Grantee Research Project Results
Final Report: Development of New Concrete-Based Wastewater Infrastructure Systems With Enhanced Durability, Structural Efficiency, and Hydrological Performance
EPA Contract Number: 68D02097Title: Development of New Concrete-Based Wastewater Infrastructure Systems With Enhanced Durability, Structural Efficiency, and Hydrological Performance
Investigators: Chowdhury, Habibur
Small Business: Technova Corporation
EPA Contact: Richards, April
Phase: I
Project Period: October 1, 2002 through July 31, 2003
Project Amount: $99,974
RFA: Small Business Innovation Research (SBIR) - Phase I (2002) RFA Text | Recipients Lists
Research Category: Watersheds , SBIR - Water and Wastewater , Small Business Innovation Research (SBIR)
Description:
Concrete components (pipes, manholes, etc.) represent close to one-half of the investment in sewer infrastructure. In recent years, incidents of severe damage to concrete-based sanitary sewer systems have increased significantly. Microbial-induced corrosion has been identified as the primary cause of this growing problem. New environmental regulations have led to a significant rise in microbial activity within wastewater systems. Sulfuric acid is generated by a sequence of microbial ecosystems in sanitary sewers, which attacks concrete and undermines its longevity. Recent research has provided substantial insight into this mode of concrete deterioration; this information, complemented with a fundamental view of the material science of concrete, provides a solid basis to develop effective solutions to the problem. Traditional structural designs relying solely on corrosion-prone steel reinforcement further undermine the efficiency and durability of concrete-based sewer infrastructures. Recent advances in synthetic fiber reinforcement offer the potential to substantially enhance the structural efficiency of concrete-based sewer systems. Technova Corporation, in cooperation with the concrete pipe industry and Michigan State University, has undertaken a comprehensive approach towards the development of a new generation of concrete-based sewer infrastructure systems with significantly enhanced corrosion resistance and structural efficiency.
Summary/Accomplishments (Outputs/Outcomes):
Control of microbial-induced corrosion is accomplished through a multi-faceted approach that mitigates the chemical, physical, and microbial damage phenomena through refinement of the concrete pore structure, transport attributes, chemistry, and amenability to microbial growth. High-modulus synthetic fibers also are employed towards the design of more efficient concrete pipes of reduced steel ratio with improved protection of steel, streamlined geometry, and enhanced structural performance. Laboratory and field investigations of concrete materials were complemented in Phase I research with industrial production and large-scale structural evaluation of concrete pipes embodying new fiber reinforcement systems and structural designs. The research outcomes have validated the technical value and commercial promise of selected strategies involving refinement of the concrete capillary pores, emphasizing their size distribution, interconnectivity and surface characteristics, modification of the chemistry of cement hydration products, enhancement of the fracture toughness and tensile strength of concrete, and development of concrete pipe structural designs that optimally utilize these improvements in material performance attributes. Implementation of these strategies in production facilities involves simple use of new additives with practically no alteration of production process and facilities. Major gains in longevity and life cycle economy of concrete-based sewer infrastructure systems could be realized through optimum combination, full verification, and industrial implementation of these complementary strategies.
Conclusions:
Technically and commercially viable strategies were developed for enhancement of the longevity, life cycle economy, structural efficiency, and workability of the concrete-based sewer infrastructure systems. Three major activities were undertaken in the project: (1) development of effective and commercially viable means of improving concrete resistance to microbial-induced corrosion in sanitary sewer environment; (2) enhancement of the structural efficiency, durability, and workability of concrete pipes through fiber reinforcement; and (3) development of commercialization plans and industrial coalitions towards market introduction of the technology. The project achievements in these three areas are presented in the paragraphs that follow.
Development of Commercially Viable Concrete Materials With Enhanced Resistance to Microbial-Induced Corrosion. Diverse strategies were evaluated for the enhancement of concrete resistance to microbial-induced corrosion through refinement of concrete chemistry, pore structure, transport attributes, and amenability to microbial growth. Comprehensive laboratory and field experiments were implemented to screen different strategies based on their impact on mechanical, physical, and durability characteristics of concrete as well as its susceptibility to microbial-induced corrosion. Given the constraints of production processes and facilities, the approach emphasized development of a new concrete admixture formulation in lieu of altering major constituents of concrete (i.e., cement and aggregates). The following ingredients emerged as effective means (with complementary effects) of a new admixture formulation for the enhancement of concrete resistance to microbial-induced corrosion: (1) hydrophobic additives rendering the surfaces of capillary pores water-repelling and thus enhancing the barrier qualities of concrete; (2) blends of fine and coarse pozzolans to refine the chemistry and pore system characteristics (fineness and interconnectivity) of concrete, thereby enhancing the chemical (acid) resistance and barrier attributes of concrete; and (3) polymer emulsions for the refinement of concrete porosity (interconnectivity), affinity for moisture, and amenability to microbial growth. Antimicrobial constituents also were considered for reducing the amenability of concrete to microbial growth; however, their high cost lowers their competitive position. The results indicate that an admixture formulation comprising optimum blends of hydrophobic, fine pozzolan, and coarse pozzolan constituents offers the best promise to achieve substantially enhanced resistance to microbial-induced corrosion and life cycle economy of the concrete-based sanitary sewer infrastructure, with only minor initial cost implications. Replacement of the hydrophobic constituent with polymer emulsion also is an option, with somewhat less favorable initial cost implications. These additives would effectively enhance all key aspects of concrete performance that impact its resistance to microbial-induced corrosion, including chemistry of cement hydration products, size distribution, interconnectivity and surface characteristics of capillary pores, affinity to moisture, and amenability to microbial growth. An optimum admixture formulation based on these complementary strategies is expected to offer an effective and commercially viable solution to the growing problems associated with microbial-induced corrosion of concrete in sanitary sewer environments.
