Sunday, June 29, 2008

Bat Mitzvah Dresses For Tweens

TE STREET FESTIVAL CALL INVITATION







This Sunday June 29, 2008 was a special report in Excelsior on urban art, much in several interviews, including some of the girls are coming out in this book-object, as the case of IZOLDAK , also made a couple of mentions of the book-object and illustrates various parts of the story with images of the book.

Reporters are: Virginia Baptist


Patricia Edgar A. Lamb Hernández

Some photos of Solomon Ramírez and other collaborations. Invitation

Saturday, June 28, 2008

2005 Honda Pilot Tire Sensor

CEMENT

PORTLAND CEMENT INTRODUCTION


.

binder is a hydrophilic, resulting from the calcination of limestone, sandstone and clay, in order to obtain a fine powder that hardens when water is present gaining strength and adhesion properties)

As mentioned in Chapter 1, the name comes from the similarity in appearance and advertising intended to give effect in 1824 Joseph Apsdin an English builder, for patenting a process of calcination of limestone clay producing a hydrated cement acquired according to him, the same resistance that stone island near the port of Portland in Dorset.
is in 1845 when developing the industrial process of modern Portland cement with some variation persists to this day and consists of ground limestone with some clay shale composition and subjecting the powder to temperatures above 1300 ° C producing what is called the clinker, consisting of hardened balls of different diameters, Lesnar finally ground gypsum as a final product having an extremely fine powder.


PORTLAND CEMENT MANUFACTURING

The starting point of the manufacturing process is the selection and exploitation of raw materials for processing accordingly.
Components main chemical raw materials for cement manufacturing and general proportions involved are

Chemical Component


Hometown Usual calcium oxide (CaO)
limestone

95% Silica Oxide (SiO2)

Sandstone
Aluminum Oxide (Al2O3) Clays


Iron Oxide (Fe2O3)
Clays, Iron Ore, Pyrite

magnesium oxide, sodium, 5%


Potassium, Titanium, Sulphur,
Several

Match Minerals and manganese


typical percentages involved in the Portland cement mentioned oxides are:


Component Percent Oxide Typical Abbreviation



CaO 61% - 67% SiO2


C 20% - 27% Al2O3
S

4% - 7% Fe2O3


A 2% - 4% F


SO3 1% - 3% MgO


1% - 5% K2O and Na2O


0.25% - 1.5%


can see an overview of modern manufacturing in the system called for dry ", which is cheaper because it needs less power, and is the highest employment in our area, however we must bear in mind that each manufacturer has a particular equipment available depending on your needs.
It begins with the quarrying of raw materials and subjected to a primary crushing process is reduced in size to around 5 stones "and then processes this material into a secondary crusher which reduces them to a size of about 3 / 4 ", which are capable of being subjected to grinding. The materials are ground individually in a ball mill to be converted into a fine powder, impalpable, being dosed and then intimately mixed in suitable proportions for the type of cement that is desired.
The mixture is then introduced into a rotary kiln consisting of a large metal cylinder of refractory material coated with diameters ranging between 2 and 5 m. and lengths between 18 and 150 meters. The oven has a slight inclination with respect to the horizontal of around 4% and a rotation speed of 30 to 90 revolutions per hour. Depending on the size of the oven, can be produced daily from 30 to 700 tons. The heat source is at the opposite end of the income and material can be obtained by injection of pulverized coal, oil or gas ignition, with temperatures between 1.250 and 1.900 ° C. Developed
temperatures along the furnace produced first open water evaporation, then the release of CO2 and finally in the area of \u200b\u200bhigher temperature melting occurs around 20% 30% of the load and when the lime, silica and alumina are recombined swarming in nodules of various sizes, usually 1 / 4 "to 1" diameter characteristic black color, bright and hard when cooled, called " Portland cement clinker. "
In the final stage, the clinker is cooled and ground in a ball mill together with plaster in small amounts (3 to 6%) to control the hardening violent. The grinding produces a fine powder containing up to 1.1 x 10 12 particles per kg and that passes completely through a sieve No. 200 (0.0737 mm., 200 openings per square inch). Finally, the cement passes be stored in bulk, being then supplied in this form or heavy bagging for distribution.

In the wet process the raw material is ground and mixed with water to form a slurry which is introduced into the rotary kiln using a similar process as above but with higher consumption of energy to remove the water added. The process used depends on the characteristics of raw materials, economy, and in many cases by ecological considerations as the wet process is that the dry cleaner.
During all processes running detailed checks the manufacturer to ensure both quality and proportions of ingredients such as temperature and final product properties, for which there are a series of physical tests and standardized chemical and laboratory equipment developed specifically for this work.

can see the sources of raw materials of which you can get the components to make cement, which appreciates the variety of possibilities in nature in order to produce this material.


COMPOSITION OF PORTLAND CEMENT.

After the training process and final grinding of clinker, the following compounds are obtained first established by Le Chatelier in 1852, and which are those that define the behavior of hydrated cement and detail its chemical formula and name abbreviation
current
a) Tricalcium Silicate (3CaO.SiO2 -> C3S -> Alita-

Define the initial resistance (in the first week) and is very important in the heat of hydration.

b) dicalcium silicate (2CaO.SiO2- -> C2S -> Belita) .-

Define long-term resistance and has minor effect on the heat of hydration.

c) Tricalcium Aluminate (3CaO.Al2O3) -> C3A) .- Singly

has no bearing on the resistance, but with silicate setting determines the violent act as a catalyst, making it necessary to add gypsum in the process (3% - 6%) to control it. Responsible
cement resistance to sulfates and to react with these results sulfoaluminate expansive properties, so you have to limit its content.

d) Aluminium-Ferrito tetracalcium (4CaO.Al2O3.Fe2O3--> C4AF - Celita) .- .-
Table 3.1 Sources of raw materials used in manufacturing portland cement
. (Ref. 3.3)



Cal Silica Alumina


SaO

SiO2 Al2O3


Aragonite

Clay calcareous clay (Marga) Calcite

Seashells
Waste Slag alkaline


Marble Slate Limestone

Residual dust from clinker
Rock Chalk
calcareous clay

calcareous clay (Marga)

Arena Sandstone Basalt

fly ash

ash rice husk. Slag


Quartzite Limestone limestone

calcium silicate clay

calcareous clay (Marga)

