Apparent Quality Control Technology Of High-Pump Cable Tower Concrete

The apparent quality of concrete is an intuitive reflection of architectural aesthetics.Excellent once-molding appearance can not only shorten the construction period,improve the economy and environmental protection,but also improve the durability of concrete.Aiming at the problems of color difference and porosity on the surface of existing engineering concrete,and on the basis of meeting the requirements of high pump range,large volume and high strength,the paper studies the influence rules of vibration process,demoulding agent and mix proportion on concrete apparent quality,and puts forward the apparent quality control technology of cable tower concrete.The 0.3%carbomer transparent gel with rheological characteristics similar to that of concrete slurry was prepared,and the effect of vibration process on material movement was simulated.The influence mechanism of vibration parameters on rheological properties of slurry was simulated by software.Gel simulation shows that insertion vibration has higher vibration efficiency than external vibration.Under the vibrating action,the velocity of bubble movement is positively correlated with its size,and the direction is mostly toward the template or vibrating needle.While the aggregate will appear jump tamping and obvious subsidence only when closing to the vibrating needle.Software simulation shows that the vibrating flow field presents two semi-circular arcs,and the highest velocity and lowest viscosity appear at both ends of the arc.The change range and influence range of flow field properties can be increased obviously by increasing vibration frequency,the change range can be increased by increasing amplitude,and the influence range can be increased by increasing vibration needle diameter.When the vibration position is close to the template,the velocity of the flow field between them increases greatly,forming a region with low viscosity on the template,and the influence radius of the flow field decreases.The interface properties of release agent-formwork,slurry-isolation film and concrete-isolation film were studied,and the data of color difference and porosity of concrete surface were analyzed,so as to explore the relationship between the properties of release agent and concrete apparent quality.The results showed that the higher the adhesiveness of the release agent and the higher the viscosity of the release agent,the better the coating performance on the template.Most of the release agents can reduce the hydrophilic angle of the template and improve the wettability of slurry on the isolation film.The higher the adhesion strength is,the more likely it is to destroy the bond between concrete and isolation film,and the less the residual adhesion of concrete on the formwork.With the increase of the hydrophilic angle of the isolation film,the maximum pore diameter and area ratio on the surface will decrease,and there are risks of increasing color difference and decreasing brightness.A high viscosity curing release agent with good coating condition was developed.The adhesion amount was less than2.4 g/m~2 and the surface pore diameter was less than 2 mm,but the color difference was large under wet condition.The effects of iron oxide black,water reducing agent,water consumption,functional aggregate and rubber ratio on the workability and apparent quality of the slurry were investigated.1%iron black has the effect of early hydration and reducing the dry/wet color difference of mortar,but increases the surface color difference and porosity in concrete;the surface quality can be greatly improved by adjusting the air entraining and defoaming components of water reducer;the high proportion of cement will produce surface cracks,and the surface pores of high proportion of mineral powder are large.The incorporation of functional aggregate needs to reduce the amount of water and water reducer to reduce the impact on the apparent quality,and the decrease of water consumption will also increase the surface pores.Cement:fly ash:slag powder=60:25:15,with 120 mm vibration spacing,16～23 s vibration time the best appearance quality.Finally,the surface quality evaluation methods under different conditions are proposed.