boom
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