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