Behaviour of Geopolymer Mortar

Vishwanath K Dalawai and Prashanth V P
Geo-polymer mortar (GPM) is proven for its strength, durability and sustainability [2 &3]; strength of GPM is a function of alkaline to binder ratio, and has an adverse effect on consistence properties of mortar. Early research proven the art of sundry curing GPM, with a combined binder fly-ash and GGBFS [11]. The fresh properties of GPM can be improved with the dilution of alkaline to binder ratio (Free Moisture) up to limit with refer to flow table test, Consistency of GM increases with increase in the water-to-alkaline binder ratio, but in the mean way which affect inversely with compressive strength. The present investigation of pH in alkaline solution evident the degree of dilution of solution may not alter the mechanism of Geo-polymerization with addition of water. Commercial available Sodium silicate solution as alkali and 4 molar sodium hydroxide solutions were used as alkaline activators. Activated alkaline solution to binder ratio of 0.5 - 0.8 for Rich mortar (1:3) and lean mortar (1:6) by mass was maintained constant for the study of dilution and bond strength properties of GPM.FA and GGBFS based 1:3 and 1:6 GPM offers early strength of order 5-12 MPa for three days Sundry curing regime. GPM with alkaline to binder ratio 0.23 to the dilution up to 0.8 may offers good shear bond strength of 0.52N/mm2&0.31N/mm2 for 10mm -5mm masonry joint.

The geopolymer concrete solutions has gained momentum in the recent times, due to environmental concern related to the production of cement in terms of energy consumption and carbon foot print. One such alternative material for the cement is the use of alkali-activated binder using industrial by-products containing silicate materials. The most common industrial by-products used as binder materials are fly ash and blast furnace slag. Slag has been used as cement replacement material due to the latent hydraulic properties, while fly ash has been used as pozzolanic material to enhance physical, chemical and mechanical properties of mortars. The utilization of large proportion of by-products would contribute to the elimination of an environmental problem and to the development of potentially new high-performance material. Recent research has shown that it is possible to use fly ash or slag as a sole binder in mortar by activating them with an alkali component. The activation of material containing mostly silicate and aluminates by a highly alkaline solution will form an inorganic binder through a polymerization process in 1979 [1&3].

The current research is evident that GPM can be cured in sun-dry condition with proportionate combine binder FA&GGBFS [11]. Alkaline to binder ration place significant role in predicting the properties of GPM. To achieve a good consistence in GPM, increasing the alkaline binder ratio, there is significant effect setting of mortar. In this study attempt is made to enhance the consistency of GPM, with dilution of alkaline solution and its impact on Geopolymerization and some basic harden properties are studied.

Material And Methods
Fly ash and GGBS

In the present investigation Class F fly ash and GGBS are considered as binders. The physical characteristics are reported in Table-1.

Table 1: Physical Properties of Binders
Particulars Fly ash GGBS
Residue on 45µ sieve 24.4% 2.9%
Specific gravity 2.2 2.8
Fineness (Blaine’s air permeability) 252.30m2/kg 521.7m2/kg

Locally available river sand is chosen as filler, which confirm the requirements Indian standards.

Alkaline solution
The locally available sodium silicate and sodium hydroxide solution are used in the present investigation as alkaline solution. The sodium hydroxide is in flakes and pellet with about 98% purity. These pellets were mixed with distilled water to obtain the sodium hydroxide solution of required molarity. In the present study, 4M (4*40g=160g) NaOH solution is considered for investigations. The commercial grade of sodium silicate which has purity of 78% and contains 27% of water is used in the present investigation [7].

Curing of the specimens
The GPM specimens are cured in sun-dry for atmospheric humid factor and varying temperature. The sun-dry curing specimens were covered with a thick polythene sheet in order to reduce the moisture cracks and conventional impression curing is adopted for conventional cement mortar.

Results & Discussion
Influence of addition of water on pH value of combined alkaline solution.

The defining properties for GPM are the alkaline to binder ratio. In the view of enhancing the workability for required strength, an attempt has been made to replace alkaline to binder ratio with water to binder ratio in the mix. The effect of addition of water on the alkalinity of solution is evident thorough pH observation of combined solution of NaOH and Na2Sio3.

