Polypropylene Fiber as a Factor of Reduction of the Total Shrinkage Strain of Expanded Clay Concrete

Statement of the problem. The article presents the development features of the total shrinkage strain of expanded clay concrete, expanded clay fiber-reinforced concrete, expanded clay steel-reinforced concrete, and expanded clay fiber-steel-reinforced concrete. According to the analytical review, the shrinkage strain decrease as a result of the fibers adding was noted by the researchers without analyzing the reason for the phenomenon. Therefore the purpose of the study is to establish the reason for the decrease of the shrinkage strain of expanded clay concrete with the addition of polypropylene fibers. Results. It has been confirmed that the polypropylene fiber addition reduces the total shrinkage strain of expanded clay concrete by 29—34 % on the 120th day with the volume content of fibers of 0.36 %. Empirical dependences of deformations compatibility for expanded clay fiber-reinforced concrete and expanded clay fiber-steel-reinforced concrete are set forth. Conclusions. It has been experimentally established that fiber is a significant factor on the first days of the concrete mixture hardening, when the elastic modulus of the fiber is greater than or equal to the elastic modulus of the cement stone. Fibers act as a bond and affect the redistribution of shrinkage stresses within the composite, thus reducing the values of the total shrinkage strain.