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Calcium carbonate is wildly used in cementitious composites at different scales and can affect the properties of cementitious composites through physical effects (such as the filler effect, dilution effect and nucleation effect) and chemical effects. The effects of macro (>1 mm)-, micro (1 μm–1 mm)- and nano (

Fiber reinforced cementitious composites (FRCC) have been widely used in the field of civil engineering in terms of high-performance building material. The fracture mechanics has been generally considered as an effective way to perform the stability analyses of cracks and safety assessment of concrete structures. This review article first introduces several theoretical models of fracture mechanics and different testing methods of fracture parameters for FRCC. Then the factors affecting fracture properties of FRCC are reviewed respectively, including fiber type, fiber content (Vf), water-to-cement ratio (w/c), maximum aggregate particle size (dmax), aggregate type, initial crack length (a0), high temperature and freeze–thaw cycle times. Furthermore, the reinforcement mechanism of fiber to improve fracture properties of FRCC is discussed, and future work is recommended. This review provides fundamentals on measuring fracture properties, also is to understand the fracture behaviors of FRCC.

Calcium carbonate whisker (CW) can work as a cost-effective and environment friendly micro-fiber in reinforcing cementitious composites. Influence of high temperature on micro-structure of CW reinforced cement paste by nanoindentation and mercury intrusion porosimetry test is studied in this research. Up to 500[Formula: see text]C, the indentation depth, elasticity modulus, indentation hardness and interfacial transition zone (ITZ) width of CW reinforced cement paste are near or even better than that at room temperature, due to the coupling effect of CW transformation from aragonite to calcite and internal autoclaving. However, when the temperature is higher than 700[Formula: see text]C, nano-mechanical properties of CW reinforced cement paste degenerated significantly, due to the decomposition of CW and hydration products. Similarly, with the increase of temperature up to 400[Formula: see text]C, the porosity and pore size increase little or even decrease, while the fractal dimension of pore volume increases. With the introduction of CW, the pore parameters and fractal dimension are decreased up to 400[Formula: see text]C, due to the filler effect of CW. When the temperature is higher than 700[Formula: see text]C, the pore diameter and fractal dimension of CW reinforced cement paste are significant higher than that of pure cement paste, due to the decomposition of CW and hydration products. In CW reinforced cement paste, the fractal dimension was increased with the increased temperature and porosity in this research. There are negative correlations between the pore volume fractal dimensions and the strengths of CW reinforced cement paste. Fractal dimension is a useful tool to evaluate the change of pore structure at high temperature.

A testing program was undertaken to evaluate the effects of fibers on properties of expansive self-consolidating concrete (ESCC). Hooked end steel fibers and monofilament polypropylene fibers were used in the tests with three selected volume fractions (0.25%, 0.50% and 0.75% of the total volume of concrete) for steel fibers and one volume fraction (0.10%) for polypropylene fibers. Workability of fresh concrete, mechanical properties and shrinkage of hardened concrete were investigated. Slump flow, J-ring and V funnel tests were carried out to evaluate the filling ability, passing ability, and viscosity of the fresh concrete. Mechanical properties including compressive strength, splitting tensile strength and flexural strength of hardened concrete were studied. Test results indicate that workability of fresh concrete decreases with increased volume fraction of fibers. The compressive strength of ESCC is improved at 7 days with added expansive admixture. Combined addition of expansive admixture and fibers reduces the concrete strength at 7 days, while it does not influence the 28 days strength noticeably. For flexural performance, steel fiber improves the linear load-deflection relationship of ESCC beams. Steel fiber reinforced beam specimens with fiber content higher than 0.50% show deflection-hardening behavior. It is also found that free expansive rate of ESCC reduces with the increase of steel fibers content. Overall, fiber reinforced ESCC both at 0.25% and 0.50% volume content satisfy the target performance criteria.

Mineral carbonation using waste cement is a promising method to solve the problems caused by CO2 emission and waste cement. Compaction pressure is an important parameter for mineral carbonation of calcium hydroxide, one of the most dominant composite of waste cement that can be carbonated. The carbonation degree, morphology of products and compressive strength of carbonated compacts are influenced by compaction pressure significantly. Results show that the carbonation degree of calcium hydroxide increases at first (0-8 MPa) and then decreases in the higher compaction pressure range (10-14 MPa). At the meantime, results also indicate that lower compaction pressure accelerates the early carbonation but hinder carbonation in the later stages. For the morphologies of carbonation products, calcium carbonate tends to form typical crystal morphology of calcite (rhombohedral) under lower compaction pressure, while it will become ellipsoid-like when compaction pressure reaches 8 MPa. TGA and water content results show that there is an optimal water content for the carbonation. In addition, lower water content is adverse to the carbonation at later stage and the CO2 is difficult to penetrate into the inside of compacts when water content is high, which will hinder the carbonation. XRD and TGA results show that the carbonation products are calcite and small amount of amorphous calcium carbonate.

