Final Report: Waste to Value: Incorporating Industrial Symbiosis for Sustainable InfrastructureEPA Grant Number: SU831810
Title: Waste to Value: Incorporating Industrial Symbiosis for Sustainable Infrastructure
Investigators: Ramaswami, Anu , Clark, Tom , Rens, Kevin , Wright, Sean
Institution: University of Colorado at Denver
EPA Project Officer: Nolt-Helms, Cynthia
Project Period: September 30, 2004 through May 30, 2005
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2004) RFA Text | Recipients Lists
Research Category: P3 Challenge Area - Materials & Chemicals , Pollution Prevention/Sustainable Development , P3 Awards , Sustainability
Current “green building” guidelines establish qualitative environmental goals, relating to the energy associated with the transportation of the product and not the energy of production, termed embodied energy. however, sustainability of the urban built environment requires choosing building materials based on quantitative structural, thermal, environmental, and economic criterion.
The primary innovation in Phase I was the consideration of alternative waste materials that could be incorporated into construction materials to lower the embodied energy of the urban infrastructure. The incorporation of high volumes of fly ash (HVFA) as a substitution for Portland cement required real-time concrete safety testing, and the use of an overall LCA/LCC framework to evaluate the overall economic and environmental benefits and cost. of incorporating fly ash and waste oil metals. The industrial symbiosis study also identified metals from filtered waste oil as a potential substitution for aggregates in concrete and led to the P3 Phase II proposal for a larger scale bulk-Material Flow Analysis (bulk-MFA) to evaluate the potential for symbiosis within the infrastructure of a middle-sized city in the United States: Longmont, Colorado.
The project teams research during the P3 Phase I investigation evaluated substitution of Portland cement with primarily Class F fly ash ranging from 40 to 70 percent by weight (typical concrete-ash mixes contain between zero and 15 percent fly ash). Recently Class C fly ash was included in the construction of a prestressed double-tee girder. Further testing is proposed in the Phase II proposal. The goal of P3 Phase I study was to evaluate procedures necessary to select HVFA mixes that provided a significant reduction in embodied energy and met design criteria for structural elements. Performance testing of 12 HVFA “mini-mixes” was initially completed to select promising mixes to carry forward for further full-scale testing. The mixes were divided into three ranges of total cementitious content (low-L, medium-M, and high-H). The total cementitious material for the three sets was 327-kg/m3 (550 pounds per cubic yard) for the low (L), 369-kg/m3 (620 pounds per cubic yard) for the medium (M), and 4 10-kg/m3 (690 pounds per cubic yard) for the high (H). Each range of cementitious content was further divided into four total fly ash replacement percentages of 40, 50, 60, and 70. The mixes were named accordingly (e.g., medium cementicious content with 60 percent fly ash replacement was termed M60).
The performance testing included laboratory durability and strength testing and the construction of concrete products: a precast manhole, a precast structural double-tee girder, and the installation of road panels and curb and gutter sections in the Denver. Colorado. The range of products produced under the P3 Phase I provided a better understanding of insitu workability and contractor logistics.
The compressive strength test results for the 12 mixes at 1, 3, 7, 28, and 56-day breaks are shown in Figure 1. The performance of these mixes at early-age strength showed promising results. All of the tests met the 1-day break strength of 10.35 MPa (1.500 psi), except for L70, M70, and L60. However, only the L70 mix failed to meet the 28-day strength of 27.6 MPa (4,000 psi).
The early-age compressive strength and the high volume of fly ash content led to the selection of four mixes for full scale testing. Four mix designs were chosen for full-scale testing from the MM results. L50 (1-day 10.00 MPa/28-day 43.61 MPa), M50 (1-day 12.41 MPa/28-day 52.40 MPa), H60 (1-day 12.24 MPa/28-day 55.85 MPa), and H70 (1- day 6.20 MPa/28-day 39.99 MPa). In addition, three 100 percent Portland cement mixes (zero percent fly ash) were included for comparison purposes (LO, MO and HO). The tests run on all samples included; compressive strength (ASTM C 39), slump (ASTM C 143), air content (ASTM C 231), and temperature (ASTM C 1064). All samples were compared on the basis of an approximate five-inch slump. The full-scale compressive strength test results are shown in Figure 2.
