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Short Paper Proc. of Int. Conf. on Advances in Civil Engineering 2012

Geopolymer Paver Blocks Aaron Darius Vaz1, Donal Nixon D’Souza2, Noothan Kaliveer2, Satish K.T2 and Amar S.M2 1

M.S.Ramaiah Institute of Technology/Student of Civil Engineering Department, Bangalore, India Email: aarondariusvaz@yahoo.com 2 M.S.Ramaiah Institute of Technology/Student of Civil Engineering Department, Bangalore, India Email: donalnixon@gmail.com Email: dabu.kaliveer@gmail.com Email: satishanaji@gmail.com Email: amarsm90@gmail.com a major greenhouse gas which is responsible for global warming. As of 2010 the world production of OPC was 3300 million tons accounting for 5% of global man-made carbon emissions [2] [3]. Today there is a great environmental responsibility, which has initiated research in sustainability and eco-friendly methods for infrastructure development. The other great problem today is disposal of solid waste. Coal fired thermal power plants generate solid waste in the form of fly ash and pond ash. Disposal of these wastes is a major engineering challenge with more stringent environmental laws. Today research has combined sustainability with waste management leading to a wonderful product called Geopolymer concrete. In 1978, a French scientist Joseph Davidovits developed a binder called Geopolymer by polymerization of source materials rich in silicon and aluminium with alkaline solutions [4]. Most commonly used source materials are fly ash and blast furnace slag. Geopolymer made of waste materials like fly ash have smaller carbon footprint compared to OPC [5]. According to Davidovits Geopolymer technology was used by Egyptians to build pyramids [6]. Modern day geopolymers are mostly made from low calcium fly ash activated by alkaline solutions (NaOH or KOH) to liberate Si and Al with an additional source of silica (usually sodium silicate or potassium silicate). These are thermally activated along with aggregates to obtain geopolymer concrete. Water is not involved in chemical reaction of geopolymer concrete and is expelled during curing where as in ordinary Portland cement concrete, water is necessary for hydration to occur.

Abstract—Green paver blocks is an ecofriendly method of making concrete paver block using geopolymer concrete. Paver blocks have been in use since thousands of years. Due to rapid infrastructure development cement concrete is the second most consumed commodity on earth today. Portland cement generates large amounts of carbon dioxide (CO 2) which is responsible for global warming since it is a greenhouse gas. Environmental responsibility has initiated research in sustainability and ecofriendly methods for infrastructure development. The other great problem today is disposal of solid waste. Coal fired thermal power plants generate solid waste in the form of fly ash and pond ash. Disposal of these wastes is a major engineering challenge today with more stringent environmental laws. Today research has combined sustainability with waste management leading to a wonderful product called geopolymer concrete. This paper reports on the use of geopolymer concrete in precast concrete paver blocks and compares the performance with the commercial available OPC paver blocks of the same mix proportions. The mix design with a target strength of 47 MPa was developed to create paver blocks suitable for highways. The tests were done and the results tabulated. Index Terms—green paver blocks, Portland cement concrete, geopolymer concrete, precast concrete paver blocks.

I. INTRODUCTION Green paver blocks have got nothing to do with color, but is an ecofriendly method of making concrete paver block. Paver blocks made of different materials have been in use since thousands of years. The Romans built roads with stone based paver blocks which are still intact today. However greater revolution in paver blocks took place in Holland in 1940’s with the making of cement concrete paver blocks. After World War II, most of Europe was in ruin and reconstruction began. Cement concrete paver blocks became an ideal choice because of its easy and faster laying, better looks and finish. Today precast concrete paver blocks are the most preferred choice for paving of footpaths, parking lots, bus stops, industries, etc. More advanced interlocking designs have increased the public appeal due to its aesthetic beauty. Due to rapid infrastructure development taking place, today Portland cement concrete is the second most consumed commodity on earth. Manufacture of ordinary Portland cement generates large amounts of carbon dioxide (CO2) which is then released into the atmosphere. About 900kg of CO2 is released for every ton of OPC manufactured [1]. CO2 is © 2012 ACEE DOI: 02.AETACE.2012.3.19

