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.

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.

scholarly journals Calcarreous Fly Ash Content Signifacence To Self-Terminating Carbonation Model Of Concrete

2018 ◽  
Vol 163 ◽  
pp. 05004
Author(s):  
Paweł Woliński ◽  
Piotr Woyciechowski ◽  
Grzegorz Adamczewski
Keyword(s):  
Fly Ash ◽  
Brown Coal ◽  
Ash Content ◽  
Accelerated Carbonation ◽  
Cement Ratio ◽  
Water To Cement Ratio ◽  
Technical Properties

Calcareous Ely Ash is a combustion by-product of Brown coal. Its technical properties depend on the combustion conditions – in the paper calcareous fly ash obtained from the traditional grate furnaces is considered. The presented paper shows the results of accelerated carbonation tests according to the draft of CEN / TS 12390-12 standard. The obtained models have self-terminating character. Concretes of water to cement ratio (w / c) from 0,35 to 0,55 and Ely Ash to cement ratio (p / c) from 0,2 to 0,5 were investigated.

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.

scholarly journals Surface Roughness and Porosity of Hydrated Cement Pastes

10.14311/1374 ◽  
2011 ◽  
Vol 51 (3) ◽  
Author(s):  
T. Ficker ◽  
D. Martišek ◽  
H. M. Jennings
Keyword(s):  
The Other ◽  
Porous Solids ◽  
Surface Irregularity ◽  
Hydrated Cement ◽  
Cement Pastes ◽  
Cement Ratio ◽  
Fracture Surfaces ◽  
Water To Cement Ratio ◽  
The One ◽  
Highly Porous

. Seventy-eight graphs were plotted to describe and analyze the dependences of the height and roughness irregularities on the water-to-cement ratio and on the porosity of the cement hydrates. The results showed unambiguously that the water-to-cement ratio or equivalently the porosity of the specimens has a decisive influence on the irregularities of the fracture surfaces of this material. The experimental results indicated the possibility that the porosity or the value of the water-to-cement ratio might be inferred from the height irregularities of the fracture surfaces. It was hypothesized that there may be a similarly strong correlation between porosity and surface irregularity, on the one hand, and some other highly porous solids, on the other, and thus the same possibility to infer porosity from the surfaces of their fracture remnants.

scholarly journals CO2 Curing Efficiency for Cement Paste and Mortars Produced by a Low Water-to-Cement Ratio

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3883
Author(s):  
Seong Ho Han ◽  
Yubin Jun ◽  
Tae Yong Shin ◽  
Jae Hong Kim
Keyword(s):  
Cement Paste ◽  
Pressure Vessel ◽  
Gas Pressure ◽  
Strength Development ◽  
Co2 Uptake ◽  
Cement Pastes ◽  
Co2 Gas ◽  
Cement Ratio ◽  
Mix Proportion ◽  
Water To Cement Ratio

Curing by CO2 is a way to utilize CO2 to reduce greenhouse gas emissions. Placing early-age cement paste in a CO2 chamber or pressure vessel accelerates its strength development. Cement carbonation is attributed to the quickened strength development, and CO2 uptake can be quantitatively evaluated by measuring CO2 gas pressure loss in the pressure vessel. A decrease in CO2 gas pressure is observed with all cement pastes and mortar samples regardless of the mix proportion and the casting method; one method involves compacting a low water-to-cement ratio mix, and the other method comprises a normal mix consolidated in a mold. The efficiency of the CO2 curing is superior when a 20% concentration of CO2 gas is supplied at a relative humidity of 75%. CO2 uptake in specimens with the same CO2 curing condition is different for each specimen size. As the specimen scale is larger, the depth of carbonation is smaller. Incorporating colloidal silica enhances the carbonation as well as the hydration of cement, which results in contributing to the increase in the 28-day strength.

Effects of Fly Ash Addition on Compressive Strength and Flexural Strength of Foamed Cement Composites

2013 ◽  
Vol 795 ◽  
pp. 664-668 ◽  
Author(s):  
Roshasmawi Abdul Wahab ◽  
Mohd Noor Mazlee ◽  
Shamsul Baharin Jamaludin ◽  
Khairul Nizar Ismail
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Flexural Strength ◽  
Cement Composites ◽  
Volume Percent ◽  
Foaming Agent ◽  
Cement Ratio ◽  
Water To Cement Ratio

In this study, the mixing of polystyrene (PS) beads and fly ash as a sand replacement material in foamed cement composites (FCC) has been investigated. Specifically, the mechanical properties such as compressive strength and flexural strength were measured. Different proportions of fly ash were added in cement composites to replace the sand proportion at 3 wt. %, 6 wt. %, 9 wt. % and 12 wt. % respectively. The water to cement ratio was fixed at 0.65 meanwhile ratios of PS beads used was 0.25 volume percent of samples as a foaming agent. All samples at different mixed were cured at 7 and 28 days respectively. Based on the results of compressive strength, it was found that the compressive strength was increased with the increasing addition of fly ash. Meanwhile, flexural strength was decreased with the increasing addition of fly ash up to 9 wt. %. The foamed cement composites with 12 wt. % of fly ash produced the highest strength of compressive strength meanwhile 3 wt. % of fly ash produced the highest strength of flexural strength.

scholarly journals Hydration processes of cement paste-an EPR study

2010 ◽  
Vol 7 (1) ◽  
pp. 215-219
Author(s):  
R. Gopalakrishnan ◽  
D. Govindarajan
Keyword(s):  
Setting Time ◽  
Electron Paramagnetic Resonance Study ◽  
Hydration Time ◽  
Time Intervals ◽  
Paramagnetic Resonance ◽  
Cement Pastes ◽  
Cement Ratio ◽  
Final Setting Time ◽  
Water To Cement Ratio ◽  
Electron Paramagnetic

The present works reports the hydration processes of Portland cement through Electron paramagnetic resonance study. Cement pastes in a Water to cement ratio (W/C) of 0.4 at different hydration time intervals have been prepared. The g-factor of Fe(III) and Mn(II) impurities at different hydration ages has been related to changes in setting time of cement. Both gFe and gMn values are reach a maximum values at final setting time of OPC paste.

Mechanical Properties of Reactive Powder Concrete Containing Fly Ash under Different Curing Regimes

2014 ◽  
Vol 597 ◽  
pp. 320-323 ◽  
Author(s):  
De Hong Wang ◽  
Yan Zhong Ju ◽  
Wen Zhong Zheng
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Flexural Strength ◽  
Ash Content ◽  
Reactive Powder Concrete ◽  
Steam Curing ◽  
Cement Ratio ◽  
Reactive Powder ◽  
Curing Regimes

Mechanical properties of reactive powder concrete (RPC) containing fly ash were investigated under different curing regimes (standard and steam curing) in this study. The experimental results indicate that, flexural strength of RPC increased considerably after steam curing, compared to the standard curing. Steam curing had no significant effect on compressive strength of RPC. Increasing the fly ash content improved the flexural strength of RPC under all curing regimes considerably. The compressive strength reached a maximum (103.8MPa) when the fly to ash and cement ratio is 0.3.

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.

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