CaCO3 Whisker Research Articles

Rheological and mechanical properties of hybrid fiber reinforced cement mortar

A new hybrid fiber system containing steel fiber, polyvinyl alcohol fiber (PVA fiber) and calcium carbonate (CaCO3) whisker was employed to further improve hardened properties and reduce engineering cost of cement mortar. In this paper, the rheological properties, flow rate and flow spread were measured to evaluate the workability of hybrid fiber reinforced mortar in fresh state. Mechanical strength and flexural toughness of mortars were tested in hardened state. The results indicated that, flowability of fresh hybrid fiber reinforced mortar decreased after substituting PVA fiber for steel fiber and further CaCO3 whisker for PVA fiber in mortar. This is mainly due to the flexibility of PVA fiber and large specific surface area of CaCO3 whisker. The hybrid fiber reinforced mortar shows promising mechanical strength and flexural toughness due to the multi-scale crack resistance formed by micro- and macro-fibers. M5 specimen (1.5% steel fiber+0.4%PVA fiber+1.0% CaCO3 whisker) exerts the best flexural performance and relatively higher compressive strength, exhibiting an obviously positive hybrid effect of fibers.

Development of Multiscale Fiber-Reinforced Engineered Cementitious Composites with PVA Fiber and CaCO3 Whisker

AbstractEngineered cementitious composites (ECCs) have attracted increasing attention in recent years owing to its unique properties of tensile strain hardening behavior and tight multiple cracks. ...

CaCO3 whisker modified Engineered Cementitious Composite with local ingredients

This paper aims at developing CaCO3 whisker modified ECC with local ingredients in China. CaCO3 whisker is a kind of micro scale fibrous material (inorganic single crystal) with a diameter of 0.5–2μm and an aspect ratio of 20–60. It has a high tensile strength of 3–6GPa and high elastic modulus of 410–710GPa. Therefore, CaCO3 whisker can potentially reinforce the ECC materials at microscopic level. In this study, cube compressive and uniaxial tensile tests were conducted to investigate the influence of CaCO3 whisker on ECC’s mechanical properties. The experimental results indicated that incorporating CaCO3 whisker can improve compressive strength and tensile strain-hardening behavior (especially tensile strain capacity). When CaCO3 whisker was added at the optimal content of 0.5% by volume of total ECC mixture, the compressive strength of composite increased from 23MPa to 30MPa, and the ultimate tensile strength and tensile strain capacity increased by 53% and 114%, respectively. Addition of CaCO3 whisker can also enhance the robustness of ECC mixtures. The coefficient of variation of mechanical properties was found to be reduced by 90% compared to that of the ECC without CaCO3 whisker. In addition, when CaCO3 whisker is added, fly ash content has negligible influence on ultimate tensile strength of the composite, which suggests that the frictional bond strength of fiber/matrix interface is significantly affected by CaCO3 whisker.

Mechanical Attributes of Uniaxial Compression for Calcium Carbonate Whisker Reinforced Oil Well Cement Pastes

It is crucial for design and safety of the cementing sheath to develop better understanding of the CaCO3 whisker reinforced oil well cement pastes. The uniaxial compression curve, mechanical constitutive relation, and reinforcing mechanism of the CaCO3 whisker reinforced oil well cement pastes are studied in this script. The results indicate that the CaCO3 whisker under the 10% dosage could improve the tensile strength of the cement paste significantly. The peak stress, elasticity modulus, and the energy at different stages of the stress-strain curve of the CaCO3 whisker reinforced cement paste are reinforced with the increasing of CaCO3 whisker. Afterward, the constitutive model of stress-strain curve, the toughness index, and capability coefficients index of the CaCO3 whisker reinforced cement paste are established. A physical model of the interface layer is also established and the micromechanical reinforcement is related to the double film layer between the CaCO3 whisker and cement matrix which could be bonded with much more fastness to the cement surface. The development of this script provides new ways to analyze the toughening mechanism of CaCO3 whisker and establishes a correlation between basic material structure and the physical properties.

