Zi Ming Wang

Preparation of Sulfonated Cyclohexanone-Formaldehyde Resin

Sulfonated cyclohexanone-formaldehyde resin (SCF) was synthesized using cyclohexanone and formaldehyde as raw materials, sodium sulfite as sulfonating agent. The composition of the SCF resin was characterized by FTIR and 13C NMR, and the possible mechanism for formation of the resin was suggested. The effects of reaction parameters, such as ratio of formaldehyde and cyclohexanone, the amount of sulfonating agent, as well as reaction temperature and pH, on the viscosity and average molecular weight were investigated. The results showed that the optimum reaction conditions was that the ratio of reactant was n (formaldehyde):n (cyclohexanone):n (sodium sulfite) = 2.0:1.0:0.7, and pH value of the system was 10 at 90°C temperature. The average molecular weight of the resulted resin was 58392.

The Performance and Application of Cement-Based Grout Material with High Hour Strength

The cement-based grout material with very high hour strength and good self-leveling ability was developed to meet the needs of urgent engineering r epairing or rapid consolidation work. The grout material has the properties of good fluidity, high hour s trength and high final strength, shrinkage compensating ability, short time gap between ini tial setting and final setting and better durability compared to organic grout material. The influence o f environment temperature on the properties of the cement based grout material was also exam in d and discussed. By means of XRD analysis, the mechanism of high hour strength was discussed. The cem nt based grout material has been successfully used in several urgent reinforci ng projects of railway substrate, as well as some waterproof engineering under severe natural environment. Introduction In many cases the repairing and consolidation of old concrete struct ures must be carried out while not affecting their routine service. Road and airport runway, bridge, railway tunnel and railway substrate are usually required to be repaired while in use, so repair work must be finished in the short interval of service and strength should gain quickly enough to wit hstand the load. The railway substrate in the 14 km long Dayao Mountain Tunnel in Jingguang line, the long st tunnel in Asia, was severely damaged and hollow down. The speed of the trains were s trictly limited to below 60 km/h when trains passed through the tunnel. But to repair the railway s ubstrate faced a lot of limitations. Jingguang line is the busiest railway line of China, over 90 trains running on this line everyday, and the longest interval between the consecutive two trains is 70 minutes. So the grout operation must be finished in 30 minutes and the strength of the grout m aterial must reach as high as 8MPa in the next 30~40 minutes, and the strength at 28 day should not bel ow 50MPa[1]. Furthermore the grout material should possess some anti-washout abi lity and good groutability as well as be environmental friendly, for the construction site wa s h lf sealed. So on the basis of systematic survey, a cement-based grout material with high hour strength and good self-levelling ability was proposed to meet the needs of urgent repairing work i n railway substrate engineering and rapid consolidation work.

Mechanical Properties of Self-Healing System in Cementitious Material with Microcapsule

In this paper, several urea–formaldehyde/epoxy microcapsules with different particle sizes were synthesized by in-situ polymerization. The chemical structure and compressive rupture load of microcapsule were characterized. The effect of microcapsule dosage, particle size and preload pressure on compressive strength of cementitious materials was studied. The result shows: when the particle size of microcapsule is 2 mm~2.5 mm, the rupture load of microcapsule is highest, more than 3N; When the microcapsule dosage is less than 2.5%, the strength loss of the matrix is relatively small; With the increase of the particle size of the capsule, the strength of the matrix decrease greatly; When the dosage of microcapsule is 2.5%, the particle size is 1.5 mm and the preload pressure is 30%~45%fmax, the compressive strength of the self-healing specimen is 8% higher than that of the non-preloaded specimens, which shows a certain self-healing performance.

Effect and Mechanism of Sodium Fluosilicate on Setting Time of Cement

Sodium fluosilicate (Na2SiF6) is prepared from by-product of phosphate fertilizer production. According to a certain percentage of Na2SiF6 mixed in the cement, the influence of different dosages on the setting time of cement under different water-cement ratio was discussed, and the effect of different forms of fluoride compounds on the setting time of cement were compared. The effect and mechanism of sodium fluosilicate on the hydration products of cement were researched by using the X-ray diffraction analysis and micro electron microscope. Experimental results show that the retarding effect of sodium fluosilicate on the coagulation time had a critical effect, and beyond a certain value, it sharply decreased the setting time. The critical dosage increased with the increase of water-cecment ratio. Compared with the retarding effect of Na2SiF6、MgSiF6、NaF and CaF2 on the coagulation time of cement, Na2SiF6 was the best. The incorporation of Na2SiF6 does not change the types of the hydration products, the main function of FN is hydrolyzed with Ca2+ ions to form CaF2 with a very low solubility.

Putting Cement to Sleep with Sucrose and Waking it up with Ca(OH) 2

In this work, the effects of sucrose on setting time, heat of hydration and hydration products were studied, and the corresponding hydration process and regulation mechanism were discussed. With the adsorption test of sucrose on Ca (OH)2 suspensions, the “wake up” mechanism of Ca (OH)2 on sucrose-retarded cement was discussed. The results indicate that sucrose is used as retarder to increase the dormant period by adsorption to the cement surface, but there exists a critical amount of sucrose. And the XRD patterns indicate that sucrose can accelerate the reaction of C3A and the formation of AFt, but restraint the hydration of C3S. Ca (OH)2 that was used as accelerator in this paper can adsorb the sucrose up to 6.2mg sucrose/g Ca (OH)2. The combined-use of sucrose and Ca (OH)2 does not change the shape of the heat rate curves significantly. And the dormant period of sucrose-retarded cement can be decreased with the doses of Ca (OH)2 increasing, because of its high surface and preferential adsorption of sucrose.

