Browsing by Author "Peng, YN"

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A design consideration for durability of high-performance concrete
(2001-08-01)
Chang, PK
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Peng, YN
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Hwang, CL
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交大名義發表
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National Chiao Tung University
Environmental factors, especially the climate, have significant influence on concrete structure. This paper aims to investigate the harmful effects of maritime climate on the durability of concrete structures built in coastal areas. Singly reinforced beam specimens of traditional design and those of densified mixture design algorithm (DMDA) were employed to study the potential problems of concrete structure. Results indicate that cracks on the concrete structure, if go unnoticed, may cause failures. Thus, it is important to know the methodology of achieving high strength and durable concrete in order to avoid formation of cracks in the structural member. (C) 2001 Elsevier Science Ltd. All rights reserved.
A study on characteristics of interfacial transition zone in concrete
(2004-06-01)
Liao, KY
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Chang, PK
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Peng, YN
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Yang, CC
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土木工程學系
The aim of this study was to observe the behavior of the interfacial transition zone (ITZ) of high-performance concrete that was under curing in saturated lime water. From the Scanning Electron Microscope (SEM), it was found that the pores and hydration products at the ITZ, within 100 mum between the paste and aggregate, permuted each other during the early hydration stage, and then appeared as a large lump or strip. They gradually became irregular and small lumps for the further curing age. At the curing age of 56 days, the pores almost concentrated within an area of 0-15 mum from the aggregate edge. The hydration products were much denser with the increase in its distance from the aggregate edge. (C) 2004 Elsevier Ltd. All rights reserved.
Characteristics of microhydrates formed under steam conditions
(2000-05-01)
Lin, WM
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Hwang, CL
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Peng, YN
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土木工程學系
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Department of Civil Engineering
This paper presents the physical properties and chemical composition of hydrates formed under steam conditions. The test specimens were made with cement as well as individual compounds. A comprehensive study on the characteristics of hardened hydrates in a microscopic scale was carried out. An improved polymerization of silicate anions resulting in an increased CaO/SiO2 ratio at an elevated temperature was verified by the nuclear magnetic resonance spectroscopy (NMR) analysis. Dense microstructures of hydrates and low content of Ca(OH)(2) crystals were observed by the scanning electron microscope (SEM), energy dispersive spectromer (EDS), environmental scanning electron microscope (ESEM), thermogravimetric analyzer (TGA), and x-ray diffractometer (XRD) tests. Mercury intrusion porosimetry (MIP) had been used to examine the pore structures of hydrates. It revealed that the hardened paste made with the dry-mixture/steam-injection (DMSI) method developed microstructures with low porosity, small pore radius, and larger surface areas. These observations agree with the NMR/TGA test results. This paper also discusses the effects of sample fineness and compaction on the hydrate's microstructures formed under steam environment. The test results verify the validity of the DMSI concept.
Fundamental study on hydration of cement and cement minerals with steam
(1998-01-01)
Lin, WM
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Lin, TD
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Hwang, CL
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Peng, YN
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土木工程學系
This paper-discusses the basic concept of steam hydration and presents test data oil heat of hydration by exposing cement compounds to pressurized steam. The lest samples include cement and its individual compounds; tricalcium silicate (C3S), dicalcium silicate (C2S), tricalcium aluminate (C(3)A), and tetracalcium aluminoferrite (C(4)AF). For a compacted 10 grams C3S sample, the heat of hydration was determined as 209 cal/g. All samples except C;A hardened during steaming. Nonetheless, rite C(3)A samples reacted very rapidly with steam and registered a 91 C temperature rise during the test. This paper also discusses effects of sample's fineness and degree of compaction on heat evolution and hydrate morphology during exposure to steam. The test results verify the validity of the dry-mix/steam-injection (DMSI) concept.
Influence of mixing techniques on properties of high performance concrete
(2001-01-01)
Chang, PK
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Peng, YN
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土木工程學系
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Department of Civil Engineering
Six mixing methods were used to prepare high performance concrete (HPC) of high flowability. The properties of the fresh and hardened concrete are measured. It is found that adding all superplasticizers (SP) in watts in one dose can ensure that workability can be maintained. The tested results identified a most efficient and economical method in making HPC. especially for lower binder content, which requires less mixing time and less amount of SP in producing the resulting material with higher flowability and better compressive strength than the other methods. (C) 2001 Elsevier Science Ltd. All rights reserved.
The characteristics and engineering properties of dry-mix/steam-injection concrete
(2001-04-01)
Su, N
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Peng, YN
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土木工程學系
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Department of Civil Engineering
This study aims to investigate the characteristics and engineering properties of the dry-mix/steam-injection method (DMSIM) which was developed to overcome difficulties involved in vacuum conditions of the lunar environment. A comparison was made to examine the differences in the hydration process, mechanical properties and the composition of hydration products between DMSIM and the normal-temperature wet-mix method (NTWMM). In DMSIM. when dry cement particles come in contact with steam, heal immediately transfers from the steam to the cement, with part of the steam being forced into the inner regions of the cement particles via the micropores. As cement particles gain activation energy and moisture condensed from steam? they undergo rapid and complete hydration. Test results showed that the optimal steaming temperature for dry-mix samples of cement and standard sand is 180-200 degreesC and the optimal steaming scenario for 10 cm(3) samples of concrete is at 200 degreesC for 18 h. The present DMSIM has advantages of lower cement content, shorter hardening time and higher concrete strengths, as compared to NTWMM. (C) 2001 Elsevier Science Ltd. Ail rights reserved.
The macro- and micro properties of cement pastes with silica-rich materials cured by wet-mixed steaming injection
(2003-09-01)
Wu, DS
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Peng, YN
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土木工程學系
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Department of Civil Engineering
This research used cement pastes with a low water/blaine ratio (W/b = 0.27). Rice husk ashes (REA) burned at 700 and 850 degreesC, silica fume, silica sand (Ottawa standard sand), etc., were the added ingredients. Wet-mixed steam injection (WMSI) was at five different temperatures: 65, 80, 120, 150 and 180 degreesC. We investigated cement pastes with added silica-rich materials. For different WMSI temperatures and times, we explored the relations between compressive strength, hydration products, and pozzolanic reaction mechanism. From scanning electron microscopy (SEM) and EDS, we know that hydration products become very complicated, depending on the WMSI temperatures and times. It is difficult to determine the direct effects on the strength based on changes in the products. Experimental results, however, clearly showed that the compressive strength was worst for 80 degreesC and best for 180 degreesC. High-temperature WMSI is best with 4-h presteaming period and 8-h retention time. Curing in saturated limewater for 28 days did not increase the strength. The three types of silica-rich materials used in this research all participated in the reaction during high-temperature WMSI; they helped to increase the strength. Addition of Ottawa standard sand resulted in the best strength, followed by addition of RHA, while addition of silica fume was worse than the others. Specimens treated with high-temperature WMSI would swell slightly if they were placed in air. This was different from normal-temperature curing. (C) 2003 Elsevier Science Ltd. All rights reserved.