Study On Shrinkage Characteristics And Reduction Of High Strength Concrete

To establish a sustainable and innovative development model,the development and application of high-performance,multi-functional civil engineering materials is the research hotspot and development direction of modern concrete preparation technology.Ultra-high strength concrete has many excellent properties such as ultra-high mechanical strength,and has become the preferred material for modern high-rise buildings,long-span Bridges,deep mines and other civil engineering structures.With the rapid development and application of high-strength concrete technology,its problems have become increasingly prominent,especially the shrinkage caused by low water-binder ratio increases,which increases the risk of cracking and destruction of concrete structure,and seriously affects its volume stability,impermeability and other durability properties.How to reduce shrinkage is a big problem that needs to be overcome in(ultra)high strength concrete technology.In order to promote the development and application of high-strength concrete and further study the influence of mineral admixtures and internal curing technology on shrinkage characteristics of high-strength concrete,this paper studies two new materials,nano-SiO2 and perforated cenospheres by testing and analysising the characteristics of autogenous shrinkage and dry shrinkage of concrete,the tendency of the compressive strength,paste density and setting time,and the main physical properties of test blocks.Meanwhile,X-ray Diffraction Analysis,Scanning Electron Microscope and Thermodynamic Analysis are adopted.The results show that nano-SiO2 can significantly enhance the strength of high performance concrete with high content of fly ash,but also greatly increases its autogenous shrinkage and dry shrinkage.Therefore,in engineering practice,when using nano-SiO2 material to compensate the strength of concrete,the influence of nano-SiO2 material on shrinkage performance of concrete should be fully considered.Because of its unique properties,perforated cenospheres can be used as microcapsules to load and transport inner curing water,and release water into surrounding cement slurry to promote cement hydration,reduce the loss of free water in concrete,effectively improve the self-shrinkage of high strength silica fume concrete caused by large silica fume content and low water-binder ratio,and have little influence on its dry shrinkage and compressive strength.It can be seen that perforated cenospheres are a kind of internal curing material with excellent performance,which have high research value and wide application prospects in the field of preparing(ultra)high strength concrete.Figure 41 table 13 reference 52...