Cementation Bonds Research Articles

Antifungal Ability of Novel Silane on Titanium Implant Surface

Titanium and its alloys are commonly used in dentistry for implants due to their strength, lightweight nature, durability, corrosion resistance, and biocompatibility. These implants can osseointegrate after surface treatments such as SLA, plasma-spray, and nanotubes, providing a stable foundation for prostheses. However, Candida albicans, an opportunistic fungal pathogen, can threaten the success of titanium dental implants, causing oral infections in vulnerable individuals. A dual novel silane blend of 3-acryloxypropyltrimethoxysilane (ACPS) and bis-1,2-(triethoxysilyl)ethane (BTSE) has been shown to improve the shear bond strength in resin cement bonds with titanium and ceramics. This study evaluated the effects of Candida albicans colonization on blended silane-coated SLA-Ti surfaces compared to non-coated SLA-Ti (positive control) and flat titanium (negative control). Candida albicans biofilms were cultured on all surfaces, and it was found that silane-coated SLA-Ti had significantly lower CFU counts than non-coated SLA-Ti. However, no significant differences were observed in the RT-PCR results. In conclusion, a combination of 1.0 vol% ACPS and 0.3 vol% BTSE shows promise as a silane coupling agent with potential antifungal properties for inhibiting Candida albicans proliferation.

Exploring alkali-source, pore-filling and cementation damage effects in cemented clay with typical industrial waste binders

Various industrial waste binders (IWBs) are being recycled in soil stabilization to save cement consumption. However, the coupled effects brought out by combined IWBs on stabilized soils are still unclear. IWBs are categorized into two typical categories (IWB-A and IWB-B) referring to their chemical role in this study. The alkali-source effect, pore-filling effect and cementation damage effect by IWBs in soil stabilization are explored. A series of mechanical and microscopic tests is performed on stabilized clay with different proportions of IWB-A and IWB-B. Moreover, initial water contents and cement contents of cement-stabilized clay are varied to examine the evolution of coupled effect with void ratio and cementation level. The results indicate that the alkali-source effect strengthens the cementation bonds and increases the early strength by 0.5–1.3 times, whereas the pore-filling effect improves the microfabric especially for the specimen with a large void ratio. The alkali-source effect increases soil cohesion cu at the pre-yield stage, and the pore-filling effect increases frictional angle φu at the post-yield stage. The cementation damage effect is remarkable at a low void ratio, which may result in many extruded pores among soil aggregates. The strength evolution with IWB proportions can be well stimulated by considering the coupled alkali-source effect, pore-filling effect and cementation damage effect. The optimal proportion of IWBs corresponds to an optimal combination of coupled effect.

Frost Resistance of Silicate Bricks

The article presents the results of a research frost resistance of silicate bricks one of the Russian factories produced in different periods. The change in appearance, weight and strength of silicate bricks during alternate freezing-thawing was evaluated. It has been established that silicate bricks, can meet high frost resistance grades F150-200, in terms of appearance, while the reduction in compressive strength does not exceed 9%. Some increase in brick strength at the initial stage of testing was noted, which is probably explained by the processes of carbonization of free calcium hydroxide and high-basic calcium hydrosilicates, accompanied by their recrystallization into low-basic ones, which is confirmed by the results of differential-thermal and X-ray phase analysis. It is concluded that the frost resistance of silicate bricks is decisively influenced by the mineralogical composition of the cementitious bond. High strength and frost resistance of silicate concrete is provided by the simultaneous presence of low-basic calcium hydrosilicates and α-C2S hydrate in the composition of the new formations. The condition for the formation of such composition of neoplasms is excessive content of lime in the composition of the raw material mixture.

