Arooz

Rizna hails from Hambantota. She completed her secondary education at Southlands College, Galle. She then entered the Faculty of Architecture at the University of Moratuwa(UoM) and completed Bachelor of Architecture with first class honours in 2012. She joined the industry and worked for 3 years before returning to UoM’s Civil Engineering Department to take up her next challenge, i.e. to pursue a PhD.

Rizna says her interest was to look at earth-based, organic construction material that has low impact on the environment. Taking a look at material that is freely available, soil caught her eye. She said, “during this time a research group at the Department of Civil Engineering was investigating a mud-concrete block, and this influenced my thinking towards the same material”. The challenge for Rizna was to come up with a technology that would make it possible to build a load bearing wall without reinforcements with these material. According to Rizna, there are two common methods currently used for developing structural strength in walls. One is reinforcement with metal, and the other is compression of the material to achieve a thickness that increases with height. Both these methods are expensive. So, Rizna set out to find an optimal mix of self-compacting mud that could be stabilized with low quantities of concrete.

The material used in her mix, mud, is easy to find, consumes little energy, saves labor costs and because of its ubiquity, incurs minimal transportation cost. Rizna also designed a formwork which could be used to pour the mud-concrete mix to help build the wall. This formwork is reusable, which helps reduce the cost of constructing her load bearing wall.

Tests using computer simulations, load calculations and a questionnaire survey determined that a wall segment built using mud-concrete is strongest at a height of 4 feet. Rizna's findings show that, up to 3 stories can be built using these load bearing wall segments, Further tests were conducted at the labs in the Department of Civil Engineering to identify the best curing period and to check the durability of the wall.

Results illustrated the best curing period for this particular mix as 14 days. Experiments were carried out to test erosion by shooting water at a 90-degree angle at the wall. These showed that the wall could withstand the forces of heavy rain. Rizna acknowledges however, that the structure has to be tested over the next few years to determine how it would withstand erosion brought on by time. “The wall is not easily vulnerable to moss and mole”, she said, “but with methods such as plastering and proper eaves designed for roofs, we could stop the dampening of the wall to improve durability further”.

Rizna is happy that she chose to do a PhD at UoM. “While I had reservations because I am from an architectural background, I was able to put them to rest because of the encouragement given by my supervisor”. She is thankful for the grant she received for her research from the National Science Foundation through her supervisor. She has presented her work at conferences in Hong Kong and Singapore and is appreciative of the grant received for travel from the Royal Society in the UK. 

Rangika Halwathura is a Professor of Civil Engineering. He has completed both Bachelors and PhD degrees at the UoM. He is known as an ardent researcher and is the recipient of a  number of awards.

Rizna and Rangika obtained patents and won a presidential award for their mud-concrete mix design and the formwork. They are both hopeful that this technology will be widely accepted in Sri Lanka, and has entrusted the Ministry of Housing with this technology. They have also trained people with UN Habitat to build a community center for war victims in Batticaloa.

Rizna says, “This technology could accommodate mass economical construction, but I don’t necessary want this technology to be only known as one for the poor. I want people to recognize this technology for the benefits it provides, such as the thermal performance, structural performance, reduction in life cycle costing and minimal embodied energy consumption”. She claims that the cost for building a square foot of load bearing wall with six-inches of thickness and plastering it will cost about 60 Sri Lankan Rupees. According to our researcher this is a saving of about 30-40% when compared to building a brick wall with the same dimensions.

Rizna is continuing her research with the Department of Civil Engineering. She is also working on popularizing this technology. We hope that she will reach her goal soon, and wish her all the best for a bright career.