New strategy for design and fabrication of polymer hydrogel with tunable porosity as artificial corneal skirt

In order to obtain an ideal material using for artificial corneal skirt, a porous polymer hydrogel containing 2-hydroxyethyl methacrylate (HEMA), trimethylolpropane triacrylate (TMPTA) and butyl acrylate was prepared through one-step radical polymerization method and the usage of CaCO3 whisker as porogen. The physical-chemical properties of the fabricated polymer hydrogel can be adjusted by CaCO3 whisker content, such as pore size, porosity, water content of materials and surface topography. Then a series of cell biology experiments of human corneal fibroblasts (HCFs) were carried out to evaluate its properties as an artificial corneal skirt, such as the adhesion of cells on the materials with different pore size and porosity, the apoptosis on materials with different characteristics, the distribution of the cells on the material surface. The results revealed that high porosity not only could improve water content of hydrogel, but also strengthen the adhesion of HCFs on hydrogel. In addition, high porosity hydrogel with the whisker shape of pores showed much elongate spindle-like morphology than those low porosity hydrogels. MTT assay certified that the resulted polymer hydrogel material possessed excellent biocompatibility and was suitable for HCFs growing, making it promising for being developed as artificial corneal skirt.

Rheology, fiber distribution and mechanical properties of calcium carbonate (CaCO3) whisker reinforced cement mortar

Calcium carbonate (CaCO3) whiskers are a new kind of microfiber used in cementitious composites and have proved to provide excellent effect on strengthening and toughening. In order to further improve the mechanical properties of CaCO3 whisker-reinforced cementitious composites, rheological properties of fresh mixtures and the CaCO3 whisker distribution in the hardened matrix were investigated. The yield stress and plastic viscosity increased with an increasing content of CaCO3 whisker and a decreasing water-cement ratio. Also, the rheological properties were affected by the distribution of CaCO3 whisker in the matrix. The largest increments in flexural and compressive strength were 27.59% and 12.60% for the mortars with CaCO3 whisker contents of 2.0% and 1.5%, respectively. The properties responsible for the mechanical response were explained in terms of the effects of CaCO3 whisker reinforcement, the distribution of CaCO3 whiskers, and the porosity as well as pore size distribution.

Preparation of PMMA grafted calcium carbonate whiskers and its reinforcement effect in PVC

In this study, calcium carbonate (CaCO3) whiskers were grafted with poly(methyl methacrylate) (PMMA) by in situ emulsion polymerization using γ‐methacryloxy propyl trimethoxyl silane (γ‐MPS) as a coupling agent, and the properties of resultant whisker were determined using Fourier transform infrared (FTIR) spectroscopy, energy dispersive spectroscopy (EDS), X‐ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The results show that PMMA has been successfully grafted onto the surface of CaCO3 whiskers and the maximum grafting degree (Gd) is 3.75%. The scanning electron microscopy (SEM) micrographs of the tensile‐fractured surfaces show that modified CaCO3 whiskers have strong interfacial adhesion to the poly(vinyl chloride) (PVC) matrix. The tensile strength increases from 44.0 MPa for PVC composite with unmodified whisker to 49.5 MPa for that with grafted whisker. The dynamic mechanical analysis (DMA) and TGA results indicate that the composites reinforced by modified CaCO3 whiskers have much higher modulus, glass transition temperature, and better thermal stability than their counterparts reinforced by unmodified CaCO3 whiskers. POLYM. COMPOS., 38:2753–2761, 2017. © 2015 Society of Plastics Engineers

Growth of Aragonite CaCO3 Whiskers in a Microreactor with Calcium Dodecyl Benzenesulfonate as a Control Agent

