Wollastonite Microfibers Research Articles

The effects of synthetic wollastonite microfibers on PVA fiber-reinforced engineered geopolymer composites

In this study, first, synthetic wollastonite microfiber (SWM) with a high aspect ratio (44:1) was produced with a special three-stage production method. Then, fly ash and ground granulated blast furnace slag-based engineered geopolymer composites (FA+GGBFS-based EGCs) were developed. SWM was used in different proportions instead of FA. The compressive strength of EGCs, changed in the range of 88.1-111.1 and 95.1-122.6 MPa at 7 and 28 days, respectively. Additionally, EGCs containing 6% SWM performed the best, considering both ‘‘increasing deformation capacity’’ and ‘‘maintaining the bearing strength by fiber bridging after crack’’, since they acted like a fiber owing to the acicular particle structure of SWM. Moreover, it can be said that the presence of the SWM mineral in the pore system, ensured pore discontinuities in the matrix because of its acicular particle structure. Consequently, the mechanical, durability and dimensional stability properties of EGCs improved with SWM.

Flexural behavior and strength model of UHPC plate with steel macrofibers and wollastonite microfibers

Flexural behavior and strength model of UHPC plate with steel macrofibers and wollastonite microfibers

Influences of hybrid fiber-reinforcement using wollastonite and cellulose nanofibers on strength and microstructure characterization of ultra-high-performance mortar

This paper presents the effect of incorporating wollastonite microfibers and cellulose nanofibers on mechanical properties and microstructure of ultra-high-performance mortar (UHPM). Cellulose nanofibers of 0.005%, 0.015%, and 0.030% are combined with 4.8% wollastonite microfiber by weight of binder, which consists of 10% silica fume and 90% cement. Compressive and flexural strengths of the UHPM specimens are measured at 7 days. The microstructure is characterized in terms of SEM/EDX, XRD, FTIR, and nanoindentation. The results show the effectiveness of the fiber hybridization in enhancing the compressive and flexural strength of ultra-high-performance mortar with the improvement in flexural toughness and fracture energy by as much as 10% than control mortar. Moreover, hybrid fiber-reinforcement based on the microstructural analysis provided more synergic effect and uniform distribution of the fibers, thus developing an efficient micro crack bridging mechanism as well as resulting in enhanced toughening properties and an increased load carrying capacity. Additionally, the combination of wollastonite microfibers and cellulose nanofibers promoted the hydration reaction products and contributed a denser matrix between the fibers and cement matrix, resulting in an increase of the microstructure and interface area between the fibers and cement matrix. Nano indentation analysis also confirmed the increase of UHD C-S-H from 65% to 84% and lower percentage of anhydrous phase in ultra-high-performance matrix after combining wollastonite microfibers and cellulose nanofibers.

Mechanical performances, chloride permeability, and microstructure of wollastonite microfiber reinforced cement-based composite incorporated with zeolite powder

Wollastonite microfiber (WM) with a unique fiber structure and zeolite powder (ZP) with a high pozzolanic effect can improve the performances of cement-based composite owing to the same calcium silicate system. This study aimed to analyze the effects of WM and ZP on the properties of cement-based composite by compressive test, flexural test, shear test, rapid chloride migration (RCM) test, fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), mercury intrusion porosimetery (MIP) and scanning electron microscopy (SEM). Results showed that utilizing WM and ZP was found to be beneficial for improving mechanical performances and impermeability. WM had a more significant effect on enhancing flexural and shear properties, which can be attributed to the fact that the WM as a fibrous structure could provide skeleton support and bridging crack resistance in the matrix, and an addition of 5% WM (by mass) in the matrix could increase the 60-day flexural strength, shear strength and tensile strength by 24%, 13% and 4%. Additionally, ZP had a more significant impact on improving the late compressive strength and chloride permeability because of the particle filling effect and pozzolanic effect. The pozzolanic ingredient (such as active SiO2 and Al2O3) in ZP can take secondary hydration reaction with Ca(OH)2 to produce C–S(A)-H, this can refine the pore size and reduce the porosity, especially for the large pore.

