A Carbon Negative Self-Healing Enzymatic Construction Material

Worcester Polytechnic Institute, Worcester MA

Investigators

Abstract

Second only to water, concrete is the most consumed material on earth. Every year, waste concrete from construction and carbon dioxide excretion from cement production and transport is increasing, and concrete alone now contributes to 9 percent of the overall CO2 emissions. Additionally, concrete is inherently brittle, and it requires frequent repair and replacement, which are economically expensive and further generate large volumes of carbon dioxide. Scientists have been trying to find environmentally friendly and low-cost substitutes for concrete for decades. The goal of this award is to create a new class of inexpensive, carbon-negative, self-healing construction materials using a combined modeling and experimental framework. The material utilizes a safe, ubiquitous, biological enzyme that can efficiently capture CO2 during its production. Using this new paradigm, a self-healing Enzymatic Construction Material will be produced. This Enzymatic Construction Material can significantly lengthen the service life of civil infrastructure while capturing carbon. It is predicted that one cubic yard of Enzymatic Construction Material will approximately store 18 pounds of CO2. In contrast, one cubic yard of concrete emits around 400 pounds of CO2. The research tasks will be complemented by training both graduate and undergraduate students and developing a program to help inspire underprivileged girls to learn about construction and engineering. Inspired by the efficient process of CO2 transport in cells by enzymes, a new paradigm is introduced to create the Enzymatic Construction Material with self-healing properties. The enzyme, carbonic anhydrase, catalyzes calcium carbonate crystal precipitation, establishing mineral bridges along the polymer scaffolding that bonds the aggregate together. Hence, curing of the material can be performed at low temperatures in a short timeframe. The material exhibits an average strength value that is three times as high as the minimum requirement for cement mortar and is also capable of sustaining many cycles of healing after fracture. The scientific contribution of the project includes the following. (1) The formulation of a new class of construction materials through enzymatic crystal precipitation. The rate of crystal precipitation through the enzymatic mechanism is four orders of magnitude faster than bacterial methods making it scalable to industrial applications. (2) The enzymatic mechanism provides a means for the development of carbon-negative materials to ultimately replace concrete. (3) A novel fluctuation-based Semi-Grand Canonical Monte Carlo simulation method will be used as a modeling technique for the thermodynamic behavior of the Enzymatic Construction Material. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.