Soft Clay Modified with Municipal Solid Waste and Stabilized with Nano-MgO for Pavement Subgrade and Embankment Fill Applications

Municipal solid waste (MSW) is the largest group of non-hazardous waste. Four percentages of MSW replacement (15 %, 25 %, 35 %, and 45 % by weight) were used for chemical modification of soft clay at 1, 14, and 28 days of curing. The MSW replacement at optimum (15 % and 25 %) to the clay enhanced unconfined compressive strength (UCS) and California bearing ratio (CBR) by 1.28 and 3.34 times, respectively. Also, the nanomagnesium (Nano-MgO) was used as an additive at small contents i.e., 0.25, 0.5, 0.75, and 1 % to improve the mechanical properties of MSW-soft clay blends. The optimum MSW replacement ratios with 1 % Nano-MgO significantly improves UCS and CBR of the soft clay when compared to clay stabilized with 1 % Nano-MgO. The UCS and CBR improvement mechanism was investigated via microstructural analysis of the MSW-soft clay stabilized with Nano-MgO. The improved structure of stabilized specimens was found to be due to flocculation, cation exchange, and cementation bond formation with brucite mineral. However, the X-ray diffraction tets results indicated the presence of the Palygorskite mineral in the specimen containing very high MSW replacement ratio, which retarded the Nano-MgO stabilization process. At optimum MSW replacement ratio (15 % and 25 %), Nano-MgO could effectively improve mechanical properties of soft clay for sustainable road construction.

Bonding Effectiveness of Saliva-Contaminated Monolithic Zirconia Ceramics Using Different Decontamination Protocols.

This research study investigated the effect of new decontamination protocols on the bonding capacity of saliva-contaminated monolithic zirconia (MZ) ceramics cemented with two different monomer-containing self-adhesive resin cements. Standardized tooth preparations (4 mm. axial height) were performed for eighty human maxillary premolars under constant water cooling system. Eighty monolithic zirconia crowns (Whitepeaks Supreme Monolith) (n = 8/10 groups) were manufactured by CAD-CAM. Specimens were kept in the artificial saliva at pH = 7.3 for 1 minute at 37°C except control groups. The specimens have not been prealumina blasted and grouped according to cleaning methods and resin cements: control groups (C) (no saliva contamination + GPDM + 4-META (N) (CN) and 10-MDP (M) containing resin cement (CM), alumina blasted (AL) + GPDM + 4-META (ALN) and 10-MDP containing resin cement (ALM), zirconium oxide containing universal cleaning agent (IC) applied + GPDM + 4-META (N) (ICN) and 10-MDP containing resin cement (ICM), pumice (P) applied + GPDM + 4-META (PN) and 10-MDP containing resin cement (PM), and air-water spray (AW) applied + GPDM + 4-META (AWN) and 10-MDP containing resin cement (AWM)). Monobond Plus was applied to all surfaces for 40 seconds before cementation. The thermal cycle was applied at 5,000 cycles after cementation. The crowns were tested in tensile mode at a speed of 1 mm/min. The mode of failure was recorded. SEM examinations were carried out at different magnifications. Data were analyzed using rank-based Kruskal-Wallis and Mann-Whitney tests. No significant differences were found between the surface treatments and between the two types of resin cements. Interaction effects between surface treatments and resin cements were found to be significant by two-way ANOVA analysis. ICM group resulted in significantly better bond strength results compared with CN. ICM was found to result in better bond strength results compared with PM. The combination of universal cleaning agent and 10-MDP containing resin cement had significantly the highest cementation bond strength values. The increasing order of mean tensile bond strength values of decontamination protocols was C < AW < P < AL < IC. The mean tensile bond strength of 10-MDP containing resin cement was slightly higher than GPDM + 4-META containing resin cement. Universal cleaning agents can be preferred as an efficient cleaning method with 10-MDP-containing cement after saliva contamination for better adhesive bond strength of 4 mm crown preparation height of monolithic zirconia ceramics.

An experimental study to investigate the mechanical behaviour of low plasticity fine-grained soil stabilized with different contents of lime and fly ash

ABSTRACT Shear strength, small and large strain stiffness moduli, and cyclic stiffness degradation of fine-grained soil with low plasticity (CL-ML) stabilized with different contents of lime and fly ash were investigated in this work. The results of static triaxial tests showed that adding fly ash to the soil-lime mixture increases significantly the compressive strength of the samples due to an increase in pozzolanic reactions. By varying fly ash up to 15% and lime up to 7%, an optimal composition with 5% lime and 15% fly ash was achieved, in which the shear strength was maximum. The results of the bender element tests also showed that the mixture of 5% lime and 15% fly ash has the highest maximum shear modulus. The results of the cyclic triaxial tests on the samples with the optimal composition; showed cyclic degradation of the stiffness due to the failure of cement bonds.

