This
and its uses, I got more and more amazed by the way construction professionals deal
Therefore most likely the average user
Regardless of the origin of the pozzolan, make sure that the maximum particle size
The silica fume particle consists mainly of ³vitreous²
Certain impurities such as iron, magnesium, and calcium (note:
with RHA, but it isn¹t clear why, and why others had poor to disastrous results. The main constituent material in SF is silica
structural strength over time. accepted value for the specific gravity of any vitreous silica. A "pozzolan" is defined as "a siliceous
Ideally, there should
Reduced Sulfate Attack: Pozzolans tie up free lime that otherwise could combine
The first uses of pozzolans were for lime as a construction material. Pozzolans include a broad category of materials, both naturally occurring and by- products of various modern manufacturing processes but can be generally defined as being mainly siliceous or silico-aluminous material that will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds having cementitious properties. requirement. You can only expect to produce a superior
CONTROL OF ALKALI-AGGREGATE REACTION Alkalis can come, not only from cement, but also from Fly ash is finely divided residue from the combustion of coal. Reduced Efflorescence: Pozzolans chemically bind free lime and salts that
at relatively low temperatures. trash and the other man¹s treasure), Quote: ³U.S. typically more than 90% of amorphous silicon dioxide. Very low Chloride Ion Diffusion: Pozzolans make concrete more resistant to
with sulfate to create destructive expansion. can be accomplished by placing the clay in the water and left to soak for a day or
Dynastone gained national recognition
above. of fly ash, obviously there is also a market and good use for this quality-enhanced
the effects of alkali silica reaction. 3-1). On the other hand, 1% doesn¹t seem to
That in turn puts the responsiblity on the construction professionals to thoroughly
Types of Pozzolan Pozzolans commonly used in modern concrete construction include coal fly ash (aka pulverized fuel ash or … the bulk density is only about 200 - 300 kg/m3. It should be noted that to overcome the above shortcomings, sometimes FA and/ or
It can - but does not always - result
Apart from MS600 which is very fine, the other reactive pozzolans contain significant amounts of aluminium which may be a key factor in determining a pozzolan’s reactivity. Contents:What is pozzolana or pozzolanic material?Types of pozzolana materials … generates less heat, resulting in reduced thermal cracking when pozzolans are used
high-quality concrete - like FC/ECC - have a look at enhanced pozzolans
matter at all where the ash comes from, as long as it can produce the benefits listed
able to construct those sturdy buildings we still admire today. The application of natural pozzolans in concrete structures is either in the form … Commercial
construction because of its high acid-resistance. Chemical admixtures - Accelerators, Retarders, Water-reducing agents, ... A pozzolan is a material which, when combined with calcium hydroxide (lime), exhibits cementitious properties. and FeSi-75% condensed silica fume has proven to work effectively, while mixtures
This increased cohesiveness could however increase the
removal from fly ash. force wind and rain (75 mph), it resisted water penetration for four hours. Related terms: Binders; Compressive Strength; Silica Fume; Metakaolin salt water (seawater). The release of these fine pozzolan
like fly ash), will tend to produce a harder mortar, closer in its characteristics
silica fume (normally in the form of a slurry) is more effective. and seal the concrete, they have many other beneficial features you will realize
The modern furnaces for rice hulls are probably
This publication pursues no commercial interest. is 10 µm or less, or that at least more than 90% of the particles fulfill this
And for some reason
Some people even claim that it is superior to silica fume (see below). Note: If the fly ash has high calcium content, it should
Therefore I feel
cementitious compounds (calcium-silicate hydrate gel, calcium-alumino silicates,
The lower the better! you purchase them or add them to the mix. form of ASR when he talks about it, but the desired reaction between pozzolan and
Therefore permission is granted
and in reality always happens. of bleeding and segregation. fume particles is 2.2 to 2.5. Unfortunately that may not always be true with the kind of ash you would like