Compressive strength v/s Mix proportions

Table-2: Ph Value of Alkaline Solution with Respective Addition of Water
Alkaline solution (ml) Water (ml) pH values
1St Day
pH values
2nd Day
pH values
3rd Day
100 00 13.7 13.7 13.7
90 10 13.62 13.62 13.62
80 20 13.58 13.58 13.58
70 30 13.52 13.52 13.52
60 40 13.48 13.50 13.50
50 50 13.42 13.42 13.44
40 60 13.34 13.32 13.36
30 70 13.24 13.24 13.24
20 80 13.12 13.14 13.14
10 90 12.88 12.88 12.90
00 100 7.82 7.94 7.98

The results clearly show that the alkalinity of combined solution does not vary much with the addition of water and there is no significant change in the pH of alkaline solution for the observation of 1, 2 and 3 days in laboratory condition. Hence it can be said that there is no change in the alkalinity of geopolymer solution for continues incremental addition of water.

Table-3: flow and compressive strength for different mix proportions
Cement mortar Geopolymer mortar
Mix No Mix Proportions Alkali/Binder Ratio Flow Values (mm) Compressive Strength MPa Mix No Mix Proportions W/C Ratio Flow Values (mm) Compressive Strength MPa
3days 7days 3days 7days
S1 1:3 0.64 195 10.20 12.44 N1 1:3 0.72 195 13.2 19.59
S2 1:3 0.68 200 9.38 11.15 N2 1:3 0.8 200 11.28 17.95
S3 1:3 0.72 210 6.44 8.57 N3 1:3 0.88 210 9.24 16.32
M4 1:6 1.13 195 3.67 6.32 P4 1:6 1. 3 175 7.89 12.24
M5 1:6 1.23 200 2.86 5.71 P5 1:6 1.39 200 7.02 11.28
M6 1:6 1.3 210 2.04 4.49 P6 1:6 1.5 210 6.59 10.2

Influence of dilution of Alkaline to binder ratio on the properties of GPM.
As the geopolymer consists of binders and alkali solution, it is necessary to optimize the solution content required for the matrix. Therefore, the solution content required for the different alkali solution to binder ratios were done for the mixes considered for the study i.e., 1:3 and 1:6. Different ratios have been considered starting from 0.36 to 0.72. The optimum values from the ratios will result in required flow. Primarily few trial mixes were made to fix up the alkali solution to binder ratio using flow table test. Three trials for each mix have been made and tested. The average of all the three trials per each mix has been tabulated in table-4.

Table-4:Alkaline binder Ratio for Mortar
Sl No Mix Proportions Alkaline/Binder Ratio Flow Values (mm)
1 1:3 0.4 Nil
2 1:3 0.5 157.5
4 1:6 0.8 Nil
5 1:6 1 Nil

GPM offers good early strength and it is evident that strength of GPM is based on the percentage of alkaline solution, hence, for further work, min alkaline to binder for good flow values are chosen as from TABLE VII and have been kept constant and increasing the amount of water on basis of the flow value or workability in the study. According to IS 2250-1981, the mortar flow should be around 100% to 110% i.e., 200 to 210mm flow depending upon the purpose of mortar.

The trend (fig.3) between the flow values in % and the Alkaline/Binder (A/B) ratio fallows an approximately linear relationship; this relationship is more convenient to use the Alkaline/Binder ratio curve for interpolation.

