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Replacing Energy Intensive Cements with Blast Furnace Waste and Recycled Concrete : 

Replacing Energy Intensive Cements with Blast Furnace Waste and Recycled Concrete Project Team: University of Pittsburgh University of Washington Dr. Amir Koubaa Dr. Donald Janssen, P.E. Dr. Julie M. Vandenbossche, P.E. Ms. Nancy M. Whiting

Outline: 

Outline Background Research objectives Approach/results Sustainability Future research

Cement production: 

Cement production Limestone Clay Silica Sand Kiln (Heat raw materials to 1500C [2500F]) Clinker Gypsum Mill Portland Cement CO2

Environmental impact of Portland cement : 

Environmental impact of Portland cement Production of 1-ton of PC: extremely energy intensive (consumes 180 - 320 kwh) produces 1 ton of CO2 Nearly 2 billion tons PC produced per year 5% - 8% of the CO2 output worldwide comes from the production of PC

Project goals: 

Project goals Reduce CO2 emissions by 50% Reduce energy consumption in production Replace raw materials with industrial waste Maintains characteristics similar to Portland cement (PC) concrete Develop a more sustainable concrete that….

Strategic approach: Produce blended cements: 

Strategic approach: Produce blended cements Inter-grinding: PC clinker Granulated blast furnace slag (GBFS) Addition of either Recycled concrete dust (RCD) Concrete truck wash-out fines (WOF)

GBFS: 

GBFS Advantages Industrial by-product of the steel industry Little additional energy needed Cementitious properties similar to PC Disadvantages Hydration is significantly slower than PC Delays in set times and strength gain Costly delays in construction Increased potential for premature failure

RCD or WOF: 

RCD or WOF Waste by-product of the concrete industry Some cementitious properties Provide nucleation sites (Accelerates the hydration process)

Blended cements: 

Blended cements Criteria for a successful blend: Contains less than 50% PC clinker Hydration and strengths similar to 100% PC concrete Proportions evaluated PC: 40% - 90% GBFS: 0% - 55% RCD: 0% - 20% WOF: 0% - 12%

Notation: 

Notation Clinker/GBFS/RCD (or WOF) Example: 55/40/5 55% PC clinker 40% GBFS 5% RCD or WOF

Materials characteristics affecting performance: 

Materials characteristics affecting performance Fineness Chemical analyses Glassy content of GBFS

Fineness: 

Fineness %Passing 75-μm Dry Sieve Analysis %Passing 45-μm Sieve Wet Sieve Analysis ASTM C204 Standard Test Method for Fineness of Hydraulic Cement by Air-Permeability Apparatus Estimates the total surface area “Blaine” (m2/kg)

Fineness (cont): 

Fineness (cont)

Materials characteristics (cont): 

Materials characteristics (cont) Chemical analyses (results pending) Oxide analysis (clinker, GBFS, RCD and WOF) Using atomic absorption Glass content of the GBFS > 95% Visual estimate (100X) Transmitted light microscopy in cross-polarized light

Phase I Testing of Hydraulic Cement Paste Mixes: 

Phase I Testing of Hydraulic Cement Paste Mixes

ASTM C187 Standard Test Method for Normal Consistency of Hydraulic Cement: 

ASTM C187 Standard Test Method for Normal Consistency of Hydraulic Cement Paste Consistency Setting Time ASTM C191 Standard Test Method for Time of Setting of Hydraulic Cement by Vicat Needle Paste mixes 20 Blends created 31 Consistency tests 8 Pass for set time testing Results

Consistency test results: 

Consistency test results

Set time test results: 

Set time test results

Phase II Testing of Mortar Mixes: 

Phase II Testing of Mortar Mixes

Compressive Strength: 

Compressive Strength ASTM C109M Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in [50-mm] Cube Specimens) 1, 3, 7 and 28 days 2-in cube Heat of Hydration Thermocouple and datalogger Recording temperature at 1 minute intervals Mortar mixes

Compressive strength of blends: 

Compressive strength of blends

Compressive strength results: 

Compressive strength results

Heat of hydration results: 

Greater the area under the curve the more extensive the hydration (increased strengths). Heat of hydration results

Heat of hydration for WOF: 

Heat of hydration for WOF 0 0.025

Compressive strength test matrix: 

Compressive strength test matrix

Early compressive strength : 5% RCD: 

Early compressive strength : 5% RCD

Slide27: 

28-day compressive strength: 5% RCD

Early compressive strength results: 5% WOF: 

Early compressive strength results: 5% WOF

28-day compressive strength results: 5% WOF: 

28-day compressive strength results: 5% WOF

Sustainability: 

Sustainability 39% CO2 reduction for opt. blend 43% of PC can be replaced with waste materials

Future work: 

Future work Relate material characteristics to performance Test additional sources of recycled fines Successful mixes should be tested for: Shrinkage characteristics Freeze/thaw durability permeability scaling corrosion resistance Trial full scale production