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International Concrete Abstracts Portal

Showing 1-5 of 13 Abstracts search results

Document: 

SP247-04

Date: 

September 1, 2007

Author(s):

R.C. Lewis and J. Larsson

Publication:

Symposium Papers

Volume:

247

Abstract:

The precast industry has always been looking for ways to improve production. Be that ease of casting or finishing, faster turnaround or better economics due to less damage or reduced concrete costs. The advent of self consolidating concrete (SCC) has enabled some of these aspects to be realised. The development of SCC and new mixture design procedures has improved certain facets of the precast industry. However, the excessive use of fillers or very high cement contents has had equal drawbacks for the use of SCC in this environment. With the advances in software allowing very precise particle packing analyses to be made of the materials, new mix designs with lower total binder contents - and little or no fillers - are possible. Designs with supplementary cementitious materials (SCMs), including silica fume, can be very effective for SCC, not only giving excellent flow and non-segregation, but also enhancing the finished quality of the concrete. This paper reviews the use of silica fume in SCC, information from the Technically Optimised Piling Concrete (TOPIC) research in the UK, and gives examples of the use in some precast operations in Sweden.

DOI:

10.14359/18997


Document: 

SP247-09

Date: 

September 1, 2007

Author(s):

R. Burgueño and M. Haq

Publication:

Symposium Papers

Volume:

247

Abstract:

The mix design deviations required to achieve self-consolidating concrete (SCC) have raised concerns on the effect that this may have on the bond performance of reinforcement. The paper summarizes an investigation on the effect of SCC mix proportioning on the bond behavior and bond-related parameters of transfer and development length of 13mm (0.5 in.) diameter prestressing strands. Three SCC mix designs that bound the common approaches to achieve SCC and a reference normally consolidated concrete (NCC) mix were used. Direct bond strength was assessed by simple strand pull-out tests. Using laboratory-scale T-beams, transfer length was evaluated by concrete surface strains and draw-in measurements, while development lengths were estimated through flexural tests. Results indicated the bond performance of strand in SCC to be lower than for NCC. Transfer and development lengths for SCC were longer than for NCC; yet, on average, these lengths still met the ACI code recommendations. Bond performance for the different SCC mixes was distinct, consistent and bounded by the extreme cases considered. Given the variability and uncertainties in the experimental methods and code equations, results from this study indicate that bond performance on SCC, as it pertains to anchorage lengths, is adequate.

DOI:

10.14359/19002


Document: 

SP247-10

Date: 

September 1, 2007

Author(s):

E. Salcedo Rueda and A.J. Schokker

Publication:

Symposium Papers

Volume:

247

Abstract:

The use of Self-Consolidating Concrete (SCC) is becoming more prevalent in both building and bridge applications. Newcrete Products in Roaring Spring, Pennsylvania has experience with use of an SCC mix in parking structure members such as double-tee sections. While SCC is not yet widely used in bridge members in Pennsylvania, this application is also of interest. Newcrete in cooperation with Penn State University developed a program for bond evaluation of the Newcrete SCC mix. The objectives of the program are as follows: 1) to compare the Newcrete SCC mix with the current design code requirement for transfer length, 2) to determine the pull-out capacity of the strand in the SCC mix with the Moustafa test, 3) evaluate the failure mode at ultimate, and 4) compare the results of the SCC mix with a standard (non-SCC) Newcrete mix.

DOI:

10.14359/19003


Document: 

SP247-06

Date: 

September 1, 2007

Author(s):

R. Burgueño and D.A. Bendert

Publication:

Symposium Papers

Volume:

247

Abstract:

A demonstration bridge project in Michigan is allowing the state’s Department of Transportation to evaluate the short- and long-term structural performance of self-consolidating-concrete (SCC) in bridge beams. The M-50/US-127 Bridge over the Grand River (Jackson, Michigan) features SCC prestressed box beams in 3 of its 6 beams. Three SCC mixture proportions are being evaluated against a reference normally consolidated concrete mixture (NCC). Before implementation, performance of the SCC beams was evaluated through full-scale flexure and shear testing to ensure similar performance to the NCC beams. The SCC beams met the nominal design capacities and their performance was essentially the same as the NCC beams. With this validation, the demonstration bridge with its SCC beams was completed in October 2005. A strain and temperature continuous monitoring system was placed on the SCC beams and one NCC beam to evaluate long-term performance. Collected data since December 2005 indicates that the field performance of the SCC beams is similar to the NCC beams.

DOI:

10.14359/18999


Document: 

SP247-02

Date: 

September 1, 2007

Author(s):

H.N. Atahan, D. Trejo, and M.D. Hueste

Publication:

Symposium Papers

Volume:

247

Abstract:

Self-consolidating concrete (SCC) is being implemented throughout the US. Some advantages of SCC include its ease of placement, reduced labor requirements for placing the material, reduced noise when placing, and its improved finish quality. Clearly there are benefits of using this material. However, the AASHTO LRFD specifications were developed based on material characteristics of conventional, normal strength concretes. Because of this, engineers and designers are reluctant to specify and use SCC for bridge applications, possibly making the potential benefits of this material underutilized. This research investigated compressive strength development, modulus of elasticity (MOE), modulus of rupture (MOR), and splitting tensile strength (STS) of SCC mixtures specifically designed for precast, prestressed, concrete bridge girders. The experimental program included two target 16-hour compressive strength levels and two coarse aggregate types (river gravel and crushed limestone) with varying volume fractions. The measured mechanical properties for the SCC mixtures were compared with the results of conventional concrete (CC) mixtures of similar release strengths, as well as the estimated values from the 2006 AASHTO LRFD prediction equations. Results indicate that the AASHTO equations either predict the mechanical properties of SCC fairly well or underestimate the properties of SCC.

DOI:

10.14359/18995


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