Bauxite Waste fly ash

aluminum ore.
copper slag slag

Staurolite
Granodiorite

Slate Limestone

washing waste aluminum ore limestone



Gypsum Iron Magnesia



CaSO4.2H2O
Fe2O3 MgO
Clay



ash and blast furnace slag from iron pyrite laminations

Boards
iron ore washing

waste iron ore

Calcium Sulfate Anhydrite Gypsum


Slag Limestone limestone




has significance in the rate of hydration and secondarily in the heat of hydration.

e) Magnesium oxide (MgO) .-
Despite being a minor component, is important because for contents greater than 5% expansion brings problems hydrated and hardened paste.

f) Potassium and Sodium Oxide (K2O, Na2O -> Alkalis) .-

cases have special importance for chemical reactions with certain aggregates, and soluble in water contribute to producing efflorescence with limestone aggregates.

g) manganese oxide and titanium (Mn2O3, TiO2) .-

The former has no special significance in the properties of cement, except in color, which tends to be brown if they contained more than 3%. It has been observed that in cases where the content exceeds 5% decrease in resistance is obtained over time. (Ref.3.2)
The second influence on the resistance, reducing it to more than 5% contained. For lower contents is of no importance. Of the compounds

mentioned, silicates and aluminates are the major components, but not necessarily the most significant ones, because as we shall see some of the minor components are very important for certain conditions of use of cement.

BOGUE
THE FORMULA FOR THE CALCULATION OF THE POTENTIAL FOR CEMENT COMPOSITION.

in 1929 following a series of experimental investigations, the chemical formulas RHBogue states that allow the calculation of the components of cement on the basis of knowing the percentage of oxides containing, having been taken as a standard by ASTM C-allowing practical approach to any potential behavior normal Portland cement is not mixed.

then establish Bogue formulas should be clear that based on the following assumptions: ¨

compounds have the exact composition. (It is not entirely true because in practice have impurities). ¨

equilibrium is obtained at the temperature of formation of clinker and maintained during cooling. (In practice, the formulas overestimate the C3A and C2S)

BOGUE FORMULAS (Composition Potential):

If Al2O3 / Fe2O3 ≥ 0.64: \u200b\u200b

C3S = 4.071CaO - 7.6SiO2 - 6.718Al2O3 - 1.43Fe2O3 - 2.852SO3

C2S = 2.867SiO2 -
0.7544C3S
C3A = 2.65Al2O3 - 1.692Fe2O3

C4AF = 3.04Fe2O3


< 0.64 se forma (C4AF+C2AF) y se calcula:
If Al 2O3/Fe2O3
(C4AF + C2AF) = 2.1Al2O3 + 1.702Fe2O3

and whose case is calculated as Tricalcium Silicate :

C3S = 4.071CaO - 7.6SiO2 - 4.479Al2O3 - 2.859Fe2O3 - 2.852SO3

(These no C3A cements so the sulfate resistance is high, the C2S is calculated as)

variants in the proportions of these compounds are those that define the types of cements that we will see later, and the practical importance of the Bogue formulas is that which will be to assess the likely potential composition and compare it with standard values \u200b\u200bfor each type of cement, trends can be estimated in terms of behavioral characteristics we are interested from the standpoint of the concrete, such as development of resistance over time, hydration heat, resistance to chemical aggression etc.


mechanism of hydration of cement.

hydration is called the set of chemical reactions between water and cement components, which carry the state change the hardened plastic, with the inherent properties of the new products formed. The components mentioned above, to react with water forming calcium hydroxide and complex carbohydrates.
The rate at which hydration takes place is directly proportional to the fineness of cement and inversely proportional to the time, so it is very rapid initially and decreases gradually with the passage of days, but never get to stop.

Contrary to what was thought years ago, the reaction with water joins the cement particles but each particle is dispersed in millions of particles of hydration products disappearing initial constituents. The process is exothermic generating a flow of heat to the outside called heat of hydration.

Depending on the temperature, time, and the relationship between the amount water and cement react, you can define the following states that have been set arbitrarily to distinguish the stages of the hydration process:

a) .-

Union Plastic water and cement powder to form a moldable paste . The lower the water-cement ratio, the higher the concentration of particles compacted cement paste and thus the structure of hydration products is much more resistant.
The first element is the C3A react, and then the silicate and C4AF, characterized by the scattering process of each grain of cement in million particles. Counteracts the action of gypsum speed reactions and in this state produces what is called the latent period or rest in which the reactions are attenuated, and lasts between 40 and 120 minutes depending on temperature and the cement particle. In this state they form calcium hydroxide which contributes to significantly increase the alkalinity of the dough reaches a pH of about 13.

b) initial set

.- Status of cement paste in which speed up chemical reactions, begin the hardening and loss of plasticity is measured in terms of resistance to deformation. It is the stage where the exothermic process is evident where it generates the aforementioned heat of hydration which results from chemical reactions described.

a porous structure is formed gel called calcium silicate hydrates (CHS or Torbemorita), colloidal consistently intermediate between solid and liquid to be stiffened more and more to the extent that continue to hydrate the silicates.

This period lasts about three hours and produced a series of chemical reactions that are causing the gel CHS more stable over time.
At this stage the paste can remix without permanent deformations or alterations in the structure that is still in training.

c) .-

final set is obtained after completing the stage of initial set, characterized by significant and permanent deformation hardening. The gel structure consists of the final assembly of hardened particles.

d) Curing .-

occurs from the final set and is the state to hold and increase with time resistant properties. The predominant reaction is the continuing hydration of calcium silicates, and in theory continue indefinitely.

is the final state of the paste, which fully demonstrate the influence of cement composition. The strong hydration express very low solubility so that the tightening is still feasible under water.
setting There are two phenomena that are different from those described, the first is the so-called "Curing False" that occurs in some cements due to heating during the grinding of clinker with gypsum, resulting in the partial dehydration of the resulting product for that by mixing cement with water, crystallization and hardening occurs apparent during the first 2 minutes of mixing, but remixing the material plasticity is recovered, without generating heat of hydration and resulting negative consequences. The second phenomenon is the "set violence" that occurs when during manufacture is not added in sufficient amount of gypsum, which produces an immediate tightening, development violent heat of hydration and permanent loss of plasticity, however it is very unlikely at present that this phenomenon occurs, because with modern technology added gypsum is controlled very accurately.


HYDRATED CEMENT STRUCTURE.

