Compatibility between Rice Straw Fibers with Different Pretreatments and Ordinary Portland Cement.

Xiaoli Xie,Hongbo Li

doi:10.3390/ma14216402

Abstract

The compatibility between crop straw and Portland cement greatly restrict the application of crop straw in cement-based materials. In this study, rice straw fibers with different pretreatments were added to ordinary Portland cement (OPC), and the influence of different rice straw fiber (RF) content on the hydration process of OPC was measured using calorimeter tests. Additionally, compatibility between RF and OPC was evaluated using the inhibitory index. As a result, steam explosion treatment of rice straw removed most hemicellulose and post-treatment bleaching was used for delignification. As compared with the pure OPC, addition of RF inhibited the hydration of OPC, and the inhibition degree reduced with the increase in pretreatment degree of RF. The inhibitory index grade of different RF filled OPC (RF-OPC) samples is directly related to hemicellulose and lignin content. Compared with lignin, hemicellulose has a greater influence on cement hydration. Without considering the influence of other components, the RF-OPC samples with hemicellulose content of 1.54 wt.% reached the inhibitory index extreme grade, and the hemicellulose content of 2.05 wt.% led to the cessation of cement hydration. The inhibitory index of the samples with 2.05 and 0.85 wt.% lignin content is moderate and low grade, respectively. In addition, the results of XRD patterns and SEM images are consistent with those of heat of hydration. In terms of mechanical properties of cement-based composites with 10 wt.% rice straw fibers, pretreatment of fibers is beneficial to improving the fracture toughness of the samples.

Highlights

The application of plant fibers in cement-based materials has attracted great interest of researchers in recent years because of the low cost, high specific modulus and low density compared with synthetic fiber
The results showed that the cement inhibition directly correlated with arabinose content of the samples because the alkali solution of cement paste dissolve the linkage between lignin and hemicellulose/cellulose and produce large amounts of degraded polysaccharides, which generates an inhibitory effect on cement hydration
Steam explosion treatment greatly reduced the content of the hemicellulose component, which reduced to 7.9 wt.% in RF2 from 20.5 wt.% in RF1

Summary

Introduction

The application of plant fibers in cement-based materials has attracted great interest of researchers in recent years because of the low cost, high specific modulus and low density compared with synthetic fiber. In order to make efficient use of fibers stemming from the alfa plant, which for the most part is found in North Africa and Spain, Ajouguim et al [2] investigated the impact of alfa fiber morphology on hydration kinetics and mechanical properties of cement mortars. Many studies on the application of other plant fibers in cement-based materials have published, such as sisal fiber studies described by Frazao et al [3] and Wei et al [4], a study of banana fiber [5], a study of pine fiber [6] and a study of hemp fiber [7]. Ballesteros et al pointed out that the research and production of cement-based composites reinforced with plant fibers is a meaningful strategy to overcome environmental problems and social economic issues [15]

Methods

Results

Conclusion