Properties and Applications of Geopolymer Masonry Blocks
Radhakrishna, Professor and Head, Department of Civil Engineering, RV College of Engineering, Affiliated to Visvesvaraya Technological University, Bengaluru.

Block masonry is one of the oldest methods of construction. It is composed of masonry units and mortar. The most popular masonry units are burnt brick concrete blocks. These conventional masonry blocks are not considered as sustainable. Burnt bricks consume considerable amount of top fertile soil and fossil fuels. Conventional cement concrete block need cement which produces carbon dioxide (CO2) during its manufacturing. Hence there is a need to develop and use alternatives masonry units. Geopolymer masonry is one of the new materials among many alternatives, in which complete elimination of cement is achieved without compromising the strength and durability. This technology makes use of marginal materials like fly ash, blast furnace slag as binders. River sand can be replaced with m-sand as fine aggregates. The reported literature is silent about the use of Geopolymer masonry blocks in the construction. The present study focuses on this sustainable technology to save the natural and scarce materials.
Industrial by-products, class F flyash and ground granulated blast furnace slag (GGBFS) were used as binders. Water was used to prepare with alkaline solution. Geopolymer bricks/blocks were cast. They were cured in ambient temperature by preserving water. The properties of masonry block/bricks were determined and used in the construction of a building. It was found that the masonry blocks exhibits comparatively better properties to the conventional masonry units. Geopolymer masonry units were satisfied the requirements of the standard Indian and other standard codes. A model building which was constructed using geopolymer masonry blocks performed better compared to traditional concrete blocks. Hence the use of Geopolymer masonry blocks can be recommended for the construction industry.
In the present developing world, construction industry is under tremendous pressure to negotiate the balance between demand and supply of materials. Extraction of natural resources must be limited to preserve them. The construction industry is facing acute shortage of constituent materials of concrete and the masonry. In this context, the challenges for the civil engineering community is to develop material for the sustainable development without compromising the mechanical properties and durability. Block masonry is one of the oldest methods of construction and was known by the Ancient Romans. After the Roman Empire passed, the use of masonry was reduced until mid-18th century. Masonry is the building of structures from individual units laid in and bound together by mortar and the term masonry can also refer to the units themselves [1-4]. Masonry is generally highly durable form construction. Block masonry is composed primarily of binder, aggregate, and water. The most popular binder is Ordinary Portland cement, which releases considerable amount of carbon dioxide during its manufacturing process [2-4]. Hence to reduce this green house gas emission, there is a need to reduce or avoid traditional cement as far as possible [3]. Geopolymer technology is emerging as a new environmental friendly construction material for sustainable development [15-20], the use waste material like flyash, GGBFS and alkaline solution in place of OPC as the binding agent. The geopolymer technology gives considerable promise for application in construction industry as an alternative binder to the Portland cement. In this technology, the source material that is rich in silicon (Si) and Aluminium (Al) is reacted with a highly alkaline solution through the process of Geopolymerisation to produce the binding material [4-10]. Geopolymer technology is one in which complete elimination of cement is achieved without compromising the strength and durability [15-20]. This technology makes use of marginal materials like fly ash, slag etc. This attempt results in two benefits. i.e. reducing CO2 releases from production of OPC and effective utilization of industrial waste by products such as flyash, slag [11-14] etc. by decreasing the use of OPC.
The use of ASTM class F flyash (low calcium) normally produced by burning of bituminous and anthracite coal. It is pozzolanic in nature; the lime percentage is less than 5% [21-30]. The class F flyash is in combination with Portland cement to produce the structural masonry units. Flyash when used as a component of cement have several benefits like fresh properties, ultimate strength and long term durability. Moreover use of flyash supports the sustainability. This can lead to a number of environmental, technical and economical benefits. Ground granulated blast furnace slag (GGBS) is a byproduct of the manufacturing of iron in a blast furnace where iron ore, limestone and coke are heated up to 1500OC. When these materials melt in the blast furnace, two products are produced- molten iron and molten slag. The molten slag is lighter and floats on the top of molten iron. The molten slag comprises mostly silicates and alumina from the original iron ore, combined with some oxides from the limestone. The demand for the natural river sand as fine aggregate is increasing day by day for increase in the construction activities. The sand mining has caused environmental imbalance. Manufactured sand can be used as the alternative to this without compromising the properties. Fly ash, slag etc. which were once considered as waste materials, can be utilised in making useful products like masonry units economically.
Literature Review
A brief literature review is made selecting the most recent publications on geopolymers.
Many researchers reported that refractory concrete can be made using quartz sand, alumina powder, zeolites and rice husk using geopolymer [1-7]. Fly ash and GGBFS – compressive and split tensile strength, bond strength - thermally cured geopolymer concrete [8-14]. Radhakrishna et al, [15-20] Possible to manufacture geopolymer masonry units using class F fly ash Phenomenological models can be developed to re-proportion. Some of other researcher have investigated that the use of Geopolymer- the Flexural strength, compressive strength in early time reached 9-15Mpa. [21-30]. They have stated that M-Sand reduces water absorption and Recycled Aggregates can be used. The use of 5-10% of Paper sludge replacement of fine aggregates in fresh concrete that increases the compressive strength and tensile strength [31-32].
The reported literature is scant about the properties and applications of geopolymer masonry units. The proposed study will address these issues.
Objectives
The objectives of the research work are as follows:
- To characterize the properties of the materials like fly ash, GGBFS and M-Sand.
- To investigate the properties of the masonry units like compressive strength, water absorption, density test, dimensionality and temperature study etc.
Materials and Methods
The following materials were used to prepare geopolymer masonry blocks/bricks:
- Fly ash (Class F) and GGBFS : 80:20
- Manufactured sand (M-sand)
- Recycled water
- Alkaline Solution : Sodium hydroxide and Sodium silicate : 1:1.5
- Molarity of sodium hydroxide: 6M, 8M, 10M & 12M
- Fluid Binders Ratio : F/B : 0.2

