High Cement Research Articles

Efficacy of bioactive materials in preventing Streptococcus mutans-induced caries on enamel and dentine.

The study investigated the ability of bioactive materials used to restore enamel and dentine specimens to prevent caries. Enamel (n=50) and dentine (n=50) specimens were obtained from bovine incisors, prepared, and randomly allocated to one of five groups according to the restorative treatment: alkasite without adhesive system; alkasite with adhesive system; high viscosity glass ionomer cement; resin composite; no restoration; negative control group. Specimens were restored, exposed to a thermal cycling aging protocol, sterilized, and exposed to a cariogenic challenge induced by Streptococcus mutans and then submitted to surface and subsurface microhardness tests and polarized light microscopy to verify the caries lesion development in enamel or dentine surrounding the restorative materials. Data were analyzed using one-way ANOVA. In enamel and dentine, glass ionomer cement, alkasite without and with adhesive system presented a lower percentage surface microhardness loss than resin composite and negative control. Enamel subsurface microhardness presented no statistically significant differences between glass ionomer cement, alkasite without and with adhesive system. Glass ionomer cement also did not present statistically significant differences from resin composite and the negative control. In dentine, glass ionomer cement showed the highest subsurface microhardness values. In conclusion, bioactive restorative materials provide greater protection to enamel and dentine against surface caries development than resin composite.

Unveiling the strong coulomb interaction effect on electronic structures and mechanical properties of C4AF

AbstractThere are works have reported the crystal structures and mechanical properties of ferrite cement (C4AF) at the atomic scale with deviation owing to the omission of the Coulomb interaction effect (Ueff) between 3d electrons of Fe in C4AF. In this work, the DFT+U method was used to evaluate its effect on their electronic structures and mechanical properties of C4AF with two different phases I2mb (C4AF‐I) and Pnma (C4AF‐P). The FeO bonds of the two phases are all weaker and display Ueff due to the presence of Fe ions. The mechanical properties of C4AF calculated using DFT+U method significantly differ from those obtained without considering Ueff, in which the former shows lower inferior mechanical properties than the latter. This work presents a comparative study the effect of Coulomb interaction to the internal electronic structures and mechanical properties, which will pave the way for designing high hydration reaction cement and high toughness materials.

The very early-age behaviour of Ultra-High Performance Concrete containing ground granulated blast furnace slag

Ultra-High Performance Concrete (UHPC), despite being a relatively new kind of advanced cement-based material (featuring outstanding mechanical performance and excellent durability), has been deemed unsustainable due to its high cement content, thus increasing its carbon footprint. The large amounts of cement and silica fume (SF) can also raise both production costs and cracking risks due to the high early-age autogenous shrinkage. This paper addresses an innovative approach for developing a more sustainable UHPC involving an efficient application of ground granulated blast furnace slag (GGBS). Slags of two fineness levels are used, displaying a Blaine fineness of 420 m2/kg (SL1) and 700 m2/kg (SL2), respectively. These slags have been incorporated as volume replacements for 30% and 50% cement.The results analysis shows that it is indeed possible to produce SL2-based UHPC with a behavior similar to that of classical silica fume-based materials. The partial replacement of ordinary Portland cement (OPC) by 30% of GGBS (SL1 or SL2) improves workability, promotes the hydration reaction of cement and accelerates setting. In this case, the nucleation site effect of GGBS particles dominates; it seems to be directly correlated with the fineness of the slag used. Thus, the finer additions result in a significant acceleration of setting and hydration. The dilution effect is more sensitive at 50% of SL1 substitution. This prevailing effect delays the hydration reaction, prolongs setting times and decreases the peak of heat flow. In contrast however, this delay effect was not observed for the mixture containing 50% of SL2. Shrinkage measurements indicated that 30% of SL1 induces a slight reduction in early-age chemical and autogenous types of shrinkage. The most severe shrinkage is clearly found in mixtures incorporating 30% of SL2. This phenomenon may be due to the distribution of refined pores, which increases capillary tension. A more sustainable UHPC containing a high level of superfine slag (50%) with less autogenous shrinkage has been successfully produced.