Nucleus accumbens dopamine release reflects the selective nature of pair bonds

In monogamous species, prosocial behaviors directed toward partners are dramatically different from those directed toward unknown individuals and potential threats. Dopamine release in the nucleus accumbens has a well-established role in social reward and motivation, but how this mechanism may be engaged to drive the highly divergent social behaviors directed at a partner or unfamiliar conspecific remains unknown. Using monogamous prairie voles, we first employed receptor pharmacology in partner preference and social operant tasks to show that dopamine is critical for the appetitive drive for social interaction but not for low-effort, unconditioned consummatory behaviors. We then leveraged the subsecond temporal resolution of the fluorescent biosensor, GRABDA, to ask whether differential dopamine release might distinguish between partner and novel social access and interaction. We found that partner seeking, anticipation, and interaction resulted in more accumbal dopamine release than the same events directed toward a novel vole. Further, partner-associated dopamine release decreased after prolonged partner separation. Our results are consistent with a model in which dopamine signaling plays a prominent role in the appetitive aspects of social interactions. Within this framework, differences in partner- and novel-associated dopamine release reflect the selective nature of pair bonds and may drive the partner- and novel-directed social behaviors that reinforce and cement bonds over time. This provides a potential mechanism by which highly conserved reward systems can enable selective, species-appropriate social behaviors.

Mechanical properties and micro-mechanism of improved shield tunnel muck with phosphogypsum and lime

Massive shield tunnel muck is being landfilled without effective use due to high moisture contents and poor engineering properties, which not only leads to soil resources waste, but also occupies a large amounts of land sources. In this study, industrial waste phosphogypsum (PG) was recycled to improve the tunnel muck with lime, and the improved muck is aiming to be used in subgrade filling. A series of laboratory tests, including compaction tests, unconfined compressive strength (UCS) tests, california bearing ratio (CBR) tests, resilient modulus tests and microscopic tests were carried out. The effects of PG, lime, carboxymethyl cellulose (CMC) and moisture contents on physical, mechanical and microscopic properties of improved muck were examined, respectively. Results indicate that the incorporation of lime and PG significantly improves the mechanical properties and water stability of shield tunnel muck generated in silt stratum. The performance of improved tunnel muck meets the requirement for subgrade filling. Notably, for a fixed total contents of lime and PG, the proportion of 3:1 lime/PG results in the best mechanical properties and water stability. The tunnel muck generated in silt stratum mainly consists of lamellar and layered structures, which contributes to stronger cohesion among soil particles and the hydration products. The CMC has the ability to create cementation bonds among soil particles and the hydration products of lime and PG, resulting in a denser gel network microstructure.

Mikrobiyolojik Yöntemle Çimentolanmış Kum Örneginin Üç Eksenli Kesme Davranışı Ve Mikroyapısının Incelenmesi

The use of bacteria induced calcite cementation for ground improvement presents a relatively new option for geotechnical engineers, one that has the potential to revolutionize the way that we improve soils to prevent liquefaction-induced damage. This technique uses non-pathogenic organisms which are found naturally in the soil environment to cement sand particles together at their particle-to-particle contacts. There is significant potential for a reduction in environmental concerns on various types of projects; in the long-term, this technique may also prove to be an extremely sustainable form of ground improvement. Consequently, the goal of the research described herein is to enhance the state-of-the-art with respect to our understanding of controlling biological cementation processes in soil. Bio-treatment of sand specimens was performed using a commonly encountered urea-producing soil microorganism called Sporosarcina Pasteurii (ATCC-6453). Microorganisms that were suspended in solution were introduced to the soil, and over time the microorganisms were supplied with necessary nutrients via cycling with a peristaltic pump. After bio-treatment, the specimens were back pressure saturated, isotropically consolidated, and sheared under undrained conditions. Scanning electron microscope (SEM) imaging was performed to examine the soil microstructure over a range of specimen curing periods to assess the nature of any cementitious bonds that may have formed.

