Investigation of mechanical behavior of cement mortars containing air entraining agent and fibers under freeze-thaw effect

In this study, it is investigated usability of air entraining agents and fibers decreasing harmful effects occurred in case of the concrete subjected to freeze-thaw cycles. For this objective, the study consists of two parts. In the first part of the study, cement mortars having three different types of air agent (AE1, AE2, AE3) in four different ratios (%0.00, %0.45, %0.55, %0.65) are subjected to five different freeze-thaw cycles (0, 7, 14, 28, 56). In the second part of the study, five different types of fibers (PP, CF, AR, GF, PVA) in four different ratios (0.0%, 0.4%, 0.8%, 1.2%) are added to cement mortars with the air agent type and ratio that are determined in the first part of the study. Then, these samples are subjected to five different freeze-thaw cycles (0, 25, 50, 75, 100). Thus, mechanical behaviors are investigated under freeze-thaw effects. The samples prepared and subjected to freeze-thaw cycles in the study are applied flexural, compressive and ultrasonic tests. When applied flexural tests, deflections are also determined. In addition to this, mass properties are found. The results obtained are compared with control samples. If most important results found from the study are summarized; air entraining agents can decrease mechanical properties of concrete while they increase freeze-thaw resistance of it. For this study, AE3 type air entraining agent with 0.65% addition ratio provides the best performance against freeze-thaw effects. The fibers decrease compressive strength, dynamic modulus of elasticity and specific mass while they increase flexural strength and deflection ability. The highest flexural strength is obtained with 1.2% addition of CF fiber. If it is investigated the mechanical properties of the samples subjected to repetitive freeze-thaw cycles; in some degree decrease in compressive strength, flexural strength and modulus of dynamic elasticity of the samples containing air agent or fiber or non-additive are seen. However, the samples containing both air agent and fiber show better performance against freeze-thaw damage. The best performance against freeze-thaw damage is shown with 1.2% PVA addition. The best flexural strength provided with 0.8% CF addition and the highest modulus of dynamic elasticity obtained with 1.2% PP addition. Keywords: Cement Mortars, Freeze-Thaw Resistance, Air Entraining Agents, Fibers, Mechanical Properties