1 Madasamy Arockiasamy, 2 Perambur Neelakantaswamy, and - NRMCA Expanding the Concrete ... · 2011-03-29 · intense materials including: Class F fly ash, Class C fly ash, volcanic

Development of Sustainable and Multi-Functional Inorganic Polymer Coating Material for Restoration and Protection of Constructed Concrete

Infrastructure as well as New Structures

Felix Achille,1 Madasamy Arockiasamy, 2 Perambur Neelakantaswamy,3 and Charles E. Carraher, Jr.4

1. Green World Crete, Inc., Pompano Beach, FL 33073; PH 954-978-9399; FAX 954-978-9397; e-mail [email protected]

2. Department of Civil Engineering, Florida Atlantic University, Boca Raton, FL 33431; PH email: [email protected]

3. Department of Electrical Engineering, Florida Atlantic University, Boca Raton, FL 33431 e-mail: [email protected]

4. Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, FL 33431; PH 561-297-2107; FAX 561-297-2759; e-mail [email protected]

Abstract.

Fly ash is the major solid product from the burning of coal. The present focus of Fly ash is on its use as a cementations material. Fly ash is a fairly green material because it offers a carbon dioxide footprint 93 CO2e per ton (kg) compared to Ordinary Portland Cement (OPC) at 959 CO2e per ton (kg) and Ground Granulated Blast Furnace Slag (GGBFS) at 155 CO2e per ton (kg) and because its’ commercial use will cancel the need to place the material in a landfill. To evaluate its stability, portions of various fly ash-derived materials were exposed to extremely high concentrations of possible environmental detractors. This form of testing is one method of gaining accelerated time data. OPC was used as the control. The materials were tested against saturated solutions of sodium carbonate and sodium chloride and high concentrated solutions (10 M) of sulfuric acid, nitric acid, and sodium hydroxide. All of the tested materials were stable for over two months in the sodium carbonate, sodium chloride, and sodium hydroxide. One of the samples was stable in 10M nitric acid and one was stable in both 10M nitric acid and sulfuric acid. By comparison, OPC crumbles rapidly in both nitric acid and sulfuric acid. Thus, some of the test materials show much greater stability under quite harsh conditions in comparison to OPC. Further testing is underway. Setting

Our aging concrete-based infrastructure is continuing to decay and in desperate need of repair and rehabilitation. This includes bridges, dams, roads and commercial buildings. Most need repair and many will need to be replaced due to long-term deterioration. Our overall efforts are aimed on developing a multi-functional material for use by present and

2010 Concrete Sustainability Conference 1 © National Ready Mixed Concrete Association

future generations that meet this challenge while embracing the goal of economic development and coupled with the “green emphasis” on materials offering little or no carbon dioxide foot print for the present and future generations. In 2009 the American Society of Civil Engineers (ASCE, 2009) compiled alarming statistics concerning the condition of the nation’s core infrastructures and reported these finding in a Report Card (ASCE, 2009) which projects an estimated 5-year investment need of $2.2 trillion. Most “Infrastructure Element” categories were viewed as being in poor condition receiving grades of D and below.

Over the millennia, concrete prepared by the Romans using lime, pozzolona, and aggregates has survived giving proof of its durability. The Roman cement and the small artifacts were made using knowledge of geopolymer techniques. [Carraher, C., and Pittman, C., (2009), Nugteren, H., “Geopolymers” (2008)]

The aging infrastructure is one of the most serious problems faced by society today. For the United States, the 20th century was one of unprecedented population growth, economic development, and improved quality of life. The infrastructure systems [Pinkas, J., (2005), Duxson, P., Fernandez-Jimenez, A., Provis, J., Lukey, G., Palomo, A., van Deventer, J., (2007)] water, wastewater, power, transportation, and telecommunications – built in the 20th century have become so much a part of modern life. Large segments and components of the nation’s critical infrastructure systems including steel and reinforced concrete structures are now 50 to 100 years old and are now compromised. In the past decades, professionals focused primarily on new construction but today as much of the aging infrastructure reaches the end of its designed lifetime, the emphasis is on maintaining and extending the life of these valuable assets.

