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Benefits of Engineered Masonry on Embodied Energy of Buildings

Compressed Earth Block Masonry

Preamble

Structural Masonry is aesthetic, cost effective and easy to build. It offers so many optimal options that one would be surprised at the range of design possibilities, all of them "truly green" in construction. In common civil engineering terms, structural masonry is sometimes referred as "load-bearing" construction systems. Currently, "framed-RC" system is quite popular, especially in the urban context where the need is to maximize the number of floors. Both the systems possess relative merits and demerits. However, from the embodied energy perspective, structural masonry may be a better alternative, especially for low to moderate height buildings in the Indian context, although in many developed countries masonry is commonly used in construction of multi-storeyed buildings.

Conventional (or traditional) masonry refers to the load-bearing construction system where available bricks/stones/blocks are used in 'as-produced' condition as opposed to engineered masonry where blocks are 'engineered' to a desired strength, shape, texture, colour, weight and to extract a desired structural performance. Obviously, engineered masonry possesses far greater structural advantage over traditional masonry. Of late, engineered masonry is exploited to derive the architectural aesthetics. Engineered Hollow Concrete Blocks and Stabilised Mud Blocks are two such materials.

Energy is consumed by all the processes associated with the production of a building, from the acquisition of natural resources to product delivery, including mining, manufacturing of materials and equipment, transport and administrative functions. The embodied energy is the energy requirement to construct and maintain the premises, for example, with a brick wall, the energy required to make the bricks, transport them to site, lay them, plaster, paint and re plaster over the life of the wall. Best practice would also include energy calculations for demolition and recycling.

This paper presents the embodied energy computation of two types of load-bearing construction systems. Both the buildings serve similar functional requirement viz. as institutional buildings. One of the building has been constructed using Engineered Hollow Concrete Blocks with reinforced masonry also as some structural components, the other building bas been constructed using Stabilised Mud Blocks. The computations from the case studies clearly reveal that structural masonry consumes far less amounts of embodied energy compared to framed RC systems.

Introduction

Engineered masonry has lot many specific advantages. Some of them are briefed hereunder;

1. Modularity:  Modularity allows larger number of units to be produced which are of very high quality (factory level control), easy erection since construction becomes modular and very low wastage on site due to high quality. More the modularity, less the variation on site, and lesser the ultimate cost.
2. Mortar Saving in Joints:  Because of the high dimensional accuracy, the blocks can be laid with very thin mortar joints. 10 mm mortar joint is standard compared to nearly 25-35 mm for normal concrete blocks. It is possible to source cementitious adhesive which does not require curing and apply it as bedding mortar of only 5 mm thickness since the blocks are so perfect. This not only speeds up construction, it also saves curing water, thus environmentally sustainable.
3. Mortar saving in plaster:  Because of high dimensional accuracy, the blocks being of almost perfect size and shape, plastering can be reduced from the normal 25-40 mm thickness to less than 10mm. In most cases, it can be completely eliminated outside by just giving a waterproof coating.
4. Material Saving:  Mortar saving in joints and plastering leads to saving of sand and cement. In addition, we have to brace ourselves for the non-availability of river sand within a few years due to the overexploitation of sand mining. This move to us of Engineered Masonry Units (EMU) will mitigate the issues of non-availability of river sand.
5. Load bearing ability: These blocks are load bearing (the lowest strength being M6 compared to the generally available concrete block which is only M3.5 in strength). Hence, it is possible to build multiple storeys with EMU blocks without the use of an RCC framed structure. If rebar is required anywhere, they can be easily inserted vertically or horizontally into the blocks without the need for expensive and time consuming shuttering. Depending on the design, savings of up to 30 percent can be achieved by reducing the use of RCC. Reinforcement can be introduced almost anywhere – along the length of the wall and/or along the height of the wall, alternative load transfer paths are available. Masonry structures have more redundancies than moment-resisting framed structures where only discrete elements transfer loads.
6. Earthquake Resistance:  Easily adaptable to Earthquake resistant construction since rebar can be inserted horizontally and vertically anywhere. Thus structural masonry can be made ductile.
7. Weight advantage:  Since hollow blocks weigh lesser, the dead load is lesser on the structure and hence the structure can be designed more efficiently for a lower load.
8. Avoid un-necessary wet-works: Cast-in-situ lintels and chejjas (sun-shades) can be avoided using lintel and chejja blocks leading to better finish and faster construction.
9. Green Manufacturing:  Manufactured sand and Fly ash can be incorporated into the blocks with an optimal mix design to ensure a far lesser carbon footprint in the manufacturing process. Locally available soil can be utilized to produce SMBs using human energy and thus avoiding usage of fuels.
10. No formwork required: Masonry walls are ‘constructed’ using blocks and they do not need form-work as in framed construction and this minimizes the time and processes needed for wet-works.
11. Greater flexibility in terms of plan forms: Structural masonry plays a dual role – functional and structural and thus there is great flexibility in terms of plan forms.

