Titanium dioxide (TiO2) porous ceramic pellets with three dimension nano-structure were prepared using nano TiO2 powder. The TiO2 porous ceramic pellets were composed of TiO2 nanoparticles with 14–16 nm in diameter and had porosity of 74.85%. The mean pore size of the TiO2 porous ceramic pellets was 20.73 nm and the main pore size ranged from 3 to 16 nm. The mass loss of the TiO2 ceramic pellets was less than 5% after 20 d immersion in water. The antibacterial properties of the TiO2 pellets were studied. The sterilization rate of Colibacillus (hospital polluted water with bacterium) can reach 99% after 3 h photocatalytic process and these TiO2 pellets are easy to be re-activated and cyclically be used. The shaping mechanism and photocatalysis sterilization mechanism of the TiO2 pellets were discussed.
Cr-doped Li3V2(PO4)3 cathode materials Li3V2−xCr x(PO4)3 were prepared by a carbothermal reduction(CTR) process. The properties of the Cr-doped Li3V2(PO4)3 were investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM), and electrochemical measurements. Results show that the Cr-doped Li3V2(PO4)3 has the same monoclinic structure as the undoped Li3V2(PO4)3, and the particle size of Cr-doped Li3V2(PO4)3 is smaller than that of the undoped Li3V2(PO4)3 and the smallest particle size is only about 1 μm. The Cr-doped Li3V2(PO4)3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra(EIS). The optimal doping content of Cr was that x=0.04 in the Li3V2−xCr x(PO4)3 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li3V2(PO4)3 cathode materials are attributed to the addition of Cr3+ ion by stabilizing the monoclinic structure.
Mg3(PO4)2-coated Li1.05Ni1/3Mn1/3Co1/3O2 cathode materials were synthesized via co-precipitation method. The morphology, structure, electrochemical performance and thermal stability were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), charge/discharge cycling and differential scanning calorimeter (DSC). SEM analysis shows that Mg3(PO4)2-coating changes the morphologies of their particles and increases the grains size. XRD and CV results show that Mg3(PO4)2-coating powder is homogeneous and has better layered structure than the bare one. Mg3(PO4)2-coating improved high rate discharge capacity and cycle-life performance. The reason why the cycling performance of Mg3(PO4)2-coated sample at 55 °C was better than that of room temperature was the increasing of lithium-ion diffusion rate and charge transfer rate with temperature rising. Mg3(PO4)2-coating improved the cathode thermal stability, and the result was consistent with thermal abuse tests using Li-ion cells: the Mg3(PO4)2 coated Li1.05Ni1/3Mn1/3Co1/3O2 cathode did not exhibit thermal runaway with smoke and explosion, in contrast to the cells containing the bare Li1.05Ni1/3Mn1/3Co1/3O2.
Nanocomposites MgFe2O4/SiO2 were successfully synthesized by the sol-gel method in the presence of N, N-dimethylformamide (DMF). The formation of pure MgFe2O4 was confirmed by powder X-ray diffraction (XRD) and electron diffraction. The structural evolution of MgFe2O4 nanocrystals was followed by powder X-ray diffraction and IR absorption spectroscopy. The formation of spinel structure of MgFe2O4 started at 800 °C, and completed at 900 °C. The transmission electron microscopy (TEM) measurements suggest that the particle sizes increase with the increasing annealing temperature, and the mean particle sizes of the spherical samples annealed at 800 °C, 900 °C and 1 050 °C are ca. 3 nm, 8 nm and 11 nm, respectively. Magnetization measurements at room temperature and 78 K indicate superparamagnetic nature of these MgFe2O4 nanocrystals.
Fatigue-free Bi3.2La0.8Ti3O12 ferroelectric thin films were successfully prepared on p-Si (100) substrates using metalorganic solution deposition process. The orientation and formation of 5-layers thin films were studied under different processing conditions using XRD. Experimental results indicate that increase in annealing time at 700 °C after preannealing for 10 min at 400 °C can remarkably increase (200)-orientation of the films derived from the precursor solutions with two contents of citric acid. Meanwhile, high content of citric acid increases the film thickness and is conducive to the a-orientation of the films with the preannealing, and low concentration of the solution is conducive to the c-orientation of the films without the preannealing.