Comparative Bonding Analysis of Computer-Aided Design/Computer-Aided Manufacturing Dental Resin Composites with Various Resin Cements

The use of dental resin composites adapted to computer-aided design/computer-aided manufacturing (CAD/CAM) processes for indirect tooth restoration has increased. A key factor for a successful tooth restoration is the bond between the CAD/CAM composite crown and abutment tooth, achieved using resin-based cement. However, the optimal pairing of the resin cement and CAD/CAM composites remains unclear. This study aimed to identify the optimal combination of a CAD/CAM composite and resin cement for bonding. A commercial methyl methacrylate (MMA)-based resin cement (Super-Bond (SB)) and four other composite-based resin cements (PANAVIA V5; PV, Multilink Automix (MA), ResiCem EX (RC), and RelyX Universal Resin Cement (RX)) were tested experimentally. For the CAD/CAM composites, a commercial polymer-infiltrated ceramic network (PICN)-based composite (VITA ENAMIC (VE)) and two dispersed filler (DF)-based composites (SHOFU BLOCK HC (SH) and CERASMART300 (CE)) were used. Each composite block underwent cutting, polishing, and alumina sandblasting. This was followed by characterization using scanning electron microscopy, inorganic content measurement, surface free energy (SFE) analysis, and shear bond strength (SBS) testing. The results demonstrated that the inorganic content and total SFE of the VE composite were the highest among the examined composites. Furthermore, it bonded highly effectively to all the resin cements. This indicated that PICN-based composites exhibit unique bonding features with resin cements. Additionally, the SBS test results indicated that MMA-based resin cement bonds effectively with both DF- and PICN-based composites. The combination of the PICN-based composite and MMA-based resin cement showed the best bonding performance.

Expansion and Mitigation of Alkali-Silica Reaction in Binary Blended Concrete Confining Potentially Reactive Aggregates

Without a cure but preventable, Alkali-Silica Reaction (ASR), dubbed the “Concrete Cancer,” happens when alkali in cement bonds with silica in aggregates to form an expansive gel. This research aims to investigate expansion and influence mitigation of ASR in concrete by identifying potentially reactive aggregates causing its onset and using binary blended cement to slow down unwanted gel expansions through the mitigative ability found in its fly ash component. This research also observed variations in expansive behavior and the physical changes that arose after the experiments. Aggregate samples were collected from different quarries in Davao, Philippines, denoted as Deposit A, Deposit B, Deposit C, and Deposit D. These deposits were tested according to the ASTM C1260: Accelerated Mortar Bar Tests (AMBT) to identify a reactive group. Three aggregate groups, Deposit A, Deposit B, and Deposit C, were tagged as reactive due to exhibiting more than a 0.1% increase in lengths, indicating unideal expansion. Additional sets of AMBTs were done for the identified aggregates using blended cement as a binder to test the combinations' ability to minimize expansion. This resulted in an average expansion decrease per set of approximately 78%, 82%, and 85% for A, B, and C, respectively, further strengthening the reputation of fly ash as an effective mitigating SCM against ASR.

Evolution in macro-micro properties of cement-treated clay with changing ratio of red mud to phosphogypsum

To investigate the effect of combined red mud (RM) and phosphogypsum (PG) in cement-treated clay, unconfined compressive strength (UCS) tests and isotropically consolidated undrained triaxial (ICUT) tests were performed to explore the effects of RM/PG ratio on mechanical behavior of stabilized clay. Moreover, x-ray diffractometer (XRD) tests, thermogravimetric analysis/differential scanning calorimetry (TG/DSC) tests and scanning electron microscopy (SEM) tests were employed to observe the evolution in microstructure with changing RM/PG ratios. The results indicate that the combined RM and PG play a significant role in cement-based hydration reactions. The UCS at early curing stages nearly doubles with an optimal proportion of 7.5 %RM and 2.5 %PG. The stabilized clay with high contents of RM exhibits a higher maximum deviator stress and a brittle behavior in undrained shearing process. As the PG content increases, the peak strength decreases but the ductility of the specimen increases remarkably. It is believed that the RM acts as an alkali activator on clay minerals whereas the PG mainly contributes to the generation of ettringite. The combined RM and PG not only promotes sufficient pozzolanic reactions and stronger cementation bonds, but also brings out a principally denser microstructure, though a few large pores can be observed due to expansion potential of ettringite. However, the microstructure of stabilized clay becomes much looser with a high content of PG. Partial amounts of PG are found non-reactive with inadequate active aluminium ions. The mechanical behavior of stabilized clay also gets worse concerning negative effects of impurities in PG.