Dynamic splitting behavior of ultra-lightweight cement composite with rubber and polyethylene fiber

The incorporation of fiber and rubber into concrete can enhance its tensile strength and impact resistance. In this study, a new rubberized ultra-lightweight high ductility cement composite (RULHDCC) was developed by mixing waste rubber particles and polyethylene (PE) fiber into an ultra-lightweight cement composite (ULCC). Previous studies have demonstrated that the effect of rubber and PE fiber results in satisfying static and dynamic compression performance. This study carried out a series of Split Hopkinson Pressure Bar (SHPB) splitting tests to investigate the impact of rubber and fiber on the tensile strength and splitting behavior of RULHDCC. The results showed that the splitting behavior of RULHDCC was significantly improved due to the synergistic effect of rubber and fiber, without much loss of compressive strength. The tension-Dynamic Increasing Factor (DIF) models are evaluated, and the limitations of the research are highlighted.

Influence of confining pressure on rubberised cement bound aggregate behaviour during static triaxial test

The aim of this research was to better understand the influence of adding waste rubber in cement bound aggregate (CBA) by testing both the unconfined and triaxial stress state. CBA with waste rubber was tested in this manner aiming to analyse influence of the confining pressure on the material behaviour. The results indicate that adding 20% rubber to a high cement content mix can assimilate the high stiffness caused by the high cement paste content, resulting in a mixture with increased cement paste content to facilitate in situ compaction. Additionally, a low confining pressure of 40 kPa has the most impact on the elastic properties/stiffness and it would be more appropriate to measure the CBA elasticity modulus with moderate lateral (confining) pressure. Finally, the practical implication of this research is that, in pavement mechanistic-empirical design, a correction of the measured uniaxial static modulus of elasticity by 10–15% should be adopted.

Comparative environmental assessment of low and high CaO fly ash in mass concrete mixtures for enhanced sustainability: Impact of fly ash type and transportation

The effect of fly ash type on the sustainability of concrete mixtures has yet to be quantified. This study aims to assess the environmental impacts of low calcium oxide (CaO) and high CaO fly ash in mass concrete mixtures from Thailand. The study analyzed 27 concrete mixtures with varying percentages of fly ash as a cement replacement (0%, 25%, and 50%) for 30 MPa, 35 MPa, and 40 MPa compressive strengths at specified design ages of 28 and 56 days. Sources of fly ash have been located between 190 km and 600 km away from batching plants. The environmental impacts were assessed using SimaPro 9.3 software. The global warming potential of concrete is reduced by 22–30.6% and 44–51.4% when fly ash, regardless of type, is used at 25% and 50%, respectively, in comparison with pure cement concrete. High CaO fly ash has more environmental benefits than low CaO fly ash when utilized as a cement substitute. The reduction in environmental burden was most significant for the midpoint categories of mineral resource scarcity (10.2%), global warming potential (8.8%), and water consumption (8.2%) for the 40 MPa, 56-day design with 50% fly ash replacement. The longer design age (56 days) for fly ash concrete showed better environmental performance. However, long-distance transport significantly affects ionizing radiation and ecotoxicity indicators for terrestrial, marine, and freshwater environments. Furthermore, the results show that a high cement replacement level (50%) may not always have a reduced environmental impact on mass concrete when considering long-distance transportation. The critical distance calculated based on ecotoxicity indicators was shorter than those calculated using global warming potential. The results of this study can provide insights for developing policies to increase concrete sustainability using different types of fly ash.

