Cement Setting Research Articles

Experimental Study on the Evolution Law of the Mechanical and Pore Characteristic Parameters of Set Cement under High- and Ultra-High-Temperature Treatments

Cement has been widely used as a structural material in many underground projects, and these projects often face high- or ultra-high-temperature environments, leading to the deterioration of the mechanical, porosity, and permeability properties of set cement, thereby increasing the risk of instability of underground structures. In response to this, two new temperature-resistant cement slurry systems were designed. Experiments were conducted on the changes in porosity and permeability of set cement after thermal treatment using low-field nuclear magnetic resonance technology (NMR), visual studies of pore and crack development were carried out using the argon-ion polishing field emission scanning electron microscopy (FE-SEM) and computed tomography (CT) methods. The research results show that as the thermal treatment temperature continued to rise, the compressive strength first increased (25 °C–200 °C) and then decreased (200 °C–600 °C). The porosity of the set cement first decreased (25 °C–115 °C) and then increased (115 °C–600 °C), and the penetration first slowly increased (25 °C–400 °C) and then rapidly increased (400 °C–600 °C). Visualization experiments were conducted on micro-cracks and the pore distribution of the set cement under high- and ultra-high-temperatures, which proved the evolution law of these characteristic parameters. The research results have vital reference significance for the protection of the structural stability of cement components when encountering high-temperature environments.

Novel Processing Methods of Low-Clinker Multi-Component Cementitious Materials—A Review

The wide use of multi-component cement of highly reduced Portland clinker factor is largely impeded by detrimental changes in the rheological properties of concrete mixes, a substantial reduction in the early rate of cement hardening, and sometimes the insufficient strength of mature concrete. Therefore, major changes are needed in traditional concrete-production technologies if low-clinker cement is to gain wider acceptance. This review’s goal is to summarize the impacts of using non-ionizing radiation methods to improve the dispersion of concrete mix constituents, cement setting, and early hardening. The potential impacts of such interactions on the permeability and strength of concrete are also highlighted and investigated. Their intriguing potential for delivering additional energy to cementitious mixtures is analyzed for batch water, solid non-clinker constituents of cement (mainly supplementary cementitious materials), and their mixtures with aggregates. The advantages of adopting these non-traditional methods are found to be highly alluring to the greener preparation techniques used in the construction materials sector.

Ultrasonic monitoring of cement setting based on embedded sensor

The hydration property of cement directly affects the performance index of concrete, so it is necessary to monitor the hydration setting process of cement. The aim of this paper is to monitor the process of cement hydration setting by ultrasonic wave. Ultrasonic monitoring is a kind of dynamic non-destructive testing technology, which has the advantages of real-time, on-line and continuous. In this paper, an in-situ monitoring technology of cement hydration setting based on embedded piezoelectric ceramic sensor is introduced. The monitoring results show that the amplitude change of ultrasonic signal received by the sensor can indirectly reflect the change process of cement hydration solid and liquid, especially the initial setting node has a high catching ability.

Comparative Outcomes of Pulpotomy in Mature Molars with Irreversible Pulpitis: A Non-Randomized Trial Evaluating Calcified and Non-Calcified Pulp Chambers.