Energy and Materials

Consumption of energy in the civil engineering scenario is huge as most of the materials and products constituting the construction materials require energy in one or many forms, from the time of extraction till it is used in the construction site. The usage of materials like cement, steel, aggregates etc has increased in the construction industry. These materials consume high energy in their manufacturing process. In order to quantify the environmental effects due to depletion of natural resources, the evaluation of embodied energy of different building materials is required. Optimal utilization of available resources is needed to ensure the energy consumed is low.

The embodied energy of some of the commonly used materials and masonry blocks are listed in Table 1.

Table 1- Embodied Energy of Different Materials

SI No	Material	Unit	Embodied energy (MJ/Unit)
1	Cement	kg	3.6
2	Coarse aggregate	cum	572
3	Fine aggregate	cum	29.58
4	Steel	kg	42
5	SSM	cum	104
6	Table moulded bricks (TMB)	Block	4.5
7	Hollow Concrete Blocks (HCB)	Block	12.3
8	Solid Concrete Blocks (SCB)	Block	15.5
9	Stabilized Mud Blocks (SMB)	Block	4.15

Computation of Embodied Energy of Buildings

There are a number of tools that have been developed to help assess embodied energy. Process analysis, statistical analysis, input output analysis and hybrid analysis are among the major methods used for embodied energy computation. These method possess have different limitations and their level of accuracy vary.

In the calculation of embodied energy of the building structure, there will always be uncertainty in:

• The amount of materials used
• The embodied energy of the materials
• The source and content of the materials

It is thus important to estimate the range of uncertainty of the input parameters such that the resulting uncertainty in the embodied energy of the building structure can be predicted and the most influential input parameters can be identified. This process is explained through Fig. 1. The methodology adopted includes the following steps.

• Identification of the building with alternative technologies
• Reconnaissance
• Preparation of measured drawing
• Component identification for the energy calculation
• Quantity estimation
• Embodied energy computation
• Comparison with the conventional system

Case Study 1

Institutional Building for Swami Vivekananda Youth Movement (SVYM)

Location and Description

The building is located in Swami Vivekananda Youth Movement Campus, Ring Road, Mysore. The building is designed as a G+3 storeyed masonry building, (Structural consultants: BMS-SMRC, BMS College of Engineering, Bangalore-19). Salient features of the building are,

• Total built up area - 1193.96 m²
• Building is constructed without any column and footings
• SSM foundation is adopted for load bearing walls, with reinforced plinth beam
• Masonry using Engineered Hollow Concrete Block is used as a dominant load bearing element
• Based on design consideration, few walls are built as reinforced masonry walls
• Wall plastering and ceiling plaster is avoided

The plan the general view of the building is shown in the Fig. 2 and Fig. 3 respectively.

The building is constructed with alternative building technologies and alternative building materials which lead to saving of materials/energy/cost. Some of them are the (i) manufactured sand (Fig. 4.), (ii) Engineered Hollow Concrete Block (EHCB) (Fig. 5), (iii) Masonry Lintel blocks (Fig. 6)

The foundation is constructed with conventional size stone masonry (SSM) with RC plinth beams constructed with U-block masonry. A view of the U-block RC plinth is shown in Fig. 7. Reinforcement was provided through the EHCBs to bear the point loads from beams, wherever needed (Fig. 8 and Fig. 9). The reinforcement was surrounded by grout concrete.  To enhance the structural integrity, through lintel beams using U-blocks were provided along the walls (Fig 10). Also, wall-beams were provided at the top most course of masonry wherein the RC slab was cast monolithically.

