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Showing 1-5 of 60 Abstracts search results

Document: 

SP178-06

Date: 

June 1, 1998

Author(s):

K. Wangwichit, M. Hisada, N. Otsuki and S. Nagataki

Publication:

Symposium Papers

Volume:

178

Abstract:

In Thailand, the utilization of fly ash as a concrete admixture has been increasing gradually. However, there are no local standards regulating the use of fly ash. Mixing of concrete usually follows standards that contain requirements, especially temperature, that are difficult or sometimes impossible to satisfy. Therefore, this research was carried out to verify the influence of temperature, hot (Thailand) and temperate (Japan) climate, on the strength and durability properties of fly ash mortar. Also, to propose an optimum range of cement replacement percentage and water-binder ratio for each kind of fly ash under Thai (simulated) and Japanese climate conditions. From this investigation, it was found that fly ash exhibited advantages in strength and durability of mortar under high temperature. The strength activity index of both fly ash mortars were satisfied in accordance with ASTM C 618 under all temperatures considered. Furthermore, the optimum range of cement replacement and water-binder ratio became wider with increasing temperature. Thus, fly ash is recommended to be used under high temperature.

DOI:

10.14359/5974


Document: 

SP178-39

Date: 

June 1, 1998

Author(s):

A.A. Ramezanianpour, Radfar, Hadikhanloo, Moslehi and Maghsoodi

Publication:

Symposium Papers

Volume:

178

Abstract:

As part of a comprehensive research project on the durability of on and offshore concrete structures in the Persian Gulf, a simulation laboratory has been made use of. The present study consists mainly of nine month exposure tests in the tidal and atmospheric zone conditions in the laboratory. Concrete specimens containing different supplementary materials, namely; silica fume, blast - furnace slag, diatomous earth and trass, have been thoroughly investigated. The tests conducted include, compressive strength, volume changes, half cell potentials, carbonation, and chloride diffusion, all at different ages. With respect to the alternate cycles of wetting and drying the superior preformance of silica fume was followed by the diatomous earth pozzolan. However all concrete mixtures containing natural and artificial pozzolans showed better performance when compared with the plain portland cement control concrete mixtures.

DOI:

10.14359/6007


Document: 

SP178-19

Date: 

June 1, 1998

Author(s):

R.N. Swamy and H.H. Hung

Publication:

Symposium Papers

Volume:

178

Abstract:

The development of a high performance, high volume fly ash (HVFA) concrete incorporating a small amount of silica fume, and part replacement of both cement and sand with fly ash (FA) is reported. This paper presents the results on the engineering properties such as strength, dynamic modulus and swelling/shrinkage of such high volume fly ash concrete. The mixtures were proportioned to give 30 to 40 MPa cube strength at 28 days. Two basic mixtures with total binder contents of 350 kg/m3 and 450 kg/m3, and, with a minimum portland cement content of 150 and 200 kg/m3 respectively, were investigated. In each mixture, about 60 per cent of the cement was replaced by fly ash. In addition, in some mixtures, a nominal amount of silica fume was incorporated, and in some others, additional FA was incorporated as replacement for sand. The results show that the total binder content had little effect on strength, swelling strain and drying shrinkage, but had a significant effect on the dynamic modulus of elasticity implying a clear densification of the microstructure by fly ash and silica fume. On the whole, HVFA concrete with a nominal amount of SF, and FA as part replacement of both cement and sand showed better overall performance. The engineering properties of the HVFA concretes investigated show good potential for use in structural and mass concrete applications.

DOI:

10.14359/5987


Document: 

SP178-17

Date: 

June 1, 1998

Author(s):

S. Morel, P. Clastres, D. Mathieu and A. Pellequer

Publication:

Symposium Papers

Volume:

178

Abstract:

This study proposes a new method for a process development based on specific planning and use of experiments. The ‘Statistical Design Of Experiments’ method comprising the selection of experiments in manner where the results derived from these experiments can be used for the calculation of values to be analysed. Ash produced from the Incineration of Municipal Solid Wastes requires to be solidified and stabilised prior to landfilling. MSWI fly ash is a powdery material. It comprises hydraulic and toxic elements. Ground granulated blast furnace slag is a suitable hydraulic binder to stabilise this ash and MSWI ash can activate the slag hydraulicity. A preliminary study was undertaken on artificial MSWI ash to analyse the influence of the variation of the content of (Ca(OH)2 , CaCIOH, CaS04 ) ash components, while taking into account their interactions effects. It was demonstrated that CaClOH content significantly influences the behaviour of the material. Empirical laws were also developed to determine the mechanical and physical behaviour of mixtures of industrial MSWI ash and slag. The parameters of these models were A/S, W/(A+S), and the water temperature. Then, using the various models developed, an optimum formulation of the MSWI ash and slag mixture was developed, which fulfils the requirements of French Regulations.

DOI:

10.14359/5985


Document: 

SP178-59

Date: 

June 1, 1998

Author(s):

M.A. Berube, J. Duchesne and J. Frenette

Publication:

Symposium Papers

Volume:

178

Abstract:

Cement paste samples incorporating various amounts of silica fume were made and stored in humid air at 23°C and 38°C. Their pore solution was expressed under high pressure at different times, then analyzed for its alkali content. The storage temperature did not significantly affect the alkali concentration in the short term (O-28 days), where most reaction products (hydrates) are formed. However, all control and blended pastes stored at 38°C recycled very significant amounts of alkali in the pore solution between 28 days and 1.5 years, while not those stored at 23°C. Consequently, the longter effectiveness of silica fume against ASR should be better than expected from a number of recent experimental studies all involving concrete expansion tests conducted at 38°C for field concretes exposed at an average lower temperature, e.g. in many regions of the world. This would explain at the same time why satisfactory field performance is reported in Iceland, for instance, while the only one case reported until now relating to poor field performance of silica fume against ASR took place under the hot South African climate. Results from concrete prism expansion tests also indicated that ASR expansion can develop in high-performance concrete, even with moderately reactive aggregates. Other expansion results confirmed that the higher the degree of reactivity of the particular reactive aggregate to counteract, the alkali content in the silica fume, the alkali content in the portland cement used, and the cement dosage, in other words the higher the total concrete alkali content, the higher is the amount of silica fume required to counteract ASR expansion. The study also indicated that pelletizing the silica fume before mixing with the clinker at the grinding stage did not reduce its effectiveness against ASR, provided the grinding process is effective in dispersing the silica fume.

DOI:

10.14359/6027


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