For the nation to meet the challenges of the 21st century, a new paradigm of innovative materials is needed from which practical and cost-effective solutions can be developed that will lead to resilient, cost-effective, and environmentally sustainable infrastructure systems. The U.S. Federal Highway Administration (FHWA) released a break-through 2-year study in 2002 on the direct costs associated with deterioration of infrastructure due to metallic corrosion in nearly every U.S. industry sector, from infrastructure and transportation to production and manufacturing. Initiated by National Association for Corrosion Engineers (NACE) and mandated by the U.S. Congress in 1999 as part of the Transportation Equity Act for the 21st Century (TEA-21), the study provides current cost estimates for the time and identifies national strategies to minimize the impact of corrosion on infrastructure. The study [Kosslick, H., and Fricke, R., (2007)], entitled “Corrosion Costs and Preventive Strategies in the United States,” was conducted from 1999 to 2001 by CC Technologies Laboratories, Inc., with support from FHWA and NACE. Results of the study show that the total annual estimated direct cost of corrosion in the U.S. is a staggering $276 billion-approximately 3.1% of the nation’s Gross Domestic Product (GDP). It reveals that, although corrosion management has improved over the past several decades, the US must find more and better ways to encourage, support, and implement optimal corrosion control practices. New or improved multi-functional materials need to be developed to provide for increased service life of infrastructure, security, and safety elements of the critical infrastructure.


Background

The green cementitious materials that we are focusing on are aluminosilicate-intense materials including: Class F fly ash, Class C fly ash, volcanic ash, metakaolin, kaolin clay, microsilica, other clays, steel slag, iron slag and Ground Granulated Blast Furnace Slag (GGBFS). Our initial efforts that we are reporting on here are based on fly ash. There are several aspects that prompt the current research with fly ash. First, with the increased need of cementitious material, new materials need to be developed that can expand and/or replace OPC. The cost of OPC is rapidly increasing as the availability is decreasing. Second, there is an increased need for low carbon footprint materials.

Fly ash is a low carbon footprint material in that its CO2 footprint is 93 CO2e per ton (kg) having already been established through its creation from coal burning. [Carraher, C., and Pittman, C., (2009), Nugteren, H., “Geopolymers” (2008) Pinkas, J., (2005); Duxson, P., Fernandez-Jimenez, A., Provis, J., Lukey, G., Palomo, A., van Deventer, J., (2007); Kosslick, H., and Fricke, R., (2007)] . Second, there is a need for the disposal of fly ash. About 70% of fly ash is currently stored at dump sites, while 30% is employed as a OPC extender. Thus, it is an underused resource.

Fly ash is generally divided into two groups as defined by ASTM C618: Class F fly ash and Class C fly ash. The major difference between these two classes is the amount of calcium, silica, alumina, and iron in the ash. The chemical composition is, in turn, due to the chemical content of the burned coal-anthracite, bituminous, and lignite.

Class F fly ash normally comes from older anthracite and bituminous coal. It is pozzolanic containing less than 10% lime (CaO). Because it is pozzolanic, Class F fly ash requires a cementing agent, such as OPC, quicklime, or hydrated lime, in the presence of water, to produce cementitious materials. Cementitious materials are also produced through the use of chemical activators such as sodium silicate (water glass).

Burning of younger lignite and sub bituminous coal gives Class C fly ash. It possesses pozzolanic properties but also has some self-cementing ability and does not require an activator. Typically it contains more than 20% lime and alkali and sulfate amounts are generally greater than in Class F fly ash.

Following is described our initial efforts to evaluate the ability of prepared fly ash samples to withstand aggressive conditions similar to those offered by the environment, but at much greater concentrations of the environmental agents.

Experimental

Samples were made that were approximately ¼ inches thick. The samples weighted approximately 0.6 grams. The samples were placed in glass vials and approximately 10 mL of test solution added. The samples were shaken at least once a week.


Results and Discussion

Accelerated Stability Studies Four samples were initially tested.

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Figure 1. Starting materials.

These included a control, OPC based concrete, and three specimens derived from Fly ash Class F. These samples are briefly described following.

Sample 33 (Geo-Green Crete LC-33) is a Fly Ash Class F pozzolan material having a mean diameter of 3.0 micron that has been activated in an alkaline environment with a water/cementitious ratio of 0.53 to create a liquid paste that can be sprayed, brushed and painted on a porous to semi-porous surface.

Sample 34 (Geo-Green Crete LC-34) is a Fly Ash Class F pozzolan material having a mean diameter of 3.0 micron that has been activated in an alkaline environment with a water/cementitious ratio of 0.53 to create a liquid paste that can be sprayed, brushed and painted on a porous to semi-porous surface.


Sample 35 (Geo-Green Crete LC-35) is a Fly Ash Class F pozzolan material having a mean diameter of 3.0 micron combined with a high SiO2 containing material that has been activated in an alkaline environment with a water/cementitious ratio of 0.53 to create a liquid paste that can be sprayed, brushed and painted on a porous to semi-porous surface.