Interpretable machine learning model for autogenous shrinkage prediction of low-carbon cementitious materials

Supplementary cementitious materials (SCM) are key components of low-carbon cementitious materials. However, their effects, especially for the emerging high cement replacement ratio formulations, are sometimes very challenging to predict, leading to restrictions in most standards. Through advanced Machine Learning techniques, this study provides novel insights into the autogenous shrinkage properties of concrete containing various kinds of supplementary cementitious materials such as slag, fly ash, silica fume, calcined clay, and filler. Four machine learning models are optimized and their predictions are compared on a dedicated database, including ternary and quaternary cement blends. The Extreme Gradient Boosting (XGBoost) model exhibited the highest accuracy among these models. Interpretative tools such as SHAP analysis are then used to obtain novel information about the relative influence of the SCM on the autogenous shrinkage depending on their dosage. The model is finally compared to the recently modified versions of the B4 and the CEB analytical models to predict the autogenous shrinkage of unknown concrete formulations. The model showed significantly better predictions than the analytical models, and a web application is proposed, paving the way for precise and interpretable autogenous shrinkage predictions of cementitious materials incorporating SCM.

A new mathematical model of compressive stress-strain behaviour of low viscosity and high viscosity bone cement with different strain rates

A new mathematical model of compressive stress-strain behaviour of low viscosity (LV) and high viscosity (HV) bone cement has been proposed to capture large uniaxial deformation under constant applied strain rate by incorporating three-term power law. The modeling capacity of the proposed model has been validated using uniaxial compressive test under eight different low strain rates ranging from 1.39 × 10-4 s-1 to 3.53 × 10-2 s-1 for low viscosity and high viscosity bone cement. The well agreement between the model and experimental response suggests that the proposed model can successfully predict rate dependent deformation behavior for Poly(methyl methacrylate) (PMMA) bone cement. Additionally, the proposed model was compared with the generalized Maxwell viscoelastic model and found to be in good agreement. The comparison of compressive responses over low strain rates for LV and HV bone cement reveals their rate-dependent compressive yield stress behaviour along with a higher value of compressive yield stress of LV bone cement compared to HV bone cement. For example, at the strain rate of 1.39 × 10-4 s-1 the mean value of compressive yield stress of LV bone cement was found to be 64.46 MPa, whereas for HV bone cement it was 54.00 MPa. Moreover, the modeling of experimental compressive yield stress with the Ree-Eyring molecular theory suggests that the variation of yield stress of PMMA bone cement can be predicted using two processes Ree-Eyring theory. The proposed constitutive model might be useful to characterize large deformation behaviour with high accuracy for PMMA bone cement. Finally, both variants of PMMA bone cement also exhibit ductile-like compressive behaviour below the strain rate of 2.1 × 10-2 s-1, whereas above this threshold strain rate, brittle-like compressive failure behavior is observed.

Experimental Investigation on Reactive Powder Concrete by Partial Replacement of Cement with Different Pozzolanic Materials

Abstract: Reactive powder concrete (RPC) is one of the ultra-high performance concrete (UHPC). In RPC the coarse aggregate is eliminated and the micro particles like silica fume, quartz powder and sand are utilized in the production process. The high cement content and low water to binder ratio in RPC lead to shrinkage problems. Hence in this study, an attempt is made to produce eco-friendly RPC by replacing cement with 3 different pozzolanic materials from industrial wastes such as Fly ash, GGBS and Granite powder. To assess the viability of partial replacement of cement by pozzolanic materials, nine mixes have been arrived with 10%, 20% and 30% replacements. The fresh concrete property such as slump and the compressive strength are determined for all the mixes. By comparing the strength property the suitable alternate replacement material and replacement percentage for cement in RPC is found out

Improving the resistance of ultra-high-performance concrete against nuclear radiation: Replacing cement with barite, hematite, and lead powder