The process of preparing SiC coating by electron beam-physical vapor deposition (EB-PVD) was discussed from viewpoint of thermodynamis. Results show that within the temperature range of 2 700–3 300 K, the ratio of SiC in the SiC coating doesn’t change much and keeps around 0.7. Purity of the as-deposited SiC coating is not high. To improve the purity of the SiC coating, the SiC ingot is required to not be, necessary in full density but be fine-grained.
A series of dimer acid-based polyamides were synthesized by melt-polycondensation of dimer acid and various aromatic diamines, and were characterized by Fourier transform infrared spectrum (FT-IR) and nuclear magnetic resonance (1H NMR). The physical properties of the polyamides, such as glass transition temperature, melting temperature, decomposition temperature and mechanical properties were also investigated. The polyamides’ intrinsic viscosity ranges from 1.8 dL·g−1 to 2.2 dL·g−1, and the melting temperature ranges from 140 °C to 181 °C. The glass transition temperatures, observed from dynamic mechanical analysis, fall in the range of 34.8–48.2 °C. The physical and mechanical properties of the resultant polyamides are similar to those of the PA1212. The heat resistance and mechanical properties of poly (4, 4′-diphenylsulfone dimeramide) (PSD) and poly(4, 4′-diphenyl dimeramide) (PPDI) are comparable to those of PA1212.
A novel environmental friendly catalyst, H4SiW12O40/PAn was prepared and identified by FT-IR, XRD and TG/DTA. The optimal synthetic protocol was a PAn to H4SiW12O40 mass ratio of 1: 1, a 20 mL of methanol and a reaction time of 2 h at reflux. It was used in catalytic synthesis of ten important ketals and acetals with a high catalytic activity. With an aldehyde/ketone to glycol molar ratio of 1: 1.5 and a 1 wt% catalyst loading, the yields of ketals and acetals could reach 60.0%–93.8 % after 1 h.
Two-dimensional (2D) transient coupled finite element model was developed to compute the temperature and stress field in cast billets, so as to predict the defects of the I-type billets made from AZ31 magnesium alloy and find the causes and solutions for surface cracks and shrinkages during direct-chill (DC) casting process. Method of equivalent specific heat was used in the heat conduction equation. The boundary and initial conditions used for primary and secondary cooling were elucidated on the basis of the heat transfer during the solidification of the billet. The temperature and the thermal-stress fields were simulated with the thermal-structural coupled module of ANSYS software. The influences of casting parameters on the distributions of temperature and stress were studied, which helped optimize the parameters (at pouring temperature of 680 °C, casting speed of 2 mm/s, heat-transfer coefficient of the second cooling equals to 5 000 W/m2·°C−1). The simulation results of thermal stress and strain fields reveal the formation mechanism of some casting defects, which is favourable for optimizing the casting parameters and obtain high quality billets. Some measures of controlling processes were taken to prevent the defects for direct-chill casting billets.
TiC-containing diamond-like carbon (TiC-DLC) nanocomposite coatings were deposited by a rectangular cathodic arc ion-plating system using C2H2 as reacting gas. Raman spectroscopy and transmission electron microscopy analysis show that with increasing flow rate of C2H2, the structure of nanocomposite coatings changes from TiC nanograin-containing to graphite nanograin-containing DLC. The hardness measurements show that the hardness decreases from 28 GPa to 18 GPa with increasing C2H2 flow rate. The scratch test show that a high critical load (>40 N) was obtained and exhibited a good adhesion between the coating and the substrate. Wear experiment shows that the friction coefficient of TiC-DLC nanocomposite coatings decreases with increasing C2H2. A low friction coefficient of 0.07 was obtained at 480 sccm C2H2.
