scholarly journals Effect of Boron and Water-to-Cement Ratio on the Performances of Laboratory Prepared Belite-Ye’elimite-Ferrite (BYF) Cements

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4862
Author(s):  
Raquel Pérez-Bravo ◽  
Alejandro Morales-Cantero ◽  
Margherita Bruscolini ◽  
Miguel A. G. Aranda ◽  
Isabel Santacruz ◽  
...  
Keyword(s):  
Particle Size ◽  
Rietveld Method ◽  
Phase Assemblage ◽  
Calorimetric Study ◽  
Cement Ratio ◽  
Degree Of Hydration ◽  
Rheological Measurements ◽  
Water To Cement Ratio ◽  
Mechanical Strengths ◽  
Heat Released

The effect of superplasticiser, borax and the water-to-cement ratio on BYF hydration and mechanical strengths has been studied. Two laboratory-scale BYF cements—st-BYF (with β-C2S and orthorhombic C4A3S¯) and borax-activated B-BYF (with α’H-C2S and pseudo-cubic C4A3S¯)—have been used, and both show similar particle size distribution. The addition of superplasticiser and externally added borax to BYF pastes has been optimised through rheological measurements. Optimised superplasticiser contents (0.3, 0.4 and 0.1 wt % for st-BYF, B-BYF and st-BYF with externally added 0.25 wt % B2O3, respectively) result in low viscosities yielding homogeneous mortars. The calorimetric study revealed that st-BYF is more reactive than B-BYF, as the values of heat released are 300–370 J/g and 190–210 J/g, respectively, after 7 days of hydration; this fact is independent of the water-to-cement ratio. These findings agree with the higher degree of hydration at 28 days of β-C2S in st-BYF (from 45 to 60%) than α’H-C2S in B-BYF (~20 to 30%). The phase assemblage evolution has been determined by LXRPD coupled with the Rietveld method and MAS-NMR. The formation of stratlingite is favoured by increasing the w/c ratio in both systems. Finally, the optimisation of fresh BYF pastes jointly with the reduction of water-to-cement ratio to 0.40 have allowed the achieving of mortars with compressive strengths over 40 MPa at 7 days in all systems. Moreover, the st-BYF mortar, where borax was externally added, achieved more than 70 MPa after 28 days. The main conclusion of this work does not support Lafarge’s approach of adding boron/borax to the raw meal of BYF cements. This procedure stabilises the alpha belite polymorph, but its reactivity, in these systems, is lower and the associated mechanical strengths poorer.

scholarly journals Influence of cement replacement with limestone filler on the properties of concrete

2021 ◽  
Vol 64 (3) ◽  
pp. 165-170
Author(s):  
Ksenija Tešić ◽  
Snežana Marinković ◽  
Aleksandar Savić
Keyword(s):  
Particle Size ◽  
Compressive Strength ◽  
Mineralogical Composition ◽  
Limestone Filler ◽  
Green Concrete ◽  
Cement Ratio ◽  
Cement Replacement ◽  
Concrete Mixtures ◽  
Water To Cement Ratio ◽  
Compressive Strength Of Concrete

This paper presents an experimental research of one type of green concrete in which Portland cement was replaced with two types of limestone filler of the same origin and mineralogical composition, but with a different fineness of particles. Ten concrete mixtures were designed in which 0%, 15%, 30% and 45% (by mass) of cement were replaced with filler. The water to cement ratio for each mixture was constant (w/c=0.54), and the water to powder ratio was decreasing with increasing cement replacement. Particle size distribution was selected using Funk and Dinger, as well as using Fuller's model. The results showed that it is possible to increase the compressive strength of concrete by reducing 45% of cement, but further research should be focused on improving the workability.

The Quantitative Calculation the Volume Fraction of Cement Pastes

2010 ◽  
Vol 168-170 ◽  
pp. 156-160
Author(s):  
Zhi Yong Liu ◽  
Yun Sheng Zhang ◽  
Guo Wen Sun
Keyword(s):  
Volume Fraction ◽  
Cement Pastes ◽  
Volume Percentage ◽  
Cement Ratio ◽  
Degree Of Hydration ◽  
Quantitative Calculation ◽  
Water To Cement Ratio ◽  
Saturated Density ◽  
Experimental Values ◽  
Creep And Shrinkage

The knowledge of the microstructure is a point of major importance to understand the transport, mechanics, creep and shrinkage properties. The present work proposes a method to quantitatively predict the volume percentage of each of phases in Portland cement pastes. The saturated density of C-S-H is revised as a function of degree of hydration and water to cement ratio (w/c). The computed results are consistent with experimental values for cement paste that performed in this study.

