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Chapter 4 preliminary design Properties of concrete
8

Chapter 4 preliminary design Properties of concrete

Chapter 4 preliminary design Properties of concrete

(OP)
As many would already know i am writing some notes on an undergrad manual that will go in the FAQ, the next chapter has some simple properties of concrete. These are from notes i have taken over time, two or more are from posts in this forum, other are from the net.bigears

If you have the time please look through them and comment on anything you do not agree with.

Or if you have any properties that you think should be apart of this list, please post.

Properties
1.    Temperature and shrinkage causes tensile forces in concrete, due to the interaction of reinforcement and concrete; Cracking levels depend on,
 a)    Tensile strength of concrete.
 b)    The cover thickness.
 c)    The diameter of rebar  
 d)    Rate of corrosion.

2.    Poisson's ratio: A value of about 0.2 is usually considered for design.

3.    Shear strength: The strength of concrete in PURE SHEAR has been reported to be in the range of 10 to 20% of its compressive strength.

4.    Factors influencing creep:
 Creep increases when,
a) Cement content is high,
b) w/c ratio is high,
c) Aggregate content is low,
d) Air entertainment is high,
e) Relative humidity is low,
f) Temperature (causing moisture loss) is high,
g) Size / thickness of the member is small,
h) Loading occurs at an early age &
i) loading is sustained over a long period.

5.    Effect of creep:
Detrimental results in RC structures due to creep:
a) Increased deflection of beams and slabs.
b) Increased deflection of slender columns (possibly leading to buckling)
c) Gradual transfer of load from concrete to reinforcing steel in compression members.
d) Loss of prestress in prestressed concrete.

6.    In order to reduce the effect of creep-deflection it is advisable to use 0.2% of cross sectional area at the compression face.

7.    Symmetrical arrangements of reinforcement will aid to avoid the differential restraint.

8.    Reduction of moments on account of moment redistribution is generally NOT APPLIED TO COLUMNS.

9.    Reinforcement availability:
Standard diameter sizes (mm): 6, 8, 10, 12, 16, 20, 24, 32, 40
Standard lengths: > 12mm diameter: 12 metres
< 12mm diameter: from a coil

10.    These values are approximate and should be used only as a check on the total estimated quantity:
Slabs - 80 - 110 kg/m3 (flat slab120-220kg/m3)
Columns - 200 - 450 kg/m3
Walls - 40 - 100 kg/m3
R/C footings 70-90 kg/m3
Pile caps - 110 - 150 kg/m3
Rafts - 60 - 70 kg/m3
Beams - 150 - 220 kg/m3
Transfer slabs 150kg/m3
Retaining walls-110kg/m3
Stairs – 135kg/m3
Note: The actual reinforcement quantity in the element will vary according to detailing practice and efficiency of the concrete element.

11.    In normal circumstances and where N grad concrete is used, forms may generally be removed after the expiry of the following periods:     
Type of Form Work (Location)                             Min period before striking Form Work
a)    Vertical formwork to columns, Walls, beam                                    16 - 24 hrs
b)    Soffit formwork to slabs (props to be re-fixed immediately after removal of formwork)                   3 days
c)    Soffit formwork to beams (props to be re-fixed immediately after removal of formwork)                7 days
d)    Props to slabs: (1) Spanning up to 4.5m 7 days (2) Spanning Over 4.5m                                14 days  
e)    Props to beams & arches:(1) Spanning up to 6m 14 days  (2) Spanning Over 6m         21 days

12.    CONCRETE MIX RULES OF THUMB
•    ADDING 3L OF WATER TO ONE CUBIC METER OF FRESHLY MIXED CONCRETE WILL:
a.    Increase slump about 25mm
b.    Decrease compressive strength about 1 to 2 mPai
c.    Increase shrinkage potential about 10%
d.    Waste as much as 1/4 bag of cement
•    IF FRESHLY MIXED CONCRETE TEMPERATURE INCREASES 10 DEGREES:
a.    About 3L OF WATER TO ONE CUBIC METER maintains equal slump
b.    Air content decreases about 1%
c.    Compressive strength decreases about .5 to 1.2 mPai
•    IF THE AIR CONTENT OF FRESHLY MIXED CONCRETE:
a.    Increases 1%, then compressive strength decreases about 5%
b.    Decreases 1%, then slump decreases about 10mm
c.    Decreases 1%, then durability decreases about 10%

13.    The main components of cast-in-place concrete floor systems are concrete, reinforcement (normal and/or post-tensioned), and formwork. The cost of the concrete, including placing and finishing, usually accounts for about 30% to 35% of the overall cost of the floor system.

