Final Report: Cement-Polymer Composites From Recycled Polymers for Construction ApplicationsEPA Contract Number: EPD05051
Title: Cement-Polymer Composites From Recycled Polymers for Construction Applications
Investigators: Loutfy, Raouf O.
Small Business: Materials and Electrochemical Research (MER) Corporation
EPA Contact: Manager, SBIR Program
Project Period: April 1, 2005 through June 30, 2006
Project Amount: $225,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2005) Recipients Lists
Research Category: SBIR - Waste , Hazardous Waste/Remediation , Small Business Innovation Research (SBIR)
Materials & Electrochemical Research (MER) Corporation developed modified elastomers derived from recycled rubber tires (crumb rubber) by surface modifying the rubber using super electrophiles to derive an addition reaction. Crumb rubber was treated with several different electrophiles and was successfully surface functionalized. Among various electrophiles investigated, the best functionalization of crumb rubber was obtained with organic acid in the presence of a nonprecious catalyst. Treated and thus functionalized crumb rubber was incorporated into a commercially available stucco mix; various test samples then were made and tested in accordance with American Society for Testing and Materials (ASTM) standards.
After incorporating MER’s best treated crumb rubber into stucco, the compressive strength was found to be higher than that of commercial stucco, and better than that of untreated crumb rubber stucco under similar conditions. Similarly, the flexural strength of treated crumb rubber stucco composite was found to be better than that of pure stucco and untreated crumb rubber stucco. Based on freeze and thaw experiments, the cracking resistance of MER’s treated crumb rubber stucco composite was found to be better than that of commercially available stucco. Incorporating crumb rubber into stucco also decreased the overall density, making it a lighter material while reducing thermal transmission. These results demonstrate that a remarkable improvement in desirable properties for commercially available stucco can be achieved by incorporating MER’s treated crumb rubber into stucco.
This research program demonstrated approximately an 86 percent increase of compressive strength for the stucco mixed with treated rubber compared with that of untreated rubber. Strength increased 45 percent for stucco using treated rubber additive compared to pumice alone (no rubber additive). The extraordinary improvement in flexural strength of the stucco using rubber treated with an additive was demonstrated and compared to the stucco using untreated rubber. The stucco using pumice or pumice plus untreated rubber has almost no flexural strength. It also was confirmed that stucco using pumice and treated rubber weighed less than pumice and untreated rubber.
MER is pleased to report that all the objectives of this Phase II project were successfully met, and a simple, low cost process capable of significantly improving the desirable properties of stucco has been developed. This multi-use cement technology, with minor modifications, can be applied easily to numerous other applications such as concrete building structures, roads, and pavements.
MER arranged for the Arizona State University (ASU) to act as a third-party evaluator to evaluate MER’s rubber material using ASU’s stucco-fabrication method. The test results obtained by ASU validated MER’s data and confirmed that surface functionalization of crumb rubber results in a significant increase in compressive strength and flexural strength. The results increased MER’s confidence in the suitability of developing this process for commercialization. It is interesting to note that the functionalization resulted not only in increased mechanical properties, but because of better bonding of the rubber to the cement, it also allowed increased loading of rubber in the stucco.
Based on the results achieved in this program, the following conclusions can be drawn:
- Simple, low-cost cement-rubber stucco was developed by producing a treated recycled rubber that is wettable, dispersible, and easy to mix homogenously with cement. This treated rubber adheres to the surrounding cementation material.
- Adding treated recycled rubber to the stucco consistently increases crack resistance, and decreases crack width of stucco in environmentally harsh conditions.
- The treated recycled rubber increases the compressive and flexural strength of cementitious materials, using optimum treatment loading and preparation conditions.
- The technical feasibility of using treated recycled rubber in concrete material has been established by demonstrating that functionalized rubber as an additive improves compressive and flexural strength as determined by MER and validated by ASU.
- The treatment process was scaled-up to produce 15 lb/day of product; commercialization effort is underway with three companies (including one local company in Tucson) to evaluate the developed product. Unfortunately, the evaluation is time consuming, and there are many stucco materials formulations, which vary among companies.
- Continued work with commercial companies in this field is recommended. In addition, more extensive field testing of MER’s treated recycled rubber incorporated into concrete control mixtures should be conducted to allow further optimization and improvement of the overall process.
- The excellent results obtained by incorporating MER’s treated recycled rubber into concrete stucco control mixtures should be extended and validated for structural concrete such as road pavement, road tile, etc.