Calcium carbonate (CaCO 3 ) 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 CaCO 3 whisker-reinforced cementitious composites, rheological properties of fresh mixtures and the CaCO 3 whisker distribution in the hardened matrix were investigated. The yield stress and plastic viscosity increased with an increasing content of CaCO 3 whisker and a decreasing water-cement ratio. Also, the rheological properties were affected by the distribution of CaCO 3 whisker in the matrix. The largest increments in flexural and compressive strength were 27.59% and 12.60% for the mortars with CaCO 3 whisker contents of 2.0% and 1.5%, respectively. The properties responsible for the mechanical response were explained in terms of the effects of CaCO 3 whisker reinforcement, the distribution of CaCO 3 whiskers, and the porosity as well as pore size distribution.

Bitumen froth generated during the oil recovery operation from Athabasca oil sands needs to be cleaned to remove water and fine mineral solids for subsequent bitumen upgrading or pipeline transport. Two currently used bitumen froth cleaning methods, naphthenic froth treatment (NFT) and paraffinic froth treatment (PFT), either cannot generate market-spec bitumen froth (NFT) or causes losses of bitumen (PFT). In this study, a combination of hydrothermal treatment, venting and filtration was investigated to clean the bitumen froth. Laboratory hydrothermal treatment was conducted at 300–420 °C for 0–180 min. The filterability of fine solids was quantitatively characterized by room-temperature filtration or hot filtration at 200 °C. Mineralogical composition and particle size distribution of the untreated and treated fine solids were determined by quantitative X-ray diffraction using RockJock and focused beam reflectance measurement (FBRM) particle size analyzer. The microscopic observation of clay particle stacking behavior at the filter cake-filter medium interface was made by scanning electron microscope (SEM). The results show that hydrothermal treatment followed by venting and filtration is an effective way to remove water and fine solids from bitumen froth: the water content was reduced from 14 wt% to 0.03 wt%, and the fine solids content was reduced from 8 wt% to 0.08 wt% by hot filtration at 200 °C using a 0.5 μm pore size stainless steel filter medium. After hydrothermal treatment, no noticeable changes were observed to the clay mineralogy and fine solids particle size. However, the platy clay particles at the filter cake-filter medium interface turned from preferential orientation to random orientation due to the attachment of numerous ultrafine particles on the basal surface of the clay, increasing the porosity of the filter cake and facilitating the filtration. Such a change in the filter cake was hypothesized to be caused by the re-structuring of the organic-mineral aggregates into the ultrafine-particle-coated platy clays, releasing the organics and the ultrafine solids during the hydrothermal treatment. The released ultrafine solids then adsorbed onto the clay platelets. It was indeed observed that the total organic carbon content of the bulk fine solids decreased from 14.7 wt% to 10.3 wt%, but the carbon concentration on the fine solids surface increased from 35.6 at.% to 47.7 at.%.

A novel kind of cement blend with high temperature resistance and favorable sustainability was developed in this paper. The physical and chemical changes due to high temperature exposure were examined in this sustainable cement paste containing fly ash (FA) and aragonite calcium carbonate whiskers (CW) as supplementary cementitious materials. High flexural strength is demonstrated before 400 °C because FA has pozzolanic effect, self-cementitious properties and potentials to react with CW under hydrothermal condition. When the exposure temperature is above 400 °C, especially above 800 °C, high residual properties and less deterioration are observed in flexural and compressive strengths and elastic modulus, mainly because FA is involved in the sintering process and formation of ceramic phases. In summary, the sustainable cementitious composites studied in this paper are very promising to have high temperature resistance to reduce fire damage on constructions and at the same time lower carbon dioxide footprint of cement manufacture.

Calcium carbonate whisker (CW) is used to modify the steel-PVA hybrid fibers reinforced cementitious composites (SPFRCC). The addition of CW result in excellent mechanical properties and considerable economic benefit owing to its microscopic reinforcement effect and low cost. In this study, the flexural behavior, fiber distribution characteristics and compression response of CW modified steel-PVA hybrid fibers reinforced cementitious composites (CW-SPFRCC) are investigated by three-point bending test, image processing technique and uniaxial compression test, respectively. The results indicate that the addition of CW can effectively improve the flexural properties of SPFRCC because of the crack resistance and filling effect at microscale. The best fiber distribution characteristics are observed in CW10-S15P05 due to the presence of CW that modify the adhesion and flowability of cement matrix. The uniaxial compression strength, peak strain, elastic modulus and Poisson's ratio of CW-SPFRCC are increased by 37.1%, 40.2%, 3.7% and 30.7%, respectively. Meanwhile, the uniaxial compression constitutive model is proposed to describe the compression stress–strain relationship of CW-SPFRCC based on the experimental results. Moreover, the microstructure analysis demonstrates that the modification mechanism of CW in SPFRCC is attributed to the interface improvement, CW pull-out, CW slippage, and CW rupture.

eco-efficient cementitious composites are widely used in buildings and structures which are usually exposed to high temperatures and high pressure because of their high temperature resistance abilities. In order to figure out the effects and mechanisms of supplementary cementitious materials (SCMs) on improving high temperature resistance of eco-efficient cementitious composites, the effects of fly ash (FA), silica fume (SF) and granulated blast furnace slag (GBFS) on residual mechanical properties of thermally damaged cementitious composites were systematically reviewed based on some relevant literatures. Also, self-healing properties of thermally damaged eco-efficient cementitious composites induced by post-fire-curing were summarized to better understand the comparative roles of SCMs. The results showed that FA and GBFS were favorable to improve the residual properties, but SF was less effective than FA and GBFS. Extensive cracking and spalling were more frequently performed on heated cementitious composites containing SF. However, all these SCMs were effective to improve the self-healing properties of thermally damaged cementitious composites. This review mainly focuses on developing functionalized cementitious composites with both high temperature resistance and self-healing. Furthermore, to promote high volume utilization of SCMs in developing eco-efficient cementitious composites is another purpose of this review.

