Development of energy efficient organic bricks in construction using IOT and perlite

ABSTRACT

The study focuses on improvement of bricks in mechanical properties, reduction of energy consumption, making more economical and environmentally friendly by saving the depleting resources. The bricks were mixed in different proportions, by replacing sand with Iron Ore Tailings from 30 to 60 percent at 10 percent interval, cement from 10 to 20 percent at 5 percent interval and perlite at 2 and 5 percent to make bricks of 230 mm×112.5 mm×75 mm dimensions. The bricks were tested for compressive strength, water absorption and thermal conductivity. From these tests among different combinations, IOTs:Sand:Cement:Perlite 50:25:20:5 combinations have yielded better results by satisfying Indian Standard (IS) codes and this is taken as optimum dosage of raw materials. Model rooms are constructed using these bricks to access the effectiveness of thermal conductivity to compare with the ordinary conventional brick (fired brick) room, both rooms are of the same dimension and exposed to same environmental conditions. Thermal conductivity is assessed by measuring the temperature on walls of all sides of the room at different timings of the day. The results revealed that heat transferred from the outside to inside of the walls of the model room constructed with IOT-perlite bricks was at least 2°C less compared with that of ordinary bricks. Lower thermal conductivity leads to energy savings and results established 8 percent of energy savings with IOT-perlite bricks. The study proved the eco-friendly bricks by using the mine waste, lower thermal conductivity, good strength and light weight in structure.

KEYWORDS:

• Brick
• iron ore tailings
• perlite
• thermal conductivity
• energy saving

1. Introduction

Clay brick manufacturing is a sector which involves a lot of firing processes requiring higher temperature. To maintain this temperature, large amount of fuel in the form of wood, coal, biomass etc. need to be burnt in the kiln causing serious issues of air pollution.

Preparation of clay brick need high temperature which involves different process of firing and require lot of fuel consumption in the form of wood, coal, biomass, etc and this process causes the air pollution (Mary et al. 2018). There are certain issues regarding energy, carbon emissions and sustainability of building construction (Venkatarama, Reddy 2009). Rapid industrialisation has contributed to existing problems of solid waste generation and its disposal (Sakhare and Ralegaonkar 2016). In the absence of utilisation of these accumulated solid wastes, they are a burden to industry and a threat to the environment (Madurwar, Sakhare, and Ralegaonkar 2015). Hence, a need of environmentally friendly and economically viable brick production is increased. Stabilised bricks are a type of bricks that have low embodied energy of 0.42 MJ/Kg and a low carbon footprint. Many researchers have experimented with different recycled materials such as coconut fibre, granite waste, waste glass sludge, rice husk, sugarcane bagasse ash and eggshell powder to obtain better properties than conventional bricks (Nithiya et al. 2016). In order to improvise the quality, properties and to make eco-friendly bricks – fly ash, Ground-granulated blast-furnace slag (GGBS), iron ore tailings, vermiculite and perlite are used as industrial wastes. Syed et al. (2017) studied to explore the potential use of waste glass sludge (WGS) as a secondary material in clay brick manufacturing. Clay bricks incorporating WGS exhibited higher compressive and flextural strength as compared to that of traditional clay brick. The thermal conductivity of the brick increased after incorporation of 25% WGS (Syed et al. 2018a). Sutas, Mana, and Pitak (2011) determined the addition of rice husk ash by 2% over rice husk will improve the properties of bricks.

Non-burnt bricks are preferred for construction to prevent environmental pollution and the use of industrial byproduct materials is essential in bricks without compromising structural soundness. Shubhananda Rao, Gayana, and Ram Chandar (2018) reviewed the use of iron ore tailings in infra projects. Gayana and Ram Chandar (2018a, 2018b) investigated the use of iron ore waste in concrete pavements. Ram Chandar et al. (2019) used PS balls on the performance of concrete.

