Contribution of chemical hardening to strength gain of fly ash

2021 ◽  
pp. 35-41
Author(s):  
A.B. Fourie ◽  
G.E. Blight ◽  
N. Barnard
Keyword(s):  
Fly Ash ◽  
Strength Gain ◽  
Chemical Hardening

Empirical Prediction Models for Strength Gain Properties of Fly Ash Based Concrete Subjected to Accelerated Curing

2018 ◽  
Vol 1150 ◽  
pp. 73-90
Author(s):  
Vallarasu Manoharan Sounthararajan
Keyword(s):  
Fly Ash ◽  
Prediction Models ◽  
Pulse Velocity ◽  
Hot Water ◽  
Experimental Investigations ◽  
Strength Gain ◽  
Steam Curing ◽  
Empirical Prediction ◽  
Accelerated Curing ◽  
Water Curing

Experimental investigations on the early age, strength gain properties of fly ash blended cement concretes containing low and high volume fly ash replacement were studied. Concrete mixes were prepared with two different fly ash contents and varying concrete ingredients with water to binder ratio (w/b), fine to coarse aggregate ratio (F/c) and accelerator dosage. Five different curing techniques, namely controlled humidity curing; hot air oven curing, steam curing, hot water curing and normal water curing were adopted for curing the fly ash based concretes. Test results showed evidence the influence of accelerating admixtures and accelerated curing for obtaining the high early strength properties in fly ash mixed concrete. Most notably a maximum 1 day compressive strength of 40.20 MPa and 34.60 MPa with low (25%) and high (50%) volume fly ash concretes were obtained respectively in this study. Experimental results clearly indicated that the improvements on the strength gain properties with the careful selection of mix ingredients; accelerator addition and accelerated curing in fly ash based concrete mixes. Also, significant improvements on the flexural strength, elastic modulus, dynamic modulus and the ultrasonic pulse velocity test were noticed.

scholarly journals Shotcrete using ternary binder made from coal combustion products: from lab tests to an application

2021 ◽  
Vol 1205 (1) ◽  
pp. 012004
Author(s):  
Vít Šmilauer ◽  
Radoslav Sovják ◽  
Šárka Pešková ◽  
Rostislav Šulc ◽  
František Škvára ◽  
...  
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Coal Combustion ◽  
Combustion Products ◽  
Strength Gain ◽  
Hydration Products ◽  
Fluidized Bed Combustion ◽  
Space Filling ◽  
Coal Combustion Products ◽  
Fbc Fly Ash

Abstract The paper presents a ternary binder development and its utilization in shotcrete. The binder is made from fluidized bed combustion (FBC) fly ash, siliceous fly ash, and Ca(OH)2 addition, now available under the name Sorfix. XRD and TGA identified ettringite and C-S-H as two main hydration products. In addition, thermodynamic modeling verified robustness in terms of space-filling capabilities when varying input oxide composition. Since alkali-free accelerators produce mostly ettringite in Portland-based systems, a fraction of Portland cement was advantageously replaced with the ternary binder, forming early ettringite as well. Extensive testing led to 45% replacement of Portland cement, following J2 curve for early strength gain used commonly in shotcrete tunnel linings. The shotcrete was successfully tested in a mock-up experiment in a 2 m3 Prague served for the full-scale application, utilizing over 1000 tons of Sorfix and saving over 700 tons of CO2

Early Strength of Self-Compacting Concrete

2000 ◽  
Vol 1698 (1) ◽  
pp. 61-69
Author(s):  
David J. Mukai ◽  
Simten Altan ◽  
John Q. Ehrgott
Keyword(s):  
Fly Ash ◽  
Primary Objective ◽  
Strength Characteristics ◽  
Strength Gain ◽  
Slag Cement ◽  
Self Compacting Concrete ◽  
Steam Curing ◽  
External Vibration ◽  
Early Strength ◽  
Congested Areas

The researchers’ primary objective was to evaluate the early-strength characteristics of self-compacting concrete (SCC), which is a type of concrete that can be placed without external vibration, even in congested areas. Two unique characteristics of SCC are its high-percentage substitution of cement with fly ash or slag cement, or with both fly ash and slag cement and a relatively high superplasticizer dosage. Both of these characteristics retard early-strength gain. The impetus was to develop self-compacting concrete with an early strength suitable for precast applications. The major findings are that it is possible to proportion SCC mixtures with high early strength (30 MPa at 16 h under steam curing) and that high slump does not necessarily correlate with self-compaction.

