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International Concrete Abstracts Portal

Showing 1-5 of 45 Abstracts search results

Document: 

SP-335_09

Date: 

September 20, 2019

Author(s):

A. M. Yasien, A. Abayou, and M. T. Bassuoni

Publication:

Symposium Papers

Volume:

335

Abstract:

In cold regions, freezing temperatures limit the construction season to few months, usually between May and September. The use of nanoparticles, which have high specific surface and vigorous reactivity, may potentially enhance the performance of concrete placed at low temperatures. Therefore, this study focused on developing concrete mixtures incorporating nano-silica which were mixed, placed and cured at -5°C (23°F) without any insulation or protection targeting field applications in late fall and early spring periods. Eight mixtures incorporating general use (GU) cement, fly ash (up to 25%), and nano-silica (up to 4%) were tested for this purpose, with water-to-binder ratios of 0.32 and 0.4. All mixtures contained a combination of calcium nitrate and calcium nitrite as an antifreeze admixture. Testing involved concrete setting time (placement), 7 and 28 days compressive strengths (hardened properties) and resistance to freezing-thawing cycles (durability). Moreover, mercury intrusion porosimetry, thermal analysis and scanning electron microscopy were performed to corroborate the trends from the macro-scale tests. It was found that nano-silica significantly improved the overall performance of concrete placed and cured at -5°C (23°F), which implicates its promising use for construction applications under low temperatures.


Document: 

SP326-117

Date: 

August 10, 2018

Author(s):

Vasily Sitnikov and Ivan Sitnikov

Publication:

Symposium Papers

Volume:

326

Abstract:

It is well-known that cooling of fresh concrete to a subfreezing temperature interrupts the structure formation and can lead to serious damages of constructions. Most of the existing antifreeze additives reduce this destructive effect, however it should be acknowledged that the processes of cement hydration is still interrupted to an extent that the strength gain in these conditions is simply negligible. When using these admixtures, it is merely expected that concrete will not lose its integrity during the phase of cooling and that strength will be gained after the ambient temperature will reach positive values. However, in our work we aim at proving the possibility of rapid strength gain of UHPC with reduced water-cement ratio even at subfreezing temperatures. The following article presents analysis of the influence of various in-house developed admixtures on kinetics of strength gain of UHPC at negative temperatures.


Document: 

SP326-121

Date: 

August 10, 2018

Author(s):

Satoshi Fujimoto

Publication:

Symposium Papers

Volume:

326

Abstract:

The quality of hardened concrete is severely degraded if the concrete is frozen at its setting or hardening stage. To prevent the degradation of materials, heating of the materials, equipment and facilities is widely utilized in ready-mixed concrete plants in cold regions of Japan. The heating is widely mentioned and conditionally recommended in specifications and recommendations. While these documents refer to material types to be heated and maximum temperature that will affect the quality of concrete, they do not refer to the energy sources or heating method for equipment and facilities. These factors, however, do have influences on the environmental performances at production stage of concrete. The difference in energy sources, types of heating and operation design of heating make significant difference in the emission of carbon dioxide and other global warming substances. Considering these importance, this paper surveys the types of energy sources and its system for concrete production at ready-mixed concrete plants in cold regions of Japan. The comparison of plants by the difference in seasonal temperature and the location is analyzed through monthly use of energy and on-site observation in various plants.


Document: 

SP282-02

Date: 

December 27, 2011

Author(s):

Norbert Delatte

Publication:

Symposium Papers

Volume:

282

Abstract:

Portland Cement Pervious Concrete (PCPC) is a material of increasing interest for parking lots and other applications. PCPC typically consists of coarse aggregates, portland cement, water, and various admixtures. In this research, in-service PCPC pavements were inspected in the field, and cores were removed in order to investigate properties in the laboratory. Field evaluation methods included visual inspection, two surface drainage measurements, and indirect transmission ultrasonic pulse velocity (UPV). Laboratory testing methods included void ratio, unit weight, compressive strength, splitting tensile strength, hydraulic conductivity, and direct transmission UPV. Because it is compacted on the surface with screeds or rollers, PCPC generally has higher strength, lower void ratio, and lower hydraulic conductivity at the surface than at the bottom. Therefore, the properties of the tops and bottoms of core samples were compared. Generally, the PCPC installations evaluated under this research project have performed well in freeze-thaw environments with little maintenance required. No visual indicators of freeze-thaw damage were observed. With the exception of some installations where the pore structure was sealed during construction with wet mixtures or over compaction, nearly all sites showed fair to good infiltration capability based on drain time measurements.

DOI:

10.14359/51683639


Document: 

SP275-62

Date: 

March 1, 2011

Author(s):

Amr El-Ragaby and Ehab F. El-Salakawy

Publication:

Symposium Papers

Volume:

275

Abstract:

The bridge deck slab is a prime example where FRP bars are used as main concrete reinforcement. In Canada, bridge deck slabs are usually subjected to a variation of cold and hot weathering while directly sustain the traffic loads. Both fatigue and thermal loading are expected to adversely affect the overall performance of such structural elements. In this research, a total of 4 large-scale bridge deck slabs totally reinforced with glass FRP bars were constructed and tested under simulated long-term loading and environmental conditions. The slabs were subjected to 3,000,000 cycles of sinusoidal waveform fatigue loading combined with either 100 freeze-thaw cycles or continuous cold temperature for one month. The test parameters included the environmental conditioning and the reinforcement ratio. It was concluded that the overall behavior of GFRP-reinforced bridge deck slabs after being subjected to simulated long-term fatigue load cycles and freeze-thaw or cold temperature is satisfactory according to the current design codes.

DOI:

10.14359/51682472


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