Tremendous environmental problem are rising in construction industry due to leading urbanisation (Mokal et al. 2015). The real estate industry is a significant contributor to the global warming from energy use in the building (Tanju, Khitoliya, and Singh 2016). Since the large demand has been placed on building and construction material industry especially in the recent past owing to the increasing population which causes a chronic shortage of building materials, the civil engineers have been challenged to convert the industrial wastes to useful buildings and construction materials (Scinduja et al. 2014).

As most of the construction materials are obtained locally but excessive demand resulted in the extraction of these depleting resources beyond the limit and it has adversely affected the environment. This has resulted in an acute shortage of fine as well as coarse aggregates, obligating to explore the replacement for these materials without compromising the quality, environmental and economic factors. One of the replacement opportunities comes from industrial waste. The iron ore mining industry generates the waste in the form of Iron Ore Waste (IOW) and Iron Ore Tailings (IOT) on a large scale in the process of quarrying and preparing the material ready for iron and steel industry. It is a herculean task for these mining industries to dispose of the mine wastes. To overcome these problems a systematic study is carried out to use IOT in manufacturing bricks which resulted in minimising the impact of pollution on the environment, solves the problem of disposal and this byproduct is freely available for making the bricks more economical.

The raw materials used in this research are iron ore tailings, perlite, locally available sand and Ordinary Portland Cement of grade 53. Zone I sand is used for casting of bricks. IOT samples were collected from the tailings dam of Mining Company in Bellary district of Karnataka State using a random sampling method and perlite was procured from M/S. Keltech Energies Limited (KEL), Vishwasnagar, Udupi District of Karnataka which is been used in many products.

The Iron ore tailings is a siliceous material having higher density, when used in the production of the bricks results in a heavier product which demands a stronger framed structure of the building. To reduce the cost of the building, lighter materials are used to overcome the problem. The perlite as an admixture used to reduce the weight of the brick which is a volcanic rock with a density of 0.03 gm/cc is used in the brick as a density controller. Perlite has many folded benefits like lower density, low thermal, acoustic conductivity and many good properties. The combination of IOT and perlite helped in achieving the objectives of the research.

2. Literature review

There are lots of researches done on bricks, local construction materials, reuse of industrial wastes, environment sustainability which are studied well before fixing the objectives, aims and route map to achieve the goal of research. The research gap is identified after the intensive literature review and decided to put an effort on contributing something to environment and to safeguard the depleting resources by developing energy efficient eco-friendly bricks using industrial waste. Some of the studies by previous researchers are discussed below;

Manoharan et al. (2012) used alluvial clay in the production of ceramic bricks and compared with red clay bricks for its properties such as compressive strength and thermal analysis along with elemental and mineralogical study. Based on the test results, ceramic brick using alluvial clay resulted in high compressive strength and low water absorption in comparison with red clay bricks. The mineralogical studies showed the presence of quartz, plagioclase, illite, kaolinite and chlorite for the alluvial clay and quartz, kaolinite, haematite and goethite for red clay brick. The red clay deposits contained well crystallised kaolinite, whereas the alluvial clay deposits were poorly crystallised kaolinite. A comparison of the DTA curves of the alluvial clays and the red clay materials reveal an endothermic effect with a peak at 300ºC did not appear in the alluvial clays. All the four clays show an endothermic peak corresponding to α-quartz to β-quartz transformation at 600ºC is clearly visible. Therefore the amount and conditions of transformation of quartz in clays impact on the thermal transformation.

Gokhan and Osman (2013) investigated the effects of rice husk addition on the porosity and thermal conductivity properties of fired clay bricks. The raw material added in two forms as ground rice husk and coarse rice husk and rice husk was substituted by volume (5%, 10% and 15%) to brick. The brick with the 5% and 10% addition of rice husk to brick clay exhibit a compressive strength of 7 to 10 MPa which is smaller than the reference clay bricks but it satisfies the TS EN 772–1. The reference clay brick gives the highest thermal conductivity at all firing temperature. It has been determined that samples added with coarse rice husk in brick have lower thermal conductivity than samples added ground rice husk.