By experimental research on the steel- polyvinyl alcohol (PVA) fibers- calcium carbonate whisker (CW) multi scale fiber-reinforced cement-based composites (MSFRC) after exposure of temperatures up to 900 °C, the flexural, compressive strength, and microstructures of multi scale fibers were investigated in this paper. The incorporation of steel-PVA fibers-CW can effectively improve the flexural and compressive strength of mortar after elevated temperatures. Compared with normal concrete, hybrid fiber reactive powder concrete (RPC) and engineered cement-based composites (ECC), the MSFRC present better capacity of high temperature resistance. The flexural and compressive strength increase first and then decrease with the increasing temperature, and the critical temperatures are 200 °C and 400 °C respectively. Models for describing the relationship between strength, CW content and temperature are proposed. The good high temperature resistance of MSFRC relates to the hybrid effect of melt of PVA fiber, good heat conduction of steel, and the phase transformation from aragonite to calcite of CW. Comprehensive morphology observations by digital camera and optical microscope are simple and useful way to evaluate the changes of fibers and CW at high temperature. This research is very beneficial for the applications of MSFRC in construction project with fire risk.

Recently, CaCO3 whiskers (CW) are used as new-type micro-fibers for achieving reinforcing and toughening of cement-based materials due to their cracking resistance ability at micro-scale. In this paper, the combination of steel-polyvinyl alcohol (PVA) fibers are added into CW reinforced cement mortar (CWRCM) to further enhance the reinforcing and toughening effects at meso- and macro-scales. In addition, four analytical models of fiber reinforced cementitious composites (FRCC) were developed to describe the compressive stress-strain response. The cylindrical specimens are tested under uniaxial compressive loading to investigate the effect of different volume fractions of steel-PVA hybrid fibers in CWRCM. The test results indicated that the incorporation of steel-PVA hybrid fibers could significantly improve the stress-strain behavior of CWRCM, as compared to that of the CWRCM. The highest ultimate compressive strength (fc), elasticity modulus (Ec) and total compressive strain energy (ED) were observed in SF1.8PF0.2, but SF1.5PF0.5 showed a greater peak strain (eu). Moreover, the prediction models of compressive parameters were proposed by simultaneously considering the reinforcing index (RI) of steel and PVA fibers. The obtained parameters in four models were evaluated according to their essential requirements. It was found that only Model III met its essential requirements and parameters were closely associated with RI values of steel and PVA fibers.

Cracking is a multi-level process that damages the concrete structure or cement-based material. Nowadays, multi-scale hybrid fibres can be utilized in concrete to get more resistance against cracking. In this work, the reinforcing index and constitutive modelling are studied for plain concrete, single fibre reinforced concrete, two hybrid fibres reinforced concrete and multi-scale hybrid fibres reinforced concrete having different basalt fibre contents. The reinforcing index is calculated for hybrid fibres and empirical equations between strength properties and reinforcing index are developed. Also, the constitutive models of the compressive stress-strain relationship are well established and the comparison between experimental data and different models are made. Furthermore, energies absorbed and toughness indexes are obtained for compressive and flexural properties from the stress-strain and load-deflection curves, respectively. The SEM analysis is done to study the multi-level cracking mechanism and fibre-matrix bond. The results of empirical equation showed satisfactory results of strength properties with that of experimental results. The results obtained from different mathematical model of uniaxial compressive stress-strain curve are in good agreement with experimental data. It is revealed that the optimal mechanical properties for multi-scale hybrid fibre reinforced concrete was observed with 0.8% basalt fibre content, 1% CaCO3 whisker and 0.25% steel fibre content.

Building fire disasters may cause large economic loss and casualties. To improve the fire resistance ability of concrete and repair the fire-damaged concrete structures using an in-situ repairing technique (such as post-fire-curing) can greatly offset these adverse effects. Thus, the present study employed fly ash (FA) to form a CW-FA-cement system which was proved to enhance the high-temperature resistance of cement and CW blended cement and was also favorable for recovery of compressive strength and microstructure induced by water re-curing. In details, incorporation of FA was effective to reduce the deterioration of cement and CW blended cement and was favorable for recovery of compressive strength and microstructure after water re-curing. Incorporation of CW was favorable to increase the restorability of compressive strength re-cured after 400 °C and performed a combined effect with FA to improve the recovery of compressive strength re-cured after 800 °C. Through the microstructural tests, the deterioration of compressive strength was due to the decomposition of hydration products. The recovery of compressive strength was due to the rehydration of dehydrated cement, further hydration of unhydrated cement particles, pozzolanic effect of FA and combined effect of CW and FA. Furthermore, the cement blends containing CW and FA had a good high temperature resistance and restorability.

