Molecular insight into the fluidity of cement pastes: Nano-boundary lubrication of cementitious materials

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.

Download Full-text

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

Construction and Building Materials ◽

10.1016/j.conbuildmat.2018.10.235 ◽

2019 ◽

Vol 198 ◽

pp. 445-455 ◽

Cited By ~ 11

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

Download Full-text

Synergistic Antiwear Effects of Zinc Dialkyl Dithiophosphate and Different Detergents

STLE/ASME 2008 International Joint Tribology Conference ◽

10.1115/ijtc2008-71013 ◽

2008 ◽

Author(s):

G. Pennecot ◽

K. Komvopoulos ◽

E. S. Yamaguchi

Keyword(s):

Wear Rate ◽

Boundary Lubrication ◽

Base Oil ◽

Temperature Range ◽

Zinc Dialkyl Dithiophosphate ◽

Contact Voltage ◽

Lubrication Regime ◽

Steel Surfaces ◽

Dialkyl Dithiophosphate ◽

Insight Into

The effectiveness of blends consisting of base oil, some secondary zinc dialkyl dithiophosphate (ZDDP), and different detergents to form antiwear tribofilms on steel surfaces sliding in the boundary lubrication regime was investigated in the temperature range of 105–125°C. The efficacy of the tribofilms formed from these blends was evaluated in terms of contact voltage and wear rate measurements. The best antiwear performance was demonstrated by the tribofilm formed from the blend containing sulphonate detergent. The results of this study provide insight into competing effects between ZDDP and different detergents that affect significantly the antiwear performance of the formed tribofilms.

Download Full-text

Mechanically activated mine tailings for use as supplementary cementitious materials

RILEM Technical Letters ◽

10.21809/rilemtechlett.2021.143 ◽

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.

Download Full-text

Effects of Nanosilica as Suspensions on the Hydration and the Microstructure of Hardened Cement Paste

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120967952 ◽

2020 ◽

pp. 036119812096795

Author(s):

Dulani P. A. Kodippili ◽

Robin A. L. Drew ◽

Michelle R. Nokken

Keyword(s):

Pore Size ◽

Isothermal Calorimetry ◽

Hardened Cement ◽

Cement Pastes ◽

Production Methods ◽

Beneficial Effects ◽

Agglomeration Of Nanoparticles ◽

Calorimetric Studies ◽

Hydration Characteristics ◽

Insight Into

Nanosilica (NS) has shown significant beneficial effects on concrete. However, the utilization of NS to achieve its maximum benefits is limited by the agglomeration of nanoparticles, which is associated with production methods and the method of NS dispersion in concrete. In this study, the effects of the utilization of NS as a suspension in calcium hydroxide (CH) on the hydration characteristics and the microstructure of the cement pastes were investigated with different levels of cement replacements (1%, 2%, 4%, and 6% NS) at 2, 7, and 28 days. The hydration of the cement pastes was investigated by isothermal calorimetry, and the measurement of CH content by thermogravimetry. The microstructures were analyzed by scanning electron microscopy and by energy dispersive X-ray spectroscopic mapping. The microstructure of the pastes was characterized by analyzing the pore size and the pore size distribution using mercury intrusion porosimetry (MIP). The calorimetric studies indicated that the replacing cement by NS derived by this method leads to faster hydration up to 4% replacement. The CH contents could be reduced by the incorporation of NS. The pore structures revealed that the pastes with NS had become comparably denser than the pastes without NS. A positive insight into the durability characteristics was shown by the results of the MIP when using NS as suspensions.

Download Full-text

Characterization of Titanium Nanotube Reinforced Cementitious Composites: Mechanical Properties, Microstructure, and Hydration

Materials ◽

10.3390/ma12101617 ◽

2019 ◽

Vol 12 (10) ◽

pp. 1617 ◽

Cited By ~ 3

Author(s):

Hyeonseok Jee ◽

Jaeyeon Park ◽

Erfan Zalnezhad ◽

Keunhong Jeong ◽

Seung Min Woo ◽

...

Keyword(s):

Mechanical Properties ◽

Cement Paste ◽

Cementitious Materials ◽

Cement Clinker ◽

Early Age ◽

Potential Candidate ◽

Hydration Kinetics ◽

Cement Pastes ◽

Viable Solution ◽

First Time

In recent years, nano-reinforcing technologies for cementitious materials have attracted considerable interest as a viable solution for compensating the poor cracking resistance of these materials. In this study, for the first time, titanium nanotubes (TNTs) were incorporated in cement pastes and their effect on the mechanical properties, microstructure, and early-age hydration kinetics was investigated. Experimental results showed that both compressive (~12%) and flexural strength (~23%) were enhanced with the addition of 0.5 wt.% of TNTs relative to plain cement paste at 28 days of curing. Moreover, it was found that, while TNTs accelerated the hydration kinetics of the pure cement clinker phase (C3S) in the early age of the reaction (within 24 h), there was no significant effect from adding TNTs on the hydration of ordinary Portland cement. TNTs appeared to compress the microstructure by filling the cement paste pore of sizes ranging from 10 to 100 nm. Furthermore, it could be clearly observed that the TNTs bridged the microcracks of cement paste. These results suggested that TNTs could be a great potential candidate since nano-reinforcing agents complement the shortcomings of cementitious materials.

