Pozzolan on Pagan Island

THE HIGH QUALITY NATURAL POZZOLAN
ON PAGAN ISLAND

INTRODUCTION

MT. Pagan of the Northern Mariana Islands in the western Pacific Ocean, erupted in May 1981. The eruption deposited over 200 million tons of natural pozzolan, which blankets about 5 square miles of the northwestern slope in vast drifts ranging from 30 ft. to over 100 ft. deep.

Random samples were collected throughout the deposit. Numerous test reports have confirmed that the whole deposit is of uniformly high quality, contains no carbon and virtually no sulfur trioxide, and is free from any contamination. In the shape of porous rocks, this natural pozzolan can be easily ground into very fine power and can quickly react with lime.

After thorough testing, professor Anders Henrichsen of the Technical University of Denmark gave the following recommendation:

" The material can be characterized by its uniformity, the high reactivity which equals that of OPC, and its contribution to the durability of concrete, particularly such which are exposed to marine conditions of sulfate rich environments. "

The high quality natural pozzolan on Pagan Island is an ideal concrete strengthening additive.

HISTORY OF POZZOLAN

There are 1282 volcanos in the world considered to have been active in the past ten thousand years. Only 3 volcanoes deposited high quality natural pozzolan.

The first one is Santorini Volcano, Greece, which erupted during 1600 BC ~ 1500 BC. Mt. Vesuvius, Italy, is the second volcano which erupted in AD 79. Pozzolan was names after the town of Pozzoli where it was deposited. The third, Mt. Pagan, is the only one which has erupted in modern times.

Scientists have proven that the ancient Greeks began to use natural pozzolan-lime mixtures to build water-storage tanks some time between 700 BC and 600 BC. This technique was then passed to the Romans about 150 BC.

According to Roman engineer Vitruvius Pollio, who lived in the first century BC:

" The cements made by the Greeks and the Romans were of superior durability, because neither waves could break, nor water dissolve the concrete. "

Many great ancient structures, such as the Colosseum, the Pantheon, the Bath of Caracalla, as well as other structures that are still standing in Italy, Greece, France, Spain and the islands in the Mediterranean Sea, were built with natural pozzolan-lime mixtures. Many of them have lasted two thousand years.

After the invention of Portland cement, natural pozzolan was used concrete strengthening additive to improve characteristics, such as durability, compressive strength, chemical resistance, hydration heat, permeability etc.,

In Europe and the USA, there have been numerous high rise buildings, highways, dams, bridges, harbors, canals, aqueducts and sewer systems built with natural pozzolan-cement mixtures.

Due to the limited supply of high quality natural pozzolan, in the last 30 years, the USA and European countries were compelled to lower their quality criteria so that waste materials such fly ash could be used as substitute for natural pozzolan.

FLY ASH vs NATURAL POZZOLAN

Known to be much inferior to natural pozzolan, fly ash normally contains excess amounts of carbon dioxide and sulfur trioxide, which are trapped inside the spherical envelope while coal powder burns. As the waste of coal-fired power plants, fly ash is inconsistent in chemical composition.

When fly ash cement is hydrated, the envelope covering each fly ash particle prevents or slows down its reaction with calcium hydroxide during cement curing period. When the envelope breaks in a later stage, destructive DEF (Delayed Ettringite Formation) occurs around the partly reacted fly ash particle.

Fly ash is also known to be inferior to natural pozzolan in the control of alkali-aggregate reaction, because the envelope slows down its reaction with calcium hydroxide which is produced by hydration of Portland cement. The envelope also slows down the silicate inside the particle to react with the alkali in the cement.

Natural pozzolan is formed when silica rich magma meets with a large quantity of under ground water in the volcano conduit. Under high pressure and high temperature, water in steam form dissolves into the magma mixing with the dissolved carbon dioxide and sulfur gases. When this magma reaches the earth's surface, it blows off the top of the volcano cone, Because the pressure is suddenly reduced, all the gases inside the magma are released and the magma, blown up like pop-corns, falls to ground then cools off into small porous rocks.

After being ground into a find powder, natural pozzolan can quickly react with calcium hydroxide and can trap the alkali inside the cement paste. Thus, it helps to form a denser paste with almost no alkali aggregate reaction at all.

