Alkali leaching features of 3-year-old alkali activated fly ash-slag-silica fume: For a better understanding of stability

Author(s):  
Yingcan Zhu ◽  
Marlon A. Longhi ◽  
Aiguo Wang ◽  
Dongshuai Hou ◽  
Hao Wang ◽  
...  
Author(s):  
Hyuk Lee ◽  
Vanissorn Vimonsatit

This paper presents the mechanical properties of fly ash-based alkali-activated cement (AAC). A statistical analysis method was used to determine the effect of mix proportion parameters on the dry density and compressive strength of fly ash-based AAC pastes and mortars. For that purpose, sample mixtures were designed according to Taguchi’s experimental design method, i.e., in a L9 orthogonal array. Four factors were selected: “silica fume content” (SF), “sand to solid ratio” (s/c), “liquid to solid ratio” (l/s), and “superplasticiser content” (SP). The experimental results were analysed by using signal to noise for quality control of each mixture, and analysis of variance (ANOVA) was used to determine the significant effect on the compressive strength of fly ash-based AAC. Furthermore, a regression-analysis method was used to predict the compressive strength according to the variation of the four factors. Results indicated that silica fume is the most influencing parameter on compressive strength, which could be decreased by superplasticiser and l/s ratio. There is no significant effect of sand-to-cementitious ratio on compressive strength of fly ash-based AAC. The dry density decreases as the sand-to-cementitious ratio is decreased. The increasing l/s ratio and superplasticiser dosage could further decrease the dry density of fly ash-based AAC.


2011 ◽  
Vol 368-373 ◽  
pp. 3240-3245
Author(s):  
Zhi Jun Zhou ◽  
Hui Li ◽  
Qiang Song ◽  
Bao Jing Shen

In this paper, water glass was chosen as activator to prepare Alkali-activated slag(AAS) cement. Effects of modulus and dosage of water glass, and admixture (fly ash, slag and silica fume) on the strength of AAS cement was investigated. It was found that the modulus of water glass had great effect on the strength of AAS cement when the mixing amount of water glass was less than 12%. With the incorporation of fly ash or slag, the strength of AAS cement decreased, however the incorporation of silica fume could promote the flexural and compressive strength of AAS cement slightly.


2011 ◽  
Vol 374-377 ◽  
pp. 1632-1636
Author(s):  
Ya Chao Wang ◽  
Yao Jun Zhang ◽  
Yong Xu ◽  
De Long Xu

In order to improve the inherent fragility of alkali-activated fly ash-based geopolymer, the silica fume and styrene-acrylic emulsion were used to reinforce and toughen the geopolymer. The phase structure, morphology and chemical composition were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray fluorescence (XRF). The results showed that the mechanical properties of alkali-activated fly ash-based geopolymer were dramaticlly improved and the specimen with doping content of 10 wt% silica fume, 1wt% styrene-acrylic emulsion and 15wt% the alkaline excitation agent Na2SiO39H2O showed the highest compressive and flexural strengths of 42.11MPa and 5.30MPa in the ambient temperature curing 28d, respectively. SEM results indicated that doped silica fume and styrene-acrylic emulsion were embedded within the matrix of fly ash-based geopolymer. XRD results demonstrated that the mineral structures did not change obviously when silica fume and styrene-acrylic emulsion were added to the geopolymer


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