Calcium carbonate whisker is an emerging class of inorganic fiber having tremendous properties and vast applications. Calcium carbonate whisker is extensively used as a filler due to its tremendous properties including low price, simple preparation requirements and ease of availability. As a filler, it increases the physical and chemical properties such as heat resistance, strength and modulus. Its unique properties are seeking the attention of researchers for utilizing it as a filler in various applications. In this paper, different basic preparation techniques of calcium carbonate whisker such as metathesis reaction, sol-gel, carbonation, gravity crystallization and urea hydrolysis are described briefly. In addition to this, the review focus on research advancements achieved in the utilization of calcium carbonate whisker in different applications such as friction materials, paper making, reinforcing composite materials, cement, mortar and concrete. Calcium carbonate whisker is mostly used for enhancing the properties of cementitious materials. In this review, a special emphasis is given to the role of whisker in cementitious materials such as cement, concrete and mortar.

Functionalized graphene nanosheets (FGNs) with high surface area and various functional groups were prepared by oxidation method. The characteristics of FGNs were studied by nitrogen adsorption using the Brunauer-Emmett-Teller (BET) method, Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersion spectrum (EDS), and atomic force microscopy (AFM). The specific surface area of obtained FGNs was measured as 834.06 m2 g−1, which was 20–40% higher than graphene nanosheets (GNs) before oxidation. An abundance of oxygen-containing functional groups, such as carboxyl, hydroxyl and epoxy groups, was grafted on the edge and surface of GNs. Moreover, FGNs demonstrated excellent adsorption and desorption performance when used as absorbent to remove Cu (II) from aqueous solution. The removal percentage could reach 96% within 1 h and remain 72% after 5 adsorption-desorption cycles. Adsorption process and mechanism were elucidated by kinetics models and isotherm models. The results showed FGNs has a great potential to be an adsorbent for removal copper ions from water.

International audience; Organic materials such as polyanthraquinone sulfide (PAQS) are receiving increased attention as electrodes for energy storage systems owing to their good environmental compatibility, high rate capability, and large charge‐storage capacity. However, one of their limitations is the solubility in Organic solvents typically composing the electrolytes. Here, the solubility of PAQS was tested in 17 different solvents using UV/Vis spectroscopy. The results show that PAQS exhibits a very wide range of solubility according to the nature of the solvent and the obtained trend agrees well with the predictions from Hansen solubility analysis. Furthermore, the transport properties (conductivity, σ, and viscosity, η) of selected electrolytes composed of non‐solubilising solvents with 1 m LiTFSI are compared and discussed in the temperature range from −40 °C to 80 °C. In the second part of this study, the electrochemical characterization of PAQS as electrode material in selected pure or mixture of solvents with 1 m LiTFSI as salt was made in half‐cells by a galvanostatic method. In a methylglutaronitrile (2MeGLN)‐based electrolyte that exhibits low solubility of PAQS, it appears that the capacity fade is intricately linked to the large irreversibility of the second step of the redox process. Although the standard cyclic carbonate solvents mixture (ethylene carbonate and propylene carbonate) led to rapid capacity fade in the initial 10–15 cycles owing to their high solubilising ability. Finally, it is shown that a pure linear alkylcarbonate (dimethyl carbonate) or binary mixture of ether‐based (dioxolane/dimethoxy ethane) electrolyte is much more compatible for enhanced capacity retention in PAQS with more than 120 mAh g−1 for 1000 cycles at 4 C.

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.

A new kind of fiber hybridization containing steel fibers, polyvinyl alcohol (PVA) fibers and cheap calcium carbonate (CaCO 3 ) 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 CaCO 3 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 CaCO 3 whisker, thus helping to decrease the production cost of fiber reinforced cementitious composites for large scale construction project applications in the future.

Calcium carbonate whisker (CW) could improve mechanical properties of cementitious composites at room temperature. Aiming at using CW as high-performance and low-cost microfiber at high temperature, the microstructural changes of cementitious composites with CW exposed to high temperature are clarified in this research. From room temperature to 500 °C, additional hydration of unhydrated binder grains in steam environment occur (“internal autoclaving”). Moreover, CW transferred from aragonite to calcite in cement paste at about 375 °C (“phase transformation”). Under these coupling effects, calcite CW forms stronger bond with these rehydration products than that at room temperature, also improving the pore distribution and compressive strength. At 800 to 1000 °C, CW increases the pore size and decreases the compressive strength of cement paste due to CW decomposition. From 1000 to 1100 °C, the residual compressive strengths of CW reinforced cement pastes increase slightly because of the forming of calcium silicate and Ca(OH)2.

