CaCO3 Whisker Research Articles

Enhancing interlayer bonding strength of 3D printed ternary geopolymer using calcium carbonate whiskers spray

Weak interlayer bonding, especially induced by a long period of printing interruption, is one of the major concerns for 3D printing concrete. The effect of CaCO3 whiskers suspension (CWS) spray and printing time interval on the interlayer bonding of 3D printing fly ash-granulated blast furnace slag-steel slag based geopolymer was investigated with splitting tensile strength and direct shear strength tests. The underlying mechanisms were explored based on the characterization of micromorphology, porosity, surface roughness and reaction kinetics of interlayer area. It was revealed that the CWS spray at appropriate concentrations can significantly improve the interlayer bonding of geopolymer printed at extended printing intervals, with 0.05 g/mL of CWS increasing the shear strength up to 71% at 60 min and 0.10 g/mL of CWS increasing the splitting tensile strength by 40% at 40 min. The CWS at proper concentrations could replenish the interlayer moisture, fill the interlayer voids and provide nucleation sites for geopolymerization and hydration products, i.e., N(C)-A-S-H and C-S-H gels. However, excessive CaCO3 whiskers or water content was harmful to the interlayer bonding. As the reaction process and microstructure of 3D printed ternary geopolymer were synergistically impacted by the printing time interval, residual water content, compensated moisture and CaCO3 whisker reinforcement, the mix of CWS spray should be carefully designed to optimize its effectiveness on the interlayer strengthening.

Reinforcement effects on the tensile properties of seawater sea-sand engineered cementitious composites reinforced with multi-scale hybrid fibers

The preparation of seawater sea-sand engineered cementitious composites (SS-ECC) holds great potential for development in coastal and marine infrastructure. To improve its compressive strength and tensile properties, this study investigated the crack characteristics, micro-mechanics, fibers reinforcement index, and micro-structure of SS-ECC using a multi-scale hybrid fibers system consisting of CaCO3 whiskers, PE fibers, and stainless steel fibers (SSF). The aim was to gain an in-depth understanding of the reinforcement effects of multi-scale hybrid fibers. The results showed that CaCO3 whiskers increased the number of cracks and the stability of crack evolution in SS-ECC during the ultimate tensile state by bridging the matrix micro-cracks, improving the matrix micro-structure, and filling the interfacial transition zones between the macroscopic fibers (PE fibers and SSF) and the matrix. Additionally, it reduced the crack width and spacing. These combined effects increased the compressive strength, tensile strength, and tensile strain capacity of SS-ECC by 12.8%, 15.7%, and 11.9%, respectively. Finally, the reinforcement effects of multi-scale hybrid fibers were analyzed based on the pseudo-strain hardening performance indices, fibers reinforcement index, and hybrid coefficient. This analysis provides reference and insight for the design of multi-scale hybrid fibers SS-ECC with a high comprehensive performance (σcσtε/w) index.

High-strength high-ductility seawater sea-sand Engineered Cementitious Composites: Mechanical properties, cracking behavior and micro-mechanics

This study developed strain-hardening seawater sea-sand engineered cementitious composites (SS-ECC) with both high-strength and ultra-high tensile ductility for the first time using CaCO3 whiskers (CW). The developed SS-ECC exhibited a compressive strength of 132.7 MPa and successfully pushed the ultimate tensile strain capacity over 10 %. Investigations into crack characteristics and micro-mechanics were conducted to analyze in depth the obtained tensile performance. The results showed that the incorporation of 0.3 vol% CW increased the degree of crack saturation and decreased the crack width, leading to a further increase in the ultimate tensile strain capacity. With CW dosage increasing from 0.3 vol% to 0.8 vol%, the compressive strength increased significantly, but the ultimate tensile ductility decreased. In addition, this study took into account the effects of CW and PE fibers in the micro-mechanical model and theoretically explained the synergistic effect of CW and PE fibers on the enhancement of tensile performance of SS-ECC through the obtained PSH indices. The finding provides new insights into the production of high-cost efficiency and high overall performance index (fcftε/w) for ultra-high ductility SS-ECC, with promising applications in sustainable marine infrastructures.