Nano SiO2/NR composites were prepared through blending nano SiO2 emulsion with natural rubber latex and then concreting with acetic acid. The emulsion nano SiO2 was prepared with Na2SiO3·9H2O and hydrochloric acid under the reaction of the assistant agents. The was analyzed effect of the application rates of assistant agents such as silane coupling agent, surfactant, nucleating agent and dispersant on the properties and interface structure of the nano SiO2/NR composites with IR, TEM, SEM, DMA was analyzed. An orthogonal test was arranged to select optimum condition. The results show that the best combination for preparing nano SiO2/NR composites is as follows: the rate of the silane coupling agent (TESPT), the surfactant(dodecyl benzene sulfonate natrium), nucleating agent(AlCl3) and dispersant(ethylene diamine tetraacetie acid) in the course of preparing nano SiO2 are 15%, 2.0%, 2.5% and 0.4%, respectively. Several replications in the experiment had produced desirable nano SiO2 products and nano SiO2/NR composites with better properties.
The biocompatibility of silicone rubber (SR) based electrodes coating with poly (vinyl alcohol) (PVA) films after implanted in the brain of rats was investigated. Twenty-two Wistar rats were used and implanted with SR electrodes and PVA/PAA films coated electrodes in left and right cerebral cortex respectively. After 4 and 8 weeks, the expression of glial fibrillary acidic protein (GFAP, a specific marker of astrocytes) and cluster of differentiation 68 (CD68, a specific marker of macrophages) were evaluated by immunohistochemistry. After 8 weeks, GFAP and CD68 expressions around PVA electrodes were significantly lower than those around SR electrodes in every stratified area (0–50 μm, 50–100 μm, 100 μm from further up to the electrode-tissue interface). The results show that PVA coating can reduce the expressions of GFAP and CD68, suggesting the PVA coating can improve the biocompatibility of the SR while it is implanted in brain.
The precursors with NiCO3·2Ni(OH)2·2H2O, Co2(OH)2CO3, or both NiCO3·2Ni(OH)2·2H2O and Co2(OH)2CO3 coated graphite microspheres were prepared respectively by the aqueous heterogeneous precipitation using nickel sulfate, cobalt nitrate, sodium carbonate, ammonium bicarbonate and graphite microspheres as the main starting materials. Subsequently, Ni-, Co- and NiCo-coated graphite microspheres were successfully obtained by thermal reduction of the as-prepared precursors at 500 °C for 2 h, respectively. These metal-coated graphite microspheres were characterized with a smooth, cohesive surface consisting of fine metallic particles. Optimized precipitation processing parameters of the concentration of graphite microspheres (10 g/L), the rate of adding reactants (3 mL/min) and pH value (8.0) were determined by a trial and error method. The thermal analysis of the precursors was investigated by TG. Powders of the precursors and the resultant metal-(Ni, Co and NiCo alloy) coated graphite microspheres were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD).
Capacity of the silver-doped TiO2 under UV-C light to restrain cyanobacterial growth was explored with Anabaena sp. PCC 7120 and Microcystis aeruginosa as test species. The survival, chlorophyll bleaching, photosynthetic activity, DNA breakages, antioxidant enzyme activities, lipid peroxidation, and cellular morphologic structure of test cyanobacteria were analyzed. The results indicate that the test cyanobacteria with UV-C photocatalysis by silver-doped TiO2 sufferd from effects of reactive oxygen species, which promote the damage of the cell wall and the peroxidation of cell membranes, and subsequently, aggravate the losses of cell organelle and viability. The results suggest that UV-C photocatalysis by the silver ions doped TiO2 could be a promising method to prevent fast and excessive growth of cyanobacteria in eutrophic water sources.
