POTENTIAL OF INDUSTRIAL WASTES TO POTENTIAL OF INDUSTRIAL WASTES TO PRODUCE GEO-POLYMER CONCRETE OF PRODUCE GEO-POLYMER CONCRETE OF

PRACTICAL UTILITYPRACTICAL UTILITY

VARA PRASAD. GVARA PRASAD. G

under the guidance of under the guidance of Dr. M.C. NarasimhanDr. M.C. Narasimhan

ProfessorProfessorCivil Engineering Dept.,Civil Engineering Dept.,

NITK, Surathkal. NITK, Surathkal.

INTRODUCTIONINTRODUCTION

The concern is on two environment-related The concern is on two environment-related situations :situations :

- the high amount of carbon dioxide released - the high amount of carbon dioxide released

during the production of Portland cementduring the production of Portland cement

- the abundant availability of fly ash - the abundant availability of fly ash

Ordinary Portland cement results from the Ordinary Portland cement results from the calcination of limestone (calcium carbonate) and calcination of limestone (calcium carbonate) and silica silica

5 CaCO5 CaCO33 + 2 SiO + 2 SiO22 => 3 CaO => 3 CaO..SiOSiO22 + 2 CaO + 2 CaO..SiOSiO22 +5CO +5CO22

1 tonne of cement - 0.55 tonnes of chemical CO1 tonne of cement - 0.55 tonnes of chemical CO22

combustion of carbon fuel - 0.40 tonnes of COcombustion of carbon fuel - 0.40 tonnes of CO22. .

1 T of1 T of cement = 1 T of COcement = 1 T of CO22

In 2001, the fly ash production in USA - 68 million In 2001, the fly ash production in USA - 68 million tons, but only 32 percent was used .tons, but only 32 percent was used .

In 1998, worldwide the estimated fly ash productionIn 1998, worldwide the estimated fly ash production

- 390 million tons, but only 14 percent was utilized. - 390 million tons, but only 14 percent was utilized.

By the year 2010, the amount of fly ash produced By the year 2010, the amount of fly ash produced worldwide is estimated to be about 780 million tons worldwide is estimated to be about 780 million tons

Environmental benefits – fly ash as a cement Environmental benefits – fly ash as a cement replacement material.replacement material.

Significant advancements in the usage Significant advancements in the usage of fly ash in concreteof fly ash in concrete

- Development of high volume fly ash (HVFA) - Development of high volume fly ash (HVFA) concreteconcrete

-Development of geopolymer concrete.-Development of geopolymer concrete.

Geo-polymer is an inorganic alumino-silicates Geo-polymer is an inorganic alumino-silicates polymer synthesized from minerals of geological polymer synthesized from minerals of geological origin or by-products materials, such as fly ash, origin or by-products materials, such as fly ash, blast furnace slag etc. blast furnace slag etc.

Fly ash -silicon and aluminium are main constiuents.Fly ash -silicon and aluminium are main constiuents.

To replace cement, fly ash activated – alkaline To replace cement, fly ash activated – alkaline solutionssolutions

Geo-polymer materialGeo-polymer material

The polymerization - chemical reaction under highly The polymerization - chemical reaction under highly alkaline conditions on Al-Si minerals, yielding alkaline conditions on Al-Si minerals, yielding polymeric Si-O-Al-O bonds, as described by :polymeric Si-O-Al-O bonds, as described by :

MMnn [ – ( Si – O [ – ( Si – O22 ) ) z z – Al – O - ] – Al – O - ] nn . wH . wH22O O

The amorphous to semi-crystalline three dimensional The amorphous to semi-crystalline three dimensional geo-polymeric silico-aluminate structures are of the geo-polymeric silico-aluminate structures are of the types poly(sialate), poly(sialate-siloxo) and types poly(sialate), poly(sialate-siloxo) and poly(sialate-disiloxo) .poly(sialate-disiloxo) .

single materialsingle material

Source materials Source materials

combinationcombination

Alkali activators – sodium silicate and sodium / Alkali activators – sodium silicate and sodium /

potassium hydroxide, widely used.potassium hydroxide, widely used.