II. LITERATURE REVIEW Fly ash can be converted to a binding material by activating with alkaline solution [7]. It is observed that higher concentration of sodium hydroxide and high ratio of sodium silicate to sodium hydroxide liquid by mass results in higher compressive strength [8]. The strength of the geopolymer concrete decreases with the increase in ratio of water to geopolymer solids by mass [9]. Increase in curing temperature increases the compressive strength. It was found that 24 hours of steam curing at 60 to 80°C provided enough energy to aid geopolymerization [10]. Geopolymer concrete has excellent resistance to chemical attack and is an ideal option for use in aggressive environments [11]. Although the term ‘geopolymer’ is generically used to describe the amorphous to crystalline reaction products from 173

Short Paper Proc. of Int. Conf. on Advances in Civil Engineering 2012 synthesis of alkali aluminosilicates upon reaction with alkali hydroxide/alkali silicate solution, geopolymeric gels and composites are also commonly referred to as ‘low-temperature aluminosilicate glass’ [12], ‘alkali-activated cement’ [13], ‘geocement’ [14], ‘alkali-bonded ceramic’ [15], ‘inorganic polymer concrete’ [16], and ‘hydroceramic’ [17]. Despite this variety of nomenclature, these terms all describe materials synthesized utilizing the same chemistry, which can be described as a complex system of coupled alkali mediated dissolution and precipitation reactions in an aqueous reaction substrate. Alkali-activation of blast-furnace slag has been used as an alternative means of cement production for over 65 years [18, 19], and slags are often used as a component of geopolymeric systems. Typical image illustrating the microstructures of geopolymers synthesized from metakaolin and Class F fly ash is presented in fig 1. and the Process showing geopolymers synthesized from metakaolin and class F ash in fig 2.

(1) Gourley and Johnson have developed geopolymer precast concrete products for commercial scale. These include sewer pipes, railway sleepers and wall panels [20]. Precast reinforced geopolymer concrete culverts developed showed promising results on a commercial scale [21]. Geopolymer concrete can be effectively used as a substitute for OPC in precast concrete products. Geopolymer concrete is a feasible option for waste stabilization [22]. Several studies have been conducted across the world for effective use of geopolymer in various construction and infrastructure elements; this paper reports on the use of geopolymer concrete in precast concrete paver blocks and compares the performance with the commercial available OPC paver blocks of the same mix proportions. The superior properties of geopolymer concrete, based on Prof. B.V. Rangan and Hardijito, are a. Sets at room temperature b. Nontoxic, bleed free c. Long working life before stiffening d. Impermeable e. Higher resistance to heat and resist all inorganic solvents f. Higher compressive strength Compressive strength of geopolymer is very high compared to the ordinary Portland cement concrete. Geopolymer has also showed very high early strength hence it is used in the precast industries. Geopolymer Concrete showed good workability as of the Portland cement concrete. Despite the many advantages the limitations are as follows: a. Bringing the base material fly ash to the required location b. High cost for the alkaline solution c. Safety risk associated with the high alkalinity of the activating solution d. Practical difficulties in applying steam curing/ high temperature curing process. [23] Considerable research is ongoing to develop geopolymer systems that address these technical hurdles.

Fig 1. Microstructures of geopolymers synthesized from metakaolin and class F ash

III. EXPERIMENTAL PROGRAM The experimental program consisted of the following steps:  Preliminary investigation of materials used.  Development of mixed design for OPC paver blocks based on IS 10262:2009 [25] confirming to the standards of IS 15658:2006 [24] and hence to arrive at the base proportion.  Development of GPC paver blocks of the above base proportions with different strengths of activators and steam curing at 60°C for 24 hours  Studies on mechanical and physical properties on paver blocks on 28th day as per IS 15658:2006 [24]

Fig 2. Process showing geopolymers synthesized from metakaolin and class F ash

This geosynthesis involves the chemical reaction of geopolymeric precursors such as aluminosilicate oxides with alkali polysilicates yielding polymeric Si-O-Al bonds as shown in (1). © 2012 ACEE DOI: 02.AETACE.2012.3.19

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m3. They were free from deleterious matter confirming to IS 383-1970 [28].

and ASTM C936 [26] (for durable studies) The base proportion was 1:1.2:2 with a water to cement ratio of 0.35 using codal provisions. In geopolymer paver blocks, cement was replaced by fly ash and water is replaced by activator alkaline solutions.

D. Water Tap water was used for mixing and curing. It was free from deleterious materials confirming to IS 456-2006 [29] and IS 3025-1964 [30] specifications.

