Drying Shrinkage and Mechanical Strength of Cementitious Composites with Alkali-Treated Makino Bamboo Fibers

ABSTRACT

Alkali-treated bamboo fibers (AFs) treated with different NaOH concentrations (5 and 10%) and treatment times (1, 12, and 24 h) were used as fillers to fabricate cementitious composites with AFs (CAFs) in the present study. The results demonstrated that alkali treatment caused the partial decomposition of hemicellulose and lignin and an increase in the surface roughness of bamboo fibers. Additionally, the amounts of calcium hydroxide in alkali-treated CAFs were higher than in untreated CAFs, and they increased with increasing NaOH concentration and treatment time. For drying shrinkage (DS) under 75% relative humidity (RH), the DS values of the CAFs significantly decreased after adding AFs compared to the DS values of untreated CAFs. Compared to untreated CAFs, the density of the 5% and 10% NaOH-treated CAFs with longer treatment times decreased by 2.9% and 5.1%, respectively. Furthermore, the tensile strength of all alkali-treated CAFs exhibited no significant differences when compared with that of untreated CAFs, while the modulus of rupture and compressive strength were significantly decreased by NaOH treatment. These results indicated that the AFs significantly improved the drying shrinkage of the CAFs and hydration retardation effect of cement pastes, while the density and mechanical strength of the CAFs decreased.

摘要

本研究采用不同NaOH浓度（5%和10%）和处理时间（1、12和24小时）的碱处理竹纤维（AF）作为填料，制备了含有AF的水泥基复合材料. 结果表明，碱处理使竹纤维的半纤维素和木质素部分分解，表面粗糙度增加. 此外，碱处理的CAFs中的氢氧化钙含量高于未处理的CAF，并且随着NaOH浓度和处理时间的增加而增加. 对于75%相对湿度（RH）下的干燥收缩率（DS），与未处理的CAFs相比，添加AF后的CAFs的DS值显著降低. 与未处理的CAFs相比，处理时间较长的5%和10%NaOH处理的CAF的密度分别降低了2.9%和5.1%. 此外，与未处理的CAFs相比，所有碱处理的CAF的拉伸强度没有显著差异，而NaOH处理显著降低了断裂模量和抗压强度. 这些结果表明，AF显著改善了CAFs的干燥收缩和水泥浆体的水化阻滞效果，同时降低了CAFs的密度和机械强度.

KEYWORDS:

• Alkali treatment
• bamboo fiber
• cement
• drying shrinkage
• makino bamboo
• mechanical strength

关键词:

• 碱处理
• 竹纤维
• 水泥; 干燥收缩
• makino竹
• 机械强度

Highlights

• Effects of adding alkali-treated bamboo fibers (AFs) on the properties of cementitious composites with AFs (CAFs) were investigated.

• Bamboo fibers were treated with various NaOH concentrations and treatment times.

• AFs significantly improved the drying shrinkage of the CAFs and hydration retardation effect of cement pastes.

• A decrease in density, flexural strength and compressive strength of the alkali-treated CAFs was observed.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author’s contribution

C.-H. Yeh: Data curation, Formal analysis, Investigation, Resources, Validation, Visualization, Writing – Original Draft, Writing – Review & Editing. J.-H. Wu: Funding acquisition, Investigation, Supervision, Validation, Writing – Review & Editing. T.-C. Yang: Conceptualization, Data curation, Funding acquisition, Investigation, Methodology, Project administration, Resources, Supervision, Validation, Visualization, Writing – Original Draft, Writing – Review & Editing.

Additional information

Funding

This work was supported by the National Science and Technology Council, Taiwan under Grant NSTC 108-2313-B-005-014-MY3 and NSTC 111-2313-B-005-028-MY3.