Curing concrete in "carbonated water"

Classified in Physics

Written at on English with a size of 10.73 KB.

 

Shrinkage Reducing Admixture  “product or product residue may explosively Combust…” • Superplasticizer  Kills fish and ruins water – never pour down a Drain! • Colloidal Silver  “…known to cause birth defects…” • Silver Nitrate Solution  A poison, oxidizer, and corrosive!

Nitric acid + nitrobenzene = spontaneous explosion  We have separate storage for acids vs bases vs   Disposable safety gloves  One-time use  Remove and throw out when exiting lab • Neoprene gloves  For acids/bases  Wash outside fully before removing so next person Can use them safely • Lab coats  Protect skin from chemicals, broken glass, Abrasions  Protects your experiments from outside schmutz  According to Bruce Tuckman: • Forming  Most members positive, polite. Roles not yet defined. Some anxiety. Leaders important. • Storming  Pushing against boundaries; resentment at defined roles; challenges To authority; different work styles cause trouble; testing of boundaries • Norming  Resolving differences; growing respect each other; recommit to team Goals • Performing  Actual doing work; delegation of tasks; members joining or leaving Causes few problems • Adjourning  May be stressful for those who like structure    High context culture  Appropriate communication depends on Decoding the situation, the relationship, the Non-verbal behavior (the context)  Invest time in getting to know people • Low context culture  Appropriate communication depends on using concrete, logical, unambiguous task-oriented Language  So we should be explicit and transparent (personal relationships are nice, but not Necessary)   Reflection 2. Team Charter 3. Task List (generic, with rotation) 4. Problem Solving 5. Communication styles N.B.: Chapter 8 is how to troubleshoot Problems! Might need it! Teams produce best, most widely Applicable results when they have “… the widest possible range of Personalities, even though it takes longer For such psychologically diverse teams to Achieve good cooperation. They must first Cultivate an openness to opposing Opinions and recognize the value of Exploring a problem from various angles”  Clinker: Comes out of factories • Clinker + gypsum  Cement, the powder that You buy in the store • Cement + Water  Cement Paste • Cement paste + sand  Mortar • Cement paste + sand + gravel  Concrete • There’s also a lot of admixtures • The ‘p’ in portland cement is not capitalized  John Smeaton • Looking for a new material For third lighthouse in 1756 • Discovered that limestone And clay, when burned and Ground, hardens underwater Eddystone Lighthouse  “Roman Cement” patented 1780 • Competitors emerge ~1810 • Joseph Aspdin creates portland cement On his stove in 1824 • His son William makes better version, 1842 Annually:  2,800 Mt of OPC  6,600 Mt of concrete • 1 cubic meter per person per year • OPC consumes 5% of industrial energy Supply worldwide • A ton of cement produces at least 0.85 Tons CO2 • 3rd largest CO2 producer, roughly 5% ~ 40 vol.% cement paste • ~ 60 % aggregates Good compressive strength • Lousy tensile strength  This is why we use reinforcing steel • Universal raw materials • Holds water without corroding • Malleable • Very cheap Normal concrete (what we’ll talk about) • Pre-cast Concrete • High Performance Concrete (HPC) • Ultra-High Performance Concrete  Fiber reinforcement! • Shotcrete  Mike Rowe said this was his worst job  Aggregate quality has an effect  Grading (particle size, distribution)  Nature (shape, porosity, texture, etc.) • Controls economics  Use the largest possible depending on Reinforcing steel, slab thickness, etc.  Maximum size no more than 1/5 the narrowest Dimension between forms or ¾ the space Between bars • Grading can influence workability Coarse aggregates:  80% Sedimentary rocks – near the surface  Generally range between 3/8 and 1.5 inches In diameter  Gravels or crushed stone  Fine aggregates:  Natural sand or crushed stone  Passing through a 3/8-inch sieve  Comes from riverbeds or beaches • But you must wash off chlorides first! • Why don’t we grind quarried materials?  Clean  Nothing to prevent a good bond! • Shape  Too flat leads to bad mixing, anisotropy • Texture  Rough: Better bond  Smooth: Better mixibility, flow, etc. • Isotropic  “Flakiness” is bad! • Not reactive  No impurities  Nothing that will react with aggressive media  Alkali-silicate reaction (ASR)  Cement reacts with silica in aggregates to Form an expansive gel • Alkali-carbonate reaction (ACR)  Cement reacts with carbonates in aggregates To form… different carbonates • Sulfate attack  Many different forms  Turns cement paste to mush, aggregates fine! This lecture prepared with materials provided by Lorraine Higgins, WPI Writing Center Proper Preparation Prevents Poor Performance • Planning – Ask yourself BEFORE writing:  What am I trying to say?  Who am I trying to say it to?  