Class-F fly ash was procured from Raichur thermal power plant. Commercially available ground granulated blast furnace slag (GGBFS) was used as binder along with fly ash. The specific gravity of fly ash and ground granulated blast furnace slag were 2.39 and 2.90 respectively. The ratio of SiO2 and Al2O3 of the fly ash was around 2, suitable to use for making low CO2 elements. Manufactured sand (M-sand) was used as fine aggregate. The specific gravity and fineness modulus of manufactured sand was found to be 2.6 and 3.45 respectively. The M-sand and river sand used in the investigation confirms to zone-II as per IS 383-1980. The moisture content of manufactured sand was found to be 0.401%. The grain size distribution of sand and M- sand are shown in Fig. 1. The demolished concrete waste was procured from a local site and aggregates were made by breaking the blocks. The properties of the recycled water are given in Table 1.
Preparation of blocks

Results and Discussion
The Test results are as follows.
Grain size distribution for the M-sand and Natural sand are shown in fig-1

Graphical Representation showing the consolidated Compressive Strength at different ages

Dimensionality test
In geopolymer brick/block, there is no change in dimensions when compared to the regular cement block because there is no change in dimension of blocks as well any shrinkage in the blocks. Dimensionality test has been done according to IS 1077-1992.
Water absorptions test
- BIS-2185:2005 says that the water absorption shall not be more than 10% by mass.
- Increase in molarities decrease in water absorption due to the increase in density of the alkaline solution

Density test
This has been done as per IS 2185:2008 (part 4). The density of the blocks is increases in increase in molarities due to the density of the alkaline solution.

Temperature study
The temperature study has been done for the geopolymer block model house and regular cement block model houses in the month of January (10/01/2015); during this study of geopolymer block model house temperature is not as much as compare to the regular cement block model houses, due to usage of waste materials like fly ash and GGBFS.

Conclusion
The present study is expected to lead the to study and development of an appropriate use of fly ash based geopolymer block masonry. This study will be helpful to suggest the recommendation for the usage of guidelines to study the geopolymer for compressed blocks. Geopolymer masonry offers several economic benefits over conventional cement block masonry.
- The masonry block have been prepared using waste materials to satisfy the requirements of IS 2185:2008 (part 4)
- It is possible to prepare geopolymer blocks by replacing all the traditional ingredients including the water.
- Reduce carbon dioxide (CO2) emissions in the environment
- Short and long term durability would build confidence to use this masonry.
- Cement, Natural sand and water can be preserved for next generation.
Acknowledgement
The authors would like to thank the authorities of R V College of Engineering and South East Asian College of Engineering and Technology for their continuous support and encouragement.
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