Early-age behaviour and cracking potential of fly ash concrete under restrained condition

Initial cracks due to volume changes at an early age affect the durability of concrete structures, so numerical simulations are often conducted in order to predict cracks. Such prediction requires some mechanical properties of early age concrete. Tensile Young's modulus is directly dependent on the prediction of tensile stress and is one of the important input data for FEM analysis. However, direct tension test for tensile Young's modulus needs a unique apparatus and specimen, and such test is not suitable for evaluating Young's modulus at early ages of concrete. The present study compared tensile Young's modulus with compressive Young's moduli of Fly ash concrete. Compressive Young's moduli used in this study were secant modulus and initial tangent modulus. In addition, linear modulus taken from a regression line of a compressive stress-strain curve in the range of stresses less than the splitting tensile strength was also evaluated. It is found that the secant modulus, which is generally used as Young's modulus in Japan was clearly smaller than the tensile Young's modulus, which means that, tensile stresses evaluated using a secant modulus might be underestimated. On the other hand, linear modulus and initial tangent modulus were almost equal to the tensile Young's modulus. This result indicates that tensile stresses can be evaluated using Young's modulus obtained from a compression test with general apparatus and specimens.

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Fly-Ash Concretes of 50% of the Replacement Ratio to Reduce the Cracking in Concrete Structures

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.405-408.2665 ◽

2013 ◽

Vol 405-408 ◽

pp. 2665-2670 ◽

Cited By ~ 1

Author(s):

Ming Jie Mao ◽

Qiu Ning Yang ◽

Wen Bo Zhang ◽

Isamu Yoshitake

Keyword(s):

Fly Ash ◽

Concrete Structures ◽

High Volume ◽

Pozzolanic Reaction ◽

Strength Development ◽

Early Age ◽

Replacement Ratio ◽

Fly Ash Concrete ◽

Massive Concrete ◽

Normal Strength

Fly-ash concrete used in massive concrete structure has superior advantages to reduce hydration heat. On the other hand, the fly-ash concrete has negative property of low strength development at early age because pozzolanic reaction of fly-ash activates at mature age, such as after 28 days. To investigate these characteristics of fly-ash used in concrete, the present study discusses thermal cracking possibility of fly-ash concrete by using FE analysis software. The present study employs prediction formulae proposed by Zhang and Japanese design code in the simulations. The objects in this study are normal strength concrete mixed of fly-ash up to 50% of replacement ratio to cement. The comparative investigations show that temperature effect is more significant than strength development at early age. Based on the analytical study, high volume fly-ash concretes of 30-50% of the replacement ratio can be concluded as effective and useful materials to reduce the cracking possibility in massive concrete structures. Keywords-Fly-ash concrete; Early Age, Prediction Formulae for Strength; Thermal Stress Analysis

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Proposal of a Simplified Prediction Formula for Compressive Strength of Fly Ash Concrete

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.287-290.1201 ◽

2011 ◽

Vol 287-290 ◽

pp. 1201-1208 ◽

Cited By ~ 2

Author(s):

Wen Bo Zhang ◽

Isamu Yoshitake ◽

Tadashi Saitoh

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Early Age ◽

Strength Ratio ◽

Prediction Formula ◽

Replacement Ratio ◽

Fly Ash Concrete ◽

Wide Range ◽

Water Ratio ◽

Simplified Formula

To propose a prediction formula of compressive strength of concretes containing fly ash (FA concrete), over 1600 strength data are collected from previous studies and discussed in this study. In particular, the study focuses on developing strengths of FA concrete. The study deals with test data of concrete with wide range of FA replacement, namely 0-50% by mass of cement. Compressive strength at age of 7 days has strongly relation to the cement-water ratio, so the strength can be predicted by using only water and cement contents. In addition, early age strengths within 7 days can be estimated by using the Goral curve based on strength ratio. Strength after the age of 7 days can be predicted by using replacement ratio of fly ash because the strength ratios are proportional to the replacement ratio. Based on the findings, a simplified formula for predicting compressive strength at various ages is proposed in the paper.

