scholarly journals Study of Transfer Properties on Fresh Cement Pastes; Laboratory Experiments: Discontinue Measurements using a Permeameter

2016 ◽  
Vol 5 (2) ◽  
pp. 29
Author(s):  
Jean Claude Tchamba ◽  
Théodore Gautier L. J. Bikoko
Keyword(s):  
Laboratory Experiments ◽  
Cementitious Materials ◽  
Soil Permeability ◽  
Cement Pastes ◽  
Water To Cement Ratio ◽  
Fresh State ◽  
Analysis Of Results ◽  
Constant Head ◽  
Transfer Properties ◽  
Over Time

<p class="1Body">The study of hydraulic conductivity or permeability (k) of fresh cement pastes is a fundamental stage to understand the concrete<strong> </strong>placement in their formworks, and for the more extended study of the rheology of cementitious materials at fresh state. The results here are obtained on fresh cement pastes (PC) PC30, PC36 and PC40 with water- to- cement ratio (w/c) of 0.30, 0.36 and 0.40 respectively with a classical permeameter traditionally used in geotechnical for soil permeability measurements: the constant head permeameter. It has the advantage of allowing accurate measurements and staggered over time. The analysis of results obtained are in agreement with those obtained elsewhere in the literature.</p>

scholarly journals Study of Transfer Properties on Fresh Cement Pastes; Laboratory Experiments: Discontinue Measurements using a Permeameter

2016 ◽  
Vol 5 (2) ◽  
pp. 23 ◽  
Author(s):  
Jean Claude Tchamba ◽  
Théodore Gautier L. J. Bikoko
Keyword(s):  
Laboratory Experiments ◽  
Cementitious Materials ◽  
Soil Permeability ◽  
Cement Pastes ◽  
Water To Cement Ratio ◽  
Fresh State ◽  
Analysis Of Results ◽  
Constant Head ◽  
Transfer Properties ◽  
Over Time

<p class="1Body">The study of hydraulic conductivity or permeability (k) of fresh cement pastes is a fundamental stage to understand the concrete<strong> </strong>placement in their formworks, and for the more extended study of the rheology of cementitious materials at fresh state. The results here are obtained on fresh cement pastes (PC) PC30, PC36 and PC40 with water- to- cement ratio (w/c) of 0.30, 0.36 and 0.40 respectively with a classical permeameter traditionally used in geotechnical for soil permeability measurements: the constant head permeameter. It has the advantage of allowing accurate measurements and staggered over time. The analysis of results obtained are in agreement with those obtained elsewhere in the literature.</p>

scholarly journals New Approach for the Determination of Radiological Parameters on Hardened Cement Pastes with Coal Fly Ash

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 475
Author(s):  
Ana María Moreno de los Reyes ◽  
José Antonio Suárez-Navarro ◽  
Maria del Mar Alonso ◽  
Catalina Gascó ◽  
Isabel Sobrados ◽  
...  
Keyword(s):  
Fly Ash ◽  
Activity Concentration ◽  
Gamma Ray ◽  
Coal Fly Ash ◽  
Cementitious Materials ◽  
New Method ◽  
Supplementary Cementitious Materials ◽  
Hardened Cement ◽  
Cement Pastes ◽  
Activity Concentrations

Supplementary cementitious materials (SCMs) in industrial waste and by-products are routinely used to mitigate the adverse environmental effects of, and lower the energy consumption associated with, ordinary Portland cement (OPC) manufacture. Many such SCMs, such as type F coal fly ash (FA), are naturally occurring radioactive materials (NORMs). 226Ra, 232Th and 40K radionuclide activity concentration, information needed to determine what is known as the gamma-ray activity concentration index (ACI), is normally collected from ground cement samples. The present study aims to validate a new method for calculating the ACI from measurements made on unground 5 cm cubic specimens. Mechanical, mineralogical and radiological characterisation of 28-day OPC + FA pastes (bearing up to 30 wt % FA) were characterised to determine their mechanical, mineralogical and radiological properties. The activity concentrations found for 226Ra, 212Pb, 232Th and 40K in hardened, intact 5 cm cubic specimens were also statistically equal to the theoretically calculated values and to the same materials when ground to a powder. These findings consequently validated the new method. The possibility of determining the activity concentrations needed to establish the ACI for cement-based materials on unground samples introduces a new field of radiological research on actual cement, mortar and concrete materials.