Microstructure and Properties of C-S-H/PCE Nanocomposites

Different dosage of TPEG-polycarboxylate (PCE) copolymers were used to prepare the calcium-silicate hydrated (C-S-H)/PCE nanocomposites by precipitating C-S-H from Na2SiO3·9H2O and Ca (NO3)2·4H2O in the PCE solution. The composition and structure of the prepared C-S-H/PCE nanocomposites were characterized by XRD, SEM, FTIR methods, and the early strength of mortars was measured. The results show that structural investigation of the C-S-H/PCE nanocomposites via X-ray diffraction revealed a semi-crystalline composition, and the PCE polymers were adhered the surface of C-S-H particles in the composite. The preparation of C-S-H /PCE nanocomposites enhanced markedly the early strength of mortar, and when the dosage of PCE copolymers was up to 30%, the early strength enhancing effect was the highest, the early flexural strength increased up to 100%, and early compressive strength increased up to 120%. Therefore, C-S-H /PCE nanocomposites can improve the early strength of mortar effectively since it can lower the barrier of nucleation of the products, promote the nucleation and inhibit the growth of large grains effectively.

Hardening Performance and Mechanism of Fluosilicate Surface Treatment Agent on Cement-Based Materials

Based on the theory of ecological resources recycling, the effects of matrix quality, surface treatment method, soaking time, age after treatment and fluosilicate cation on hardening cement based materials were investigated by using the byproduct of phosphate fertilizer production namely fluosilicate as the surface treatment agent of cement-based materials and changing different surface treatments. The results showed that the permeation capacity of surface hardener solution , the wear resistance and surface hardness of cement-based materials were significantly improved by the treatments of surface sanding and oven drying. Both surface spraying and submerging methods can promptly increase the hardening effect by more than 20%, manifesting as the rapid improvement of wear resistance in 1 day and the maintenance of that in 7 days. The effective spraying amount and soaking time were 100g/m2-200g/m2 and 6 h, respectively. The fluosilicate surface hardener exhibited better hardening effect than the silicate surface hardener for those matrix materials with different quality, especially for the matrix materials with low compactness. The magnesium fluosilicate displayed the best hardening effect. Besides, the mechanism of fluosilicate and silicate surface hardeners were discussed and compared. The results show that the fluosilicate surface hardener produced crystals and colloids by reacting with cement hydrates to fill the void and improve the compactness, other than the silicate surface hardener which produced calcium silicates by reacting with cement hydrates. As a result, the hardness and wear resistance of cement-based materials are improved, but also the probability of a potential alkali-aggregate reaction is substantially reduced.

Preparation and Properties of Heat-Dissipation Coating Filled with Carbon-Based Filler

Aiming at the heat dissipation of equipment, and based on ANSYS finite element simulation of thermal conductivity of coatings, the heat-dissipation coating filled with graphite and carbon nanotubes respectively, which integrates heat conduction (high thermal conductivity) and radiation (high emissivity), was successfully prepared by the method of solution mixing. Meanwhile, the effects of filler content, type and shape on thermal conductivity and emissivity of the coating were also investigated. The results indicate that the rising tendency between the simulated data by FEM and experimental value is consistent, which has a certain directive significance. In addition, graphite can improve the thermal conductivity and emissivity of the coating effectively; however, the emissivity decreases when the content exceeds 23.08%. The carbon nanotubes can improve the thermal conductivity and emissivity simultaneously, the thermal conductivity is 2.3 times that of pure resin, and the emissivity is up to 0.91 at the 2.0% mass fraction of carbon nanotubes.

Solar Reflection Characteristics of Phthalocyanine Green/TiO2 Composite Green Pigments Prepared via Different Approaches

Near-infrared pigment is the key to control the near-infrared performance of solar heat-reflective coating which has good economic and application prospects as a new special coating. Green infrared reflective pigments were prepared through physical mixing, inorganic lake method and sol-gel processes in this study. Results show that the near-infrared spectral reflectance of composite pigments is improved when using inorganic lake method and sol-gel method. Chromaticity of composite pigment is the closest to phthalocyanine green when using sol-gel method. Physically mixing method is not suitable to prepare infrared reflective pigment. The coating materials have influence on the coating effect and the reflectivity of near-infrared spectral range in a certain extent.

Synthesis of High Performance Polycarboxylate Superplasticizer through Redox Initiation System and its Application in Concrete

A high performance polycarboxylate superplasticizer (PCE) was successfully synthesized by a polymerization reaction among acrylic acid (AA), maleic anhydride (MA) and isopentenyl polyethylene glycol (IPEG) through redox initiation system. The composition and amounts of initiation system, and the ratio of monomers were investigated respectively. The proportion of IPGE: MA: AA: sodium methallyl sulfonate (SMAS): ammonium persulfate (APS): ascorbic acid (ASA) was determined as 1: 3: 1.5: 0.3: 0.015: 0.012. Moreover, the effect of polymerization temperature on PCE’s cement paste fluidity was studied. The results showed that the cement pastes mixed with PCE synthesized at 10°C, 20°C and 30°C respectively exhibited better fluidity performances than that mixed with common PCE. The Fourier Transform Infrared Spectroscopy (FTIR) measurements were used for the structural characterization. The results confirmed the occurrence of polymerization reaction and the ideal structure. Furthermore, the application performances of PCE synthesized through redox initiation system in mortar and concrete were tested. The results showed that the water reducing rate of PCE in mortar and the slump performances of PCE in concrete were better than those of the common commercial PCEs. This synthesis method presents the great research value and application prospect for the PCE preparation in concrete engineering.