While concrete is a relatively durable and robust building material, it can be severely weakened by poor manufacture or a very aggressive environment. Deterioration of reinforced concrete structures exposed to man-made or atmospheric aggressive conditions is a common problem in many countries of the world. Frequently, due to corrosion, the resistance of structures decreases much earlier than the expected service life and the need to carry out repairs of degraded structures is increasing exponentially.

The durability of reinforced concrete structures depends both on the resistance of the concrete against physical and/or chemical attack on its ability to protect reinforcing bars against corrosion. Concrete is not chemically resistant and impermeable to gases and fluids. In a number of situations, concrete and embedded reinforcing bars need some additional protection against chemical attack which can only be afforded by a barrier resistance to the action of the chemical agents encountered. Essentially all cementitious materials are affected by their natural environment.

Accelerated testing of concrete-like materials can be carried out employing increased concentrations of the potential deteriorates and increased temperature and a combination of these two factors. Thus, concrete-like specimens are exposed to various chemical agents at varying concentrations and temperatures. We will use as a base line values that are common.

Salinity: Sea water has salinity (salt concentration) of about 3.5% or 35 ppt (about 0.5 molar, M) mostly derived from the ions of sodium chloride. By comparison, fresh water has a much lower salinity of about of about 0.5 ppt. There is a great difference in the amount of bicarbonate ion in fresh and sea water. In seawater, bicarbonate ion accounts for about 0.4 % of the salt anion whereas in freshwater it accounts for about 50% of the salt anion. The amount of carbonate in the ocean is about 2 x 10-3 M and in freshwaters it is about 6 x 10-3 M.

Acid Rain-Sulfate, Carbonate, Nitrate: Another source for deterioration for cement is acid rain that is a combination of nitrogen and sulfur oxides and carbon dioxide. In worse case scenarios, the nitrogen oxide is converted to the strong and oxidizing acid nitric acid and the sulfur oxide is converted to the strong acid sulfuric acid. Carbon dioxide is converted to carbonic acid which is a weak acid and contributes to the carbonate concentration in natural waters. Strong acids act to dissolve limestone (CaCO3) and concrete. Thus, sulfuric acid reacts with limestone forming soluble calcium sulfate acting to destroy the limestone.

CaCO3 (s) + H2SO4 (aq) � CaSO4 (aq) + CO2 (g) + H2O (l)


It is difficult to quantify the amount of acid in our rain but a rough approximation is gained from looking at the average pH values of rain. The pH of pure water is 7. The pH of rain in the US ranges from 4.1 to 6.1. [National Atmospheric Deposition Program/National Trends Network (2004)] Taking the worst case scenario of a pH of 4.1 shows an acid concentration of about 10-4 molar in proton or again assuming worse case scenarios assuming that only sulfuric acid contributes to the acidity a sulfuric acid concentration of 5 x 10-5 M and assuming that only nitric acid contributed to the acidity a nitric acid concentration of 10-4 M.

Base: While fresh water is slightly acidic, ocean water is slightly basic with a pH of 7.5 to 8.4. Using as a worse case scenario a pH of 8.4 translates to a hydroxide concentration of about 4 x 10-6 M.

The following base line values will be used based on the data given above. For *sulfuric acid 5 x 10-5 M; *nitric acid 10-4 M; *sodium chloride 0.5 M; *sodium hydroxide 4 x 10-6 M and *6 x 10-3 M sodium carbonate (a water soluble source of the carbonate ion). This includes all of the major degradation modes for concrete, i.e. carbonation,

salt injury, and sulfate degradation; as well as oxidation by nitric acid and basic degradation.

For the initial temperature, room conditions of 20 °C were employed. Following are the factor increases for the materials tested in the present study. For

*sulfuric acid-2 x 105 ; *sodium hydroxide-2.5 x 105 ; *sodium chloride 12 ; *sodium carbonate 50 ; and *nitric acid 1 x 105 . In the case of sodium chloride and sodium carbonate, concentration limits the

increased factor. For the other materials a factor increase of 100,000 and greater was employed.

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Figure 2. Samples beginning (left set) and after 10 months (right set) in sulfuric acid (10 Molar) right from left to right in each set- concrete, LC-33, LC-34, LC-35.


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Figure 3. Samples beginning (left set) and after 10 months (right set) in sodium hydroxide (5 Molar) right from left to right in each set- concrete, LC-33, LC-34, LC-35.