scholarly journals Investigation of C-S-H in ternary cement pastes containing nanosilica and highly-reactive supplementary cementitious materials (SCMs): Microstructure and strength

2019 ◽  
Vol 198 ◽  
pp. 445-455 ◽  
Author(s):  
Daniel da Silva Andrade ◽  
João Henrique da Silva Rêgo ◽  
Paulo Cesar Morais ◽  
Anne Neiry de Mendonça Lopes ◽  
Moisés Frías Rojas
Keyword(s):  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Cement Pastes

Test Methods for Rheological Properties of Self-Compacting Concrete Pastes

2011 ◽  
Vol 338 ◽  
pp. 396-400
Author(s):  
Bao Guo Ma ◽  
Hui Xian Wang ◽  
Jian Huang ◽  
Liu Qing Song
Keyword(s):  
Rheological Properties ◽  
Cement Paste ◽  
Test Methods ◽  
General Study ◽  
Self Compacting Concrete ◽  
Cement Pastes ◽  
Different Types ◽  
Over Time

This paper provides a general study on cement paste flow which derived from self- compacting concretes. Rheometer, Marsh cone and mini-slump cone were used to evaluate fluidity of cement pastes containing superplasticizers of different types and dosages and loss of fluidity over time. There is a superplasticizer saturation dosage beyond which no significant fluidity increase can be found. This paper evaluated the effect of these three methods using rheometer as control and the optimum superplasticizer type for the preparation of self-compacting concrete was suggested.

scholarly journals Mechanically activated mine tailings for use as supplementary cementitious materials

2021 ◽  
Vol 6 ◽  
pp. 61-69
Author(s):  
Sivakumar Ramanathan ◽  
Priyadarshini Perumal ◽  
Mirja Illikainen ◽  
Prannoy Suraneni
Keyword(s):  
Mine Tailings ◽  
Isothermal Calorimetry ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Strong Correlations ◽  
Negative Effects ◽  
Cement Pastes ◽  
Amorphous Content ◽  
Milling Duration ◽  
Median Particle

Two mine tailings are evaluated for their potential as supplementary cementitious materials. The mine tailings were milled using two different methods – ball milling for 30 minutes and disc milling for durations ranging from 1 to 15 minutes. The modified R3 test was carried out on the mine tailings to quantify their reactivity. The reactivity of the disc milled tailings is greater than those of the ball milled tailings. Strong correlations are obtained between milling duration, median particle size, amorphous content, dissolved aluminum and silicon, and reactivity of the mine tailings. The milling energy results in an increase in the fineness and the amorphous content, which do not appreciably increase beyond a disc milling duration of 8 minutes. The reactivity increases significantly beyond a certain threshold fineness and amorphous content. Cementitious pastes were prepared at 30% supplementary cementitious materials replacement level at a water-to-cementitious materials ratio of 0.40. No negative effects of the mine tailings were observed at early ages in cement pastes based on isothermal calorimetry and thermogravimetric analysis, demonstrating the potential for these materials to be used as supplementary cementitious materials.

Effect of w/cm and Composition on Correlations of Concrete Electrical Resistivity and Chloride Migration Coefficients

2016 ◽  
Vol 711 ◽  
pp. 21-28
Author(s):  
Francisco J. Presuel-Moreno
Keyword(s):  
Electrical Resistivity ◽  
Steady State ◽  
Fly Ash ◽  
Laboratory Experiments ◽  
Chloride Ion ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Ion Migration ◽  
Resistivity Measurements ◽  
Chloride Migration

The performance with regard to chloride penetration of specimens made with three base compositions (supplementary cementitious materials: 20% fly ash, 20% fly ash + 8% silica fume, and 50% slag replacement by weight of cement), and water-to-cementitious ratios of 0.35, 0.41, or 0.47 were investigated here. In this investigation, laboratory experiments were carried out to study the correlation between electrical resistivity and non-steady state chloride ion migration coefficients (Dnssm) of concrete. NT Build 492 was used to determine chloride migration coefficients. Rapid migration tests and resistivity measurements were performed several times over two years, and the non-steady state migration coefficient (Dnssm) vs. resistivity values were correlated. Experimental results show that a good correlation was found between electrical resistivity and Dnssm. Based on the relationships developed from this investigation, it appears that the correlations are age and composition dependent.