During the hydration process, the external volume of the paste is relatively constant, however, internally the solid volume increases steadily over time, causing a permanent reduction of porosity, which is inversely related to resistance of the hardened paste and directly to the permeability.
To produce complete hydration is required enough water for the chemical reaction and provide the structure of empty or space for hydration products, the proper temperature and time, getting rid of this fundamental concept of cure, which is in essence these three elements to ensure that the process is complete.

A basic concept that will allow us to understand the behavior of concrete, is that the volume of hydration products is always less than the sum of the volumes of water and cement that arise because of the chemical combination of water volume decreases by about 25%, which brings result in contraction of the hardened paste. The hydration products need a space of about twice the volume of solid cement to produce complete hydration.
Another important concept to be taken into account is that it is shown that the lower value of the water-cement ratio to produce complete hydration of cement is about 0.35 to 0.40 in normal weight and additive mixed depending on the precise relationship of each individual case. In

, illustration can be seen as a typical pattern of the structure of cement paste and water distribution, distinguishing the following parts:

a) .- Cement Gel

Formed by strong hydration (calcium silicate hydrate), the water in the gel, water is called combination, which is not to be intrinsic evaporable chemical reaction.

b) Gel Pores .-

small space between solids that do not allow moisture inside the formation of new solid hydration. The water contained within these pores is called water gel, which can evaporate under special conditions of exposure.

c) capillary pores

.- Formed by the spaces between groups of solid hydration dimensions that provide space for the formation of new hydration products, which are called capillary water contained in them.

To better understand how different components are distributed in the structure of hydrated cement paste, we will establish some relationships that allow us to calculate in a particular case, for which we initially consider a system where there is no loss evaporative water or additional water enters cure:
Sea:
Pac = weight of water
combination Pch = Weight of cement hydration
Vac = Volume of water in combination = Pac / Pch

It must: Pac
Pch = 0.23 ......................( 1)

(average ratio determined experimentally)


Sea:
Cv = Contraction in volume due to hydration
Ga = Specific gravity of water

We mentioned that the water in combination shrinks 25% then:

Cv = 0.25 x Pac / Ga = 0.25 x 0.23 Pch / Ga
Cv = 0.0575 Pch / Ga ..................... (2)

Sea:
sh = Volume of solids of hydration = Pch / Gc Gc = Gravity


specific cement has to be:
sh = Pch / Gc + Vac - Cv ..........( 3)

Replacing (1) and (2) in (3) gives:
sh = (1/Gc + 0.1725/Ga) Pch ..........( 4)

other hand:

Po = porosity of the hydrated paste
Vag = Volume of water gel

defined:
Po = Vag / (sh + Vag) (5)
Replacing (4) to (5) and solving gives:
Vag = [(Po / (1-Po)) x (1/Gc +0.1725 / Ga)] Pch (6) Sea
:

Vad = Volume of water available for hydration

We have:
Vad = Vac + Vag ............................ ........( 7)

Replacing (1) and (6) in (7) and solving follows:

Pch Vadx1 =.. / [(0.23/Ga + (Po (1-Po) ) x (1/Gc +0.1725 / Ga)] (8).

Finally, we define:
VCSH = unhydrated cement volume
Pcd = Weight of cement available
VCV = volume of capillary voids

And it has that:

VCSH = Pcd / Gc - Pch / Gc ...........................( 9)
VCV = Pcd + Vad - sh - Vag - VCSH ............( 10)

With these relationships we have developed which shows the changes in the components of the structure of the paste 100 gr. cement with various amounts of water available for hydration having assumed the following typical parameters:

Gc = Specific gravity of cement = 3.15
Ga = Specific gravity of water = 1.00
Po = porosity of the paste hydrated = 0.28

can see that for very low values \u200b\u200bof the water / cement hydration stops from lack of water to hydrate fully the amount of cement available, remaining unhydrated cement and empty capillaries are capable of allowing entry of additional water and space to develop more solid hydration.
their hydration products, then there are water-cement ratio for which extra water for more than that we provide, there will be total cement hydration.
We also see that for normal conditions as those assumed in which the pasta has only the initial mixing water, you need a water-cement ratio of 0.42 minimum order, and if it provides extra hydration water, the minimum is order of 0.38.
Con los valores de la se han elaborado las 5 donde se gráfica a título explicativo el % de hidratación y el % de cemento no hidratado en función de la relación Agua/Cemento, así como los vacíos capilares obtenidos.
Hay que tener presente, que pese a que para relaciones Agua/Cemento inferiores a las que producen el 100 % de hidratación, aún queda cemento sin hidratar, la estructura es mas compacta con menor cantidad de vacíos, por lo que se obtienen en la práctica características resistentes mas altas pese a no contarse con toda la pasta hidratada; sin embargo para lograr la hidratación máxima que es posible alcanzar con relaciones Agua/Cemento muy bajas, se necesitan condiciones that merit special mixing and pressure increase in compaction energy and otherwise does not moisturize as planned. In practice, with normal mixing conditions was possible to achieve water-cement ratio paste minimum of about 0.25 to 0.30 depending on the type of cement and the conditions of temperature, humidity, pressure and mixing technique. Under special conditions, have got to get pasta in laboratory water-cement ratio as low as 0.08 (Ref.3.6)


TYPES OF CEMENT AND ITS APPLICATIONS MAIN.

Types of portland cement standard that we can qualify, because their manufacture is regulated by requirements are specific (Ref. 3.5): Type I

.- For general use, where special properties are not required.

Type II .- moderate sulfate resistance and moderate heat of hydration. Structures for use in harsh environments and / or mass emptied.

Type III .- Rapid development of resistance to high heat of hydration. For use in cold weather or where you need to advance the commissioning of the structures.

.- Type IV Low heat of hydration. Massive concrete.

Type V - High resistance to sulphates. For very aggressive environments.

When the first three types of cement were added the suffix A (eg Type IA) means they are cements which have been added air entraining in its composition, keeping the original properties. Interestingly

cements referred to as "mixed or added" because some of them are used in our midst:

Cement Type IS .- which was added between 25% to 70% of blast furnace slag referred to total weight. Type

ISM .- Cement which has added less than 25% of blast furnace slag on the total weight.

.- Cement Type IP that pozzolan has been added at a rate ranging between 15% and 40% of the total weight.

IPM .- Cement type that has been added pozzolan at a rate up to 15% of the total weight.

