Creep and thermal cracking of ultra-high volume fly ash mass concrete at early age

2019 ◽  
Vol 99 ◽  
pp. 191-202 ◽  
Author(s):  
Zhifang Zhao ◽  
Kejin Wang ◽  
David A. Lange ◽  
Hougui Zhou ◽  
Weilun Wang ◽  
...  
Keyword(s):  
Fly Ash ◽  
Thermal Cracking ◽  
High Volume ◽  
Early Age ◽  
Mass Concrete ◽  
High Volume Fly Ash

Effects of calcium formate on early-age strength and microstructure of high-volume fly ash cement systems

2021 ◽  
pp. 1-13
Author(s):  
Zhiyuan Zhou ◽  
Massoud Sofi ◽  
Aocheng Zhong ◽  
Amin Shahpasandi ◽  
Marvel Cham Sarabia ◽  
...  
Keyword(s):  
Fly Ash ◽  
High Volume ◽  
Early Age ◽  
High Volume Fly Ash ◽  
Calcium Formate

Very High Volume Fly Ash Cements. Early Age Hydration Study Using Na2 SO4 as an Activator

2013 ◽  
Vol 96 (3) ◽  
pp. 900-906 ◽  
Author(s):  
Shane Donatello ◽  
Ana Fernández-Jimenez ◽  
Angel Palomo
Keyword(s):  
Fly Ash ◽  
High Volume ◽  
Early Age ◽  
High Volume Fly Ash ◽  
Early Age Hydration ◽  
Very High

Reducing Set Retardation in High-Volume Fly Ash Mixtures with the Use of Limestone

2012 ◽  
Vol 2290 (1) ◽  
pp. 139-146 ◽  
Author(s):  
Lisa R. Gurney ◽  
Dale P. Bentz ◽  
Taijiro Sato ◽  
W. Jason Weiss
Keyword(s):  
Fly Ash ◽  
Volume Fraction ◽  
High Volume ◽  
Reaction Rates ◽  
Limestone Powder ◽  
Water Volume ◽  
Early Age ◽  
Ternary Blends ◽  
Setting Times ◽  
High Volume Fly Ash

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.

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

2016 ◽  
Vol 722 ◽  
pp. 157-162 ◽  
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.

scholarly journals Early age assessment of cement mortar incorporated high volume fly ash

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

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

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.

scholarly journals A Review on Early Age and Long-term Compressive Strength of High-volume Fly Ash Concrete

2018 ◽  
Vol 207 ◽  
pp. 01004
Author(s):  
Mu Li
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
High Volume ◽  
Partial Replacement ◽  
Early Age ◽  
Fly Ash Concrete ◽  
Power Stations ◽  
High Volume Fly Ash ◽  
Curing Age

Fly ash is a by-product of the combustion of the coal-fired electric power stations, and disposal of fly ash has been one of the environmental challenges. Much of the studies have been focused on the mechanical property of fly ash concrete. It is no doubt that the use of high-volume fly ash as a partial replacement of cement is also one of the effect way to utilize fly ash. It is known that the compressive strength of fly ash concrete is lower than that of ordinary concrete at early age, especially for high-volume fly ash concrete. It is urgent for engineers to consider the compressive strength of high-volume fly ash concrete at different curing age. In this review, the compressive strength of high-volume fly ash concrete in various literature was reported and then analyzed. Furthermore, the proposal of the utilization of high-volume fly ash concrete is provided.

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