What am I trying to gain by writing this? • Make SURE you have:  Enough time  Enough sleep  A quiet place What is this lab about? Why should anyone care?  Move: Introduce the topic that you are investigating  Move: Explain the opportunity that calls for research What technical concepts must I know to understand this work? How does this build On the work of others?  Move: Define background concepts  Move: Review and evaluate previous studies  Move: Cite sources!  Move: Overview objective and parameters of current study  What did you do? How did you do it? • Move: Explain materials and methods in past tense. • Move: Include visuals as necessary • Move: Show formulas and refer to standards as necessary  What happened? Where’s the evidence?  Move: Use section headings as appropriate  Move: Briefly summarize each finding  Move: Support findings by referring to figures and tables or discussing key measures  Move: Refer to appendices for raw data  Move: Remind your reader how you arrived at key findings  What does it all mean? What are the implications?  Move: Sum up key findings, describe patterns and relationships  Move: Interpret findings and provide context  Move: Discuss anomalies (not shown in this example). Your results are your CLAIM • Your discussion is your SUPPORT  How has your research changed anything?  Move: Summarize entire paper BRIEFLY  Move: Point out implications and recommendations for the future  According to Williams/Ireton:  Of self  Of authorship  Of words  Of structures  Of ideas Mix design  Determining the needed characteristics of your Concrete, reflecting final usage of structure • Mixture proportioning  Selecting the ingredients for your concrete • Properly proportioned concrete should:  Have acceptable workability  Have good durability, strength, appearance  Be economically feasible • Keep in simple! Too complex is hard to control Concrete usually selected on a Strength basis  Durability, permeability, etc. Becoming more important • Minimum cement contents Protect finishability, durability, Etc. • First item: w/c ratio  Determines workability  Strength is inverse to water content • More water  more porous  less Strong w:c should be the lowest value required For anticipated conditions • Concrete gains strength over time as Hydration reactions continue • Temperature, humidity are most Important factors in curing f’ C is the strength at 28 Days (avg. Of 3) • ACI318 requires 17.5 MPa (2500 psi)  No single sample can be 3.5 MPa below average • Always aim a little Higher than the required Strength to have a Safety factor  f’cr is f’c plus a little Wiggle room  Entrained air  Reduces freeze/thaw Damage  Mild, moderate, or severe Exposure categories  Amount depends on aggregate properties  Can reduce the amount of Water needed  Targets are hard to hit: for 6%, aim for 5–8% Water-reducing admixtures improve Workability, thus allow a reduction of Water up to 12% • High-range water reducing admixtures (superplasticizers) reduce water 12-30% Anticorrosion • Accelerators • Set retarders • Colorants • Multiple admixtures should be tested Together ahead of time to ensure Compatibility Use previous mix design with f’c within 7 MPa (1000 psi) of your requirements  Assuming materials and characteristics are Similar/the same  Determine if f’cr is met based on 45 trials  2  f’c < 35 MPa  3  f’c > 35 MPa Step 1: Strength Table 9-1: since 35 > 31, we go with 35 • Table 9.11: f’cr = f’c + 8.5  35 + 8.5 = 43.5 w:c ration Step 3: Air Content Step 4: Slump Step 5: Water Content Step 6: Cement Content • Simple math! • 135 kg water per m3 divided w:c ratio of 0.31 yields 435 kg cement per m3 • This is greater than 310 kg cement per M3 from Table 9.7  Step 7: Coarse Aggregate Content • Figure 9.3: Volume Fraction of 0.67 • Since it has a unit Weight of 1600 kg/m3:  1600 x 0.67 = 1072 kg (dry)  From the MSDS, we would learn that 8% Air content requires 0.5g admixture per Kg cement  0.5 x 435 = 0.218 kg • WRA is used at 3g per kg cement  3 x 435 = 1.305 kg Step 9: Fine aggregate content • We can add up all other volumes per m3  Mass / (Relative density*density of water) = volume • Water = 135 / (1 x 1000) = 0.135 m3 • Cement = 435 / (3 x 1000) = 0.145 m3 • Coarse Agg. = 1072 / (2.68 x 1000) = 0.4 m3 • Air (different!) = 8/100 = .08 m3  Total volume of known material: .76 m3  Therefore FA is 1 - 0.76 = .24 m3  Viz and to wit: 0.24 x 2.64 x 1000 = 634 kg Water 135 kg • Cement 435 kg • Coarse agg. (dry) 1072 kg • Fine agg. (dry) 634 kg • AEA 0.218 kg • WRA 1.305 kg  (The admixture volume is so low that we can Ignore it. But other admixtures, such as Corrosion inhibitors are very large, and need to Be accounted for in w:c) 1072 x 1.02 = 1093 kg coarse aggregate • 634 x 1.06 = 672 kg fine aggregate • CA surface water = 2% - 0.5% = 1.5% • FA surface water = 6% - 0.7% = 5.3% • (Or: How wet it is – what it can absorb) • Therefore, total water:  135 – (1072 x 0.015) – (634 x 0.053) = 85 kg Water 85 kg • Cement 435 kg • Coarse agg. (dry) 1093 kg • Fine agg. (dry) 672 kg • AEA 0.218 kg • WRA 1.305 kg

Entradas relacionadas: