Abstract

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This paper reports the findings of an investigation into the admixture potential of bone ash (BA) with a focus on the setting time of ordinary Portland cement (OPC). Cow bones are agricultural waste and constitute a sizeable proportion of solid waste in many cities of the world. Heaps of cow bones constitute aesthetic problem to the environment, unnecessary occupation of space and exude unpleasant odour that pollutes the environment. Cow bones need to be properly disposed to check the nuisance they constitute to the society. In the ever increasing endeavours to convert waste to wealth, investigation into the potentials of converting cow bones to beneficial applications in concrete becomes relevant. Bone vis-à-vis cow bone is mainly composed of compounds of calcium. The presence of calcium compounds in bone as well as in cement warrants effects of bone ash on cement to be envisaged. Cow bones were air-dried and incinerated to ash. The resulting ash was sieved through 75µm sieve. Based on weight of cement, 0%, 0.1%, 0.15%, 0.25%, 0.5, 1.0, 1.5%, 2.0%, and 2.5% of the ash were separately mixed with OPC to produce cement-bone ash (CBA). The required quantity of water determined from consistency test was added to the CBA mixture and mixed thoroughly to obtain CBA paste. The CBA paste was tested for setting time. Results show that BA decreases the setting time of OPC; the higher the content of BA, the faster is the reduction in the setting time of OPC. Reaction mechanisms are articulated and developed to explain reasons for the decrease in the setting time of OPC due to the addition of BA. It is concluded that BA is an accelerator; hence BA is recommended for use as an accelerator in concrete.

Keywords: Admixture, Accelerator, Bone ash, Concrete, Economic disposal, Ordinary Portland cement, Properties, Safe disposal, Setting time, Solid waste