Aragonite CaCO3 whisker (CW) could improve the mechanical properties of cementitious composites. The microstructure of calcite is different from that of aragonite, but only a few studies reported different effects in cementitious composites between incorporating aragonite and calcite. In order to fully use CW as high-performance, low-cost microfiber and clearly understand different mechanisms between aragonite and calcite CW, in this study, the heat treatment method was used to convert aragonite CW to calcite CW, and the effect of calcite and aragonite on the hydration and strength of CW reinforced cement paste (CWRC) was studied to bridge the gaps in this area. The aragonite and calcite CWs exhibited the overall physical dilution effect in Portland cement, significantly decreasing the hydration heat of cement and the total amount of non-evaporable water and Ca(OH)2. Calcite CW presents a more significant nucleation effect than aragonite CW. Compared to aragonite CWRC, the hydration of silicon phase in calcite CWRC is faster and the hydration heat release is higher; however, there is no significant difference in the hydration of aluminum phase. The Ca(OH)2 content in calcite CWRC was more than that in aragonite CWRC. More hydration products formed on the surface of calcite CW than that on aragonite CW, improving the bonding strength between calcite CW and cement matrix. Hence, both the compressive strength and flexural strength of calcite CWRC are higher than those of aragonite CWRC. The rheological test of fresh aragonite and calcite CWRC proved that both aragonite and calcite CWs significantly decreased the flow of cement paste, presenting viscosity effect. Compared to aragonite CW, calcite CW improved the flowability of fresh cement paste, indicating the lubricant effect of calcite CW. Aragonite and calcite CW present chemical effect similar to limestone powders, i.e., aluminum phase in Portland cement interacted with CO32- dissolved from CW to form mono- and semi- carbonate. The Ca(OH)2 orientation indexes of cement decreased by the introduction of CWs. Aragonite and calcite CWs can also be used as microfiber and filler in cementitious composites. These effects improved the micro-structure, thus enhanced the flexural and compressive strength of cement paste.

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.

Chitosan was exploited as a selective depressant in the differential Pb Zn sulfide flotation at pH 4 on artificial galena and sphalerite mixtures. The mixtures were prepared in two different approaches. In the first approach, the high purity galena and sphalerite were blended directly whereas in the second approach, the sphalerite was coated with copper before blending with galena. Using the first approach, it was found that lead ions contaminated the sphalerite surface making the separation non-selective. After adding EDTA, sphalerite was depressed by chitosan while galena was floated at pH 4. Using the second approach, i.e., that the sphalerite was pre-coated with copper before mixing with galena, it was found that the sphalerite was selectively depressed by chitosan without the need to add EDTA. ToF-SIMS and XPS were used to study the interactions of chitosan with uncoated sphalerite and copper-coated sphalerite. The results indicated that the amine groups and the hydroxyl groups in chitosan were involved in the strong interaction between chitosan and sphalerite whether the latter was coated by copper or not. Chitosan did not interact strongly with galena as reported previously.

Chitosan was used in the flotation of pyrite–galena mixtures. The results indicated that chitosan preferentially adsorbed on pyrite and galena was floated from the pyrite–galena mixtures. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) analyses were performed to study the interaction mechanism of chitosan on the pyrite and galena minerals at pH 4 and 6. ToF-SIMS showed that chitosan adsorbed heavily on pyrite but barely on galena when a mixture of pyrite and galena was treated by chitosan. The high resolution XPS spectra indicated that both the amine and the hydroxyl groups from chitosan reacted with pyrite surface, whereas no significant binding energy shifts were observed on galena. Combined with the authors’ previous studies of chitosan in other sulfide flotation systems, it was observed that chitosan could depress pyrite, galena, sphalerite and chalcopyrite to different extent when the minerals were floated alone. However, in the flotation of mineral mixtures, chitosan selectively adsorbed on one mineral which depressed its flotation, allowing the other mineral to be floated from the mixture. The competitive adsorption was attributed to the differences in the electron affinity value of the lattice metal ions. Chitosan strongly binds with metal ions with a high electron affinity.

Restriction of propagation and coalescence of cracks at microscopic level is one of the most effective means to achieve high properties of cement based composite. In order to improve the properties of cement based composite microcosmically, calcium carbonate whisker was introduced as a kind of microreinforcer. The effects of whisker on macro and micromechanical properties, fracture morphology, microstructures, and crack resistance of the composite with different water to binder ratios, as well as the reinforcing mechanisms were studied. The results indicated that whiskers are effective in delaying the formation and propagation of microcracks. The micromechanical mechanism is relative to the bond properties between whiskers and cement matrix. An appropriate interfacial bond strength is advantageous to optimize the reinforcing effect of whisker in cement based composite.

