Early-age strength development in fly ash blended cement composites: investigation through chemical activation

2019 ◽  
Vol 71 (5) ◽  
pp. 260-270 ◽  
Author(s):  
T. Hemalatha ◽  
Saptarshi Sasmal
Keyword(s):  
Fly Ash ◽  
Chemical Activation ◽  
Blended Cement ◽  
Strength Development ◽  
Early Age ◽  
Cement Composites

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

2013 ◽  
Vol 405-408 ◽  
pp. 2665-2670 ◽  
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

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

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.

Early Age Property Study of Phosphate Cement by Electrical Conductivity Measurement

2013 ◽  
Vol 544 ◽  
pp. 409-414
Author(s):  
Zhu Ding ◽  
Xiao Dong Wang ◽  
Bi Qin Dong ◽  
Zong Jin Li ◽  
Feng Xing
Keyword(s):  
Electrical Conductivity ◽  
Fly Ash ◽  
Temperature Rise ◽  
Conductivity Measurement ◽  
Maximum Temperature ◽  
Strength Development ◽  
Initial Reaction ◽  
Early Age ◽  
Electrical Conductivity Measurement ◽  
Hardening Process

The properties and electrical conductivity at early age of magnesium phosphate cement (MPC) was studied. Electrical resistivity or conductivity had been used for explaining the microstructure development of cement materials. In the current study, an electrodeless resistivity meter (ERM) was used to study the early property of MPC, which was mixed with and without fly ash respectively. The hardening process was investigated by the conductivity variation, incorporating with strength development and temperature rise during the initial reaction. The products and microstructure morphology of MPC paste were analysed by XRD and SEM. Results showed the mechanical property of MPC can be improved by fly ash. Fly ash lowers the maximum temperature rise during initial reaction of MPC with water. The electrical conductivity results divids the hardening process of MPC into three stages: acceleration, deceleration and stabilization. Conductivity measurement is an excellent method to explain the hardening process of MPC.

scholarly journals Dielectric Study on Fly Ash Blended Cement

2009 ◽  
Vol 6 (1) ◽  
pp. 231-236 ◽  
Author(s):  
G. Sivakumar ◽  
K. Mohanraj ◽  
S. Barathan
Keyword(s):  
Fly Ash ◽  
Ordinary Portland Cement ◽  
Setting Time ◽  
Blended Cement ◽  
Dielectric Measurement ◽  
Dielectric Study ◽  
Cement Composites ◽  
Distilled Water ◽  
Fly Ashes ◽  
Solid Ratio

In this paper, the hydration behaviour of ordinary portland cement (OPC) and fly ash blended cement (10, 25 and 40%) replaced by two different fly ashes (FA) were investigated. The samples were hydrated with distilled water (DW) in water to solid ratio 0:4 and its setting time and dielectric measurement are carried out. Results of the study found that the fly ash blended cement composites have slow hydration than OPC during early stages (up to 24 h).

Effect of Gypsum on Strength Development of Steam-Cured Concrete

2011 ◽  
Vol 194-196 ◽  
pp. 1085-1088
Author(s):  
Zhi Min He ◽  
Xiao Ju Shen ◽  
Jun Zhe Liu
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Strength Development ◽  
Early Age ◽  
Strength Gain ◽  
Fly Ashes ◽  
Steam Curing ◽  
Gain Rate ◽  
Early Strength ◽  
Chemical Activator

The use of fly ashes for cement-replacement purposes, especially in high volumes, decreases rate of early strength development of the steam curing concrete. To resolve it, this paper developed a new steam-cured concrete incorporating fly ash and a chemical activator (gypsum). Experiments were conducted to investigate the mechanical properties at early and later ages of steam and standard curing concretes. The corresponding mechanism was also discussed by testing the microstructure of concretes. Results indicate that the demoulding compressive strength of steam curing concrete with 4% gypsum dosage can meet production requirements, and compressive strength of this concrete at later ages increase well. Compared with that of ordinary pure cement steam-cured concrete, concrete with 4% gypsum has a higher compressive strength gain rate. At an early age, addition of the gypsum can distinctly accelerate the extent of hydration of the steam curing fly ash cement systems, and thus the microstructure of concrete becomes denser. However, in standard curing condtion, the effect of gypsum is not distinct.

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 Strength Development of Alkali-Activated Fly Ash Exposed to a Carbon Dioxide-Rich Environment at an Early Age

2016 ◽  
Vol 53 (1) ◽  
pp. 18-23 ◽  
Author(s):  
Sol-Moi Park ◽  
Jeong-Gook Jang ◽  
Gwang-Mok Kim ◽  
Haeng-Ki Lee
Keyword(s):  
Carbon Dioxide ◽  
Fly Ash ◽  
Strength Development ◽  
Early Age ◽  
Alkali Activated

scholarly journals Application of Slag–Cement and Fly Ash for Strength Development in Cemented Paste Backfills

Minerals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 22 ◽  
Author(s):  
Yue Zhao ◽  
Amin Soltani ◽  
Abbas Taheri ◽  
Murat Karakus ◽  
An Deng
Keyword(s):  
Fly Ash ◽  
Mechanical Performance ◽  
Blended Cement ◽  
Dry Mass ◽  
Strength Development ◽  
Unconfined Compression ◽  
Strength Criteria ◽  
Copper Gold ◽  
Paste Backfill ◽  
Solids Content

The present study investigates the combined capacity of a newly developed slag-blended cement (MC) and fly ash (FA) as a sustainable solution towards improving the mechanical performance of the cemented paste backfill (CPB) system of a copper-gold underground mine. A total of thirteen mix designs consisting of three MC-treated and ten MC + FA-treated blends were examined. Samples were prepared with a solids content of 77% (by total mass), and were allowed to cure for 7, 14, 28, 56 and 128 days prior unconfined compression testing. Scanning electron microscopy (SEM) studies were also carried out to observe the evolution of fabric in response to MC and MC + FA amendments. The greater the MC content and/or the longer the curing period, the higher the developed strength, toughness and stiffness. The exhibited improvements, however, were only notable up to 56 days of curing, beyond of which the effect of curing was marginal. The performance of 4% Portland cement or PC (by total dry mass) was found to be similar to that of 1.5% MC, while the higher MC inclusions of 2.5% and 3%, though lower in terms of binder content, unanimously outperformed 4% PC. The use of FA alongside MC improved the bonding/connection interface generated between the tailings aggregates, and thus led to improved mechanical performance compared with similar MC inclusions containing no FA. Common strength criteria for CPBs were considered to assess the applicability of the newly introduced MC and MC + FA mix designs. The mix designs “3% MC” and “2.5% MC + 2–2.5% FA” satisfied the 700 kPa strength threshold required for stope stability, and thus were deemed as optimum design choices.

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