Effect of Unburnt Rice Husk on the Properties of Concrete

Abstract

In the recent years, there have been considerable efforts all over the world to reuse by-products in order to sustainably conserve our environment. In this sense, rice husk is also an agricultural bi-product and its ash after being burnt has widely been used to replace Portland cement in the construction industry due to the fact that it is rich in pozzolanic content. However, no studies have been conducted to identify the definite temperatures to which rice husk can be heated to produce the perfect qualities required for enhancement of concrete. This prompted us to find out whether utilizing ground unburnt rice husk would as well be fit to be used in partial replacement of cement. This would save time and other resources used in heating rice husk to ash. This study evaluates how different contents of rice husk added to concrete may influence its workability, water absorption and compressive strength of concrete with 0, 1.5, 2.5, 5, 7.5 & 10% cement replacement at fixed water cement plus ground rice husk at 0.5. The results were compared to a controlled sample and the viability of adding ground rice husk to concrete was verified. For water absorption the results were negative as addition of ground un burnt rice husk resulted in increasing water absorption of concrete which is generally not good for its durability purposes. Values of workability varied with addition of ground un burnt rice husk but still within the allowable limits for concrete to be used on some construction works. Also, there was a break through on the compressive strength with 1.5% replacement of cement with ground un burnt rice husk achieving the target strength. Basing on this, we can therefore infer that cement can be reduced up to 15% with un burnt ground rice husk without compromising compressive strength requirements of concrete more especially in situations where water absorption is not very important.