Mathematical modeling of cement paste microstructure by mosaic pattern. Part II. Application

1997 ◽  
Vol 12 (7) ◽  
pp. 1741-1746 ◽  
Author(s):  
Paul D. Tennis ◽  
Yunping Xi ◽  
Hamlin M. Jennings
Keyword(s):  
Mathematical Modeling ◽  
Spatial Distribution ◽  
Portland Cement ◽  
Cement Paste ◽  
Pattern Analysis ◽  
Mosaic Pattern ◽  
Cement Pastes ◽  
Multiphase Materials ◽  
Spatial Features ◽  
Complex Shapes

A model based on mosaic pattern analysis is shown to have the potential to describe the complex shapes and spatial distribution of phases in the microstructures of multiphase materials. Several characteristics of both micrographs of portland cement pastes and images generated using the few parameters of the model are determined and, for the most part, agreement is good. The advantage is that spatial features of the microstructures can be captured by a few parameters.

Interaction Between Naphthalene Sulfonate and Silica Fume in Portland Cement Pastes

1987 ◽  
Vol 114 ◽  
Author(s):  
Sidney Diamond ◽  
Leslie J. Struble
Keyword(s):  
Portland Cement ◽  
Silica Fume ◽  
Cement Paste ◽  
Uv Spectrophotometry ◽  
Residual Concentration ◽  
Cement Pastes ◽  
High Ph ◽  
Substantial Concentration ◽  
Low Dosage

ABSTRACTPortland cement pastes were mixed with predissolved naphthalene sulfonate superplasticizer at normal water:cement ratios. Solutions were separated from the fresh pastes at intervals and the residual concentration of the superplasticizer determined by UV spectrophotometry. At low dosage levels essentially all of the superplasticizer was found to be removed from solution within a few minutes; at high dosage levels a substantial concentration was maintained in solution at least to approximately the time of set. In pastes in which silica fume replaced 10% by weight of the cement, it was found that the incorporation of silica fume significantly increased the uptake of superplasticizer. In separate trials it was found that the silica fume by itself adsorbed little superplasticizer, even from high pH solution simulating that of cement paste.

Estimation and Measurement of Porosity Change in Cement Paste

2010 ◽  
Author(s):  
Eunyong Lee ◽  
Haeryong Jung ◽  
Ki-jung Kwon ◽  
Do-Gyeum Kim
Keyword(s):  
Ionic Strength ◽  
Portland Cement ◽  
Cement Paste ◽  
Thermodynamic Model ◽  
Ordinary Portland Cement ◽  
Type I ◽  
Hydration Products ◽  
Cement Pastes ◽  
Porosity Change ◽  
Dissolution Reaction

Laboratory-scale experiments were performed to understand the porosity change of cement pastes. The cement pastes were prepared using commercially available Type-I ordinary Portland cement (OPC). As the cement pastes were exposed in water, the porosity of the cement pastes sharply increased; however, the slow decrease of porosity was observed as the dissolution period was extended more than 50 days. As expected, the dissolution reaction was significantly influenced by w/c raito and the ionic strength of solution. A thermodynamic model was applied to simulate the porosity change of the cement pastes. It was highly influenced by the depth of the cement pastes. There was porosity increase on the surface of the cement pastes due to dissolution of hydration products, such as portlandite, ettringite, and CSH. However, the decrease of porosity was estimated inside the cement pastes due to the precipitation of cement minerals.

Rectifying and thermocouple junctions based on Portland cement

2001 ◽  
Vol 16 (7) ◽  
pp. 1989-1993 ◽  
Author(s):  
Sihai Wen ◽  
D. D. L. Chung
Keyword(s):  
Carbon Fiber ◽  
Portland Cement ◽  
Cement Paste ◽  
Steel Fiber ◽  
Cement Pastes

Rectifying and thermocouple junctions have been achieved using electrically dissimilar Portland cement pastes. The preferred junction is a pn-junction involving steel fiber cement paste (n-type) and carbon fiber cement paste (p-type). For this junction, the thermocouple sensitivity is 70 εV/°C.

scholarly journals Effect of Particle Size of Periclase on the Periclase Hydration and Expansion of Low-Heat Portland Cement Pastes

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Man Yan ◽  
Min Deng ◽  
Chen Wang ◽  
Zhiyang Chen
Keyword(s):  
Particle Size ◽  
Portland Cement ◽  
Cement Paste ◽  
Raw Materials ◽  
Internal Standard ◽  
Internal Standard Method ◽  
Hydration Degree ◽  
Cement Pastes ◽  
Effect Of Particle Size ◽  
Curing Age

