
NSF Org: |
CMMI Division of Civil, Mechanical, and Manufacturing Innovation |
Recipient: |
|
Initial Amendment Date: | March 15, 2018 |
Latest Amendment Date: | April 29, 2021 |
Award Number: | 1829101 |
Award Instrument: | Standard Grant |
Program Manager: |
Siddiq Qidwai
sqidwai@nsf.gov (703)292-2211 CMMI Division of Civil, Mechanical, and Manufacturing Innovation ENG Directorate for Engineering |
Start Date: | August 15, 2017 |
End Date: | July 31, 2022 (Estimated) |
Total Intended Award Amount: | $334,525.00 |
Total Awarded Amount to Date: | $358,525.00 |
Funds Obligated to Date: |
FY 2020 = $16,000.00 FY 2021 = $8,000.00 |
History of Investigator: |
|
Recipient Sponsored Research Office: |
633 CLARK ST EVANSTON IL US 60208-0001 (312)503-7955 |
Sponsor Congressional District: |
|
Primary Place of Performance: |
1801 Maple Avenue Evansville IL US 60201-3149 |
Primary Place of
Performance Congressional District: |
|
Unique Entity Identifier (UEI): |
|
Parent UEI: |
|
NSF Program(s): | Mechanics of Materials and Str |
Primary Program Source: |
01002021DB NSF RESEARCH & RELATED ACTIVIT 01002122DB NSF RESEARCH & RELATED ACTIVIT |
Program Reference Code(s): |
|
Program Element Code(s): |
|
Award Agency Code: | 4900 |
Fund Agency Code: | 4900 |
Assistance Listing Number(s): | 47.041 |
ABSTRACT
This award supports fundamental research to provide new knowledge that paves the way for a systematic design of advanced geopolymer composites. Geopolymer composites are a new class of amorphous polymeric hybrids with attractive attributes that have the potential to drastically change the way composites materials are synthesized. Geopolymer-based hybrids are relevant to a vast array of fields such as civil, aerospace, mechanical, and biomedical engineering. However, established relationships between performance, chemistry, and composition are lacking. As a consequence, the widespread application of geopolymer-based materials has been impeded, despite their high potential. The integration of cutting-edge experiments with advanced computational modeling will accelerate the discovery of high-performance multifunctional structural composites. Geopolymer composites have been theorized for many interdisciplinary applications including enhanced-performance construction materials, passive cooling systems for buildings, biomaterials for bone repair, membranes for clean energy generation, and sound insulation systems. Therefore, results from this research will benefit the U. S. economy and society, and spur materials discovery. This research involves the collaboration between three institutions and across disciplines including nanoscience, solid mechanics, and materials science. Comprehensive outreach activities will be implemented in collaboration with local high schools to contribute to raising the next generation of materials scientists. Therefore, the multi-disciplinary approach will help broaden participation of underrepresented groups in research and positively impact engineering education.
Geopolymers are amorphous inorganic polymers that result from the reaction between an aluminosilicate source and an alkali metal hydroxide or silicate solution. Despite a wealth of studies, the origin of the strength of geopolymer composites is not fully understood. This research is to fill the knowledge gap by connecting the effective response to the micro- and nano- constituents based on continuum and computational micromechanics integrated with nanoscale mechanical characterization methods. The research team will formulate a theoretical micromechanics model to predict the macroscopic constitutive behavior, articulate new variational solutions using the modified secant approach within nonlinear homogenization theory, build a periodic microfield finite element model that accounts for multiaxial loading cases as well as morphological features, test the hypothesis that nano-porosity is the driving factor controlling the macroscopic mechanical response, validate the theoretical models by carrying out nano- and macro-scale mechanical tests on microsphere-reinforced potassium-based geopolymer composites, and establish correlations between nano- and micro-scale characteristics and the macroscopic behavior.
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.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
Note:
When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external
site maintained by the publisher. Some full text articles may not yet be available without a
charge during the embargo (administrative interval).
