| Prefabricated building is an important direction for the development of modern architecture,which is environmental protection,efficient and saving a lot of labor.The prefabricated component is an important part in the prefabricated building,and the connection between the components is the key link in the construction process.Among the connection modes,the sleeve grouting connection is an important form of prefabricated building connection,which is highly valued by the academic and industrial circles.Due to the complex construction environment,grouting material quality the good and bad are intermingled on the market,there are often grouting material expansion ratio,the fluidity is not up to standard,leading to lack of grouting,grouting retained large number of holes in the sleeve and defect problems such as the existence of,make the anchoring strength greatly reduced,which cause serious damage to the prefabricated building structure security and the long-term durability.The purpose of this paper is to study a kind of low-viscosity and ultra-high performance grouting material used in prefabricated building construction to ensure the safety and long-term durability of prefabricated building.While preparing the grouting material and studying its performance,the effect of grouting defects and the strength of the grouting material on the performance of connection nodes was studied.Specific work includes:(1)Multiple factors such as water-binder ratio,mortar-sand ratio,water-reducing agent content,silica fume content,expansion agent content was selected to design orthogonal experiment.Through the extremum difference analysis of the experiment results,the influence of different factors on the main properties,such as initial fluidity,the fluidity of 30 min and the compressive strength of 1d,3d,28 d were studied,and the best parameters was selected to compose the optimum formula.On the foundation of the optimum formula,the admixtures of water reducer,defoamer and plastic expansion agent were further tested to obtain the initial formula of grouting material.(2)On the basis of the initial formula,ultra-fine slag and fine limestone powder as mineral admixtures was selected,and both of them have inferior water absorption then cement.study the effects of limestone powder,slag,and the combination of the them on the performance of the grouting material.The test results show that the blending of ultrafine slag and limestone powder can reduce the viscosity,but the blending of limestone powder will increase the yield stress of the grout,and both of them has a negative impact on the mechanical properties of the grout.composite powder can greatly improve the working performance of the grouting material,improve the compactness and compressive strength of the grouting material structure.The lowest plastic viscosity of composite powder grouting material is 6.05Pa·s,the lowest yield stress is almost 0Pa,and the 28 d strength can reach up to 142 MPa.(3)Study the influence of the mixing of slag and limestone powder on the performance of the grouting material by rheometer,three-dimensional digital image correlation method(3DDIC).The test results show that ambient temperature has few effect on the initial rheological properties of the slurry.However,the higher the temperature,the greater the increase in the yield stress of the slurry with time,and the incorporation of mineral admixtures can greatly reduce the increase.The incorporation of mineral admixtures can also increase the expansion rate of the slurry in the plastic phase,expand the expansion range and make the expansion more uniform.(4)Study the influence of the length and location of grouting defects,the offset of steel bars and the strength of grouting material on the performance of connection nodes in prefabricated buildings.The test results show that the grouting defect position has no obvious influence on the performance of the joint.The offset of the steel bar can cause the displacement to increase.The length of the grouting defect is the main factor affecting the mechanical performance of the joint.Three grouting materials with different strengths were selected and grouting defects of different lengths were set.The maximum critical value of grouting unsaturation of different strength grouting materials is studied by monotonic pull-out test.The test results show that the higher the strength of the grouting material,the greater the ability to withstand defects.The 28 d compressive strength of medium and high-strength grouting materials has increased by 20.1% and 62.4% then low-strength grouting material,respectively.and withstood about 5% and 18% more grouting defects. |
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