Strength Characteristics and Microstructure Analysis of Alkali-Activated Slag–Fly Ash Cementitious Material

Abstract

Modifying the admixture of alkali-activated cementitious materials using components such as fly ash and fine sand may reduce CO2 emissions and conserve natural resources and energy. This study adopted strength testing, scanning electron microscopy, and mercury intrusion porosimetry to investigate the influence of different admixtures on the compressive strength and flexural strength of alkali slag cementing materials and the microstructure characteristics of hardened slurry under the action of load. The flexural strength of alkali slag cement slurry and mortar was reduced by replacing slag powder with fly ash. Content of fine sand less than 20% had little effect on the strength of alkali slag cement mortar; however, when the content of fine sand exceeded 30%, the strength decreased significantly. The hydration degree at 3 d was large, and the density of slurry increased with the extension of age. Increased fly ash or fine sand content decreased the density of the slurry, and increased fly ash resulted in a large number of unhydrated fly ash particles in the cementitious materials. Addition of fine sand resulted in a large number of microcracks in the slurry, which gradually decreased with the extension of hydration age.

Study on Shrinkage in Alkali-Activated Slag–Fly Ash Cementitious Materials

“…This study investigates the drying and autogenous shrinkage values of alkali-activated slag (AAS) cementitious materials with varying fly ash and fine sand contents. With the author's previous research results on the strength development law of alkali slag cementing materials, it can be found that the addition of these materials can improve the shrinkage performance of AAS at the expense of some mechanical strength [22].…”

“…To mitigate this issue, the author proposes replacing slag powder with fly ash or fine sand to reduce the shrinkage value. Previous studies have investigated the effects of adding fly ash and fine sand on the physical and mechanical properties of alkali-activated slag cementitious materials [22]. The results showed that when the amount of fly ash does not exceed 50% or the amount of fine sand does not exceed 20%, the effect on the strength of the cementitious material is minimal.…”

A Review on Development of Industrial Solid Waste in Tunnel Grouting Materials: Feasibility, Performance, and Prospects

“…Further enhancement of grouting material performance can be achieved by optimizing the addition amounts, combinational types, and process parameters of ISWs. Zhu et al [84] prepared cementitious materials using slag and fly ash as raw materials under alkali activation. The findings revealed that the compressive strength initially increased and then decreased with a decreasing fly ash content when 3% sodium hydroxide (by mass) was used as an alkali activator and the water-to-solid ratio was 0.4.…”

Study on Kinetics of Carbonization Reaction of Hardened Cement Paste Powder Based on Carbonization Degree

“…Therefore, it is crucial to focus on reducing, capturing, storing, and utilizing CO 2 in the cement and concrete industry. The most common research in this field involves CO 2 reduction, which includes reducing carbon emissions during cement production and finding alternatives to cement [ 5 , 6 , 7 ].…”