Ultra-high-performance concrete (UHPC) is concrete with a high cement content; thus, replacing the cement with other materials can contribute to the sustainable production of UHPC. This type of concrete offers desirable strength characteristics and durability, which makes it a possible deterrent for countering gamma rays. The addition of sustainable materials can reduce the thickness of the protective concrete structures and possibly provide the desired attenuation and half-life coefficients. The current study used barite, hematite, and lead powders as replacements for cement at contents of 10%, 15%, 20%, 25%, and 30%. Compressive and flexural strength tests were performed at 28 days of age and X-ray diffraction (XRD) tests at 180 days of age. To determine the radiation attenuation and half-life coefficients, sodium iodide crystals were used with a gamma-ray spectrometer from three sources (137Cs, 60Co, and 207Bi) at energies of 662, 1173, and 1333 keV. The results showed that the replacement of cement with barite and hematite powder at all percentages reduced the compressive and flexural strengths of the concrete. Their highest compressive strengths were at 10% cement content (106 and 109 MPa, respectively). Replacement of cement with 20% lead powder provided the maximum compressive and flexural strengths of 129 and 13.5 MPa, respectively. XRD analysis showed that the reason for the high compressive strength with 20% lead powder was the increase in the resistance phases and the decrease in ettringite. The highest attenuation and lowest half-life coefficients were for UHPC with 30% lead powder (0.23 cm-1 and 3 cm, respectively). This was about 53% higher than that of the UHPC-only sample, and its half-life coefficient was 35% lower. Therefore, UHPC with 30% lead powder was the most efficacious mix design for resistance to gamma rays.

Direct electric curing in high early-strength sodium citrate-doped Portland cement systems for sustainable energy saving applications

Faced with the increasingly severe energy crisis, it is very important to seek a low-energy-consumption accelerated curing method for prefabricated concrete element to save energy in the construction industry. In this research, direct electric curing (DEC) was used to produce high early-strength cement sample, and sodium citrate was used to improve the durability of the paste. Meanwhile, the effects of DEC and traditional accelerated curing methods on the early-age strength of paste and the corresponding energy consumption were compared and discussed. The results indicate that the DEC makes the early-age strength of cement paste higher than that of steam-cured sample, but its energy consumption is only 4% of that of steam curing. Although DEC increases the early-ages strength of the cement sample without reducing its long-term strength, it increases the water absorption and drying shrinkage deformation of the sample. Meanwhile, incorporating sodium citrate to the electric-cured paste can effectively improve its durability by refining the pore structure. The reduction in energy consumption also means a reduction in production costs and carbon emissions. This means that DEC can replace traditional accelerated maintenance methods and improve production & energy efficiency, which may bring a technological change to the modern construction industry.

Production of Advanced Foam Concrete using the Vibroturbulization Process

Foam concrete is a building material that has found widespread use in modern construction, which is cellular concrete with a spongy structure, formed by a large number of air bubbles locked in it. This structure is formed after hardening of a special mixture, which includes: purified water; sifted sand; high quality cement; foaming agent. Foam concrete is produced using a foam generator; foam generator and dispersant; by cavitation dispersion method; by high pressure. The disadvantages of these methods are: the resulting foam concrete blocks are susceptible to cracking and have a heterogeneous structure; use of a large amount of high-quality synthetic foaming agent; increased wear of equipment and the need to use a compressor. This article presents a completely new method for producing advanced foam concrete using the vibroturbulization process. In the developed method, a vertical vibration effect on a special mixture, which includes: purified water, sifted sand, high-quality cement, placed in a tank to produce foam concrete, in the vibroturbulization process mode, produces intensive foaming of the mixture by sucking all the air above the mixture in the tank onto its the bottom and intensive periodic float and immersion in the mixture of the resulting “swarm” of microdispersed air bubbles, which leads to uniform saturation of the mixture with microdispersed air bubbles. The resulting mixture, uniformly saturated with microdispersed air bubbles, is poured through a special tap installed at the bottom of the tank into special molds for hardening and obtaining advanced foam concrete with uniformly saturated microdispersed air bubbles of a given shape.