This non-randomized clinical trial investigated the outcomes of full pulpotomy in adult molars with irreversible pulpitis, comparing those with calcified and non-calcified pulp chambers over 6 and 12 months. A total of 101 adult permanent molars with irreversible pulpitis, in individuals over 12 years old, were categorized based on pulp chamber calcification observed in radiographic images by two endodontists. Subsequently, full pulpotomy procedures were performed, achieving hemostasis, and applying a 2 mm layer of calcium-enriched mixture (CEM) cement as a pulp covering agent. After 48 hours, the setting of the CEM cement was verified, followed by the application of a layer of resin-modified glass-ionomer. The tooth was then restored using amalgam. Clinical and radiographic evaluations were conducted at 6-month and 1-year follow-ups by blinded endodontists. Success rates were compared using Fisher's exact test and logistic regression tests with a significance level of 0.05. Among the 97 patients with 6-month and 1-year follow-ups, all achieved clinical success. Radiographic success rates were 99% at 6 months and 96.9% at 1 year, regardless of pulp calcification. In the 6-month follow-up, success rates were 98.07% for non-calcified pulp chambers and 100% for calcified pulp chambers. At the 1-year follow-up, success rates were 96.1% and 97.8%, respectively. Statistical analysis showed no significant difference in radiographic success rate between the two groups at both follow-ups (P>0.05). Full pulpotomy using CEM cement is a successful treatment for adult permanent teeth with calcified and non-calcified pulp chambers presenting signs and symptoms of irreversible pulpitis up to a 1-year follow-up. This study provides compelling evidence that vital pulp therapy can be effectively employed in the pulpotomy of calcified teeth, at least in the short term.

Брушитовый бор-содержащий цемент с антибактериальными свойствами

Boron-containing brushite cements (B-BC) for bone grafting based on B-substituted β-tricalcium phosphate (B-TCP) have been developed. The phase composition and microstructure of B-BC have been studied. It is shown that the crystalline phase of brushite is formed as a result of hardening of cements. The behavior of B-BC in physiological solution containing TRIS-buffer was studied. The strength of B-BC under compression 5 days after mixing is 22.5 ± 1 MPa. Studies of antibacterial activity against gram-negative strain E. coli ATCC25922 and gram-positive strain S. aureus ATCC25923 showed that boron containing brushite cement exhibits antibacterial activity against both strains, causing a decrease in the number of CFU after 3 h of incubation. In vitro studies of the developed B-BC were carried out, it was shown that the developed cements based on TCP and B-TCP are biocompatible and promising for use in bone tissue surgery.

Mechanical properties, durability and self-healing performance of mortar containing double-layers capsules

To improve the self-healing performance of cementitious materials and minimize the negative impact of self-healing materials on mortar, a novel type of double-layer capsules is developed in this study. The developed double-layer capsule includes the rapid hardening cement as the internal wall and polyvinyl alcohol (PVA) as the external wall. To evaluate its impact on mortar, two factors (i.e., capsule size and dosage) are considered and the correspondent experiments of investigating mechanical properties, durability, and self-healing performance are conducted. Experimental results present that the double-layer capsules reduce the flexural and compressive strength of mortar. With a reduced capsule size and a small ratio of the dosage, the negative impact the capsule gradually weakens. Moreover, the mixing of capsules slightly decreases the chloride penetration resistance and carbonation resistance of mortar specimens, while improves the frost resistance and impermeability greatly when the dosage is within 10%. Furthermore, the capsules can significantly improve the self-healing capacity of mortar. Especially when the capsule size is 2.36–3.2 mm and the dosage is 10%, the healing effect on matrix is highest. In addition, the XRD\\SEM\\XCT results indicated that the healing products mainly include C-S-H gel, CaCO3, Aft and Mg-containing compounds, the filling and bonding effects of which realize the automatic and effective recovery of matrix properties.

Anti-strength retrogression cementing materials for deep and ultra-deep wells

Recent studies have brought to light a critical issue pertaining to the conventional silica-enriched Portland cements employed in deep and ultra-deep wells. The traditional silica-enriched oil well cements were found to exhibit substantial strength retrogression during prolonged curing under high temperatures, posing a significant threat to the overall cementing quality and subsequent production safety. This study proposes a novel approach to enhance the long-term stability of traditional silica-cement systems under high temperature conditions by introducing both granulated blast furnace slag (GBFS) and fly ash to the system. Test results indicated that the addition of GBFS increased the strength stability of the traditional silica-cement system but failed to completely prevent its strength retrogression. In contrast, the combined addition of GBFS and fly ash in silica-cement system significantly enhanced its long-term strength measured after 90 d curing. The strength test results were corroborated by further evidences from permeability tests as well mercury intrusion porosimetry analyses. Detailed analysis of the set cement composition suggests that the inhibition of xonotlite phase and the promotion of tobermorite and grossular phases in hydration products are responsible for improved long-term strength stability.

