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This Week's Featured Presentation

Field Evaluation of Early-Age Cracking in Concrete Bridge Decks and its Impact on Long-Term Durability
by Aleksandra Radlinska, Pennsylvania State University; and Farshad Rajabipour, Pennsylvania State University

Presentation details

Influence of Early-Age Properties on Crack Development and Long-Term Durability—Bridge Decks (ACI Fall 2017 Convention, Anaheim, CA)
The results of field investigation of early-age bridge deck cracking in the Commonwealth of Pennsylvania is summarized in this presentation. The goal was to use field data to identify factors that contribute to, or reduce, early-age cracking in concrete bridge decks and to assess the effect of cracks on long-term durability performance of bridge decks. Inspection data from 203 bridge decks were collected and analyzed to evaluate the effect of concrete mixture proportions and properties, construction methods, and rebar type on the propensity to experience early-age deck cracking. The inspections included 40 older bridge decks plus initial (post construction) inspection data for 163 new bridge decks that was received from PennDOT. The results suggest that limiting the total cementitious materials content (e.g., to 620 pcy) and the maximum compressive strength (e.g., to 5000 psi at 28 days) is advisable to reduce deck cracking. Decks constructed using half-width procedures cracked 4 times more than decks constructed full-width and using detours. Cracking accelerated rebar corrosion, but epoxy-coated rebar showed good corrosion resistance even in cracked concrete. The critical chloride content required for corrosion propagation increased from 0.03% (wt. of concrete) for black rebar to 0.20% for epoxy-coated rebar.

Upcoming Presentations

April 22 – 28

Early-Age Bridge Deck Cracking—A Case Study
by Elizabeth Nadelman, Wiss, Janney, Elstner Associates, Inc.

Presentation details

Influence of Early-Age Properties on Crack Development and Long-Term Durability—Bridge Decks (ACI Fall 2017 Convention, Anaheim, CA)
Numerous investigations and research studies have been performed to understand and prevent early age bridge deck cracking; however, the problem is still readily apparent. Understanding and preventing early age bridge deck cracking is very complex and challenging. Consideration should be given to mixture proportioning; concrete placement conditions and processes; bridge deck design and restraint; and early age curing. In this presentation, a case study will be presented where early age transverse cracking developed in numerous western Montana bridge decks. Within the first few years of service, the cracking progressed to cause full depth holes in two of the decks. A brief overview of project will be presented, including field investigation, laboratory studies, and modeling analyses. The effect of early age volume changes and resulting stresses due to temperature will detailed as it specifically relates to the western Montana bridge decks. Large stresses can develop at early ages not only due to global temperature changes, but also due to diurnal temperature changes, resulting in through deck temperature gradients Specific modeling efforts will be presented showing the importance of understanding early age stresses due to temperature and potential for development of transverse cracks. WJE’s proposed and implemented prevention plan will be discussed, and the efficacy of the prevention plan, implemented on subsequent new bridge decks, will be presented.

April 29 – May 5

Digital Concrete at ETH Zurich
by Timothy Wangler, ETH Zurich; and Ena Lloret, Norman Hack, and Lex Reiter, ETH Zurich

Presentation details

Concrete and Digital Fabrication: Perspectives, Challenges and Developments (ACI Fall 2017 Convention, Anaheim, CA)
With what has been called the “Third Industrial Revolution” well underway, digital technology is changing the paradigm in manufacturing from “mass production” to “mass customization”. This revolution is now beginning to creep into the construction sector, especially in recent years, with additive manufacturing with cementitious materials promising to revolutionize what is possible to construct by revolutionizing the way construction is performed, all the way from design to realization. At ETH Zurich, in the Chair of Physical Chemistry of Building Materials and Gramazio Kohler Research and under the auspices of the National Centre for Competence in Research in Digital Fabrication in Architecture, research on digital fabrication with concrete has been underway for the past few years. Here we present projects such as Smart Dynamic Casting, in which a moving formwork produces customized linear elements, and the Mesh Mould, in which a robotically constructed steel mesh serves both as formwork and reinforcement.

May 6 – 12

3D Printing Concrete—Workability and Rheology
by Mohammed Sonebi, Queen’s University Belfast; Sofiane Amziane, Blaise Pascal University; Damien Rangeard, National Institute of Applied Sciences; and Arnaud Perrot, Universite de Bretagne-Sud

Presentation details

Concrete and Digital Fabrication: Perspectives, Challenges and Developments (ACI Fall 2017 Convention, Anaheim, CA)
Inspired by the 3D printing with polymer materials, 3D printing opens new horizons to cement based materials of the construction industry. As formworks represent 35-60% of the overall costs of concrete structures, it would be an important benefit to use this new technology in construction and also it will be reduced the time of construction. The printability of fresh cement based materials is the ability of the layer to maintain itself and the weight of the layers subsequently deposited. The time gap between two deposited layers must be sufficiently long to provide adequate mechanical strength capable of sustaining the weight of the subsequently deposited layers and also short enough to provide an optimized bond strength and building rate. The aim of this research is to evaluate the effect of different mix composition such as addition of fly ash, silica fume, dosage of superplasticizer and dosage of fiber on fresh and rheological properties, and opening time of a 3D printable concrete.

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