Some links on this page may take you to non-federal websites. Their policies may differ from
this site.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Overview
Geopolymers are a class of inorganic polymeric and X-ray amorphous materials that consist of alumina, silica, and alkali metal oxides. Geopolymers exhibit many appealing properties such as low carbon dioxide footprint, early strength development, and high strength-to-weight ratio. Due to these attractive attributes, geopolymer hybrids have been applied as green alternatives to concrete, as fire-resistant structural elements, and as affordable housing construction materials. A deeper emphasis on multi-scale predictive tools is a widely recognized need to advance the science and technology of geopolymer composites and promote the large-scale application and acceptance of geopolymer materials.
Therefore, our research objectives are: (i) to formulate a rigorous quantitative and multi-scale model that connects the intrinsic properties at the elemental scale to the behavior observed at the macroscopic level, (ii) to understand the influence of carbon-based nanomaterials on the physical and mechanical properties of geopolymer nanocomposites, and (iii) to understand the influence of raw materials on the behavior of rock-based geopolymer composites.
Intellectual Merit:
We formulated a multiscale physics-based mechanistic model to describe the strength behavior of geopolymer composites. Geopolymer composites were found to exhibit a pressure-dependent granular behavior, with the porosity being subdivided into nanoporosity and microporosity. Our results indicated that the nanoporosity is solely influenced by the chemistry and is not influenced by the processing and the presence of reinforcement. The nanogranular structure and the chemical composition at the nanometer scale have a profound influence on the effective mechanical response.
We formulated advanced synthesis protocols for metakaolin-based geopolymers reinforced with carbon nanofibers (CNFs) and multiwalled carbon nanotubes (MWCNTs). We found that CNFs lead to a densification of the microstructure, and we noted an increase in indentation modulus and in indentation hardness. A similar inner strengthening effect was also observed with MWCNTs as MWCNTs reduced the microporosity, resulting in an increase in the indentation modulus and hardness for the dominant microphase. We found that CNFs enhance the fracture toughness and the fracture energy. Similarly, MWCNTs increased the fracture toughness. For CNFs, we observed crack-bridging mechanisms in geopolymer nanocomposites. For MWCNTs, MWCNTs acted as bridges for fracture surfaces and connections for pores. Therefore, carbon-based nanomaterials such as CNFs and MWCNTs promote the geopolymerization reaction, strengthen the geopolymer skeleton, affect the pore structure, and improve mechanical characteristics.
We investigated the behavior of rock-based geopolymers synthesized using feldspathic rocks. We found that the geopolymerization products involve two phases: polysialate geopolymer and sodium aluminosilicate hydrates (N-A-S-H). When used as raw materials, feldspathic rock serve as both catalysts and fillers in geopolymer composites resulting in advanced materials with enhanced strength and fracture response.
Broader Impacts:
The research yielded advanced designs and protocols for the synthesis of enhanced performance geopolymer composites and cement nanocomposites: our protocols were archived in four patent applications and ten scientific articles in high-impact scientific research journals. The research funds supported two female PhD students of color (Jiaxin Chen and Yunzhi Xu) who graduated in 2021 and 2023. The project also supported five undergraduate students (Herbert Elyse, Raymonde Council, Mairi Glynn, Junior Ndayikengurukiye, and Nadiah Zamri), including four female students and three African American students, in advanced materials design and materials nanoscience. The project has fostered an international collaboration between the PI, the Local Materials Promotion Authority in Cameroon, and the University of Modena and Reggio Emilia in Italy. In 2017, we participated in the University of Illinois I-STEM summer program reaching out to 30 high-school students attended. In 2018, organized a hands-on high school science workshop for 30 10th grade students from the Chicago Bulls College Prep at Northwestern University (NU), on “Waves and Nanomechanics”. Moreover, there were two podcasts with the National Nanotechnology Institute and several high-profile lectures with The Royal Society (2020 and 2021), Gordon Research Conference (2022), and at the US-Africa first NAE Frontiers of Science, Engineering, and Medicine Symposium (2022).
Last Modified: 11/17/2023
Modified by: Ange-Therese Akono
Please report errors in award information by writing to: awardsearch@nsf.gov.