Effect of Wollastonite Microfibers and Waste Tire Rubber on Mechanical Properties of Concrete

The main objective of the present research is to investigate the effect of adding wollastonite microfibers and waste tire rubber on the mechanical properties of concrete. For this purpose, two different series of mixtures were considered. Different percentages (5, 10, 15, and 20 percent) of wollastonite microfibers were added to the ordinary concrete and tested in the first series. Then, in the second series, wollastonite microfibers were added to the specimens in the amount of 20% by the weight of cement, and waste tire rubber was replaced with fine aggregate in different percentages (3, 5, 7, and 10 percent by the weight of fine aggregate), and the specimens were tested again. All the specimens were cured at the two ages of 7 and 28 days, and they were tested for the slump, compressive strength, tensile strength, and flexural strength. The results showed that the addition of 20% wollastonite microfibers to the specimens increased the compressive, flexural, and tensile strengths of the concrete at 28 days of age by 16, 87, and 78%, respectively, compared to the control specimen. The outcomes also demonstrated that replacing fine aggregate with tire rubber in samples containing 20% wollastonite microfibers reduces the strength of the samples. The highest reduction is related to the sample containing 20% of waste tire rubber, which has a reduced compressive strength of about 20% compared to the control sample. Furthermore, the results of this research showed that adding wollastonite microfibers to concrete reduces the concrete slump, while the density of the samples increases with the addition of wollastonite. Moreover, the presence of wollastonite microfibers reduces the porosity of concrete, but there is an increase in the number of pores in concrete samples containing waste tire rubber.

Improving the Creep Resistance of Hardened Cement Paste through the Addition of Wollastonite Microfibers: Evaluation Using the Micro-Indentation Technique

This paper evaluates the creep behavior of wollastonite-microfiber-reinforced hardened cement paste. A parametric study was performed for cementitious mixtures with partial replacement of cement using wollastonite. The samples were subjected to uniaxial compression and microindentation experiments. The compressive strength significantly improved by up to 30% for the mixture containing 10% wollastonite fiber. Microindentation experiments were performed to evaluate the creep response and time-dependent performance of both the control and the wollastonite-fiber-reinforced samples. Approximately 36% increase in creep modulus was observed with 10% wollastonite fiber content. This indicates a significant improvement in creep behavior, which can be attributed to the micro-reinforcing effect of the fibers. No significant impact was observed for time characteristic of creep with the incorporation of wollastonite fibers. Overall, the study establishes a cost-effective, sustainable, and efficient route to enhance the creep behavior of hardened cement paste for a wide range of infrastructural applications.

Characteristic properties of fly ash-based self-compacting geopolymer mortars with synthetic wollastonite microfiber produced from silica and calcite

This study investigated the fresh, physical, and mechanical properties of self-compacting geopolymer mortars (SCGs) with synthetic wollastonite microfiber (SWM). SCGs were designed with Class F fly ash (FA) as a binder by activating it with Na2SiO3 and NaOH solutions. First, SWM was produced in the laboratory. Alkali ratios were determined as 1.5, 2.0, and 2.5, whereas SWM percentages were utilized as 0%, 4%, 8%, and 12% by weight of the binder. After geopolymer mortars were cured at 80 oC and 100 oC for 24 hours, respectively, they were kept at room temperature until testing age. The compressive strength, flexural strength, ultrasonic pulse velocity, dynamic modulus of elasticity, water sorptivity coefficient values, and physical characteristics of SCGs were tested at the end of the 28th day. The highest compressive strength value was obtained as 28.9 MPa for SCG-1.5-8 cured at 100 oC, while 6.5 MPa was measured as the highest flexural strength for SCG-2-12 cured at 80 oC.

Life cycle assessment and shrinkage properties of high performance mortars incorporating synthetic wollastonite microfibers

In this study, the use of an alternative material as supplementary cementitious material was researched for the design of high-performance mortars (HPMs). Synthetic wollastonite microfibres (SWMs) were produced from calcite and quartz sand. The SWMs were then replaced at ratios of 0, 3, 6, 9 and 12% by cement weight to investigate the fresh, mechanical and shrinkage properties of HPMs. Test results showed that the mechanical and shrinkage properties of HPMs improved up to 9% inclusion of SWMs. The compressive strength, flexural strength, modulus of elasticity, fracture toughness and fracture energy of HPM incorporating 9% SWM was higher than that of the control mixture by 8.8–9.1%, 7.5–9.9%, 4.7–6.7%, 8.9–4.6% and 13.2–2.5% at 28–90 days, respectively. Similarly, the ratios for maximum drying shrinkage and average crack width were determined as 10.5% and 58.3%, respectively, at the end of 60 days. These findings were also supported by microstructural analysis. Moreover, the potential environmental impacts resulting from the production of 1 kg SWM and HPM incorporating 9% SWM were evaluated using the life cycle analysis software (LCA) SimaPro 8.5.0.0. Based on the LCA results, SWMs can be used as an alternative material to develop sustainable concrete structures.

Properties of ultra-high-performance mortar containing eco-friendly wollastonite micro-fibers for green and sustainable infrastructure

Wollastonite has become one of the potential pozzolanic microfibers material that can be used to improve the characteristics of cement-matrix composites. This study was conducted with the aim to investigate experimentally the properties of high-strength mortar containing wollastonite as an additive material with percentage of 1.2, 2.4, 4.8, and 9.6% by weight of binders. Water and sand to binder ratio of 0.2 and 2.5, respectively, were used to form high-strength mortar specimens for mechanical properties testing including compressive strength and three-point loading on flexural strength test. Microstructural analysis was also conducted to assess the reinforcing effects and hydration products that might be affected due to the inclusion of wollastonite micro-fibers. The results show that mortar with 1.2-4.8% of wollastonite content reached 12% higher resistance on compression load with respect to the control mortar. More significant improvement can be observed in flexural strength results whereas the wollastonite showed its reinforcing capability in bridging the micro-cracks resulted in more ductile and toughness matrix in carrying the high load carrying capacity. Moreover, wollastonite also has a capability to pore refinement as evident from the sorptivity results. Furthermore, wollastonite micro-fibers can be an alternate source material for durability improver that leads to sustainable infrastructure.

Effect of wollastonite microfiber on the performance of engineered cementitious composites

The effects of 75μm wollastonite microfibers on the workability, mechanical properties and shrinkage properties of cementitious composites were studied by mechanical and shrinkage tests. The results show that the addition of microfiber reduces the fluidity of fresh mixture, but appropriate content can still meet the needs of self-compaction. WF has no gain effect on the compressive strength of the mixture, but when the dosage is 20%~30%, the flexural strength and tensile strength can be significantly increased by 87% and 28%. The shrinkage test indicates that WF has a good inhibiting effect on shrinkage deformation. It can be used as a good mineral admixture in ECC.

Properties of additively manufactured geopolymer incorporating mineral wollastonite microfibers

Integration of reinforcement in the 3D concrete printing (3DCP) process is a major challenge. As a possible solution, the addition of short synthetic/metallic fibers directly to a fresh mixture before extrusion has been investigated in previous studies. However, the use of natural/inorganic microfibers such as wollastonite as reinforcement for 3DCP has received less attention. Wollastonite is substantially cheaper and more environmentally friendly than synthetic/metallic fibers. To fill this knowledge gap, this study reports a systematic approach to enhance the flexural strength of a 3D-printed geopolymer by the addition of wollastonite microfiber. The effect of different replacement levels of wollastonite (0, 5, 10, 15, 20, and 30% by weight of sand) on setting time and mechanical properties of several mixtures were evaluated to identify the optimum wollastonite content. The printing performances, rheological properties, and mechanical strengths of the optimum mixture were then evaluated and compared with the control mixture (without wollastonite). The results showed that at 10% replacement level, the static yield stress and thixotropy property of the mixture were enhanced, which is desirable for the superior printability of the mixture. In addition, the flexural strength of the mixture incorporating 10% wollastonite was superior to the control mixture, whereas the compressive strength was not changed. The use of mineral wollastonite microfibers as a low-cost and environmentally friendly reinforcement for 3DCP is experimentally established in this study.

The flexural behaviors and mechanism of wollastonite microfiber modified ultra-high performance concrete with steel fiber from micro to macro scale

The flexural behaviors and mechanism of wollastonite microfiber modified ultra-high performance concrete with steel fiber from micro to macro scale

Rheological properties, strength characteristics and flexural performances of engineered cementitious composites incorporating synthetic wollastonite microfibers with two different high aspect ratios

In this study, synthetic wollastonite microfiber (SWM) with high aspect ratio (44:1/SWM-I) developed with a special technique was used in different proportions instead of cement (C), fly ash (FA) and cement + FA (C-FA) in Engineered Cementitious Composites (ECC). SWM-I decreased the workability as a result of interlocking during flow due to its acicular particle structure. When SWM-I was used instead of C, it was determined that the compressive strength decreased and the ductility improved significantly due to the increased SWM-I content. The use of SWM-I instead of FA improved the mechanical performance up to 6% in terms of compressive strength and flexural performance. However, the mixtures prepared by using SWM-I instead of C-FA provided optimum data, considering both ''increasing deformation capacity'' and ''maintaining the bearing strength by fiber bridging after crack''. Therefore, the effect of SWM-II (30:1) was tested by using instead of C-FA. SWM-I with a higher aspect ratio has been improved the mechanical properties of ECC and reduced the workability of ECC more than that of SWM-II. Increasing FA content in ECC has been provided higher ductility but decreased significantly the compressive strength. The bearing strength and deformation capacity of the ECC designed with finer aggregate has been achieved the higher levels compared to larger aggregate size. As a result of all obtained findings, the data of the optimum mixture has been determined as follows: the compressive strength, flexural strength and ductility of ECC incorporating 6% SWM-I instead of C-FA have been reached higher levels than that of 19.0%-12.5%, 12.0%-8.2% and 56.2%-25.5% at 7–28 days, respectively.

Finite Element-Based Numerical Simulations to Evaluate the Influence of Wollastonite Microfibers on the Dynamic Compressive Behavior of Cementitious Composites.

This paper investigates the dynamic compressive behavior of wollastonite fiber-reinforced cementitious mortars using multiscale numerical simulations. The rate dependent behavior of the multiphase heterogeneous systems is captured in a multiscale framework that implements continuum damage towards effective property prediction. The influence of wollastonite fiber content (% by mass) as cement replacement on the dynamic compressive strength and energy absorption capacity is thereafter elucidated. An average compressive strength gain of 40% is obtained for mortars with 10% wollastonite fiber content as cement replacement, as compared to the control mortar at a strain rate of 200/s. The rate dependent constitutive responses enable the computation of energy absorption, which serves as a comparative measure for elucidating the material resistance to impact loads. Approximately a 45% increase in the dynamic energy absorption capacity is observed for the mixture containing 10% wollastonite fibers, as compared to the control case. Overall, the study establishes wollastonite fibers as a sustainable and dynamic performance-enhanced alternative for partial cement replacement. Moreover, the multiscale numerical simulation approach for performance prediction can provide an efficient means for the materials designers and engineers to optimize the size and dosage of wollastonite fibers for desired mechanical performance under dynamic loading conditions.

Shrinkage Mitigation of an Ultra-High Performance Concrete Submitted to Various Mixing and Curing Conditions.