Table- 5. Effect of variation of water to alkaline ratio (w/a) for a/b ratio 0.4 of 1:3 mortar/cu-m.
Mix No Added W/A ratio Binder  (kg) Alkaline solution (kg) Sand (kg) Added water (kg) Flow table value (%) Dry Density (kg/m3) Av. Compressive strength (MPa), for day
Fly ash GGBS Na2Sio3 NaoH Sun-dry curing Water curing
3 7 3 7
M1 0.375 472.5 52.5 105 105 1575 78.75 75 2111.9 12.24 13.59 8.97 10.74
M2 0.437 472.5 52.5 105 105 1575 91.77 85 2088.8 10.33 11.97 7.75 9.39
M3 0.52 472.5 52.5 105 105 1575 109.2 110 2110.0 8.84 9.24 5.3 5.57

The strength of mortar primarily depends upon the strength of the binder paste. The strength of paste increases with binder content and reverse with voids and alkaline content. The strength of mortar is only depending upon water/alkaline ratio, provided the mix is workable in GPM. The relation between the water/alkaline ratio and the strength is shown in fig 4 and 5. It is observed that lower water/alkaline ratio achieves higher strength, whereas comparatively higher water/alkaline ratio give lower strength.

Compressive strength v/s Water/Alkaline (W/A) ratio

Relationship between compressive Strength v/s Flow values
The relation between the strength and the flow values in % is shown in fig 9 and 10. It is evident that increase in the flow value decreases the strength. When the flow value is low, the workability is low, and it gives the higher strength.

Table-6. Effect of variation of water to alkaline ratio (w/a) for a/b ratio 0.5 of 1:3 mortar. per cu-m
Mix No- S1 Added W/A ratio Binder (kg) Alkaline solution (kg) Sand (kg) Added water(kg) Flow table value (%) Dry Density (kg/m3) Avg Compressive strength (MPa)
FA GGBS Na2Sio3 NaOH Sun-dry curing Water curing
3 Days 7 Days 3 Days 7 Days
,M1 0.18 472.5 52.5 131.25 131.25 1575 47.25 75 2120 10.61 13.05 7.35 10.34
M2 0.2 472.5 52.5 131.25 131.25 1575 52.5 85 2080 15.71 12.91 8.16 7.61
M3 0.22 472.5 52.5 131.25 131.25 1575 57.75 110 2100 12.10 10.06 8.56 9.25

Compressive strength v/s Water/Alkaline (W/A) ratio

Table-7. Effect of variation of water to alkaline ratio (w/a) for a/b ratio 0.8 of 1:6 mortar.
Mix No Added W/A ratio Binder  (kg) Alkaline solution (kg) Sand (kg) Added water (kg) Flow table value (%) Dry Density (kg/m3) Avg Compressive strength (MPa)
FA GGBS Na2Sio3 NaOH Sun-dry curing Water curing
3 Days 7 Days 3 Days 7 Days
S2,N1 0.473 270 30 120 120 1800 113.52 180 2008.5 2.85 4.11 4.76 1.27
S2,N2 0.509 270 30 120 120 1800 122.16 195 2048.5 2.31 3.80 4.48 1.15
S2,N3 0.545 270 30 120 120 1800 130.8 210 2010.9 2.04 3.39 4.21 1.06

Compressive strength

Shear Bond Strength of Geopolymer Mortar
The geopolymer mortar bond strength of masonry specimen is determined by testing masonry triplet under shear. The main objective is to evaluate the strength of mortar mixes with varying proportions by determining the shear strength of triplets and comparing it with the conventional mortar mixes.

Table-8. Shear strength of solid concrete blocks
Sl No Direction of the  plane Thickness of the mortar joint(mm) Failure load (N) Shear strength
1 Vertical 10 28000 0.52
2 Horizontal 5 35000 0.31

