Assessment of Hydration Degree of Cement in the Fly Ash-Cement Pastes Based on the Calcium Hydroxide Content

2014 ◽  
Vol 875-877 ◽  
pp. 177-182 ◽  
Author(s):  
Xiang Li ◽  
Hua Quan Yang ◽  
Ming Xia Li
Keyword(s):  
Fly Ash ◽  
Calcium Hydroxide ◽  
Cement Hydration ◽  
Ash Content ◽  
Content Increase ◽  
Hydration Degree ◽  
Equilibrium Calculation ◽  
Cement Pastes ◽  
Cement Ratio ◽  
Water Cement Ratio

The hydration degree of fly ash and the calcium hydroxide (CH) content were measured. Combined with the equilibrium calculation of cement hydration, a new method for assessment of the hydration degree of cement in the fly ash-cement (FC) pastes based on the CH content was developed. The results reveal that as the fly ash content increase, the hydration degree of fly ash and the CH content decrease gradually; at the same time, the hydration degree of cement increase. The hydration degree of cement in the FC pastes containing a high content of fly ash (more than 35%) at 360 days is as high as 80%, even some of which hydrates nearly completely. The effect of water-cement ratio to the hydration degree of cement in the FC pastes is far less distinct than that of the content of fly ash.

Cement Hydration Models Research Based on Composition Content of each Phase of Minerals

2012 ◽  
Vol 204-208 ◽  
pp. 3639-3643
Author(s):  
Chun Hua Rao ◽  
Lang Wu ◽  
Bin Lei
Keyword(s):  
Cement Hydration ◽  
Curing Temperature ◽  
Kinetics Model ◽  
Hydration Degree ◽  
Hydration Kinetics ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Hydration Rate ◽  
Chemical Phase ◽  
Temperature Water

Abstract: Based on the cement hydration kinetics model proposed by R.Berliner, taking into account the factors such as each chemical phase of minerals, curing temperature, water-cement ratio, the final hydration degree and fineness of cement, a theoretical hydration kinetics equations was established in this paper. It can be used to predict the hydration rate and the change of hydration degree.

Survey on Factors Affecting Impermeability of Waterproof Concrete

2011 ◽  
Vol 250-253 ◽  
pp. 1320-1323
Author(s):  
Yi Jin Li ◽  
Yun Li Gong ◽  
Jian Yin
Keyword(s):  
Fly Ash ◽  
Ash Content ◽  
Raw Material ◽  
Factors Affecting ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Mix Proportion

This paper describes the influence of raw material, water-cement ratio, sand ratio, cement-sand ratio and fly ash content on impermeability of waterproof concrete. The value ranges of several important mix parameters are summarized, that provides the reference to select the parameters of mix proportion of waterproof concrete for subway.

Experimental Study on Carbonation Resistance of Ready-Mixed Concrete

2012 ◽  
Vol 174-177 ◽  
pp. 152-158 ◽  
Author(s):  
Jing Song Zhu ◽  
Ya Li Sun ◽  
Yue Feng Zhu ◽  
Dan Fei Chen
Keyword(s):  
Fly Ash ◽  
Service Life ◽  
Early Stage ◽  
Ash Content ◽  
Design Criteria ◽  
Carbonation Depth ◽  
Curing Conditions ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Carbonation Resistance

By means of accelerated carbonation tests, the carbonation resistance of concrete in relation to the variation of water-cement ratio, fly ash content and curing conditions is studied in this article. The results show that under the standard curing conditions, with the fly ash content of 20%, in response to different water-cement ratio, the carbonation depth of concrete and the water-cement ratio are presented more or less in a linear relationship. At the water-cement ratio of 0.40, there is hardly any carbonation effect onto the concrete. However, at the ratio of bigger than 0.60, the carbonation depth of concrete increases in a speedy way. Under the standard curing conditions, at the water-cement ratio of 0.55, with the fly ash content of lower than or equal to 30%, the carbonation resistance of concrete is good enough to fulfill the design criteria of 50~100 years for service life of important and general buildings, while the compressive strength declines by less than 10%. But under the condition of 1d curing with retention of moisture followed by curing in the air until 28d, with no fly ash content, the carbonation depth of concrete has reached 35mm, which fails to fulfill the design criteria of 50 years for service life of general buildings. It is therefore concluded that the control of water-cement ratio, the control of fly ash content, and the sufficient curing with retention of moisture in early stage are all the essential factors to ensure the durability against carbonation for the concrete with fly ash content.

