A Study on Biochar-Cementitious Composites Toward Carbon–Neutral Architecture

Concrete is currently the second most consumed material in the world, with it’s core ingredient–cement, emitting 900 kg of CO2 into the atmosphere with each ton produced. Carbon sequestering amendments can help tackle the negative impacts of the concrete construction sector. As the concrete construction industry along with the computational design tools and manufacturers evolve, they move towards new materially and structurally informed construction methods aiming at carbon neutral solutions. The research investigates the use of biochar (carbonised bio-waste) as an aggregate for sustainable cementitious composites. The literature on the topic suggests that the main limitation of biochar as a concrete amendment is the reduction in mechanical properties associated with an increase in biochar content. This chapter, however, approaches this as a design challenge for maximising carbon sequestration while reaching optimal structural performance. Based on the novel biochar-cementitious composites developed in IAAC (the Institute for Advanced Architecture of Catalonia), the work further investigates and defines new design principles for traditional building elements so that they can obtain a carbon–neutral or negative footprint. The programmability of the material mix, for instance, combined with additive manufacturing and computational design tools makes it possible to design and manufacture functionally graded architectural elements whose properties vary based on the mechanical or qualitative performance, among others. The research chapter uses three case studies and examines fabrication strategies as well as new techniques for material allocation and performance-driven design toward carbon-negative materially informed building elements. Following the properties and origins of biochar, a novel approach for building structures acting as “carbon sinks” is proposed.