These cements have variants that entrained air is added (suffix A), induced moderate sulfate resistance (suffix M), or moderate heat of hydration (suffix H).

pozzolans are siliceous inert materials and / or alumina, which individually have almost no binding properties, but finely ground and chemically react with calcium hydroxide and water resources are cementitious properties. Pozzolans are usually obtained calcined clay, diatomaceous earth, tuff and volcanic ash, and industrial waste as fly ash, pulverized brick, etc.
The particularity of replacing part of cement by these materials, is to change some of its properties, such as the increasing durations of the above conditions, delay and / or slow the development of resistance over time, reduce permeability , the more water holding capacity, greater cohesiveness, increased water requirements to form dough, lower heat of hydration and better performance against chemical aggression.
must be borne in mind that the variation of these properties will not always be appropriate depending on the particular case, so that you can not take pozzolanic cement or the addition of pozzolan as a panacea, as they are very sensitive to temperature variations and construction processes curing conditions.

end mix design must take into account that the standard cements have a specific gravity of around 3.150 kg/m3 and pozzolanic cements are lighter in specific gravity between 2.850 and 3.000 kg/m3.

in which you can see typical behaviors of basic cement, on the development of resistance over time and heat of hydration.
can be seen in the physical and chemical requirements of manufacturing standards established by ASTM C-150 for standard cements appointed and in the. statistics are reported variation of the components of the various types of normal cement in USA and England, where it is concluded that the elasticity in manufacturing standards supports variations but should not influence the final strength required, if they can cause time-varying behavior.


PERUVIAN CEMENTS AND THEIR CHARACTERISTICS.

currently manufactured in Peru cement Type I, Type II, Type V, Type IP and Type IPM.
can be seen in the physical and chemical characteristics of domestically produced cement provided by the manufacturers, except for cement Rumi, the producer did not agree to provide them, despite our insistence, so an analysis is entered at the request of the author at the Catholic University of Peru in connection with the use of this material during construction of the airport in Juliaca, in which the results are quite irregular a Cement Type I, which nevertheless must be taken with caution because only a sample. In

, Resistances are plotted versus time for different Peruvian cements based on information supplied between January and April of 1.993.
is interesting to note that in general the national cement are typical behaviors in the long run it is reasonable to expect similar cement manufactured in abroad, but experience in using them and the variability that can be seen in the analysis and graphics shown us that the underlying property in the short term do not always keep constant parameters, so you should never rely on them a priori without performing tests of control to the case of works of some importance.
On the other hand, local manufacturers have much experience in the manufacture of cement, but none of them is in the practical application of this material in concrete production because very rarely collect data, or do research in particular, so which is very little information can make in this regard and also, there is usually reluctance to provide results of its quality control routinely. However, we must acknowledge the assistance provided by the producers who agreed to provide and include in this book data provided.
No information is published periodically by the manufacturers on basic issues such as the variation of resistance development time variation of hydration depending on environmental conditions, characteristics of the employing pozzolans in blended cements, statistics interlaboratory controls made, etc.

information would be extremely useful to users and researchers to avoid many situations that behavior is expected by extrapolation outside information or local information incomplete and you get another for lack of reliable data.

As an additional comment would have to say that the introduction of pozzolanic cement and pozzolan modified in our environment has brought benefits from the point of view that have advantages concerning durability as well as being profitable for the manufacturer to replace it cheaper pozzolana cement costs and selling prices experienced some reduction, but these benefits are not fully exploited since it has not been enough research, outreach and educational efforts regarding the considerations for dosing, which results in deficiencies in its use by the user.
normally assumed that these cements designs require the same amount of water than normal, which in practice is not true, as some of them require up to 10% more water and have a consistency that deserves greater cohesive energy compaction so that eventually the economy is not so alleged.
in the Appendix includes copies of the original data supplied by manufacturers in 1993 and 1996, including additional information to that contained in the tables and can be useful for anyone interested in learning more about these issues.


CONTROL AND STORAGE CONDITIONS ON SITE AND ITS CONSEQUENCES.

I already mentioned in relation to the national cement makes us reflect on the need to address if possible to do in work time statistical monitoring and storage conditions and quality of cement used.

A good practice is the run chemical analysis in a reliable laboratory every 500 tons of cement for great things, and seek regular certified manufacturers with results of quality control. In any case the sample is obtained must be less than 5 kg
For storage conditions, is often recommended to clean deposit metal silos especially in high humidity climates, because there is partial hydration of cement adhering to the walls, and using the results that emerge silo hardened pieces and mix with fresh concrete causing problems uniformity of concrete production.
In the case of cement in bags, the concept is similar as to protect from moisture, either isolating or protecting soil indoors.
A practical way to assess whether there has been partial hydration of cement stored, a sample is to sift through the mesh No 100, according to ASTM C-184, weighing the detainee, which the total weight, gives an order magnitude of the portion hydrated. The percentage retained without hydration usually ranges between 0 and 0.5%.
If you remember the concepts regarding the mechanism of hydration can estimate that if we use partially hydrated cement, will be replaced in practice by adding a portion of hardened cement strength characteristics uncertain and definitely below the sand and stone, which will cause areas weak structure, whose significance will be greater the larger the proportion of these particles.

can be estimated that the use of cement hydration by 30% on total weight, with granules of not more than 1 / 4 "results in a reduction resistance to 28 days of the order of 25%, depending on the cement in particular. It is obvious that higher percentages hydrated, with particles larger than 1 / 4 "will cause more negative damage resistance and durability.
Finally, we should clarify that in terms of storage, the proper criterion for evaluating the quality of cement is not time that has been stored but the conditions of hydration of cement within that period, so it is advisable to take provisions to prevent or delay the hydration from the start, instead of letting time pass without caution and then enter in the complications of evaluating whether it will fit or not for use.


REFERENCES


Read Frederik .- "The Chemistry of Cement and Concrete" .- Edward Arnold Publishers - London 1988. Adam Neville

.- "Concrete Technology" .- Mexican Institute of Cement and Concrete - Mexico 1977.

S. Kosmatka, Panarese W. .- "Design and Control of Concrete Mixtures," Portland Cement Association - USA 1988. Sandor Popovics

.- "Concrete: Making Materials" .- Edit. Mc Graw Hill - 1979.

ASTM Standard C-150 .- "Standard Specification for Portland Cement" -1986.

ACI SCM-22 .- .- Troubleshooting Concrete Construction Seminar Course Manual.USA 1990.

ASTM Standard C-595.- "Standard Specification for Blended Hydraulic Cements"-1986.

