Air Contents and Air-Entraining Admixture in the Concrete
Environmentally Friendly Pervious Concrete for Treating Deicer-Laden Stormwater (Phase I) Interim Progress Report Dr. Xianming Shi, P.E. Gang Xu, P.E. https://sites.google.com/site/greensmartinfrastructure Department of Civil & Environmental Engineering Washington State University Problem Statement Stormwater control is a national priority since non-point sources continue to rank as leading causes of water pollution. Deicer stormwater is a new challenge. Pervious concrete is considered a successful Low
Impact Development (LID) technology and has been increasingly used as a stormwater BMP for parking lots, sidewalks, and other applications. The production of Portland cement (the most common binder in concrete) is an energyintensive process that accounts for a significant portion of global CO2 emissions and other greenhouse gases. Background Pervious concrete pavements reduce the quantity of stormwater runoff and improve its water quality by reducing total suspended solids, total phosphorous, total nitrogen, and metals. The utilization of nanotechnology to enable expanded use of waste and recycled materials is an unexplored area with great potential.
Project Objective Expand the use of industrial waste and recycled materials (such as fly ash and recycled glass) in pervious concrete (Phase I) Explore the potential of such greener pervious concrete for the treatment of deicer-laden stormwater under a variety of contaminant loading scenarios (Phase II) Identify Green Constituents of Pervious Concrete Locally available fly ashes serve as alternative binders Recycled glasses serve as alternative aggregates
Local black liquor from pulp plants serve as alternative mixing water Identify Green Constituents - Fly ash Four types of locally available fly ashes were identified as: WA ash WA C & F fly ash Centralia Coal Plant, Washington OR C fly ash Boardman Coal Plant, Oregon MT C fly ash (control group)
OR ash MT ash Identify Green Constituents - Recycled Glass & Black Liquor Recycled glass Currently working with Washington State Department of Ecology to identify reliable sources Black liquors from pulp plants 1. Clearwater pulp plant at Lewiston, ID 2. Michelsen pulp plant at Yakima, WA
Evaluate Green Constituents - Fly ash WA C & F ash evaluation by XRF. WA C Content SiO2 Percentage (wt. %) 33.4% WA F Content SiO2 Percentage (wt. %)
31.4% Al2O3 14.9% Al2O3 13.3% CaO 14.6% CaO 10.2%
MgO 4.7% MgO 3.6% Na2O K2O 3.7% 1.22% Na2O K2O
4.2% 1.34% Fe2O3 5.4% Fe2O3 7.4% SO3 1.5% SO3
2.6% Evaluate Green Constituents - Fly ash OR C & MT C ash evaluation by XRF. OR C Content SiO2 Percentage (wt. %) 23.6% MT C Content
SO3 Comparison of key contents in fly ash Evaluate Green Constituents - Fly ash Evaluate the identified fly ashes as cementitious bin Evaluate Green Constituents - Fly ash Experiment by using uniform design scheme Evaluate Green Constituents - Fly ash Sample (2x4 cylinders) fabrication & testing
Evaluate Green Constituents - Fly ash Experiment results (total 27 groups; 324 samples) Table.2 28-day Compressive Strength of Mortars with Different Factor Levels Run No. Factor 1 (X1) Factor 2 (X2) Factor 3 (X3) Factor 4
- Fly ash Experiment results (total 27 groups; 324 samples) Figure.1 Compressive Strength of Mortars with Different Factor Levels Evaluate Green Constituents - Fly ash Experiment results analysis by ANOVA and regression techniques compressive strength models Evaluate Green Constituents - Fly ash Model Visualization & Verification (1)
3D contour diagram of 3-day compressive strength model and model prediction vs. actual data Evaluate Green Constituents - Fly ash Model Visualization & Verification (2) 3D contour diagram of 28-day compressive strength model and model prediction vs. actual data Evaluate Green Constituents - Fly ash Model Errors Normal probability plot for 3-day fc model
Normal probability plot for 28-day fc model Evaluate Green Constituents - Fly ash Effects of each mixture component on compressive strength Trace plot for 3-day fc model Trace plot for 28-day fc model Evaluate Green Constituents - Fly ash Elastic Modulus of Mortars Effect of SBR on elastic modulus
at 28-Day. Control: MT C ash. Elastic modulus over time with 0% SBR Evaluate Green Constituents - Fly ash SEM/WDS Analysis (1) A B SEM micrograph of mortar surface cured for 7 days. A) 1000X magnification. B) 10000X magnification
Evaluate Green Constituents - Fly ash SEM/WDS Analysis (2) SEM micrograph of cenosphere with clustered small spheres inside. Evaluate Green Constituents - Fly ash SEM/WDS Analysis (3) Al Elemental mapping of mortar surface at 7 days. 1) Al. 2) Ca. Ca Evaluate Green Constituents
- Fly ash SEM/WDS Analysis (4) Si Elemental mapping of mortar surface at 7 days. 1) Si. 2) S. S Evaluate Green Constituents - Fly ash SEM/WDS Analysis Conclusion Preliminary DOE Since Si & Al dissolution rates from fly ash spheres are at the same level (Brouwers 2002), the lack of Si indicates that Al is mainly from C3A or Kleinite in fly ash and the dissolution of glassy structure of fly ash is slow.
