A review: Alkali-activated cement and concrete production …
After alkali-activating the pre-treated precursors, inert aggregates such as sand and gravel are added to the mixer to form alkali-activated concrete. They increase …
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After alkali-activating the pre-treated precursors, inert aggregates such as sand and gravel are added to the mixer to form alkali-activated concrete. They increase …
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This paper presents a review of alkali-activation technology, moving from the atomic scale and chemical reaction path modelling, towards macroscopic observables such as strength and durability of alkali-activated concretes. These properties and length scales are intrinsically interlinked, and so the chemistry of both low-calcium ('geopolymer') and …
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The current study encompasses the production of alkali-activated artificial aggregates through cold-bonding pelletization technique using three different raw …
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Alkali: Base: Definition: Alkali is a basic soluble hydroxide of alkali metals or alkaline earth metals. The base is a chemical compound that reacts with acids to produce salts. Solubility: Alkalis dissolve in water to produce OH-. Bases do not dissolve in water. Relation: All alkalis are bases. Alkali is a subset of the base. All bases are not ...
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For the alkali-activation of high-calcium precursors, calcium (Ca +) has shown that it can act as a charge balancing cation like Na + and K +.If some of the Na + is replaced by Ca +, a C-A-S-H gel is formed (calcium aluminosilicate hydrate).Recent studies, show that the higher pH of the medium, the more C-A-S-H will prevail over N-A-S-H [24, …
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2.3. Test methods. To evaluate the potential reactivity of the gravel aggregate, the accelerated ASTM C1260 method was used together with the long-term ASTM C227 method [18], [19].The grain composition was prepared from the mechanically crushed gravel aggregate according to the requirements outlined in ASTM C1260 and …
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Alkali-aggregate reactivity (AAR) is one of the major causes of damage in concrete. Potential susceptibility of aggregates to this reaction can be determined using several methods.
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The efficient fractionation and recovery of lignocellulosic biomass (LCB) constituents, hemicellulose, cellulose, and lignin, are ideal for LCB utilization. In this study, we prepared a solid acid catalyst (SPS120-40) with high acid density using polystyrene resin (PS) as precursor. The synthesized catalyst was characterized by XPS, 13C NMR, …
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The key reason why alkali-activation is gaining increasing recognition and interest, after more than 100 years of sporadic utilisation, is related to the potential for …
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A further concern with using gravel containing a number of different rock types as aggregate in concrete is the possibility of Alkali-Silica Reaction (ASR), which could lead to cracking and ...
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This paper reviews the key developments in alkali-activated materials since 2011, with a particular focus on advances in characterisation techniques and structural …
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The alkali metals are very reactive, readily losing 1 electron to form an ion with a 1+ charge: [M rightarrow M^+ + e- nonumber ] Due to this reactivity, the alkali metals are found in nature only as compounds. The alkali metals combine directly with most nonmetals: React with hydrogen to form solid hydrides
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While the AMBT is often cited for its aggressive nature, adding petrographic examination (ASTM C295) to the suite of testing for an aggregate source is an extremely time efficient method and does not add significant cost to the determination of aggregate reactivity.
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Sodium metal and potassium metal react with water to produce NaOH and KOH, respectively, as well as hydrogen gas. The reaction is exothermic with enough energy to ignite the hydrogen gas being produced. Phenolphthalein can be used to visualize the production of OH-during this reaction. Potassium's increased reactivity demonstrates the …
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Learn what alkali-silica reactivity (ASR) is, how it damages concrete structures, and how to prevent it. Find out the common test methods, standards, and …
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Learn about the types, causes, and effects of alkali-aggregate reaction (AAR) in concrete, including alkali silica reaction (ASR). See how to evaluate aggregates, prevent AAR, and …
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This study compares gravel alkali reactivity results obtained from different tests conducted on coarse aggregates with complex petrography.
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What is Alkali-silica reactivity? Alkali-silica reactivity (ASR) remains a major durability issue affecting concrete structures, including heavy civil infrastructure, such as dams, bridges, pavements, and nuclear power plants — despite over 70 years of investigations. (See references [1]–[4] below.)
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Red mud is a polymetallic waste generated during Bayer's process of alumina production. High alkalinity (pH > 11), multiple elements, and micron-sized particles make red mud recycling energy-intensive and challenging. The following work presents a hydrometallurgical flowsheet for separation of different red mud elements and recovery …
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This approach aims to increase the amorphousity (activity) of the aluminosilicate material to produce one-part AAB with good physical and mechanical properties [57][58][59] [60]. Abdel-Gawwad et ...
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The alkali-silica reaction in cementitious composites occurs through the chemical association of the solution contained in the matrix pores, which is strongly basic and rich in alkalis, and the reactive phases of some aggregates. For the process to begin, high relative humidity and a high concentration of total alkalis are required. The …
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No headers. Alkali metals are the chemical elements found in Group 1 of the periodic table.The alkali metals include: lithium, sodium, potassium, rubidium, cesium, and francium. Although often listed in Group 1 due to its electronic configuration, hydrogen is not technically an alkali metal since it rarely exhibits similar behavior.
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Overview. Welcome to part 2 of our series, Foundations in Landscaping, which covers design fundamentals for homeowners and the DIY-inclined. Gravel, an often misused and misunderstood term, is a large category of aggregates that plays a central role in our lives, everyday, whether in decorative landscaping and hardscaping, or home …
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Cement is an alkali, which can cause skin burns. Take great care when mixing it to avoid producing dust. Put on your gloves. Take your yoghurt pot to the front bench to collect the ingredients. Using the teaspoons in each container, put 3 level teaspoons of cement, 3 level teaspoons of sand, and 3 level teaspoons of fine gravel into the yoghurt ...
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The results of silica dis-solving in a sodium hydroxide solution have been com-pared, as well as scale of the expansion of the mortar and concrete bars with silica …
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The Schwalbe G-One Bite SuperGround SpeedGrip gravel bike tyres are easy to set up tubeless and offer good amounts of highly predictable grip on hard surfaces and those with a layer of loose ...
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Figure: Periodic table ( Alkali metals) Discovery of alkali metals. Johan August Arfwedson, a Swedish scientist, made the initial discovery of lithium in 1817 while examining mineral ore.German chemists Gustav Kirchhoff, who created Kirchhoff's equations for electrical current, and Robert Bunsen, who gave his name to the Bunsen …
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An acid and an alkali react to form a soluble salt in solution. In this experiment, students produce ammonium sulfate from the reaction between ammonia and sulfuric acid. They can then recover this salt by crystallisation. This is a well-tried standard class experiment, which should take no more than 30 minutes.
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Like the alkali metals, the alkaline earth metals are so reactive that they are never found in elemental form in nature. ... (CaC 2), which reacts readily with water to produce acetylene. For many years, this reaction was the primary source of acetylene for welding and lamps on miners' helmets. In contrast, beryllium reacts with elemental ...
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The potential alkali-silica reactivity (ASR) of various combinations of Portland-composite cements CEM II/A, and Lithuanian aggregates from three gravel deposits are investigated in this work.
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