Tensile properties and constitutive model of cost-effective multiscale hybrid fiber reinforced strain hardening cementitious composites

To enhance the mechanical properties and cost-effectiveness of conventional polyvinyl alcohol fiber reinforced strain hardening cementitious composite (PVA-SHCC), a modified version called multiscale hybrid fiber reinforced SHCC (MsHySHCC) was developed. This new composite incorporates a combination of steel fiber, PVA fiber and calcium carbonate (CaCO3) whisker. Uniaxial direct tensile behaviors (stress-strain relationship, tensile strength, tensile deformation capacity and tensile toughness) of designed MsHySHCCs were investigated and evaluated. The results show that the PVA fibers dominate the ductile behavior and the steel fibers and CaCO3 whiskers effectively affect the strength of MsHySHCCs. The PVA fibers can be partially replaced by CaCO3 whisker and steel fiber, along with an increase in tensile strength and ductility of designed composites. The findings suggest that the configuration of MsHySHCC proves to be a viable approach in simultaneously enhancing the strength and ductility of PVA-SHCC. A semi-theoretical prediction model for tensile constitutive relationship was derived. The comparison of the theoretical results with the experimental data shows that this semi-theoretical model is applicable for determining the tensile constitutive relationship of PVA-SHCCs and MsHySHCCs.

Preparation and Mechanism of Calcium Carbonate Whiskers from DoLOMITE Refined Solution

AbstractThe preparation of calcium carbonate whiskers by gas‐liquid contact method using low‐grade dolomite refining solution and CO2 as raw materials has attracted widespread attention. The effects of reaction temperature, Mg2+ concentration and pH value on the morphology, particle size, aspect ratio and crystal form of CaCO3（Calcium carbonate） whiskers are investigated in detail. SEM (Scanning Electron Microscope) and XRD (X‐ray powder diffraction) are combined to analyze the calcium carbonate whiskers. The results demonstrated that under the conditions such as 100 °C, Mg2+ concentration of 0.05 mol L−1 and pH value of 9.5, calcium carbonate whiskers with uniform distribution, aspect ratio of 15–20, and purity of 99.38% can be prepared. Through Material Studios simulation software and critical nucleation energy analysis, it is confirmed that the morphology of calcium carbonate whiskers emerged to be a long hexagonal prism. Mg2+ in the refined solution would adhere to the surface of calcium carbonate during carbonization, inhibit the formation of calcite phase, and promote the growth of face clusters connected by vertex angles between CaCO3 crystals. The initial pH condition determines the solubility of CO32− and the supersaturation of the solution, which in turn affected the formed calcium carbonate crystal form.

Synergistic effect of PTB emulsion, CaCO3 whisker and Nano-SiO2 on the properties of cement-based materials

With the rapid development of the civil engineering industry, performance requirements for building materials are also increasing rapidly. It is particularly critical to improve the performance of cement-based materials using admixtures. In this study, the synergistic effect of PTB (COMPAKTUNA.PRO) emulsion, calcium carbonate whisker (CaCO3 whisker) and nano-silica (nano-SiO2) on material properties was analyzed. Macroscopic properties such as rheology, compressive strength, flexural strength, durability, bond strength, and permeable pressure were tested. Microstructures were analyzed using the porosity, hydration heat, X-ray diffraction, and scanning electron microscopy methods. The results revealed that the PTB emulsion, CaCO3 whiskers, and nano-SiO2 increased the plastic viscosity and yield stress of the cement. When the nano-SiO2 content was high, the fluidity of the slurry decreased significantly. Overall, PTB emulsion, CaCO3 whisker and nano-SiO2 can improve the strength, durability, bond strength, and permeability of composite materials. PTB emulsions can prolong the hydration process, resulting in low early strength and reduced compressive strength. However, they play a key role in terms of improving durability, bond strength, and permeability pressure. CaCO3 whiskers yield slight improvements in various properties. Nano-SiO2 can promote the hydration rate and hydration effect, thereby improving the strength, compactness, and properties of composite materials. Performance can be optimized by leveraging these synergistic effects and each material has its own unique advantages and limitations. In engineering applications, critical properties should be considered when selecting appropriate admixture contents. This study aimed to improve various properties and to develop materials that are suitable for the complex environment of underground engineering.