In this paper, low-heat Portland cement (LHC) clinkers were prepared by calcining raw materials at 1350°C for 2.0 hours, 1400°C for 1.0 hour, 1400°C for 1.5 hours, 1400°C for 2.0 hours, 1450°C for 1.0 hour, and 1450°C for 2.0 hours. The clinkers were ground with gypsum to produce LHC. The particle size of periclase was analysed by BSEM. Expansion of LHC pastes due to hydration of periclase was measured. The hydration degree of periclase in LHC pastes was quantitatively determined by XRD internal standard method and BSEM. The results showed that the particle size of periclase was larger when clinkers were calcined at higher temperatures or for longer time. Smaller periclase (2.60 μm) in LHC pastes tended to hydrate faster. As a result, expansion of LHC pastes develops relatively faster. Smaller particle of periclase in clinker tends to result in higher hydration degree of periclase in pastes cured at 20°C for 240 days, and there is a small amount of brucite appearing around periclase. The hydration rate of 4.00 μm periclase particle in cement paste cured at 80°C is obviously faster than that in paste cured at 20°C and 40°C. When cement paste was cured at 80°C for 7 days, the periclase was hydrated for 32.56%. The smaller size periclase (1–3 μm) had fully hydrated when the curing age was 240 days, and a large amount of brucite was produced around the larger periclase particle.

INFLUENCE OF CEMENT TYPE AND ADMIXTURES ON RHEOLOGICAL PROPERTIES OF CEMENT PASTE / CHEMINIŲ ĮMAIŠŲ POVEIKIS REOLOGINĖMS CEMENTO TEŠLOS SAVYBĖMS

2014 ◽  
Vol 5 (4) ◽  
pp. 175-181 ◽  
Author(s):  
Mindaugas Macijauskas ◽  
Albinas Gailius
Keyword(s):  
Portland Cement ◽  
Induction Period ◽  
Rheological Properties ◽  
Cement Paste ◽  
Flow Characteristics ◽  
Cement Pastes ◽  
Chemical Admixtures ◽  
Materials Used ◽  
Rotation Viscometer ◽  
Portland Cement Paste

The article aims to research the influence of the chemical admixtures on the rheological properties of Portland cement paste and determine their impact on the effectiveness of hydration induction period. Materials used in the study: Portland cement CEM I 42.5 (N and R early strength), limestone Portland cement CEM II/A-LL 42.5 N, plasticizer Centrament N3, the latest generation superplasticizer MC-PowerFlow 3140 and water. Investigations focused on effects of Plasticizer and superplasticizer on water and cement (W/C) ratio and Portland cement paste flow characteristics. Portland cement pastes with the same watercement ratio with and without chemical admixtures were tested. Investigations were carried out using a Suttard viscometer and rotation viscometer Rheotest NH 4.1 with coaxial cylinders. It was observed that viscosity of Portland cement paste can be controlled by chemical admixtures during the hydration induction period. Investigations of effectiveness of the chemical admixtures on the rheological properties of the Portland cement pastes, comparing it with a control composition of the Portland cement paste were provided in the article. Diagrams show changes of the viscosity of the Portland cement pastes depending on the type and amount of the used chemical admixtures. Obtained results were compared with the same consistence without admixtures. After making the regressive analysis of research results of Portland cement paste with and without chemical admixtures, empirical equations were produced. Santrauka Šio darbo tikslas – ištirti cheminių įmaišų poveikį reologinėms portlandcemenčio tešlų savybėms ir nustatyti jų poveikio veiksmingumą indukcinio hidratacijos periodo metu. Tyrimams naudotos šios medžiagos: AB „Akmenės cementas“ gamyklos portlandcementis CEM I 42,5 (N ir R ankstyvojo stiprumo), klinties portlandcementis CEM II/A-LL 42,5 N, plastiklis Centrament N3, naujausios kartos superplastiklis MC-PowerFlow 3140 ir vanduo. Ištirtas plastiklio ir superplastiklio poveikis vandens ir cemento (V/C) santykio pokyčiams ir portlandcemenčio tešlų sklidumui naudojant Sutardo viskozimetrą. Buvo tiriamos vienodo vandens ir cemento santykio portlandcemenčio tešlos su cheminėmis įmaišomis ir be jų. Tyrimai atlikti naudojant rotacinį viskozimetrą Rheotest NH 4.1 su bendraašiais cilindrais. Nustatytas cheminių įmaišų portlandcemenčio tešlose veiksmingumas. Pastebėta, kad portlandcemenčio tešlų dinaminė klampa gali būti reguliuojama cheminėmis įmaišomis viso indukcinio hidratacijos periodo metu. Atlikus portlandcemenčio tešlų su cheminėmis įmaišomis ir be jų tyrimų rezultatų regresinę analizę, gautos empirinės lygtys.