Fly Ash As A Binder in Aggregate Base Courses

1987 ◽  
Vol 113 ◽  
Author(s):  
Petros Zenieris ◽  
Joakim G. Laguros
Keyword(s):  
Fly Ash ◽  
Moisture Content ◽  
Coarse Aggregate ◽  
Optimum Moisture Content ◽  
Dry Density ◽  
Strength Gain ◽  
Maximum Dry Density ◽  
High Calcium ◽  
High Calcium Fly Ash ◽  
Aggregate Base

ABSTRACTThe benefit of adding up to 35 wt% Class C high calcium fly ash to various types of fine and coarse aggregate pavement mixes is described and quantified. The mixes, which were compacted to maximum dry density at optimum moisture content, had variable compressive strengths during the first 28 days of curing; after that they assumed a relatively uniform pattern of strength gain reaching values as high as 11 MPa (1600 psi). Mixes containing 15% fly ash gave unacceptably low strengths. XRD measurements indicated massive formation of ettringite, transforming to monosulfoaluminate and the poorly crystallized hydrated phases of C-A-H, C-A-S-H and C-S-H. This transformation helps explain the gain in strength of the mixes with extended curing. SEM observations depicted progressive packing and densification of the skeletal matrix as the hexagonal phases and C-S-H gained higher crystallinity and formed aggregated masses. Furthermore, these observations suggest that fly ash acts predominantly as a chemical binder and partly as a filler in the aggregate mixes tested.

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.

scholarly journals Geotechnical Properties of Fly Ash and its Application on Soft Soil Stabilization

2010 ◽  
Vol 1 (2) ◽  
pp. 1-6 ◽  
Author(s):  
Emilliani Anak Geliga ◽  
Dygku Salma Awg Ismail
Keyword(s):  
Fly Ash ◽  
Soil Sample ◽  
Construction Industry ◽  
Soil Stabilization ◽  
Soft Soil ◽  
Geotechnical Properties ◽  
Industrial Wastes ◽  
Strength Gain ◽  
Construction Engineering ◽  
Local Construction

Soil stabilization has become the major issue in construction engineering and the researches regarding the effectiveness of using industrial wastes as a stabilizer are rapidly increasing. This paper briefly describes the suitability of the local fly ash to be used in the local construction industry in a way to minimize the amount of waste to be disposed to the environment causing environmental pollution. Several civil engineering laboratory tests are conducted to study the geotechnical properties of fly ash and strength gain when mixed with local clay sample. A different proportion of fly ash and soil sample cured for 7 days results in a strength gain. A better understanding of the properties of fly ash is gained from the study and the tests indicates an improved strength and better properties of soft soil sample when stabilized.

Advancements in Properties of Cement Containing Pulverised Fly Ash and Nanomaterials by Blending and Ultrasonication Method (Review - Part I)

2018 ◽  
Vol 19 ◽  
pp. 1-11 ◽  
Author(s):  
Mehmet Serkan Kirgiz
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Flexural Strength ◽  
Water Demand ◽  
Review Paper ◽  
Setting Time ◽  
Heat Of Hydration ◽  
Strength Gain ◽  
Hydration Properties ◽  
Carbon Nano Tube

This review research aims to discuss the results obtained researches on cement containing pure cement, pulverised fly ash, and nanoparticles, in order for eliminating negative side effects underlie the substitution of by–products for pure Portland cement. Nanoparticles (NP) used in these researches are nanoTiO2, nanoSiO2, nanoCaCO3, fibers of carbon nano tube (CNT), nanolimestone (nanoCaCO3), nanoZrO2, nanoclays, and nanometakaolin (nMK) for improving properties of cement systems. Published manuscripts explains two methods regarding on the usage of nanoparticles for cement system: blending and ultrasonication for dispersion of nanoparticles. However, differences between blending and ultrasonication methods suggested by various researchers are also discussed. Experiments reported these papers include the water demand, the density, the setting–times, the heat of hydration, the fluidity, the compressive strength and the flexural strength. According to these results, nanoparticles increase the water demand and heat of hydration of cement; it decreases the density and fluidity for cement mortars, evidently. The most effective nanoparticles on early compressive and flexural strengths are fibers of carbon nano tube and nanoCaCO3. These papers also point effects of these nanoparticles on the strength gain of cement. This review paper inform us until Effect of nanomaterial on water demand and density section in this Part I. Second part of this review paper will explain Hydration properties of Portland pulverised fly ash cement section, Effect of nanomaterial on setting–time section, Effect of nanomaterial on heat of hydration section, Strength gain mechanisms for hardened Portland pulverised fly ash cement paste and mortar section, Effect of nanomaterial on compressive strength section, Effect of nanomaterial on flexural strength (Bending) section, and Conclusion section.

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