contact results in enhanced bond strengths. and wet scrubbing are used. makes it clear that the pozzolan has to be very fine (<10 µm) to ensure
compounds on the inside. anybody wants to experiment with it, he should make sure that it is either already
See more. Waterproofing admixtures have a broad range of applications in construction and infrastructure development. as ³pozzolans². cases up to 300Mpa. http://www.silicafume.org/
(SFC) normally incorporates a water reducing agent or superplasticiser. but unfortunately it reacts too slowly, due to its reduced total surface area. and flexible, while the hard-burned materials, for example PFA (pulverized fuel ash,
good if user groups like ³ferrocement² could conduct research into this matter. the properties of lime, the most adventurous additives have been used. for the water loss on the surface, due to evaporation. amount of condensed silica fume in the concrete mix. basin to improve abrasion erosion resistance; it has also been employed as an essential
The term ³pozzolan² is derived from the name of the town Pozzuoli,
... For example, different pozzolans and slag are available in different regions. The more carbon that is still
Higher Strength: Pozzolans continue to combine with free lime, increasing
an average. Pozzolan concrete is also more
prepared, and to distinguish which ones are suitable for their purposes. Let¹s have another look at this definition: A pozzolanic material has to contain reactive silicates or
just like any other pozzolan - is not an inert filler, but plays an active role in
purposes, and as long as due credit is given to the author. concrete. faster strength gain, while Class F is produced from burning bituminous coal and
Types of Admixtures of Concrete. Materials" by Malhotra and Mehta (Gordon and Breach Publishers, 1996). Other natural pozzolans, such as volcanic ash, occur naturally. of plastic shrinkage and cracking that appears when the bleeding water cannot compensate
Types of Pozzolanic Materials Pozzolanic materials can be divided into two categories according to the source of origin, natural and artificial. other points of research they might consider ultrasonic conditioning and wet scrubbing
should alert the future user. This video explains what Portland Pozzolana Cement (PPC CEMENT) is and important properties and uses. Otherwise you might encounter strange problems and never know the cause. cementitious properties. the lime from the cement-hardening process is also an ³ASR², though a much faster
That is the case if the lime only has aggregate or large pozzolanic
Silica fume is a waste product of the silicon metal industry, and is a super-fine
http://www.geocities.com/CapeCanaveral/Launchpad/2095/pozzolan.htm
Among them
But as the ashes of organic origin, like ³pulverized fuel ashes²
well suited for many applications, including:
times the mass of cement, besides making the same amount of concrete harder than
Type II and Type IIA contain tricalcium aluminate, but no more than 8%. Rice hull ash (RHA) is frequently referred to as a pozzolan superior to fly ash. the subject, mostly the members of the discussion list about ³ferrocement² (FC). property, but will in a finely divided form - and in the presence of moisture - chemically
Here are some useful links to start an in-depth investigation
The impermeability of SFC is higher than that of similar concrete without SF. How to name the new cement blends. nitrate attack. For this reason, silica fume concrete
Fly ashes that comply with ASTM C 618 for mineral admixtures in portland cement concrete
contents (<1%). turn crystalline, rendering them useless as pozzolans. into pozzolans:
course they would prefer to do that for a profit. Italy. Gypsum, in addition to ettringite,
Both natural and artificial (man-made) materials show pozzolanic activity and are used as supplementary cementitious materials. Fly ash is 66-68% glass, on
These gels are expansive, and that
C 3 A. Pozzolanic materials do not change the types of hydrates that form from the hydration of C 3 A. the concrete, they have many other beneficial features you will realize the moment
too! depends!² One definition for ³ASR² is ³alkali-sulfate reaction². or big pozzolanic particles, as well as the slow reaction between lime and silica,
there is hardly any in-depth information available in the public domain, though there
Resistance to Freeze-Thaw: As water doesn¹t penetrate the hardened concrete,
without any loss of strength. Improved Water Tightness: The formation of expansive gels effectively seals
portland cement hydrates) and alkalis to form cementitious compounds.
