Grantee Research Project Results

Biostabilization of Rammed Earth for Reduction of Waste and CO2 Emissions

EPA Grant Number: SU835497
Title: Biostabilization of Rammed Earth for Reduction of Waste and CO2 Emissions
Investigators: Kraus, Chad , Roberts, Jennifer A , Hirmas, Daniel
Current Investigators: Kraus, Chad , Johnson, Anna , Roberts, Jennifer A , Bents, Alyson , Peek, Ben , Hirmas, Daniel , Versteeg, David , Boling, Joshua , Bents, Timothy , Dawson, Zachary
Institution: University of Kansas
EPA Project Officer: Packard, Benjamin H
Phase: I
Project Period: August 15, 2013 through August 14, 2014
Project Amount: $14,980
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2013) RFA Text |  Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Sustainable and Healthy Communities , P3 Challenge Area - Chemical Safety , P3 Awards , Sustainable and Healthy Communities

Objective:

Rammed earth (RE) possesses low embodied energy, high recyclability, and low toxicity while having little impact on biodiversity and virtually no depletion of biological nutrients. This inherent sustainability has been compromised by modifications imported from concrete construction in response to contemporary building standards, most notably, the addition of Portland cement as a soil stabilizer. Today, cement is the ubiquitous glue that holds our built environment together. While cement stabilized rammed earth (SRE) possesses less than half of the embodied energy of site cast concrete, it still remains less bad. The challenge is to stabilize contemporary rammed earth to meet the expectations of building codes without the use of Portland cement or other stabilizers such as lime and asphaltic emulsions. The proposed work aims to strengthen RE by a process known as microbially induced calcite precipitation. Natural soil microorganisms are known to biomineralize calcite in soil pore spaces, aggregating mineral grains and enhancing desirable properties of earthen materials; this process has been increasingly used in engineering applications (repairing existing concrete structures, stabilizing soils around foundations, etc.) over the past decade. Our goal is to significantly reduce the atmospheric CO₂ emissions and waste associated with the production and application of Portland cement by exploring microbial biomineralization to enhance the material properties of RE in what we are calling microbially indurated rammed earth (MIRE).

Approach:

The work of Phase 1 will be conducted in two parts and represents an interdisciplinary endeavor involving the Departments of Architecture, Geography, and Geology at the University of Kansas. During Phase 1a, students from the three departments on the P3 team will conduct controlled MIRE experiments guided by predictive models and amended with different concentrations of a common soil bacterium (Sporosarcina pasteurii) known to increase strength of construction materials through biomineralization of calcite. These samples will be analyzed for: particle-size, Atterberg Limits, Proctor Compaction, water retention curve determination, distribution and mineralogy of carbonate, pore-size distribution, and compressive and flexural strength. These findings will be compared against controls – unamended soils, Portland cement stabilized soils, and soils biostabilized with native microorganisms. In Phase 1b, the material testing will culminate in the design and construction of a small MIRE structure.

Expected Results:

We expect the results of the project will provide data illustrating MIRE as a sustainable alternative to cement stabilized rammed earth. We anticipate illustrating the significantly lower embodied energy and reduced pollution of MIRE compared to SRE and concrete construction. The MIRE structure will serve as a proof-of-concept as well as a public demonstration of biostabilization of earthen construction materials.

Supplemental Keywords:

biocementation, biomineralization, calcification, microbes, earthen architecture, compressed earth block, adobe, Kansas;

Progress and Final Reports:

Final Report