This study presents a novel technique for the controllable preparation of aragonite CaCO3 whiskers using a microdispersion process. Calcium dodecyl benzenesulfonate [Ca(Ar–SO3)2] was first used as an additive for controlling the crystalline form. A homogeneous concentration distribution in the system was achieved due to the efficient micromixing. The effects of various operation parameters on the whiskers were determined, and the reaction conditions were optimized. The mechanism of the additive was discussed. The dynamic adsorption of Ca(Ar–SO3)2 on the surface of whiskers was experimentally demonstrated to be in charge of maintaining the one-dimensional growth and the high purity of the crystals. Aragonite CaCO3 with a crystalline purity of 98–99.5% was controllably synthesized at room temperature. The whiskers were approximately 27 μm in length and had an aspect ratio of about 58.

Effect of calcium carbonate whisker content on the morphology, crystallization, and mechanical properties of poly(para-dioxanone)/Calcium carbonate whisker composites

In this work, poly(para-dioxanone) (PPDO) was mixed with 0, 1, 5, 10, 20, and 30 weight percent (wt%) calcium carbonate (CaCO3) whiskers by solution coprecipitation. Samples were compression molded into bars using a platen vulcanizing press. It has assessed the influence of the CaCO3 whisker content on the morphology, thermal, mechanical, and crystalline properties of the PPDO/CaCO3 whisker composites, using differential scanning calorimetry (DSC), polarized optical microscopy, scanning electron microscopy, and X-ray diffraction. DSC showed that the glass transition temperature (Tg) and crystallization temperature (Tc) of the composites increased with increasing CaCO3 whisker content. At low CaCO3 whisker content (1 wt%), the degree of crystallinity (Dc) of PPDO increased sharply. The addition of higher content of CaCO3 whisker would cause more agglomeration in PPDO matrix, so that the mechanical properties of PPDO/CaCO3 whisker composites would gradually decrease. The mechanical properties of PPDO were changed by the presence of CaCO3 whiskers; the optimal amount of CaCO3 whisker was 1 wt%, which sharply improved the tensile strength of PPDO by 54%. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Hybrid effect of calcium carbonate whisker and carbon fiber on the mechanical properties and microstructure of oil well cement

Individual carbon fibers, calcium carbonate (CaCO3) whiskers and their hybrid combination were used to reinforce the oil well cement, and the reinforced cement was analyzed by means of scanning electron microscopy (SEM) and mechanical testing. Compared with individual CaCO3 whiskers or carbon fibers, the hybrid combination of 10% CaCO3 whiskers and 0.3% carbon fibers can more effectively improve the strength and toughness. This is likely attributed to the carbon fibers pulling out from the cement matrix, better stress transfer in the presence of CaCO3 whiskers, finer dispersion of CaCO3 whiskers and good miscibility of CaCO3 whiskers with cement phases.

Characterization of mechanical behavior and mechanism of calcium carbonate whisker-reinforced cement mortar

In order to reinforce cement mortar, a new kind of micro-fibrous material, calcium carbonate whisker (CaCO3 whisker), was incorporated in this study. Microstructure, mechanical properties and reinforcing mechanism of this composite were characterized. It was found that the addition of CaCO3 whisker improved not only the compressive and flexural strength of cement mortar, but also the load–deflection curves and work of fracture. Further work using mercury intrusion porosimetry tests confirmed the filler effect and the refining of the pore distribution of whiskers in cement mortar. Scanning electron microscopy showed that the microscopic mechanism primarily consists of whisker pullout, crack deflection, whisker-cement coalition pullout, whisker bridging and whisker breakage. These mechanisms are related to the matrix strength. As compared to the strong matrix, the weak matrix that was modified with CaCO3 whisker achieved the highest increase in strength and toughness of the cement mortar. This is likely attributed to the crack deflection mechanism, which is weakened by the strong interfacial bonding between the CaCO3 whisker and cement matrix in the stronger mortar matrix.