The focus of this paper is given to investigate the effect of different fibers on the pore pressure of fiber reinforced self-consolidating concrete under fire. The investigation on the pore pressure-time and temperature relationships at different depths of fiber reinforced self-consolidating concrete beams was carried out. The results indicated that micro PP fiber is more effective in mitigating the pore pressure than macro PP fiber and steel fiber. The composed use of steel fiber, micro PP fiber and macro PP fiber showed clear positive hybrid effect on the pore pressure reduction near the beam bottom subjected to fire. Compared to the effect of macro PP fiber with high dosages, the effect of micro PP fiber with low fiber contents on the pore pressure reduction is much stronger. The significant factor for reduction of pore pressure depends mainly on the number of PP fibers and not only on the fiber content. An empirical formula was proposed to predict the relative maximum pore pressure of fiber reinforced self-consolidating concrete exposed to fire by considering the moisture content, compressive strength and various fibers. The suggested model corresponds well with the experimental results of other research and tends to prove that the micro PP fiber can be the vital component for reduction in pore pressure, temperature as well spalling of concrete., National Natural Science Foundation of China (Grant: 51121005), DUT and Fundaçãopara a Ciência e a Tecnologia (SFRH/BPD/22680/2005), the FEDER Funds through “Programa Operacional Factores de Competitividade - COMPETE" and by Portuguese Funds through FCT-within the Projects PEst-CMAT/UI0013/2011 and PTDC/MAT/112273/2009.

A xanthation-modified polyacrylamide (PAM), named PAM-X, was synthesized. In single mineral flotation tests, PAM-X exhibited unique selectivity between galena and Cu-activated sphalerite. The adsorption mechanisms were investigated via attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). It was observed that PAM-X had different absorption band shifts when adsorbed onto galena and Cu-activated sphalerite, indicating the formation of different adsorption bonds between PAM-X and the minerals. The analysis by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) revealed that PAM-X was a mixture composed of partially hydrolyzed PAM and a low molecular weight sulfur-bearing compound. The observed selectivity of PAM-X to galena and Cu-activated sphalerite was attributed to the adsorption of the PAM-X and the synergistic effect of its two components.

Anionic collectors (phosphonic acid and hydroxamic acid) and flotation depressants were tested in a modified small-scale flotation tube on high purity single minerals in order to find a suitable reagent combination for niobium oxide mineral flotation from its ores. High purity calcite and quartz were used to represent carbonate and silicate gangue minerals and pyrochlore was used to represent the niobium oxide mineral. Only hydroxamic acid could float pyrochlore at natural pH, with recoveries over 90%. However, it floated calcite as well. To separate the pyrochlore from the carbonate gangue, sodium metaphosphate was used. Single mineral and mineral mixture tests indicated that the calcite could be selectively depressed by the sodium metaphosphate. Bench-scale flotation tests were carried out on a carbonatite niobium ore sample, and they showed that the reagent combination, at less than 2 kg/t Aero 6493 (hydroxamic acid) and 1.0 kg/t sodium metaphosphate, could recover over 90% of niobium oxide from the ore feed at about 30% mass pull. The results indicated that the combination of hydroxamic acid and sodium metaphosphate is a possible reagent scheme for pyrochlore recovery from niobium oxide ores.

Chitosan was recently found to be a potential replacement for toxic inorganic depressants commonly used in the flotation separation of Cu–Pb sulfide minerals. The current work focused on the interaction mechanisms and investigated the reasons for the preferential adsorption of chitosan on copper sulfide (chalcopyrite) over lead sulfide (galena). Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) were employed in the study. ATR-FTIR spectra of chitosan showed that the absorption peaks due to amino groups shifted upon adsorption on chalcopyrite. High resolution XPS spectra detected binding energy shifts of N 1s and O 1s electrons on chitosan-treated chalcopyrite. ToF-SIMS ion mass spectra revealed CuNH 3 as the dominant stable species as a result of chalcopyrite–chitosan interactions. It was therefore concluded that the adsorption of chitosan on chalcopyrite was due to a strong chemical interaction between the surface copper atoms and the protonated amine as well as the hydroxyl groups on chitosan. Such a strong chemical interaction was not observed on galena.

Chitosan, a natural polymer extracted from crustacean shells, was found to selectively depress chalcopyrite while galena was floated by xanthate. At pH 4, the recovery of galena was up to 95% while that of chalcopyrite was 30% when flotation tests were carried out on mixtures of chalcopyrite and galena. However, in single mineral flotation and adsorption tests, it was found that both chalcopyrite and galena were depressed and chitosan adsorbed on both minerals. The observed selectivity seemed to have originated from competitive adsorption. ToF-SIMS measurements indicated that when chalcopyrite and galena were present together in the suspension, chitosan barely adsorbed on galena but adsorbed heavily on chalcopyrite. Chitosan-metal ions adsorption test, X-ray photoelectron spectroscopy (XPS) as well as ToF-SIMS were employed to study the interaction of chitosan with chalcopyrite and galena and to delineate the observed competitive adsorption. Chitosan could potentially be used in differential Cu–Pb sulfide separation to replace the hazardous inorganic depressants such as cyanide, dichromate and sulfur dioxide.

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.

In order to explore the serviceability and reinforcement of CaCO3 whisker in portland cement matrix, the durability of CaCO3 whisker and effect of low whisker content(0%–4.0%) on the working performance and mechanical properties of portland cement were investigated. The experimental results show that CaCO3 whiskers have a good stability and serviceability in cement, and should not significantly alter the rheological properties of the cement paste. The flexural and compressive strength of portland cement reinforced by CaCO3 whiskers was increased by 33.3% and 12.83%, respectively.

