Papers by Author: Zi Ming Wang

Abstract: A novel polycarboxylate superplasticizer (PCE) with energy saving preparation was elaborately designed and synthesized by using acrylic acid (AA), hydroxypropyl acrylate (HPA) and isopentenyl polyethylene glycol (IPEG) as monomers. To investigate the effects of the preparation method on the effectiveness of PCE, the PCEs were prepared from energy-saving method and common method respectively, and the hydration heat evolutions of the cement pastes containing these PCEs were comparatively probed. Furthermore, the working mechanisms of the PCEs by different preparations were identified via adsorption behavior, adsorption kinetic and Zeta potential of the PCE on cement surfaces. The results showed that, this novel PCE prepared in an energy saving manner can significantly prolong the hydration process and present a stronger adsorption capacity. In addition, the adsorption of this PCE on cement surface exhibited a characteristic of pseudo first order kinetic equation model. The evaluation in energy conservation showed that, this energy saving preparation can save 1.548×10⁴ kJ per 10 ton production. The aim of this study is to provide a new avenue to synthesize a PCE with economical method which achieves energy-saving preparation. Due to the indispensable application in construction industry, the innovations from this study contribute to the low energy-consumption production and high eco-effectiveness of the novel PCE, which has potential applications in low-emission building materials.

Abstract: 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%f_max, 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.

Abstract: 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.

Abstract: The hydration of cement is known to be a complex phenomenon. Although the broad pattern of reactions and microstructural development are known, a number of important questions remain unanswered. How to select the proper techniques is what the research people think of for now. This paper reviewed the domestic and international research progress and presented the advantages and disadvantages of these methods and the application prospects. Nuclear magnetic resonance spectroscopy (NMR), nanoindentation and electron microscopy techniques of cements were expounded in detail. Furthermore, through analyzing the results obtained by different research methods, the paper predicted the development prospect of advanced testing method of cement-based materials.

Abstract: Analyzed and calculated the energy savings of heat reflective coatings applied on multi-storied residential buildings and high-risen commercial buildings in Beijing. Some advices about the application of heat reflective coatings in northern cold region are given. Energy saving effect was evaluated with the building energy simulation in winter and summer while the heat reflective coating is applied on the surface of residential buildings and commercial buildings. Calculating results showed that the energy saving is the most optimal to the multi-storied buildings when the cool roof coatings is coated on the roofs and the glass heat reflective coating is applied on east and west windows. With the high-risen commercial building, the energy saving is noticeable when the glass curtain wall is coated with glass heat reflective coatings. The energy saving rate can reach a maximum of 13%.

Abstract: To discuss the effect of energy saving of heat-reflective coating on building, the heat gain of exterior building envelope in summer and winter in Beijing has been calculated. The results indicated that the higher the reflectivity of coating, the better the energy saving effect. The energy consumption of roof and different direction walls were analyzed. The energy saving effect on roof is the best, however the effect is not obvious on the east and west walls. The heat reflective coating has no effect on north wall but exhibits effect on south wall. The energy saving effect of brick red heat-reflective coating is not obvious compared with the common brick red coating.

Abstract: Polycarboxylate superplasticizer (PCE) was synthesized in non-aqueous system to achieve the rapid transportation and convenient preparation. The results showed that, PCE using isopentenyl polyethylene glycol (TPEG) or isobutenyl polyethylene glycol (IPEG) as macromonomer exhibited excellent paste fluidities and retaining properties at 80°C and 75°C, respectively. Fourier Transform infrared spectroscopy (FTIR) measurement confirmed the polymerization between monomers. The synthesized PCE as solid state was dissolved into water to prepare the PCE solution, and its cement application performances were studied systematically. The results showed that PCEs with good paste fluidity retentions exhibited the longest final setting time and the shortest setting time interval. The hydration heat results showed that PCEs with good fluidity properties can significantly delay the hydration process and lower the hydration heat.

Abstract: Polycarboxylate superplasticizer (PCE) was usually sensitive to clay in mortar or concrete. The flow properties of cement pastes and mortars for PCEs with either kaolin or bentonite were studied systematically. The results showed that bentonite had a stronger influence on PCEs performance than kaolin, even no fluidity when bentonite dosage was more than 2%. The adsorption amount of bentonite on PCE was about 5-10 times more than that of kaolin, and PCEs adsorption on clay was proportional to its sensitivity to clay. The influencing mechanism of clay on PCE was analyzed from the structures of kaolin and bentonite and their adsorption characteristics between interlayer. The result of exploring control measure showed that adding the synthesized pre-adsorbent can effectively inhibit the effect of clay on PCE and ensure its workability.

Abstract: The shrinkage-reducing type polycarboxylate superplasticizer (SRPCA) has become a hot research issue both at home and abroad for its perfect water-reducing ability, outstanding shrinkage-reducing and slump retaining ability. The effect of ordinary polycarboxylate superplasticizer (PCA) and shrinkage-reducing PCA on the drying shrinkage of cement mortar was studied thoroughly in this paper. The result showed that the SRPCA can effectively reduce the drying shrinkage of cement mortar. Moreover, the shrinkage-reducing mechanism was discussed from the aspect of molecular structure to the solution surface tension and also mortar water retention. It indicated that the solution surface tension had certain impact on the PCA shrinking-reducing ability, meanwhile the perfect water-retaining ability conduce to the shrinking-reducing improvement. esides, the introduction of shrinking-reducing functional groups to the ordinary PCE molecular structure can reduce the polymer solution surface tension, control the air content in the concrete and decrease the drying shrinkage of cement-based materials.

Abstract: The dispersing effect of superplasticizer is closely related to its adsorption behaviors on the surface of cement particles or the hydrates. But the relationship between the adsorption amount of superplasticizer and the fluidity of cement paste seems uncertain. To investigate the relationship between the adsorption amount and the fluidity of cement paste, three groups of cements with designed compositions and C3A mineral were prepared in lab. Four types of superplasticizer were used to measure the adsorption on various cements. The corresponding zeta potential of cement particles with superplasticzers and the fluidity of cement pastes were tested and analyzed. It was found that the adsorption amount of superplasticizer was inversely related to the fluidity of cement paste for a given superplasticizer. The zeta potential of cement particles in the paste was proportional to the adsorption amount of superplasticizer. The adsorption amount of different superplasticizers at the isoelectric point in C3A-H2O system was determined. The meaning of the “adsorption amount” was discussed. The author proposed that the superplasticizer in cement paste should include three parts, and the role of each part was discussed according to test results and analysis.