Effects of alkali activation and hydrothermal processes on the transformation of fly ash into Al-substituted tobermorite fiber

Hou, Xuan; Ma, Shuhua; Wang, Xiaohui; Ou, Yanjun; Liu, Ruiping

doi:10.1016/j.conbuildmat.2023.132372

Cited by 8 publications

(1 citation statement)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Minerals belonging to the tobermorite group are naturally occurring hydrated calcium silicates resulting from the hydrothermal alteration of calcium carbonate rocks [97], [142]. Typically, tobermorite is synthesized using SiO2-rich materials, such as quartz, silica powder, lime, and silica-rich fly ash [91], [92], [93]. It can be synthesized from dicalcium silicate also [102].…”

Section: X-ray Diffraction (Xrd) Analysismentioning

confidence: 99%

Mitigation Measures of Swelling Characteristics in Alkali-Contaminated Red Earth using Fly Ash and GGBS Blends

Kumar Darapu,

Vindula

2023

IOP Conf. Ser.: Earth Environ. Sci.

View full text Add to dashboard Cite

Alkali contamination induces swelling in the inherently non-swelling soils, resulting in heave severely damaging the sub and superstructures. Stabilization measures must be taken in vulnerable areas to prevent such colossal losses. Considerable research has been conducted regarding the swelling behavior of soils contaminated with alkalis and the impact of subsequent stabilization techniques utilizing different industrial byproducts and pozzolanic materials. However, there is a paucity of such studies on the Red Earth (RE) of the Visakhapatnam region. Furthermore, limited attention was given to the effects of extremely low concentrations of alkalis on the swelling behavior of soils. RE in the study area of the Visakhapatnam region predominantly consists of quartz, kaolinite, and hematite. In phase 1 of the experimental analysis, RE was contaminated with a highly dilute NaOH solution (0.05 N), and the resulting swell characteristics were investigated. A free swell of 10% was observed. One-dimensional standard oedometer tests revealed an equilibrium swelling of 5.6%, indicating significant potential for substantial heave and subsequent damage. X-ray diffraction (XRD) analysis revealed the formation of natrolite and analcime zeolites with a hollow structure, which caused the swell. Peaks of silicate minerals like paragonite and ussingite were also observed, indicating the dissolution of authigenic minerals and new precipitations even at lower concentrations of NaOH. In phase 2, swell tests were conducted on a mixture of contaminated red earth (50% w/w), fly ash (25% w/w), and ground granulated blast furnace slag (GGBS, 25% w/w), and it was observed that the swelling was completely arrested. XRD analysis unveiled that even though siliceous zeolites were formed, the development of chrysotile, attapulgite, tobermorite, and dicalcium silicate effectively inhibited the swelling with their pozzolanic behavior.

show abstract