Research On The Preparation And Performance Of Magnesia Micro-expansion C50 Steel Tube-confined Concrete

The concrete-filled steel tube is one kind of combination material which uses the plain concrete pour into the steel tube. Compares with the traditional reinforced concrete structure 'It has many merits such as: The supporting capacity to be high, the weight is light, plastic toughness is good, the construction facilitates and saves the cement lumber and so on. In recent years this kind of new structure was being valued people's more and more, in domestic and foreign obtained the thorough research and the widespread promoted application.Compares with the general's steel tube concretes that the steel tube high-strength expansion concretes were considered as more ideal steel tube-confined concrete. This material's characteristic was in the core high-strength concrete mixing components of the expansion, has established the earlier period initiatives tight band strength. Causes the steel tube and the core concrete before receiving the load function has the tight band strength, which would in turn make up for the general confining of concrete-filled steel tube defects that the tight band strength appeared too late to improve the performance of such materials. The main contents are summarized as follow:Magnesite take the light burning system, in 700℃, 900℃and 1100℃under the calcine keeps warm for 1 hour, determination of its activity, through the cement paste test, magnesia expansive agent on the expansion of performance, and magnesia expansive agent and ettringite expanders cement grout and mortar performance of the expansion of research, analysis and comparison of results.The induction summarizes the domestic and foreign cement concrete stability examination method, study in one kind of reasonable pressure steams under the system, the amount of magnesia and fly ash to steam the expansion behavior and the concretes performance influence to the magnesia concretes, the experiment confirmed that conforms to the stable request magnesia concretes the magnesia to mix the quantity.The design compounds the C50 steel tube concretes, enables it to have excel, high-strength, micro- expansion, self-compacting and the characteristics of good work performance.Analysis the concrete shrinkage distortion characteristic and introduces the concrete shrinkage computation model. The model building to the magnesia concretes inflation distortion analog computation; the opposite experiment measures the actual strain data, the confirmation model accuracy.The experimental results are shown following: The expansive properties of magnesia is greatly affected by calcinations temperature, The calcinations temperature is higher its activeness to be lower, the magnesia detention expansibility is also more obvious; Reasonable pressure steam pressure steam system of law can be used to be good evaluation to magnesia concrete mixed with the stability, Uses in 200℃under keeps warm 6 hour pressure to steam the law to determine in this study the micro- expansion concretes magnesia to mix the quantity not to surpass 8%; Through optimized preparation design, C50 magnesia micro-expansion concrete for the best mix: water-cement ratio of 0.32, 0.38 of sand, water units 160 kg, cementing material 500 kg, fly ash 15%, 6% of magnesia expansive agent, and it's have the good operating performance and the later period performance under this preparation 's magnesia concrete.