Study on the mechanism and controlling method for annulus pressure buildup problems in shale gas wells

The Annulus Pressure Buildup (APB) problems in shale gas wells is mainly caused by the crack at casing-cement interface. The stresses on casing-cement interface and cement-formation interface are calculated by the established model which the constrain of formation rock is considered. The elastic modulus of cement sheath has great effect on the stress on casing-cement and cement formation interface. The radial stress on interfaces changed linearly with fluid pressure. The cement rock is treated as a porous elastic material and the residual strain in cement sheath is mainly caused deformation or collapse of pore structure in the cement rock due to the large radial stress on interfaces. Ultimately, micro-annulus will be generated on the casing-cement interface due to the residual strain of cement sheath. High flexibility cement rock is proposed to decrease the radial stress on the interfaces which can reduce the residual strain of cement sheath. On the other hand, PABP is proposed to offset the decreased radial stress due to residual strain. A model for calculating the stress on interface by considering residual strain of cement sheath and PABP is established. The radial stress on the interfaces caused by PABP is quantitative calculated. The mechanism on how the method for solving APB problems in shale gas wells is clearly explained. The field application certificated the validity of method for solving the APB problems and it also proved the correctness of the calculation method.

The Development of Soil-Based 3D-Printable Mixtures: A Mix-Design Methodology and a Case Study

Concrete 3D printing is one of the newest technologies in the field of construction. However, despite the various opportunities that this technique offers today, it still has a high environmental impact, as most 3D-printable materials contain high amounts of cement. On the other hand, due to the large volumes of soil excavated each year across the world, there is a pressing need for proper management to dispose of it or reuse it efficiently. This study aims to develop sustainable and resistant 3D-printable materials with low environmental impact using excavated soil. Firstly, a series of tests were carried out to find the most appropriate superplasticizer and the amount required to develop the printable mixtures. Next, the extrudability and buildability were evaluated and verified to validate the printability of the developed mixtures. A 3D laboratory printer was also used to validate the printability of the mixtures on a larger scale. Then, the fresh and hardened properties of the printable mixtures were investigated. Three printable mixtures were developed, with the most environmentally friendly mixture having a soil content of 1602 kg/m3 and a cement content of 282 kg/m3. The mixtures demonstrated satisfactory characteristics and properties in both fresh and hardened states. On the one hand, the mixtures were extrudable and buildable at two laboratory scales. On the other hand, the mixtures presented sufficient compressive strengths, ranging from 16 MPa to 34 MPa, despite their high soil content and low cement content. In addition, their compressive strengths were found to be higher than the minimum strength required for structural concrete. Consequently, this study highlights the possibility of developing ecological, sustainable and resistant mixtures that can be used in 3D-printing construction applications using excavated soil.

Movable fluid evaluation of tight sandstone reservoirs in lacustrine delta front setting: Occurrence characteristics, multiple control factors, and prediction model

The tight sandstone, deposited in a lacustrine delta front setting, constitutes substantial new petroleum reserves. Tight sandstone reservoirs' fluid mobility directly affects oil production and recovery efficiency. Consequently, it is crucial to quantitatively and synthetically characterize fluid mobility. This study presented a detailed investigation of the movable fluid of the Yanchang tight sandstone in the Ordos Basin. Multiple experiments were conducted to investigate movable fluid, including casting and cathodoluminescence thin section, nuclear magnetic resonance, X-ray diffraction, and high-pressure mercury intrusion. According to pore-throat structure investigation with petrographical observations, delta front sandstone was divided into four types of lithofacies, pore-throat structure, and three pore-throat spaces (nano-scale, submicron, and micron), which correspond to various occurrence characteristics of the movable fluid. The result shows that the fluid mobility of the micron pore-throat space is higher than the sub-micron scale, and the nano-scale is the lowest. The fluid mobility is driven by petrophysical property, pore-throat structure, diagenetic mineral, lithofacies, and sandstone strata pattern. With the deterioration of the pore-throat structure and petrophysical property, fluid mobility gradually decreases. Movable fluid content significantly correlates with quartz and feldspar content, showing that residual intergranular and feldspar dissolved pores can significantly improve fluid mobility. On the contrary, it is negatively correlated with clay and carbonate cement content. The carbonate cementation and clay mineral filling increase the proportion of nano-scale pore-throat, leading to the deterioration of the reservoir quality and pore-throat structure. Detailed researches on the spatial distribution of fluid mobility show it related to sandstone bed thickness, mudstone proximity, and mudstone/formation ratio. Typically, medium-grained sandstones forming thick beds in mudstone-poor sequences are commonly low in carbonate and clay mineral cement and highest in movable fluid content. In contrast, fine-grained sandstones occurring as thin beds or located near the mudstone-sandstone interface in mudstone-rich sequences generally exhibit high carbonate and clay cement. Hence, its movable fluid content is lowest. The frequent material exchange between sandstone and adjacent mudstone prompts the enhancement of the cementation of clay and carbonate minerals, which is a devastating factor for fluid mobility. The proposed model for predicting fluid mobility can be used for similar delta front sandstones of other lacustrine basins. These findings provide new insights into predicting the best reservoir sandstones with high fluid mobility and effectively exploiting tight sandstone reservoirs.