GRANULATED BLAST FURNACE SLAG vs NATURAL POZZOLAN

Good quality granulated blast furnace slag is a good cementitious material. But, in order to produce good quality slag, steel plants have to sacrifice the quality and some quantity of their steel products. Therefore, good quality slag is very hard to find.

Uniformity is another problem. The mixture of the left over from burning the iron ore, lime stone and coal, can vary from ton to ton in chemical composition.

Water cooling may help to purify the slag, but still, there are certain quantities of gases such as carbon dioxide, carbon monoxide and sulfur gases trapped inside the slag.

Slag cement is well known for its slowness in developing its compressive strength. Adding expensive silica fume can accelerate the development, but the result is still not very satisfactory.

Containing 30~40% silicate and about the same amount of calcium oxide, slag is far inferior to natural pozzolan in reactivity with the calcium hydroxide produced by cement hydration.

The natural pozzolan on Pagan Island is unique in its uniformity and high reactivity.

BENEFITS AND ADVANTAGES OF THE NATURAL POZZOLAN ON PAGAN ISLAND
Substituting 30% Portland cement with natural pozzolan on Pagan Island will accomplish the following:

1. Lithification
Once natural pozzolan-lime mixture is hydrated, pozzolanic reaction begins and will continue for many years. Eventually, the mass will reach a complete LITHIFICATION, forming a rocky material similar to plagioclase with some content of magnetite.

The compressive strength and flexural strength will continue to increase for a long time. This unique characteristics is one of the main reasons why many great ancient structures have lasted for over two thousand years.

2. Autogenous healing
Another unique characteristics of Pagan's natural pozzolan is its inherent ability to heal or re-cement cracks within the concrete by means of its continuation of pozzolantic reaction with the calcium hydroxide freed from the hydration of Portland cement. This autogenous healing mechanism mends the structures by filling up most of the gaps inside the hardened concrete matrix.

3. Fatigue Properties
All engineering materials are subject to potential failure caused by progressive fracture under the action of repeated loadings. The stress level (the ration of applied stress to the modulus of rupture) gradually decreases.

The flexural strength of Pagan's natural pozzolan-Portland cement mixture, like the compressive strength, increases with time. Its autogenous healing mechanism also helps to mend the fractures and recover the stress level.

4. Reduced permeability and voids
The leaching of water-soluble calcium hydroxide produced by the hydration of Portland cement can be a significant contributor to the formation of voids. Also, the amount of " water of convenience " used to make the concrete workable during the placing process, creates permeable voids in the hardened mass.

Pagan's natural pozzolan can react quickly with calcium hydroxide and form additional C-S-H. Thus, it not only prevents the water soluble compound from migration out of the concrete, but also make the cement paste denser, with no voids.

In addition, natural pozzolan can increase the fluidity of concrete without " water of convenience ". Therefore, the volume of capillary pores created by water can be minimized.

5. Reduces expansion and heat of hydration
Experiments show that replacing 30% Portland cement with natural pozzolan can reduce the expansion and heat of hydration to as low as 40%. Possibly, it is because there is no heat produced when natural pozzolan reacts with calcium hydroxide and that the free calcium oxide in the cement can hydrate with natural pozzolan to form C-S-H.

Pagan's natural pozzolan decreases the heat generated by cement hydration and delays the time of peak temperature. The graphic pattern of natural pozzolan-Portland cement mixture is extended longer and lower to form a much more moderate curve than the heat of hydration curve of Portland cement itself.

6. Reduces creep and cracks
While concrete is hardening, the " water of convenience " dries away. Then, the surface of the hardening mass begins to shrink as the temperature goes down from outside. That causes the formation of creep and cracks.

Pagan's natural pozzolan moderates the expansion and shrinkage of concrete. It also helps to lower the water content of the fresh concrete. Therefore, the creep and cracks can be significantly reduced without the process of water cooling.

7. Reduces microcracking
The expansion and shrinkage mentioned above also create microcracks inside the hardened C-S-H paste and in-between the aggregate and C-S-H paste. These microcracks significantly contribute to concrete permeability as well as other concrete defects.

Pangan's natural pozzlan-Portland cement mixture expands shrinks so moderately that there is no microcracking inside the C-S-H paste. In addition, the aggregate keeps close contact with the C-S-H paste after drying.