The element maps show that hydration products are rich in Al, Ca and S, which indicates that hydration products are mainly ettringite and monosulfate. (consistent with observation from Wang, 2004) Only very small amount of Si is detected, which indicates the hydration of fly ash sphere is at very low level and C-S-H gel (key Evaluate Green Constituents - Fly ash Evaluation Conclusion Preliminary DOE A group of pure fly ash mortars show the highest compressive strength of 3000 psi at 28 days. ASTM C270 requires a minimum compressive strength of 1800 psi for Type S mortar at 28 days. The close correlation between the experimental values and predicted values confirms the fitness of the compressive strength models. Predictive equations (Models) could help optimize compression strength of the green mortars subject to other constraints (e.g., cost). SEM/WDS tools can shed light on the hydration mechanism of fly ashes.
Evaluate Green Constituents - Fly ash To further improve the fly ash mortar strength: 2nd DOE 1. 2. 3. 4. Additives to improve ions transport behavior A (max. 4% improvement) B (max. 5% improvement) C (max. 2% improvement) D (max. 8% improvement)
1. 2. 3. 4. 5. Chemical activators to improve fly ash reactivity E (max. 15% improvement) F (max. 5% improvement) G (max. 32% improvement) H (max. 34% improvement) I (max. 21% improvement) Evaluate Green Constituents - Fly ash Improve the fly ash mortar strength -contd
Mechanical activation to improve ash reactivity 1. Grind fly ash (max. 19% improvement) New sequence of fabrication Evaluate Green Constituents - Fly ash 2nd DOE: Synergy effects of activators Evaluate Green Constituents - Fly ash Preliminary Conclusion 2nd DOE A group of pure fly ash mortars show the highest compressive strength of 3200 psi at 7 days, which shows about 75% improvement from 1st DOE (1800 psi at 7 days). The identified chemical activators are very effective to improve the reactivity of OR C fly ash.
There are certainly synergistic effects of different activators, compared with the strength improvement from each individual chemical activator. Evaluate Green Constituents - Fly ash Future Research Focuses 2nd DOE Develop compressive strength models to describe the synergistic effects of different chemical activators. SEM/WDS analysis of hydration products with chemical activators. Categorize class C fly ashes into non-reactive, low-reactivity and high-reactivity fly ashes based on the understanding of hydration mechanisms learned from this project. Utilize the improved fly ash pastes with recycled glass, black liquor, and nano-materials to develop pervious concretes. Additional Testing of Green
Pervious Concretes Compressive strength, elastic modulus, splitting tensile strength Abrasion resistance Salt scaling resistance (to be conducted by WTI) Total porosity Potential for treating deicer-laden stormwater Products and Timeline One poster presented at Academic Showcase, WSU, March 27, 2015: Environmentally Friendly Mortars with Coal Fly Ashes as Cementitious Binder. One poster to present at the 6th Advances in Cement-Based Materials, July 20-22, 2015, Manhattan, KS. Two papers in preparation for the TRB 2016 Annual Meeting, Washington, D.C. and also for peer-reviewed journals. One patent application to be prepared by Dec. 2015. Project end date: extend from Sept. 30 to Dec. 30, 2015.
Acknowledgements Thanks for funding from CESTiCC Thanks to BASF, Boral and Lafarge for donated materials Thanks to Composite Materials and Engineering Center (CMEC) at WSU for providing test equipment. Dr. Owen K. Neil, Dr. J. Daniel Dolan, Dr. Mehdi Honarvarnazari, Jiang Yu, Sen Du at WSU also provided valuable assistance in experiments.
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