Octacalcium phosphate phase forming cements as an injectable bone substitute materials: Preparation and in vitro structural study

In the realm of regenerating damaged or degenerated bones through minimally invasive techniques, injectable materials have emerged as exceptionally promising. Among these, calcium phosphate bone cements (CPCs) have garnered significant interest due to their remarkable bioactivity, setting it apart from non-degradable alternatives such as polymethyl methacrylate cements. α-Tricalcium phosphate (α-TCP) is a widely used solid phase component in CPCs. It can transform into calcium-deficient hydroxyapatite (CDHAp) when it comes in contact with water. In this study, we aimed to create an injectable, self-setting bone cement using low-temperature synthesized α-TCP powder as a single precursor of the powder phase. We found that changes in the pH of the liquid phase (pH 6.0, pH 6.2, pH 7.0 and pH 7.4) significantly altered the cement's setting, handling, and mechanical properties. The formation of the octacalcium phosphate (OCP) phase was identified in our study, which positively affects the osteoblastic cell response. Hardened OCP-forming bone cements prepared using a liquid phase with pH 7.0 and 7.4 showed better osteogenic cell attachment and proliferation than those prepared with pH 6.0 and 6.2. Our study suggests that changes in the pH of the liquid phase can significantly affect the properties of α-TCP-based bone cement, and the presence of the OCP phase is crucial for optimal cement performance.

A viscosity-soluble type biomimetic self-healing cement slurry system

With the development of cementing slurry technology, cementing self-healing has become one of the most effective technologies to prevent and treat oil and gas channeling and improve long-term sealing capacity of cement sheath. To solve the technical problem of annulus oil and gas channeling caused by the long-term sealing failure of cement sheath, this paper researches and develops a kind of viscosity-soluble type biomimetic self-healing cement slurry system from the perspective of chemical biomimetics, based on the technical idea of “prevention before blocking”. Then, the engineering performance of this biomimetic self-healing cement slurry system and the mechanical property of self-healing set cement are evaluated respectively. In addition, the mechanical recovery capacity and permeability reducing rate of the self-healing set cement conserved with methane are evaluated by creating fractures through splitting. Finally, the healing mechanisms of the self-healing cement are analyzed by means of SEM microscopic test and infrared spectrography. And the following research results are obtained. First, the set cement has excellent mechanical property. When the compressive strength decreases by 15 %, the elastic modulus of set cement decreases by 41 %, showing good toughness to play the role of “first prevention”. Second, when meeting hydrocarbon, the damaged set cement is excited to generate a kind of viscosity-soluble type gelatinous ester substance, which re-bonds the skeleton of the set cement. When the self-healing set cement is conserved with methane, its compressive strength recovery rate is up to 94.5 %, bending strength recovery rate is 58.6 %, gas log permeability drops by 99 %, and liquid log permeability drops by 100 %, so as to realize “blocking later”. In conclusion, the viscosity-soluble type biomimetic self-healing cement slurry system can effectively achieve cementing integrity and long-term sealing integrity through self-healing after the damage of cement sheath, which provides a strong technical support for preventing the production safety hazard of sustained casing pressure in oil and gas wells and is beneficial to solve the technical problem of annulus oil and gas channeling caused by long-term sealing failure of cement sheath.