Embodied Energy Calculation

The embodied energy for various materials and components used in the building is calculated using the process stated earlier and is presented in Table 2. 

Table 2: Total Embodied Energy of the Building

SI No.	Material		Volume (cum)	Percentage Volume	Embodied Energy (GJ)	Percentage Embodied Energy
1	Masonry Unit	Size Stone	160.6	12.16	16.7073	1.00
		HCB 200 mm	388.6	29.42	194.336	11.58
		HCB 100 mm	4.8	0.36	2.412	0.14
		BBM	325.04	24.60	67.297	4.01
2	Mortar Quantity		146.7	11.10	137.2745	8.18
3	Concrete Quantity	1:1.5:3	23.9	1.81	36.0365	2.15
		1: 2:4	88.3	6.68	115.298	6.87
		RMC(M20)	179.3	13.57	250.357	14.95
4	Steel Quantity		3.8	0.29	858.539	51.14
Total			1321.04	100%	1678.84	100%

The total embodied energy of the building is 1678.84 GJ and the area of the building is 1193.96 m², therefore the embodied energy of the building is 1.41 GJ/m². Fig. 11 shows the pictorial representation of the percentage of embodied energy consumed by various materials. It is interesting to note that reinforcement steel is takes up a huge share of 51.14% although the volumetric presence is miniscule. This is to be expected since amongst all the major construction materials steel is the most energy consuming material. In an attempt to compare the embodied energy of the load-bearing system with that of an RC framed building, the same building was structurally re-designed as an RC framed structure with BBM as an in-fill material. Of course this system consists of footings, columns and beams which were not needed in the load-bearing system. The embodied energy of such a system worked out to 2.18 GJ/m², which is nearly 1.5 times that of the load-bearing masonry system.

The embodied energy for RC framed structure is calculated and compared with the Masonry structure. Embodied energy for both the building is shown in the Table 3 considering only basic materials. The energy comparison is shown for different materials for RC structure and Masonry structures in Fig. 13. In the case conventional RC framed structure the consumption of steel and concrete is more for column footing, columns, plinth beam and RC beams which leads to higher energy consumption for those components of the building. The embodied energy of the brunt brick masonry is more than the EHCB masonry with an added advantage of reduced mortar consumption in case of EHCB masonry.

Table  3: Embodied energy comparison for Masonry structure and RC framed structure

SI No.	Particulars	Masonry Structure		R C Structure
		Embodied Energy (GJ)	Percentage Embodied Energy	Embodied Energy (GJ)	Percentage Embodied Energy
1	SSM	16.71	1.02	16.49	0.65
2	Blocks	264.05	16.18	597.19	23.52
3	Mortar	137.27	8.41	218.81	8.62
4	Concrete	355.32	21.77	647.93	25.51
5	Steel	858.54	52.61	1059.15	41.71
	Total	1631.89	100	2539.57	100

Case study 2

Institutional campus of Dwarakanath Reddy Ramanarpanam Trust (DRRT)

Location and Description:

The building chosen for the study is facilitated by Dwarakanath Reddy Ramanarpanam Trust (DRRT). The Institutional campus is located at Gollahalli near Chikkaballapur district in Karnataka which is the district head quarters. The institutional building is not only a conventional school but also a training centre catering to the rural population in and around the village. The institution is partially run as a residential campus and hence hostel blocks are also provided.

Fig.13: Plan of Class room block

At present two class room blocks and two hostel blocks have been completed. The hostel block as well as class room block is two storied building. The ground floor of hostel block consists of five rooms and four toilets and one room and two toilets in the first floor. The roof includes masonry dome and the filler slab. The class room block consists of three class rooms in ground floor as well as in first floor. The plan for the buildings is shown in the Fig. 14 and Fig. 15. The area of class room block is 399 m² and for the hostel block it is 437 m². The general views of the buildings are shown in Fig. 16 and Fig. 17 respectively.

Fig. 14:Ground floor Plan - Hostel block

Fig. 16: Hostel Block - View of Dome

Fig. 17: Stabilized Mud Block (SMB) made at site

The institutional building is located in an interior rural region where the good quality table molded bricks were not available and the transportation of the concrete blocks would be expensive. The procurement of building materials at short distance i.e. the selection of locally material is important for saving energy and costs. These constraints lead to the choice of using Stabilized Mud Block for the construction. The SMB was made at site with manual labour using Mardini block making machine. A stack of SMBs made at site is shown in Fig. 18.