U.S. Bureau of Reclamation.- "Concrete Manual" Eight Edition- Revised - 1988.

Free Kates Playground Ipad Movies

Cement






History A brief overview of the history of cement around the year 700 BC the Etruscans used pozzolan and lime mixture to make a mortero.Ya in the year 100 BC the Romans used mixtures of lime pozzolan for concrete compressive strength of 5 Mpa.Hasta 1750, just use lime mortars and pozzolanic materials (diatomaceous earth, flour, brick etc).. By 1750-1800 are investigated mixtures caliza.Smeaton calcined clay and compared in 1756 with the appearance and hardness of Portland stone to the south of England. 40 years later, Parker cement factory then natural to apply the term "cement" (previously interpreted as "caement" "any substance capable of improving the properties of others). Vicat explains in 1818 in a scientific manner the behavior of these" "binders". In 1824, Aspdin patented portland cement giving the name for commercial reasons, because of its color and hardness that remind you of Portland stone. Until the advent of self-hardening hydraulic mortar, the mortar was prepared in a mortarium (pan mortar) for percussion and tear, such as in the chemical industry and the years 1825-1872 farmacéutica.Entre appear first cement factory in England France and Germany. 1880, studied the hydraulic properties of slag high horno.En in 1890 appeared the first cement factory España.es 1980, there are 1,500 factories producing about 800 million tons / year . Today cement is the glue or "binder" cheaper than known. Properly mixed with water forms aggregates and concrete, artificial amorphous rock able to take more varied forms with a performance very important mechanical compression. The tensile strength can be improved with the use of reinforcement (reinforced concrete).







Types of cement

have established two basic types of cement: clay
Source: derived from clay and limestone in proportion 1 to 4 or so;
pozzolanic Source: pozzolan cement can be organic or volcanic origin.
There are several types of cement, different in composition, its resistance and durability, and therefore by their targets and uses.
From the chemical point of view is generally a mixture of calcium silicates and aluminates, obtained through the baking of limestone clay and sand. The material obtained, very finely ground, once mixed with water is hydrated and gradually solidifies. Since the chemical composition of cements is complex, specific terminology used to define the compositions.

The
Portland cement Portland cement is the type of cement used as binder for the preparation of concrete or concrete.
was invented in 1824 in England by Joseph Aspdin constructor. The name comes from the similarity in appearance to the rocks found on the Isle of Portland, an island county of Dorset.
The manufacture of Portland cement is given in three phases: (i) Preparation of the mixture of raw materials, (ii) Production of clinker, and (iii) Preparation of the cement.
raw materials for production of Portland are minerals that contain:
calcium oxide (44%), silicon oxide
(14.5%),
aluminum oxide (3.5%), iron oxide
( 3%)
manganese oxide (1.6%).
The extraction of these minerals is done in quarries, which should preferably be close to the factory, minerals and often have the desired composition, however in some cases it is necessary to add clay or limestone or iron ore, bauxite, or residual ore smelters. Scheme

oven
The mixture is heated in a special oven, consisting of a huge cylinder (called a kiln) arranged horizontally at a slight angle, and rolling slowly. The temperature increases along the cylinder up to about 1400 ° C, the temperature is such that the minerals are combined but do not melt or glaze. Section
lower temperature, calcium carbonate (limestone) is separated into calcium oxide and carbon dioxide (CO2). In the high temperature zone of calcium oxide reacts to form silicates and calcium silicates (Ca2Si and Ca3Si). It is also a small amount of tricalcium aluminate (Ca3Al) and Ferroaluminato tetracalcium (Ca4AlFe). The resulting material is called clinker. The clinker can be stored for years prior to the production of cement, provided it does not come in contact with water.
The energy required to produce clinker is approximately 1,700 joules per gram, but because of the heat loss value is considerably higher. This implies a high demand of energy for cement production, and thus releasing a large amount of carbon dioxide in the atmosphere, greenhouse gas.
To improve the characteristics of the final product clinker it adds about 2% of gypsum and the mixture is finely ground. The cement powder obtained is ready for use.
cement composition obtained has a type:
calcium oxide 64% 21%

silica alumina 5.5% 4.5%

iron oxide, magnesium oxide 2.4% 1.6
% 1% sulfate
other materials, including primarily water.
When Portland cement is mixed with water, the product solidifies and hardens in a few hours gradually over a period of several weeks. The initial hardening is produced by the reaction of water, gypsum and tricalcium aluminate, forming a crystalline structure calcium-aluminum-hydrate, estringita and monosulfate. The subsequent hardening and development of internal forces of tension arising from the slower reaction of water with the tricalcium silicate to form a structure called amorphous calcium-silicate-hydrate. In both cases, structures that are formed wrap and set grains of materials present in the mixture. A final reaction produces silica gel (SiO2). The three reactions generate heat.
With the addition of special materials to cement (lime or lime) yields plastic cement that sets faster and more easily workable. This material is used in particular for the external cladding of buildings.
The quality Portland cement shall be in accordance with ASTM C 150.
In 2004, the world's largest producers of portland cement were in France Lafarge, Holcim in Switzerland and Cemex in Mexico. Some cement producers were fined for monopolistic behavior.

clinker formation reactions
1000-1100 ° C3CaO + Al2O3 + SiO2 → 3CaOAl2O3 2CaO 2CaOSiO2 → CaO + Fe2O3 → CaOFe2O3
1100-1200 ° CCaOFe2O3 +3 CaOAl2O3 → 4CaOAl2O3Fe2O31250-1480 ° C2CaOSiO2 + CaO → 3CaOSiO2
will end Composition From 3CaOSiO2

51% 26% 11% 3CaOAl2O3
2CaOSiO
12% 4CaOAl2O3Fe2O3


hydration reactions of hydration reactions, which form the setting process are:
2 (3CaOSiO2) + (x +3) + H2O → 3CaO2SiO2xH2O 3CA (0H) 22 (2CaOSiO2) + (x +1) 3CaO2SiO2xH2O + H2O → Ca (0H) 22 (3CaOAl2O3) + (x +8) + H2O → 4CaOAl2O3xH2O 2CaOAl2O38H2O3CaOAl2O3 + 12H2O + Ca (0H) 2 + 7H2O → → 4CaOAl2O313H2O4CaOAl2O3Fe2O3 3CaOAl2O36H2O + CaOFe2O3H2O
These reactions are all exothermic. The most exothermic hydration 3CaOAl2O3 is followed by that of 3CaOSiO2, and then finally 2CaOSiO2 4CaOAl2O3Fe2O3.


function plaster Plaster or Gypsum is generally added to the clinker to regulate the setting time. Their presence makes the setting is completed in about 45 minutes. Plaster reacts with tricalcium aluminate to form an expansive salt called "ettringite '.3 CaOAl2O3 + 3 (CaSO42H2O) + 26H2O → 3CaOAl2O33CaSO432H2O


Modules Modules are characteristic values \u200b\u200bof each cement or lime, which allow to know in what capacity are, in percentage terms, the various components in the final product. For Portland cement holds: Hydraulic module


silicates Module Module Module students silicic


Cementos Portland
special
special Portland cements are cements that are obtained in the same way that the Portland, but have different characteristics because of variations in the percentage of components that form.