Discrete-element method simulations of the seismic response of tunnels in deep granular deposit

The seismic response of tunnels constructed in a deposit of granular soil of depth greater than 20 m is examined in this paper. Three-dimensional discrete-element method (DEM) simulations were used to model the soil assembly and the tunnel lining. Soil particles were simulated as rigid spherical particles that are allowed to overlap at the contact points. The tunnel lining was modeled as a flexible system using a collection of particles that were glued together using cementitious bonds to mimic the physical properties of an actual tunnel. Free-field boundaries were utilized at the model’s lateral sides to prevent the propagating wave’s reflections back to the domain and enforce the free-field motion. The DEM computational framework was validated using published centrifuge test results. DEM simulation results reveal good agreement with the experimental centrifuge test results when subjected to the same input motion. Further simulations were carried out to investigate the seismic response of the system under different input motion characteristics. The dynamic earth pressure was monitored at certain points on the tunnel lining. It was found that the dynamic earth pressure and tunnel lining forces increased during seismic excitation and the final residual values were, in most cases, considerably larger than the initial static values. The results also showed that the maximum amplification factor, ground settlement and tunnel lining internal forces occurred close to the resonant frequency of the system.

Engineering properties of fine-grained red mud

ABSTRACT Basic engineering parameters of fine-grained red mud tailings were evaluated via laboratory tests; the coupled effect of mineralogy and microstructure was investigated by appraising the stress-deformation characteristics; and the static and seismic liquefaction susceptibilities were evaluated via critical state soil mechanics and empirical equations, respectively. Results indicated the presence of cementitious minerals without swollen clay minerals. The textural and compression properties were similar to those of clays, whereas the strength parameters were similar to those of sand. The stress-deformation curves show overall strain softening with a temporary strain-hardening curve at the beginning, which can be qualitatively explained by the coupled effect of the microstructure and mineral components. Hydroxysodalite precipitated at the contact points among the particles afforded microstructural cementation bonds, allowing the aggregates to resist external loads at the initial loading stage. Red mud presented strong resistance to static liquefaction but was potentially seismically liquefiable.

Stiffness of cold-recycled mixtures under variable deformation conditions in the IT-CY test

Stiffness modulus belongs to the most important properties describing the cold-recycled mixtures (CRM) in terms of their usability in road pavement structures. Previous research proved that this property is strongly dependent on the scheme and conditions of the test (temperature and time of loading) and the time that has passed since the compaction of the specimen or pavement layer. It is a result of the influence of two different types of bonds – hydraulic bonds from cement and bituminous bonds from bituminous emulsion or foamed bitumen. Research presented in this paper showed that the target horizontal deformation values selected during the stiffness modulus test have a strong impact on the obtained results as well. In this paper the popular Indirect Tensile Stiffness Modulus (ITSM) test on cylindrical specimen (IT-CY scheme) was used to show the dependence of the stiffness modulus values on the selected target horizontal deformation level. Research was conducted on four different CRM mixtures and three reference materials. The research proved that even for a narrow deformation range the CRMs do not present linear viscoelastic behavior and display very high effort of material even for typical test conditions. In consequence, they are very prone to failure. Research also proved that CRM mixtures present different rheological behavior than cement concrete or asphalt concrete, and more attention should be given to establishing proper test conditions. Based on the research, it was determined that the recommended target horizontal deformation in IT-CY test of CRM should be reduced to 3 µm.

Fracture of Interparticle MICP Bonds under Compression

Microbiologically induced calcium carbonate precipitation (MICP), as a promising reinforcement technique, has been investigated extensively through element and model tests. However, tests on the particle-scale behaviors of MICP bonds are rarely conducted yet, which constrains the development of constitutive and numerical models of MICP-treated sands. In this paper, a set of devices is designed to form MICP bonds between spherical quartz beads (SQBs) and spherical calcareous beads (SCBs) and investigate the microscopic compression behavior of the interparticle MICP bonds in comparison with portland cement (PC) bonds. The experimental results reveal that the PC bonds are the strongest, whereas the MICP bonds between SQB are the weakest. A higher cementation degree leads to higher strength and smaller dispersion among parallel specimens, while a larger interparticle distance causes smaller strength and greater dispersion. Identified with force–displacement curves and optical photos, the PC-treated SQB specimens are dominated by brittle failure, the MICP-treated SQB specimens can present ductile or brittle failure, and possible grain crushing is observed in the MICP-treated SCB specimens. Scanning electron microscopy (SEM) images suggest better interfacial bonding for the MICP-treated SCB specimens than for the MICP-treated SQB specimens. Gravity-related inhomogeneity is observed in the MICP bonds, whereas a homogeneous dense microstructure is observed in the PC bonds.

