CoRncrete

A bio-based construction material

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Abstract

CoRncrete is a corn starch based bio-material formed by mixing corn starch with water and sand, and heating the mix in a microwave or oven. This heating process results in the formation of a hardened material. A constant corn starch to sand proportion of 1:5 has been adopted in this study. The transformation of CoRncrete from a semi-solid to a hardened material is caused by modification of corn starch that occur through a ‘gelatinization’ process. Heating of corn starch in the presence of water results in the formation of a gel that binds with sand grains and hardens. The temperature at which gel formation or gelatinization in CoRncrete occurs, was studied by DSC (Differential Scanning Calorimetry). To understand the microstructure of CoRncrete, ESEM (Environmental Scanning Electron Microscope) tests were carried out. ESEM scans revealed the effect of water content, heating source and heating duration on the gelatinization process that affects the development of microstructure of CoRncrete. The physical properties of CoRncrete was studied by analysing consistency behaviour of fresh CoRncrete and compressive strength of hardened CoRncrete. It was found that the corn starch in fresh CoRncrete changes its phase from solid to plastic/liquid at a specific water content. This water content was determined by cone penetrometer and proctor tests. This change in phase of corn starch was observed at an optimum water content. At optimum water content, the maximum dry density of fresh CoRncrete and maximum density and strength of hardened CoRncrete is also achieved. The fresh CoRncrete was heated to form hardened CoRncrete with the compressive strength found to be comparable to that of red clay bricks. The factors influencing the strength of hardened CoRncrete such as water content, size of the sand particle and heating duration (in a microwave) has been studied and discussed. A strong positive correlation between density and strength of hardened CoRncrete has been observed. Degradation of CoRncrete was studied by immersing specimens in water. Specimens were degraded partially to fully within a day, raising durability issues. The sustainability of CoRncrete was studied by carrying out LCA (Life Cycle Assessment) and compared with LCA results of Portland cement concrete and fired clay brick. The analysis indicated that the CoRncrete has comparatively higher environmental impact. Finally, the limiting factors in application of a CoRncrete and their remedial measures have been discussed. This research work addresses CoRncrete as a potential precursor to a new class of construction materials which gain strength rapidly by heating at relatively low temperature (~100oC).