Portland The Portland
ferric iron is characterized by a flux of 0.64 module. This means that this cement is very rich in iron. In effect is obtained by inserting mineral pyrite ash or powdered iron. This type of composition therefore involves, in addition to the increased presence of Fe2O3, less 3CaOAl2O3 presence of moisture which is developing more heat. For this reason these cements are particularly suitable for use in hot climates. The best iron cements are those with a low limestone module, in fact they contain fewer 3CaOSiO2, whose hydration produces the greatest amount of free lime (Ca (OH) 2). Since the free lime component is mostly attacked by aggressive water, these cements, containing fewer, are more resistant to aggressive water. White Cement


Unlike ferrous cements, white cements have a high smelters module, about 10. They contain therefore a very low percentage of Fe2O3. EI White is due to lack of iron which gives it a grayish hue to normal Portland and a darker gray ferrous cement. Fe2O3 reduction is offset by the addition of fluorite (CaF2) and cryolite (Na3AlF6) required in the manufacturing stage in the horno.para lower quality type of cement that today there are 4, which are type I 52.5, 52.5 type II, type II and type II 42.5 32.5, also called the pavement) is often added an extra addition of limestone called clinkerita to lower the rate, since normally the clinker ground with gypsum type I would


blended cements cements mixtures are obtained by adding the normal Portland cement and pozzolan other components. The aggregate of these components gives these cements new features that differentiate it from normal Portland.


pozzolanic cement pozzolan is called a fine volcanic ash that lies mainly in the region of Lazio and Campania, its name derives from the town of Pozzuoli, near Naples, on the slopes of Vesuvius. Subsequently it has been widespread volcanic ashes elsewhere. Vitruvius and described four types of pozzolana: black, white, gray and red.
Mixed with lime (in the ratio of 2 to 1) behaves as a pozzolanic cement, and allows the preparation of a good mix capable of forging even under water.
This property enables the innovative use of concrete, as understood by the Romans, the ancient port of Cosa was built with pozzolana mixed with lime just before use and wash under water, probably using a tube, for deposit in the fund without diluted in seawater. The three piers are still visible, with the submerged in good condition after 2100 years.
The pozzolan is a stone of acidic, highly reactive, being very porous and can be obtained cheaply. Pozzolanic cement contains approximately:
55-70% 30-45% clinker Portland pozzolan
2-4% gypsum

Because the pozzolan is combined with lime (Ca (OH) 2), it will less of the latter. But just because the lime is the component that is attacked by corrosive water, pozzolanic cement is more resistant to attack them. On the other hand, as the 3CaOAl2O3 is present only in the component formed by the Portland clinker, pozzolanic cement wash will develop a lower heat of reaction during curing. This cement is therefore suitable for use in particularly hot climates or large castings.

Cement steel
The pozzolan has been replaced in many cases by the coal ash from power plants, smelting slag or residues obtained by heating the quartz. These components are introduced between 35 to 80%. The percentage of these materials may be particularly high, with which originates from silicate material is a hydraulic potential. This should however be activated in an alkaline environment, ie in the presence of OH-ions. It is for this reason must be present for at least 20% of normal Portland cement. For the same reasons that the pozzolanic cement, cement, steel also has good resistance to corrosive water and develops less heat during setting. Another feature of these cements is the high natural alkalinity, which renders it particularly resistant to atmospheric corrosion caused by sulphates.

quick setting cement
rapid hardening cement, also known as "prompt natural or Roman cement," is characterized by initiating the setting within minutes of its preparation with water. It is produced in a manner similar to Portland cement, but with the oven at a lower temperature (1,000 to 1,200 ° C). [2] is appropriate for smaller jobs, fixing and repairs, is not suitable for major projects because they free up time for a good wash. Although you can start setting controlled by natural retardant (E-330) as citric acid, yet if you start the approxmately FRAUD. 15 minutes (temperature at 20 ° C). The advantage is that passing approxmately. Iniado 180 minutes of setting, it achieves high Resistance to compression (from 8 to 10 MPa), so you get great benefit for rapid intervention works and final. There are rapid cement past 10 years, get superior compressive strength some concrete (graphical pass in the 60 MPa). Aluminous cement


Main articles:
aluminosis aluminate cement and alumina cement is produced primarily from bauxite with impurities of iron oxide (Fe2O3), titanium oxide (TiO2) and silicon oxide (SiO2). Additionally, lime is added or calcium carbonate. Aluminous cement, also called "cast concrete", so the oven temperature reaches up to 1,600 ° C and reaches the melting of the components. The cast concrete is poured into molds to form ingots that are cooled and ground to obtain the final product.
aluminous cement has the following composition of oxides:
35-40% calcium oxide
40-50% aluminum oxide
5% silica
5-10% iron oxide
1% titanium oxide
It referred to their real components have:
60-70% 10-15% 2CaOSiO2
CaOAl2O3
4CaOAl2O3Fe2O3
For 2CaOAl2O3SiO2
respect to silica, its presence as an impurity must be less than 6%, because the component that gives rise, ie the (2CaOAl2O3SiO2) is low hydrophilic properties (low water absorption).