Download Full-text

Additive Manufacturing of Cementitious Materials by Selective Paste Intrusion: Numerical Modeling of the Flow Using a 2D Axisymmetric Phase Field Method

Materials ◽

10.3390/ma13215024 ◽

2020 ◽

Vol 13 (21) ◽

pp. 5024

Author(s):

Alexandre Pierre ◽

Daniel Weger ◽

Arnaud Perrot ◽

Dirk Lowke

Keyword(s):

Numerical Modeling ◽

3D Printing ◽

Cement Paste ◽

Phase Field ◽

Numerical Approach ◽

Cementitious Materials ◽

Field Method ◽

Phase Field Method ◽

Shape Accuracy ◽

Cement Pastes

The 3D printing of concrete has now entered a new era and a transformation of the construction sector is expected to reshape fabrication with concrete. This work focuses on the selective paste intrusion method, which consists of bonding dry particles of aggregate with a cement paste. This innovative technique could lead to the production of very precise component for specific applications. The main obstacle to tackle in order to reach a high shape accuracy of high mechanical performances of 3D printing elements by selectively activating the material is the control of the distribution of the cement paste through the particle bed. With the aim to better understand the path followed by the solution as it penetrates a cut-section of the granular packing, two-dimensional numerical modeling is carried out using Comsol software. A phase-field method combined with a continuous visco-plastic model has been used to study the influence of the average grain diameter, the contact angle, and the rheological properties of cement pastes on the penetration depth. We compare the numerical modeling results to existing experimental results from 3D experiments and a one-dimensional analytical model. We then highlight that the proposed numerical approach is reliable to predict the final penetration of the cement pastes.

Download Full-text

Regulating the Expansion Characteristics of Cementitious Materials Using Blended MgO-Type Expansive Agent

Materials ◽

10.3390/ma12060976 ◽

2019 ◽

Vol 12 (6) ◽

pp. 976 ◽

Cited By ~ 2

Author(s):

Peng Liu ◽

Zhiyang Chen ◽

Min Deng

Keyword(s):

Stress Test ◽

Cementitious Materials ◽

Test Apparatus ◽

Early Type ◽

Late Type ◽

Cement Pastes ◽

Practical Applications ◽

Expansive Agent

To promote the application of MgO-type expansive agents (MEAs), the expansion stresses produced by compacted MEAs with different activities cured in water at 40 °C were measured using a self-designed expansion stress test apparatus. Based on these, different MEAs were divided into the early-type MgO expansive agent and the late-type MgO expansive agent classifications according to the stress curves of compacted MEAs. The two types of MEAs were blended with each other at different ratios and added into cement pastes. Results indicated that the expansion of the cement pastes added with blended MEAs lasted from the beginning to 200 days later, and the expansion characteristics can be regulated by adjusting the blending ratio of MEAs and the choice of types of MEAs. The results suggest that the expansion of MEAs can be improved by using blended MEAs in practical applications.

Download Full-text

The use of calcium sulfo-aluminate cement as an alternative to Portland Cement for the recycling of municipal solid waste incineration bottom ash in mortar

Waste Management & Research ◽

10.1177/0734242x20925170 ◽

2020 ◽

Vol 38 (8) ◽

pp. 868-875

Author(s):

Marc Antoun ◽

Frédéric Becquart ◽

Najib Gerges ◽

Georges Aouad

Keyword(s):

Compressive Strength ◽

Portland Cement ◽

Municipal Solid Waste ◽

Solid Waste ◽

Bottom Ash ◽

Waste Incineration ◽

Cementitious Materials ◽

Hydrogen Gas ◽

Municipal Solid Waste Incineration ◽

Cement Pastes

Municipal solid waste incineration generates large quantities of bottom ash that should be recycled. Current use of municipal solid waste incineration bottom ash (MSWI-BA) in cementitious materials is mostly in Ordinary Portland Cement (OPC). This paper considers using MSWI-BA as sand substitution in Calcium Sulfoaluminate Cement (CSA) as an alternative to OPC. A comparison between OPC and CSA mortars containing 0–2 mm MSWI-BA is conducted. The MSWI-BA used was treated to remove the ferrous and non-ferrous metals in order to obtain a better mineral fraction. Different percentages (0%, 25%, 50%, 75%, and 100%) of standard sand were substituted by MSWI-BA based on equivalent volume. Experimental results showed that the compressive strength and porosity of the CSA mortars were superior to OPC after substitution at 1, 7, 28, and 90 days. The compressive strength of OPC mortars with 25% substitution decreased by 40% compared to 11% for CSA mortars at 90 days. This is due to the difference in pH between the two cement pastes as OPC in contact with the MSWI-BA leads to a reaction with the aluminum content which releases hydrogen gas, increases the porosity, and decreases the compressive strength.

Download Full-text

Acid Rain Attack on Portland Cementitious Materials in China: Deterioration Process and Corrosion Products

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.168-170.82 ◽

2010 ◽

Vol 168-170 ◽

pp. 82-85

Author(s):

Kai Wang ◽

Meng Cheng Chen ◽

Li Xie

Keyword(s):

Acid Rain ◽

Ordinary Portland Cement ◽

Cementitious Materials ◽

Corrosion Layer ◽

Simulated Acid Rain ◽

Corrosion Products ◽

Corrosion Mechanism ◽

Cement Pastes ◽

Alumina Gel ◽

Deterioration Process

A research program was undertaken to discover the corrosion mechanism of portland cementitious materials to acid rain attack in China. The deterioration process and corrosion products of hardened ordinary portland cement pastes in pH 2 simulated acid rain solution were analyzed by XRD and BSE. The results indicate that the destruction of hardened portland cementitious materials by acid rain attack in China is predominantly due to the coordinated effect of H+ and SO42- of acid rain solution, and gradually occurs from the surface to the interior of materials. The corrosion products are mainly a white mushy mixture consisting of silica gel (SiO2•nH2O), alumina gel (Al2O3•nH2O) and dihydrate gypsum (CaSO4•2H2O) crystal. During the process of acid rain attack, the deteriorated specimen can be divided into corrosion layer, affected layer and unaffected layer.

Download Full-text