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Alkali activation of fly ash with proper mix design and correct formulations can exhibit very good strength and chemical resistance and other potentially valuable characteristics similar or even …
When fly ash content is increased to 45%, UPV increases up to 4145 m/s or 1.17% more. The highest UPV of 4151 m/s was recorded in specimens containing 55% of fly ash, and this value is 1.32% higher compared to UPV in control specimens. When fly ash content is increased to 65%, UPV drops down to 4147 m/s.
An optional requirement for Class F fly ash is to limit its alkali content to 1.5% maximum. Class C fly ash, which has usually higher lime (CaO) content than Class F, is considered less effective to prevent ASR unless a higher replacement of cement is used. ASTM C441 is used to evaluate fly ash with a 75% reduction in expansion at 14 days.
Three alkali-activated slag formulations with different fly ash content (0, 15, and 30%) in the presence of five admixtures (vinyl copolymer, melamine, and three …
The content of the aluminosilicate component is low, and the activity is lower than of fly ash. Consequently, the mechanical strength of RFG decreases as the red mud dosage is increased. Furthermore, Fig. 3 a reveals that the mechanical strength of RFG decreased slightly when the dosage of red mud was lower than 30 wt%.
The volume of gel pores gradually increased from 7 days (Fig. 8 a) to 90 days (Fig. 8 c) in all HVFA pastes regardless of alkali content. At the early stage of 7 days, the volume of gel pores was directly related to alkali content. This could be associated with the faster rate of hydration of the HVFA system at an early age.
However, the danger to humans, wildlife, and the environment presented by fly ash production can be mitigated by using fly ash to improve the composition of concrete. Since fly ash contains aluminous and siliceous components, it may form cement when mixed with water if the calcium content of the fly ash is high enough.
Amorphous content in the fly ash has notbeen quantified from XRD. The glassy phase content of fly ash was determined by dissolving 1 g of it in 100 ml of HF(1%) acid –(Arjunan's method) with constant stirring for 6 hrs …
construction in general and an introduction to fly ash activation technology and certain basic concepts about hybrid cements (binders with a very low clinker factor and high fly ash content). In the authors' opinion, such technology may soon become highly enough developed to bridge the gap between portland cement and the cements of the future.
It has been found that optimum fly ash content depends on fly ash characteristics (including CaO%, soluble alkalis, and glass composition), aggregate reactivity, and aggregate threshold alkalinity ...
Sodium and potassium are the common alkalis present in fly ash. Excessive amounts of fly ash alkalis can cause efflorescence problems in concrete products and raise concern about the …
Table 1 shows the average coal fly ash alkali content in Europe, USA, China, India, and Australia and in function of the coal type [8,9]. The values range from 0.1% to 4.7%. ... it is well-known that the finer the coal fly ash is and the higher reactive silicon content in it, the more effective it becomes in terms of mechanical strength and ...
Alkali-activated materials (AAMs), which are prepared by using various solid wastes as precursors and reacting with alkaline solutions, are gradually applied in the construction industry. However, not all solid waste precursors can exhibit good performance in the preparation of AAMs. To realize the effective utilization of phosphorus slag (PS) solid waste, alkali …
However, Gao et al. [14] found that increasing SF content reduced the workability of alkali-activated slag-fly ash paste since more water was needed to wet particle surface. Moreover, SF exhibits potential as an activator due to its chemical reactivity, serving as a supplier of silicates in alkaline solutions [15], [16] .
PDF | On Apr 23, 2018, Revathi and others published Studies on Physio Chemical Properties of Fly Ash for their Effective Alkali Activation | Find, read and cite all the research you need on ...
The production of Ordinary Portland cement (OPC) requires calcining limestone, which leads to high energy consumption and CO 2 emissions [1].Alkali activation can use industrial solid wastes, such as blast furnace slag and fly ash, as the precursor to realize the effective utilization of the wastes.
The chloride binding mechanism of alkali-activated materials (AAM) under various granulated blast furnace slag (GBFS)/fly ash (FA) ratios is investigated in this work. Two types of layered double hydroxides (LDH), i.e., MgAl-LDH and CaAl-LDH, and active magnesium oxide (MgO) were added to reduce the concentration of free chloride in AAM.
Amorphous content in the fly ash has notbeen quantified from XRD. The glassy phase content of fly ash was determined by dissolving 1 g of it in 100 ml of HF(1%) acid –(Arjunan's method) with constant stirring for 6 hrs [19]. Dried samples (110°C) were weighed and the content of glassy phase was determined by weight loss.
This paper presents results regarding the phase composition, microstructure and textural properties of two types of aggregates, which were prepared via crushing or pelletization of …
The self-hardening property of fly ash owing to its free lime content has made fly ash a suitable for construction material . However, ... Luo, X., Xu, J., Bai, E., Li, W.: Systematic study on the basic characteristics of alkali-activated slag-fly ash cementitious material system. Constr. Build. Mater. 29, 482–486 (2012)
Fly ash (FA) is a typical aluminosilicate solid waste, and it has been intensively studied as a precursor for the preparation of geopolymers because it is widely available globally and has a relatively consistent chemical composition (Turner and Collins, 2013, Scrivener et al., 2018).However, the massive production and application of FA-based geopolymers are still …
Studies on Physio Chemical Properties of Fly Ash for their Effective Alkali Activation Revathi 1, Jeyalakshmi * Rajamane2, Sivasakthi, Dhinesh3 ... Amorphous content in the fly ash has notbeen quantified from XRD. The glassy phase content of fly ash was determined by ...
Reaction, Phases, and Microstructure of Fly Ash-Based Alkali-Activated Materials Akira Matsuda1, Ippei Maruyama2*, Amr Meawad 3, Sanjay Pareek4, Yoshikazu Araki 5 ... amorphous content in fly ash and alkali activated prod-ucts were quantified using Rietveld analysis (Bish and Howard 1988). The software used for Rietveld analysis
Optimum moisture content (OMC) values for fly ashes vary from 11 to 53%, and maximum dry density values range from 1.01 to 1.78 g/cm3. Country-specific trends in terms …
Subsequently, the reaction degrees of fly ash and slag can be calculated as follows: (5) α fly − ash = 1 − V t fly ash V 0 fly ash × 100 % (6) α slag = 1 − V t slag V 0 slag × 100 % where α fly−ash is the reaction degree of fly ash, V (t)fly−ash is the volume fraction of unreacted fly ash at age t obtained from the BSEM image ...
The results showed that the compressive strength of stabilised soil significantly increased when the fly ash was activated. The optimal activation parameters to stabilise the …
Download scientific diagram | Alkali content in fly ash with different soaking time. from publication: Mechanism of the effect of alkali metal on the electrostatic precipitability of fly ash | The ...
1. Introduction. Alkali–activated materials (AAMs) or geopolymers are potential sustainable cementitious alternatives to ordinary Portland cement (OPC) [1].AAMs are produced with precursors such as fly ash (FA), ground–granulated blast–furnace slag (GGBFS a.k.a. slag), and metakaolin (MK), and are activated with alkaline activators at room temperature [3], [4], [5].
As shown in Figure 3b, the strength development coefficient of GPM decreased significantly and then slowly with the increase in fly ash admixture, which can be explained mainly by the high stability of fly ash itself (particle structure denseness and surface activation energy) weakening the effective amount of alkali activator . In addition ...
However, the danger to humans, wildlife, and the environment presented by fly ash production can be mitigated by using fly ash to improve the composition of concrete. Since fly ash contains aluminous and siliceous …