hydration reactions H2O → CaOAl2O310H2O CaOAl2O3 +10 (hexagonal crystals) 2 (CaOAl2O3) +11 2CaOAl2O38H2O + H2O → Al (OH) 3 (crystals + gel) 2 (2CaOSiO2) + (x +1) + H2O → 3CaO2SiO2xH2O Ca (0H) 2 (crystals + gel)
While Portland cement concrete is a basic in nature due to the presence of lime Ca (OH) 2, alumina cement is of a substantially neutral. The presence of hydroxide Aluminium Al (OH) 3, which in this case behaves like acid, causing the neutralization of the two components and resulting in a neutral cement.
aluminous cement should be used at temperatures below 30 ° C, so cold weather. Indeed, if the temperature is above the second hydration reaction would change and the formation of 3CaOAl2O36H2O (cubic crystals) and increased production of Al (OH) 3, leading to an increase in volume and could cause the concrete cracks Portland is the best

manufacturing process









Cement Factory A wide variety of cements as base raw materials and processes used to produce, which are classified as dry and processes wet processes.
The cement manufacturing process involves four main steps:
Mining and milling of raw materials
homogenization of the raw material

Clinker Production of cement grinding.
The raw material for cement production (limestone, clay, sand, iron ore and gypsum) is extracted from quarries or mines and, depending on the hardness and location of the material, apply certain operating systems and equipment. Once extracted, the raw material is reduced to sizes that can be processed by oil mills.
The homogenization step may be wet or dry, depending on whether you use air or water currents to mix the materials. In the wet process the raw material mix is \u200b\u200bpumped into ponds homogenization and thence to the furnaces that produce clinker at temperatures above 1500 ° C in the dry process, the raw material is homogenized in yards of raw material the use of special machinery. In this process the chemical control is more efficient and energy consumption is lower, since not having to remove the water added to mix the materials, kilns are shorter and less time clinker subjected to high temperatures.
The clinker obtained, regardless of the process used in the homogenization step is then ground with small quantities of gypsum to finally get cement.









Storage cement Cement is a substance particularly sensitive to the action of water and moisture, thus safeguarding their property, they must have some very important precautions include: Immediately after the cement is received in the area of \u200b\u200bworks if bulk cement tanks should be stored in dry, water-proof designed, adequately ventilated and with adequate facilities to prevent the absorption of moisture. If bagged cement must be stored on wooden racks or floor boards, not stack them in tiers of more than 14 bags high for storage of 30 days nor more than 7 bags for storage up to 2 months. To avoid unduly cement age, after arriving in the area of \u200b\u200bworks, the contractor must use the same timing of their arrival. Do not use a bag of cement that has more than two months of storage in the area of \u200b\u200bworks, unless further testing shows that it is in satisfactory condition.

Rubbermaid Retail Stores In Ontario

CEMENT

During the visit of the visit to San Marcos we saw a building which I found most interesting the cement and its uses. CEMENT


• Definition:
is a finely powdered substance made of gypsum plaster able to form a soft paste when mixed with water and hardens spontaneously on contact with air
Cement is a material that combines the fragments detritus (sand or gravel) in some clastic rocks (sandstones and conglomerates). In general the cement of these rocks is caused by chemical precipitation, being the most common cementing substances silica, carbonates and iron oxides.
Cement is a dry powder made of silica, alumina, lime, iron oxide and magnesium oxide, which hardens when mixed with water.
· Properties
physical and chemical properties of cement:
cements belong to the class of materials called binders under construction, such as air lime and plaster (not hydraulic), the cement hardens rapidly and reaches high resistance, that due to complicated reactions combination of lime - silica. Ex
Chemical analysis of cement: 63% CaO
(Cal)
20% SiO2 (Silica)
6% Al2O3 (alumina)
3% Fe2O3 (Iron Oxide)
1.5% MgO (magnesium oxide)
K2O + 1% Na2O (Alkali)
2% Loss on ignition 0.5% insoluble residue

2% SO3 (sulfur dioxide)
Residue 1% CaO (lime free) Chemical characteristics


_Módulo
_Compuestos flux on ignition side _Perdida

insoluble _Residuo

Physical
_Tiempo
_Superficie setting specific _Falso
volume setting
_Estabilidad _Resistencia
mechanical air

_Contenido _Calor
hydration of cement
· Types
PORTLAND CEMENT: Portland cement without addition, is the product obtained by spraying a mixture clinker and calcium sulfate with water (hydrated gypsum).

CEMENT STEEL: The product obtained from the joint mixture of clinker, basic slag and granulated blast furnace cast. Granular basic slag, is the product obtained by quenching the melt non-metal, which results in the treatment of iron ore in a blast furnace. If you have less than 30% of basic slag, Portland cement is called Iron and Steel.

CEMENT WITH ADDED A: It is the product obtained by grinding together with clinker, and plaster aggregate type. The aggregate type A is a mixture of substances, consisting of a calcium-clay material, which has been calcined at temperature above 900 º C, and other materials based on oxides of silicon, aluminum and iron. If it contains less than 30% of the aggregate type is called Type A Portland Cement, and if you are between 30 and 50% is called Cement Type A. CEMENT

PUZOLÁMICO: The product obtained by joint milling of the clinker, pozzolana and gypsum. The pozzolan is silica-alumina material, but has no binding properties by itself, develops when finely divided and in the presence of water, chemical reaction with calcium hydroxide at room temperature. PORTLAND CEMENT

:
hydraulic cement produced by pulverizing clinker consisting essentially of hydraulic calcium silicates usually containing one or more of the forms of calcium sulfate as an addition during milling.

PORTLAND CEMENT TYPE:
Type I normal Portland cement is intended for general concrete work, when they do not specify the use of another type. (Buildings, industrial structures, housing complexes) releases more heat
hydration than other types of cement.
Type II: moderate sulfate resistance, portland cement is intended for general concrete works and works exposed to moderate sulphate action is required or where moderate heat of hydration, where be specified. (Bridges, concrete pipe)
Type III: High early strength, as when you need to get the concrete load as soon as possible or as needed stripping a few days of discharge.
Type IV: low heat of hydration requires that there should be no expansion during setting.
Type V: Used where high strength is required the concentrated action of sulfates (channels, culverts, port works)

TYPES Portland pozzolan cement, Type IP Portland pozzolan
: Where the addition of pozzolan is 15 -40 % of the total. Portland pozzolan
Type I (PM): Where the addition pozzolan is less than 15%

Portland pozzolan type Q: Where the addition of pozzolan is over 40%


SPECIAL CEMENT-Portland Cement White Masonry Cement
-
-aluminous cement-Cement

compounds
CEMNETOS RECOMMENDED THEIR EFFECTS ON CONCRETE
The conditions to be taken into account to specify the concrete cement suitable and appropriate for selecting a play, can be determined by the timely investigation of two aspects:
1) the characteristics of the structure and equipment and procedures required to build it.
2) the exposure conditions and service Specifically, given the characteristics of the environment and the means of contact and foreseeable effects resulting from the use for the structure.
There are several aspects of the behavior of concrete in fresh and hardened, which can be modified by using an appropriate cement, to adapt to the specific requirements given by the conditions of the work. The main characteristics and properties of concrete that can be influenced and modified by different types and grades of cement are: Cohesion and manageability

fresh concrete slump loss and bleeding

Settlement Setting time
strength Acquisition Concrete

hardened heat generation resistance to attack by sulfates
Dimensional Stability (volumetric changes)
Chemical Stability (cement-aggregate reactions) PRODUCTION

manufacturing _proceso
REMOVING QUARRY

In the stone quarries limestone is extracted and clays by drilling and blasting with explosives.