Drug resistance is a major obstacle in cancer treatments and diminishes the clinical efficacy of biological, cytotoxic, or targeted therapeutics. Being an antiapoptotic mediator of chemoresistance in breast and lung cancer cells, MKP1 phosphatase might be targeted for overcoming chemoresistance and improving therapeutic efficacy. In this work, tyrosine phosphatase inhibitor-3 (TPI-3) was identified as a novel small molecule inhibitor of MKP1 and was capable of sensitizing tumors to bio- and chemotherapeutics in mice as a tolerated oral agent. Effective against recombinant MKP1, TPI-3 selectively increased MKP1 phosphosubstrates in Jurkat cells and induced cell death via apoptosis at nanomolar concentrations. TPI-3 also increased MKP1 phosphosubstrates in WM9 human melanoma cells and synergized with biotherapeutic IFNα2b in the growth inhibition of melanoma cells in vitro (combination index

A montmorillonite inorgano-intercalation compound(MIIC) was synthesized by using a purified Na-exchanged bentonite (PNaB) as a matrix and Al-pillaring ion as an intercalating reagent under microwave irradiation. The synthesized products were characterized by X-ray diffraction (XRD), 27Al magic angle sample-spinning nuclear magnetic resonance (27Al MAS NMR), specific surface area (BET) measurement, and adsorption density determination. The results show that, at 5% solid (PNaB) concentration and 7 minutes irradiation in a 130 W microwave oven, the basal spacing d(001) of the synthesized MIIC increases to 1.740 nm from the original 1.218 nm of PNaB. The MIIC has much higher adsorptive densities to F− and Cr6+ from aqueous solution than the PNaB. The adsorption isotherm of F− on the MIIC follows the Freundlich equation, and the increased adsorption is mainly due to the porous structure of the MIIC which created larger adsorption surfaces. The adsorption isotherm of Cr6+ on MIIC follows the Langmuir equation and the adsorption is mainly monolayer as a result of chemisorptions.

The multiscale nature and multiscale cracking behavior of cementitious composite determine its micro-, meso-, and macroperformance. A new kind of fiber hybridization containing steel fiber, polyvinyl alcohol (PVA) fiber, and cheap calcium carbonate (CaCO3) whisker (approximately $230 per ton) was designed to increase the multiscale cracking resistance for cementitious composites. Mechanical properties, microstructures, reinforcing mechanisms, and economic efficiency of this designed hybrid fiber-reinforced composite were presented. The results indicated that both the flexural strength and flexural toughness are significantly improved. Scanning electron microscopy images and fracture tests confirmed that the interaction of different fibers and multiscale cracks contributes to enhancing the mechanical properties of cementitious composite, which is also reflected in its deflection hardening performance and multiple cracking behavior. Moreover, it seems possible that the steel fibers and PVA fibers ca...

The influence of TiCl 3 solution on the room temperature resistivity and the electrical properties of Ba 0.92 Ca 0.08 TiO 3 positive temperature coefficient resistance (PTCR) ceramics were studied. The results indicate that the PTC effect can be improved significantly when an appropriate amount of TiCl 3 in solution is added to the raw materials. The carrier concentration ( N d ), the surface charge density ( N s ), and the barrier height at grain boundaries ( φ ) were calculated by AC complex impedance analysis. The segregation of Ti 3+ at the grain boundaries is believed to have enhanced the PTC effect.

Asphalt pavements were liable to suffer from structural damage at early stage, so the goal is to reduce such damage in order to improve both social and economic benefits in pavements' lifespan. In this paper, damages at early stage were classified, meanwhile, the basic character and the reasons for the asphalt pavement early damages were also discussed, and the precautionary measurements were put forward accordingly.

CaCO 3 whiskers were incorporated into cement composites in this paper and the effects of whiskers on the physical properties of cement composites were studied, including the fluidity and dry shrinkage of mortar and the pore structure of cement paste. The results showed that the fluidity of cement mortar was decreased gradually with the CaCO 3 whisker content increasing and when the whisker content was in the range of 10%, the fluidity had no significant degradation; when the whiskers were mixed in the mortar with the content of 5% and 10%, the effect on the dry shrinkage of mortar was not obvious and with the content increasing further, the dry shrinkage was increased; through the analysis of mercury intrusion porosimetry(MIP) test, it was shown that the porosity of cement paste was increased with the whisker content increasing and when the content was less than 20%, there was no significant change in the main distribution of pore size and the increase of less harmful pores below 50nm was dominant.

“Construction Laws and Regulations” course is a required course for civil engineering specialty in institutions for higher learning. Through years’ exploration, the author, guided by the concept to “Implement elite education and cultivate elite talents” advocated by Academician Ou Jinping, puts forward the teaching method for Construction Laws and Regulations course centering on “student-centered” and “interactive teaching”, which achieves rather desirable teaching effects. The thesis expounds systematically from the aspects of the meaning of interactive teaching, the construction of supporting textbooks, lecturing methods in classroom, simulated training in law enforcement, case teaching, the construction of supporting courseware, performance evaluation, teaching effects and others. It discusses matters needing attention concerning interactive teaching method in teaching implementation. Through years’ practice, the method achieves favorable teaching effects and is of high promotion value.

