Fine-grained concrete compositions have been developed using local raw materials of the Kabardino-Balkarian Republic - volcanic ash. In the studies for the development of fine-grained fiber-reinforced concrete composites the following were used: Portland cement PC500-DO produced by Belgorod Cement CJSC; sand from the Malkinskoye deposit with a maximum grain size of 5 mm; volcanic ash of fraction 0–0.14 mm from the Zayukovsky deposit; basalt fiber produced by Ivosteklo OJSC of the RNB-9–1200-4s brand. The mixture was prepared in a forced-action mixer, in which cement, volcanic ash, sand, basalt fiber were successively loaded and mixed until a homogeneous dry mixture was obtained, then water was added and mixing was continued again until a homogeneous dispersed-reinforced fine-grained concrete mixture was obtained. The mobility of the fine-grained concrete mixture was determined using a Suttard viscometer. The mixture spread was 18 cm. Samples measuring 4x4x16 cm were molded using the injection molding method and dried naturally in air-dry conditions. The compositions and properties of fine-grained fiber concretes with volcanic ash have been studied using methods of mathematical experimental planning. A second-order rotatable plan of the regular hexagon type with central points has been implemented to study the influence of fiber reinforcement parameters on the properties of fine-grained concrete. It has been revealed that reinforcement of fine-grained concrete with basalt fibers significantly increases their bending strength, the highest values of compressive strength are observed in the plan area with \(\mu_{\nu } \approx 1.0\;\%\) and \({\raise0.7ex\hbox{$l$} \!\mathord{\left/ {\vphantom {l d}}\right.\kern-0pt} \!\lower0.7ex\hbox{$d$}} = 1444\) , and bending strength - \(\mu_{\nu } \approx 1.25\;\%\) and \({\raise0.7ex\hbox{$l$} \!\mathord{\left/ {\vphantom {l d}}\right.\kern-0pt} \!\lower0.7ex\hbox{$d$}} = 1444\) .