Mazama volcanic ash as a natural pozzolan and explored innovative uses of the material for roadway improvement. Because the extreme fineness(!) demand. It is commonly known as PPC cement. (i.e. There are many types of building lime on the market.
(PFA, mostly coal ashes) and rice hull ashes (RHA) also show enhancing properties
Pozzolan refers to any of several silicate materials that produce cement-like materials when they react with calcium hydroxide. Since the fly-ash-bearing
possible disastrous pressure build-up and a slow destruction of the concrete. silica particles. most of the gels will be produced after the hardening of the cement, resulting in
counts are the properties, primarily particle size and purity (absence of carbon),
"Our team of scientists discovered that
can create efflorescence. http://www.silicafume.org/general-concrete.html
Class C fly ash must replace at least 25% of the portland cement to mitigate
effort, responding better to vibration to fill forms more completely. That in
water penetration and leaching. results similar to ground burnt clay bricks. Though difficult (and expensive) to handle,
Silica fume powder collected
As little as 3% of coal in the cement mix (without aggregates)
The fly ash is the first type of admixtures that we are going to discuss. be used correctly. http://concreteproducts.com/ar/concrete_news_developments_27/
are copies of this company¹s press release. Given the present situation, my hope is that this publication
The relative density of typical silica
2. Applying silica fume in concrete fertilizer storage silos effectively reduced calcium
of pulverized coal in electric power plants. creates a lubricating action when concrete is in its plastic state. rice hulls has improved a lot, but that doesn¹t mean that each and every plant that
can also be produced during sulfate attack and is capable of producing expansion. etc. For more info about this process go to http://www.isgresources.com/
but they can do great things for you if you select the right product and apply it
can be used as a cement replacement, ranging from 20-35% of the mass of cementitious
could negate the benefits of adding silica fume. The other meaning of ³ASR² is ³alkali-silica reaction². Artificial Pozzolanas: Under this group following substances are grouped: However, if the mixes contain calcium hydroxide, C-S … has also become a pozzolan. they don¹t seem to realize that any potion, magic or not, has to be carefully produced
Pozzolan blended ASTM type I cement (API Class B or C), which is resistant to chlorine and sulfate attack and at the same time develops strong cement matrix, can be used, for example. Portland-pozzolan cement based on Portland or IS cement, plus 15%–40% pozzolans of unspecified type. than one µm in size. For more info about fly ash go to: http://www.iflyash.com/whatisflyash.htm. The aggregate in the concrete is basically silica,
RHA are also added to the concrete, together with SF. curing measures should be taken immediately after placing the concrete. ash. Dynastone pipe has an estimated life of 100+ years and can be used anywhere in sewer
destroy it. Now let me describe more about the artificial pozzolans and properties of mineral types of admixtures. Given this mineral origin, some purists consider only volcanic ashes, pumice, tuffs,
required compaction energy. different qualities of ash, categories have been created for coal-derived fly ash. to use as a pozzolan. into account. Physical Characteristics. - especially important in hot weather. In combination with portland cement, Class F fly ash can be used as a cement
conventional concrete at 56 and 90 days. without pozzolans, less voluminous structures are able to bear the same load.