Activator liquid to source materials ratio 0.25 – 0.3Activator liquid to source materials ratio 0.25 – 0.3

Geo-polymer ConcreteGeo-polymer Concrete

Geopolymer – binder.Geopolymer – binder.

usual Concrete technology methods.usual Concrete technology methods.

Fresh concrete mix - 100 Fresh concrete mix - 100 × 200 mm steel × 200 mm steel cylindrical mould in three layers.cylindrical mould in three layers.

Each layer - 60 manual strokesEach layer - 60 manual strokes

- 10 secs. Vibration.- 10 secs. Vibration.

samples - cover with a film.samples - cover with a film.

Geo-polymeric CementsGeo-polymeric Cements Alumino-silicate binders are called inorganic geopolymeric Alumino-silicate binders are called inorganic geopolymeric

compositions, since the Geo-polymeric cement obtained compositions, since the Geo-polymeric cement obtained results from an inorganic polycondensation reaction, a so-results from an inorganic polycondensation reaction, a so-called geopolymerisation called geopolymerisation

poly(sialate-siloxo) cement is obtained by blending three poly(sialate-siloxo) cement is obtained by blending three elements produced separately:elements produced separately:

- specific alumino-silicates of the kaolinitic clay species, - specific alumino-silicates of the kaolinitic clay species,

calcined at 750°C;calcined at 750°C;

- alkali-disilicates (Na- alkali-disilicates (Na22,K,K22)(H)(H22SiOSiO44))22

- granulated iron blast furnace slag - granulated iron blast furnace slag

Experimental studies on Geo-polymersExperimental studies on Geo-polymersLow calcium dry fly ash (class F)Low calcium dry fly ash (class F)

BB1 1 – 1.29 m– 1.29 m22/cc./cc.

Specific surface area Specific surface area

BB2 2 – 1.94 m– 1.94 m22/cc./cc.

Alkaline activators NaOH solution and Sodium Alkaline activators NaOH solution and Sodium silicate solutionsilicate solution

Sodium silicate solution : NaSodium silicate solution : Na22O - 14.7 %O - 14.7 %

SiOSiO2 2 - 20.4%- 20.4%

water - 55.9%water - 55.9%

Naphthalene based Super plasticizer was used.Naphthalene based Super plasticizer was used.

-Aggregates and fly ash – mixed dry in a pan for 3 -Aggregates and fly ash – mixed dry in a pan for 3 min min

-Alkaline solutions & super plasticizer are mixed and -Alkaline solutions & super plasticizer are mixed and added to solid particles – mixed for 3 min.added to solid particles – mixed for 3 min.

-Mix - 100 -Mix - 100 × 200 mm steel cylindrical moulds in 3 × 200 mm steel cylindrical moulds in 3 layers.layers.

-Each layer - 60 manual strokes-Each layer - 60 manual strokes

- 10 sec. Vibration- 10 sec. Vibration

-Samples - cover-Samples - cover

-After curing the test cylinders were removed from -After curing the test cylinders were removed from

curing chamber and left in moulds for six hours to curing chamber and left in moulds for six hours to

avoid drastic change of environmental conditionsavoid drastic change of environmental conditions

Properties of Fresh and Hardened Properties of Fresh and Hardened ConcreteConcrete

Fly ash based GPC has a stiff consistency and glossy in Fly ash based GPC has a stiff consistency and glossy in appearanceappearance

Water content influences the workability of GPCWater content influences the workability of GPC

Curing temperature ( 0c)

Elastic constants and stress relationsElastic constants and stress relations

-Youngs modulus was determined as secant modulus measured @ a level of 40% of compressive strength

Collins analytical modelCollins analytical model

ffcmcm = peak stress = peak stress

єєcmcm = strain at peak stress = strain at peak stress

n = 0.8 + (fn = 0.8 + (fcmcm/17)/17)

k = 0.67 + (fk = 0.67 + (fcmcm/62) when e/62) when ec c /e/ecmcm>1>1

= 1.0 when = 1.0 when єєcc/ / єєcmcm≤≤11

Equation applies to both normal and high strength Equation applies to both normal and high strength Portland cement concrete.Portland cement concrete.

