Experimental identification of the fractional parameter of the fractional derivative standard linear solid model for fiber-reinforced rubber concrete

Abstract

This paper studies the influence of different factors, such as polymer and fiber type and aging, on the internal friction and fractional parameter, which are determined for rubber concrete and fiber-reinforced rubber concrete by means of the Resonant Frequency and Damping Analyzer (RFDA Basic) implementing the Impulse Excitation Technique (IET). Both materials contained low molecular weight cis-polybutadiene rubber SKDN-N as the main binder. Another type of binding material has been used for further investigation of internal friction phenomena in polymer concrete. Namely, low molecular weight polybutadiene rubber (BR) of mixed microstructure was utilized to produce the samples for the experimental program. Two different types of fiber are used: metal and polymer fiber. It has been found that the addition of steel fiber reduces internal friction in the material, whereas propylene fiber acts as additional damping material and increases internal friction. BR-based concrete and fiber-reinforced concrete show rather high values of internal friction, i.e. behave more viscoelastically. BR-based concrete performs higher values of the fractional parameter, and, therefore, more obvious viscoelastic properties. Introduction of steel fiber in the mixture reduces the fractional parameter, since it plays the role of additional bonds in the material structure. However, addition of propylene fiber increases fractional parameter in both, SKDN-N and BR-based concretes. It can be explained by additional damping effect of the polymer fiber. The obtained results are compared with those for the reference specimens made of ordinary Portland cement concrete, and a certain influence of the selected parameters on the internal friction of the considered materials are established.