Dr. M. A. Chamorro-Trenado

On the Path to a New Generation of Cement-Based Composites through the Use of Lignocellulosic Micro/Nanofibers

Pere Mutje

Fabiola Vilaseca Morera

The stiffness of a composite material is mainly affected by the nature of its phases and its contents, the dispersion of the reinforcement, as well as the morphology and mean orientation of such reinforcement. In this paper, recovered dyed cotton fibers from textile industry were used as reinforcement for a polypropylene matrix. The specific dye seems to decrease the hydrophilicity of the fibers and to increase its chemical compatibility with the matrix. The results showed a linear evolution of the Young’s moduli of the composites against the reinforcement contents, although the slope of the regression line was found to be lower than that for other natural strand reinforced polypropylene composites. This was blamed on a growing difficulty to disperse the reinforcements when its content increased. The micromechanics analysis returned a value for the intrinsic Young’s modulus of the cotton fibers that doubled previously published values. The use of two different micromechanics models allowed evaluating the impact of the morphology of the fibers on the Young’s modulus of a composite.

15 May 2019 in Materials

Journal Article

Rafel Reixach

Josep Claramunt

An Approach to Understanding the Hydration of Cement-Based Composites Reinforced with Untreated Natural Fibers

M. Mercè Pareta

Marc Delgado-Aguilar

Due to its high biocompatibility, bio-degradability, and low cost, cellulose finds application in disparate areas of research. Here we focus our attention on the potential applications of cellulose nanofiber in cement-based materials for the building sector. We first describe the chemical/morphological composition of cellulose fibers, their process and treatment, the characterization of cement-based composites, and their flexural strength. In recent research in this field, cellulose has been considered in the form of nano-sized particles, i.e., cellulose nanofibers (CNF) or cellulose nanocrystals (CNC). CNF and CNC are used for several reasons, including their mechanical and thermal properties, their extended surface area and low toxicity. This study presents some potential applications of lignocellulosic micro/nanofibers (LCMNF) in cement-based composites in order to improve flexural strength. Samples were made with 0.5-1.0-1.5-2.0 wt% of LCMNF obtained from pine sawdust, CEM I (Portland) and a 1:3 cement-water ratio. The composites were then tested for flexural strength at 7, 14, and 28 days and the evolution of flexural strength was assessed after water immersion during 72 h. Scanning electron microscopy was employed to visualize the bond between LCMNF and the cement matrix. Results showed that LCMNF improved the flexural strength of the composite in all the dosages used.

11 June 2023 in Sustainability

Journal Article

Fernando Julian

Ester Gifra

Francesc Xavier Espinach

Experimental study on the vertical interface of thin-tile masonry

The use of untreated natural fibers to reinforce cementitious composites improves their environmental friendliness, resulting in a more sustainable material. Moreover, the influence of the untreated natural fibers on the hydration process of Portland cement composites presents some uncertainties. According to the literature, the most usual tests to analyze the degree of hydration of cement composites are the differential thermal and thermogravimetric analyses (TGA/dTGA). Several authors propose to analyze data methods to establish the degree of hydration of cement composites. This paper presents the TGA/dTGA test carried out on mortar samples with and without fibers at age 2, 3, 7, 14, and 28 days. The degree of hydration was calculated according to Bhatty’s method. To characterize the raw materials, the quantitative chemical was determined using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM–EDX). The main findings of this study were that the presence of untreated natural hemp fibers in the OPC composites increased the hydration degree by 9%. The presence of fibers affected the formation of several components. Thus, their presence increased the formation of monosulphate, reduced portlandite, did not affect ettringite, and increased the formation of calcite, thereby improving the sustainable footprint due to the increased CO₂ fixation.

1 November 2020 in Construction and Building Materials

Journal Article

Miquel LLorens

Experimental Study of Mechanical Behavior of Dry-Stone Structure Contact

Javier Gómez Colom

Cristina Barris

25 November 2024 in Buildings

Journal Article

Irieix Costa Prieto

Joan Fontàs

Experimental Behavior of Brick Masonry under Uniaxial Compression on Parallel-to-Face Brick. Single-Leaf Case Study

Nathanael Savalle

Dry-stone structures are traditional constructions that are present everywhere around the world, with their stability working mostly by gravity. Contrarily to their in-plane behavior, their out-of-plane response is very brittle and is fully controlled by the geometry, as well as the contact properties, between units (stones). Two main local failure modes of dry-joint contact are identified to lead to the global failure of the structure: (i) sliding and (ii) joint opening. Most of the existing studies investigated full structures to obtain the global response and/or couplet only, with the aim of only characterizing the contact. The present experimental work studies the effect of sliding and joint opening between stones at different scales: couplets, structures made of a few (up to five) blocks, and full walls, as well as varying the way the masonry units are assembled within a single structure. Different stones are employed to quantify potential differences. All the structures are loaded up to the collapse with a tilting table to induce out-of-plane actions. Repeatability tests are also conducted to better understand the effect of contact variability. This study unveils that the heterogeneity of the dry-joint contact, as well as the repartition of the blocks, affects the global response (both in terms of load capacity and failure mode). It also confirms that the most critical local failure mode is produced by the joint opening.

27 August 2018 in International Journal of Architectural Heritage

Journal Article

Miquel LLorens