CT Identification And Analysis Of Pore State Of Porous Cement Concrete

Porous cement concrete is a kind of functional material,which is gradually valued by engineering industry.Due to the large number of pores inside the material,and its different pore states,varies functions are resulted.For example,porous concrete has the functions of water permeability,ventilation,plant regeneration.For now,most domestic and foreign scholars only study the influence factors of the porosity of porous concrete,but the study on distribution of pores,the state of pore connectivity and the pore size is very limited.In this thesis,the non-destructive testing of industrial CT is used to identify the internal porosity of porous concrete specimens.A series of CT image data extraction methods are proposed.And then the effects of different aggregates and forming processes on the internal pore state of porous concrete are analyzed.The main results are as follows:1.The identification of the internal porosity of the porous concrete specimen can be processed in black and white,and the pores can be identified through Magic Eye ICT,and the porosity also is calculated.In order to extract the data of the pore distribution,specimens can be scanned in different positions in the study area,and then the standard deviation and variance of the pore distribution in each scanning plane are used for qualitative analysis.To obtained the data of pore size distribution,pores with the same area circle are equivalent,different sizes of pores are counted,a variety of factors under the state of aperture changes are studied.In terms of the interconnection state,the CT image can be reconstructed by sampling the VTK software,and then the other software is used to identify and investigate the interconnected pore changes.2.From the first grade to the fourth grade,the internal porosity,the average pore size and the pore connectivity of the porous concrete specimens show an overall trend of increase,and the pore distribution uniformity becomes worse.In addition,the larger the volume ratio of aggregate,the larger the porosity,average pore diameter and interconnected porosity of the specimen,the greater the dispersion of pore distribution.Compared with the gravel,the porosity and average pore size of the pebble porous concrete is slightly smaller,the distribution of the pores is better and the communication porosity is slightly higher.3.Compared with the ramming method,the porosity and pore diameter of porous concrete are slightly smaller than that of porous concrete by vibration method.The longer the vibration time,the lower the porosity,the smaller the average aperture,but the change is not obvious over time.In contrast,the internal porosity distribution of the specimens by ramming method is lower than that by the vibration method,and the internal connection porosity is higher than that of the vibration method.4.In comparison,aggregate gradation is one of the four factors(aggregate volume ratio,forming process,and aggregate type)that contribute most to the uniformity of pore distribution.