Fabric molds could bring material-saving concrete beams within reach

A team of MIT engineers has discovered that fabric molds can be used to create concrete beams that use significantly less material than traditional beams. This innovation could make concrete construction more environmentally friendly and accessible, especially in regions where advanced construction equipment is scarce. The researchers designed a 3-meter test beam using an automated pattern-making process to create fabric molds.

The resulting beam used about one-third as much concrete and half as much steel reinforcement compared to a conventional beam. Despite fabric deforming under the weight of wet concrete, the engineers found that computational pattern design could turn this flexibility into an advantage, producing optimized structural forms. Fabric molds are also inexpensive, lightweight, and fast to produce, allowing them to be easily transported to job sites.

The team also noted that using less concrete could significantly reduce the cement industry's carbon emissions, which account for roughly 8% of human-caused carbon emissions. The design process involved mapping a path for the steel reinforcement using graphic statics, followed by topology optimization to determine where concrete was needed and where it could be removed.

The resulting beam features a top section, narrow angled legs, and a thin bottom section for the steel reinforcement. The researchers used a moderately wet, sand-rich concrete mix and packed it into the fabric mold by hand, resulting in a beam that closely matched the design. The team built three molds with different numbers of fabric pieces and found that 56 pieces provided the best balance between local control and overall accuracy.