Research of the Influence OF Activated Silica on the Durability of Basalt Fiber in Cement Concrete

AbstractReinforcement of cement concrete with basalt fiber reduces their shrinkage, increases crack resistance and compressive strength (by 30‐50%), and flexural tension by more than two times. Basalt fiber‐reinforced concrete loses its strength characteristics over time due to alkaline corrosion of the fiber surface. The destruction occurs as a result of the interaction of the surface of the fiber with hydrate of lime, which is released during the hardening of cement. To increase the stability of the fiber, an active siliceous component is introduced into the concrete mixture ‐ ferromanganese production waste. This gave an opportunity significantly to improve the strength characteristics of fiber‐reinforced basalt fiber of concrete during long‐term storage due to a decrease in the content in the system Calcium Hydroxid Ca(OH)2 and preservation of the fiber surface without corrosion.

Masquelet Technique: Visualization of Cement Spacer Utilizing Methylene Blue

Masquelet Technique: Visualization of Cement Spacer Utilizing Methylene Blue

MgO‐based binders

AbstractTo limit global temperature rise to below 2°C, we need to radically and rapidly change the way we build and use materials, since construction is responsible for 20‐40% of industrial CO2 emissions. Magnesium carbonate‐based cements have the potential to become a major carbon sink in construction industry, as CO2 will not be emitted during their production, but CO2 will rather be bound during hardening. Two different reaction mechanisms lead to setting and hardening of such HMC cements: i) hydration of MgO‐Mg‐carbonate, also in blends with silica and other mineral additions, in the presence of water or salt solutions (such as sodium bicarbonate solution) at ambient conditions or ii) carbonation hardening of MgO‐based systems at increased CO2 partial pressure and/or at increased temperatures.However, the utilization of hydrated magnesium carbonate and magnesium silicate cements is currently hampered by the lack of systematic experiments and of fundamental understanding of the factors affecting the hardening process, mechanical properties, long‐term behavior and durability. In particular, the role of temperature, relative humidity and addition of supplementary cementitious materials and/or industrial by‐products has not been systematically investigated. We need knowledge both on the practical side through systematic experiments with pastes, mortars and concretes as well as on a fundamental level through solubility and sorption experiments and thermodynamic modelling. In addition, reaction kinetics need to be optimized as well as the early formation of the preferred phases (stability enhancement) to develop efficient HMC cements for construction. Due to the socio‐economic relevance of cement and concrete, the impact of such “carbon”‐negative cements may go beyond a purely scientific one and lead to technological breakthroughs to the benefit of environment and society.

Fast set GGBS Binder

AbstractTo reduce CO2 emission producing Ordinary Portland cement (every ton of Portland cement accounts for roughly 850 kg CO2) the use of supplementary cementing materials (SCM's) are becoming todays standard in the cement and construction industry.Although some SCMs are used on their own, most of them are used in combination with Portland cement clinker.Aim was to accelerate the setting time of a pure GGBS binder and improve its early strength development. From different publications we learned that fast setting cements contain C11A7. CAF2 similar to the phases calculated from our Type II GGBS.

Application of the virtual-fit method for fixed complete denture cases designed on intraoral scans: Effect of cement spacing