The experimental work on the consistent factors of GPM is evident for the following observations:
  • Alkalinity of the solution doesn’t change with dilution with free moisture and may not alter the chemistry of polymerization solution and may not alter the Geo polymer mechanism in GPM.
  • Utilization of GGBS as binder to a certain extent (i.e.5-10%) improves the setting time and compressive strength of the geopolymer mortar as compared to conventional mortar. And also added the word self-curing for sundry curing application.
  • The results are evident that using fly ash along with GGBS as base material and alkaline solution dilution of free moisture, it is possible to produce mortar of compressive strengths of the order of 5-15MPa. And offers an early strength (about 5-7 MPa in 3 days of sun dry curing) as compared with conventional mortars.
  • Bond strength of the GPM (of thickness 5mm and 10mm) is found to be 0.31N/mm2 for horizontal plane and 0.52N/mm2 for vertical plane than the conventional cement mortar.
  • Cheng, T. W. and J. P. Chiu. “Fire-resistant Geopolymer Produced by Granulated Blast Furnace Slag.” Minerals Engineering 16(3): 205-210, 2003.
  • F.Rendelland R. Jauberthie, “The deterioration of mortar in sulphate environment”. Cement and concrete Research pp. 321-327, 1999.
  • J. Davidovits, “Properties of Geopolymer Cements”. Procedings of the first international conference on alkaline cements and concretes. Vol. 1 SRIBM, Kiev, Ukraine, pp. 131-149. 1994.
  • Jae Eun Oh, Paulo J.M. Monteiro , Ssang Sun Jun, Sejin Choi , Simon M. Clark, “The evolution of strength and crystalline phases for alkali-activated ground blast furnace slag and fly ash-based geopolymers” Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720, USA, 2009.
  • Jumrat, S. Chatveera, B. and Rattanadecho,P. “Dielectric properties and temperature profile of fly ash-based geopolymer mortar”, International Communications in Heat and Mass Transfer ,2010 Elsevier.
  • K.K.Deevasan, (2008) A Study on -“Geopolymer concrete using Industrial effluent”, M.Tech Thesis (Department of Civil Engineering; BMS College of Engineering), Submitted to Visvesvaraya Technological University –Karnataka
  • M. D. Cohen and B. Mather, “Sulfate attack on concrete”. Research needs ACI materials Journal, pp. 62-69, 1991.
  • Mohammed Saleh. (2007). “A Study on Geopolymer Concrete incorporating Flyash”, M.Tech Thesis (Department Of Civil Engineering; BMS College of Engineering), Submitted to Visvesvaraya Technological University –Karnataka.
  • Mohammed,M. Kamarudin,H.I, Niza,K. and Zarina,Y. “Review on fly ash-based geopolymer concrete without Portland Cement”, Journal of Engineering and Technology Research Vol. 3(1), pp. 1-4, January 2011.
  • Palomo, M.W. Grutzeck, M.T. Blanco,“Alkaline activated fly ashes cement for the future”. Cement and concrete research, pp. 1323-1329, 29. 1991
  • Prashanth V P, R.V. Ranganath and M.S. Sudarshan “Sun cured alkali activated concrete- Some basic properties”, International Conference on “world of concrete India”, October 24-26, Hyderabad – 2013.
  • Wallah, S. E., & Rangan, B. V. Low-Calcium Fly Ash-Based Geopolymer Concrete: Long-Term Properties, Research Report GC 2. Perth: Faculty of Engineering Curtin University of Technology. 2006.
Click Here
To Know More / Contact The Manufacturer
Please fill in your details, we will contact you as soon as possible
Choose Title from the listPlease let us know your name.
Please let us know your Designation.
Invalid Input
Please let us know your email address.
Please let us know your City.
Please let us know your Contact Number.
Please brief your query.
Our other value-added services:

To receive updates through e-mail on Products, New Technologies & Equipment, please select the Product Category(s) you are interested in and click 'Submit'. This will help you save time plus you will get the best price quotations from many manufacturers, which you can then evaluate and negotiate.

Equipment & Machinery
Invalid Input
Building Products
Invalid Input
Invalid Input

Sustainability in Indian Cement Industry - Challenges and Avenues

Cement is the most used industrial commodity required for development, but it is also responsible for high GHG emissions; so there is a need to create a balance between the nation’s growth and environment sustainability Read More ...

Characteristics of Alternative building materials

Cement concrete is the most consumed materials on the earth next only to water. The ingredients used in preparing concrete are not sustainable. The ingredients are responsible for causing global warming. The most Read More ...

Ready Mix Concrete - Helping the Construction Industry Achieve Sustainable Development

India’s ready-mix concrete (RMC) market is projected to witness a 7-9% CAGR in the next five years. This growth is predominantly driven by the increased investments in the development of infrastructure throughout Read More ...