No claims are made regarding accuracy or completeness, nor are there any other claims. The resulting gels
Portland Pozzolana cement is integrated cement which is formed by synthesising OPC cement with pozzolanic materials in a certain proportion. 29. In an attempt to the classify
Reduced Heat of Hydration: The pozzolanic reaction between pozzolan and lime
mortar (20 psi strength) resists water for five seconds under the same conditions,
who would first analyze the tap or well water he is going to use? that otherwise could lead to rock pockets and blemishes. Tests have proven that one part of silica fume can replace up to 3-4 parts of cement
to replace portland cement. investigate pozzolans and to demand higher quality standards for them, so they can
Realizing that the quality of the average fly ash often leaves much to desire,
http://www.pensacolatesting.com/dirtknocker/beta.htm
the specific value. Pozzolans also serve to densify and reduce the permeability of concrete, which helps to make it more resistant to deterioration and swelling associated with various exposure conditions. If after reading this summary you go out and buy ³any old² pozzolan to improve
pozzolan (copy of press release). mostly designed to produce as little NOx emission as possible. All of the below benefits apply to fly
silica fume², to distinguish it from other forms of silica fume. Requirements of natural pozzolans are specified in … millions of tons of fly ash annually, which is usually dumped in landfills.². Combining SF with the appropriate aggregates and water-reducing agent can produce
a timely reaction between the lime that is given off as the cement hardens, and the
like rice hull ash could be treated in the same manner. Besides that, silica fume -
There is an additional ASTM requirement to identify the type and amount of each component blended with the clinker. etc.). and a loss in strength. Increased Durability. as a ³finely divided powder², one of the requirements to be a good pozzolan. Reduced Slump Loss: More dependable concrete allows for longer working time
be no weight loss at all. At higher temperatures the glassy particles would
The general definition of a pozzolan embraces a large number of materials which vary widely in terms of origin, composition and properties. For example, coal from the east coast tends to contain sulfur,
this summary. Class F fly ash (see ASTM C 618) readily reacts with lime (produced when
and high silicon content,
with this subject. when mixed with cement or lime, most of the times the origin is irrelevant. A Growing Scarcity of Waste Pozzolans Driven by the need to dispose of the ash scrubbed from the stacks of coal-fired power plants, the power industry discovered the residual ash had similar chemistries to natural pozzolans—a sort of artificial pozzolan. slowly react with the aggregate, producing gels. Natural pozzolans need further grinding and calcining to activate them. product, and that should be food for thought. The technology for burning
Vesuvius and is the place where the Romans more than
Spherical Shape: Fly ash (FA) and rice hull ash (RHA)
burns these hulls is using the latest technology. Last of all, an apparently insignificant detail that came to my mind while writing
power plants produce
Phoenix Class F Fly Ash. not necessarily be a suitable pozzolan. RHA does not come by nature
come in two classes: Class C is produced from burning sub-bituminous coal and has
For that the hulls
ash and rice hull ash, and most of them to silica fume as well. The mere fact that I¹m just speculating here - due to the lack of precise info
It has a specific gravity of about 2.20, which happens to be the
Cement gives off lime as it hardens and this lime will inevitably react with silica
Mortar. Natural Pozzolans are highly effective (25 %) When slag is used, replacement quantities of 50% or more are common. As this is basically calcined clay, it should produce
Two types are distinguished: types IP and P, for general use, with subtypes IP (MS), IP (A), and IP (MH) as before; and type P with less early strength, with the same subcategories, plus type P (LH) with low hydration heat. cement. your concrete, most likely you won¹t obtain the expected great results. Properties of (problems with) fresh concrete with silica fume:
two. freezing can¹t cause destructive expansion. but not CaSi) have shown to increase this value. The undensified silica fume is almost as fine as cigarette ash and
Reduced Bleeding: Fewer bleed channels decreases porosity and chemical attack. From: The Fundamentals of Corrosion and Scaling for Petroleum & Environmental Engineers, 2008. finely ground or that he can use a suitable mill and screen. basically refers to the carbon content in the ash. will prevent the hardening of the concrete. would have to be burnt with the minimum possible amount of air (oxygen). Pozzolans. hardens too much), so they won¹t cause too much pressure build-up in the hardened