IV. DEVELOPMENT OF GEOPOLYMER CONCRETE MIXES

E. Fly ash Fly ash for the experiment was obtained from Raichur Thermal power station, Raichur, Karnataka. The lime reactivity as per IS 1727-1967 [32] is 7.1 MPa. The physical properties are as below:

Based on base proportion of OPC mix as show in table I, the geopolymer mix of fly ash, fine aggregate and course aggregate was taken. Ratio of alkaline liquid to fly ash was taken as 0.35. Ratio of sodium silicate to sodium hydroxide was taken as 2.5. The concentration of sodium hydroxide was varied from 8M to 12M. For good casting slump values need to be between 0 to 10cm or 100mm. Super plasticizer may be added to get the required workability.

Specific gravity Fineness modulus (Passing 45µ)

2.35 9.8%

Chemical composition of fly ash SiO2 54.6% Al2O3 28.8% Fe2O3 7.9% CaO 1.9% L.O.I 2%

TABLE I. BASE PROPORTIONS FOR GEOPOLYMERMIX

As per IS 3812-1981 [31], fly ash is grade 1 with low calcium F. Sodium Hydroxide Commercially available sodium hydroxide flakes with a purity of 98% were used.

GPC 3 had 2.65 kg/m of super plasticizer. V. MATERIAL PROPERTIES

G. Sodium Silicate Commercially available sodium silicate solution supplied to the industries was used.

A. Cement Birla 53 grade Portland cement, conforming to IS 12269:1987 [27]. The properties are as shown in table II. TABLE II. PROPERTIES

Chemical properties are as below: SiO2 to Na2O ratio by mass Na2O SiO2 Water Assay

53GRADE PORTLAND C EMENT

2 (approx.) 15.3% 30% 53.2% min 97%

Super plasticizer – Glenium B233 was used VI. OPC PAVER BLOCKS MIX DESIGN The mix design with a target strength of 47 MPa was developed to create paver blocks suitable for highways. The proportioning was done based on IS 10262:2009 [25]. The mix proportions of OPC paver blocks was taken as base proportion. 530 kg cement, 636 kg fine aggregate and 1060 kg of coarse aggregate for 1m3 of concrete were mixed with 0.35 water to cement ratio.

B.Fine aggregates (sand) Naturally locally available river sand was used as fine aggregate. Material passing 4.75mm sieve and retained on 75 µm sieve was used. The fineness modulus was 3.40 and specific gravity was 2.67. Water absorption was 1.68 %

VII. CASTING OF PAVER BLOCKS Both OPC and GPC paver blocks were mixed in a concrete mixer. In GPC the mixing is done as specified by B.V. Rangan [9]. The fly ash and aggregates were dry mixed for two minutes followed by addition of activator solutions i.e. sodium hydroxide and sodium silicate mixed 24 hours prior. It was

C. Coarse aggregate (stone chips) Crushed stone from granite was used as course aggregate. Material passing 10mm sieve and retained on 4.75mm were used. Specific gravity was 2.7 with bulk density of 1980 kg/ © 2012 ACEE DOI: 02.AETACE.2012.3.19

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Short Paper Proc. of Int. Conf. on Advances in Civil Engineering 2012 wet mixed for another 4 minutes, if plasticizer was required it should be added along with the alkaline solution. The paver blocks were casted using a hydraulic automated paving block machine with pressing force of 70tonnes. I section specimen mould of 80mm thickness was used as shown in fig 3. The OPC paver blocks were cured in water for 28 days and GPC paver blocks were steam cured at 60°C for 24 hours.

Fig 4. Compressive strength of paver blocks versus age

IS 15658:2006 [24] specifies minimum compressive strength of 47.2 N/mm2 of 80 mm thick heavy traffic paving blocks. GPC paver blocks have high compressive strength compared to OPC. They also have high early strength gain. All paver blocks satisfied the compressive strength requirement for heavy traffic paving. Increasing the strength of NaOH increased the compressive strength of paver blocks.

Fig 3. I section GPC paver block

VIII. TESTING AND RESULTS A.Mechanical and physical properties The Mechanical and Physical properties of paving blocks casted are as given in the table III. TABLE III. MECHANICAL AND PHYSICAL PROPERTIES

C. Flexural Strength Flexural strength is express in term of flexural stress or in form of breaking load. GPC was found to have better flexural strength compared to OPC. IS 15658:2006 [24] specifies a breaking load of 7 kN. All blocks satisfied the specification for heavy traffic paving.

