Grantee Research Project Results
Final Report: An Alternative Concrete Chemistry with Significantly Enhanced Durability, Sustainability, Economy, Safety and Strength
EPA Contract Number: EPD17021Title: An Alternative Concrete Chemistry with Significantly Enhanced Durability, Sustainability, Economy, Safety and Strength
Investigators: Balachandra, Anagi
Small Business: Metna Co.
EPA Contact: Richards, April
Phase: II
Project Period: March 1, 2017 through February 28, 2019 (Extended to September 30, 2019)
Project Amount: $300,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2016) Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , SBIR - Building Materials
Description:
A new class of sustainable hydraulic cements was developed, which are distinguished by the primary aspect of their processing. These hydraulic cements offer significant advantages over conventional Portland cement in terms of carbon footprint, energy content, performance, cost, and safe use of industrial byproducts. The distinct approach to processing of these hydraulic cements allows for expanding their chemistry and selection of raw materials. Some hydration mechanisms considered included through-solution polycondensation of alkali aluminosilicates, and formation of more stable binders from the metastable phases of cement. The approach adopted for processing of hydraulic cements enables the use of diverse byproduct and natural primary raw materials. The byproducts considered were rich in aluminosilicates, and included metallurgical slags, biomass combustion ash, landfilled coal ash, mine tailings, and the brick constituent of construction & demolition wastes. Abundant aluminosilicate- and carbonate-rich natural materials were also evaluated, including limestone, clay, and igneous rocks (granite, etc.). Besides these primary raw materials, supplementary constituents were also used to enable activation of and compounding with the primary raw materials.
Summary/Accomplishments (Outputs/Outcomes):
It is possible to transform abundant industrial byproducts and natural raw materials into hydraulic cements without resorting to excessively high temperatures. These hydraulic cements have about 75% less carbon footprint and energy content, and their production cost is about half that of Portland cement. The weathering resistance and chemical stability of the new hydraulic cements magnify their sustainability and cost benefits when evaluated from a life-cycle point of view. The new hydraulic cements meet the performance-based requirements for general-used hydraulic cements. They also suit utilization as the primary constituent of blended cements. The approach to processing of the sustainable hydraulic cements developed in the project is scalable. These cements actually benefit from scale-up which improves their quality and rate of product. The new hydraulic cements are compatible with the procedures developed for design of Portland cement concrete mixtures. Concrete materials incorporating the new hydraulic cements can be produced using common industrial-scale methods of concrete production, and are compatible with the prevalent methods of concrete construction. The physical, mechanical, barrier and durability characteristics of concrete materials prepared with the new hydraulic cements match or surpass the corresponding properties of Portland cement concrete.
Conclusions:
- It is feasible to transform abundant byproduct and natural materials into hydraulic cements that meet standard requirements via input of mechanical energy in the presence of relatively small concentration of supplementary materials that complement their chemistry and/or facilitate their mechanical activation.
- The cement chemistries considered for processing via input of mechanical energy include alkali aluminosilicates and carbonates. Activation via disturbing the crystalline structures as well as chemical compounding under input of mechanical energy are the prevalent mechanisms in transformation of the blends of raw materials into hydraulic cements.
- Diverse raw materials suit transformation into hydraulic cement, in the presence of supplementary materials, via input of mechanical energy. The primary byproduct raw materials evaluated for this purpose include metallurgical slags, mine tailings, landfilled coal ash, and the brick constituent of construction & demolition waste. These industrial byproducts were used as aluminosilicate precursors (some of which also include alkali or alkaline earth metals). Some abundant natural raw materials used in the process included sedimentary rocks (limestone), clay, and different igneous rocks (e.g., granite). These natural materials were used either as sources of aluminosilicates (with or without alkali metals) or carbonates.
- Some supplementary materials used successfully in formulation of hydraulic cements for processing via input of mechanical energy included sodium carbonate, sodium sulfate, sodium hydroxide, potassium hydroxide, gypsum, lime, and quick lime.
- The mechanically processed hydraulic cements based on alkali aluminosilicate chemistry are effective in stabilizing any heavy metals constituent of the aluminosilicate-rich industrial byproducts used as primary raw materials in their processing.
- The mechanical approach to processing of hydraulic cements developed in this project is scalable, and actually benefits from scale-up that raises the intensity of mechanical energy input via impact. At any scale, measures that raise the intensity of mechanical energy input enhance the efficiency of the process and the end product quality.
- While our current state of understanding the transformation of raw materials into hydraulic cements via input of mechanical energy is not adequate for theoretical simulation of the process, the semi-empirical models developed in the project can guide further scale-up of the process for industrial implementation.
- Conventional and advanced methods of Portland cement concrete mix design are applicable when the new hydraulic cements replace Portland cement; the relationship between water/cement ratio and strength needs to be adjusted when using the sustainable hydraulic cements developed in the project.
- High-performance concrete materials matching or surpassing the mechanical, physical, barrier and durability characteristics of Portland cement concrete can be prepared with the sustainable class of hydraulic cements developed in the project.
- Conventional methods of industrial-scale concrete production and field construction suit concrete materials prepared with the new class of hydraulic cements.
- Guidelines were developed for implementation of the mechanical approach to processing of sustainable hydraulic cements in a continuous mode of operation that facilitates industrial-scale implementation.
- The optimum approach to transformation of the more inert raw materials (e.g., crystalline rocks and soils) into hydraulic cements may require exposure of raw mateirals to moderately elevated temperatures to supplement input of mechanical energy.
- Quality control procedures were developed to facilitate production of the sustainable hydraulic cements to reliably meet standard requirements and to reach their potential in terms of sustainability, economy and production throughput.
- The new class of hydraulic cements promise to reduce the carbon footprint and energy content of normal Portland cement by about 75%, and lower its product cost by about 50%. The potential to tailor existing cement manufacturing plants towards production of the new hydraulic cements further add to their market appeal.
Commercialization
market adoption of the new class of hydraulic cements developed in the project. The new class of hydraulic cements can be used in the mainstream concrete construction projects either as full replacement for Type I Portland cement or in blended cement where the new hydraulic cements are used together with a minor dosage of Type I Portland cement.
SBIR Phase I:
An Alternative Concrete Chemistry with Significantly Enhanced Durability, Sustainability, Economy, Safety and Strength | 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.