Peripheral nerve regeneration using a novel nerve conduit (PRGD/PDLLA/β TCP/NGF) was evaluated, which was made of RGD peptide modified poly{(lactic acid)-co-[(glycolic acid)-alt-(L-lysine)]} (PRGD), poly(d,l-lactic acid) (PDLLA) and β-tricalcium phosphate (β-TCP). And the effectiveness was compared with that of PRGD/PDLLA/β-TCP, PDLLA and autograft in terms of nerve regeneration across a gap. Both of biodegradablity and cell-biocompatibility of the novel nerve conduit were evaluated in vitro. The results show that PRGD/PDLLA/β-TCP/NGF composite materials have better biodegradation properties and cell affinity than PDLLA, and could promote the RSC96 Schwann cells adhesion, proliferation and growth on the surface of materials. PRGD/PDLLA/β-TCP/NGF composite conduit was significantly superior to that of the PDLLA conduit in histological and axon morphologic index. PRGD/PDLLA/β-TCP/NGF conduit is more beneficial to nerve regeneration than PDLLA conduit. The biodegradable PDLLA/PRGD/β-TCP/NGF conduit has a good biocompatibility with rats tissue and it could effectively promote the nerve regeneration after bridging sciatic nerve defect of rats, the effect is as good as that of the autograft nerve, significantly superior to the PRGD/PDLLA/β-TCP conduit and PDLLA conduit. PDLLA/PRGD/β-TCP/NGF composite conduit is a potential ideal conduit.
The deformation resistance effect of polyacrylonitrile (PAN)-based carbon fibers was investigated, and the variatipn law of electrical resistivity under tensile stress was analyzed. The results show that the gauge factor (fractional change in resistance per unit strain) of PAN-based carbon fibers is 1.38, which is lower than that of the commonly-used resistance strain gauge. These may due to that the electrical resistivity of carbon fibers decreases under tensile stress. In addition when the carbon fibers are stretched, the change of its resistance is caused by fiber physical dimension and the change of electric resistivity, and mainly caused by the change of physical dimension. The mechanical properties of carbon fiber monofilament were also measured.
A novel process for separation of red (Y2O3: Eu3+), blue (Sr, Ca, Ba)10(PO4)6Cl2: Eu2+ and green (LaPO4: Tb3+, Ce3+) fine tricolor phosphor powders was established. First, the green phosphor was extracted and separated from three phosphor mixtures in heptane/DMF(N, N-Dimethylformamide) system using stearylamine or laurylamine (DDA) as the cationic surfactant. Then, after being treated with 99.5% ethanol, the blue and red phosphors could be separated in Heptane/DMF system in presence of 1-octanesulfonic acid sodium salt as the anionic surfactant. Satisfactory separation results have been achieved through two steps extractions with their artificial mixtures. The grades and recovery of separated products reached respectively as follows: red product was 95.3% and 90.9%, blue product was 90.0% and 95.2%, and green product was 92.2% and 91.8%.
The microstructure and mechanical properties of rapidly solidified Al-Cr alloys were investigated by XRD, TEM and microhardness testing instrument. The results indicate that the matrix of rapidly solidified Al-Cr alloys is α-Al solid solution when the Cr content is lower than 4 wt%. However, when the Cr content is above 4 wt%, the microstructures of rapidly solidified Al-Cr alloys are different along cross section. The microstructure of alloy contacting copper roller consists of α-Al and a few intermetallic compounds. With the increase of distance from copper roller, the matrix consists of α-Al and spherical intermetallic compounds which conglomerate in α-Al matrix. These intermetallic compounds are Al7Cr, Al11Cr and Al4Cr. The tensile strength has the maximal value when the Cr content is about 8 wt%. The annealed microstructures show that supersaturated α-Al solid solution dissolved with increasing anneal temperature. The starting temperature of the second phase precipitated from the supersaturated α-Al solid solution desponds on the supersaturation. Meanwhile, the microhardness of rapidly solidified Al-Cr alloy reaches maximal value after annealing at 300 °C.