Modeling Pozzolanic Systems for Subsurface Cementitious Systems

2013 ◽  
Author(s):  
Eduardus Koenders ◽  
Camila Aparecida Abelha Rocha ◽  
Romildo Dias Toledo Filho ◽  
Neven Ukrainczyk
Keyword(s):  
Particle Size ◽  
Experimental Testing ◽  
Pozzolanic Reaction ◽  
Cement Ratio ◽  
Degree Of Hydration ◽  
Hydration Model ◽  
Pozzolanic Materials ◽  
Cementitious Systems ◽  
Testing Plan ◽  
Good Agreement

The secondary pozzolanic reaction mechanism has been modeled explicitly in the Delft hydration model Hymostruc. The model calculates the progress of the hydration process as a function of the particle size distribution, the water cement ratio, the temperature and the cement and pozzolanic chemistry. The consumption of portlandite due to the activation of the pozzolanic materials is shown in detail. The numerical results are validated by an experimental testing plan on G-cement and 8% of silica fume and a water to cementitious ratio of 0.44. The simulated development of portlandite and degree of hydration and the experimental results are in good agreement.

scholarly journals Experimental Study on Effective Chloride Diffusion Coefficient of Cement Mortar by Different Electrical Accelerated Measurements

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 240
Author(s):  
Jianlan Chen ◽  
Jiandong Wang ◽  
Rui He ◽  
Huaizhu Shu ◽  
Chuanqing Fu
Keyword(s):  
Diffusion Coefficient ◽  
Cement Mortar ◽  
Early Stage ◽  
Chloride Concentration ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Cement Ratio ◽  
Water To Cement Ratio ◽  
Good Consistency ◽  
Determination Methods

This study investigated the effective chloride diffusion coefficient of cement mortar with different water-to-cement ratio (w/c) under electrical accelerated migration measurement. The cumulative chloride concentration in anode cell solution and the cumulative chloride concentration drop in the cathode cell solution was measured by RCT measurement and the results were further used to calculate the chloride diffusion coefficient by Nordtest Build 355 method and Truc method. The influence of w/c on cement mortar’s chloride coefficient was investigated and the chloride diffusion coefficient under different determination methods were compared with other researchers’ work, a good consistency between this work’s results and literatures’ results was obtained. The results indicated that the increased w/c of cement mortar samples will have a higher chloride diffusion coefficient. The cumulative chloride concentration drop in the cathode cell solution will have deviation in early stage measurement (before 60 h) which will result in overestimation of the effective chloride diffusion coefficient.

The Use of Rheology for Sludge Characterization

1982 ◽  
Vol 14 (6-7) ◽  
pp. 475-489 ◽  
Author(s):  
H W Campbell ◽  
P J Crescuolo
Keyword(s):  
Particle Size ◽  
Sewage Sludge ◽  
Test Procedures ◽  
Particle Size Reduction ◽  
Rotational Viscometer ◽  
Polymer Addition ◽  
Rheological Measurements ◽  
Acceleration Rate ◽  
Sludge Characterization ◽  
Potential Use

Rheological measurements were conducted on a variety of anaerobically digested sewage sludges to evaluate the potential use of rheology in describing the effects of chemical conditioning on the physical characteristics of sludges. The objectives of the study were to evaluate the influence of the method of chemical conditioning on rheological measurements; to determine the response of the viscometer system to changes in the instrument variables; and to evaluate interrelationships between rheology and other physical properties. All rheological measurements were made using a coaxial rotational viscometer. Evaluation of a variety of test procedures identified that both the method of adding chemical conditioners, and the acceleration rate of the rotational viscometer, could significantly alter the shape of the rheograms. A suggested methodology was identified and selected samples were analyzed in triplicate to test the reproducibility of the procedures. Existing mathematical models do not adequately describe the variety of flow behaviour patterns observed with sewage sludge. The concepts of yield stress and apparent viscosity also have limited value due to problems of definition and calculation. A parameter termed the “instantaneous viscosity”, defined as the derivative of the flow curve, is suggested as being more suitable for describing sludge behaviour. The relationships between chemical conditioning, particle size distribution and applied shear were explored. As polymer addition increased, the sludge particles became more susceptible to shear breakup. The extent of particle size reduction was a function of the rate of shear and the time during which the shear was maintained.

scholarly journals Cementitious Composites Reinforced with Polypropylene, Nylon and Polyacrylonitile Fibres

2012 ◽  
Vol 730-732 ◽  
pp. 271-276
Author(s):  
H.R. Pakravan ◽  
M. Jamshidi ◽  
M. Latifi ◽  
F. Pacheco-Torgal
Keyword(s):  
Absorption Capacity ◽  
Cement Matrix ◽  
Cementitious Composites ◽  
Scanning Electron Micrographs ◽  
Energy Absorption Capacity ◽  
Cement Ratio ◽  
Pull Out ◽  
Water To Cement Ratio ◽  
Before And After ◽  
Scanning Electron

This paper compares the adhesion strength between three polymeric fibres (polypropylene (PP), nylon66 (N66) and polyacrylonitrile (PAN)) embedded in a cement paste. The specimens were prepared at a water to cement ratio (w/c) of 0.5 and tested after 7, 14 and 28 curing days. It was found that although the adhesion between the polymeric fibres to the cement matrix is an important factor, the energy absorption capacity or energy dissipation ability of the fibres, plays a more important role in the improvement of the cementitious composites fracture toughness. Scanning electron micrographs were used to characterize the fibres surface before and after the Pull-out tests.

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