Effect of Fly Ash Incorporation on Rheology of Cement Pastes

1986 ◽  
Vol 86 ◽  
Author(s):  
M. Rattanussorn ◽  
D. M. Roy ◽  
R. I. A. Malek
Keyword(s):  
Fly Ash ◽  
Chemical Composition ◽  
Zeta Potential ◽  
Spherical Shape ◽  
Ash Content ◽  
Type I ◽  
Special Effect ◽  
Cement Pastes ◽  
Cement Ratio ◽  
Water To Cement Ratio

ABSTRACTThe predominant spherical shape of fly ash particles combined with mainly glassy composition and texture of its surfaces have a special effect on rheology of cement pastes containing fly ash. The early ages rheological behavior of cement pastes (ASTM Type I) incorporating 30% low-calcium fly ash was monitored by measuring viscosity of the fresh pastes prior to initial hardening and stiffening (up to −2 hours) as a function of time. The viscosities were determined using a co-axial rotoviscometer (HAAKE). The effects of fly ash content, water to cement ratio, and presence and concentration of superplasticizer, were evaluated. In addition, the dispersivity of fly ash spheres was evaluated by determining the zeta-potential of fly ash suspensions in water using a microelectrophoresis technique and the results were correlated to the chemical composition of fly ash as well as the viscosities of fresh pastes.

High Volume Slag and Slag-Fly Ash Blended Cement Pastes Containing Nano Silica

2019 ◽  
Vol 967 ◽  
pp. 205-213
Author(s):  
Faiz U.A. Shaikh ◽  
Anwar Hosan
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Cement Paste ◽  
Ordinary Portland Cement ◽  
Blended Cement ◽  
High Volume ◽  
Ash Content ◽  
Partial Replacement ◽  
Nano Silica ◽  
Cement Pastes

This paper presents the effect of nanosilica (NS) on compressive strength and microstructure of cement paste containing high volume slag and high volume slag-fly ash blend as partial replacement of ordinary Portland cement (OPC). Results show that high volume slag (HVS) cement paste containing 60% slag exhibited about 4% higher compressive strength than control cement paste, while the HVS cement paste containing 70% slag maintained the similar compressive strength to control cement paste. However, about 9% and 37% reduction in compressive strength in HVS cement pastes is observed due to use of 80% and 90% slag, respectively. The high volume slag-fly ash (HVSFA) cement pastes containing total slag and fly ash content of 60% exhibited about 5%-16% higher compressive strength than control cement paste. However, significant reduction in compressive strength is observed in higher slag-fly ash blends with increasing in fly ash contents. Results also show that the addition of 1-4% NS improves the compressive strength of HVS cement paste containing 70% slag by about 9-24%. However, at higher slag contents of 80% and 90% this improvement is even higher e.g. 11-29% and 17-41%, respectively. The NS addition also improves the compressive strength by about 1-59% and 5-21% in high volume slag-fly ash cement pastes containing 21% fly ash+49%slag and 24% fly ash+56%slag, respectively. The thermogravimetric analysis (TGA) results confirm the reduction of calcium hydroxide (CH) in HVS/HVSFA pastes containing NS indicating the formation of additional calcium silicate hydrate (CSH) gels in the system. By combining slag, fly ash and NS in high volumes e.g. 70-80%, the carbon footprint of cement paste is reduced by 66-76% while maintains the similar compressive strength of control cement paste. Keywords: high volume slag, nanosilica, compressive strength, TGA, high volume slag-fly ash blend, CO2 emission.

Microstructure of High Strength Cement Paste Systems

1984 ◽  
Vol 42 ◽  
Author(s):  
M. Regourd
Keyword(s):  
Cement Paste ◽  
Ultrafine Particles ◽  
High Strength ◽  
Interfacial Bond ◽  
Cement Pastes ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Composite Systems ◽  
Crystalline Hydrates ◽  
Low Porosity

AbstractHigh strength cement pastes include hot pressed, autoclaved, impregnated low water/cement ratio, macrodefect free, ultrafine particles arrangement systems. The densification of the microstrucure is mainly related to a low porosity and to the formation of poorly crystalline hydrates. In composite systems like mortars and concretes, the interfacial bond between the cement paste and aggregates is moreover less porous and more finely crystallized than the normal “auréole de transition”.

