International Concrete Abstracts Portal

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International Concrete Abstracts Portal

Showing 1-10 of 899 Abstracts search results

Document: 

CI4201Mahoutian_Spotlight

Date: 

January 1, 2020

Author(s):

Mehrdad Mahoutian, Chris Stern, and Yixin Shao

Publication:

Concrete International

Volume:

42

Issue:

1

Abstract:

Steel furnace slag, a by-product of the steelmaking process, can be used as a portland cement replacement in production of concrete masonry units (CMUs). Even though steel furnace slag lacks cementitious or pozzolanic properties, it gains strength when exposed to CO2 in the presence of water. The article discusses technology for manufacturing CMUs using steel furnace slag as a total cement replacement.


Document: 

SP-336_07

Date: 

December 11, 2019

Author(s):

David Darwin, Rouzbeh Khajehdehi, Muzai Feng, James Lafikes, Eman Ibrahim, Matthew O’Reilly

Publication:

Special Publication

Volume:

336

Abstract:

The goal of this study was to implement cost-effective techniques for improving bridge deck service life through the reduction of cracking. Work was performed both in the laboratory and in the field, resulting in the creation of Low-Cracking High-Performance Concrete (LC-HPC) specifications that minimize cracking through the use of low slump, low paste content, moderate compressive strength, concrete temperature control, good consolidation, minimum finishing, and extended curing. This paper documents the performance of 17 decks constructed with LC-HPC specifications and 13 matching control bridge decks based on crack surveys. The LCHPC bridge decks exhibit less cracking than the matching control decks in the vast majority of cases. Only two LCHPC bridge decks have higher overall crack densities than their control decks, which are the two best performing control decks in the program, and the differences are small. The majority of the cracks are transverse and run parallel to the top layer of the deck reinforcement. The results of this study demonstrate the positive effects of reduced cement paste contents, concrete temperature control, limitations on or de-emphasis of maximum concrete compressive strength, limitations on maximum slump, the use of good consolidation, minimizing finishing operations, and application of curing shortly after finishing and for an extended time on minimizing cracking in bridge decks.


Document: 

SP-336_01

Date: 

December 11, 2019

Author(s):

James Lafikes, Rouzbeh Khajehdehi, Muzai Feng, Matthew O’Reilly, David Darwin

Publication:

Special Publication

Volume:

336

Abstract:

Supplementary cementitious materials (SCMs) in conjunction with pre-wetted fine lightweight aggregate to provide internal curing are being increasingly used to produce high performance, low-shrinking concrete to mitigate bridge deck cracking, providing more sustainable projects with a longer service life. Additionally, the SCMs aid in concrete sustainability by reducing the amount of cement needed in these projects. This study examines the density of cracks in bridge decks in Indiana and Utah that incorporated internal curing with various combinations of portland cement and SCMs, specifically, slag cement, Class C and Class F fly ash, and silica fume, in concrete mixtures with water-cementitious material ratios ranging from 0.39 to 0.44. When compared with crack densities in low-cracking high-performance concrete (LC-HPC) and control bridge decks in Kansas, concrete mixtures with a paste content higher than 27% exhibited more cracking, regardless of the use of internal curing or SCMs. Bridge decks with paste contents below 26% that incorporate internal curing and SCMs exhibited low cracking at early ages, although additional surveys will be needed before conclusions on long term behavior can be made.


Document: 

CI4112ProdPracticeSpotlight

Date: 

December 1, 2019

Publication:

Concrete International

Volume:

41

Issue:

12

Abstract:

MaturixTM, a concrete placement monitoring system, can be used to determine the temperature and strength of concrete placements. The system comprises type K or type A temperature sensors coupled to reusable, weatherproof wireless transmitters. After concrete is placed, the transmitters begin sending data that can be monitored using a mobile device or computer.


Document: 

SP-334-11

Date: 

September 30, 2019

Author(s):

Eslam Y. Gomaa, Ahmed A. Gheni, and Mohamed A. ElGawady

Publication:

Special Publication

Volume:

334

Abstract:

The durability of alkali activated concrete (AAC) synthesized using high calcium fly ashes (FAs) was studied. Surface resistivity, bulk electrical resistivity, rapid chloride ions penetration, and freeze-thaw resistance tests were carried out on AAC made with five different FAs. The specimens were either oven-or moist-cured. The effect of adding air entraining admixture (AEA) and recycled crumb rubber to the AAC specimens on the freeze-thaw resistance was investigated as well. It was found that the durability of AAC was higher than that of comparable ordinary Portland cement (OPC) concrete. Adding the AEA improved the freeze-thaw resistance but not enough to complete the 300 cycles, per ASTM C666-15. Adding the rubber to the AAC mixtures improved the freeze-thaw resistance significantly.


