Search

Fissures in concrete structures result from structural deterioration and inadequate building processes, among other factors. Traditional in situ repair is often expensive and complex. For this reason, self-healing techniques have been developed, such as the use of bacteria that precipitate calcium carbonate and seal fissures. However, adding bacteria directly to the concrete matrix reduces bacterial survival. We present a review of different methods of bacterial encapsulation and their effects on fissure repair and concrete resistance. We argue that encapsulation of Bacillus subtilis in clay is the most promising method for this type of concrete, increasing concrete strength by 12% and repairing fissures of up to 0.52 mm.

Recent developments in engineering have promoted the use of reinforced composite materials from natural fibers, which provides an opportunity to investigate such materials using state-of the-art tools. Here we present a morphological and nanomechanical characterization of the parallel section of the axis of guadua Angustifolia kunth fibers (GAK) from Colombia, focusing on properties such as hardness (nanoindentation), roughness and topography. Our method was based on the application of scanning electron microscope (SEM) and atomic force microscope (AFM). AFM provided curves of force by displacement, as well as characteristics of dynamic nanoindentation systems and images. Their analysis revealed ridges and valleys on the surface of GAK fibers. The estimated surface roughness of 9.51 nm suggests an adequate value to provide superior adhesion between polymer and fiber. The same conclusion follows from our measurements of hardness, reduced modulus and nanoscale topography. Due to their excellent properties, we conclude that GAK fibers represent an ideal reinforcement material in polymer matrices.