Ultra-High Performance Concretes (UHPC) are cement-based materials with a very low water-to-binder ratio that present a very-high compressive strength, high tensile strength and ductility as well as excellent durability, making them very interesting for various civil engineering applications. However, one drawback of UHPC is their pretty high autogenous shrinkage stemming from their very low water-to-binder ratio. There are several options to reduce UHPC shrinkage, such as the use of fibers (steel fibers, polypropylene fibers, wollastonite microfibers), shrinkage-reducing admixtures (SRA), expansive admixtures (EA), saturated lightweight aggregates (SLWA) and superabsorbent polymers (SAP). Other factors related to curing conditions, such as humidity and temperature, also affect the shrinkage of UHPC. The aim of this paper is to investigate the impact of various SRA, different mixing and curing conditions (low to moderate mixing temperatures, moderate to high relative humidity and water immersion) as well as different curing starting times and durations on the shrinkage of UHPC. The major importance of the initial mixing and curing conditions has been clearly demonstrated. It was shown that the shrinkage of the UHPC was reduced by more than 20% at early-age and long-term when the fresh UHPC temperature was closer to 20 °C. In addition, curing by water immersion led to drastic reductions in shrinkage of up to 65% and 30% at early-age and long-term, respectively, in comparison to a 20% reduction for fog curing at early-age. Finally, utilization of a liquid polyol-based SRA allowed for reductions of 69% and 63% of early-age and long-term shrinkages, respectively, while a powder polyol-based SRA provided a decrease of 47% and 35%, respectively.

Design of Wear-Resistant UHMWPE-Based Composites Loaded with Wollastonite Microfibers Treated with Various Silane Coupling Agents

The tribomechanical properties of the wear-resistant ultrahigh molecular weight polyethylene (UHMWPE)-based composites loaded with wollastonite microfibres silanized with various coupling agents (“KH-550”, “Penta-1006”, and “OTS”) were investigated. It was demonstrated that the mechanical properties of UHMWPE-based composites filled with various amounts of wollastonite (7–23 wt. %) increased by 1.3 times (yield strength) and by 1.8 times (elastic modulus), while the wollastonite silanization further improved yield strength by 9% in some cases. It was demonstrated that the composite loaded with 23 wt. % wollastonite silanized with the “KH-550” coupling agent possessed the maximum wear resistance under “moderate” conditions of tribological loading. Under “severe” conditions, the composites containing 23 wt. % wollastonite silanized with the less efficient “OTS” and “Penta-1006” agents showed the greatest wear resistance during dry sliding friction. Wear resistance significantly depended on filler weight fraction and the load–speed mode of the tribological tests. Based on the obtained experimental data on the mechanical (including impact toughness) and tribological properties of the UHMWPE-based composites loaded with wollastonite, the optimal compositions (the filler content and the type of the coupling agent) for two load–speed modes were designed using the developed computer algorithm. The composites provided the predefined high tribomechanical properties for operation in the metal-polymer friction units compared to neat polymer.

Effects of rice husk ash and wollastonite incorporation on the physical and thermal properties of refractory ceramic composites

ABSTRACT The main objective of this work was to evaluate the effects of rice husk ash and wollastonite microfibers incorporation, added per clay partial substituition, on physical and thermal properties of refractory ceramic composites. The raw materials characterization occurred with respect to their chemical composition (XRF), phase composition (XRD) and granulometry by laser. The composites were avaluated by physical properties - apparent porosity, bulk density, water absorption, linear retraction after sinterization and mass variation - and thermal properties - thermal conductivity and thermal shock. The rice husk ash used in the present work proved to have potential as a ceramic precursor in the development of refractories. The clay substitution per ash and the microfiber different percentages resulted in an increase in water absorption and apparent porosity and a reduction in the linear retraction. The increase in porosity suggests that the mullitization was insufficient. Regarding the thermal performance, the thermal conductivity was inversely proportional to the porosity and the microfiber percentage. In addition, the higher the thermal-shock temperature gradient the lower was the number of cycles resisted by the composites.