Document: 

SP-334-07

Date: 

September 30, 2019

Author(s):

A.M. Said, O. Saleh and A. Ayad

Publication:

Special Publication

Volume:

334

Abstract:

There is a growing need for alternative binders with smaller carbon footprint. The cement manufacture is an energy intensive process that is one of the major global contributors to carbon dioxide emission. Fly ash-based geopolymer binders represent one of these potential alternatives. Beside consuming a largely produced byproduct, fly ash-based geopolymers generally have better mechanical performance when exposed to elevated temperatures. This study evaluates the effect of the initial curing temperature and the alkaline activation solution proportions on the strength, pores structure and crystal structure of fly ash-based geopolymer mortars. The geopolymer was synthesized using Class F fly ash, potassium hydroxide solution and sodium silicate solution. The specimens were made using various ratios of sodium silicate to potassium hydroxide and were initially cured at different temperatures and their properties were studied in terms of mechanical and microstructural properties.


Document: 

SP-335_10

Date: 

September 20, 2019

Author(s):

Vemuganti, S., Rahman, M.K., and Reda Taha, M. M.

Publication:

Special Publication

Volume:

335

Abstract:

Nanomaterials like nanosilica, nanoalumina and nanoclay have shown improvement in workability and increased compressive strength when used with cement. However, the potential of using nanoclay to alter the elastic modulus and limit creep of oil-well cement (OWC), specifically when cured under high temperature and pressure, has not been explored. In this investigation, Type-G cement mixed with 1.0 wt.%, 3.0 wt.% and 5.0 wt.% nanoclay and with water/cement ratio of 0.45 was prepared and cured for 7 days under high temperature and pressure of 80 ℃ (176 ℉) and 10 MPa (1500 psi) respectively. Dynamic mechanical analysis was conducted under high temperature to reveal the evolution of the elastic modulus and creep compliance of the different cement-nanoclay mixture with curing time. Thermogravimetric analysis, Scanning Electron Microscope and X-ray Diffraction measurements were performed to support observations of elastic modulus and creep compliance evolution of OWC incorporating nanoclay explaining the microstructural changes that take place in OWC mixture incorporating nanoclay when hydrated under high temperature and pressure.


Document: 

CI4108Spotlight_1129B

Date: 

August 1, 2019

Publication:

Concrete International

Volume:

41

Issue:

8

Abstract:

Selecting a curing method for concrete depends on product type and local climate conditions. Polarmatic Oy from Tampere, Finland, provides thermal-energy units for various curing applications including warm, moist air; circulating warm water; and turbosteam. A Polarmatic unit is used by a precast concrete producer in Canada for heating aggregates, curing concrete, heating mixing water, and heating its buildings.


Document: 

CI4012Q&A

Date: 

December 1, 2018

Publication:

Concrete International

Volume:

40

Issue:

12

Abstract:

My company constructs concrete bridge decks throughout the upper Midwest and Northwest United States. Can you explain why we occasionally experience excessive cracking even though we cure the bridge decks according to the state’s DOT requirements?


Document: 

SP327-29

Date: 

November 1, 2018

Author(s):

Mostafa Yossef, An Chen and Austin Downey

Publication:

Special Publication

Volume:

327

Abstract:

Insulated concrete sandwich panels are composed of two concrete wythes separated by an insulation layer and connected by shear connectors. This paper develops a multifunctional photovoltaic (PV) integrated insulated concrete sandwich (PVICS) panel, which can act as a passive energy system through the insulation layer and an active energy system by harvesting the solar energy using attached thin-film solar cells. The panel features an innovative co-curing scheme, where solar cells, Fiber-Reinforced Polymer (FRP) shell, and polymer concrete are manufactured together to act as a formwork for the sandwich panel. The objective of this paper is to prove the concept of PVICS based on bending test, Finite Element (FE) analysis and analytical study. It can be concluded that the test results correlate well with those from the FE and analytical models. FRP shell can act as both shear connectors and reinforcement. The panel achieved 82% Degree of Composite Action, which can provide enough strength and stiffness. Solar cells worked properly under service load. Shear-lag effect was observed for the strains along the width of the panel.


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