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Figure 4. Samples beginning (left set) and after 10 months (right set) in sodium chloride (0.5 Molar) right from left to right in each set- concrete, LC-33, LC-34, LC-35.

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Figure 5. Samples beginning (left set) and after 10 months (right set) in sodium carbonate (0.3 Molar) right from left to right in each set- concrete, LC-33, LC-34, LC-35.


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Figure 6. Samples beginning (left set) and after 10 months (right set) in nitric acid (10 Molar) right from left to right in each set- concrete, LC-33, LC-34, LC-35.

All of the materials, including the OPC samples, were stable in the sodium hydroxide and sodium carbonate solutions throughout the entire 10 month study except LC-33 showed some, a minor amount, formation of feathery-like material at about 10 months time. In sulfuric acid, LC-33 and LC-34 crumbled within 30 minutes after addition to the acid. The OPC bubbled on addition of the acid and after 2 weeks finally crumbled completely. By comparison, LC-35 remained over the test period. For nitric acid, the OPC and LC-34 crumbled almost immediately after addition of the nitric acid. By comparison, LC-33 and LC-35 remained stable over the test period. Thus, in comparison to the OPC sample, LC-33 offered better stability to nitric acid and LC-35 was more stable in both nitric acid and sulfuric acid.

The major active polymeric material in fly ash is a combination of aluminosilicate rings. On a molecular basis the gel, reorganized material, and final product is a mixture of ring products containing varying amounts of the aluminum oxides and silicon oxides generally present in 8-membered rings. The IR assignments for these rings or clusters is known [Yunsheng, Z., Wei, S., and Zongjin, L., (2007) ; Mozgawa, W., Handke. M., and Jastrzebski, W., (2004) ; Lee, W., and van Deventer, J. (2003); Luan, Z., and Fournier, J. (2005); Gora-Marek, K., Derewinski, M., Sarv, P., and Datka, J. (2005); Michalski, J., Kraft, M., Sharp, T., and Christensen, P. (2006)] so that identification of the proportion of each of these rings is straightforward. These rings or clusters contain varying amounts of the aluminum and silicon oxides. Several of these ring structures are given in Figure 7.


SiO

O

Si

Si

O

O

Si

OH

O-

OH

OHO

-OH

O-

OHAl

O

O

Al

Al

O

O

Al

O-

OHO

-

OHAl

O

O

Si

Si

O

O

Al

O-

OH

O-

OH

O-

O-

AlO

O

Si

Si

O

O

Si

O-

OH

O-

OHOH

O-

O-

Si

O

O

Al

Al

O

O

Al

O-

OHO

-

OH

O-

AlO

O

Al

Si

O

O

Si

OH

O-

OH

O-

OHO-

Figure 7. Examples of aluminosilicate rings including those containing only silicone (top left) and only aluminum (top middle).

Adhesion occurs generally through one or more of the following mechanisms [Carraher, C., 2007]. Mechanical adhesion with interlocking occurs when the adhesive mixture flows about and into two rough substrate faces. This can be likened to a hook and eye, where the stiff plastic hooks get caught in the fuzz-like maze of more flexible fibers. Chemical adhesion is the bonding of primary chemical groups. Specific or secondary adhesion occurs when hydrogen bonding or polar (dipolar) bonding occurs. Viscosity adhesion occurs when movement is restricted simply due to the viscous nature of the adhesive material. The strongest and most stable of these are the formation of chemical bonds which is the mechanism found for the interaction between the aluminosilicate materials and concrete.

Each of these structures contain ionic oxygen “fingers” that can react with silicon oxide and vacant silicon sites on the sand and rocks of the concrete which can form chemical bonds between the applied aluminosilicate coating and the concrete.

Al-O- (from aluminosilicate) + +Si- (from rock) � Al-O-Si

Al-O- (from aluminosilicate) + H-O-Si (from rock) � Al-O-Si + H2O

Si-O- (from aluminosilicate) + +Si- (from rock) � Si-O-Si

Si-O- (from aluminosilicate) + H-O-Si (from rock) � Si-O-Si + H2O


These bonds can also be formed through the calcium oxide portions of the concrete.

Si-O- (from aluminosilicate) + +Ca- (from concrete) � Si-O-Ca

Si-O- (from aluminosilicate) + H-O-Ca (from concrete) � Si-O-Ca + H2O

The presence of these ionic fingers is an advantage over OPC patching materials where the extent of chemical bonding between the already in place OPC and added OPC contains little such chemical bonding. Thus, Fly ash has a distinct advantage over many other filling, patching, or coatings materials in that it chemically bonds to both itself and to OPC.

