Rheological Properties of Cement Paste Containing Ground Fly Ash Based on Particle Morphology Analysis

Abstract

Separating finer particles from raw fly ash is a popular method to produce high-performance admixture of concrete. However, the supply of separated fly ash is obviously behind the demand and the residue fly ash is difficult to be disposed. Ground fly ash is another method to improve the particle size and reactivity, but the change of particle morphology during grinding may affect the rheological properties of cement paste and concrete, which limits the application of ground fly ash in concrete projects. In this study, the raw fly ash, separated fly ash, and ground fly ash of the same particle size range were studied and the particle morphology was analyzed by Image-Pro Plus process and spherical particles proportion calculation. On this basis, the fluidity and rheological properties of cement paste with different fly ash content were tested and the mechanism was discussed by packing density and zeta potential analysis. The results showed that the total amount of spherical particles in fly ash-cement paste system was reduced due to the spherical particles of ground fly ash being destroyed during the grinding process. Thus, compared with the separated fly ash of similar particle size range, the fluidity of ground fly ash was significantly decreased while the yield stress and plastic viscosity increased significantly, which indicated that the rheological properties of fly ash cement paste are closely related to the particle morphology of fly ash. The results provide theoretical basis and technology support to the application of ground fly ash.

The single and hybrid use of steel and basalt fibers on high‐temperature resistance of sustainable ultra‐high performance geopolymer cement mortars

“…It is seen that all of the control and ST and BA fiber‐added UHPGPC samples have very compact, tight, homogeneous, and undamaged internal structures under ambient conditions. In addition, FA particles with a spherical structure are formed due to the dissolution of FA in UHPGPC matrix mixtures 83–85 . All the samples start to lose their tightness with the effect of elevated temperatures, especially after the impact of 500 and 800°C temperatures, voids are formed in the interior complex of specimens with the development of vapor pressure, and micro‐ and macro‐cracks are formed.…”

“…In addition, FA particles with a spherical structure are formed due to the dissolution of FA in UHPGPC matrix mixtures. [83][84][85] All the samples start to lose their tightness with the effect of elevated temperatures, especially after the impact of 500 and 800 C temperatures, voids are formed in the interior complex of specimens with the development of vapor pressure, and micro-and macro-cracks are formed. Especially at 800 C, it is seen that micro-voids and microcracks formed at lower temperatures enlarge and turn into macro-voids and cracks.…”

Flowability and Strength Characteristics of Binary Cementitious Systems Containing Silica Fume, Fly Ash, Metakaolin, and Glass Cullet Powder

“…Similarly, the MK of flaky and porous particles increased the water demand, which caused this remarkable increase in the plastic viscosity under the same replacement level. It can also be explained by the effect of packing density, which is very obvious in the cases of GP and FA [38]. GP had the highest packing density, which reduced the need for water; however, under a fixed amount of water and superplasticizer similar to the control mix, the availability of water increased; consequently, the friction among particles decreased, and the plastic viscosity decreased as well.…”

Study on Properties and Optimization of Ternary Auxiliary Cementing Materials for IOTs

“…It has been documented that FA has certain volcanic ash reactivity, and when it is mixed into cement as admixture, its active components SiO 2 and Al 2 O 3 can react with Ca(OH) 2 produced during the hydration of cement clinker to produce hydration products such as C-S-H and C-A-H [ 26 ], which is one of the main bases for FA to function in cement and concrete, respectively. Another study [ 27 ] pointed out that FA play a “morphological effect” and “micro-aggregate effect” can play a lubricating role in the material, filling the gaps in the concrete to increase the density of concrete and improve the working properties of concrete.…”