14.    Where normal 500 mPa reinforcement is utilized, a concrete mix with a compressive strength of 32mPa yields the least expensive system.

15.    Where post-tensioned reinforcement is used, a concrete compressive strength of at least 40mPa psi is usually specified to attain, among other things, more cost-effective anchorages and higher resistance intension and shear.

16.    Having the greatest influence on the overall cost of the floor system is the formwork, which is about 45% to 55% of the total cost.
Three basic principles govern formwork economy for site-cast concrete structures:
•    Specify readily available standard form sizes. This is essential to achieve economical formwork. Most projects do not have the budget to accommodate custom forms, unless they are required in a quantity that allows mass production.
•    Repeat sizes and shapes of the concrete members wherever possible. Repetition allows forms to be reused from bay to bay and from floor to floor, resulting in maximum overall savings.
•    Strive for simple formwork. There are countless variables that must be evaluated and then integrated into the design of a building. Economy has traditionally meant a time-consuming search for ways to reduce the quantities of materials. For example, it may seem appropriate to vary the depth of beams with the loading and span variations, providing shallower beams where the loads or spans are smaller. This approach would result in moderate savings in materials, but would create additional costs in formwork, resulting in a substantially more expensive structure—quite the opposite effect of that intended. Providing a constant beam depth while varying the amounts of reinforcement along the span length is the simplest and most cost-effective solution.

17.    ABRASIVE RESISTANCE of concrete increases with compressive strength and use of aggregate having low abrasion.

18.    Do you know that:
For steel bars to lose one mm diameter due to corrosion, it takes about 12.5 years. But due to practical reasons the number of years reduces due to hostile corrosive environment. For 6mm dia To corrode completely it takes about 75 years.
 

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

Item 6...I think "use" should be replaced with "reinforce".
Item 10...The reinforcement rate for columns seems very high. If a column is kept to 1% reinforcement the reo rate will be ~=78kg/m^3+lapping+ties. 200-450kg/m^3 looks high but I will check over some of the designs we have in our office and comment.

I know a good one you could include...Young's modulus of Concrete and Young's modulus of High Performance Concrete.

RE: Chapter 4 preliminary design Properties of concrete

One thing that stuck in my mind (from India) is to choose the rebars you use so that they are easily perceived as far as size from one to another.  India has bar sizes by 2mm (e.g., 16mm, 18mm, 20mm, 22mm, etc.)  This leads to mixups when the workers go "get some 20 mm bars) - they grab an 18 mm instead - the perception isn't there (18 to 20) and if QC isn't on the ball, the wrong size used.

RE: Chapter 4 preliminary design Properties of concrete

No 1, please add-e) modulus of elasticity of concrete and reinf f) spacing of reinf.

No 4, please add-j) properties of aggregate k) magnitude of loading.

No.5, please add-e)premature yielding of column reinf.

RE: Chapter 4 preliminary design Properties of concrete

For:

1...add f. cement content (or factor) of concrete
    add g. water-cement ratio of concrete
    add h. curing method and length of curing
    add i. aggregate gradation and type (high absorption coarse aggregate increases shrinkage)

2.  Poisson's ratio is generally taken as 0.15 for concrete

4...add j. coarse aggregate type and gradation

10. Is unclear.  State that these are gross section densities that vary with the amount of reinforcing steel.  The slab values relative to, say, retaining walls seem inconsistent.

14. Seems to an overly broad generalization

17. Should clarify that the aggregate shall have low abrasion loss under standardized testing or high abrasion resistance.  The term low abrasion is misleading.

18. The last sentence is only true under good conditions.  I've seen 6mm rebar corrode completely in 5 years or less under adverse conditions (coastal applications, poor consolidation of concrete, insufficient cover, use of chloride admixtures, etc.)