Rheological properties of cement-based slurry and evaluation of rheological model: Influence of particle size and shape

With the continuous development of mineral admixtures and additives, the influence of various factors on the rheological properties of cement-based slurry remains unclear. In this study, the effects of particle size, particle shape, shear rate, and time on the rheological properties were analyzed. The rheological curves were determined using an RST-SST rheometer and fitted with the Bingham model, Modified Bingham model and Herschel-Bulkley model, respectively. The rheological parameters were evaluated. The results showed that the effect of particle size on the rheological properties is much greater than that of the particle shape. The small particle size is evidently affected by the shear rate, and the rheological parameters increase with time. The three rheological models can well describe the samples containing microfine cement (MC), fly ash (FA) and calcium carbonate whisker (CaCO3 whisker). The sample containing nano-silica (nano-SiO2) requires special analysis. The yield stress predicted by the Bingham model is the highest, whereas that predicted by the Herschel–Bulkley model is the lowest. The plastic viscosity predicted by the Bingham model is lower than that predicted by the modified Bingham model. The rheological index (n) of the Herschel–Bulkley model can effectively characterize the degree of shear thinning. The three rheological models demonstrate their characteristics and advantages, and an appropriate rheological model should be selected to evaluate the rheological parameters according to the requirements. The research aims to provide theoretical support for the analysis of rheological properties and the selection of rheological models.

Enhancement in strength and toughness of ultra-high performance concrete (UHPC) from micron- and nano-scale

The employment of multi-scale materials was considered the most effective and practical way to strengthen and toughen ultra-high performance concrete (UHPC). In this work, three types of enhancement materials at different scales (i.e., steel fibers on millimeter-scale, CaCO3 whiskers on micron-scale, and graphene oxide on nano-scale) were used to prepare a series of steam- and autoclave-cured UHPC. The dynamic elastic modulus, flexural load-deflection response, and compressive stress-strain behavior of the prepared UHPC were investigated, with special attention devoted to the effect of the enhancement materials on the flexural and compressive toughness of UHPC. The test results show that incorporating CaCO3 whiskers could enhance the dynamic elastic modulus of UHPC, but the effect of graphene oxide on the dynamic elastic modulus fluctuated. Under flexural and compressive behaviors, improvements in strength, energy absorption capacity, and toughness index could be found after incorporating CaCO3 whisker or/and graphene oxide. The best improvements of strength and energy absorption capacity were obtained through the hybrid of CaCO3 whisker and graphene oxide. But the hybrid of CaCO3 whiskers and graphene oxide could not necessarily further promote the improvement of the toughness index. Moreover, the hybrid effect for the performance parameters was analyzed, and the strengthening and toughening mechanisms were discussed based on microscopic observation. Overall, this work could provide a valuable reference for UHPC strengthening and toughening at the micron- and nano-scale.

Uniaxial tensile properties of multi-scale fiber reinforced rubberized concrete after exposure to elevated temperatures

With the rapid development of transportation and population growth, there is a surge hike in demand for automobile tires. Waste rubber disposal has become a big environmental concern worldwide due to the non-biodegradability of waste rubber. Based on the previous literature, waste rubber has great potential to make green concrete. However, the mechanical behavior of concrete, especially the tensile strength after being heated, will be reduced by adding waste crumb rubber. To improve the residual tensile behavior of rubberized concrete, steel fibers, PVA fibers (or PE fibers), and CaCO3 whiskers were added to make green concrete with better fire resistance. This study investigated the influences of the crumb rubber and multi-scale fibers on the failure mode, first cracking strength and strain, ultimate strength and strain, and the stress-strain relationships of MSFRRC subjected to elevated temperatures (up to 800 °C). In addition, the damage evolution of rubberized concrete under uniaxial tension was studied by the acoustic emission (AE) technique. Results show that specimens without fibers exhibited a single straight crack and a brittle failure. Adding crumb rubber could not improve the brittleness of concrete and eliminate explosive spalling. However, the brittleness of rubberized concrete could be improved and a multi-cracking behavior could be achieved by incorporating multi-scale fibers. Meanwhile, the ultimate strength decreased significantly when the crumb rubber volume replacement ratio increased from 0% to 30% since the increase in the porosity of the concrete specimen. The incorporation of multi-scale fibers could mitigate the strength loss and contribute to the first cracking strength, ultimate strength, and strain-hardening capability. The tensile strength of MSFRRC was enhanced by 54.4%–64.3% and the ultimate strain increased by 26.9–50.4 times. Nevertheless, the strain-hardening capability was eliminated owing to the weakened interfacial bond between the steel fiber and the matrix and the decomposition of PVA fibers when the temperature reached 400 °C. In addition, the large and medium capillary pores were reduced due to the additives of multi-scale fibers and the content of mesopores increased. Furthermore, the empirical formulas to predict the residual uniaxial tensile stress-strain relationship of MSFRRC considering parameters of crumb rubber, multi-scale fibers, and elevated temperatures were proposed based on the test results.

