Experimental Research On Chemical And Autogenous Shrinkages Of Cement Paste Added With Nano-particles

With the development of nanotechnology,the nano-scale components have been introduced into cementitious materials,and it promotes the development rapid of technology of composite cement-based materials.Scholars at domestic and foreign have gained fruitful research results of the nano composite of concrete on durability,functionality,microstructure,but research on its early shrinkage has been rarely reported in the literature.Although the chemical shrinkage and autogenous shrinkage of cement paste have been researched for nearly 70 years,it rarely involved the early shrinkage of cement-based material with nano-particles added,and the existing research methods remains to be improved.This master thesis preferably selected three minerals nano-particles?Nano-SiO₂?Nano-CaCO₃?Nano-TiO₂?and three mineral admixtures?Silica Fume?Fly Ash?Meta-Kaolin?,referring to the standard of ASTM C1608?Volume method?and ASTM C1698?Corrugated pipe method?.It developed and improved the measurement system of chemical shrinkage and autogenous shrinkage of cement paste,studied the chemical and autogenous shrinkages of cement composite paste with nano-particles added,mineral admixtures added,double or various nano-particles and mineral admixtures.Meanwhile,the influence factors of water-binder ratio and curing temperature were discussed.The research findings are as follows:1.In a certain dosage range,both chemical shrinkage and autogenous shrinkage of cement paste are significantly increased by increasing replacement ratio of nano-particles.The smaller the particle size of Nano-SiO₂,the larger the chemical and autogenous shrinkages of cement paste.The chemical shrinkage of cement paste is most affected when the replacement ratio of Nano-TiO₂ or Nano-CaCO₃ is 3%.Nano-TiO₂ or Nano-CaCO₃ can limit the role of Nano-SiO₂ in cement paste,while Nano-TiO₂ and Nano-CaCO₃ work together in the cement paste.2.Both chemical shrinkage and autogenous shrinkage of cement are significantly increased with silica fume or meta-kaolin added,but the addition of fly ash is the opposite.The addition of Nano-SiO₂ can increase the chemical shrinkage and autogenous shrinkage of cement paste which is added double or various nano-particles and mineral admixtures.3.Under the condition of water-binder ratio of 0.30⁰.38,chemical shrinkage of cement paste with Nano-SiO₂ or Nano-CaCO₃ added is proportional to water-binder ratio.With fixed water-binder ratio of 0.34,the effect of Nano-TiO₂ on the chemical shrinkage of cement paste is the maximum.In addition,high water-binder ratio is beneficial to reduce autogenous shrinkage.4.Under the condition of curing temperature of 18²8?,the effect of nano-particles on the chemical shrinkage of cement paste are increased by the curing temperature rising.