Enhancement of the Structural Efficiency, Durability, and Workability of Concrete Pipes Through Fiber Reinforcement. The load-bearing capacity of concrete pipes strongly relies on steel reinforcement of concrete. Steel, however, is highly susceptible to corrosion, and concrete-based sanitary sewer infrastructure systems are considered to reach the end of their service life once the depth of microbial-induced corrosion reaches the level of steel reinforcement. The service life of concrete-based sanitary sewer infrastructure systems thus would increase proportionally with increasing thickness of protective concrete cover. Reinforcement of concrete with corrosion-resistant synthetic fibers offers the potential to enhance the fracture toughness and tensile strength of concrete and thus allow reduction of the steel reinforcement ratio (and increase of the protective concrete cover thickness). Comprehensive material studies complemented with industrial-scale production and evaluation efforts were undertaken to identify fiber reinforcement conditions that offer technically effective and economically viable means towards achieving this objective. Emphasis was placed on high-modulus fibers that are particularly effective in enhancement of the mechanical properties of concrete. Polyvinyl alcohol (PVA), carbon, and aramid and alkali-resistant glass fibers were considered in this investigation at volume fractions ranging from 0.2 percent to 1 percent. Flexural, shear, impact, and durability tests were performed with concrete pipe mix proportions to evaluate the competitive position of different fiber types and dosages. PVA fibers at approximately 1 percent volume fraction proved to be highly effective in enhancement of the mechanical attributes of concrete, with desirable durability characteristics in the alkaline environment of concrete; the relatively low cost of PVA fibers is another advantage favoring their choice for use in concrete-based sewer infrastructure systems.
The gains in shear resistance of concrete with PVA fiber reinforcement further allows elimination of the enlarged end segment of concrete pipes that complicates their handling, storage, and installation. In light of the gains in concrete mechanical performance with introduction of PVA fibers, new structural designs were developed for concrete pipes with reduced amount of conventional steel reinforcement and increased protective concrete cover thickness. Full-scale pipes embodying these new design principles (with PVA fibers) were produced in an industrial production facility in mid-Michigan, and were subjected to full-scale structural (flexural and joint shear) tests. The results confirmed the viability of Technova Corporation’s approach to develop more efficient and streamlined concrete pipe designs through complementary use of synthetic fibers and conventional steel reinforcement. These new pipe designs complement enhanced levels of structural efficiency with improved durability (under microbial-induced corrosion) and workability (ease of handling, storage, and installation). Industrial-scale production and experimental evaluation of full-scale concrete pipes proved to be a major step towards verification of the technical promise and commercial viability of this approach.
Development of Commercialization Plans and Industrial Coalitions Towards Market Introduction of the Technology. Enhancement of concrete resistance to microbial-induced corrosion is a serious industrial need with growing commercial implications. The industry is, therefore, strongly supportive of the project, and has made major contributions and commitments towards implementation of the research effort. Economic analyses were conducted during the project, which suggested viability of Technova Corporation's strategies in terms of their impact on initial and life cycle costs of concrete-based sanitary sewer infrastructure systems. Competitive performance and cost analyses were implemented versus competing technologies, which verified commercial viability of the approach. Steps were taken to secure the company’s proprietary position with respect to the new concrete admixture formulations and structural design strategies. Preliminary production, marketing, and financing plans were developed for transfer of the technology to targeted markets. Major steps were taken to solidify the industrial relationships needed to implement the production, marketing, and financing plans.
Supplemental Keywords:
sewer infrastructure, concrete, sanitary sewer systems, microbial-induced corrosion, wastewater systems, sulfuric acid, steel, corrosion resistance, pozzolan, polyvinyl alcohol, PVA, fiber, life-cycle economy, structural efficiency, small business, SBIR;, Scientific Discipline, Water, Sustainable Industry/Business, Wastewater, cleaner production/pollution prevention, Chemistry and Materials Science, Environmental Engineering, concrete, cleaner production, environmentally conscious manufacturing, clean technology, wastewater pipeline, wastewater pipeline repair, concrete materials, recycled building material, phosphate based concrete, fiber reinforcement, construction material, pollution prevention, product designSBIR Phase II:
Development of New Wastewater Infrastructure Systems With Enhanced Durability and Structural Efficiency | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.