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International Concrete Abstracts Portal

Showing 1-5 of 40 Abstracts search results

Document: 

SP242-14

Date: 

April 1, 2007

Author(s):

I. Janotka

Publication:

Symposium Papers

Volume:

242

Abstract:

This paper reports high-strength concrete behavior subjected to temperatures up to 200 °C and 100 freezing and thawing cycles in regime of 8 hours in water at + 20 °C and 16 hours at - 20 °C (weekends in frost). The concrete is composed of 425 kg/m3 of portland cement of CEM I 42.5 type, 32 kg/m3 of silica fume, 5.6 L/m3 of super plasticizer Melment and has a W/C of 0.32. Compressive strength is 78.5 MPa at 28-day curing on cubes for temperature resistance tests and 63.1 MPa on prisms for freezing and thawing tests, both after 28-basic curing in 20 °C/100 % R. H. - air. Evident C-S-H dewaterization of the cement paste is observed between 100 °C and 200 °C. Initial shrinkage within 24-hour period due to rapid cooling is more detrimental on the cement paste strength than shrinkage due to C-S-H dewatering at temperature elevation from 100 °C to 200 °C. The strength, elastic modulus and volume deformation of concrete are irreversibly influenced either by temperature elevation or rapid cooling to 20 °C. Differences in strength, elastic modulus and shrinkage or expansion after 100 freezing and thawing cycles relative to those in water are negligible. The compressive strength of prisms subjected to 118-day freezing and thawing was 62.9 MPa, compared to 65.2 MPa for those kept in water.

DOI:

10.14359/18713


Document: 

SP242-13

Date: 

April 1, 2007

Author(s):

J. Matolepszy and E. Tkaczewska

Publication:

Symposium Papers

Volume:

242

Abstract:

This paper presents possibilities of use of fly ashes from co-burning bituminous coal and other fuels in cement production process. Both fly ashes coming from co-burning bituminous coal and biomass and the ones from coal combustion were analysed. The physical and chemical properties of the fly ashes were examined by determination of fineness, chemical and phase composition, pozzolanic activity and structure of the glassy phase. Cement samples with different content of the fly ashes were prepared. The following properties of the samples were tested: porosity, compressive strength as well as heat of hydration. The results show that cement samples containing fly ashes from co-burning bituminous coal and biomass had demonstrated adverse features like higher porosity, lower compressive strength after specified ages, than the ones containing fly ashes from bituminous coal combustion. The investigations of microstructure of the cements were also carried out by SEM.

DOI:

10.14359/18712


Document: 

SP242-03

Date: 

April 1, 2007

Author(s):

E. Matsuo, K. Hino, and S. Hamada

Publication:

Symposium Papers

Volume:

242

Abstract:

In Japan, sea sand is used frequently as fine aggregate for concrete. The mining of sea sand has been more difficult year by year for environmental reasons. This would be a serious problem in manufacturing concrete. The amount of fly ash has been increasing gradually in Japan, therefore the utilization of fly ash as the substitution of fine aggregate has a significant advantage. In this study, bending fatigue test of roller compacted concrete was carried out, in which all fine aggregate was replaced with fly ash. The obtained S-N curve was compared with that of normal concrete and general roller compacted concrete. Scatter of fatigue strength was also determined.

DOI:

10.14359/18702


Document: 

SP242-27

Date: 

April 1, 2007

Author(s):

T. Horiguchi, T. Kikuchi, Y. Nakagawa, and K. Shimura

Publication:

Symposium Papers

Volume:

242

Abstract:

This research evaluated, from the ecological and economical points of view, the potential use of high volumes of incineration ash from sewage sludge in CLSM (Controlled Low Strength Materials). Moreover, a dust powder from crushed stone production is used as a fine aggregate. This new type of green CLSM will be a promising sustainable cementitious material for reducing CO2 emissions. In-situ early-age strength estimation of CLSM was proposed with applying simple cone penetration method (so-called YCP Test, Yamanaka Cone Penetration Test), which has been used for soil strength estimation. Test result showed that the YCP Test is found to be effective for estimating the in-situ early-age compressive strength of CLSM. Test results also showed the adequate strength development and reasonable flowability are confirmed if the mixture proportion is carefully selected. Although, the compressive strength decreases with increasing level of incineration ash, this strength reduction is easily compensated for increasing a small amount of cement content. From these tests results it is confirmed that a wide range of municipal solid waste is applicable for the materials of a new green CLSM.

DOI:

10.14359/18726


Document: 

SP242-38

Date: 

April 1, 2007

Author(s):

Z. Pytel

Publication:

Symposium Papers

Volume:

242

Abstract:

The purpose of the research program was to investigate how the addition of new-generation wastes produced in the coal-fired power plant, fluidized-bed type installations, impact mechanical properties and chemical durability of cements. Tests were made on cements derived from two portland cement clinkers containing widely different amounts of C3A. With addition of the fluidized-bed material from the brown and black coal combustion systems blended portland cements were made. The properties of these blended cements were compared with those of the reference portland cements. The composition of all cements was adjusted to achieve the maximum permissible amount of SO3 i. e. 3.5%. Three different curing procedures were used for mortar specimens: normal temperature and humidity conditions, low pressure steam curing, and autoclaving. Durability to sulfate attack was studied using two methods: one method involved monitoring of linear dimensions of 20 x 20 x 160 mm mortar prisms cured under different conditions and exposed to aqueous solutions of Na2SO4 and MgSO4, with 16±0.5 g/l concentration of SO42- anions. The other method involved investigation of changes of mechanical properties of 25x25x100 mm mortar prisms cured under different conditions and subjected to prolonged sulfate exposure. The strength of samples was measured after different times of exposure in sulfate. Five percent aqueous solutions of Na2SO4 and MgSO4 were used for sulfate immersion test. Compressive and flexural strength tests were measured after 90, 180, 365, and 730 days of exposure. SEM and EDS techniques were used for microstructure studies.

DOI:

10.14359/18737


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