8. Increases compressive strength
The pozzolanic reaction between natural pozzolan and calcium hydroxide happens after the C3S and C2S in the cement begin to hydrate. At the early stage of curing, 30% natural pozzolan substituting Portland cement mixture is slightly lower than reference OPC in regard to compressive strength.

As time goes by, natural pozzolan keeps on reacting with the calcium hydroxide produced by cement hydration and increasing the compressive strength by producting additional C-S-H.

After 21 curing days, 30% naturing pozzolan 70% Portland cement mixture begins to exceed reference OPC in compressive strength.

After 28 days, it exceeds reference OPC by about 15%. Pozzolanic reaction keeps on until there is no free calcium hydroxide available in the mass the compressive strength exceeds the reference OPC by 30~40%.

9. Increases resistance to chloride attack
Concrete deterioration caused by the penetration of chloride occurs quickly when chloride ions react with calcium hydroxide to form strongly expanding hydrated calcium oxychloride.

The expansion of hydrated calcium oxychloride enlarges the microcracks and increases the permeability that causes quicker chloride penetration and more damage from freezing and thawing action.

The 30% natural pozzolan added into cement can react with almost all the free calcium hydroxide and form a much denser paste. Thus, the penetration of chloride can be minimized and the few penetrated chloride ions cannot find free calcium dydroxide to react with.

In order to be durable, concrete structures that are exposed to marine conditions must use natural pozzolan as a strengthening additive.

10. Increase resistance to sulfate attack
There are three chemical reactions involved in sulfate attack on concrete :
--Combination of free calcium hydroxide and sulfate to form gypsum (CaSO4-2H2O).
--Combination of gypsum and calcium aluminate hydrate (C-A-H) to form ettringite (C3A-3CaSO4-32H2O).
--Combination of gypsum and calcium carbonate with C-S-H to form thaumasite (CaCO3-CaSiO3-CaSO4-15H2O).

All these reactions result in an expansion and disruption of concrete, and thaumasite in particular is accompanied by a very severe damaging effect which is able to transform hardened concrete into pulpy mass.

Pagan's natural pozzolan contains virtually no sulfate in itself and can quickly react with free calcium hydroxide to form additional C-S-H which makes the paste much denser. Therefore, it eliminates the formation of gypsum, ettringite and thaumasite.

Experiments demonstrate that only 20% natural pozzolan from Pagan Island substituting Portland cement can reduce sulfate expansion by 80%.

11. Reduces alkali-aggregate reaction
Expansion due to alkali-aggregate reaction can be a serious problem with OPC. This undesirable expansion causes microcracks in-between aggregate and hardened cement paste.

Experiments show that only using 25% Pagan's natural pozzolan to substitute OPC can reduce alkali-silica expansion by 70%.

(A) The alkalies in Pagan's natural pozzolan are fixed in the glass phase.
(B) During cement hydration, natural pozzolan reacts with the freed calcium hydroxide and maintains the PH level in the paste.
(C) By trapping the alkalics inside the paste in the form of alkali-silica gel, the silica in natural pozzolan renders the alkalies in the Portland cement unavailable for reaction with aggregate.

12. Impedes Carbonation
Carbonation of cement/concrete is a multi factor phenomenon, which despite being abundantly researched, still remains to be understood. Among the many factors involved, the effect of alkali on carbonation is of special importance.

The following chemical equations prove that alkali functions as a catalyst in the deterioration of cement/ concrete:

(1) CO2 + 2NaOH - > Na2CO3 + H2O
(2) 3Na2CO3 + 3CaO-2SiO2-4H2O - > 3CaCO3 + 2SiO2 + 6NaOH + H2O

Part of the sodium hydroxide reacts with silica to form water soluble alkali-silica gel and the rest can react with carbon dioxide again.

Numerous still standing ancient building clearly demonstrate that natural pozzolan can impede cement carbonation.

Adding 30% Pagan's natural pozzolan into Portland cement can enhance its resistance against carbonation:

--The concrete made from this mixture has Virtually no microcracking to allow diffusion of carton dioxide.
--Its paste has very low permeability.
--It traps all the alkali in cement to form alkali-silica gel scattering within the glassy matrix, so that it prevents the alkali to act as a catalyst in cement carbonation.