Influence of multi-scale fiber on residual compressive properties of a novel rubberized concrete subjected to elevated temperatures

Green and environment-friendly rubberized concrete has attracted extensive attention from scholars worldwide. However, the incorporation of crumb rubber can weaken the mechanical properties of concrete, particularly when it is subjected to elevated temperatures. To improve the residual compressive performance of rubberized concrete, a novel multi-scale fiber reinforced rubberized concrete (MSFRRC) is developed by adding calcium carbonate whiskers, polyvinyl alcohol (PVA) fibers, and steel fibers. In this study, 10%, 20%, and 30% of the sands are substituted by the same volume of crumb rubber with sizes between 0.4 mm and 0.8 mm. The impacts of the crumb rubber content and multi-scale fiber on the residual Young's modulus, axial compressive strength, peak strain, stress-strain curve, and compressive toughness of MSFRRC after being heated up to various temperature levels (25 °C, 200 °C, 400 °C, 600 °C, and 800 °C) are discussed. Also, the failure mode combined with the acoustic emission technology and the thermal effect on the microstructure of rubberized concrete specimens, are investigated. Results reveal that incorporating multi-scale fiber can effectively restrain the development of cracks and explosive spalling under high temperatures. Besides, it can cover the strength loss caused by crumb rubber and impose a positive effect on resisting thermal damage. The compressive strength of MSFRRC can be enhanced by about 5.4%–19% with the incorporation of different fibers. The results show that specimens without fibers suddenly fail once the peak stress is reached and exhibit brittle fracture. However, the brittleness can be improved by adding multi-scale fibers. It can be observed that, after exposure to 800 °C, the damage of MSFRRC can develop at the early loading stage and develop in the whole loading process, showing a relatively ductile fracture. Meanwhile, the pore structure can be refined by adding CaCO3 whiskers and the addition of multi-scale fibers can slightly increase the porosity and cannot restrain the heating-induced pore coarsening. Furthermore, the empirical formulas to predict the residual stress-strain relation of MSFRRC under uniaxial compression are proposed by considering crumb rubber, multi-scale fibers, and high temperature.

Experimental and analytical study of steel–PVA hybrid fiber-reinforced mortar containing CaCO3 whiskers subjected to freeze–thaw cycles

Experimental and analytical study of steel–PVA hybrid fiber-reinforced mortar containing CaCO3 whiskers subjected to freeze–thaw cycles

The Mechanical Properties of Mortar Blended with Steel-PVA Hybrid Fibers and CaCO3 Whiskers Under Freeze/Thaw Cycles Condition

The Mechanical Properties of Mortar Blended with Steel-PVA Hybrid Fibers and CaCO3 Whiskers Under Freeze/Thaw Cycles Condition

RETRACTED: Effect of CaCO3 whiskers on tensile properties of ultra-high-performance engineered cementitious composites