El, Fgaier et al. (2015) conducted an experiment on thermal properties of earthen bricks at a laboratory and used in the construction of a building to observe its thermal efficiency for 2 years. The results have shown that the earthen walls were efficient in reducing the variations of the outside temperature.

Kuranchie (2015) carried out an investigation on load settlement behaviour of iron ore tailings as a structural fill material. The structural fill material of iron ore tailings showed higher load bearing capacity and the stiffness when compare to conventional fill materials by obtaining the higher value of 22 and 13.5 times respectively.

Georgiev et al. (2017) studied on effect of expanded vermiculite and expanded perlite as pore forming additives on the physical properties and thermal conductivity of porous clay bricks. The bricks of two pore-forming additives as expanded vermiculite and expanded perlite have been established by varying the composition of 0, 3, 5 and 8 mass %, fired at 900°C.The thermal conductivity of the brick without additive was 1.1 W/mK and decreased to 0.8 W/mK, when the brick had 8 mass % vermiculite. To improve the thermal conductivity of clay brick, keeping the acceptable compressive strength, expanded vermiculite and expanded perlite in amounts of 8 mass % could be used in bricks as a pore forming agents.

Syed et al., (2018b) investigated on thermal performance enhancement of eco- friendly bricks incorporating agro-wastes. The burnt clay bricks are manufactured by incorporation of sugarcane bagasse ash (SBA) and rice husk ash (RHA) in dosage of 5%–15% at 5% interval by clay weight. The 15% addition of this agro wastes resulted in lower compressive strength but satisfied the standard requirement with an additional advantage of decrease in thermal conductivity.

Munir. et al. (2018) carried out the study to utilise waste marble sludge (WMS) in the production of energy efficient burnt clay bricks on industrial scale. The WMS is added in proportion of 5%, 10%, 15%, 20% and 25% and physico-mechanical and thermal properties are examined. The brick resulted in satisfactory compressive strength and showed increase in water absorption with increasing WMS content in clay brick. The clay brick of 15% WMS addition resulted in decrease in thermal conductivity by about 16% reduction.

Li et al. (2019) discussed and concluded about recycling of industrial waste iron ore tailings in porous bricks with low thermal conductivity. The results showed that sintering temperature, soaking time and milling time had significant effects on porosity, compressive strength and microstructure of the porous tailing ceramics. There was an increase in compressive strength when soaking time was extended; meanwhile sintering temperature was decreased with similar porosity. The thermal conductivity of the porous tailing bricks could reach the lowest value of 0.032 W/mk with the porosity of 89%.

3. Experimental investigations

The bricks were casted using varying compositions of materials such as cement, sand, iron ore tailings and perlite. These were mixed in different proportions, by replacing sand with Iron Ore Tailings from 30 to 60 percent at 10 percent interval, cement from 10 to 20 percent at 5 percent interval and perlite at 2 and 5 percent. Six bricks for each varying proportion are casted to determine the exact values for compressive strength, water absorption and thermal conductivity.

The strength of brick is more when IOT addition is increased from 30% to 60% and reduced by increasing the addition of perlite. But the addition of 5% perlite showed more advantage in reducing the density of brick. The increase in percentage of IOT and perlite showed more water absorption. The addition of 20% cement increased the compressive strength and reduced the water absorption. But 50% IOT and 5% perlite at 20% cement obtained better result in water absorption and it satisfies the IS standard. Thermal conductivity of brick is less at 5% perlite addition and more when IOT content is increased. Hence the optimum percentage of raw materials was determined as iron ore tailings (IOT) 50%, sand 25%, cement 20% and perlite 5% based on these laboratory experiments satisfied the IS standards interms of strength, water absorption and conducted thermal conductivity experiment according to IS code. The reduction in thermal conductivity by adding perlite to the brick is an added benefit to this study. The summarisation of minimum, maximum and optimum dosage of raw materials with its characteristics is provided in Table 1. Considering this optimum mix, a pilot-scale study is carried out to assess the thermal efficiency and the variation of temperature induced in a structure under different intervals of time. The study is carried out by constructing two model rooms. The first room consisted of conventional burnt bricks and the second room was constructed using the optimum mix of materials with iron ore tailings and perlite. A comparison study has been made to determine the efficiency of the modified bricks with iron ore tailings and perlite bricks. The details are discussed in the following sections.