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Influence of Concrete Sludge Addition in the Properties of Alkali-Activated and Non-Alkali-Activated Fly Ash-Based Mortars

Advances in Civil Engineering ◽

10.1155/2021/5534002 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Fotini Kesikidou ◽

Stavroula Konopisi ◽

Eleftherios K. Anastasiou

Keyword(s):

Fly Ash ◽

Silicon Oxide ◽

Strength Development ◽

Alkali Activation ◽

Early Age ◽

Fly Ash Concrete ◽

High Calcium ◽

High Calcium Fly Ash ◽

Potential Synergy ◽

Alkali Activated

This study investigated the use of concrete sludge, a by-product of the ready-mix concrete industry, in combination with high-calcium fly ash in binary cementless binders. Concrete sludge was used in substitution rates ranging from 0% to 60% in test fly ash-based mortars to determine potential synergy. The mortars were tested for fresh and hardened properties; workability, viscosity, strength development, open porosity, early-age shrinkage, and analytical tests were carried out. A mortar with 50% fly ash and 50% limestone filler as binders was used for comparison purposes. Furthermore, a series of mortars with fly ash and concrete sludge were alkali-activated in order to determine potential strength gain. In the activated mortars, two fractions of concrete sludge were used, under 75 μm and 200 μm, due to different silicon oxide contents, while one mortar was cured at 40°C to investigate the effect of heating on alkali activation. Results show that sludge contributes to the formation of C-S-H and strength development when used in combination with high-calcium fly ash even at high replacement rates. The alkali activation of fly ash-concrete sludge system contributed to early-age strength development and to early-age shrinkage reduction.

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Sustainable cementitious materials: The effect of fly ash percentage as a part replacement of portland cement composite (PCC) and curing temperature on the early age strength of fly ash concrete

MATEC Web of Conferences ◽

10.1051/matecconf/201925801001 ◽

2019 ◽

Vol 258 ◽

pp. 01001

Author(s):

Gidion Turuallo ◽

Harun Mallisa

Keyword(s):

Fly Ash ◽

Portland Cement ◽

Cement Composite ◽

Cementitious Materials ◽

Curing Temperature ◽

Early Age ◽

Water Tank ◽

Lower Strength ◽

Fly Ash Concrete ◽

Lower Temperature

This research aims to determine the effect of fly ash percentage as a part replacement of Portland cement and curing temperatures to the early age strength of concrete. The percentages of fly ash used were 0, 10 and 15% by cement weight. The cured temperatures were 25, 30 dan 50°C. The concrete specimens were cubes of 150 x 150 x 150 mm3. The cubes, which were cured at 25°C, placed in water tank, while those cured at 30 and 50°C cured in oven until 7 days and then continued in water. The testing was conducted at ages 3, 7, 14 dan 28 days. The results showed that at early ages, the strength of concrete without fly ash cured at 25°C were higher than that of fly ash concrete. The higher level replacement of cement with fly ash, the lower strength of concrete obtained. The higher the curing temperature at earlier age resulted the higher the strength of concrete. The strength of concretes with 10% of fly ash cured at 25, 30 and 50°C at age three days were 15.111, 15.481 and 16.296 MPa respectively. Conversely, the strength of concrete that of cured at higher temperatures at ages 28 days, were lower than that of concretes cured at lower temperature. The results of this research also showed that fly ash could improve the workability of concrete.

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Improvement of Early-Age Strength of High-Volume Siliceous Fly Ash Concrete with Nanosilica - A Review

Advances in Civil Engineering Materials ◽

10.1520/acem20180065 ◽

2018 ◽

Vol 7 (1) ◽

pp. 20180065 ◽

Cited By ~ 3

Author(s):

Lincy Varghese ◽

V. V. L. Kanta Rao ◽

Lakshmy Parameswaran

Keyword(s):

Fly Ash ◽

High Volume ◽

Early Age ◽

Fly Ash Concrete

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Quality Control of Fly-Ash Concrete Strength at early Age and Evaluation Application Research

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.450-451.782 ◽

2012 ◽

Vol 450-451 ◽

pp. 782-785

Author(s):

Hui Niu

Keyword(s):

Quality Control ◽

Fly Ash ◽

Concrete Strength ◽

Early Age ◽

Application Research ◽

Fly Ash Concrete ◽

Improve Accuracy ◽

Concrete Quality ◽

Mixing Proportion

This manuscript briefly introduces an engineering example.The method of fly-ash concrete presumption at early age is used in mixing proportion design. we can control concrete quality and improve accuracy of the early evaluating presumption concrete among measures and results.

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Uniaxial tensile strength and tensile Young’s modulus of fly-ash concrete at early age

Construction and Building Materials ◽

10.1016/j.conbuildmat.2012.11.022 ◽

2013 ◽

Vol 40 ◽

pp. 514-521 ◽

Cited By ~ 10

Author(s):

Isamu Yoshitake ◽

Wenbo Zhang ◽

Yoichi Mimura ◽

Tadashi Saito

Keyword(s):

Tensile Strength ◽

Fly Ash ◽

Young’S Modulus ◽

Young's Modulus ◽

Uniaxial Tensile ◽

Early Age ◽

Uniaxial Tensile Strength ◽

Fly Ash Concrete

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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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