scholarly journals Effect of Nanosilica on Impermeability of Cement-Fly Ash System

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Huaqing Liu ◽  
Yan Zhang ◽  
Ruiming Tong ◽  
Zhaoqing Zhu ◽  
Yang Lv
Keyword(s):  
Fractal Dimension ◽  
Fly Ash ◽  
Bond Strength ◽  
Pore Structure ◽  
Calcium Hydroxide ◽  
Cement Hydration ◽  
Pozzolanic Reaction ◽  
Surface Protection ◽  
Durability Of Concrete

Surface protection has been accepted as an effective way to improve the durability of concrete. In this study, nanosilica (NS) was used to improve the impermeability of cement-fly ash system and this kind of material was expected to be applied as surface protection material (SPM) for concrete. Binders composed of 70% cement and 30% fly ash (FA) were designed and nanosilica (NS, 0–4% of the binder) was added. Pore structure of the paste samples was evaluated by MIP and the fractal dimension of the pore structure was also discussed. Hydrates were investigated by XRD, SEM, and TG; the microstructure of hydrates was analyzed with SEM-EDS. The results showed that in the C-FA-NS system, NS accelerated the whole hydration of the cement-FA system. Cement hydration was accelerated by adding NS, and probably, the pozzolanic reaction of FA was slightly hastened because NS not only consumed calcium hydroxide by the pozzolanic reaction to induce the cement hydration but also acted as nucleation seed to induce the formation of C-S-H gel. NS obviously refined the pore structure, increased the complexity of the pore structure, and improved the microstructure, thereby significantly improving the impermeability of the cement-FA system. This kind of materials would be expected to be used as SPM; the interface performance between SPM and matrix, such as shrinkage and bond strength, and how to cast it onto the surface of matrix should be carefully considered.

Influence of the Fly-Ash Content of Concrete at Low Water-Binder Ratio on Hydration Degree of Binders and Cement

2011 ◽  
Vol 250-253 ◽  
pp. 445-449
Author(s):  
Li Wei Xu ◽  
Jian Lan Zheng
Keyword(s):  
Fly Ash ◽  
Temperature Rise ◽  
High Performance Concrete ◽  
Ash Content ◽  
Adiabatic Temperature ◽  
Mineral Admixture ◽  
Hydration Degree ◽  
Adiabatic Temperature Rise ◽  
Binder Ratio ◽  
Water Binder Ratio

The hydration degree of binders and cement is investigated by measuring the adiabatic- temperature rise of concrete at low water-binder ratio with different fly-ash content. The results denote that, with a constant water-binder ratio, both of the hydration degree of binders and that of cement decrease with the increasing fly-ash content in the early stage. In a later stage, however, the hydration degree of cement increases with the increasing fly-ash content and the hydration degree of binders peaks when the fly-ash content is 35%. Fly ash is one of the mineral admixture of which high-performance concrete is made up. It brings down the rise of concrete temperature significantly and helps solve the problems of shrinkage and crack of concrete structure. Because the hydration mechanism in common concrete is different from that in concrete with low water-binder ratio, and the hydration environment is different between concrete and cement pastes, to determine the adiabatic-temperature rise of concrete directly conforms to the actual situation. The adiabatic-temperature rise, adiabatic-temperature-rise rate, hydration degree of both binders and cement are investigated by measuring adiabatic-temperature rise of concrete with different fly-ash content.

Experiment Research on Plastic Strength of Grouting Materials of Desulfurization Denitration Ash

2013 ◽  
Vol 275-277 ◽  
pp. 2093-2096
Author(s):  
Hong Hai Zhang ◽  
Ai Min Gong ◽  
Chun Yan Wang
Keyword(s):  
Fly Ash ◽  
Silicon Powder ◽  
Calculation Formula ◽  
Experiment Research ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Plastic Strength ◽  
Two Factors ◽  
Grouting Materials

Derived calculation formula of plastic strength, and used mortar consistency instrument to determine plastic strength. Through experiment, the fly ash and silicon powder that desulfurized or denitrated as grouting materials, its change rules of plastic strength were studid under different water cement ratio and different dosage conditions. Results shows that, between the two factors of water cement ratio and dosage, the water cement ratio affect significantly the plastic strength. The smaller the water cement ratio, the more obvious the increase of the plastic strength as time growth. Early plastic strength of silicon powder grouts is growing rapidly.

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