آزمايش رسانايي الكتريكي اصلاح شده براي سنجش مقاومت بتن درمقابل نفوذ يون هاي كلريد

Modified Electrical Conductivity Test Method for Evaluation Concrete Chloride Ion Permeability (Text in Persian)

در اين مقاله روشي جديد براي سنجش مقاومت بتن در مقابل نفوذ يون هاي كلريد ارائه شده است كه شامل اشباع سازي نمونه ها توسط محلول NaCl 5 مول، قبل از اندازه گيري رسانايي آنها مي باشد. با اشباع كردن نمونه ها توسط محلول با رسانايي بالا، رسانايي هاي نمونه هاي مختلف بتني متناسب با ساختار منافذ آنها مي شود. براي بررسي عملكرد اين روش، طرح هاي اختلاط مختلف بتن ساخته شد. مشاهده گرديد كه نتايج روش ارائه شده حساسيت كمتري نسبت به رسانايي مايع منفذي درمقايسه با روش هاي آزمايش نفوذ تسريع يافته يون هاي كلريد (RCPT) و رسانايي حجمي (BC) دارد. همچنين ارتباط خوبي بين نتايج اين روش با نتايج آزمايش انتشار حجمي (BD) به دست آمد.

Standard test method for bulk electrical conductivity (ASTM C1760) provides a rapid indication of the concrete’s resistance to the penetration of chloride ions by diffusion. In this paper a new approach for assessing the bulk electrical conductivity of saturated specimens of hardened concrete is presented. The test involves saturating concrete specimens with a 5 M NaCl solution before measuring the conductivity of the samples. By saturating specimens with a highly conductive solution، they showed virtually the same pore solution conductivity. Different concrete samples yield different conductivity primarily due to differences in their pore structure. The feasibility of the method has been demonstrated by testing different concrete mixtures consisting ordinary and blended cement of silica fume (SF) and calcined perlite powder (CPP). Two standard test methods of RCPT (ASTM C1202) and Bulk Conductivity (ASTM C1760) were also applied to all of the samples. The results show that for concretes containing SF and CPP، the proposed method is less sensitive towards the variations in the pore solution conductivity in comparison with RCPT and Bulk Conductivity tests. It seems that this method is suitable for the assessment of the performance and durability of different concretes containing supplementary cementitious materials.