Experts recommend mud concrete blocks | Sunday Observer

Experts recommend mud concrete blocks

Prof. Rangika Halwathura removing the moulded bricks
Prof. Rangika Halwathura removing the moulded bricks

 “What we need is a house, a place we could call a home and pass it down to our children,” was the plaintive cry of Meena, the 56-year old grandmother, the Sunday Observer spoke to on October 18, while visiting Killinochchi to report on the government´s latest initiative to provide houses to 50,000 families in the North and the East.

As our sister paper, the Daily News reported last week, the Request for Proposals (RFP) called by the Ministry of National Integration and Reconciliation for the houses continues to cause concern for the experts and the community alike.

Last week, at the pre-bidding meeting called by the Ministry to discuss the RFP, Ministry Secretary V Sivagnanasothy was quick to say that due to issues that arose out of the previous 65,000 house RFP, where the Luxembourg based Arcelor Mittal housing proposals were rejected, as not suitable, the veering away from the given list of materials will not be a good idea.

However, he said that if any bidder would like to propose alternative material, those proposals will be considered.Separate, single-window proposals also can be considered to meet other housing needs.

The issue with this stance, according to experts interviewed by the Sunday Observer is that the cost of a housing unit will be over Rs 1.9 million, if the bidders strictly follow the employer requirements as listed in the RFP.

As the cost spirals up, with non-governmental agencies such as the Red Cross and Habitat for Humanity constructing houses of exactly the same size and quality, at a lesser cost using innovative materials and methods, experts fear the 50,000 houses will also go the same way as the previous RFP for 65,000 houses. “We are going from one extreme – cheap, climatically unsuitable, non- long lasting to the other- the expensive, highly durable, and ultimately unsustainable, which will, at the end, result in 70,000 families being without proper housing when the term of this government ends in 2020,” one industry expert said.

He also said it could be possible that the government´s best laid plans were being sabotaged. “If the government is unable to provide these houses before the next general election, they will loose approximately 200,000 votes.

According to experts such as Prof. Rangika Halwatura of the University of Moratuwa Civil Engineering Department who recently won the coveted ‘Young Scientist of the Year Award’ from The World Academy of Sciences (TWAS), it is time to look at innovative, low cost and highly durable material that could be easily replaced or substituted for the costly and un-sustainable materials like timber, burnt clay bricks and burnt clay tiles specified in the RFP.

Thew use of moda gadol (unbaked bricks) or sun-dried clay bricks and alternative roofing is not a new concept in Sri Lanka. According to Prof. B. D Nandadeva of the University of Kelaniya, earthen buildings were the only construction technology available to common people, with brick and mortar building methods confined only to building temples and royal structures until the advent of the British.

Moda gadol continues to be used widely in many remote parts of Sri Lanka.

The innovation that Prof. Halwatura and his PhD student, architect Chameera Udawattha, proposes is to change the composition of moda gadol, to one of soil and cement, with soil replacing the aggregates (chips) and sand, that is used in sun-dried cement concrete blocks, that are widely used in the construction industry.

Their innovation, the mud concrete block (MCB), tested and peer-reviewed, has now been proven to be having the lowest embedded energy or the lowest carbon footprint, in addition to having the lowest cost, and the second best thermal insulator of material commonly used in Sri Lanka for erecting walls.

In the composition of MCB, sand and metal components of concrete are replaced by fine and coarse aggregates of soil. The precise gravel and sand combination governs the strength of the MCB. Cement in this soil concrete is used as a stabilizer in very low quantities.

Writing in the prestigious, peer-reviewed construction industry journal, Energy and Buildings, Udawattha and Halwatura said “Comparatively, the mud concrete block walls have the lowest embedded energy content.”

However, the paper cautioned, “even though the brick had the highest energy content, the brick production process consumes more renewable energy than other two building materials. Therefore, the brick manufacturing process is more environmental friendly than manufacturing cement blocks.”

According to the paper, the significance of mud concrete block production is that the production process does not use any machinery or equipment. “The mould used to build MCB is a simple wooden or steel structure. The manufacturing process does not consume energy for drying, burning or mixing. The the energy used to manufacture is human energy and they are sustainable to some extent.”

Walling material

“One of the crucial findings of this study is re-usability of walling material. The embedded energy and the initial cost justifies the suitability of the wall. However, if they are not strong enough for reuse, it cannot stand the test of environmental sustainability. Only for walling materials, brick mud concrete blocks can be reused repeatedly.

The mud concrete block is 92% reusable. Its components can be crushed and produced same walling material with an addition of cement ratio of 8%.

In another study, published in the journal Advances in Building Energy Research, Udawattha and Halwatura stated that MCB is the second thermally favourable walling material alternative to the brick, while being almost one third of the cost.

“The results show that the thermal performance of a burnt brick wall of 0.150-m thickness can be equally achieved by employing an MCB wall thickness of 0.143 m and the hollow Concrete Block wall thickness of 0.21 mm.”

While Prof Halwathura´s research and practical application – homes and buildings using the material have been erected both in the north and east and in Rambukkana in the Kegalle district, covers the erection of the walls, a previous study conducted by engineers C. Jayasinghe, M.H.P.J. De. Silva, D.M.M.P. Dissanayake and C.T.K.I. Fernando and published in the Engineer journal of the Institution of Engineers, Sri Lanka, indicates that another local material, micro concrete roofing (MCR) tiles, can replace the more expensive and heavier calicut roofing tile specified in the RFP.

“The total cost of MCR roof with the timber framework is evaluated at Rs. 852 per square meter whereas it costs Rs. 814 per square meter for Cement fibre sheets and Rs. 1006/m2 for Calicut tiles,” their study, published in 2006 said. According to industry experts, these price ratios remain unchanged.

“In addition to the manufacturing and construction cost, there is an environmental cost associated with all building materials. This maybe in the form of over exploitation of natural resources and environmental problems associated with the production process.If there is a high demand for any material, the cost to the environment will also go up. In order to ease the burden on conventional materials due to high demand, there is a timely need to investigate the performance of alternative roofing materials,” their study further said.

Micro Concrete Roofing (MCR) tiles could be manufactured with a chip concrete mix. The raw materials used to manufacture these tiles are cement, quarry dust, and chips. Quarry dust and chips are by-products of the metal crushing industry. “The strength and durability testing have revealed satisfactory results which help engineers and architects to recommend this tile with much confidence,” the study said.

According to industry experts, there are other materials, also having good thermal insulation, durable and “culturally acceptable” at competitive prices. “For example, polyester roofing, sandwiched between two zinc/aluminium sheets provided the best thermal qualities, they are much lighter and therefore much easier to erect and can be supported on a light-steel roofing structure. These roofs are widely used in the North and the East.The Civil Engineering Department building of the University of Jaffna is an example in this connection,” sources said.

Local manufacturers are now producing these sandwiched roofing sheets at globally competitive prices. Another material, again locally produced, that can be easily substituted for the timber doors and windows is either uPVC or zinc aluminium windows or doors. 

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