Fig. 18: Filler Slab

Cost consideration, architectural requirement and constraints at site necessitated the adoption of several alternative technologies for the buildings. Some of the alternative technologies being (i) RC slab with SMB filler blocks (Fig. 19), (ii) SMB dome (Fig. 20) and (iii) soil-cement mortar for exposed masonry (Fig. 21).

Fig. 19: SMB Masonry Dome with Ring beam - Inside View

Fig. 20: Masonry Dome - Exterior View

Fig. 21: Exposed Masonry

Embodied Energy Calculation

Embodied energy was computed using the similar process explained earlier. The major structural components identified for the computation of embodied energy is shown in Table 4.

Table 4: Structural Component Description

Sl. No.	Component	Description
1	Foundation	SSM in 5 layers
2	Masonry	SMB with composite mortar
3	Roof	Filler slab
4	Stair	RCC with concrete 1:1.5:3
5	Plinth	RCC with concrete 1:1.5:3
6	Lintel	RCC with concrete 1:1.5:3
7	Beam	RCC with concrete 1:1.5:3
8	Chajja	RCC with concrete 1:1.5:3
9	Flooring	PCC
10	Plastering	Around the openings, Exposed areas of beam, lintel and slab

The quantity of materials used and corresponding embodied energy for class room block and hostel block is presented in the Table 5 and Table 6 respectively. The embodied energy per area for class room block and hostel block is 1.59 GJ/m² and 1.73 GJ/m² respectively. Also presented in the table is the percentage of volume of material and percentage embodied of each material. One can discern easily those materials possessing high, like steel, is used in smaller quantities. For instance, flat RC roof is a component which is highly energy intensive, since it uses both steel and concrete. This is understandable, since such materials are invariably expensive and the engineering design demands the optimal use of such materials. Similar trend can be noticed the other buildings analyzed here.  These results of the class room block and hostel block are presented graphically in Fig 22 and Fig. 23 respectively.

The comparison of the share of embodied energy of different materials used in the class room block and hostel block is shown in Fig. 24. It can be noticed that the trends are similar. Indeed it is the roof and the wall which guzzle more than 50% of the share. Hence any alternative to reduce the embodied energy in these two components brings down the total embodied energy.

Table - 5: Volume and Embodied Energy - Class Room Block

SI No.	Material	Volume  (cum)	Percentage Volume	Embodied Energy (GJ)	Percentage Embodied Energy
1	Concrete	67.76	23.59	161.336	25.48
2	SSM	47.57	16.56	4.947	0.78
3	SMB	89.55	31.18	85.045	13.43
4	Mortar	33.12	11.53	53.658	8.47
5	Filler block	6.54	2.28	4.512	0.71
6	PCC	7.2	2.51	17.143	2.71
7	Mortar pointing	0.52	0.18	0.334	0.05
8	Reinforcement Steel	0.58	0.2	191.470	30.23
9	Door and window frames	0.11	0.04	36.313	5.73
10	Flooring	31.63	11.01	75.311	11.89
11	Plastering	2.63	0.92	3.222	0.51
	Total	287.21	100	633.291	100

Table - 6: Volume and Embodied Energy- Hostel Block

SI No.	Material	Volume(cum)	Percentage Volume	Embodied Energy (GJ)	Percentage Embodied Energy
1	Concrete	63.37	16.96	150.884	19.91
2	SSM	85	22.74	8.841	1.17
3	SMB	125	33.44	118.707	15.67
4	Mortar	46.23	12.37	74.897	9.89
5	Filler block	1.21	0.32	0.832	0.11
6	PCC	13.12	3.51	31.239	4.12
7	Mortar pointing	0.76	0.2	0.483	0.06
8	Reinforcement Steel	0.67	0.18	221.180	29.19
9	Door and window frames	0.22	0.06	72.626	9.59
10	Flooring	36	9.63	75.311	9.94
11	Plastering	2.17	0.58	2.661	0.35
	Total	373.75	100	757.661	100

Fig. 23: Percentage Volume and Embodied Energy- Hostel Block

Comparison of Embodied Energy of different structural configurations

It would be a useful exercise to make a comparison keeping the floor plans or architectural plans the same. As done for the EHCB building at Mysore, a similar exercise has been carried out here as well. The class room block and the hostel blocks were designed as RC framed systems with different in-fill materials and the embodied energy computation has been made. The different structural system include load bearing SCB, load bearing EHCB, load bearing TMB and RC framed system. The results are presented in Table – 7 and 8 along with Fig. 25.

