Alkali Silica Gel
Alkali Silica Gel - Related Videos
03:06
Alkali Metals
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2020
Group 1 elements are soft and shiny metallic solids. They are malleable, ductile, and good conductors of heat and electricity. The melting points of the alkali metals are unusually low for metals and decrease going down the group, while the density increases going down the group with the exception of potassium (Table 1). Table 1: Properties of the alkali metals Element Electron Configuration Atomic Radius (pm) IE1 (kJ/mol) Melting Point (°C) Density at 25 °C (g/cm3)
01:10
Silica Gel Column Chromatography: Overview
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2024
Silica gel column chromatography is a technique for separating compounds using a column packed with silica gel as the stationary phase. This method relies on differences in the polarity of compounds. Based on their polarities, compounds move between the stationary phase (silica gel) and the mobile phase (the solvent), forming discrete bands in the column. Polar components tend to bind strongly to the silica gel, causing them to move slowly through the column. In contrast, nonpolar compounds...
06:30
Gel Purification
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2023
Gel purification is used to recover DNA fragments after electrophoretic separation. DNA recovery from an agarose gel includes three basic steps: binding, washing and eluting from a silica column. DNA is believed to bind to silica in the presence of high salt via a salt bridge. Following binding, DNA is washed of impurities and eluted under low salt conditions disrupting this interaction. This video goes through a step-by-step, generalized procedure for cutting out a band from the gel, gel...
10:52
An Alkali-burn Injury Model of Corneal Neovascularization in the Mouse
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Cited by 75 •
2014
Neovascularization (NV) of the cornea can complicate multiple visual pathologies. Utilizing a controlled, alkali-burn injury model, a quantifiable level of corneal NV can be produced for mechanistic study of corneal NV and evaluation of potential therapies for neovascular disorders.
09:11
Porosimetry of a Silica Alumina Powder
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2023
Source: Kerry M. Dooley and Michael G. Benton, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA Surface area and pore size distribution are attributes used by adsorbent and catalyst manufacturers and users to ensure quality control and to determine when products are at the end of their useful lives. The surface area of a porous solid is directly related to its adsorption capacity or catalytic activity. The pore size distribution of an adsorbent or catalyst is...
FAQs
Hydroxyl ions attack and break down the structure of reactive silica within the aggregate. Sodium and potassium ions from the cement pore solution then enter the altered silica material, producing the gel phase. This sequence explains why both reactive aggregate silica and alkaline pore chemistry are important when engineers assess the potential for alkali-silica reaction in concrete.
Moisture enables the gel to absorb water and increase in volume. As this water uptake occurs within hardened concrete, the swelling gel can generate internal pressure. Consequently, moisture control is an important preventive consideration: limiting available moisture can reduce the conditions that promote gel expansion and the resulting stress within the concrete.
The critical transition is from chemical formation to mechanical pressure. After absorbing moisture, the gel expands within the concrete and presses against surrounding cement paste and aggregate. When the resulting internal pressure contributes to cracking, the structure may develop map-pattern distress and experience reduced durability, making gel-related expansion an engineering concern.
Map-pattern cracking is a notable form of distress associated with alkali-silica reaction. Engineers can consider this cracking, together with the known interaction between reactive aggregates, alkaline pore solution, and moisture, when diagnosing the reaction. The presence of such distress is relevant because the process can also indicate a broader risk of reduced concrete durability.
Understanding the gel helps engineers connect aggregate composition with the potential for alkali-silica reaction. If an aggregate contains reactive silica, interaction with alkali hydroxides in the cement pore solution may initiate the sequence that produces expansive gel. This knowledge supports evaluation of aggregate reactivity and helps interpret cracking or other durability concerns in concrete structures.
The overview identifies three principal approaches: using low-alkali cement, incorporating supplementary cementitious materials, and controlling moisture. These measures address the chemical or environmental conditions that support damaging expansion. Engineers can use them when selecting concrete materials and exposure controls, with the goal of limiting gel-related swelling, cracking, and loss of durability.