A multi-criteria study on rammed earth for low carbon buildings using a novel ANP-GA approach

Nowadays, the growth of energy consumption in buildings is an important topic. Rammed earth (RE) structures have attracted the attention of engineers and contractors in recent years due to their advantages such as sustainability, availability and low embodied energy content. These advantages result in less energy consumption in the life cycle of the RE structures. However, there is a lack of research on the mixture composition of RE materials containing admixtures. This research introduced integrated analytic network process (ANP) and genetic algorithm (GA) methodology to select the optimum mixture of RE material containing cement, expanded polystyrene(EPS), and phase change materials(PCM) with different moisture content. The five criteria for evaluations were cost, building weight, carbon footprint, mechanical strength and thermal performance. Thermal and mechanical experiments were performed on the different mixtures of RE. Based on the results of the ANP-GA approach, a RE mixture with mass ratios of 78% soil, 12% moisture, and 10% cement was found to be the most suitable RE mixture. ANP-GA eliminated EPS and PCM due to the low strength of EPS-RE and the high cost of PCM; however, they made RE perform well in thermal characteristic. This proposed the model can be used to select the ideal mixture of other engineering materials.