Chloride Ingress Control and Promotion of Internal Curing in Concrete Using Superabsorbent Polymer

2021 ◽  
Vol 888 ◽  
pp. 67-75
Author(s):  
Ariel Verzosa Melendres ◽  
Napoleon Solo Dela Cruz ◽  
Araceli Magsino Monsada ◽  
Rolan Pepito Vera Cruz
Keyword(s):  
Compressive Strength ◽  
Cementitious Materials ◽  
Internal Curing ◽  
Mix Design ◽  
Chloride Ingress ◽  
Superabsorbent Polymer ◽  
Cement Slurry ◽  
Chloride Permeability ◽  
Cement Ratio ◽  
Water To Cement Ratio

Chloride ingress into concrete from the surrounding environment can result in the corrosion of the embedded steel reinforcement and cause damage to the concrete. Superabsorbent polymer (SAP) with fine particle size was incorporated into the structure of concrete for controlling the chloride ingress and improving its compressive strength via promotion of internal curing. The SAP used in this study was evaluated for its absorbency property when exposed to cementitious environment such as aqueous solution of Ca (OH)2 and cement slurry. The results were compared to that in sodium chloride solution, the environment where absorbency of most of the SAP found in the market are well studied. Results showed that although SAP absorbency decreased with increasing concentration of Ca (OH)2 and cement, the results suggest that water containing cementitious materials are able to be absorbed by SAP. Chloride ingress into 28-day cured concrete specimens were determined using Rapid Chloride Penetration Test (RCPT) method employing 60V DC driving force. Concrete samples with size of 50 mm height x 100 mm diameter were prepared using a M25 mix design with 0.4 and 0.45 water to cement ratios and different percentages of SAP such as 0.05%, 0.1% and 0.15% with respect to cement mass. Results showed that concrete with 0.15% SAP gave the best result with 14% less chloride permeability than concrete with no SAP for a 0.4 water to cement ratio. Concrete samples for compressive strength tests with size of 200 mm height x 100 mm diameter were prepared using the same mix design and percentages of SAP and cured for 28 days. Results showed that the best results for compressive strength was found at 0.1% SAP at a 0.4 water to cement ratio which can be attributed to internal curing provided by SAP.

scholarly journals Effects of Bacillus subtilis biocementation on the mechanical properties of mortars

2019 ◽  
Vol 12 (1) ◽  
pp. 31-38 ◽  
Author(s):  
N. SCHWANTES-CEZARIO ◽  
M. F. PORTO ◽  
G. F. B. SANDOVAL ◽  
G. F. N. NOGUEIRA ◽  
A. F. COUTO ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Calcium Carbonate ◽  
Cementitious Materials ◽  
Mechanical Analysis ◽  
Sem Analysis ◽  
Subtilis Strain ◽  
Cement Mortars ◽  
Water To Cement Ratio ◽  
Mixing Water

Abstract This study aims to evaluate the influence of B. subtilis AP91 spores addition on the mechanical properties of mortars. B. subtilis strain AP91, isolated from rice leaves of the needle variety, which has an early cycle of production, was used at the concentration of 105 spores/mL in mortars with cement-to-sand ratio of 1:3 (by weight) and water-to-cement ratio (w/c) of 0.63. These spores were added in two different ways: in the mixing water and by immersion in a solution containing bacterial spores. Scanning Electron Microscope (SEM) analysis showed crystals with calcium peaks on the EDS, which possibly indicates the presence of bioprecipitated calcium carbonate. The results obtained in the mechanical analysis showed that the bioprecipitation of CaCO3 by B. subtilis strain AP91 was satisfactory, particularly when the spores were added in the mixing water, increasing the compressive strength up to 31%. Thus, it was concluded that the addition of B. subtilis AP91 spores in the mixing water of cement mortars induced biocementation, which increased the compressive strength. This bioprecipitation of calcium carbonate may very well have other advantageous consequences, such as the closure of pores and cracks in cementitious materials that could improve durability properties, although more research is still needed on this matter.

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