聚合物改性砂浆界面过渡区的电导特性

ELECTRICAL CONDUCTIVITY IN INTERFACIAL TRANSITION ZONE OF POLYMER-MODIFIED MORTARS

用交流阻抗谱方法对不同砂子体积分数的聚合物改性砂浆的电导率进行测定。用有效介质理论研究了聚合物改性砂浆界面的电导特性。利用一个将骨料看成非电导球形颗粒的混凝土模型,计算了界面过渡区的电导率与水泥浆基体电导率的比值(σITZ/σm)。计算发现:随着龄期的增加,聚合物改性砂浆的σITZ/σm的比值在最初3d内由5～9迅速降低到3左右,以后基本保持恒定,这与普通水泥砂浆的不同。结果说明:在聚合物改性砂浆中,界面过渡区电导的降低速度比水泥浆基体的快,结合不同聚灰比的聚合物改性水泥浆和乳液成膜过程的电导研究结果发现这是聚合物在界面过渡区的浓度较高和成膜所致。研究结果为聚合物改性砂浆的配置和养护工艺设计提供了依据。

Electrical conductivity of polymer-modified mortars (PMM) with different volume fractions of sand was measured using an alternating current impedance spectroscopy. The conductance of PMM was discussed based on the effective media theory. Using a model of concrete in which the aggregates are spherical and nonconductive particles, the ratio of the interfacial transition zone (ITZ) electrical conductivity and the matrix electrical conductivity σITZ/σm were calculated. The values of σITZ/σmfor polymer-modified mortars decreased rapidly from 5-9 to about 3 within the first 3 d and then stays almost constant, which are different from the ordinary cement mortars. Results indicate that the conductance of the ITZ reduces more quickly than that of the matrix in polymer-modified mortars. In addition, the concentration and the film-forming of the polymer in ITZ are the main reason from the results of the conductance for polymer-modified cement paste and the latex during its film-forming process. A proper approach for the selection of the technology of the polymer-modified mortar and concrete was proposed.