Behaviour of hardening and serration yield of a Fe-Ni-Cr alloy under isothermal cycling (ISC) and out-phase TMF was studied on the basis of varied hysteresis loops. Cycling hardening and serrated yielding for ISC depend on the temperature and the total strain range, stronger hardening with serrated yielding at higher strain range under ISC at 600 °C, but no hardening and serrated yielding occurred under ISC at 800 °C. Stronger hardening with stress serration occurred at the thermal path going to the lowest temperature, no stress serration occurred at the highest temperature under the out-phase. The hardening also depends on the total strain range, higher total strain range with lower cycling temperature resulted in a stronger hardening and remarkable serration yielding behavior. Weaker hardening without serrated yielding occurred at near 800 °C may due to an obvious cycling stress drop under out-phase TMF. Change in the shape of the hysteresis loops also expresses the degree of the damage of the tested alloy under out-phase and ISC.
Effects of the main process parameters(temperature and time) on microstructure and properties of Ti(C, N)/Ni interface bonded by (Cu+Nb) interlayer in a vacuum diffusion bonding device were investigated. The interfacial microstructures consisted initially of Ni3Nb metallic compound and eutectic of Ni3Nb+CuNiSS, and finally transformed to (Ti, Nb) (C, N)+Ni3Nb near Ti (C, N) and NiCuSS+Ni3Nb near Ni when diffusion bonding temperature was 1 523–1 573 K. It was clear that Cu was a constituent in the transient liquid phase (TLP) into which Ni was dissolved by forming Cu-Ni transition liquid. Nb was dissolved in Cu-Ni transition liquid rapidly. Ti (C, N) conld be wetted by resultant Ni-Nb-Cu transient liquid phase which was followed by a little (Ti, Nb) (C, N) solid solution formed at interface. This increased the interface combining capability. Ultimately the interface shear strength was able to reach 140 MPa. The theoretle analysis and experimental results show that the growth of interfacial reaction layer Ni3Nb accords with parabola law, and the activation energy of diffusion reaction is 115.0±0.5 kJ/mol, while the diffusion reaction speed constant is 12.53 mm/s1/2.
The experimental creep data were focused on wood-flour (WF) /poly vinyl chloride (PVC) composites with the variations in additive concentrations of wood flour, silane coupling agent, organomodified montmorillonite (OMMT) and nano-cacium carbonate (nano-CaCO3). Their effects were analyzed using the Four-element Burger Model incorporating microscopic mechanisms. Total creep strain was low with increasing WF while elastic strain was high and plastic flow strain was low in modeling. Modification of WF with silane was beneficial to creep resistance, so did adding low ratio of OMMT (1.5 wt%) and nano-CaCO3 in composites. Thus, it was effective in reducing creep either by stiffening the PVC matrix using rigid nano-particles or by improving their adhesion with resin. However, superfluous quantity of any additament did not benefit the improvement owing to either earlier destruction of their agglomerates or stress-concentrated cracks in the over-incrassated interface.
PST ferroelectric ceramics were fabricated successfully by a two-step method, i e first, PbTiO3 and SrTiO3 were sintered respectively, then mixed and sintered together. The process and characteristics of PST ferroelectric ceramics were introduced and researched. Their dielectric and pyroelectric characteristics are as follows dielectric constant 104 order, low dielectric loss (lower than 3.0% in the working frequency range of 1–1 000 kHz), saturation polarization intensity 10−1 C/m2 order, and pyroelectric coefficient 10−3 C/m2·K order.
In order to make an effectivily recycle use of iron and steel slags that are main industrial wastes generated in Chinese metallurgical industry, the current technologies for reprocessing and recycling these wastes into eco-building materials were reviewed, such as preparing cement-steel slag blended cement with steel slag after metal recovery, using the fine powder of blast furnace slag (BFS) for manufacturing slag cement and high performance concrete. A further research on using these available resources more efficiently were discussed.
