Optimization of compositions of multicomponent fine-grained fiber concretes modified at different scale levels

The paper deals with perspectives of modification of cement composites at different scale levels (nano-, micro-, macro-). Main types of micro- and nanomodifiers used in modern concrete technology are presented. Advantages of fullerene particles applied in nanomodification of cement concretes have been shown. Use of complex modifiers based on dispersed fibers, mineral additives and nanoparticles is proposed. These are the basic components of the fiber fine-grained concretes: cement of class CEM I 42,5R produced by JSC «Mordovcement», river sand of Novoste- panovskogo quarry (Smolny settlement, Ichalkovsky district, Republic of Mordovia), densified condensed microsilica (DCM-85) produced by JSC «Kuznetskie Ferrosplavy» (Novokuznetsk), highly active metakaolin white produced by LLC «D-Meta» (Dneprodzerzhinsk), waterproofing additive in concrete mix «Penetron Admix» produced by LLC «Waterproofing materials plant «Penetron» (Ekaterinburg), polycarboxylate superplasticizer Melflux 1641 F (Construction Polymers BASF, Germany). Dispersed reinforcement of concretes was provided by injection of the fibers of three types: polypropylene multifilament fiber with cutting length of 12 mm, polyacrylonitrile synthetic fiber FibARM Fiber WB with cutting length of 12 mm and basalt microfiber «Astroflex-MBM» modified by astralene with length about 100500 microns. Analysis of results of the study focused on saturated D-optimal plan was carried out by polynomial models «mixture I, mixture II, technology - properties» that considers the impact of six variable factors. Optimum fields of variation of fine-grained modified fiber concrete components have been identified by the method of experimental-statistical modeling. Polygons of distribution levels of factors of modified cement fiber concretes are constructed, that allowed tracing changes in fields of tensile in compressive strength and tensile strength in bending at age of 28 days depending on target characteristics and variable parameters.