Mechanical response and shrinkage performance of cementitious composites with a new fiber hybridization

A new kind of fiber hybridization containing steel fibers, polyvinyl alcohol (PVA) fibers and cheap calcium carbonate (CaCO3) whiskers (approximately $230 per ton) was designed to improve the mechanical response and shrinkage performance as well as reduce the production cost of fiber reinforced cementitious composites. Compressive response, flexural response, drying shrinkage and plastic shrinkage of this designed hybrid fiber reinforced composites were presented. The results indicated that the designed hybrid fiber shows a significant positive hybrid effect on mechanical response and plastic shrinkage of cementitious composites. Steel fibers are more effective in restricting drying shrinkage. PVA fibers and CaCO3 whiskers are more effective in restraining plastic shrinkage. Good mechanical response and satisfactory shrinkage performance of the designed hybrid fiber reinforced cementitious composites make it possible to partly replace the steel fibers and PVA fibers by using CaCO3 whisker, thus helping to decrease the production cost of fiber reinforced cementitious composites for large scale construction project applications in the future.

Fiber synergy in multi-scale fiber-reinforced cementitious composites

A multi-scale fiber blend containing steel fibers, polyvinyl alcohol fibers and calcium carbonate (CaCO3) whiskers was designed to increase the multi-scale cracking resistance for cementitious composites. This multi-scale fiber-reinforced composite was tested for fiber synergy in compressive behavior and flexural performance. The results indicated that the multi-scale fiber improves not only the softening branch of the compressive stress–strain curve and the strain capacity at ultimate stress but also the compressive toughness, achieving a ductile fracture mode during compression. The flexural strength and toughness are significantly enhanced, which is also reflected in the deflection hardening behavior and multiple cracking performance. This suggests that there is an obvious positive fiber synergy in multi-scale fiber-reinforced cementitious composites and the multi-scale fiber can effectively interact with the multi-scale cracking process of cementitious composites. Moreover, it seems possible that steel fibers and polyvinyl alcohol fibers can be partly replaced with CaCO3 whiskers, thus the production cost of fiber-reinforced cement-based composites can be decreased.

Effect of particle size and surface modification on mechanical properties of poly(para‐dioxanone)/inorganic particles

AbstractPoly(para‐dioxanone) (PPDO)‐based composites have been prepared by blending PPDO with three different types of CaCO3 particles, CC1 (nano‐CaCO3), CC2 (CaCO3 whisker), and CC3 (silane‐coated CaCO3 whisker). The effects of particles size, interface adhesion, and crystallinity of composites on mechanical properties were discovered through analysis of the morphology of fracture surfaces, thermal characteristics, and crystalline structure. DSC revealed that the CaCO3 particles acted as a nucleating agent and promoted crystallinity of PPDO. The effect of CaCO3 particles on crystallization of PPDO was clearly revealed by using the nucleating efficiency. Smaller size particles exhibit greater nucleating efficiency. Adhesion between PPDO and the CaCO3 particles plays major roles on the mechanical properties of composites. The tensile strength of PPDO was improved over 54%. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

Dispersion, Microstructure and Mechanical Properties of Ground Calcium Carbonate Whisker-Reinforced Portland Cement

Mechanical grinding method was employed in this study to disperse CaCO3 whiskers in cement matrix. Mechanical properties of the ground whisker reinforced cement were measured. It is shown that the mechanical grinding method was advantageous to the dispersion and mechanical properties of composites. But the grinding process must be proper to assure a certain length and integrality of the whiskers. Crack deflection and whisker pullout mechanisms could account for the strengthening and toughening effects caused by whiskers.