Formation and coexistence of tricalcium silicate (C3S) and calcium sulphoaluminate (C4A3$\bar S$) minerals in Portland cement clinker containing calcium sulphoaluminate were investigated. The f-CaO content, mineral composite and formation of mineral in the clinker were analyzed respectively by chemical analysis, differential scanning calorimetry(DSC) and X-ray diffraction. The results show that, adding a suitable amount of BaO can improve the burnability of raw meal and promote the f-CaO absorption. Tricalcium silicate and calcium sulphoaluminate minerals can form and coexist in clinkers at 1 234–1 317 °C by the addition of BaO to the raw meal. A suitable amount of BaO expanded the coexistence temperature of two minerals by 58 °.
The curing process of epoxy asphalt was analyzed by Fourier transform infrared (FT-IR) spectroscopy. Effect of curing temperature on viscosity of epoxy asphalt, and changes of mechanical properties with curing time were investigated. The evolution of concentration of epoxy band was followed as a function of the applied curing process. The experimental results indicate that the curing reaction rate of epoxy asphalt is invariable before 70 min at 120 °C, and it decreases when curing time exceeds 70 min. The viscosity of epoxy asphalt increases slowly with curing time at initial curing stage. But it increases quickly after initial curing stage and the initial curing time decreases as the curing temperature increases. The tensile strength increases slowly at incipient curing stage and increases rapidly when curing time is form 20 min to 70 min. The elongation at break shows a decrease with curing time, but it exceeds 200% after cured.
The normal asphalt index test, DSR test, FTIR and the GPC distribution analysis of molecular weight on the extraction and recovery of asphalt of the gussasphalt, SMA extraction and recovery of asphalt and the rotary-thin-film-oven-aged asphalt above 240 °C were introduced. The results indicate the rutting factor and fatigue factor of the extraction and recovery of asphalt of the gussasphalt are greatly improved, and an obvious absorption peak of carbonyl and a further decrease of the SBS molecular weight of the gussasphalt are found.
A new type of cement was prepared with ground limestone powder, blastfurnace slag, steel slag and gypsum without calcination. The fraction of ground limestone powder in the cement was as high as 40 wt%–60 wt% without Portland clinker. All of its physical properties can meet the requirements of masonry cement standards. The impact of limestone content on physical properties of the cement and determined its impact on law was investigated. The steel slag can excit the aquation activity of this cement effectively, and the influence of its quantity on the strength of the materials was studied, which shows that the optimum quantity of mixing is 10%. By way of changing the different content of the lime stone by quartzy sample, the law of the compression strength and the PH value was determined, confirming that the lime stone can promote the early aquation of the slag and improve the early strength. The main hydration product of this cement is calcium aluminate hydrate, ettringite and calcium silicate hydrate, as indicated by XRD and SEM analysis.
Formation, solution and phase change of hydration products in MgO-MgCl2-H2O system was studied with thermodynamics method, and resistance to water immersion and phase change of magnesium oxychloride cement with different MgO/MgCl2 molar ratio was experimented. The results show that pH value of immersion solution of cement paste has a remarkable influence on phase stability of hydration products. A higher pH value leads to a lower solubility and a better phase stability of hydration products. When the solution pH value is higher than 10.37, the precipitation of much Mg(OH)2 crystal induces a worse phase stability of hydration products. With the increasing MgO/MgCl2 molar ratio (lower than 6), the more amount of MgO in the hydration products enhances the alkalinity of solution and the phase stability is improved. However, when the MgO/MgCl2 molar ratio is higher than 6 and the excessive MgO exsits in the hydration products, the cement paste may be damaged by the excessive crystallization stress of a great deal of Mg(OH)2 formation.
Utilizing pre-cast ECC panels as participating permanent formwork of concrete members, and the validity of using ECC to disperse the single crack in concrete into multiple ones in ECC were studied. In the process, totally two kinds of ECC with different tensile properties, 7 series of flat panels with different top surface figures and 3 U-shape panels with different inner surface forms were investigated. To evaluate the performance of the permanent formworks, small ECC-concrete composite beams were cast and tested mechanically. The 4-point bending test results show that the use of pre-cast ECC panels as permanent formwork can significantly improve the load capacity and toughness of a concrete member, effectively dispersing single widely opened crack in concrete into multiple ones in ECC. Most permanent formworks show perfect bond with the concrete cast on them, while the ones with partially debonded zone achieve the best mechanical performance. The U-shape permanent formworks show better performances than the flat ones, achieving much better improvements in both the load capacity and toughness, together with better crack width control.