Table 1. Summarisation of minimum, maximum and optimum dosage of raw materials and its characteristics

IOT (%)	Perlite (%)	Cement (%)	Sand (%)	Density (Kg/m^3)	CS (MPa)	WA (%)	TC (W/mK)	Remark
30	0	10	60	1754.32	3.56	17.99	1.491	With 30% IOT and 10% cement resulted in lower compressive strength, higher water absorption and increase in thermal conductivity.
60	5	20	15	1758.19	4.08	15.64	0.941	The dosage of 60% IOT and 20% cement yields higher in density, good strength, lower in water absorption and slightly higher in thermal conductivity.
50	5	20	25	1723.43	3.89	14.82	0.920	This yielded lower density, less compressive strength (but satisfies the IS standard), lower water absorption and less thermal conductivity. Hence it is considered as optimum proportion to prepare brick.

Note: CS – Compressive Strength, WA – Water Absorption and TC – Thermal Conductivity

Georgiev et al. (2017), concluded that 8% mass addition of expanded perlite and expanded vermiculite in porous clay bricks produced at 900°C is required to keep acceptable compressive strength and thermal conductivity. In this study, to meet the IS standard requirements in terms of compressive strength and water absorption, maximum of 5% of perlite is added but achieved other advantages like reduced pollution, lower embodied energy of the brick because of non – firing and using mining waste as raw material, resulting in environmental sustainability.

3.1 Description of the model rooms

To compare the results and to know the efficiency of the IOT-perlite bricks, two model rooms were constructed one of IOT-perlite bricks and other conventional fired bricks as shown in Figures 1 and 2) respectively. These two model rooms were built in similar condition like in elevation, dimension and height. It is constructed nearby, exposing to the same intensity of light and free from all obstructions.

Figure 1. View of model room constructed with IOT-perlite bricks

Figure 2. View of model room constructed with conventional bricks

The room of conventional fired bricks constructed and pointed with cement mortar 1:4 and IOT-perlite brick room with mortar of IOT, sand, cement and perlite mix as of brick with optimum ratio 50:25:20:5. Both the rooms are laid with plain cement concrete for floor and the roof is covered with asbestos cement sheet. The thickness of the wall is one brick thick having 60 cm wide door opening in east and a height of the room is 1.9 m with necessary slope.

3.2 Experimental procedure

To measure the surface temperature of inside and outside wall, Infrared thermometer (model CENTER 350 Series) is used. The device emits laser light on the surface and measures the temperature. The ambient temperature and the model room temperature are measured with the help of probe temperature metre (model V&A Instrument) which displays the temperature when the needle is extended into the medium of which to be measured.

To confirm the accuracy of the research results, temperature of the walls and the room measured daily three times in the morning, afternoon and in the evening.

To get the difference between ambient temperature and inside model room temperature probe temperature metre is used. Both the model rooms are measured simultaneously at various regular intervals of time as shown in Figures 3 and 4

Figure 3. Simultaneous measurement of the ambient temperature and outside temperature of the wall of conventional brick

Figure 4. Simultaneous measurement of the ambient temperature and outside temperature of the wall of IOT-perlite brick

The readings are noted using the Infrared thermometer device. The table shows the thermal behaviour of all the surface of outside and inside walls, room temperature, roof temperature of both the model rooms and atmospheric temperature. A typical data set of forenoon only is given in Table 2.

