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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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While it is commonly accepted that the pozzolanic reaction takes place faster than the ASR gel formation [5, 10], Bazant et al. [16] have shown, using a mathematical model, that below a given pessimum size (around 1–2 mm), the swelling pressure generated by alkali-silica gel decreases with the size of reactive particles. …
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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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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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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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Learn about the definition, properties and applications of pozzolans, a type of mineral admixture that reacts with calcium hydroxide to form cementitious compounds. This …
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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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Pozzolanic reactions occur after cementitious hydration reaction at slower rates, which contribute to slower strength gain. In soil stabilization using stabilizers such as lime, RHA, FA, and ESP, strength development is caused by pozzolanic reactions only that provide a slower strength gain. Eventually, at the exhaust of required inputs for ...
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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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The pozzolanic reaction degree of SCMs was assessed using a modified selective dissolution test [3]. The initial mass of raw materials and the CH content of the cement pastes were determined through thermogravimetric analysis (TGA) [3]. The pore microstructure of the cement paste was examined through mercury intrusion porosimetry …
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When raw and calcined clays are mixed with CH and simulated cement pore solution (which contains 43 mM Na, 95 mM K, and has pH=13.2), the most dominating reaction products are C-S-H and C4AH, in various concentration, indicating that both Si and Al from the clay participate in pozzolanic reaction. The content of reacted Al is …
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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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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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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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Up to 90 days, the reactions continue barely and values reach to 69%. This implies that the pozzolanic reaction of calcined kaolinites occurs mainly within 28 days and the reaction slows down thereafter. However, the reaction before 28 days progresses differently for the H ordered clays (K1 and K2) compared to the M (K3) and L ordered …
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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 pozzolanic material slurry with pozzolanic reaction belongs to a nonisothermal heterogeneous system. According to the Arrhenius equation: (7) K = A exp (-Ea/RT) where k is the reaction rate constant; A is the frequency factor; Ea is the activation energy of the reaction, kJ/mol; R is the ideal gas constant, 8.314 J/(mol*k); and T is the ...
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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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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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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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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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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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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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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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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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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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The following article introduces, in a thorough manner, how the chemical pozzolanic reaction takes place in cement composites containing the fly ash (FA) additive. In the research part, however, the development of phases in the structure of the cement paste in the initial period of its curing and after 28 days from its preparation was traced. …
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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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Silica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone. In the present paper different aspects of the …
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