The pozzolanic reactivity was determined by the hydration kinetics of pozzolanic reaction based on the fact that the hydration products of active SiO2 and Al2O3 with lime were soluble in dilute hydrochloric acid. The results show that the pozzolanic reaction of active SiO2 and Al2O3 of coal ashes follows apparent first-order kinetics. The reaction rate constant of FBC ashes is greater than that of PC ashes, while the activation energy of the former is lower than that of the latter. It is confirmed that the pozzolanic activity of fluidized bed combustion(FBC) ashes is significantly higher than that of PC ashes, and the reaction barrier of the former is lower than that of the latter, because the microstructures of FBC ashes, such as mineralogical composition, morphology and polymerization degree of [SiO4] and [AlO6] are more favorable to the pozzolanic activity development than those of PC ashes.
The setting reaction of glass ionomer cement was studied by analyzing and comparing the short-tem mechanical properties of set cement stored in silicone oil, air and distilled water respectively at different temperatures. For the set cement stored at 37 °C, the strength of the sample in the air reached the maximum value after 24 h, then decreased to about 210 MPa and kept steady. The strength of the sample in water increased continuously and slowly, however, the increasing rate of sample stored in silicone oil was higher than that in the water. At 20 °C, the increasing rate of compressive strength for sample in air was higher than those in silicone oil and water. The diffusion speed and maintenance of water has significant effects on the mechanical properties of glass ionomer cements.
The influences of compositing mineral admixtures on the regularity of mechanical property, workability, durability and microstructure of C50 marine concrete were investigated. The results show that the incorporation of mineral admixtures can improve the mechanical properties and workability of C50 marine concrete, 3 min-doped mineral admixture had excellent resistance to chloride ion permeability. The microscopic structure mixing mineral admixtures system was well-distributed and compact, little macroporeare can be found.
Radiation-shielding concrete was made with ironstone aggregate. The compressive strength is affected by multi factors. The electrical conductive properties and smart performance was discovered and investigated. Experimental results show that concrete conductivity rapidly declines with increasing loading, and the conductivity is much lower than the initial value of conductive aggregate of concrete, which may be related to special characters of ironstone. This kind of concrete has widely potential applications due to its special characters and low cost.
Durability of traditional reactive powder concrete (RPC) with rich cement and high volume of fly-ash reactive powder concrete (FRPC) were studied. The X-diffraction and scanning electron microscope (SEM) measurement was imployed to analyze the microstructure. The results show that both types of RPC have higher compressive strength, less volume shrinkage ratio and better carbonation-, chloride-, freezing-resistances than the conventional concrete. The results of X-diffraction indicate that they basically have C-S-H as the main composition without Ca(OH)2 crystal and ettringite. SEM results show that hydration products of FRPC is mainly III-C-S-H which is piled up closely like densely arranged stone body and it has very compacted structure, in addition, Ca/Si ratio of C-S-H gel is lower than 1.5.
Due to its low water content, it is difficult for expansive agent to have an effective expansive effect on high strength concrete to compensate its extensive shrinkage and form a certain expansion. To solve this problem, water-releasing material with water storage and releasing characteristics was incorporated into high strength micro-expansive concrete to provide internal curing, and expansive effect of expansive agent was improved. Migration of water from initially saturated water-releasing material to the surrounding hydrating cement paste was investigated. Based on a given efficient diffusion distance of water stored in water-releasing material, the mass and real water-cement ratio of cured cement paste were estimated. At the same time, the effect of internal curing of water-releasing material on the volume deformation of high strength micro-expansive concrete was investigated.