Performance assessment of bricks and prisms: Red mud based geopolymer composite

doi:10.1016/j.jobe.2020.101462

Journal of Building Engineering

Volume 32, November 2020, 101462

https://doi.org/10.1016/j.jobe.2020.101462 Get rights and content

Highlights

•
A performance study of red mud based geopolymer brick is investigated.
•
Influence of red mud on brick strength is studied.
•
Effect of partial replacement of sand with GBFS is assessed.
•
Strength and masonry efficiency of prism cast using geopolymer bricks is evaluated.
•
An empirical formula relating masonry strength as function of brick and mortar strength is proposed.

Abstract

Most of the building construction worldwide use bricks as building material for masonry construction. Use of geopolymer bricks using industrial waste is a sustainable alternative to conventional bricks. The present study assesses the feasibility of using red mud based geopolymer bricks in masonry for structural applications. Granulated blast furnace slag (GBFS) was used as a partial replacement of sand in casting bricks. Mechanical property of bricks was evaluated and the results analysed. The optimum percentage of red mud was found to be 30% but the bricks cast with 50% red mud too, exhibited good dry compressive strength of 8.7 MPa with 1:1 binder: aggregate ratio. In general, strength and stiffness of bricks increased when sand was partially replaced with GBFS. Ultimate strength and masonry efficiency of prisms cast with geopolymer brick and cement mortar proved to be better than those cast with geopolymer mortar.

Graphical abstract

Introduction

Bricks form a vital fragment of building constructions. India is the second largest producer of brick worldwide, producing 236 billion bricks in a year with an annual increase of 5–10% [1,2]. Bricks/blocks can be categorised based on the method of production as fired, cemented and geopolymerised. Fired and cemented bricks may not be a popular method as they consume lot of energy and have carbon footprint. Carbon footprint of fired brick produced in India is 0.15 tonne CO₂/tonne [[3], [4], [5]] whereas for concrete block it is around 0.1 tonne CO₂/tonne [6]. The more favoured choice considering energy consumption, environmental impact and sustainability would be geopolymer bricks/blocks.

Some amount of research has been undertaken on the synthesis and evaluation of properties of geopolymer bricks and blocks. Saeed Ahmari and Lianyang Zhang [7] studied the feasibility of synthesising pressure-formed geopolymer bricks from copper tailings by adding water glass. An investigation on the effect of molarity, forming pressure, curing temperature and water content on the physical and mechanical property was made. Bricks made with 15 M NaOH solution showed greater strength than those with 10 M solution at all curing temperatures. The strength of the bricks increased as curing temperature rose from 60 to 90 °C, beyond which there was decline in strength. The rise in temperature resulted in faster dissolution rate and also faster condensation at later stage. When temperature was too high, condensation interfered with further dissolution process, resulting in loss of strength. Maximum strength was reported to be 33.7 MPa for bricks cured at 90 °C for 7 days, having 18% water, 15 M NaOH concentration and 0.2 MPa forming pressure.

In another investigation, Saeed Ahmari and Lianyang Zhang [8] studied the effect of adding cement kiln dust (0 to 10%) to the copper mine tailing brick cured at 90 °C for 7 days. The presence of cement kiln dust (CKD) enhanced the strength and durability of bricks. This could be attributed to the increase in Si and Al ions, rise in alkalinity due to addition of CKD. Also, calcium ion was transformed into CaCO₃ and co-existed with the geopolymer gel. The durability of brick increased as CaCO₃ had low solubility in water and alkaline solution. The Ca from CKD precipitated as CaCO₃ and not CSH gel because curing at higher temperature favoured geopolymer reaction and inversely affected hydration reaction. Chao-Lung Hwang and Trong-Phuoc Huynh [9] studied the effect of partial replacement of fine aggregate (0 to 40%) by unground rice husk ash in the production of fly ash construction bricks. Fly ash and rice husk ash in the ratio of 3:2 were used as binder, and unground rice husk ash was used as partial replacement for fine aggregate (0 to 40%). Bricks of size 220 × 105 × 60 mm were cast into steel moulds by forming pressure of 35 MPa. Alkaline solution comprised of sodium hydroxide and sodium silicate solution with SiO₂/Na₂O ratio of 0.81. Molarity of NaOH used was 10 M and solid-to-liquid ratio was 0.4. Bricks were cured at 35 °C and 50% relative humidity until the age of testing. There was reduction in compressive strength and flexural strength of the brick when unground rice husk ash was added. Compressive strength and flexural strength varied from 20.9 to 31.5 MPa and 5.7 to 6.7 MPa respectively after 28 days of casting.