Properties of SCC containing pozzolans, Wollastonite micro fiber, and recycled aggregates

Self compacting concretes (SCC) containing higher volumes of pozzolanic materials possess compressive strengths up to 30MPa. Fibers like steel, polypropylene, and carbon fibers are added in small volumes ranging from 0.25-2% v/v of concrete to increase the strength (>40MPa) of such concretes as higher volumes of fiber cause balling effect on account of inhomogeneity, thereby reducing the strength and workability. Hence higher volume of cement substitution either with mineral admixtures or fibers, or with both, to increase strength and workability is limited in the case of SCC. The condition worsens further if recycled aggregates replace normal aggregates. Wollastonite micro fiber (WMF) is a promising material that could be used in higher contents but its interaction with recycled aggregates to affect workability and strength has not been studied. Therefore this study tries to obtain a high strength concrete (>M40) by use of WMF along with flyash @ 5%, maximally up to 10% each. Microsilica was added @ 2.5%, maximally up to 10% to improve the interphase strength and make the concrete homogeneous. Results indicated that in order to obtain a high strength mix for such composites, higher amounts of WMF (≥10% by weight of binder) such that WMF:flyash varies from 1:1 to 2:1 is required, along with microsilica contents ≥7.5%. Literature suggests 5% microsilica along with either 20% WMF or 10% flyash, for yielding high strength SCC without recycled aggregates. Hence use of nearly equal amounts of WMF, flyash, and microsilica such that nearly 30% of cement is substituted, is recommended.

Behavioral study of self-compacting concrete with wollastonite microfiber as part replacement of sand for pavement quality concrete (PQC)

The fact that self-compacting concrete (SCC) does not require any supplementary compaction to fill in every nook and corner of the structure without compromising with strength and durability makes it much more futuristic and desirable over conventional concrete. Present study highlights the behavioural changes in SCC for PQC applications at macro and micro levels with the incorporations of wollastonite micro-fiber; proposed to be used for restoration of deteriorated pavement quality concrete slab. Wollastonite micro-fiber was incorporated as part replacement of fine aggregates in proportions of 10–50% with an offset of 10%. Different properties of SCC mixes such as flow-ability, segregation resistance and filling ability were investigated in fresh state while mechanical properties including compressive strength, flexural strength and hardened density were studied in hardened states. The SCC mixes were also investigated for estimating effect of incorporating wollastonite micro-fiber in hydrated states of cement mortar. Inclusions of wollastonite micro-fiber in SCC enhanced the cohesiveness of the mix thereby improving the density and reducing its water absorption. SCC mixes with wollastonite micro-fiber showed higher flexural and comparable compressive strength parameters than those of conventional SCC mix. SCC mix with 30% wollastonite micro-fiber as a replacement of fine aggregates provides similar strength and better repair prospects as compared to conventional SCC or normal concrete mix.

Solid-Lubricant, Polymer – Polymeric and Functionalized Fiber– and Powder Reinforced Composites of Ultra-High Molecular Weight Polyethylene

Mechanical and tribotechnical characteristics of solid-lubricant and polymer-polymeric composites of UHMWPE were studied for the sake of design extrudable, wear-resistant, self-lubricant polymer mixtures for Additive Manufacturing (AM). Tribotechnical properties of UHMWPE blends with the optimized content of solid lubricant fillers (polytetrafluoroethylene, calcium stearate, molybdenum disulphide, colloidal graphite, boron nitride) were studied under dry sliding friction at different velocities (V = 0.3 and 0.5 m/s) and loads (P = 60 and 140 N). Also, in order to increase strength and wear-resistance of UHMWPE composites they were reinforced with wollastonite microfibers and aluminum metahydroxide AlO (OH) microparticles preliminary treated (functionalized) in polyorganosiloxane. The comparison on measured mechanical and tribotechnical properties are given with interpretation of the mechanisms of observed phenomenon.