One can see some interesting results here;

• Had SMB masonry been replaced by conventional Solid Concrete Block (SCB) masonry the respective embodied energy values would have marginally reduced. This is because of the lower amounts of mortar (since SCBs are bigger than SMBs and as such there are lesser mortar joints).
• Had Engineered Hollow Concrete Block (EHCB) been used instead of SMB the energy consumed would reduce to 1.45 GJ/m²and 1.62 GJ/m² respectively. 
• TMB is the most energy guzzling masonry material amongst all the three. Not only does TMB need more amount of energy for production, the mortar consumption is also quite high.
• TMB in South India generally has more dimensional variances, unlike wire cut bricks. As a consequence of this, it is a practice to plaster the surface to cover up the undulations. Also, as the quality is relatively poor, this necessitates the wall surface to be plastered. Mortar used for plastering is a high energy material and thus adds to the embodied energy.

Table - 7: Details of different masonry blocks

SI No	Material	Block Size    (mm)	Embodied Energy Values (MJ/Block)	Mortar %
1	SMB	230×190×100	4.15	27
2	SCB	400 ×200×200	15.5	8
3	EHCB	400 ×200×200	12.3	5
4	TMB	230× 105 ×75	4.5	20

Table - 8: Embodied energy-Comparison with different load bearing masonry-Class room block and hostel block

SI No	Structural System	Embodied energy (GJ/m2)
		Class room block	Hostel block
1	Load bearing SMB	1.54	1.72
2	Load bearing SCB	1.5	1.7
3	Load bearing EHCB	1.45	1.62
4	Load bearing TMB	1.95	2.24
5	Framed RC	2.28	3.0

Concluding Remarks

Fig. 25: Embodied Energy for Different Structural System - Class Room Block and Hostel Block

Building is a complex combination of many processed materials, each of which contributes to the total embodied energy. Generally, the focus of energy auditors have been on understanding the energy use during the operational period of the building (use phase). This is understandable for engineering components such as automobiles, electrical appliances, engines etc. where the operational energy is extremely high compared to the embodied energy. Embodied energy is also a major indicator of the environmental impact, in terms of carbon dioxide emissions and natural material resource depletion. It is extremely important for civil engineers to get a feel of the quantum of embodied energy utilized in buildings and ensure that future engineering designs consider them as an important design parameter that needs optimal solution, just like cost. As buildings become more energy-efficient, the ratio of embodied energy to lifetime consumption may increase. Clearly, for buildings aspiring to be designed as ‘zero-energy’ or 'autonomous', the energy used in construction and final disposal takes on a new significance. It is in this context that one needs to quantify and compare the embodied energy of a variety of building materials and technologies.

The computations from the two case studies clearly indicate that load-bearing masonry in general and Engineered Masonry in particular is surely a low-energy alternative to conventional RC framed system especially for low-rise structures. More importantly, of late, alternative technologies and materials have been gaining acceptance, possibly for multiple benefits it offers - cost, aesthetics, ease of construction and structural benefits. Perhaps, low-embodied energy is a by-product of this choice.

Acknowledgements

The first case study chosen is the recently completed "Sadhana", administrative block and class room block of Swami Vivekananda Youth Movement, Mysore. The authors gratefully thanks wish to thank the authorities of SVYM for permitting the data collection from their campus, especially Dr. R B Balasubramaniam and Sri Ramesh Kikkeri. Special thanks to Sri. N R Ashok, ACE Consultants, Mysore.

The authors wish to thank Padmashree Smt. Anita Reddy of DRRT for gratefully permitting the data collection of their building at DRIK-VIVEKA campus, Chickkaballapur. Many thanks to Sri. Ramesh, Engineer, DRRT and Sri. Amarnath, Contractor.

Authors

Jitha P T and Shivaprasad K N, Post graduate students (Construction Technology), Varsha BN, Research Scholar, Raghunath S, Professor, Department of Civil Engineering, BMS College of Engineering, Bangalore 560019

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