Effect of Walnut-Shell Additive on the Structure and Characteristics of Concrete.

The partial replacement of the mineral components of concrete with natural renewable analogues in full possession of the performance characteristics of the final material, allows not only the concrete-production process to be made more environmentally friendly and inexpensive, but also to solve an important task for the agricultural industry, which is that associated with waste disposal. The scientific novelty of the work is in the obtaining of new concrete compositions by the partial replacement of coarse aggregate with a natural analogue in the form of a walnut shell, which has the maximum ratio of the strength of the composite to its density, as well as in identifying new dependencies of strength and density and their ratio on the amount of replacement of mineral coarse-aggregate walnut shell. The main goal of this article was to analyze the effect of composition factors on characteristics of concrete with partial replacement of large aggregates with walnut shells and to search for the optimal compound that would make it possible to obtain concrete with a minimum decrease in strength characteristics with a maximum decrease in concrete density. Cubes and prism laboratory samples were made from concrete of normal density with the replacement of coarse aggregate by 5, 10, 15, 20, 25 and 30%, by volume. The main mechanical properties, such as density, strength (compressive, tensile, tensile strength in bending) of the concrete samples were studied. The investigation used standard methods and scanning electron microscopy. An increase into strength characteristics up to 3.5%, as well as the maximum ratio of strength to density of concrete, was observed at a walnut-shell dosage of 5%. Effective partial replacement of coarse aggregate with walnut shells leads to a reduction in the consumption of crushed stone by up to 10% and a decrease in the mass of concrete by up to 6%.