CRUSHING the quarry material is fragmented into crushers, hopper which receives the raw material, the effect of impact or pressure is reduced to a maximum size or half an inch.












raw mill is performed through a vertical steel mill, which grinds the material by the pressure exerted by three roller bearings rolling on a turntable grinding . They are also used for this phase horizontal mills, within which the material is pulverized by means of steel balls.











BAKING
is the core of the process, which employ large kilns within which to 1.400 ° C transforms the raw meal in clinker, which are small dark gray modules 3 to 4 cm.











CEMENT MILL
The clinker is ground by steel balls of different sizes in its passage through both houses of the mill, adding the plaster to lengthen the time the cement. BAGGING


Cement is sent to storage silos, from which is extracted by pneumatic or mechanical systems, being transported to where it will be packed in paper bags or bulk supply directly. In both cases can be shipped by truck, rail or boat chutes.

Monday, June 9, 2008

Saran Wrap To Lose Inches

Taller de Geometria molecular


Workshop molecular geometry




This is the molecular model of vitamin C or ascorbic acid. Was presented at the workshop molecular geometry we do, under the direction of Professor Martha Mosquera , the different working groups we discussed our jobs, can observe well infinite number of forms assumed by molecules depending on their position atom. It was great, pity it's over this semester because we will turn away from our friends and teachers and that's good because we relax. to the next half, friends, good luck.

Vicky In this photo , Edwin and me.

Podiatrist Toronto Walk-in Clinic

udus




This is a percussion instrument originating in Nigeria that is done in ceramic. It can be done in different techniques such as hollow, for plates, by the technique of Truffles or as performed in my studio potter's wheel.
It was created by chance one might say, this type of vases were used to transport water from rivers to homes, have much capacity hold water.
History says they tried to make an extra mouth to drain the water and there's the secret of the sound of this beautiful instrument. Today
its original form it was deformed to achieve different sounds, some as I make are stoneware which means that their sound is more acute stroke and may contain water which changes the sound as the amount of water.
can be made in many sizes and shapes provided with two holes well "tuned" by this I mean that when I make the holes in the playing to get the sound I want.
The udu is decorated with oxides and small green enamel decorations.

Sunday, June 8, 2008

Mucinex D Can Cause Erectile Dysfunction



Introduction

Each space that is our body is so perfectly designed to live, that is fascinating to discover how it works as a great engine, which has its parts fully engaged and willing to fulfill their duties. But it is still indescribable, the feeling we have when it is noted that each of these parts, does not have a system functionally independent of each other, but depend on each other in their properties and features to desarrollarse.En 1912, the then unknown vitamins, were discovered and began to be classified. Discovered, yes, not because they did not exist, but because no one knew of their qualities and capabilities. Today
and after years of study we can say that vitamins are involved in each of the body's metabolic processes that give us nutrients but their role is not to provide energy, they help us to induce our body to produce enzymes that break down foods and make them the elements that provide nutrients.
is to take into account that vitamins are not stored in our system for long periods of time, are water soluble, one of the reasons why the body is discharged quickly.
Its chemical structure resembles that of glucose (in many mammals and plants, this vitamin is synthesized from glucose and galactose). Also called ascorbic acid, and calling on all chemicals that have the same characteristics. Features


The functions of vitamin C are based on their redox properties, why is an important factor in metabolism. Facilitates release of iron from transferrin (Protein that carries iron in the blood THROUGH) and of ferritin (a major storage form of iron). Collaborates in the formation of collagen, important for the formation of fibrous tissue in the body (skin, connective tissue The dentin matrix osteocartílago and tendons), plus the formation of this protein is the importance that has the vitamin and healing of wounds and fracturas.Actúa as enzyme cofactor and as a cellular antioxidant. Only the need humans, monkeys, guinea pigs and some fish. It is one of the vitamins sencilla.Participa structure also in the formation of some neurotransmitters serotonin, its concentration decreases in situations where there is accumulation of stress when there are high levels of adrenal cortex hormones. Also collaborating on the immune system defense against germs and you cancerosas.Normalmente cells are attributed healing powers, such as the common cold, but is not recommended to consume it in excess.

Chemical Composition of vitamin C

is a white substance, stable in dry form is easily oxidized which is accelerated by exposure to heat. In addition vitamin C is called to all compounds containing ascorbic acid.
Fig. 1 Chemical structure of ascorbic acid


Its main base is ascorbic acid, thus defining that vitamin C is derived from the hexose, synthesized from glucose and galactose. Some primates and other animals lack the enzyme that helps the catalyst for vitamin C, so they should consume. Absorption



species can not synthesize passively absorb. The oxidized form of ascorbic acid, dehydroascorbic acid which is subsequently reduced to scurvy. For transport, dehydroascorbic acid is oxidized and remains in the cells is the way in which mobilizes vitamin C. Lack


vitamin C deficiency can cause scurvy in adults and children is called syndrome Moeller-Barlou disease. Addition results in the malformation, and remaining in the formation of collagen and the delay in the production of osteoid with impaired function is noted osteoblastica.Además capillary permeability and constant bleeding, also note the lack promptly in observation skin, forming an outbreak in the dermis. All this a result of scurvy.
Toxicity

The discomfort can occur when taking high doses of vitamin C, are gastrointestinal distress, however it is believed that also can cause kidney stones. It is of note that the excess of ascorbic acid due to its solubility, can be eliminated in the urine.

Best Screen For Sceened Porch

Geometria Molecular


The ascorbic acid consisting of 6 carbons, 8 hydrogens and 6 oxygen.
The ascorbic acid form intramolecular bonds that contribute to the molecular stability.
Fig. 2 Form geometric ascorbic acid