Performance of Fiber-Reinforced Alkali-Activated Mortar with/without Nano Silica and Nano Alumina

Abstract

The current study is aimed to evaluate the effect of nanomaterials (nano alumina (NA) and nano silica (NS) on the mechanical and durability performance of fiber-reinforced alkali-activated mortars (FRAAM). Polypropylene fiber (PPF) was added to the binders at 0.5% and 1% of the volume of the alkali-activated mortar (AAM). Design-expert software was used to provide the central composite design (CCD) for mix proportions. This method categorizes variables into three stages. The number of mixes was created and evaluated with varied proportions of variables. The primary binders in this experiment were 50% fly ash (FA) and 50% ground granulated blast slag (GGBS). The alkali-activated solution to binder ratio was 0.5, and the sodium hydroxide (NaOH) concentration was 12 molarity. The sodium silicate to sodium hydroxide ratio was 2.5. The cubic specimens and prisms were evaluated in an ambient atmosphere at 23 + 3 °C room temperature at the ages of 7 and 28 days. The mechanical performance of AAM was indicated through evaluation of the compressive and flexural strength, flowability, and unit weight of the alkali activator mortar. In addition, the durability performance and microstructure analysis were also evaluated. The experiments demonstrated that the AAM without fibers and nanomaterials had a higher flow rate than the other mixtures. However, the flowability of all mixtures was acceptable. The highest compressive strength was deducted through the use of 2% NA and higher flexural tensile strength was obtained for mixtures included 1% NS and 0.5% PPF. The lower water absorption was noted through the combination of 2% nano silica and 1% polypropylene fiber. Whereas, the combination of 2% nano silica, 1% nano alumina, and 0.5% polypropylene fiber had the lower sorptivity. In addition, the microstructure analysis indicated that the nanomaterials significantly improved the matrix and the porosity of the matrix was considerably reduced.