Study On Mechanical Properties Of High Throw Self-compacting Concrete And Its Application In Concrete-filled Steel Tube Column

Concrete-filled steel tube columns(CFST)are usually equipped with transverse diaphragms and vertical ribs,which makes it difficult to pour concrete into the columns and ensure concrete compactness.In addition,the core concrete for super high-rise concrete-filled steel tube columns is poured in sections,which often requires an additional operating platform,and the construction cost is high.If the method is adopted from the upper floor slab or roof,the direct one-time ultrahigh pouring construction is convenient and the cost is low,but the ultra-high falling impact force is large,which may lead to concrete segregation.Self-compacting concrete has good fluidity and anti-segregation ability and is widely used in concrete-filled steel tube columns.However,whether the self-compacting concrete will undergo segregation in the process of ultra-high falling,and then affect the mechanical properties of the self-compacting concrete after forming,is also a problem that concerned engineers.Therefore,this paper intends to discuss the reasonable free-falling height and the corresponding construction method when pouring self-compacting concrete by the high throwing method through the study of the mechanical properties of high throwing self-compacting concrete and its practical engineering application.The main contents of this paper include:(1)The compression strength of the cube and prismatic stress-strain relationship of high throw self-compacting concrete was studied with high throw height parameters(10,15,20,25,30m).(2)The cube splitting strength of self-compacting concrete with high throwing height(10,15,20,25,30m)was studied.(3)Considering the construction factors,taking the time loss of self-compacting concrete as the parameter,the influence of time loss on the mechanical properties of high-throw selfcompacting concrete is considered.(4)The working performance of self-compacting concrete mixed with artificial sand is often poor.Through the changes in the anti-segregation index,compressive strength,and splitting strength after high throwing,this paper discusses whether the high throwing method is also suitable for self-compacting concrete mixed with artificial sand.(5)Combined with engineering examples,the 30 m high steel tube core concrete is poured by the method of high throwing self-compacting concrete.A 1:1 test column shall be conducted for the process test in advance.After the formed process test column is cut,the compactness of concrete shall be observed and its strength shall be tested by the rebound method.(6)Based on the previous experimental research and process test,the construction method of high-throw self-compacting concrete steel tube is used,and it is applied in the pouring of 30 m high concrete-filled steel tube columns.