تصرف الأعمدة الخرسانیة المسلحة المغمورة في أنواع مختلفة من الترب العدوانیة

Behavior of Reinforced Concrete Columns Buried into Different Types of Aggressive Soils

    Concrete resistance to sulfate attack is one of the most important properties for maintaining durability of concrete. The main objective of this research is to evaluate the performance of several types of reinforced concrete columns buried in two pits at a 3-meter depth in one of the agricultural areas in the holy city of Kerbala, one contains a sandy soil with sulfur salts (SO3 = 10.609%) and the other contains a clayey soil with salinity ratio of (SO3 = 2.61%). In this research, three types of concrete mixes have been produced and utilized: normal strength concrete, polymeric concrete, and high strength concrete. A total of 21 reinforced concrete columns, 126 concrete cubes, and 63 concrete cylinders were prepared.

     The columns and reference concrete specimens were cured for 28 days with tap water and then buried in soils for (60, 150, 240) days. A number of laboratory testing methods have been carried out on the specimens: (axial compression strength of concrete columns, compressive strength test for concrete cubes, splitting tensile strength of concrete cylinders, absorption test, voids ratio and density of concrete cubes). These tests have been conducted at different ages of exposure.

     Test results showed that the aggressive soils (containing sulfates and chlorides) affect the performance of all types of concrete mixes negatively with age of exposure. The deterioration was more for specimen buried in sandy soils. It is found that the resistance of high-strength concrete to aggressive soils was better than other types of concrete.

     The percentage of decrease in compressive strength of concrete columns exposed to aggressive solutions in the clayey soil for normal, polymer, and highstrength concretes ranged from (0.95-12.51) %, (20.28-24.96) %, and (1.5-15.62) % respectively. The percentage of decrease in compressive strength capacity of polymer, and high-strength concrete columns exposed to aggressive solutions in the sandy soils ranged between (20.03-37.52) %, and (0-18.74) % respectively, compared to the reference concrete columns not buried in soils.

    In contrast a development in strength was observed for normal concrete columns exposed to aggressive sandy soils, it reads up to (11.7 %) after (240 days) of exposure. The durability test results (absorption and voids ratio) showed a deterioration (increases) for polymer and high strength concrete mixes, while it was not observed in normal concrete mix.