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Showing 1-5 of 55 Abstracts search results

Document: 

SP199-20

Date: 

June 1, 2001

Author(s):

E. U. Kidav, T. P. Soo, V. Sirivivatnanon, and R. Khatri

Publication:

Symposium Papers

Volume:

199

Abstract:

The potential use of Malaysian fly ash cement in concrete has been studied in terms of its influence on elastic properties, volume stability and durability properties. In durability studies, the resistance to chloride ingress, sulfate attack, and suppression of alkali-aggregate reactivity were examined. The results are presented and discussed. The role of the fly ash on heat of hydration, production of roller-compacted concrete, and high-strength, high-performance concrete have been proven in practice. Understanding the influence of fly ash on both fresh and hardened properties of concrete has led to its appropriate use in many important structures in Malaysia. They include the Petronas Twin Towers, the second Malaysia Singapore Causeway, and more recently considered for the construction of a major RCC dam. Properties of fly ash concrete are discussed with examples of application.

DOI:

10.14359/10503


Document: 

SP199-03

Date: 

June 1, 2001

Author(s):

P. K. Kolay and D. N. Singh

Publication:

Symposium Papers

Volume:

199

Abstract:

Synopsis: The amount of ash, produced from the coal fired thermal power plants and its hazardous impact on the environment is continuously increasing. This poses a challenging task of safe handling, proper disposal and utilisation of the ash. The huge quantity of ash produced from these power plants calls for a special attention in terms of its proper utilisation, either directly, or conversion into a value-added product. Chemical activation of the coal ash is being practised for synthesising ash zeolites. These zeolites are being used for various environmental protection schemes and other industrial processes. With this object in view, an effort has been made in this paper to study the effect of chemical activation of a typical class F lagoon ash. This chemical activation is achieved under controlled conditions, in the laboratory, with different concentrations of alkali (NaOH) and for different durations of activation.

DOI:

10.14359/10483


Document: 

SP199-27

Date: 

June 1, 2001

Author(s):

M. Maage

Publication:

Symposium Papers

Volume:

199

Abstract:

The practical application of silica fume started in the late seventies. At that time and the following years, opinions on the effect of silica fume on reinforcement corrosion varied quite a lot. Since then a lot of research has been carried out and the results of many years of practical experience are known. The corrosion process of reinforcement steel in concrete may be divided into two stages: the initiation period and the propagation period. Silica fume affects both the two stages. In the initiation period, carbonation is going on or chlorides are transported into the concrete. The carbonation process results in reduced pH values allowing corrosion to start. Silica fume may be expected to reduce the resistance against carbonation due to reduced amount of calcium hydroxide. On the other hand, silica fume will also improve the resistance against CO? ingress. A concentration of chlorides higher that the threshold value at the steel surface may result in reinforcement corrosion. Silica fume reduces the chloride binding capacity of the binder, leaving more chlorides to attack the steel, but again silica fume will also improve the resistance against chloride ingress. In the propagation period, the electrical resistivity of the concrete and oxygen diffusion are the governing factors for corrosion rate. The first is very much increased by silica fume, the second more debatable. Based on literature review, all important factors for the initiation period and the propagation period are discussed. As far as possible, consensus for each factor is given and an overall conclusion for the effect of silica fume on reinforcement corrosion is given. The overall conclusion is that silica fume has both positive and negative effects on the different factors governing the steel reinforcement corrosion. However, the positive factors are dominating by far over the negative factors.

DOI:

10.14359/10530


Document: 

SP199-40

Date: 

June 1, 2001

Author(s):

Tarek Uddin Mohammed, Toru Yamaji, Toshiyuki Aoyama, and Hidenori Hamada

Publication:

Symposium Papers

Volume:

199

Abstract:

Corrosion of steel bars in pre-cracked prism specimens exposed in marine environment for 15-year is presented here. The size of the specimens was 100x100x600 mm. The specimens were made with ordinary Portland, slag (Type A, B and C) and fly ash (Type B) cements. A round steel bar of diameter 9 mm was embedded in each specimen. W/C were 0.45 and 0.55. Crack widths were varied from 0.1 to 5 mm. Chloride-ion concentrations in concrete and corrosion of steel bars were evaluated. Narrower cracks ( < 0.5 mm) heal irrespective of the cement types. Chloride ingress and corrosion of steel bars in concrete are highest for the specimens made with ordinary portland cement and lowest for the specimens made with slag cement of Type C. Locations of the maximum corroded area as well as the deepest corrosion pit are not necessarily at or near the cracked region Wider cracks are not healed and maximum corroded area and deepest corrosion pit are observed at the cracked region. The presence of voids at the steel-concrete interface results in corrosion pits even for chloride-ion concentration less than 0.4% of cement by weight.

DOI:

10.14359/10543


Document: 

SP199-47

Date: 

June 1, 2001

Author(s):

S. I. Pavlenko, V. I. Malyshkin, and V. V. Tkachenko

Publication:

Symposium Papers

Volume:

199

Abstract:

In the process of a long-term study of fine cementless mortar from wastes of thermal power plants (TPP) and other industries, aspects of its tech-nology were determined which were as follows: power 1. Processing slag (also known as bottom plant to sand of 0 to 5 mm size fraction. ash) from the Abakan thermal 2. Grinding fly ash to a fineness of 700 to 750 m2/kg with the use of mechanochemical activation process. 3. Using two - stage thermal treatment of cementless mortar mixture and determining optimal regimes for secondary thermal treatment. 4. Using a model method for concrete development. The application of cementless ash slag mortars non- load - bearing concrete profitability respectively. to load - bearing and

DOI:

10.14359/10550


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