There was a significant difference in compressive strength between the “mini-mix” (MM) and the full-scale mix results, particularly in the early age strengths. The 28-day and 56- day compressive strengths were acceptable for structural and non-structural concrete applications. The air contents were within acceptable limits, suggesting that air entrainment is as simple for HVFA concrete as it is for conventional portland-cement concrete. Further testing is proposed in P3 Phase II.
Getting HVFA into the Market Place — the 4th P (Product)
The products produced during the P3 Phase I included the following:
- Precast Manhole: 1.83 m (72 inch - height and diameter) precast manhole, designed for AASHTO HS-20 traffic loading.
- City and County of Denver: Cast-in-Place Alley Slab and Curb-and-Gutter
The City and County of Denver Streets Department used the H60 mix for an alley panel and curb and gutter sections.
- Pre-Stressed Structural Double-Tee Girder: prestressed slabs and a structural double-tee girder using the H60 mix. For comparative purposes, the mix was modified to substitute Class C fly ash for Class F and Type III for Type I/II cement.
Streamlined Life Cycle Assessment and Costing Analysis
Life cycle costs and environmental impacts were evaluated with BEES Version 3.0 software (NIST, 2003). The environmental indicators of concern for this evaluation were the following: water intake, smog, human health, global warming, fossil fuel depletion, eutrophication, ecological toxicity, and critical air pollutants. The 70 percent fly ash mix provided a 26.6 % reduction in environmental performance when compared to 100 percent Portland cement. The LCA results are shown in Figure 3.
In addition, a 10.3 percent reduction in LCC economic costs was evaluated for 35% fly ash when compared to OPC. This result was linearly extrapolated to estimate a 21.3% reduction for 70% fly ash inclusion.
Waste Oil Metals
A bulk sample of waste metals was obtained from Thermo Fluid industries in Denver, Colorado. A reduction in strength was not anticipated as it was planned to replace the fine fraction of aggregate with the metals. However, the metals required a very high water to cementicious materials (w:cm) ratio of 1 .12 to maintain a slump of 5 inches. This may account for the very low early age compressive strengths for the 7 and 14 day breaks were 10.4 MPa and 13.5 MPa respectively. Also, the filtered metals still retained a very “organic” odor. Because the embodied energy of the concrete is not reduced due to the filtering process and large amounts of water per mix, the low compressive strength and the pervasive smell of the final concrete product, further tests incorporating the metals are not proposed in Phase II.
The benefits of locating industrial waste streams and incorporating waste materials into new construction materials will lower the overall embodied energy of the built environment. This study has proven that the performance of the materials will not hinder these possibilities. In addition, the lower batch costs is a strong incentive for contractors, thus a mutual goal is establish for using high percent recycled material products. One of the goals of P3 Phase II will address the concept that building codes are prescriptive in limiting the amount of recycled material in concrete. The P3 Phase I study of industrial symbiosis initiated locating waste material streams.
Proposed Phase II objectives and strategies:
Concrete, being a major component of the built environment, offers an opportunity for significant reductions in the associated environmental impacts of construction. The P3 Phase II will build upon the success of the Phase I study by refining mixes of high percent post-industrial recycled content concrete and taking further steps to construct products as empirical examples in order to market “green” concrete in the urban built environment. In addition, building codes will be investigated that may set, or are perceived to set, prescriptive limits on recycled content. The testing planned includes the following:
- Optimal 1-IVFA mix: The next phase of testing will seek to identify an optimal fly ash and w:cm ratio.
- Slag (steel waste product): The embodied energy of high slag content concrete will be evaluated in addition to strength and durability testing.
- Class C Fly Ash: Class C fly ash is a readily available waste material. The optimal HVFA Class F mixes will be compared to similar mixes using Class C fly ash.
A bulk-Material Flow Analysis (bulk-MFA) of Longmont, Colorado (population 85.000) will build upon the industrial symbiosis investigations of Phase I by identifying waste to value potential within a city infrastructure. In addition, the study will provide management tools for decision-makers to evaluate the environmental performance of the city infrastructure as a whole. This study may also serve as an educational tool for the residents of Longmont to better understand the impact of materials used in the urban built environment. Mid-point environmental indicators will be evaluated with LCA/LCC software BEES 3.0 and Athena Environmental Indicator.
The primary metrics for the Phase II proposal outcomes assessment are:
- Percent waste material recovered or reused,
- Percent waste energy reused or recovered,
- Structural and durability performance of ”green” concrete,
- Number of ”green” concrete products put into the field, and
- Identification of restrictive building codes for green materials.