Green stalk fibers and their application in cement-based composites

Abstract

Supplementary cementitious materials, like stalk fibers, have been attracting attention in order to mitigate the consumption of fossil fuels, emission of greenhouse gases, changes in morphology of rivers and slopes, among others negative environmental impacts related to the use of cement and sand. Stalk fibers can partly replace these construction materials in order to produce eco-friendly mortars and concretes, as well as confer different features to these composites. However, the formation of some alkalis during the cement hydration forms an aggressive aqueous medium, wherein the fibers are mineralized due to migration of alkali ions onto their surface. This chapter discusses some ways to avoid these derogatory effects, which were divided into two categories, namely, fiber treatments and cement additives. The treatments can be performed using chemicals, for instance, silanization, acetylation, and mercerization, but cycles of wetting and drying (hornification treatment) and plasma discharges stand out in literature with promise results recently published for modifying fiber surface, producing cement composites with improved thermal, mechanical and durability without loss their environmental appeal. On the other hand, the use of additives seems to be a better alternative since it does not imply arduous procedures and their effectivity is not so strongly dependent of the chemical compatibility between fiber and cement matrix. Promising results were recently published, especially for binary and ternary blends with metakaolin, including total consumption of portlandite and increased final performances.