Investigation of the properties of lightweight concrete added with silica fume and steel fiber

When lightweight concretes are compared with normal concretes; It is a material with many advantages such as lightness, sound and heat insulation, and fire resistance. Although there are different methods in its production, the most widely used lightweight aggregate concrete provides flexibility to engineers at the design stage. By reducing the constant load in the buildings, significant advantages such as reduced size of the building elements, less foundation cost, heat and sound insulation performance, reinforced performance against seismic effects are obtained. However, due to the fact that the physical and mechanical properties of concretes are directly related to the properties of the aggregates present in the concrete composition, even though lightweight aggregate concretes reach sufficient strength, they can sometimes be in a more negative situation in terms of elastic properties. With this study, 16 different mixtures were designed using the Taguchi technique; silica fume (SD) 0%, 5%, 10% and 15%; pumice/sand 0%, 50%, 75% and 100%; pumice/coarse aggregate 0%, 50%, 75% and 100%; steel fiber ratio was chosen as 0%, 0.5%, 1% and 2%. The effect of mineral additives obtained by substituting SD instead of cement and pumice instead of aggregate on the performance of lightweight concrete was investigated. At the end of the 3rd, 7th, 28th, 90th and 180th days, some physical properties and flexural strength, compressive strength, abrasion and fire resistances were measured on the water cured and hardened samples. The test results showed that if the pumice/sand ratio is between 50-100% and SD is used at 15%, a strength of 39 MPa can be achieved. But when SD is not used, only 37 MPa strengths can be achieved at 75% pumice/sand and 75% pumice/coarse aggregate. KEYWORDS: Pumice, silica fume, lightweight concrete, steel fiber, compressive strength