Effect of polypropylene fiber length on mechanical and thermal properties of autoclaved aerated concrete

In this experimental study, the effect of polypropylene fiber (PF) length on the thermal conductivity, pressure and flexural strength values of autoclaved aerated concrete (AAC) was investigated. The investigation used samples from G2/04, G3/05, and G4/06 classes AAC manufacturing in three different density and compressive strength groups. PF of three different lengths, 3, 6, and 12 mm, were chosen as reinforcement material, and AAC samples were made by adding 1.0% in the same volumetric ratios into the matrix material, taking into consideration their specific gravity. After the samples were kept in curing at 60 degrees C for 4 h, they were cured in an autoclave at 180 degrees C at 11 bar pressure for 7 h. After the autoclave process was completed, the flexural and compressive strength, thermal conductivity values of the samples were tested and the internal structure images were examined with a scanning electron microscope (SEM). It was observed that the flexural and compressive strengths of the samples increased with PF reinforcement in all density groups, while the thermal resistances decreased and the fiber length (for 3, 6 and 12 mm) had a positive effect on the compressive and flexural strengths of all examined AAC classes. It was obtained by 70.4% increase in the compressive and flexural strengths of G2/04 class of AAC samples with 12 mm length PF addition. As the PF length increases, the thermal conductivity values of all samples also increase and the highest thermal conductivity increase was observed in the G5/06 class samples with a value of 20.2%. In general, it was observed that the compressive strength, bending strength and thermal conductivity values of all samples increased depending on the increase in PF length. It has been observed that thermal conductivity values are worsen at more higher rates while the strength values of AAC at all fiber lengths is improves with PF additive.