Alkali-activated composites are significant materials in reducing CO2 emissions and ensuring sustainability. With the increasing concerns about climate change globally, the interest in alkali-activated materials has also increased. Researching different fibers has very important potential in this area. This study aims to make alkali-activated concretes widespread in the concrete sector by using the materials common in conventional concretes and ensuring that alkali-activated concretes are an alternative in terms of sustainability. Experimental studies were conducted to examine the mechanical, durability, and microstructural properties (SEM) of slag-based alkali-activated concrete (AASC) reinforced with three various fibers. The fibers, polypropylene (PP), polyamide (PA), and steel (ST), were used with two ratios (%0.4 and %0.8 by vol.). Compressive, splitting tensile, and flexural strength tests were carried out at 28 and 90 days. In terms of durability properties, the samples were exposed to high temperatures (300–600–900 °C) and freeze-thaw test (250 cycles). The results showed that the addition of fibers improved the strength and durability properties; for instance, the existence of steel and polypropylene fibers increased the flexural toughness factor values by 430% and 260%, respectively. Moreover, the compressive strength of the fibrous samples exposed to 900 °C was obtained in the range of 6-23 MPa.

It is known that the vast majority of buildings in Turkey are made out of reinforced concrete (RC). The 1999 Kocaeli and Düzce, the 2010 Elazig, and the 2011 Van earthquakes that occurred in Turkey revealed that the most significant factor in causing damage to buildings, or their collapse, was the use of low quality concretes, i.e., concretes with low strength values, in their construction This reveals that the load bearing members of these structures should be reinforced against the effects of possible earthquakes. The aim of the present study is to investigate the effect of carbon fiber reinforced polymer (CFRP) usage on the behavior of beams made out of low strength concrete. Within the scope of the study, the results of the experimental and numerical analysis for 14 RC beams, to which CFRP plates were applied on their lower surface, as well as for two reference beams, were presented for the case of collapsing. From the start of the test to the end, load, deflection and deformation data obtained from the beams were collected and then, by the identification of the collapsing mechanism as well as the load-deflection relation, the behavior of the beams was discussed in detail. In the numerical study, moment capacities were obtained for CFRP applied beams with different concrete strength values by using the material properties of the specimens examined in the mechanical test. The results of the numerical analysis were compared with those of the experimental tests, which were found to be consistent with each other.