CASTED PAVER B LOCKS

D. Split Tensile Strength Split tensile strength was found in accordance to IS 15658:2006 [24]. GPC paver blocks were found to have high split tensile strength compared to OPC. As per IS 15658:2006 [24] there are no acceptance limits. As per Turkish standards TS- 2824 [33], individual splitting tensile strength should be greater than 2.8 MPa. All blocks satisfied the specifications. E. Abrasion Abrasion test for paving was done in accordance to IS 15658:2006 [24]. GPC paver blocks were found to have superior abrasion resistance. As per IS 15658:2006 [24] Annex E – abrasion value should be less than 2 mm for 80 mm block and 3 mm for 60 mm blocks. OPC paver blocks have lower abrasion resistance than specified by the standards.

B. Compressive Strength Compressive strength of paver blocks were determined at 1 day, 3 days, 7 days, and 28 days in accordance to IS 15658:2006 [24] are as shown in table IV and the compressive strength versus age as shown in fig 4.

F. Water absorption As per IS 15658:2006 [24], 24 hour water absorption should be less than 7% for individual blocks. GPC paver blocks had very less water absorption. All blocks met the specifications.

TABLE IV. C OMPRESSIVE STRENGTH O F PAVER B LOCKS

G. Weight Loss in Acid Solution The samples were immersed in 10% H2SO4 solution for 30 days. The weight loss in OPC was found higher than GPC paver blocks. Weight loss increased with increase in concentration of NaOH in GPC. GPC was found to possess excellent sulphate resistance properties making it ideal for aggressive marine environment. © 2012 ACEE DOI: 02.AETACE.2012.3.19

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Short Paper Proc. of Int. Conf. on Advances in Civil Engineering 2012 REFERENCES

H. Density The key for strong paver blocks is the density, high dense paver blocks can resist abrasion better and have better resistance to freezing and thawing. GPC paver blocks were found to have higher density than OPC paver blocks. Increase of NaOH concentration increased the density of paver block.

[1] Paul Miles, “Eco cement: The world’s favourite building material gets a green over”, 2012. [2] Edwards P, McCaffrey R, “Global Cement Directory 2010”, PRO Publications, Epsom, UK, 2010. [3] “The Cement Sustainability Initiative: Progress report”, World business Council for sustainable development, 2002-2006 [4] Davidovits J, “Soft Mineralogy and Geopolymers”, Proceedings of the Geopolymer International conference, the Universite’ de Technologie, Compiegne, France, 1988. [5] Lloyd N, V. Rangan, “Geopolymer Concrete – Sustainable Cementless Concrete” ACI Special publication SP – 261, 10th ACI International conference on recent advance in concrete Technology and Sustainability issues, American concrete Institute, Farmington, MI, 2009. [6] Davidovits J, “Pyramids of Egypt Made of Manmade stone, Myth or Fact?”, Symposium on Archaemetry 1984. Smithsonian Institution, Washington DC, 1984 [7] Davidovits J., “Geopolymer Chemistry and applications”. Institute Geopolymere, Saint Quentin, France, 2008 [8] Hardjito D, S Wallah, D.M.J. Sumajouw, B.V. Rangan, “ On the development of Fly ash based Geopolymer Concrete”, ACI Materials Journal, vol 101, no 6, 2004 [9] Rangan B.V, “ Mix design and production of fly ash based geopolymers concrete”, Indian concrete journal, V.82 (5), pp 7-15, 2008 [10] Hardjito D and Rangan B.V, “Development and properties of Low Calcium fly ash based geopolymers concrete”, Research Report , GCI, Faculty of Engineering, Curtain University of Technology, 2005 [11] Siddiqui K.S, “ Strength and durability of low Calcium Fly ash based geopolymers concrete,” Final year Honours dissertation, The University of western Australia, Perth, 2007 [12] Rahier H, Van Mele B, Biesemans M, Wastiels J, Wu X, J Mater Sci 31:71, 1996 [13] Palomo A, De La Fuente JIL Cem Conc Res 33:281, 2003 [14] Krivenko PV In: Krivenko PV (ed) Proceedings of the first international conference on alkaline cements, concretes. VIPOL Stock Company, Kiev, Ukraine, pp 11–129, 1994 [15] Mallicoat S, Sarin P, Kriven WM Ceram Eng Sci Proc 26:37, 2005 [16] Sofi M, Van Deventer JSJ, Mendis PA, Lukey GC, J Mater Sci (this issue), 2006 [17] Bao Y, Grutzeck MW, Jantzen CM, J Am Ceram Soc 88:3287, 2005 [18] Purdon AO, J Soc Chem Ind Trans Commun 59:191, 1940 [19] Roy D, Cem Conc Res 29:249, 1999 [20] Gourly J.T and Johnson G.B, “Developments in Geopolymer Precast Concrete”, Proceedings of the International workshop on geopolymers and geopolymers concrete, Perth, Australia, 2005 [21] Cheema D.S, N.A. Lloyd, Rangan B.V, “Durability of geopolymers concrete box culverts – A greem alternative Proceedings of the 34th Conference on our World in Concrete and structures, Singapore, 2009 [22] Duglas C Comrie, John H Paterson and Doughlas J. Ritcey, “Applications of Geopolymer technology to waste stabilization”, D. Code consulting LTD, Boulevard East, Mississaug, Ontario, [23] http://infohouse.p2ric.org/ref/14/13863.pdf [24] Lloyd, N. and Rangan, B, “Geopolymer Concrete with Fly Ash”, in Zachar, J. and Claisse, P. and Naik, T. and Ganjian, G. (ed), Second International Conference on Sustainable