13. Reduces freeze-thaw damage
Adding Pagan's natural pozzolan into Portland cement can assist the concrete in resisting freeze/thaw damage by minimizing the permeability, voids, cracks induced by chemical expansion and attack. The paste made from Pagan's natural pozzolan-Portland cement mixture is so dense and closely cohered with aggregate that moisture can hardly penetrate into its matrix.

14. Protects steel reinforcement from corrosion
The above discussions make it very clear that concrete made from 30% Pagan's natural pozzolan 70% Portland cement mixture can protect steel reinforcement in a so densely sealed alkaline environment that no liquids and gases can penetrate through to cause corrosion to the steel.

15. Increases abrasion resistance
Pagan's natural pozzolan increases the compressive strength of concrete and makes the concrete matrix denser and stronger. It also prevents the formation of pulpy, crispy or water soluble materials created by chemical attack. Therefore, it helps the concrete to durably resist abrasion.

16. Lowers water requirement with high fluidity, self-leveling and compression.
In normal operations, the bulk volume of concrete in the constructions are placed and compacted by use of high frequency poke vibrators. The rapid vibration induces segregation phenomena of all orders of magnitude in the fresh concrete, e.g., stone segregation, internal bleeding giving bonding failures, inhomogeneous cement paste and airvoid systems.

30% Pagan's natural pozzolan 70% Portland cement mixture can achieve high concrete fluidity with low w/c ratio. Thus, concrete can be self-leveled and self-compressed without the use of vibrator.

17. Improves durability
The benefits and characteristics of natural pozzolan mentioned above clearly explain why the ancient structures built by the Greeks and the Romans can survive over 2000 years of weathering.

Pangan's natural pozzolan contains no carbon and sulfur and is free from any contamination. It is the purest, the best natural pozzolan that guarantee a long life for the structures.

18. Reduces Costs
At present, Pangan's natural pozzolan is sold at a price far lower than Portland cement. Its characteristics of workabilities also help to save a lot of construction costs and manpower, such as vibration and water cooling.

19. Increases production capacity and saves energy
Cement plants can increase 30% production capacity and save energy by mixing Pagan's natural pozzolan into their Portland cement, without adding any kiln.

20. Reduces carbon dioxide emission
The carbon dioxide emission produced by cement plants is a main environmental concern. Using Pagan's natural pozzolan to substitute 30% Portland cement can help to solve the problem.

21. Unifies quality
Uniformity of cement quality is an important requirement for building large structures. Most of the pozzolanic additives cannot meet this criterion.

Research shows that the quality of our natural pozzolan material surpasses criteria of GB/T2846 for pozzolanic materials used for cement and exceeded all requirements to a natural pozzolan in accordance with ASTM C618.

For the construction use as an additive for concrete, conforming to ASTM C-618 in the U.S. and GB/T2846 in China, or use as a major ingredient for producing Portland Pozzolan Cement, conforming to ASTM C-595-98 in the U.S. and BS6610: 1996 in the U.K.

Major Pozzolan Concrete Projects

East Bay Municipal Utility District Wastewater Treatment Plant California
Aburn Dam California
Palo Verde (Nuclear) Power Generating Plant Arizona
Sacramento Wastewater Treatment Plant California
Southern Nevada Water Project Nevada
Tehama-Colusa Canal California
George R, Moscone Convention Center California
Port of Richmond California
Pacheco Pass Tunnel California
Idaho Falls Hydro Electric Idaho
American River Falls Power Plant Idaho
Coyote Power Generating Plant N. Dakota
San Francisco Wasterwater Treatment Plant Project California
Pioneer Reservoir California
Chabot Dam California
Dumbarton Bridge California
Peace Valley Water Project California
Pyramid Lake Powerhouse California
Rock Springs Wyoming Power Plant Wyoming
Hong Kong Center California
Graduate Theological Union Building, UC Berkeley California
Pacific Gas & Electric California
Helms Creek Powerhouse Pump Station California
North Point Seawall California
Bechtel Engineering Center, UC Berkeley California
Redding Airport Runway California

Los Angeles Aqueduct (1910-1912)
Los Angeles Flood Control District during the 1920's and 1930's
Bonneville Dam (1935)
Golden Gate Bridge (1937)
Piers of the San Francisco-Oakland Bay Bridge (1935)
Friant Dam (1942)
Nearly all of the concrete in the California State Water Project
Including the California Aqueduct in the 1960's and the 1970's.