Table 2. Temperature measured during forenoon for IOTs-perlite brick wall and ordinary brick wall

	IOT-perlite Bricks						Time	Ordinary Bricks						Time
	Outside Wall (°C)			Inside Wall (°C)				Outside Wall (°C)			Inside Wall (°C)
	T	M	B	T	M	B		T	M	B	T	M	B
NW	25.50	25.50	25.00	22.00	21.50	21.50	10:07 AM	29.50	29.50	29.00	26.50	26.00	25.00	10:00 AM
EW	26.00	26.00	25.50	22.50	21.50	21.00		30.00	30.00	29.50	27.00	26.50	26.00
SW	25.50	25.50	25.00	21.50	21.00	20.50		29.50	29.00	28.00	26.00	25.50	25.00
WW	25.00	24.50	24.00	21.00	20.50	20.00		29.00	28.50	28.00	25.50	25.00	24.50
Roof				b/w 29.50 and 31.00				Roof			b/w 30.50 and 32.00
Room Temperature				25.00				Room Temperature			27.00
Atmospheric Temperature surrounding the constructed rooms – 29.00°C
T – Top (Temperature measured 1 foot below the top) M – Middle (Temperature measured at centre of the wall) B – Bottom (Temperature measured 1foot above the floor)								NW – North Wall EW – East Wall SW – South Wall WW – West Wall

3. Results and analysis

A pilot-scale study describes the effectiveness of iron ore tailings and perlite use in bricks. The internal and external surface of the constructed model rooms are measured and determined the thermal efficiency of IOT-perlite brick room by comparing the fired clay brick or ordinary brick room. Model brick rooms are tested before plastering.

A) Thermal performance of the model rooms at forenoon (8 am–10 am)

During 8 am–10 am ambient temperature surrounding the model room was 29°C. The readings were taken on the walls of all sides (N, E, W and S) to check the heat transfer, whereas heat is the form of energy transfer from high temperature location to a low temperature location. The sun rays falls on eastern side of the wall during forenoon, so the temperature at outside of east wall is more compared to other sides. In an average IOT-perlite brick walls results in 3–4°C less in temperature than ordinary bricks.

It is also concluded that temperature of the IOT-perlite brick walls in outer surface is less by 10% than ambient temperature, which is only 0–2% in the case of ordinary brick walls as shown in Figure 5(a,b,c). The temperature of IOT-perlite brick walls from outer to inner surface is reduced by 13%, but in case of ordinary bricks is 10% as shown in Figure 6(a,b,c). This concludes the ambient temperature is arrested by outer surface of the IOT-perlite brick walls by more than 10% and inner surface is atleast 3% less compared to that of ordinary brick walls. The room temperature of IOT-perlite bricks is less by 7% compared to that of ordinary bricks.

Figure 5. Temperature of outside of the walls at three points measured in the forenoon

Figure 6. Temperature of inside of the walls at three points measured in the forenoon

B) Thermal performance of the model rooms at mid-day (12 pm–3 pm)

The temperature readings taken on inside and outside walls of IOTs-perlite bricks and ordinary brick walls during 12 pm–3 pm plotted to know the difference in temperature occurred. The temperature results of the outer surface of the wall of model rooms are shown in Fig. 7(a,b,c) and on the inside of the walls of the model rooms are shown in Figure 8(a,b,c) respectively at three points in different directions.

The radiation from outside to inside walls is transferred by process of conduction through all directions which are seldom steady. The temperature at midday is higher at the east, north and south walls compared to the west wall. Ambient temperature is arrested by IOTs-perlite brick from outside surface is 5%, more when compared to ordinary bricks. The transfer of heat from outside to inside of the ordinary and IOTs-perlite brick is less by 13% and 14% respectively, ordinary bricks have shown 1% less temperature difference. But, by and large when the temperature of inside surface of the bricks is measured, IOTs-perlite bricks found slightly less compared to that ordinary bricks. It justifies that lower effect of radiation and conduction of the bricks made of IOT and perlite. The room temperature of IOTs-perlite brick room is 5% less than the ordinary brick room. It could be concluded that, in midday, the temperature at walls, floor and room of IOT-perlite bricks are low compared to conventional bricks, because perlite has good thermal resistivity.