ObjectivesTo validate the virtual-fit alignment, analyze the impact of cement spacing on internal/marginal gaps, and correlate results with conventional trueness measures. MethodsFour dental abutment models were scanned using an industrial reference scanner (one time each), Emerald S (three times each), and Medit i700 (three times each) intraoral scanners (IOS). On each IOS scan (n = 24), three complete-arch fixed frameworks were designed with 70 or 140 µm cement space with no marginal space (groups 70 and 140) and 70 µm with an additional 20 µm space, including the margin (group 70+20). Two types of alignment were performed by GOM Inspect software. The reference and IOS scans were aligned through a conventional iterative closest point algorithm (ICP) where the penetration of the two scans was permitted into each other (conventional trueness method). Second, the computer-aided designs were superimposed with the reference scan also using an ICP, but preventing the design from virtual penetration into the model (virtual-fit method). The virtual-fit algorithm was validated by non-penetration alignment of the designs with the IOS scans. Internal and marginal gap was measured between the design and the abutments. The difference between spacing groups was compared by Friedman's test. A statistical correlation (Spearman's Rho Test) was computed between the measured gaps and the conventional trueness method. A significant difference was accepted at p<0.05 after the Bonferroni correction. ResultsThe gaps deviated from the set cement space by 3–13 µm on IOS scans (validation of virtual-fit algorithm). The internal gap of the design on the reference scan was not affected by cement spacing (Emerald S, p = 0.779; Medit i700, p = 0.205). The marginal gap in groups 70 and 70+20 was significantly lower than in group 140 in Emerald S (p<0.05). In Medit i700, it was lower in the 70+20 group than in the group 70 (p<0.01) and in the group 140 (p<0.05). Some Medit i700 scans exhibited high marginal gaps within group 70 but not in groups 70 and 140. The measured gaps correlated significantly (r = 0.51–0.81, p<0.05–0.001) with the conventional trueness but were 2.6–4.6 times higher (p<0.001). ConclusionVirtual-fit alignment can simulate restoration seating. A 20 µm marginal and 90 µm internal spacing could compensate for scan errors up to several hundred micrometers. However, 140 µm internal spacing is counterproductive. The conventional trueness method could only partially predict framework misfit. Clinical significanceThe virtual-fit method can provide clinically interpretable data for intraoral scanners. Emerald S and Medit i700 intraoral scanners are suitable for fabricating complete-arch fixed tooth-supported prostheses. In addition, a slight elevation of spacing at the margin could compensate for moderate inaccuracies in a scan.

Ameliorating the Effects of Phytochemical Substances on the Setting of Cement with Rice Bran in the Production of Particle Boards Using a Natural Accelerator

Ameliorating the Effects of Phytochemical Substances on the Setting of Cement with Rice Bran in the Production of Particle Boards Using a Natural Accelerator

Experimental Study on Effects of CO2 Curing Conditions on Mechanical Properties of Cement Paste Containing CO2 Reactive Hardening Calcium Silicate Cement.

Human survival is threatened by the rapid climate change due to global warming caused by the increase in CO2 emissions since the Second Industrial Revolution. This study developed a secondary cement product production technology by replacing cement, a conventional binder, with calcium silicate cement (CSC), i.e., CO2 reactive hardening cement, to reduce CO2 emissions and utilize CO2 from the cement industry, which emits CO2 in large quantities. Results showed that the carbonation depth, compressive strength increase rate, and CO2 sequestration rate increased as the CSC content increased, suggesting that CSC can be applied as a secondary cement product.

Increasing the Hydration Activity of Tricalcium Silicate by Adding Microdispersed Ettringite as a Nucleating Agent.

Tricalcium silicate (C3S) as a binder material has a decisive influence on the processes of hardening and strength gain of cements and concretes. One of the promising directions is the introduction of dispersed additives into cement mixtures, which allow micro-level control of the composition of hydration products and change the dynamics of the structure formation of cement stone. In this paper, the effect of a microdisperse ettringite additive on the kinetics of the hydration and hardening process of tricalcium silicate was studied. It was shown that ettringite crystals selectively adsorb Ca2+ and OH- ions from a saturated solution of calcium hydroxide, which contributes to the formation of hydrosilicate nuclei on their surface during cement hydration. Hydration of C3S in the presence of ettringite proceeds more intensively; the addition of ettringite contributes to an increase in the content of calcium hydrosilicates in hydration products at the initial stage of the process. Addition of 10 wt.% ettringite to C3S reduces the induction period of the beginning of the main phase of heat release by around two times and increases the amount of heat released on the 1st day of hydration by 15% compared to the control sample. According to electron microscopy data, it was found that during the first hours of hydration of modified C3S, a significant number of nuclei of fibrous particles of calcium hydrosilicates with sizes of 0.2-2 microns were formed on the surface of ettringite crystals. According to the results of kinetic modeling of the setting process of cement pastes using the Avrami-Erofeyev model, it was shown that in the presence of the addition of microcrystals of ettringite, the setting rate is characterized by a slowdown in nucleation, whereas for a sample without an additive, this process proceeds with an acceleration of the formation of solid-phase nuclei. Based on the comparison of kinetic results and mechanical measurements, it is concluded that needle crystals of ettringite during C3S hydration and cement stone hardening are preformed centers for the growth of hydrosilicate nuclei, and they also act as a reinforcing filler, increasing the bending strength of modified samples. The results of the work can be used in practice in the development of methods for controlling the processes of hydration and hardening of cements, as well as for controllable structure formation of cement stone which is important in particular for 3D printing of building products and constructions.

