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pozzolanic reaction
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Pozzolanic Reactions: The Key to Silica Fume's Effectiveness
What is a Pozzolanic Reaction? Definition and mechanism. A pozzolanic reaction refers to the chemical process wherein a pozzolan, a material containing reactive silica and/or alumina, reacts with calcium hydroxide (also known as lime) in the presence of water. This reaction produces calcium silicate hydrate (CSH) and calcium aluminate hydrate ...
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Analytical tests to evaluate pozzolanic reaction in lime …
It is of key importance to be able to determine the degree of pozzolanic reaction developed in a lime-treated soil in order to assess the durability of the reactions responsible for changing the properties of the treated soil. The DTA and XRD analysis methods described herein are effective and efficient tools for assessing the degree of ...
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Molecular Insight into the Pozzolanic Reaction of …
The reaction mechanism of the pozzolanic reaction of metakaolin (MK) from the atomic point of view has not yet been explored. To explain the process and mechanism of the pozzolanic reaction from the atomic point of view, molecular insight into the pozzolanic reaction of MK and calcium hydroxide (CH) was analyzed through the …
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Pozzolans and the Pozzolanic Reaction
This chemical reaction between the siliceous and/or siliceous-alumina components in the pozzolan, calcium hydroxide and water is called the pozzolanic reaction. The most often used mineral admixture in the modern concrete industry is the pozzolan.
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Chemical Reactions in Pozzolanic Concrete
In pozzolanic concrete, the chemical reactions from pozzolans help in resisting sulfate attack as they refine pores, dilute C 3 A and remove Ca(OH) 2 by converting it into a …
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Chapter 7 POZZOLANS AND THE POZZOLANIC …
little pozzolanic reaction during the first 28 days of the life of the fly ash treated portland cement concrete. In addition (and still the au thor's opinion), the total of the percentage of iron oxide and L.O.I. represents that portion of ash that merely "goes along for the ride" and contributes nothing to the pozzolanic activity of the ash.
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Heat-Induced Acceleration of Pozzolanic Reaction Under …
The pozzolanic reaction led to higher mass and surface fractal values, indicating that the pozzolanic reaction can be more easily accelerated under high temperature curing conditions. This can be explained by the fact that the pozzolanic reaction does not require the anhydrous as a reaction precursor. It consumes the …
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Pozzolanic Reactions of Metakaolin with Calcium …
Pozzolanic Reaction5.1.1. Reaction Processes and Main Influencing Factors. In this study, the pozzolanic reaction is defined according to DIN EN 197-1 representing the reaction processes between aluminosilicate (here only MK), CH and water [68].
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Effect of pozzolanic reaction of zeolite on its internal curing
The test results show that, 1) pozzolanic reaction can increase the pore volume and water absorption of zeolite particles, when the reaction degree reaches 10.85%, the pore content increases from 0.030 mL/g to 0.054 mL/g, and the water absorption increases from 3.82% to 5.52%; 2) in zeolite internally cured cement paste …
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Chemical Reactions in Pozzolanic Concrete
A pozzolanic material relies on the secondary reaction following the hydration of cement, whereby it reacts with the free calcium hydroxide to form the calcium silicate hydrates (C-S-H) phase which is the major contributor to strength in concrete; as a result there is usually long term strength development up to and beyond 91 days in pozzolanic ...
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Rate of pozzolanic reaction of metakaolin in high …
The higher pozzolanic activity of MK results in a higher rate of strength development and pore structure refinement for the cement pastes at early ages. Although the rate of pozzolanic reaction of MK becomes slower after 28 days of curing, the pozzolanic reaction in the blended cement pastes with a w/b of 0.3 still continues at the …
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Pozzolan
Formation of additional pozzolanic reaction products deposited in the POFA blended concrete interfacial transition zone decreased the permeability. Thus concrete with a strong resistance to chloride ion penetration (Chindaprasirt et al., 2011). However, the addition of POFA in excess of 30% as pozzolana, the resistance against chloride ion ...
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Pozzolanic activity of kaolins containing aluminum hydroxide …
The chemical reaction between portlandite (Ca(OH) 2) and aluminosilicates in aqueous solution is called pozzolanic reaction. It is always slow and leads to the formation of calcium-silicate ...
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Comprehensive Review of Direct and Indirect Pozzolanic …
Direct methods quantify the amount of consumed calcium hydroxide, whereas indirect methods assess changes in the physical properties of the specimen due to …
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Processing, effect and reactivity assessment of artificial pozzolans
Mechanisms of pozzolanic reactions. The main reactions of Portland cement hydration transform the tricalcium silicate (C 3 S) and the dicalcium silicates (C 2 S) to Calcium Silicate Hydrates (C-S-H) and Calcium Hydroxide (CH) (reactions (reaction 1), (reaction 2)). It is well known that the cement matrix acquires its mechanical properties …
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Cement-based materials: Pozzolanic activities of mineral additions …
1. Introduction. Pozzolanic activities are target properties of mineral systems that can be added to cement-based materials [[1], [2], [3]].A pozzolanic material is defined as a system that reacts with calcium hydroxide forming compounds that exhibit cementitious characteristics [4, 5].These pozzolanic materials are widely employed in cement-based …
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How Does Pozzolanic Reaction Make Concrete Green
of the pozzolanic index that will be demonstrated. In contrast to siliceous reactions, pozzolanic reactions could be between lime and aluminious pozzolanic materials. In this case the final hydration product of aluminous compounds in cement is assumed to be 3(CaO)Al 2O 3 6(H 2O). Consider the following pozzolanic reaction 3 [ Ca(OH) 2] + Al …
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An efficient method for determining the pozzolanic reaction …
In this study, the ionic selective dissolution method (ISDM) that combines the use of an EDTA–NaOH dissolving agent and inductively coupled plasma–optical …
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Pozzolanic Activity
The pozzolanic reaction plays the role of super-charger secondary reaction to the primary cement and water reaction as given by Equations (12) and (13) of section 4.3. From the various compositions of POFA given in Table 1, it is evident that POFA, according to ASTM C 618, can be placed into Class N pozzolan ( Table 2 ) because the sum of SiO ...
