISSN:13473913)
- 巻号頁・発行日
- vol.11, no.10, pp.266-281, 2013-10-09 (Released:2013-10-09)
- 参考文献数
- 35
- 被引用文献数
- 10 53
This paper demonstrates the application of microfocus X-ray computed tomography (CT) to study solute transport in cracked concrete. Cracks in a cylindrical specimen of ordinary Portland cement (OPC) and fly ash mortar were induced using a splitting tensile test. Cesium Carbonate (Cs2CO3) was then used as a tracer in the in-situ diffusion test with the aid of X-ray CT. Image analysis was also employed to measure the 3D crack geometry and tracer diffusivity from these CT images. The geometric tortuosity of the crack was approximately 1.25 irrespective of the crack opening width and whether fly ash was added or not. On the other hand the constrictivity increased for the fly ash mortar having roughly the equivalent crack opening width. The measured diffusivity in the crack was controlled by both crack opening width and constrictivity. Results obtained from microtomographic images suggest that the entire crack space may not always be filled with the tracer. The diffusive transport of solute in cracks thus can be restricted from microstructure’s point of view. Smaller crack opening would increase such restricted diffusion. Indications also suggest that the addition of fly ash would lead to the reduction of diffusivity through uncracked body of the mortar.
- 著者
- Johann Plank Bernhard Sachsenhauser
- 出版者
- 公益社団法人 日本コンクリート工学会
- 雑誌
- Journal of Advanced Concrete Technology (ISSN:13473913)
- 巻号頁・発行日
- vol.4, no.2, pp.233-239, 2006 (Released:2006-06-30)
- 参考文献数
- 15
- 被引用文献数
- 32 106
α-Allyl-ω-methoxypolyethylene glycol - maleic anhydride copolymers were synthesized with side chain lengths nEO from 0-130 and characterized by aqueous GPC. A representation of their molecular conformation (e.g. worm-, brush- or star-like polymers) was developed. The amount of polymer adsorbed on cement rapidly decreases with increasing side chain length nEO. Zeta potential measurements using the electroacoustic method in cement paste with w/c = 0.5 indicate that worm-like copolymers with nEO ≤ 7 adsorb flat (“train” type) and form a densely packed, thin polymer film. In this case, the adsorbed amount of copolymer is high. For star polymers with nEO ≥ 34, preferred orientation of the polymer main chain is perpendicular to the cement surface (“tail” type). The result is a thick polymer layer, with a second electrochemical double layer on top. For star polymers, the adsorbed amount is low because of the higher surface occupancy of horizontally layered side groups.
- 著者
- Sakai Etsuo Yamada Kazuo Ohta Akira
- 出版者
- Japan Concrete Institute
- 雑誌
- Journal of Advanced Concrete Technology (ISSN:13468014)
- 巻号頁・発行日
- vol.1, no.1, pp.16-25, 2003
- 被引用文献数
- 4 160
This paper summarizes the relation between the molecular structure and the dispersion-adsorption mechanisms of 3 types of comb-type superplasticizers used in Japan. The action mechanisms of comb-type superplasticizers and the compatibility of cements and superplasticizers are influenced by the molecular structure of polymers such as copolymer components and the grafted chain length of poly (ethylene-oxide) (PEO). Many reports regarding concrete research have investigated the influence of comb-type superplasticizers on the fluidity of concrete and the production of selfcompacting concrete. However, many have not considered the effect of the molecular structures of comb-type superplasticizers. This paper should be useful for engineers and researches studying the action of comb-type superplasticizers in the production of concrete with comb-type superplasticizers, and for understanding any new properties of such concrete.