Nanomodified Basalt Fiber Cement Composite with Bottom Ash

Abstract

Directed control of the process of structure formation of a cement composite from modern positions must be carried out taking into account the synergistic effect of its components. In particular, the cement composite, when applied with pozzolanic additives and fiber reinforcement, is transformed into a more complex material with excellent performance. The aim of the article is to study the combined action of nanomodified basalt fiber (NBF) and bottom ash (BA) as structural elements of concrete. To achieve this aim, a number of tasks were performed, including the development of nanomodified-basalt-fiber–bottom-ash–cement concretes, as well as the study of their fresh, physical and mechanical properties (flowability, average density, compressive and flexural strength, elastic modulus and crack resistance) and durability characteristics (water, frost and abrasion resistance). A series of nanomodified basalt-fiber-reinforced concretes (from 0 to 7 wt.% NBF) were developed, in which the economical Portland cement CEM I 32.5 N was replaced by up to 45 wt.% mechanically activated bottom ash residue (400 m2/kg). An economical superplasticizer with a high water-reducing capacity (35%) made it possible to achieve uniform flowability of the mixes (slump 20–22 cm and slump flow 45–52 cm). The combined effect of BA and NBF provides control over the structure formation of cement materials, which ensures the redistribution of internal stresses from shrinkage deformations throughout the entire volume of the composite; under loading, the process of crack formation slows down, the stress concentration near structural defects decreases, and stresses are redistributed in the microstructure of the cement composite between its components. Perfect values of mechanical properties (compressive strength up to 59.2 MPa, flexural strength up to 17.8 MPa, elastic modulus up to 52.6 GPa, critical stress intensity factor 0.507 MPa m0.5) are explained by the complex action of the ash residue and nanomodified basalt fibers. A mix with 30 wt.% BA and 5 wt.% NBF is characterized by water resistance grade W18, frost resistance class F400 and abrasion resistance 0.59 g/cm2, which confirms the high wear resistance of the developed materials.