Final Report: Cement-Polymer Composites From Recycled Polymers for ConstructionEPA Contract Number: EPD04041
Title: Cement-Polymer Composites From Recycled Polymers for Construction
Investigators: Loutfy, Raouf O.
Small Business: MER Corporation
EPA Contact: Richards, April
Project Period: March 1, 2004 through August 31, 2004
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2004) RFA Text | Recipients Lists
Research Category: SBIR - Waste , Hazardous Waste/Remediation , Small Business Innovation Research (SBIR)
Conventional cement-based construction materials such as stucco and concrete are prone to cracking with poor thermal insulation and are very permeable to water. Repair of deteriorated cement and stucco-based structures is a major problem. It is estimated that repair costs in the United States are more than $100 billion. Therefore, there is a need to improve certain properties of stucco and cement concrete. In this regard, there have been some attempts to improve the properties of these materials to a certain extent by coating with polymers or adding certain polymers to the cement bases. In most of the improvements, the polymer acts as a physical bonding agent or as filler material. Despite the improvement to some properties, the coating forms an impermeable barrier for the trapped moisture, causing serious problems and damage to the structure. The goal of this research project was to develop and evaluate a high-performance and low-cost cement-polymer composite for the construction industry. The specific goal was to improve various properties of commercially available stucco.
To achieve these goals, Materials and Electrochemical Research Corporation (MER) first developed modified elastomers from recycled rubber tires (crumb rubber). Very inexpensive crumb rubber is obtained from the retreading industry as a byproduct of automobile tire waste. Several surface modifications of the crumb rubber were conducted to obtain the most simple and economic process. Based on several experiments, proprietary chemical and catalytic processes were developed for modifying the surface of crumb rubber. It was discovered that 20 percent crumb rubber (by volume) can be incorporated in commercial stucco without any significant effect on the color and appearance of the resulting stucco-crumb rubber composite. Therefore, treated and functionalized crumb rubber was incorporated in commercially available stucco (20:80 ratio by volume) and various samples were made and tested in accordance with American Society for Testing and Materials standards.
By incorporating MER’s best treated crumb rubber in stucco, the compressive strength was 53 percent better than commercial stucco, and 209 percent better than untreated crumb rubber-stucco under otherwise similar conditions. Similarly, flexural strength of the treated crumb rubber-stucco composite was 26 percent better than that of pure stucco, and 95 percent better than untreated crumb rubber-stucco. Based on freeze and thaw experiments, the cracking property of MER’s treated crumb rubber-stucco composite is found to be 93 percent better than commercially available stucco. Dispersion and particle size of crumb rubber in stucco plays an important role, providing better strengths with higher dispersion. The incorporation of crumb rubber in stucco also decreased the overall density of the resulting crumb rubber-stucco composite, making it a lighter construction material. Incorporating only “untreated” crumb rubber into stucco, however, resulted in a decrease in the density, and in the compressive and flexural strengths of the stucco. Phase I results indicate a remarkable improvement in desirable properties of commercially available stucco by incorporating MER’s treated crumb rubber in stucco in a very inexpensive process.
All of the Phase I goals of this research project have been successfully met, and a simple, low-cost process capable of significantly improving desirable properties of stucco has been developed. This multiuse technology, with a few modifications, can easily be applied to numerous other applications such as concrete building structures, roads, and pavements.