Research And Engineering Application Of Super Toughness Cement-based Composite Shotcrete

Concrete is the most widely used building material in all civil and industrial buildings,transportation engineering,underground engineering and national defense engineering.With the development of science and technology,the construction technology and material properties of concrete are constantly improved.As a great progress in construction technology,shotcrete has been paid more and more attention and popularized because of its unique advantages.But at the same time,there are many shortcomings of shotcrete,such as serious decline in late strength,low tensile strength,high stiffness,poor toughness and poor durability and so on.In this paper,Portland cement is used as the base material,proper amount of admixture,mineral admixture and coarse and fine aggregate are added,and the mixture is mixed with water in a certain proportion.A kind of super toughness cement based composite shotcrete with good workability,high mechanical property,excellent shrinkage,crack resistance and good bonding property was prepared.The composition and the working mechanism of the mixed concrete are analyzed and studied in this paper.The effects of admixtures,mineral admixtures and polypropylene fiber on the workability,mechanical properties,shrinkage properties,crack resistance and bonding properties of super toughness cement based composite shotcrete are analyzed,and the optimum mix ratio is obtained.The main findings of the study are as follows:(1)The technical requirements of super toughness cement based composites are expounded,and the properties of super toughness cement based composites with different mix ratios are deeply studied.The setting time test,mechanical test,fluidity test,impermeability test and so on were designed,and the optimum mix ratio was found out.(2)The factors influencing the shrinkage performance of super toughness cement-based composite shotcrete are studied by experiments.The results show that:The drying shrinkage of super toughness cement-based composite shotcrete decreases with the decrease of the fineness of Portland cement,the decrease of water-binder ratio,the increase of the addition of shrinkage reducer,the increase of the content of fly ash,and the increase of the content of polypropylene fiber.(3)The crack resistance of super toughness cement-based composite shotcrete is studied.The effects of the content of water reducer,shrinkage reducer,expansive agent and polypropylene fiber on the crack resistance of the material are analyzed.The effects of the fineness of Portland cement,the ratio of water to binder and the content of fly ash on the bond properties of super toughness cement based composite shotcrete are studied.(4)The ratio of super toughness cement based composite shotcrete is optimized and compared with that of Portland cement concrete,including tensile bond strength and shrinkage performance,and the bonding mechanism is analyzed.Finally,through the actual engineering application results,super toughness cement-based composite shotcrete meet the construction of the construction structure of the various performance indicators required for the jet construction.Summarized the super toughness cement based composite shotcrete spray construction process,construction steps and the required mechanical equipment configuration,to evaluate the effect after construction.