A deep learning workflow for weak reflection extraction in pitch-catch measurements in the cased hole

As a key technology to evaluate cement bonds in the cased hole, an advanced ultrasonic logging tool combines pulse-echo and pitch-catch measurements in which the latter one provides reflections from the cement-formation interface (called third-interface-echo [TIE]) to evaluate the bond condition and determine casing eccentering as well as cement velocity. However, the TIE would be weak and not easy to pick due to the eccentered tool and casing and it would overlap with the strong multiple reflections between the casing inner surface and the transducer-housing tool. We have developed a deep learning workflow to extract weak TIE from noisy data and to preserve its amplitude at the same time. First, we use synthetic waveforms from thousands of finite-difference simulations as initial training data sets to train a deep learning network, which is modified from a network in speech separation. Then, the trained model is used to predict the field data through an active-learning strategy. The improved network is further used to extract the weak TIEs, which are not easy to pick in the initial deep learning model. Finally, the TIE waves image is converted to a pseudovelocity image to obtain the minimum traveltime path by solving the eikonal equation. The shortest traveltime path is used as the TIE arrival time. In addition, a 3D visualization is used to display the borehole shape from the picked arrival time. The applications in synthetic data and data set from a calibration well illustrate a good performance of our workflow in which the weakest TIE extracted from the network can reach 50 dB compared to the maximum amplitude in the full waveform. The picked arrival times can be used to reconstruct a borehole shape.

Constitutive modeling of structured granular materials with anisotropic grain skeleton and cement bonds

Constitutive modeling of structured granular materials with anisotropic grain skeleton and cement bonds

A novel approach for nature gas hydrate separation: Downhole spiral-cyclone coupled hydraulic in-situ separation

The weakly cemented mixture slurry which is formed by the natural gas hydrate (NGH) solid-state fluidization mining method that is composed of natural gas hydrate, sediment and water. The downhole cyclone of NGH needs to deal with such problems as high viscosity, narrow radial working space, and difficult to adjust the split ratio. Directly using the conventional solid-liquid cyclone structure for downhole sand removal cannot obtain good separation performance. And the conventional separator does not have a tubular structure suitable for solid fluidization exploitation of NGH. Therefore, in order to solve the problem of weak cementation between NGH and sediment due to large sand production during NGH exploitation, this study proposes a new method to separate weakly cemented natural gas hydrate based on the principle of spiral-cyclone coupling. And the model of spiral-cyclone separator was established. This method can break weakly cemented solid-phase particles in the slurry, and the effective separation and removal of ultra-fine sediment with cross-scale and micron size. The research also designs and optimizes the separation device for NGH sand removal. According to numerical simulation and theoretical analysis, the separation efficiency is greater than 60% when the particle size is larger than 5 µm and the inlet velocity is between 2 m/s and 10 m/s. The research results show that the proposed spiral-cyclone separation method has the characteristics of high separation efficiency, strong sand removal, and can break the cementation bond between the sediment and natural gas hydrate, which is a high-efficiency solid-liquid separation technology.

An experiment-based cohesive-frictional constitutive model for cemented materials

Experiment-based damage laws at the contact bond level are often absent in the computational modelling of cemented materials using cohesive contact-bond models. In this paper, in-situ X-Ray Computed Tomography on element-scale cement bonds subjected to pure compression, shear and tensile loading was conducted to investigate their failure mechanisms and associated damage laws. A new cohesive-frictional constitutive model was subsequently developed using results obtained from X-Ray CT tests. The new constitutive model was capable of describing the behaviour of contact bonds subjected to complex loading conditions, including mixed-mode and compression damage. The new model was then implemented in an open-access Discrete Element Code (YADE) to simulate several challenging laboratory-scale tests (e.g., triaxial, Brazilian and Splitting tests) and very good agreements with the experimental data were achieved.