I. Slump As per IS 15658:2006 [24] concrete paving blocks should be a stiff mix with zero slump. However for practical applications concrete with slump between 10 to 50 mm is required. Increasing the concentration of NaOH solution reduces the slump. If the slump reduces too much super plasticizers may be added to reduce water demand and increase workability of concrete. GPC 3 mix was found to have zero slump and was too stiff. 0.5% of super plasticizers was added to increase the workability. J. Weight Loss in Alkali Solution The samples were immersed in 4% NaOH solution for 30 days. Weight loss was found to be very less in GPC paver blocks compared to OPC paver blocks. This makes GPC paver blocks more suitable for aggressive soil environments with high alkali. K. Freezing and Thawing This test was done as per ASTM C 67 method. Paver’s were placed in a tray with 13 mm deep water. The unit was subjected to 50 freezing and thawing cycles with one cycle consisting of 20 hours of freezing at -9°C and 4 hours of thawing at 24°+5.5°C. Weight loss after 50 cycle was determined. As per ASTM C 67 the loss in weight should not be greater than 1%. OPC paver blocks have poor resistance to thawing and freezing and do not meet ASTM C standards. GPC paver blocks were found to have superior resistance to freezing and thawing and thus an ideal option for paving of roads in the cold climate regions. CONCLUSIONS Based on the experimental study conducted geopolymer concrete can be effectively used for manufacture of precast concrete paver blocks. GPC paver block have high compressive strength for the same mix proportion and high strength to gain. This can save lot of curing time and space at manufacturing units. GPC paver blocks have superior resistance to chemical attack making them suitable for aggressive soils. GPC paver blocks outperform OPC paver blocks under freezing and thawing conditions. This makes them suitable for arctic environments where OPC based products deteriorate rapidly. Geopolymers made out of waste materials like fly ash not only have smaller footprints but help reduce the footprint of other industries namely, coal fired power plants.

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Short Paper Proc. of Int. Conf. on Advances in Civil Engineering 2012 Construction Materials and Technologies volume 3, pp. 14931504. Ancona, Italy: UWM Center for By-Products Utilization, 2010. [25] IS 15658:2006, “ Precast concrete blocks for paving”, Bureau of Indian Standard, New Delhi, 2006 [26] IS 10262:2009, “Concrete Mix Proportions – Guidelines”, Bureau of Indian Standard, New Delhi, 2009 [27] ASTM C936 – Standard Specification for solid concrete Interlocking Paving units, American Society for testing and materials, Pennsylvania, 2002 [28] IS 12269-1987 – Standard Specification for 53 grade ordinary Portland cement – Bureau of Indian Standard, New Delhi, 1987

[29] IS 383-1970, Standard Specification for coarse and fine aggregate from Natural source for concrete, 1970 [30] IS 456-2006 – “Plain And Reinforced Concrete – Code of Practice”, Bureau of Indian Standard, New Delhi, 2006 [31] IS 3025-1964 – “ Methods of Sampling and Test (Physical And Chemical) For Water Used in Industry”, Bureau of Indian Standard, New Delhi, 1964 [32] IS 3812-1981 – “Specification For Fly Ash For Use As Pozzolana And Admixture”, Bureau of Indian Standard, New Delhi, 1981 [33] IS 1727-1967 – “Indian Standard Methods of Test for Pozzolanic Materials”, first revision, “, Bureau of Indian Standard, New Delhi, 1967 [34] TS – 2824 – “Concrete paving blocks – requirements and test methods”, Turkish standard institute Ankara, 2005.

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