International Concrete Abstracts Portal

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International Concrete Abstracts Portal

Showing 1-10 of 895 Abstracts search results

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.


Document: 

SP327-01

Date: 

November 1, 2018

Author(s):

Erblina Vokshi

Publication:

Special Publication

Volume:

327

Abstract:

SYNOPSIS: The use of wet lay-up fiber-reinforced polymers (FRPs) in the construction industry continues to grow. Their lightweight, durability, and good material properties makes them very desirable in the concrete repair industry. Research has shown that these products greatly improve the strength of repaired corroded members and reduce the rate of post-repair corrosion. There is a lack of research, however, in understanding how curing of these systems in the presence of moisture or underwater may affect their ability to strengthen and protect reinforced concrete. In this paper, data on material properties of a prepreg system, cured in laboratory conditions and under-water is presented and compared. The results show that there is a very small drop in tensile material properties when the system is cured underwater. Compression of concrete cylinders strengthened with one layer of the system and cured underwater is shown to be in agreement with ACI 440.2R-08’s confinement equations. Durability testing of the bond between the system and reinforced concrete using dolly pull-off test shows a 90% bond strength retention after 1,000hr exposure to various aggressive environments.


Document: 

SP-330-18

Date: 

September 26, 2018

Author(s):

Baoliang Li, Binbin Huo, and Yamei Zhang

Publication:

Special Publication

Volume:

330

Abstract:

To meet the requirements of building industrialization of construction, steam curing is widely used to produce concrete elements in factories in China. However, there are few reports relating to the properties of steam cured concrete under dry-wet cycle and sulfate attack. The performance of steam cured (80°C (176°F) for 7h) GGBFS blended cement mortar (20% cement is substituted by GGBFS) under sulfate attack and dry-wet cycle condition were investigated. Under dry-wet cycle, both steam cured and standard cured GGBFS mortar present worse sulfate resistance compared with those of pure cement mortar. However, early age steam curing improves the sulfate resistance of GGBFS mortar, but decreases the sulfate resistance of pure cement mortar. The formation of hemicarbonate and C-A-S-H under steam curing seems to be beneficial for protecting against the sulfate attack of cement mortar, but the coarse pore structure caused by steam cuing is harmful to the sulfate resistance of cement mortar.


Document: 

SP-329-23

Date: 

September 26, 2018

Author(s):

Fei Xiao, Yongwei Wang, Jinhuan Lv, Jie Zhang, and Tongwei Lu

Publication:

Special Publication

Volume:

329

Abstract:

In many parts of the world, the lowest temperature in winter is less than -20 degrees Celsius. It is an important problem in the field of construction engineering to improve the quality of concrete engineering and improve the durability of the structure under extreme climate. This paper introduces the development of ultralow temperature anti freezing pumping admixture. In the experiment, the concrete cured at -4°F (-20 °C) or -13°F (-25°C) for 7 days. And then the specimens were maintained in standard condition for different ages. Mechanical and durability properties of concrete were test in different curing conditions and different ages were studied. Mechanical properties include “negative temperature” compressive and flexural strength. Durability includes anti-permeability performance, dry shrinkage and chloride ion penetration resistance. The experimental data shows that the concrete have good mechanical and durability properties in ultra-low temperature because of the addition of an anti-freezing pumping agent. Compared with ordinary antifreeze, the negative temperature strength of concrete mixed with this ultralow temperature anti freezing pumping agent can be increased by more than 100%. By means of scanning electron microscopy (SEM) and pore size analysis were carried out. The action of this super low temperature anti freezing pumping agent and the frost resistance mechanism of concrete are analyzed.


Document: 

SP326-87

Date: 

August 10, 2018

Author(s):

Daman K. Panesar and Duo Zhang

Publication:

Special Publication

Volume:

326

Abstract:

The precast concrete industry is considering approaches with respect to mix design constituents and manufacturing methods to reduce the environmental impact of concrete products without compromising the desired properties and performance. The specific focus of this study is to examine the effect of using limestone filler and ground granulated blast furnace slag as cement replacement on the early age (one-day) compressive strength of steam cured precast concrete. Although it is known that a potential risk of incorporating such material may compromise the rate of hydration reactions and result in an inferior compressive strength gain which could delay demolding and prestressing operations reducing the rate of product production. This study explores the interplay between steam curing variables and mix design constituents to identify the variables that most significantly control the one-day strength of precast concrete. Key outcomes of this research reveal that the GU (general use) cement content (504 – 600 kg/m3) [31.5-37.5 lb/ft3], and the percentage of slag (up to 16.7%) has a greater effect on the one-day strength than does the cementitious material content for GU-slag blends, the stream curing duration (16-24 hours), the type of cement used (high early (HE) or GU), and the steam curing temperature (60-70°C) [140-158°F].


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