Recycling of Cashew Nut Shells Waste in Asphalt Concrete and Briquettes -

Recycling of Cashew Nut Shells Waste in Asphalt Concrete and Briquettes

                 The global cashew nut production worldwide has reached about 4 million tons in 2017. West Africa, with about one third of cashew raw nuts worldwide production, is the largest cashew nut production region. This cashew production generates large quantities of cashew nut shells (CNS) waste that must be disposed. This study aims to valorize CNS ashes in asphalt mixtures. Different proportions of ashes were added as partial replacements to the very fine sand element in the asphalt concrete. The physico-mechanical properties of the mixtures were tested using the Marshall test. The results show that CNS ashes can replace fine sand in asphalt concrete. The best characteristics of the asphalt concrete were obtained with a 15% ash composition.

This work aims at recycling ash from the pyrolysis of cashew hulls in asphalt concrete. It has been demonstrated that it is possible to effectively use such ashes, which are micrometric and nanoscale in size, as a partial substitute for very fine sand (diameter less than 80 μm) in asphalt concrete. Also, according to Ramos et al., the cement production industry generates a very large amount of environmental pollution. Consequently, the idea of partially replacing it with ashes is beneficial. Asphalt concrete is a building material whose behavior is difficult to predict. In order to design a bituminous mixture containing ash from residual materials, a series of tests was made. Asphalt concretes with ash contents ranging from 0 and 25% were manufactured and their performances evaluated by Marshall Tests. This allowed the testing of the samples’ physico-mechanical properties: packing factors, creep, stability or resistance to compression. The tests showed that an asphalt concrete containing ash should ideally have a maximum 15% ash content to be of acceptable quality (i.e., possess good stability and creep resistance). For all the percentages of the ash tested (0 to 25%), the acceptable thicknesses of the asphalt concretes were obtained. These values covered the range of the required standards of 60-63 mm. Similarly, the packing factors obtained were also within desired range, i.e., higher than 95%. It is essential to investigate the addition of organic ash in asphalt/bituminous mixtures. Nowadays, the incineration of organic and inorganic waste is the most commonly used waste disposal method in urban cities, but it generates large quantity of bottom ash that need to be recycled. The use of cashew ashes in asphalt concrete contributes to a reduction of the quantity of very fine sand and cement in asphalt concrete. Recycling cashew nut shells leads to reduced environmental pollution.

Reference:

Anagonou, A., Songmene, V., Godjo, T. and Kouam, J., 2020. Recycling of West african cashew nut shells waste in asphalt concrete: Impact on the physico-mechanical properties of asphalt concrete. International Journal of Advanced Research and Publications, 4(2), pp.96-106.