Based on similarities on Elastic properties andBased on similarities on Elastic properties andstress – strain relations of fly ash based GPC stress – strain relations of fly ash based GPC and PCC, the current standards and codes for and PCC, the current standards and codes for concrete structures may apply to GPCconcrete structures may apply to GPC

Long term properties and DurabilityLong term properties and Durability

After 24 weeks under sustained load of 40 % of the ultimate After 24 weeks under sustained load of 40 % of the ultimate strength, the drying shrinkage strain strength, the drying shrinkage strain →→ 66 to 104 x 10 66 to 104 x 10-6-6

the creep factor the creep factor → → 0.28 and 0.390.28 and 0.39 Effect of sulphate attack : specimens of fly ash-based GPC Effect of sulphate attack : specimens of fly ash-based GPC

were soaked in 5% concentration of sodium sulphate were soaked in 5% concentration of sodium sulphate solution (Nasolution (Na22SOSO44). ).

The variations in the compressive strength, the unit mass, the The variations in the compressive strength, the unit mass, the length change, as well as the physical appearance, were length change, as well as the physical appearance, were measured. It was found that after 24 weeks exposure, GPC measured. It was found that after 24 weeks exposure, GPC did not show any sign of sulphate attack or degradation in did not show any sign of sulphate attack or degradation in properties properties

Comparision between GPC and Comparision between GPC and Portland cementitious systemsPortland cementitious systems

With similar investment, lower energy cost, and With similar investment, lower energy cost, and identical carbon dioxide emission,identical carbon dioxide emission,

GPC chemistry - 5 to 10 times more cement than GPC chemistry - 5 to 10 times more cement than Portland cement technology. Portland cement technology.

Construction and civil engineering applications Construction and civil engineering applications

--reduces COreduces CO22 emission by 80 to 90%. emission by 80 to 90%. Cost of fly ash based GPC on unit volume is more Cost of fly ash based GPC on unit volume is more

than Cement mortar, BFSP – partial replacement than Cement mortar, BFSP – partial replacement material for fly ash, cost of GPMs almost equal to material for fly ash, cost of GPMs almost equal to that of CM. that of CM.

ConclusionsConclusions GPC is answer to the need of ‘greener’ concrete for GPC is answer to the need of ‘greener’ concrete for

sustainable development. sustainable development. The elastic properties of hardened concrete and the

behaviour and strength of structural members are

similar to those of Portland cement concrete,

therefore, the design provisions contained in the

current standards and codes may be used to design

geopolymer concrete members.

The geopolymer concrete also shows excellent The geopolymer concrete also shows excellent resistance to sulphate attack, undergoes low creep, resistance to sulphate attack, undergoes low creep, and suffers very little drying shrinkage.and suffers very little drying shrinkage.

However, further research is needed to understand However, further research is needed to understand the science behind geopolymer technology, i.e.,the science behind geopolymer technology, i.e.,

· Reactivity and reaction mechanism of the · Reactivity and reaction mechanism of the geopolymer material.geopolymer material. · The rheology of the fresh geopolymer concrete or · The rheology of the fresh geopolymer concrete or

paste.paste. In addition, a large data base of various In addition, a large data base of various

characteristics of geopolymer concrete should be characteristics of geopolymer concrete should be collected in order to prepare design tools collected in order to prepare design tools and codes/standards for this new material.and codes/standards for this new material.

THANKTHANK UU