Ultra-high-performance engineered cementitious composite (UHP-ECC) is expected to become an ideal construction material for its superior mechanical properties. However, the high cost of UHP-ECC, especially the use of expensive synthetic fibers, limiting its extensive engineering application. To address this, cheap calcium carbonate (CaCO3) whiskers were utilized to partially replace polyethylene (PE) fibers. The various volume fractions of PE fibers and CaCO3 whiskers were adapted to possess different tensile properties (ultimate tensile stress, strain capacity, crack number, and strain energy). The results indicated that the decrease in PE fiber content from 2% to 1.5% significantly deteriorated tensile properties of UHP-ECC (the decrease of 24.95% in tensile strength and 49.47% in strain capacity). However, the partial replacement of PE fibers by CaCO3 whiskers could effectively mitigate the performance degradation and improve the stable multiple cracking behavior. Especially, the tensile ductility of UHP-ECC with a combination of 1.75% PE fibers and 0.5% CaCO3 whiskers was 45.19% higher than that of UHP-ECC with mono 1.75% PE fibers, and also 102.5% higher than that of control group (2% PE fibers). Scanning electron microscopy images confirmed the synergistic effect of PE fibers and CaCO3 whiskers at the microscopic level. In according with micromechanics, the addition of CaCO3 whiskers could effectively improve the complementary energy of UHP-ECC by micro cracking arresting, which increased the pseudo strain hardening values and thus leading to the enhancement in tensile ductility of UHP-ECC. In addition, the hybrid fiber reinforcing index (RIv) had a positive correlation with the tensile properties of UHP-ECC. Therefore, a semi-empirical formula based on RIv could be adopted for the property prediction of UHP-ECC with different combination of PE fibers and CaCO3 whiskers.

The investigating on mechanical properties of engineered cementitious composites with high ductility and low cost

The engineering application of engineered cementitious composites(ECC) has always been limited by its cost, which mainly due to the high price of imported PVA fibers. In order to balance the mechanical properties and cost of ECC, this study presents an engineered cementitious composites with high ductility and low cost. The compressive strength, uniaxial tensile strain and uniaxial tensile strength of this ECC were 21.33 MPa, 5.10%, and 2.93 MPa, respectively. The high ductility and low cost of this ECC are mainly attribute to the reasonable combination of four materials, including PVA fibers, fly ash, CaCO3 whiskers(CW) and nano-CaCO3(NC). The optimal mixing ratio of the four materials is that the content of PVA fiber is 1.3%(vol%), the mass ratio of fly ash to cement is 3.0, 1% CW(vol%), and 1% NC(wt.%). The average crack width and the maximum crack width on the surface of the tensile specimen prepared according to the optimal mixing ratio can be controlled at about 42 μm and 100 μm, respectively. This excellent crack control ability mainly comes from the crack inhibition effect of PVA fibers and CW. Compared to classic ECC-M45, the total value coefficient and total cost of the specimens prepared according to the optimal mixing ratio were 112.59% and 36% of that of ECC-M45, respectively. And the designed ECC with high ductility and low cost has the applicability of engineering application, which has been proved by comparison with the mechanical properties of a sprayable ultra high toughness cementitious composites (UHTCC) that has been applied in practical engineering cases.

Experimental investigations and nonlocal computational models of slurry infiltrated fiber concrete with CaCO3 whiskers

Experimental investigations and nonlocal computational models of slurry infiltrated fiber concrete with CaCO3 whiskers

Experimental study and theoretical modeling for the compressive stress-strain relationship of multi-scale hybrid fiber-reinforced SHCC

In order to better match the multi-level structural characteristics and multi-scale fracture process of cementitious composite, multi-scale hybrid fiber-reinforced strain hardening cementitious composite (MsHySHCC) was designed by adding hooked steel fiber and calcium carbonate (CaCO3) whisker into conventional polyvinyl alcohol (PVA) fiber-reinforced SHCC. Compressive properties of PVA-SHCC and MsHySHCC were evaluated experimentally. The results indicate that the designed MsHySHCC had a better compressive performance than that of PVA-SHCC. Moderately partially substituted PVA fibers by steela fiber and CaCO3 whisker enhanced the compressive parameters, however, further substitution of PVA fibers by increasing the content of CaCO3 whisker didn’t bring a higher promotion. Two kinds of semi-theoretical compression constitutive models were developed from the perspective of damage mechanics theory and geometrical mathematical description, respectively. It was found that both of the proposed models can be applied to predict the uniaxial compressive stress-strain relationships of PVA-SHCC and MsHySHCCs.