Disruption of the circadian rhythm or biological clock, which is regulated by a number of clock genes, including circadian locomotor output cycles kaput (CLOCK), period genes (PERs), and cryptochrome genes (CRYs), is a risk factor for breast cancer. We hypothesized that genetic variation in these clock genes may influence breast cancer risk. To test this hypothesis, we designed a hospital-based study that included 1,538 breast cancer patients and 1,605 healthy controls. We genotyped subjects for five single nucleotide polymorphisms (SNPs) and a length variant of the circadian clock genes and evaluated their associations with breast cancer risk. These polymorphisms were determined by TaqMan allelic discrimination assays and the polymerase chain reaction-restriction fragment length polymorphism method. Univariate logistic regression analysis showed that polymorphisms of the CLOCK and CRY1 genes were associated with breast cancer risk. We found that carriers of the CLOCK CT and combined CT+TT genotypes had a significantly higher risk of breast cancer than carriers of the CC genotype (aOR = 1.35, 95% CI = 1.12-1.63 and aOR = 1.30, 95% CI = 1.09-1.56, respectively). Carriers of the CRY1 GT genotype had a decreased risk of breast cancer (aOR = 0.84, 95% CI = 0.71-0.99). We also observed a lower risk of breast cancer in carriers of the CRY2 CC genotype who were ER-positive than in those who were ER-negative (OR = 0.15, 95% CI = 0.04-0.67). When stratified by the CLOCK genotype, patients with the CLOCK CT/ CRY2 CC genotypes had significantly lower cancer risk than those with the GG genotype (aOR = 0.36, 95% CI = 0.14-0.95). Individuals carrying both the CLOCK CC and PER2 AA genotypes had an increased cancer risk (aOR = 2.28, 95% CI = 1.22-4.26). Our study suggests that genetic variants of the circadian rhythm regulatory pathway genes contribute to the differential risk of developing breast cancer in Chinese populations.

Src homology region 2 domain-containing phosphatase 1 (SHP-1) has been implicated as a potential cancer therapeutic target by its negative regulation of immune cell activation and the activity of the SHP-1 inhibitor sodium stibogluconate that induced IFN-γ+ cells for anti-tumor action. To develop more potent SHP-1-targeted anti-cancer agents, inhibitory leads were identified from a library of 34,000 drug-like compounds. Among the leads and active at low nM for recombinant SHP-1, tyrosine phosphatase inhibitor-1 (TPI-1) selectively increased SHP-1 phospho-substrates (pLck-pY394, pZap70, and pSlp76) in Jurkat T cells but had little effects on pERK1/2 or pLck-pY505 regulated by phosphatases SHP-2 or CD45, respectively. TPI-1 induced mouse splenic–IFN-γ+ cells in vitro, ∼58-fold more effective than sodium stibogluconate, and increased mouse splenic-pLck-pY394 and –IFN-γ+ cells in vivo. TPI-1 also induced IFN-γ+ cells in human peripheral blood in vitro. Significantly, TPI-1 inhibited (∼83%, p < 0.002) the growth of B16 melanoma tumors in mice at a tolerated oral dose in a T cell-dependent manner but had little effects on B16 cell growth in culture. TPI-1 also inhibited B16 tumor growth and prolonged tumor mice survival as a tolerated s.c. agent. TPI-1 analogs were identified with improved activities in IFN-γ+ cell induction and in anti-tumor actions. In particular, analog TPI-1a4 as a tolerated oral agent completely inhibited the growth of K1735 melanoma tumors and was more effective than the parental lead against MC-26 colon cancer tumors in mice. These results designate TPI-1 and the analogs as novel SHP-1 inhibitors with anti-tumor activity likely via an immune mechanism, supporting SHP-1 as a novel target for cancer treatment.

Mutual coagulation tests were conducted between hexadecane droplets (with and without doping with 0.001 mol/L sodium oleate) and micrometer-sized quartz, kaolinite, and illite particles in the presence and absence of multivalent hydrolyzable metal cations. It was observed that while hexadecane did not coagulate with quartz particles in the entire pH range tested (from 3 to 11), the presence of multivalent metal ions significantly increased the mutual coagulation between the hexadecane and quartz. And this only happened when the pH was raised to the level where first-order metal hydroxyl species and/or metal hydroxides were formed. The implications of this mutual coagulation for bitumen liberation from Alberta oil sands are discussed.

Zinc sulfate is a well-known selective depressant for zinc sulfide minerals such as sphalerite during the flotation of complex Cu-Pb-Zn sulfide ores. It deactivates sphalerite flotation by substituting the activating metal ions, and depresses sphalerite flotation by forming hydrophilic coatings of zinc hydroxyl species on sphalerite surfaces. However, we recently observed that zinc sulfate could also induce coagulation of fine sphalerite particles and such coagulation significantly reduced the mechanical entrainment of the fine sphalerite. Therefore, it seems that the effectiveness of zinc sulfate as a selective sphalerite depressant is not only due to its ability to make mineral surface hydrophilic, which reduces genuine flotation, but also due to its ability to coagulate the mineral, which reduces mechanical entrainment. Zinc sulfate is a "dual function" selective flotation depressant.