Erosion Phases in Two Types of Cement Pastes Containing Limestone Exposed to Sulfate Attack

2014 ◽  
Vol 584-586 ◽  
pp. 1182-1187 ◽  
Author(s):  
Feng Chen Zhang ◽  
Yun Zhao ◽  
Fu Wan Zhu
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Limestone Powder ◽  
Test Results ◽  
X Ray Diffraction ◽  
Limestone Filler ◽  
Cement Pastes ◽  
Cement Production ◽  
X Ray ◽  
Gypsum Formation

Limestone filler and aggregates are used widely in cement production and concrete mixing nowadays, which could be connected with thaumasite formation, and lead to a lack of durability further. This work deals with the sulfate minerals including of thaumasite, ettringite and gypsum in two types of cement pastes containing 35% w/w limestone powder immersed in MgSO4 solution at 5°C±2°C for 15 weeks by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD). Two types of cements were used: (i) ordinary Portland cement (P·O), (ii) typeII Portland cement (P·II). Test results show that thaumasite is present in two types of cement pastes, amount of thaumasite as well as amount of portlandite reacted with external SO42- in P·II cement paste are more than those in P·O cement paste. It indicates that P·II cement is more susceptible to thaumasite formation than P·O cement containing the same amount of limestone powder, and more gypsum formation could contribute to thaumasite formation possibly during the external MgSO4 attack at low temperature.

The Influence of Superplasticizers Based on Modified Acrylic Polymer and Polycarboxylate Ester on the Plasticizing Effect of Cement Paste

2017 ◽  
Vol 904 ◽  
pp. 167-173
Author(s):  
Mindaugas Macijauskas ◽  
Gintautas Skripkiūnas
Keyword(s):  
Portland Cement ◽  
Rheological Properties ◽  
Cement Paste ◽  
Acrylic Polymer ◽  
Cement Pastes ◽  
Rotational Rheometer ◽  
Coaxial Cylinders ◽  
Materials Used ◽  
The Impact ◽  
Different Levels

The article aims to present a research into the impact of the dosage and effectiveness of superplasticizers based on modified acrylic polymer and polycarboxylate ester (from 0 to 1.2 %) on rheological properties of the cement pastes (yield stresses and plastic viscosities), of different testing times after mixing (from 0 to 90 min). Materials used in the study: Portland cement CEM I 42.5 R, superplasticizers SP1 (modified acrylic polymer based), SP2 (polycarboxylate ester based), and water. Investigation was carried out using rotational rheometer Rheotest RN4.1 with coaxial cylinders. The tests revealed that superplasticizer SP2 is more effective than SP1 – cement paste (W/C = 0.30) exhibits better flowability and improved rheological qualities. Superplasticizers SP1 and SP2 exhibit different levels of plasticizing effectiveness and ability to retain the effect’s duration. Due to the increase in the dosage of superplasticizers SP1 and SP2 from 0 to 1.2 %, plasticizing effect increases. It is also observed that larger dosage of SP1 (0.6-1.2 %) results in slower increase in plasticizing effects until the 90 min margin. In conclusion, from the start of mixing until the 90 min margin, the best plasticizing effect and its retention achieved by superplasticizer SP2. Recommended SP2 dosage – from 0.6 to 0.8 %.

scholarly journals Towards the Understanding of the pH Dependency of the Chloride Binding of Portland Cement Pastes

2018 ◽  
Vol 58 (1) ◽  
pp. 143-162 ◽  
Author(s):  
Alisa Machner ◽  
Petter Hemstad ◽  
Klaartje De Weerdt
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Considerable Increase ◽  
Phase Assemblage ◽  
Chloride Binding ◽  
Nacl Solution ◽  
Cement Pastes ◽  
Ph Dependency ◽  
Decreasing Ph ◽  
Portland Cement Paste

Abstract Hydrated Portland cement paste exposed to a NaCl solution was acidified by adding HCl in small steps, gradually lowering the pH. The chloride binding of the cement paste changed as a function of the pH. For the range of pH from 13.2 to 12.2, decreasing pH resulted in a considerable increase in the chloride binding. At a pH of 11, the cement paste showed almost no chloride binding. In order to explain the changes in chloride binding upon lowering the pH, the phase assemblage was investigated with SEM-EDS, TGA and XRD and compared to a thermodynamic modelling.

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