After that it should be finely screened to remove any clumps and foreign matter. It gets with … Under conditions of fast evaporation,
Otherwise even a relatively small pressure (load) on the concrete could
Also make sure that you are dealing with a product with a low carbon
and applied to accomplish the desired result. Reduced Segregation: Improved cohesiveness of pozzolan concrete reduces segregation
Improved Finishing: Sharp, clear architectural definition is easier to achieve
Fly ash, ground granulated blast-furnace slag, silica fume, and natural pozzolans, such as calcined shale, calcined clay or metakaolin, are materials that, when used in conjunc- tion with portland or blended cement, contribute to the properties of the hardened concrete through hydraulic or pozzolanic activity or both (Fig. Hence, their artificial alternatives were found out. Anything else is an invitation for trouble. particles are almost totally spherical in shape, allowing them to flow and blend
Given the potential of pozzolans in general - and RHA in particular - it would be
http://www.sefagroup.com/cbo.htm
Dense pozzolan concrete helps keep aggressive compounds
silica fume is generally a very effective pozzolan. an important improvement to the conventional froth flotation process used to remove
starting point for experiments. This one is never
of FeSi-75% with FeSi-50% and FeSi-75% with CaSi have proven to be ineffective. though the most important ones are probably sulfur and salt (NaCl). Ball Bearing Effect: The "ball-bearing" effect of FA and RHA particles
The smaller, already
particles from the carbon improves the recovered-carbon quality and adds a desirable
that it has been issued U.S. Patent No. from waste gases and without any further treatment is generally called ³undensified
There are quite a few substances that can negatively affect your concrete,
at least one company has been working on methods to improve it. are ground burnt clay bricks, bone ash, animal blood, and clay. be a problem at all, so the gap is pretty narrow. Different types of admixtures are used for different parts of a structure namely the roof, basement or walls, as well as for different locations, climatic conditions, and purpose of the structure. hour. that most of the gels are formed before the hardening. It happens when ettringite is produced, as a result
will occupy the voids in the still elastic concrete, sealing them from water. Chemical composition of SF varies depending on the nature of the the manufacture
Natural pozzolans fall into two main category types: raw and calcined. should be a lot of proprietary information. Note that both the quality of the removed carbon (now a valuable commodity) and
component to the processed fly ash.". Ramachandra, Feldman, Aitcin, p. 9-10. Present day concrete pipes typically have a life span of 50
alloys or other silicon alloys. origin - might be too big or contain too much carbon. The fly ash is collected by an electrostatic precipitator. concrete if your pozzolan fulfills these two requirements. with typically less cost per volume. that might otherwise combine with silica from aggregates, which would cause potentially
Though by now pozzolans, particularly fly ash, have become pretty
The only way to achieve this is including very fine (<10 µm) and reactive
I compare pozzolans to grease. The types of Pozzolanic blended materials covered by this specification are an intimate and uniform blend of two or more of the following materials: Type F - Class F fly ash; Type C - Class C fly ash; Type CKD - Cement kiln dust; Type S - ground granulated blast furnace slag; Type SF - Silica fume; Type M - … The combination of Si
one. has hardened. even this is normally still too big, and they specify a maximum of 10 µm. Minkara, P.E., process co-inventor. Natural Pozzolan Types. Artificial pozzolans can be produced deliberately, for instance by thermal activation of kaolin-clays to obtain metakaolin, or can be obtained as waste or by-products from high-temperature process such as fly ashes from coal-fired electricity produc… In combination with portland cement, Class C fly ash
In
and the results! in almost the total calculated volume of water needed for the concrete mix. is betting on good luck when purchasing this product. like for extremely delicate applications only demineralized or distilled water should
The construction professional only refers to the unwanted
"Condensed Silica Fume in Concrete", Malhotra,
the moment you add them to the mix. The non-hydraulic cement doesn't require water to get harden. the concrete. When using pozzolans in mortars, the softer pozzolanic materials (like brick dust
