Brazilian students input integral to tropical road research
The PhD study is led by researcher Anthony Smith from Leeds Beckett’s School of the Built Environment & Engineering.
The Civil Engineering students Marina Prudente Guiotti, Mateus Farina, Leonardo Silva Júlio Rodrigues and Flavia Tamietti Temponi de Sa are part of Science without Borders (SwB), a Brazilian Government scholarship programme which aims to send 101,000 Brazilian university undergraduates and postgraduates to study in science, technology, engineering, maths and creative industries at top universities around the world.
The students were tasked over a number of weeks with testing soil shipped to Leeds Beckett from Malawi; using Anthony’s novel method which he hopes could solve various issues that tropical countries face during their wet season.
As Anthony explained: “Rural earth roads are constructed from the in-situ top soil, which means during the wet season – which can last for several months - the roads become inundated with rain water. This makes the soil material prone to tyre damage when used by vehicles, causing the roads to become impassable, isolating villagers for long periods of time.
“After some initial research I discovered Microbially Induced Calcite Precipitation (MICP) – a naturally occurring process where soil microbes consume urea and water to produce carbonate ions. These ions form an ionic bond with calcium ions present in the soil, creating calcite crystals. These crystals will cement soil particles together, and in doing so they strengthen the soil’s resistance to damage caused by passing vehicles. In addition, the crystals prevent the rain water from percolating down into the soil material, increasing the road’s ability to shed water and reducing the chances of the road becoming waterlogged in the first place.”
Anthony explained that he hopes his research will provide a low-impact, sustainable solution for the tropics, while the input and work by the SwB students has been vital to both the progression and quality of his research.
Student Marina, from São José do Rio Preto, said: “We were responsible for testing the characteristics of soils, before and after the introduction of a certain type of bacteria. This bacterium was put into the soil samples in order to prove if the MICP method of soil stabilisation that they deliver can be used to improve the properties of this material, which is used in the construction of earth roads.”
Mateus, from Recife in the state of Pernambuco, said of the dry density testing process: “After a sample is prepared and compacted into a mould with a specific volume, the test can be performed by removing a small amount of soil and placing it in the oven for a time. Once removed from the oven we would compare what the soil moisture was before and after the maximum density was achieved. All results were then transferred to form a table in order to be analysed.”
Flavia, from Universidade Federal de Minas Gerais added: “This research was interesting for me because not only is it a serious project that can help to improve quality of life in many villages, but it involved geotechnics, which is the area I intend to specialise in after university.
“During the project I was in charge of two experiments; the first one was the permeability test, to find the permeability of untreated and treated soil, under different conditions; and a California Bearing Ratio test that evaluates the resistance of soil to penetration, which is an indication of its bearing load capacity. My work included the preparation of the samples, the performance of the test and the respective laboratory reports.”
Leonardo from Brazil’s capital, Brasília, added: “Although it sounds simple, we had a lot of work to do, we had to test the soil samples in almost 10 different moisture contents on both treated and untreated samples, and each test could last up to 20 minutes. The tests that I was responsible for performing had a great part in the research, and I was able to gather some conclusions regarding the efficiency of the use of the bacteria in soils. The results helped to show that the use of the bacteria in this kind of soil might be efficient and viable.”
Photo from (L-R) Mateus Farina, Marina Prudente Guiotti, Leonardo Silva Júlio Rodrigues and Anthony Smith in the Leeds Beckett University lab where the soil research is carried out.