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Natural Pozzolans
The slow pozzolanic reaction of most natural pozzolans results in higher carbonation when compared with the normal Portland cement concretes at early ages. The length of moist curing of pozzolanic concretes also alters their carbonation depths. The lower the length of moist curing is the higher the carbonation depth in pozzolanic …
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Influence of quartz powder and silica fume on the …
However, secondly, the pozzolanic reactions consume part of alkaline reserves and reduce the pH in the pore solution of the cementitious matrix, which accelerates the reaction of CO 2 with the ...
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Investigation of Pozzolanic Reaction in Nanosilica-Cement …
The time to complete pozzolanic reaction is calculated with the reference value of k D. Considering the value of k D as 1.269 × 10 −17 m 2 /s, the full reaction time to complete the reaction is calculated as 760 to 2280 days with respect to kinetic models for silica fume particles having a diameter of 100 μm, as shown in Figure 5 a.
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Pozzolanic Reaction in Clayey Soils for Stabilization …
2. Review of Literature 2.1. Electrochemical Series and Pozzolanic Reaction in Treated Clayey Soils. The reactive activities in a soil stabilization process and precisely at the phase of pozzolanic reaction where displacement reactions happen depend fundamentally on the arrangement of the metallic oxides in the electrochemical …
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The effect that the pozzolanic reaction of metakaolin has …
Pozzolanic materials react with calcium hydroxide released in the hydration of Portland cement (PC), increasing the hydration heat due to the exothermic effect of the pozzolanic reaction. This fact becomes more evident in materials with high pozzolanic activity as the case of silica fume (SF), which produces an increase in heat evolution of ...
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Production of an eco-friendly concrete by including high …
However, since zeolite is a pozzolanic material, these reactions of blended binders are usually much slower than those of OPC hydration, and only after 180 days of hydration strength properties ...
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Pozzolanic reaction in the presence of chemical activators
This paper has dealt with the pozzolanic reaction products and mechanism in lime–pozzolan cement pastes in the presence of Na 2 SO 4 and CaCl 2.X-ray diffraction (XRD) analysis indicated that the hydration products in control lime–natural pozzolan pastes were calcium silicate hydrate (C-S-H) and C 413.The addition of …
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Chemical Reactions in Pozzolanic Concrete
The pozzolanic reaction occurs between silica fume and calcium oxide, producing additional CSH in many of the voids around hydrated cement particles, compounds that fill the space...
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Pozzolanic Reactions of Metakaolin with Calcium Hydroxide: …
This review examines the pozzolanic reactions of metakaolin (MK) with calcium hydroxide (CH) in various binder systems, and how alkali hydroxides, …
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Pozzolanic Reaction
Learn about the chemical reaction between reactive silica or alumina and portlandite in cement hydration, and its benefits and applications. Explore the different methods and conditions of pozzolanic reaction, and the factors that affect its speed and product.
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Relationship between strength development and pozzolanic reactions …
The pozzolanic reactions between kaolinite and lime were studied up to 2 years of curing, suing a combination of spectroscopic techniques, XRD, TGA and nuclear magnetic resonance (NMR). Quantitative analysis of the spectra obtained by each technique were conducted to determine kaolinite dissolution and lime consumption, and …
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National Pozzolan Association: How Natural Pozzolans …
Learn how natural pozzolans improve concrete by reacting with calcium hydroxide and forming cementitious compounds. Discover the different types of natural pozzolans, their …
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(PDF) Pozzolans: A review
This decrease is caused by the fact that pozzolanic reactions are retarded at room temperature [42, 87, 88]. Fly ash Addition of fly ash in concrete improves workability, reduces runoff and linear ...
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National Pozzolan Association: How Natural Pozzolans Improve Concrete
The pozzolanic reaction is a secondary, super-charger reaction to the primary reaction of Portland cement and water. Simply put, pozzolans improve concrete by converting problem-causing Calcium Hydroxide (CH)—a by-product of the hydraulic reaction between water and cement powder—to additional Calcium Silicate Hydrate (CSH)—the glue that ...
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What is Pozzolana Reaction? – theconstructor
The pozzolanic reaction is a long term reaction that includes silicic acid, water, and CaO. This may be irreversible. The high amount of free calcium and pH 12 or above must be needed to initiate the pozzolanic reaction. mechanical test and the chemical test is performed to check the activity of pozzolanic reaction. 44;
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Pozzolanic reactions of common natural zeolites with …
The pozzolanic reaction between portlandite and different types of nearly pure natural zeolites was studied. Analcime, phillipsite, chabazite, erionite, mordenite and clinoptilolite-rich tuffs were mixed with portlandite and water (1:1:2 by weight), and the progress of the pozzolanic reaction was quantitatively determined by
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Long-term pozzolanic reaction of fly ash in hardened …
The pozzolanic reaction of fly ash in hardened cement-based paste internally activated by a natural injection of saturated Ca(OH)2 solution from the age of 1 month was investigated. This investigation was conducted with the aim of comprehensively evaluating the long-term effectiveness of this technique. The Ca(OH)2 content, degree …
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