Thermal Behavior, Mechanical Properties and Microstructure of Polypropylene Composites Filled by Calcium Carbonate Whiskers

CaCO3 whiskers were treated by stearic acid and the surface property of the treated whisker were evaluated by activation index. When the mass fraction of stearic acid was 4.0%, activation exponential increased to 80.0% almost from zero. The composites were prepared by blending with polypropylene and the treated whiskers. The performance of the composites, such as thermal behavior, mechanical properties and microstructure, were analyzed with differential scanning calorimetry, scanning electron microscopy and tensile testing. The results showed that CaCO3 whisker played heterogeneous nucleation to induce crystalline behavior of PP phase in the blends and the crystallization rate of PP phase also increased because of CaCO3 whiskers intervening. Moreover thermo-decomposing temperature and tensile strengths of the blends all increased with increasing whisker content, except a little less than that of pure PP as filling 3.22% CaCO3 whiskers, but the elongation at break increased with increasing whisker content.

Polypropylene hybrid composites with wood flour and needle-like minerals

Polypropylene (PP) hybrid composites filled with wood flour and needle-like minerals, including SiO2 whiskers, CaCO3 whiskers and milled glass fibres, were prepared by melt blending and injection moulding. Maleic anhydride grafted PP was used as a compatibiliser. The effect of the needle-like minerals’ type and content on the crystallisation and melting behaviour, morphology, mechanical properties, moisture resistance and thermal stability of the hybrid composites were studied. The results showed that SiO2 and CaCO3 whiskers exhibited strong heterogeneous nucleation and promotion effect on PP crystallisation. Milled glass fibre was superior to enhance the tensile, flexural and impact properties of hybrid composites. Maleic anhydride grafted PP was selective for the interfacial modification of hybrid fillers and the best modification effect achieved in the composites hybridised with milled glass fibre. Comparatively speaking, the optimal proportions between the three kinds of needle-like minerals and the wood flour for the hybrid modification of PP all lie in 1·5∶48·5.

Performance of Polypropylene Composites Filled by Calcium Carbonate Whiskers

Calcium carbonate (CaCO3) whiskers were firstly treated by sodium stearate, and then blended with polypropylene (PP) to prepare the composites by a closely intermeshing co-rotating twin-screw extruder at 200°C. The performance of the composites, such as thermal behavior, microstructure and mechanical properties, were analyzed with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and mechanical testing. The results showed that CaCO3 whisker influenced the crystalline behavior of PP phase in the blends because of its intervening. Moreover, thermo-decomposing temperature, tensile and bending strengths of the blends all increased with increasing whisker content. CaCO3 whiskers had good reinforcing and toughening effects on PP.

Microstructure and mechanical properties of CaCO3 whisker-reinforced cement

Composite Portland cement (PC) played an important role in various kinds of construction engineering owing to low hydration heat, low-cost, and application of solid industrial waste, but its brittleness and low strength limited its use in stress-bearing locations. The aim of this study is to improve the toughness and fracture resistance by incorporating CaCO3 whisker in cement matrix. Effect of different content of calcium carbonate whiskers on the mechanical properties of PC was investigated. The results showed that the flexural strength, impact strength and split tensile strength were increased by 39.7%, 39.25% and 36.34% at maximum, respectively. Microstructure and elements of the whiskers in hardened cement were observed and analyzed by SEM/EDS. The mechanisms of the reinforcement of CaCO3 whisker on cement were also discussed, and the conclusion was that the improvement could be correlated to energy-dissipating processes owing to crack bridging, crack deflection, and whisker pull-out at the crack tips.

Experimental Study on Impact Resistance of CaCO<sub>3</sub> Whisker-Reinforced Cement Mortar

CaCO3 whiskers were incorporated into the cement mortar in this study and the effects of whiskers on the impact resistance of mortar were investigated. The results showed that CaCO3 whiskers could improve the impact resistance of cement mortar before initial cracking. When the whisker content was 10%, the reinforcing effect was optimal. But after initial cracking, the capacity of matrix to resist further impact load was not improved significantly. By observing the failure modes of specimens, it was shown that the crack branches of whisker-reinforced cement mortar were increased, which indicated the brittleness of matrix was decreased and the toughness was improved to some extent. In addition, the reinforcing mechanisms of CaCO3 whiskers in the cement mortar were also discussed