Impact of Ground Granulated Blast Furnace Slag on High-Performance Concrete

Concrete, being a physical mixture of cement, aggregate (sand and crushed rocks), and water, is the key construction material across the world. There is now a huge demand for infrastructure which has increased concrete Read More ...

Urban Concrete: Requisites & Remedies

There is a need for technologically advanced concrete admixtures for the ready-mix industry that meet industry codes and meet or exceed the demands of challenging construction applications and adverse placement conditions Read More ...

High Performance Concrete: Composition & Benefits

High Performance Concrete (HPC) is seeing major applications in the field of civil engineering constructions such as long-span bridges, tunnels, high-rise buildings, huge complexes, highway pavements, and more, since Read More ...

Robust Mix Proportioning of Self-Compacting Concrete Mixes - A Comparative Study

Concrete being the second largest consumed material after water needs attention towards sustainable construction with an increase in infrastructure. The world is moving towards innovative techniques and methodologies Read More ...

Structural behaviour of Geopolymer Masonry

Traditional masonry units are not sustainable and eco friendly due to consumption of fuel or cement. It is essential to find sustainable alternatives. This paper reports about preparation of geopolymer bricks, masonry Read More ...

Comparison of Reinforced and Pre-Stressed Concrete Building Frames

Comparison of Reinforced and Pre-Stressed Concrete Building Frames This article discusses pre-stressing of concrete to get lighter and slender beam sections for six different four storied concrete building frames of different spans/lengths by the application of post-tensioning Read More ...

Ready Mix Concrete in India With Quality Assurance

Ready mix concrete (RMC) is the first choice for projects requiring concrete. The term ‘ready mix’ is used to describe a process where concrete is pre-made at a plant and delivered in batches to job sites. It is a convenient Read More ...

Mechanical Properties of Geopolymer Concrete with Alternative Materials

Concrete is considered the world’s most versatile, durable and reliable construction material, next only to water. It is the most consumed material requiring large quantity of cement, fine aggregates, course aggregates Read More ...

Ferro-Sialate Geopolymer using Red Mud

Geopolymer is being used as a replacement for Portland cement for over the past three decades. The technology utilizes material rich in silica and alumina, either processed geological material or industrial byproducts Read More ...

Geopolymer Concrete - The Eco Friendly Alternate to Concrete

The name geopolymer was given by “Joseph Davidovits” in 1978. Geopolymer concrete (GPC) is an eco friendly product which uses industrial waste by-products such as fly ash (waste from thermal power plants) and ground Read More ...

Compressive strength study of Geopolymer Mortar using quarry rock dust

T. Venu Madhav, Head Department of Civil Engineering, Audisankara College of Engineering & Technology, Gudur, Andhra Pradesh, India. I.V. Ramana Reddy, Professor, Department of Civil Engineering, S.V.U. College of Engineering Read More ...

Use of Factory Made Reaction Generating Liquid (RGL - SRGPJ1) to Produce Geopolymer Concretes

Geopolymer binders, formed by alkaline activation of aluminosilicate precursors, are attracting interest as “green” cements because of their use of industrial wastes such as geothermal silicas, fly ashes and mineralogical Read More ...

Performance Evaluation of Fly ash and GGBFS Blended Self-compacting geopolymer concrete

An attempt has been made to develop Fly ash (FA) and Ground granulated blast furnace slag (GGBFS) blended self-compacting geopolymer concrete mixes with varying volume of pastes using conventionally available river sand Read More ...

Robustness of Self-Compacting Geopolymer Concrete (SCGC)

It’s widely known and has been reported on numerous occasions and in multiple journals that concrete is one of the most used construction materials in the world. With current cement production in excess Read More ...

New Building Material & Construction World

New Building Material & Construction World
MGS Architecture

Modern Green Structures & Architecture

Modern Green Structures & Architecture

Lifting & Specialized Transport

Lifting & Specialized Transport

Indian Infrastructure & Tenders Week

Indian Infrastructure & Tenders Week
Sign-up for Free Subscription
'India Construction Week'
Weekly e-Newsletter on Construction Industry
Get the latest news, product launches, projects announced / awarded, government policies, investments, and expert views.
Click here to subscribe.