Fly ash is most widely used raw material for geopolymerisation. Plenty of work still needs to be done in the field of geopolymer masonry units considering the wide variety of raw materials available for geopolymerisation and their different possible combinations. The industries generate huge amount of industrial wastes some of might be hazardous [10,11]. Such wastes that contain a substantial amount of alumina and silica could be a potential source of raw material for geopolymerisation. This not only helps in sustainable utilization of waste material but also immobilizes the toxic materials [[12], [13], [14]]. Red mud, an industrial waste produced during the extraction of alumina from Bauxite, is one of such potential raw material [[15], [16], [17], [18], [19]]. Not much work is done on red mud based geopolymer concrete products. The aim of the present study is to synthesize red mud based bricks and assess its properties in terms of water absorption, dry density, compressive strength. Effect of partial replacement of sand by GBFS on its mechanical properties is also investigated. Applicability of the bricks is examined by casting prisms, testing them for the compressive strength, stiffness and masonry efficiency. The obtained results are analysed and compared with the existing codal standards.

Section snippets

Materials

Red mud and fly ash were used as binder along with alkaline solution of molarity 10 M. Red mud was obtained from Hindalco refinery, Belgaum, Karnataka, India. Initially, it was in the form of boulders, which were coarsely ground to break down the bigger lumps in order to carry out research, as has been shown in Fig. 1a. The ground red mud was passed through 300-μm sieve in order to ensure uniformity in test results. The alkalinity of red mud was found to be 11.1 and specific gravity 3.25. The

Methods

The method for the synthesis of geopolymer brick comprised of casting, curing and testing. The percentage of red mud in the binder varied from 10% to 50%. Sand was replaced by GBFS from 0% to 50%. Alkaline solution mix of 10 M and Na₂SiO₃/NaOH ratio of 2.5 was prepared one day prior to the casting of bricks. Initially, all dry constituents were added in the Hobart mixer and made to rotate at low speed. The alkaline solution was added to the mixer while it was still running, and its speed

Water absorption and bulk density

Results for water absorption and bulk density of geopolymer bricks have been listed in Table 7. Fig. 6 shows the trend of water absorption with red mud content and Fig. 7 indicates its dependency on varying percentages of GGBS. There was slight increase of about 5% in the percentage of water absorbed as the red mud percentage increased from 10% to 30%. This need not entirely be indicative of porosity. Part of water utilised could be expended in reaction with Na₂O or CaO. Sum of these oxides was

Conclusion

The study focusses on analyzing the properties and behavior of sustainable masonry using red mud and other industrial wastes such as fly ash and GBFS. The red mud based brick possessed excellent mechanical properties and was aesthetically very pleasing. Presence of red mud favours geopolymerisation and improves compactness but leads to increase in the number of shrinkage cracks. The optimum red mud percentage in the binder was found to be 30%. The addition of GBFS as a partial replacement of

CRediT authorship contribution statement

Smita Singh: Investigation, Data curation, Writing - original draft. M.U. Aswath: Conceptualization, Resources, Project administration. R.V. Ranganath: Supervision, Writing - review & editing.

Declaration of competing interest

The authors declare that they have no conflict of interest.

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Performance assessment of bricks and prisms: Red mud based geopolymer composite

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Materials

Methods

Water absorption and bulk density

Conclusion

CRediT authorship contribution statement

Declaration of competing interest

Construct. Build. Mater.

Habitat Int.

Construct. Build. Mater.

J. Clean. Prod.

Construct. Build. Mater.

Construct. Build. Mater.

Construct. Build. Mater.

J. Hazard Mater.

Int. J. Inorg. Mater.

Construct. Build. Mater.

Int. J. Miner. Process.

Construct. Build. Mater.

Case Stud. Constr. Mater.

Fuel

Construct. Build. Mater.

Ceram. Int.

Cement Concr. Res.

Ceram. Int.