SFCs both with and without superplasticiser. to that, Class C fly ash may also exhibit hydraulic (self-cementing) properties. To compare to the hydraulic cement types, some of the Type II cements meeting the standard for the moderate heat of hydration type. is welcome as long as they just fill the voids with a slight pressure thus avoiding
will help the construction professional to have an influence on how pozzolans are
Also be produced during sulfate attack and is capable of producing expansion Type IIA contain tricalcium aluminate but... Infrastructure development the problem starts when too large a volume of gels produced. Concrete if your pozzolan fulfills these two requirements place in durable concrete.... F - yielding higher strengths than conventional concrete at 56 and 90 days ( 75 mph ), the produced. Artificial pozzolan and explored innovative uses of pozzolans so the time may not used! Acid, soft ( lime-hungry ) water, and they specify a of. The relative density of typical silica fume concretes of up to 300Mpa have been achieved some! The hydraulic cement types, some types of admixtures he is going to use must fine! ( SiO2 ), 2019 specific gravity of about 2.20, which ties up lime! Life of 100+ years and can be present in Our water for the mix good luck purchasing... Explored innovative uses of the removed carbon ( now a valuable commodity ) and (... Acid, soft ( lime-hungry ) water, and they specify a maximum 10. By synthesising OPC cement with pozzolanic materials in a certain proportion been used least 25 of., they contain carbon both questions is, ³it depends! ² one definition for ³ASR² ³alkali-sulfate. Definition for ³ASR² is ³alkali-sulfate reaction² you might encounter strange problems and never know the cause during attack. Lost their popularity due to the hydraulic cement types, some types of admixtures of concrete may to... Permeability and a loss in strength produce results similar to ground burnt clay bricks, ash! For fly ash mild types of pozzolans, soft ( lime-hungry ) water, and seawater high content... The concrete a very effective pozzolan alkali-aggregate reaction a chemical analysis of a commercially silica... Fewer bleed channels decreases porosity and chemical attack ( man-made ) materials show pozzolanic activity and are less... It is important that the carbon content in the hardening of the material for roadway improvement integrated. An apparently insignificant detail that came to my mind while writing this summary next two paragraphs are copies this! Known artificial pozzolan and results from the burning of pulverized coal in electric power plants any loss of.... The Romans more than 8 % slag are available in different regions the Romans than... Yielding higher strengths than conventional concrete pozzolans and properties aggregate or large pozzolanic particles to react with the kind ash... Micro-Spherical pozzolan less than one µm in size story of one man¹s trash the., it should not be ideal, it should not be used in sulfate exposure or hydraulic applications spherical! Destructive action is lessened should alert the future user after placing the clay in the field insist that this! Ash are improved seem to be a lot of proprietary information, composition and properties pozzolans! ( 75 mph ), it should be finely screened to remove any clumps and foreign matter precipitator... One definition for ³ASR² is ³alkali-sulfate reaction² as many other unwanted substances can done. Distilled water should be finely screened to remove any clumps and foreign matter particles turn! And decreases permeability this improved pozzolan ( copy of press release pozzolans in the hardening of the benefits... Years ago mined the ashes deposited by the occasional eruptions of this press! Concrete reduces segregation that otherwise could combine with sulfate to create destructive expansion blemishes... Modern furnaces for rice hulls are probably mostly designed to produce a superior if! Improve carbon removal from fly ash is finely divided, Highly reactive materials of volcanic tuff or ash used concrete... Of concrete also make sure that you are dealing with a product with a low carbon (! Dynastone shows how pozzolans can protect against strong acids durable types of pozzolans construction coal... Improved cohesiveness of pozzolan concrete is also more resistant to salt water seawater. Ash are improved, freezing can¹t cause destructive expansion, the more weight you will lose upon burning ash! Typically used as a pozzolan superior to silica fume concrete ( Fifth Edition ), 2019 Type of admixtures we. Know the cause volcanic tuff or ash used in sulfate exposure or hydraulic applications content the. Analysis of a chemical analysis of a pozzolan self-cementing ) properties resistance to Adverse reactions.