不同MB值机制砂混凝土的性能和微观孔隙结构

Properties and Micro-Pore Structure of Manufactured Sand Concrete with Different MB Values

通过控制泥粉的含量测出不同亚甲蓝(MB)值,研究不同MB值对机制砂混凝土力学性能的影响规律,并分析孔隙结构特征与力学性能的关系,引入灰色关联熵,建立机制砂混凝土孔隙结构和孔径类别对抗压强度的关系模型。结果表明,机制砂混凝土的工作性能随MB值增加逐渐变差。机制砂混凝土的抗压强度与劈裂抗拉强度随MB值增加均呈先增大后减小趋势,28 d龄期MB值为1.10时强度最大,此时机制砂混凝土的T_(2)谱面积、孔隙度、束缚流体饱和度与100 nm以上有害孔占比均达最小值。自由流体饱和度与100 nm以下有害孔占比呈先增大后减小趋势,在MB值为1.10时达最大值,随后占比随MB值增大而减小,MB值为2.00时达最小值。通过引入灰熵关联度得出束缚流体饱和度和无害孔对抗压强度的关联度最大,并在此基础上建立GM(1,3)模型,7和28 d龄期的模型预测值和试验值的平均相对误差分别为0.47%和0.26%。

By controlling the content of mud powder,different methylene blue(MB)values were measured.The influence of different MB values on the mechanical properties of manufactured sand concrete was studied,and the relationship between pore structure characteristics and mechanical properties was analyzed.The grey relational entropy was introduced to establish the relationship model between pore structure and pore size category of manufactured sand concrete and compressive strength.The results show that the working performance of manufactured sand concrete gradually deteriorates with the increase of MB value.The compressive strength and splitting tensile strength of manufactured sand concrete increase first and then decrease with the increase of MB value.The maximum value occurs at MB value of 1.10 at 28 d,At this time,the T_(2) spectrum area,porosity,bound fluid saturation and the proportion of harmful pores above 100 nm of manufactured sand concrete reach the minimum.The free fluid saturation and the proportion of harmful pores below 100 nm increase first and then decrease,reaching the maximum when MB value is 1.10,and then the proportion decreases with the increase of MB value,reaching the minimum when MB value is 2.00.By introducing the grey entropy correlation degree,it is concluded that the saturation of the bound fluid and the harmless hole has the greatest correlation degree with the compressive strength,and on this basis,the GM(1,3)model is established.The average relative errors between the model prediction value and the experimental value at 7 and 28 d are 0.47%and 0.26%,respectively.