Figure 7. Temperature of outside of the walls at three points measured in the midday

Figure 8. Temperature of inside of the walls at three points measured in the midday

C) Thermal performance of the model rooms at evening (4 pm–6 pm)

A similar procedure was followed in the evening (4 pm–6 pm) as in the case of measurement of temperature at forenoon and mid-day. The temperature was measured on top, middle and bottom sides of the IOT-perlite brick walls and conventional brick walls in all directions as shown in Figure 9(a,b,c) and Figure 10(a,b,c), on the outside and inside walls of the model rooms respectively.

Figure 9. Temperature of outside of the walls at three points measured in the evening

Figure 10. Temperature of inside of the walls at three points measured in the evening

The atmospheric temperature in the evening was noted as 28°C. The temperatures in each wall of the rooms (IOT-perlite bricks and ordinary bricks) are not same and it is varied by atleast 3% to 4%. Temperature of the IOT-perlite brick walls in outer surface is less by 3% than ambient temperature, which is only 0–1% in the case of ordinary brick walls. The radiation of the sun light is conducted in the IOT-perlite brick walls from outer to inner surface is less by 4%, but in case of ordinary bricks 2% temperature is lowered. This concludes the ambient temperature is arrested by outer surface of the IOT-perlite brick walls by more than 2% and inner surface is atleast 2% less compared to that of ordinary brick walls. The inside room temperature of IOTperlite bricks is less by 5% compared to that of ordinary bricks. It is concluded that the temperature is varied in all walls of the four sides, but on an average IOT-perlite bricks room results in 1–2°C less in temperature than ordinary bricks.

As per Kumar et al. (2019), by using clay hollow brick composite in the building (phase change material room) drops the temperature to 6°C and whereas in non-phase change material room drops temperature to 2°C, during various months of the year. Hence the difference is 4°C compared to non-phase change material room. The test room has the dimension of 3 m × 3 m × 3.65 m using clay hollow bricks and it is constructed at Chennai city, India in the warm and humid weather conditions.

But in the case of IOT-perlite brick room achieved 2°C compared to ordinary brick room. Here the raw materials used for the construction of room are IOT and perlite which is waste deposited material causing environment pollution. The research has used this mine waste to avoid the environment impact and to obtain savings in energy consumption. Although the reduction in room temperature not satisfies as per Kumar et al. (2019) but it provides non-fired bricks, environmental friendly, no fuel consumption and solution for mining waste disposal.

E) Thermal performance on room temperature by influence of time

To confirm the thermal efficiency of model room made of bricks with mine waste such as iron ore tailings and perlite, the room temperature is checked for longer duration. The temperature variation in IOT-perlite brick room and ordinary brick room are measured at a regular interval of 5 minutes for 55 minutes. It is noticed that the room temperature varies with a change in atmospheric temperature but maintain the average difference at all points of time. It is established that the temperature of the IOT-perlite brick room is less by 1–2°C compared to an ordinary brick room (Figure 11). This helps to prove the radiation, conduction and convection of heat through IOT-perlite brick is less compared to ordinary brick room, by maintaining difference in temperature proportionately throughout with the variation in ambient temperature.

Figure 11. Temperature vs time influence

4. Cost analysis

Cost analysis is done to determine the economic feasibility of IOT-perlite bricks in construction industry compared to the conventional bricks (fired bricks). The cost of the IOT-perlite brick is less by 4% and IOT brick without perlite which are used in load bearing wall is less by 38% compared to conventional brick. The calculation is based on actual cost of materials, labour and transportation for the cost analysis.

The analysis is also carried out to know the energy saved over the life cycle of the brick when used in the building construction. The analysis is done considering energy used by air conditioner (AC) as reference for IOT-perlite and conventional brick. The details are shown in Table 2. Air conditioner of 1.5 tonnes is considered for the calculation of percentage of energy saved. The wall temperature of the IOT-perlite bricks is less by 3–4^oC compared to ordinary bricks and all the time room temperature shows difference nearing 2 ^oC based on the variation of ambient temperature. The analysis is done when atmospheric temperature is 31°C, room temperature of IOT-perlite bricks and conventional bricks is 25°C and 27°C respectively. The setting temperature of AC was considered as 24°C to maintain the room temperature constant. The calculation process shown in Table 2 is as per ready reckoner given by The Energy and Resources Institute (TERI) (2018). With the similar controlled conditions, the power saved is around 34% for every Celsius degree increase in temperature (in degree). In terms of electricity for room size of 48 cubic metre, energy saved is 8% due to the low thermal conductivity of IOT-perlite bricks in comparison with conventional bricks. The percentage of cost saved per cubic metre per month is as per prevailing cost of the electricity charged by the local government.