Effect of graphene oxide and functionalized carbon nanotubes on mechanical and durability properties of high volume fly-ash cement nanocomposite

In the current investigation, the effect of Graphene Oxide (GO) and Functionalized Carbon Nanotubes (FCNTs) on the mechanical and durability properties of High Volume Fly-ash (HVFA) cement nanocomposite. The two control samples are fabricated including OPC-C and HVFA-C, whereas, the GO (0.005, 0.01, 0.02, and 0.04% by weight of binder) incorporated samples are called HVFA-GO-CNCs and for FCNTs (0.005, 0.01, 0.02, and 0.04% by weight of binder) incorporated samples are named as HVFA-FCNT-CNCs. It was observed the addition of 0.02% GO and 0.02% FCNTs in HVFA cement nanocomposite improved compressive (37.21, 27%) and tensile strength (61.71, 41.93%) as compared to the control (HVFA-C) at a curing age of 90 days. Electrical resistivity for all mixes of HVFA-GO-CNCs has been increased with increasing dosages of GO, while in the case of HVFA-FCNT-CNCs decreased with increasing dosages of FCNTs. The capillary water absorption test results observed that incorporating the GO and FCNTs into the HVFA cement nanocomposite decreased water absorption with increasing dosages of GO and FCNTs. After acid attack on HVFA-GO-CNCs and HVFA-FCNT-CNCs, compressive strength was decreased and after sulphate attack on HVFA-GO-CNCs and HVFA-FCNT-CNCs, compressive strength was found to be increased as compared to water cured sample, at 90 days of curing. In this study, GO significantly improves compressive, tensile strength, apparent electrical resistivity, reduces capillary water absorption, and more resistant to acid/sulphate attack of HVFA cement nanocomposite as compared to the FCNTs. So, the current study provides a suitable path for the production of eco-friendly, cost-effective, better mechanical properties, and more durable building materials.

リサイクルセメントを用いた高強度モルタルの圧縮強度に関する基礎的研究

In this study, compressive strength of high strength mortar using cement-based powder extracted from sludge separated from ready-mixed concrete was examined for the purpose of assisting effective treatment of returned concrete. As far as the mortar with a W/B of 30% was compared, the mortar with a high recycled cement replacement rate of over 75% took a longer time to flow down and tended to have a higher viscosity than the other mortars. And, it was found that the compressive strength of mortar using 100% recycled cement was about 0.7 to 0.8 that of mortar using ordinary Portland cement.

Mechanical properties and disintegration behavior of EICP-reinforced sea sand subjected to drying-wetting cycles