Along with the positive environmental aspects, improved physical characteristics are envisioned in comparison to no coating/filler and organic coatings. These improved characteristics are

Improved adhesion Improved workability Decreased permeability Improved sulfate protection Reduced shrinkage Improved expansion compatibility Reduced creep Decreased bleeding/segregation Increased strength (compressive and flexural) Reduced heat of hydration

Following are some reasons for using an aluminosilicate shield or coating in comparison to typical organic coatings (paints).

First, the thermal coefficient of aluminosilicate is closer to that of concrete compared to most organic coatings (coefficient of linear thermal expansion for concrete is about 12 x 10-6/K; volumetric thermal expansion is about 36 x 10-6; for polymer coatings it is about 50-90 x 10-6 K and 100 to 300 x 10-6 /K; and for aluminosilicate about 10 x 10-6 /K and 30 x 10-6 /K). Thus, there is less cause for cleavage of the adhesion between the concrete and aluminosilicate.

Second, organic coatings are derived from petrochemicals while aluminosilicates are derived from essentially waste material.

Third, aluminosilicate coatings are less expensive with a cost approaching less than ten dollars a gallon whereas specialized organic coatings cost near twenty dollars a gallon in bulk.

Fourth, organic coatings have much lower ability to resist scratching and etching in comparison to aluminosilicate coatings.

Fifth, aluminosilicate coatings adhere though formation of chemical bonds with the concrete whereas organic coatings adhere through mechanical means.


Conclusions

Initial accelerated testing on three designed fly ash samples show that they have stabilities equal to and in some cases better than OPC.

References

1. Carraher, C., and Pittman, C., (2009) “Inorganic Polymers.” in Ullman’s Encyclopedia, Wiley-VCH, Berlin. 2. Nugteren, H., “Geopolymers” (2008) 338-354, in Combustion Residues; Cox, M., Nugteren, H., and Janssen-Jurkovicova, M. Editors; Wiley, NY. 338. 3. Pinkas, J., (2005) “Chemistry of silicates and aluminosilicates.”Ceremics-Silikaty, 49, 287-298. 4. Duxson, P., Fernandez-Jimenez, A., Provis, J., Lukey, G., Palomo, A., van Deventer, J., (2007). “Geopolymer technology: the current state of the art” Advs. Geopolymer Sci., 42, 2917-2933. 5. Kosslick, H., and Fricke, R., (2007) “Chemical analysis of aluminosilicates, aluminophosphates and related molecular sieves.” Mol. Sieves, 5, 1-66. 6. National Atmospheric Deposition Program/National Trends Network (2004); NADP Program Office, Illinois State Water Survey, Champaign, Il. 7. Yunsheng, Z., Wei, S., and Zongjin, L., (2007) “Infrared spectroscopy study of structural nature of geopolymeric products.” J. Wuhan Univ. Tech.-Mater. Sci. Ed., 23, 522-527. 8. Mozgawa, W., Handke. M., and Jastrzebski, W., (2004) “Vibrational spectra of aluminosilicate structural clusters.” J. Mol. Structure, 704, 247-257. 9. Lee, W., and van Deventer, J. (2003) “Use of infrared spectroscopy to study geopolymerization of heterogeneous amorphous aluminosilicates.” Langmuir, 19, 8726-8734. 10. Luan, Z., and Fournier, J. (2005) In situ FTIR spectroscopic investigation of active sites and adsorbate interactions in mesoporous aluminosilicate ABA-15 molecular sieves.” Microporous Mesoporous Mats., 79, 235-240. 11. Gora-Marek, K., Derewinski, M., Sarv, P., and Datka, J. (2005) “IR and NMR studies of mesoporous alumina and related aluminosilicates.” Catalysis Today, 101, 131-138. 12. Michalski, J., Kraft, M., Sharp, T., and Christensen, P. (2006) “Effects of chemical weathering on infrared spectra of Columbia River Basalt and special interpretations of martian alternation.” EPSL, 248, 822-829. 13. Carraher, C., Introduction to Polymer Chemistry, Taylor & Francis, NY, 2007.


Documents

1 Madasamy Arockiasamy, 2 Perambur Neelakantaswamy, and - NRMCA Expanding the Concrete ... · 2011-03-29 · intense materials including: Class F fly ash, Class C fly ash, volcanic