Mechanical and Microstructural Characteristics of Fly Ash-Nano-Silica Composites

IF 1.7 4区 工程技术 Q3 ENGINEERING, CIVIL
K. P. Anagha, L. Abhijith, K. Rangaswamy
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Abstract

An enhancement of the inherent strength and durability characteristics is required for the effective utilization of fly ash (FA) in geotechnical engineering applications. This study presents a novel technique employing nano-silica (NS) to stabilize FA deposits, focusing on its effects on the unconfined compressive strength (UCS) and durability. The effects of different NS dosages (0.25%, 0.50%, 0.75%, and 1%), curing periods (7, 14, 28, 60, and 90 days), mixing methods (dry and wet), cement (CEM) addition, and cyclic wetting-drying (C-W-D) on the mechanical characteristics of FA-NS composites were studied. The test results revealed that FA-NS composites exhibit superior performance compared to FA in terms of strength and durability. An optimal dosage of 0.50% NS resulted in a substantial increase of 1043% in 28-day UCS, with strength development most pronounced during the early curing stages (7 days). The type of mixing method plays a major role in the assessment of the UCS of FA-NS composites. The addition of CEM, alone or combined with NS in FA, increased the UCS but was less effective than the FA-NS composite. The durability against C-W-D was improved, with 50% and 20% increases in the 28-day UCS after the 1st and 12th cycles, respectively, maintaining a higher UCS than the actual 28-day UCS. Scanning electron microscopy images and Fourier transform infrared spectroscopy indicated the formation of primary and secondary pozzolanic compounds, contributing to a cohesive structure and enhancing the UCS and durability of the FA-NS composite. Thus, incorporating a small dosage of NS remarkably improves the inherent strength characteristics of FA and offers substantial benefits for long-term construction and geotechnical engineering applications.

Abstract Image

粉煤灰-纳米二氧化硅复合材料的力学和微结构特性
要在岩土工程应用中有效利用粉煤灰(FA),就必须提高其固有强度和耐久性。本研究提出了一种采用纳米二氧化硅(NS)稳定粉煤灰沉积物的新技术,重点研究其对无压抗压强度(UCS)和耐久性的影响。研究了不同的 NS 用量(0.25%、0.50%、0.75% 和 1%)、固化期(7、14、28、60 和 90 天)、混合方法(干法和湿法)、水泥(CEM)添加量和循环润湿-干燥(C-W-D)对 FA-NS 复合材料机械特性的影响。测试结果表明,与 FA 相比,FA-NS 复合材料在强度和耐久性方面表现出更优越的性能。0.50% NS 的最佳用量可使 28 天的 UCS 大幅提高 1043%,在早期固化阶段(7 天)的强度发展最为明显。混合方法对 FA-NS 复合材料的 UCS 评估起着重要作用。在 FA 中单独添加 CEM 或与 NS 混合添加 CEM 都能提高 UCS,但效果不如 FA-NS 复合材料。对 C-W-D 的耐久性有所改善,在第 1 次和第 12 次循环后,28 天的 UCS 分别增加了 50%和 20%,保持了比实际 28 天 UCS 更高的 UCS。扫描电子显微镜图像和傅里叶变换红外光谱显示,一级和二级水青石化合物的形成有助于形成内聚结构,提高 FA-NS 复合材料的 UCS 和耐久性。因此,加入少量 NS 能显著提高 FA 的固有强度特性,为长期建筑和岩土工程应用带来巨大好处。
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来源期刊
CiteScore
3.30
自引率
11.80%
发文量
203
期刊介绍: The aim of the Iranian Journal of Science and Technology is to foster the growth of scientific research among Iranian engineers and scientists and to provide a medium by means of which the fruits of these researches may be brought to the attention of the world’s civil Engineering communities. This transaction focuses on all aspects of Civil Engineering and will accept the original research contributions (previously unpublished) from all areas of established engineering disciplines. The papers may be theoretical, experimental or both. The journal publishes original papers within the broad field of civil engineering which include, but are not limited to, the following: -Structural engineering- Earthquake engineering- Concrete engineering- Construction management- Steel structures- Engineering mechanics- Water resources engineering- Hydraulic engineering- Hydraulic structures- Environmental engineering- Soil mechanics- Foundation engineering- Geotechnical engineering- Transportation engineering- Surveying and geomatics.
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