Evaluation of early-age thermal cracking resistance of high w/b, high volume fly ash (HVFA) concrete using temperature stress testing machine

High-volume fly ash (HVFA) concretes are attractive not only because they reduce cement content and the associated greenhouse gases, but also because they avoid landfilling excessive quantities of fly ash. These sustainability benefits are often tempered by practical constructability limitations that may exist for HVFA concretes: retardation and diminution of the early-age reaction, delay in setting (and finishing operations), and lower early-age strength. This paper explores the alleviation of these deficiencies in HVFA mixtures by the incorporation of fine limestone powders into ternary blends. Isothermal calorimetry and Vicat needle penetration measurements are employed to assess reaction rates and setting times, respectively. A systematic variation of the content and fineness of the limestone powder in mixtures containing either a Class C or a Class F fly ash indicates that setting times are linearly correlated with the surface area supplied by the limestone. Comparison of a limestone system to a system containing an inert titanium dioxide of similar particle size indicates that the acceleration and amplification effects of the limestone can be attributed to both physical (nucleation) and chemical (additional calcium ions) processes. The results indicate that ternary blends with 40% of the cement by volume replaced by 30% to 35% fly ash and 5% to 10% limestone at a constant water volume fraction can be achieved without significant delay in setting.

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Nanosilica Activated High Volume Fly Ash Concrete: Effects on Selected Properties

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.722.157 ◽

2016 ◽

Vol 722 ◽

pp. 157-162 ◽

Cited By ~ 1

Author(s):

Martin Labaj ◽

Rudolf Hela ◽

Iveta Hájková

Keyword(s):

Fly Ash ◽

Raw Materials ◽

Water Pressure ◽

Construction Material ◽

High Volume ◽

Strength Development ◽

Early Age ◽

Fly Ash Concrete ◽

High Volume Fly Ash ◽

Static And Dynamic Moduli

By volume, there is no other material used as much as concrete. Its mechanical properties, durability and favorable price makes concrete the perfect construction material. In last few decades, we are seeing a growing trend of partial Portland cement’s replacement with secondary raw materials, most commonly with fly ash. So-called high volume fly ash (HVFA) concretes usually contains over 50% of it. While HVFA concrete’s long-term properties and price are improved over the classical one, its early age properties are often affected negatively. Here, a highly reactive pozzolans enters the scene. Materials like microsilica and metakaolin are known to accelerate concrete’s strength development and improve early age characteristics. In this paper, nanosilica is used for this purpose. These SiO2 nanoparticles possesses a much higher surface area and thus reactivity. Three mixtures with 0, 40 a 60% portland cement’s replacement with fly ash were prepared and tested with and without addition of small amount of nanosilica. Effects on compressive strength, static and dynamic moduli of elasticity and resistivity against water pressure were observed. Results clearly demonstrates that even with dosage in the range of tenths of percent, nanosilica can significantly improve concrete’s properties.

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Thermal Cracking Resistance of Shotcrete Based on Temperature Matched Curing

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.391-392.849 ◽

2011 ◽

Vol 391-392 ◽

pp. 849-853

Author(s):

Bo Chen ◽

Jian Tong Ding ◽

Yue Bo Cai ◽

Qiu Bo Kang

Keyword(s):

Stress Testing ◽

Testing Machine ◽

Thermal Cracking ◽

Test Method ◽

Test Results ◽

Cracking Resistance ◽

Different Types ◽

Practical Temperature ◽

The Difference ◽

Cracking Tendency

In order to evaluate the thermal cracking resistance of shotcrete under the condition of practical temperature field and strong restrain, a proper test method is needed. Based on temperature matched curing and by applying temperature stress testing machine, a new test method has been provided. With the application of this test method, thermal cracking resistance of three shotcretes with different types of fiber were investigated. Test results show that the cracking tendency of different shotcretes can be distinguished with the parameter of the difference between the max temperature and the cracking temperature.

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Early age assessment of cement mortar incorporated high volume fly ash

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/1090/1/012019 ◽

2021 ◽

Vol 1090 (1) ◽

pp. 012019

Author(s):

Dhoha Saad Hanoon ◽

Ali Kadhim Sallal ◽

Ali A. Shubbar ◽

Zainab S. Al-Khafaji ◽

Mohammed Salah Nasr ◽

...

Keyword(s):

Fly Ash ◽

Cement Mortar ◽

High Volume ◽

Early Age ◽

Age Assessment ◽

High Volume Fly Ash

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Use of gypsum and CKD to enhance early age strength of High Volume Fly Ash (HVFA) pastes

Construction and Building Materials ◽

10.1016/j.conbuildmat.2014.08.015 ◽

2014 ◽

Vol 71 ◽

pp. 93-108 ◽

Cited By ~ 20

Author(s):

Dali Bondar ◽

Eoin Coakley

Keyword(s):

Fly Ash ◽

High Volume ◽

Early Age ◽

High Volume Fly Ash

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Early-age Properties of High-volume Fly Ash Concrete Mixes for Pavement: Volume 2

10.36501/0197-9191/21-031 ◽

2021 ◽

Author(s):

Aniruddha Baral ◽

◽

Jeffery Roesler ◽

Junryu Fu ◽

◽

...

Keyword(s):

Fly Ash ◽

Setting Time ◽

High Volume ◽

Early Age ◽

X Ray ◽

Fly Ash Concrete ◽

Setting Times ◽

Chemical Admixtures ◽

High Volume Fly Ash ◽

Foam Index

High-volume fly ash concrete (HVFAC) is more cost-efficient, sustainable, and durable than conventional concrete. This report presents a state-of-the-art review of HVFAC properties and different fly ash characterization methods. The main challenges identified for HVFAC for pavements are its early-age properties such as air entrainment, setting time, and strength gain, which are the focus of this research. Five fly ash sources in Illinois have been repeatedly characterized through x-ray diffraction, x-ray fluorescence, and laser diffraction over time. The fly ash oxide compositions from the same source but different quarterly samples were overall consistent with most variations observed in SO3 and MgO content. The minerals present in various fly ash sources were similar over multiple quarters, with the mineral content varying. The types of carbon present in the fly ash were also characterized through x-ray photoelectron spectroscopy, loss on ignition, and foam index tests. A new computer vision–based digital foam index test was developed to automatically capture and quantify a video of the foam layer for better operator and laboratory reliability. The heat of hydration and setting times of HVFAC mixes for different cement and fly ash sources as well as chemical admixtures were investigated using an isothermal calorimeter. Class C HVFAC mixes had a higher sulfate imbalance than Class F mixes. The addition of chemical admixtures (both PCE- and lignosulfonate-based) delayed the hydration, with the delay higher for the PCE-based admixture. Both micro- and nano-limestone replacement were successful in accelerating the setting times, with nano-limestone being more effective than micro-limestone. A field test section constructed of HVFAC showed the feasibility and importance of using the noncontact ultrasound device to measure the final setting time as well as determine the saw-cutting time. Moreover, field implementation of the maturity method based on wireless thermal sensors demonstrated its viability for early opening strength, and only a few sensors with pavement depth are needed to estimate the field maturity.

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