A pilot study was conducted to produce high performance green ceramsite by using sewage sludge, fly ash and silt. According to the theory of Riley, the proportions of raw materials were chosen to perform the sintering...A pilot study was conducted to produce high performance green ceramsite by using sewage sludge, fly ash and silt. According to the theory of Riley, the proportions of raw materials were chosen to perform the sintering experiments. Thereby, the optimum proportion of sludge, fly ash and silt and sintering parameters were determined. The microstructure of the optimized mixture and the leaching of heavy metal elements were also analyzed. The lab testing results show that sintering parameters have significant impact on the performance of ceramsite. For solid waste ceramsite with high loss of ignition, inadequate pre-burning process lowers the strength and increases the water absorption. Low water absorption can be achieved by the enameled surface and closed pore structure. The high performance green ceramsite has the density grade of 700, water absorption of 6% and compressive strength of 6.6 MPa. The ceramsite is mainly composed of cristobalite and mullite. The leaching of heavy metal elements from the solid waste ceramsite are lower than the limits required by the national standard. This study shows that the utilization of solid waste ceramsite as the light Weight aggregate is feasible and safe.展开更多
In order to investigate the effects of carbonation on the microstructure of cement concrete,the carbonation depth and microstructure of cement paste with 0.3,0.4 and 0.5 water/cement ratio after 7,14,21 and 28 d accel...In order to investigate the effects of carbonation on the microstructure of cement concrete,the carbonation depth and microstructure of cement paste with 0.3,0.4 and 0.5 water/cement ratio after 7,14,21 and 28 d accelerated carbonation were studied respectively.The results showed that with the increase of waterto-cement ratio and carbonation age,the carbonation depth was deepened with faster early carbonation speed and slower later carbonation rate.Carbonation densified the structure of hardened cement stone with refinement of pore structure and reduced porosity.Then,during the carbonation process from the surface to the inside of carbonation area,it was prone to form micro-cracks extending to the interior specimen,resulting in cement paste carbonation depth uneven.It is further illustrated that the color reaction method using phenolphthalein solution combined with X-CT and X-ray diffraction analysis is much more reasonable to evaluate the cement concrete carbonation degree.Moreover,during carbonation process sulfur element in cement paste migrated to the area un-carbonated and the concentrated shape of sulfur element is consistent with the coloring region in carbonation interface.Finally it was identified that carbonation not only reduced the p H value in cement concrete but also made prone to crack in carbonation zone,which increased the probability of reinforcement corrosion.展开更多
基金the National Natural Science Foundation of China (No.51078189)the K.C.Wong Magna Fund in Ningbo University and Zhejiang Province Energy Conservation Innovative Team Project in Building (No.2009R50022)
文摘A pilot study was conducted to produce high performance green ceramsite by using sewage sludge, fly ash and silt. According to the theory of Riley, the proportions of raw materials were chosen to perform the sintering experiments. Thereby, the optimum proportion of sludge, fly ash and silt and sintering parameters were determined. The microstructure of the optimized mixture and the leaching of heavy metal elements were also analyzed. The lab testing results show that sintering parameters have significant impact on the performance of ceramsite. For solid waste ceramsite with high loss of ignition, inadequate pre-burning process lowers the strength and increases the water absorption. Low water absorption can be achieved by the enameled surface and closed pore structure. The high performance green ceramsite has the density grade of 700, water absorption of 6% and compressive strength of 6.6 MPa. The ceramsite is mainly composed of cristobalite and mullite. The leaching of heavy metal elements from the solid waste ceramsite are lower than the limits required by the national standard. This study shows that the utilization of solid waste ceramsite as the light Weight aggregate is feasible and safe.
基金Funded by K.C.Wong Magna Fund in Ningbo Universitythe National Natural Science Foundation of China(Nos.51278255,51478227)Ningbo Municipal Science and Technology Project(Nos.2013C51006,2015A610300)
文摘In order to investigate the effects of carbonation on the microstructure of cement concrete,the carbonation depth and microstructure of cement paste with 0.3,0.4 and 0.5 water/cement ratio after 7,14,21 and 28 d accelerated carbonation were studied respectively.The results showed that with the increase of waterto-cement ratio and carbonation age,the carbonation depth was deepened with faster early carbonation speed and slower later carbonation rate.Carbonation densified the structure of hardened cement stone with refinement of pore structure and reduced porosity.Then,during the carbonation process from the surface to the inside of carbonation area,it was prone to form micro-cracks extending to the interior specimen,resulting in cement paste carbonation depth uneven.It is further illustrated that the color reaction method using phenolphthalein solution combined with X-CT and X-ray diffraction analysis is much more reasonable to evaluate the cement concrete carbonation degree.Moreover,during carbonation process sulfur element in cement paste migrated to the area un-carbonated and the concentrated shape of sulfur element is consistent with the coloring region in carbonation interface.Finally it was identified that carbonation not only reduced the p H value in cement concrete but also made prone to crack in carbonation zone,which increased the probability of reinforcement corrosion.