Table 2. Energy and cost savings at different AC temperature settings

Atmospheric temperature at 31°C
Description	Room temperature (^oC)	Total energy used (kWh/day) (a)	Cost of using an AC		% of energy or cost saved vs 18°C per cubic metre per month
			(Rs. per day) (a) × 6.75	(Rs. per month) (b) × 30
			(b)	(c)
Initial temperature	18	13.00	87.75	2,633	NA
Fixed temperature	24	10.50	70.88	2,126	19.2
IOT-perlite Bricks	25	10.00	67.50	2,025	23.1
Conventional Bricks	27	9.0	60.75	1,823	30.8

Assumptions for cost analysis:

AC: 1.5 tonnes, 5-star rated window AC;

Energy consumption of AC: 1.3 KW/hr;

Electricity cost: Rs. 6.75 per unit;

AC functioning for 10 hours a day with each month having 30 days;

5. Conclusions

• The optimum dosage of raw materials for manufacture of brick is 50:25:20:5 (IOT:Sand:Cement:Perlite) which fulfils the compressive strength, water absorption and thermal conductivity as per IS standards.

• Atmosphere temperature is arrested at outside of the IOT-perlite brick wall before passing through the bricks and it showed lower temperatures at outside of the walls than the ordinary brick walls.

• The temperature of the inner surface of the walls in the room is reduced by 3–4°C in IOT-perlite brick walls compared to that of ordinary brick walls. It’s also noticed that inside temperature of the room, constructed by IOT-perlite bricks on an average is less by 2°C compared to ordinary bricks as it is established in the temperature and time influence graph.

• This observation proved the thermal efficiency of non-fired IOT-perlite bricks.

• Mortar used in the construction of IOT-perlite brick wall is of same proportion of brick materials, which was found to be suitable as it has given a homogenous structure.

• The room temperature of IOT-perlite bricks is less by approximately 2°C compared to ordinary brick room which saves the 8% of energy by way of electricity.

• In addition to the above, usage of mine waste in the form of iron ore tailings reduce the burden on depleting naturally available river sand and clay, on the other hand, disposal and maintenance cost of tailings will be a big saving to the mining and mineral industry and immediate use of IOT without storing reduces the environmental effect on the surroundings. As the bricks are non-fired, it results in lower embodied energy and also acts as energy conservative. The manufacturing of IOT-perlite bricks are free from fuel consumption and causes no pollution, overall it reduces its impact on the environment.

Disclosure statement

On behalf of all authors, the corresponding author states that there is no conflict of interest.

Additional information

Funding

There is no funding from source

Notes on contributors

P Shubhananda Rao

P. Shubhananda Rao obtained his M.Tech degree in Construction Technology & Management from the National Institute of Technology Karnataka (NITK), Surathkal, and now pursuing his Ph.D degree from the same Institute.  He is running his own construction business.

K. Ram Chandar

Dr. K. Ram Chandar is a graduate in Mining Engineering, M.Tech from IIT-BHU and Ph.D from NITK- Surathkal. He has almost 20years of teaching, research experience at NITK. He has involved in 7 R&D and around 100 Industry-sponsored consultancy projects, published around 90 research papers. He has received many National awards like ISTE- Young Teacher award, IE-India Young Engineer award, MGMI-Engineering Gold Medal etc. He is a fellow of the Institute of Engineers (India) and a life member of more than 10 professional bodies like ISRM, MEAI, ISTE etc. Presently he is serving as Associate Professor and Head of the Department of Mining Engineering at NITK in India.