Reinforcement effects of multi-scale hybrid fiber on flexural and fracture behaviors of ultra-low-weight foamed cement-based composites

In this paper, the flexural behavior and fracture parameters of ultra-low-weight foamed cement-based composites (FCC) reinforced by a novel fiber hybridization containing short PP fiber, and CaCO3 whisker was investigated. The flexural behavior, fracture failure, fracture toughness, and fracture energy of FCC with multi-scale fibers have been comprehensively evaluated. The fiber hybridization performed better fracture performances than that of incorporation of mono PP fiber or CaCO3 whisker, which has provided a grading crack resistance in the ultra-low-weight FCC and achieved the synergistic reinforcing effect. Accordingly, this work is helpful towards the foundation of optimal design for fracture toughness analysis in fiber-reinforced lightweight cement elements.

Synergistic Effect between CaCO3 Whisker and Steel-PVA Fiber Cocktail in Cement-Based Material at Elevated Temperature

A new fiber cocktail reinforced cement–based materials (NFCRCM) with steel, polyvinyl alcohol (PVA) fiber, and calcium carbonate whisker (CCW) was developed to obtain powerful fire resistance in this paper. The flexural properties, synergistic effects, and microscopic mechanism of NFCRCM at elevated temperature were particularly studied. With the introduction of CCW, the degradation of flexural strength and toughness of steel-PVA fiber cocktail reinforced cement–based materials below 800°C was decreased. Below 800°C, the NFCRCM with 1.5% steel fiber +0.5% PVA fiber +3% CCW showed a significant positive hybrid effect in flexural strength and toughness resulting from microscopic crack inhibition and nucleation effect of CCW. When the temperature reached 800°C or above, a negative hybrid effect was generally observed due to thermal decomposition of CCW.

Study on the effect of CaCO3 whiskers on carbonized self-healing cracks of cement paste: Application in CCUS cementing

The cracking damage of the CCUS downhole cement sheath is inevitable. In this study, a high concentration of CO2 reacted with the CaCO3 whiskers to induce CaCO3 deposition so as to improve the self-healing performance of the cement paste cracks. The characterization techniques such as compressive strength meter, μ-CT, X-ray diffractometer (XRD), thermogravimetric analyzer (TG) and environmental scanning electron microscope (ESEM) were used to study the effect of the CaCO3 whiskers on the self-healing performance of cement. The compressive strength growth of the cement pastes with and without the incorporation of the CaCO3 whiskers after carbonation self-healing reaction for 28 days was 1133% and 960%, respectively. The analysis of the crack volume of the cement pastes before and after carbonization by μ-CT revealed that the self-healing rate of the crack volume of the cement paste mixed with the CaCO3 whiskers was 55.24%, which was 18.32% higher than the system without any CaCO3 whiskers. In addition, the XRD and TG analyses demonstrated that the content of Ca(OH)2 in the cracks of the CaCO3 whisker cement decreased on increasing the carbonization time, which indicated that the CaCO3 whisker cement had a high extent of Ca(OH)2 involved in the carbonization reaction. Further, the ESEM results confirmed that the surface of the incorporated CaCO3 whiskers became rough, and the carbonized product (calcite) filled the cracks and pores, thus, making the cement paste cracks self-healing.

Flexural properties of PVA fiber reinforced high ductility cementitious composites containing calcium carbonate whisker

To reduce the cost and improve mechanical properties of PVA fiber reinforced high ductility cementitious composites (PVA-HDCCs), calcium carbonate (CaCO3) whisker (CW) was used to partially substitute PVA fibers, and thus a novel kind of the PVA-HDCC containing the CW was designed (PVA/CW-HDCC). Flexural properties of PVA/CW-HDCCs with the different PVA fiber and CaCO3 whisker contents were investigated. The results indicated that the PVA-HDCC flexural deflection hardening ability decreased with the PVA fiber content reduction. However, partially substituted PVA fibers by CWs improved the flexural strength, ultimate flexural deflection, flexural toughness and flexural deflection hardening behavior of PVA-HDCCs. Technique for Order Performance by Similarity to Ideal Solution (TOPSIS) analysis results indicated that the group with 1.5% PVA + 0.5% CW had a higher cost performance than that of the group with 2% PVA fiber. To further understand the flexural properties of the designed HDCCs, a semi-empirical mathematical model considering the influence of CaCO3 whisker was proposed for predicting the flexural strength and ultimate flexural deflection of PVA/CW-HDCCs. The theoretical calculation results showed that the proposed model can be employed to predict flexural properties of PVA/CW-HDCCs.