Papers by Author: Tao Meng

Abstract: The work described in this document forces on composite strengthening technique of recycled aggregate. In this experiment, recycled aggregates are soaked in different types and different concentrations of nanomaterials to strengthen. This research estimates the strengthening effects by comparing the properties of recycled aggregate soaked in different materials, and proves that the composite proportioning has better effect.

Abstract: In this paper, effects of nano-CaCO3 on compressive strength and Microstructure of high strength concrete in standard curing temperature(21±1°C) and low curing temperature(6.5±1°C) was studied. In order to improve the early strength of the concrete in low temperature, the early strength agent calcium nitrite was added into. Test results indicated that 0.5% dosage of nano-CaCO3 could inhibit the effect of calcium nitrite as early strength agent, but 1% and 2% dosage of nano-CaCO3 could improve the strength of the concrete by 13% and 18% in standard curing temperature and by 17% and 14% in low curing temperature at the age of 3days. According to the XRD spectrum, with the dosage up to 1% to 2%, nano-CaCO3 can change the orientation index significantly, leading to the improvement of strength of concrete both in standard curing temperature and low curing temperature.

Abstract: The flow ability, mechanical properties and microstructure of concrete with different strength grades affected by nano-SiO₂ and nano-CaCO₃ was studied. The experiment results showed that the strength of concrete at early age was increased by adding the nano-materials if the strength grade of concrete was not high. But the strength at the age of 28 days was not affected a lot by adding these nano-materials. On the other hand, it was not useful to the strength if the strength grade of concrete was high.

Abstract: The photo-catalytic efficiency and durability of nano-TiO2 photo-catalytic cementitious materials for oxidizing nitrogen dioxide were investigated under simulated sunlight irradiation. The experimental results showed that the photo-catalytic efficiency increased with increase of the content of nano-TiO2. When 15wt% nano-TiO2 was added, the photo-catalytic efficiency was equal to 223% of that of standard cement. When activated carbon was used as the carrier of nano-TiO2, the photo-catalytic efficiency of cementitious nano-TiO2 could be enhanced markedly. For example, the photo-catalytic efficiency could reach to 85.7%, which was as much as 359% of that of standard cement when the contents of activated carbon and nano-TiO2 were both 10wt%. Compared with nano-TiO2 powder, the photo-catalysis durability of cementitious nano-TiO2 supported by activated carbon could be improved clearly for that activated carbon could absorb nitrogen dioxide effectively, which was favored to the photo-oxidation of nano-TiO2 on nitrogen dioxide.

Abstract: Some long-term properties such as anti-carbonation properties, shrinkage, penetrability of chloride ion of fly ash concrete with nano-CaCO3 middle slurry were studied. Test results showed that the properties of anti-carbonation and impenetrability for chloride of fly ash concrete increased by adding nano-CaCO3 middle slurry because the tiny hole was filled by nano-CaCO3 and the density of concrete increased. But at the same time, the shrinkage of fly ash concrete with and without nano-CaCO3 was the same. Results of SEM also implied the hydration degree of fly ash could be increased by nano-CaCO3.

Abstract: Based on designed and manufactured test equipment of concrete early age shrinkage, the influence of shrinkage reduce agent (SRA) on early age autogenous shrinkage of concrete was researched. The test results show that early age autogenous shrinkage of concrete was reduced with SRA added and the shrinkage-reducing ratio increased with concrete strength grade heightened. SRA could also greatly reduce early age autogenous shrinkage of concrete added with pulverized ly ash or slag. Superplasticizer would increse early age autogenous shrinkage of concrete, and the shrinkage was larger than those without superplasticizer, even the SRA mixed into. Furthermore, early age curing should be enhanced for concrete with superplasticizer.