Fabrication of hydrophilic polymer-hybrid octacalcium phosphate blocks under wet condition based on cement setting reactions

Bioceramics, while offering excellent biocompatibility, are often compromised by their fragility and brittleness, especially under wet conditions. Even though recent hybrid processes combining biocompatible polymers and bioceramics have shown promise, complete mitigation of these challenges remains elusive. In this research, a biomimetic process was employed to mimic the structure of biological bone tissue. This led to the development of block materials composed of octacalcium phosphate (OCP) and sodium polyacrylic acid (PAA-Na) that display flexibility and resilience in wet conditions. Adjusting the PAA-Na concentration enabled the OCP-PAA-Na blocks to demonstrate superior mechanical strength when dry and increased flexibility when wet. Notably, these blocks expanded in aqueous solutions while preserving their structure, making them ideal for oral surgeries by preventing issues like blood flooding from implanted areas.

Favorable features of a calcium phosphate cement based on a metastable α ̅-tricalcium phosphate and reinforced by hydroxyapatite whiskers

The composition, impurities, ion substitutions, structure, peculiarities in crystallization and compressive strength were studied in the initial stage of setting (for 15 min) of a new cement based on a metastable -tricalcium phosphate and reinforced by various amounts (up to 15 wt%) of hydroxyapatite whiskers. The set cements were apatitic, highly nonstoichiometric with a Ca/P ratio below 1.5. The compressive strength increased more than twice (up to 8 MPa) at a whisker content of 4 wt% and then decreased again with increasing whisker content. The decline was associated with the growth of nanocrystals on the surface planes of whiskers and formation of micropores in the whisker vicinity caused by the consumption of the surrounding mother phase for the growth. It is expected that the micropores are favorable for the surrounding tissue to grow into enhancing the effectiveness of the set cement. The cement can primarily be used as accessible remedies for treatment of slightly-loaded bone defects.

Medium-term evaluation of the bond strength and dentin penetration of self-adhesive resin cements to root dentin.

Medium-term evaluate the bond strength and tag formation in root dentin using self-adhesive cements Maxcem Elite (MCE), Relyx U200 (RU2), SeT PP (SPP) and Megalink (MGL) compared to conventional cement Relyx ARC (ARC) for glass fibre post cementation. One hundred bovine incisors roots were endodontically treated and divided into 5 groups (n = 20) according to the cementation system: MCE, RU2, SPP, MGL and ARC. All cementation systems were evaluated at 24 h (1) and 12 months (2) after post cementation. Specimens from the cervical, middle and apical thirds of the root were submitted to push-out bond strength test and confocal laser microscopy to verify the dentin penetration. The adhesive failure mode was classified as adhesive, cohesive and mixed. Data were analysed by one-way ANOVA and Tukey tests (α = 5%). ARC-1 and ARC-12 showed the highest bond strength (P < 0.05). ARC showed the greatest tag extension, regardless of the third (P < 0.05). The most frequent failure mode in the 24-h analysis was cohesive, regardless of the cement used. For the 12-month analysis, mixed failure was the most frequent. Conventional cement (ARC) showed the highest bond strength and tag extension, regardless of the evaluation period. In all cementation systems, the bond strength decreased after 12 months. © 2023 Australian Dental Association.