Enzyme-induced carbonate precipitation (EICP) has emerged promising in various geotechnical applications, and has been presented as an alternative to the traditional cementitious materials-based ground improvement method. However, the study on mechanical properties and disintegration behavior of EICP-reinforced sea sand subjected to drying-wetting cycles are limited. This study investigated the mechanical properties and disintegration behavior of EICP-reinforced sea sand against the impact of drying-wetting (D-W) cycles. The uniaxial compressive strength (UCS) tests were performed to discuss the effect of drying-wetting cycles on the mechanical behavior of EICP-treated sea sand. The disintegration tests were conducted on EICP-treated sea sand to investigate the disintegration resistance of bio-cemented samples with various cementation levels. The microstructures of samples before and after disintegration were examined to disclose the disintegration mechanisms of EICP-reinforced sea sand. D-W cycles significantly affect the mechanical properties of EICP-reinforced sea sand, with UCS decreasing by 63.7% after undergoing 15 D-W cycles. The disintegration resistance index of specimens with a lower cementation level decreases significantly under the effect of D-W treatment. The higher disintegration resistance of specimens with higher cementation can be attributed to more crystals with better crystallinity formed in the contact point between sand particles within specimen. The crystals formed by soybean husk urease are mainly calcite and the crystallinity of spherical calcites would gradually change into larger rhombic calcite with further bio-grouting. The crystal with poor crystallinity is susceptible to the effect of D-W treatment, resulting in the obvious disintegration of EICP-reinforced sea sand. Overall, this study is expected to provide useful guidance on the long-term stability and drying-wetting disintegration mechanisms of EICP-reinforced sea sand.

Emerging Tenera oil palm shell concrete: Mix design and cost analyses

The utilization of oil palm shell (OPS) in concrete dates back since four decades ago. While most research has only been done on the Dura-OPS as coarse aggregate in concrete, few research has been done on Tenera-OPS. The Tenera-OPS is obtained by a hybrid crossbreeding between Dura and Pisifera type fruits to obtain a thinner shell in the palm oil fruit to produce 30% more palm oil. Tenera-OPS has different physical properties compared to Dura-OPS, which could alter the mechanical behaviour of concrete. Therefore, this paper has studied mix designs of Tenera-OPS concrete (Tenera-OPSC) to investigate its physical characteristics, and compressive strength and has compared to those of Dura-OPSC from literature. It has been found that compressive strength of 20.24 MPa could only be produced with very high cement content of 1050 kg/m3. This study has shown that the compressive strength of Tenera-OPSC is reduced by 55 – 72% by using the most common acceptable mix design used for Dura-OPSC. It has been found that Tenera-OPS in concrete swells and shrinks during the hardening process which causes de-bonding between the Tenera-OPS and the cement matrix, which is believed to be the main reason for the lower compressive strength. A cost analysis was also done to compare the costs between Tenera-OPSC and normal weight concrete (NWC) of similar grade. The cost of Tenera-OPSC has been found to be 2% lower than that of NWC.

α-Tricalcium phosphate cement reinforced with silk fibroin: A high strength biomimetic bone cement with chloride-substituted hydroxyapatite

In the past decades, bone defects have become an increasing factor in the development of disability in patients, impacting their quality of life. Large bone defects have minor chances to self-repair, requiring surgical intervention. Therefore, α-TCP-based cements are rigorously studied for the development of bone filling and replacement applications due to the possibility of application in minimally invasive procedures. However, α-TCP-based cements do not present adequate mechanical properties for most orthopedic applications. The aim of this study is to develop a biomimetic α-TCP cement reinforced with 0.250–1.000 wt% of silk fibroin using non-dialyzed SF solutions. Samples with SF additions higher than 0.250 wt% presented complete transformation of the α-TCP to a biphasic CDHA/HAp-Cl material, which could enhance the osteoconductivity of the material. Samples reinforced with concentrations of 0.500 wt% SF showed an increase of 450% of the fracture toughness and 182% of the compressive strength of the control sample, even with 31.09% porosity, which demonstrates good coupling between the SF and the CPs. All samples reinforced with SF showed a microstructure with smaller needle-like crystals when compared to the control sample, which possibly contributed to the material's reinforcement. Moreover, the composition of reinforced samples did not affect the cytotoxicity of the CPCs and enhanced the cell viability presented by the CPC without SF addition. Hence, biomimetic CPCs with mechanical reinforcement through the addition of SF were successfully obtained through the developed methodology, with the potential to be further evaluated as a suitable material for bone regeneration.