I'm not sure who your intended audience will be, but you might consider universalizing your terms and units.

Nice job.

Ron

 

RE: Chapter 4 preliminary design Properties of concrete

1 Please add, Reinf. spacing & Coefficient of expansion Alpha for aggregate, least for lime stone highest for granite

RE: Chapter 4 preliminary design Properties of concrete

Quote:

I'm not sure who your intended audience will be, but you might consider universalizing your terms and units.

I agree with Ron - It would be helpful to include inches, pounds, etc. for us old fashioned dudes.

Thanks,

 

RE: Chapter 4 preliminary design Properties of concrete

3
(OP)
I started out on this course with the intended audience as just being a few fresh faced engineer's that need a starting point for their designs, This is only the starting chapter of rules of thumb. however  evolutions occurs and the intended audience is now anyone whom reads it once it is finished in the FAQ, thus I have converted as much as I can to inch ect. However I don't know the standards for reo in any other country really, could have a stab but would really just be guessing.

sorry to post the whole thing again, but this is easier fo me bigcheeks

Properties
1.    Temperature and shrinkage causes tensile forces in concrete, due to the interaction of reinforcement and concrete; Cracking levels depend on,
a)    Tensile strength of concrete.
b)    The cover thickness.
c)    The diameter of rebar  
d)    Rate of corrosion.
e)     Modulus of elasticity of concrete and reinforcement
f)     Spacing of reinforcement
f)     Cement content (or factor) of concrete
g)     Water-cement ratio of concrete
h)     Curing method and length of curing
i)    Aggregate gradation and type (high absorption coarse aggregate increases shrinkage)
j)     Coefficient of expansion for aggregate, least for lime stone highest for granite
2.    Poisson's ratio: A value of about 0.15-0.2 is usually considered for design.
3.    Shear strength: The strength of concrete in PURE SHEAR has been reported to be in the range of 10 to 20% of its compressive strength.
4.    Factors influencing creep:
 Creep increases when,
a) Cement content is high,
b) w/c ratio is high,
c) Aggregate content is low,
d) Air entertainment is high,
e) Relative humidity is low,
f) Temperature (causing moisture loss) is high,
g) Size / thickness of the member is small,
h) Loading occurs at an early age &
i) Loading is sustained over a long period.
j) Coarse aggregate type and gradation
k) Magnitude of loading
5.    Effect of creep:
Detrimental results in RC structures due to creep:
a) Increased deflection of beams and slabs.
b) Increased deflection of slender columns (possibly leading to buckling)
c) Gradual transfer of load from concrete to reinforcing steel in compression members.
d) Loss of prestress in prestressed concrete.
6.    In order to reduce the effect of creep-deflection it is advisable to reinforce with 0.2% of cross sectional area at the compression face.
7.    Symmetrical arrangements of reinforcement will aid to avoid the differential restraint.
8.    Reduction of moments on account of moment redistribution is generally NOT APPLIED TO COLUMNS.
9.    Reinforcement availability:
Standard diameter sizes (mm): 6, 8, 10, 12, 16, 20, 24, 32, 40
Standard lengths: > 12mm diameter: 12 metres
< 12mm diameter: from a coil
If you're not going to inspect everything keep the difference in bars sizes greater than 3mm (1/8 inch).
10.    These values are approximate and should be used only as a check on the total estimated quantity:
Slabs - 80 - 110 kg/m3 (50-70lb/ft3) (flat slab120-220kg/m3 (75-140lb/ft3))
Columns - 200 - 450 kg/m3 (125-280lb/ft3)
Walls - 40 - 100 kg/m3 (25-65lb/ft3)
R/C footings 70-90 kg/m3 (45-60lb/ft3)
Pile caps - 110 - 150 kg/m3 (70-95lb/ft3)
Rafts - 60 - 70 kg/m3 (40-45lb/ft3)
Beams - 150 - 220 kg/m3 (95-140lb/ft3)
Transfer slabs 150kg/m3 (95lb/ft3)
Retaining walls-110kg/m3 (70lb/ft3)
Stairs – 135kg/m3 (85lb/ft3)
Note: The actual reinforcement quantity in the element will vary according to detailing practice and efficiency of the concrete element.

11.    In normal circumstances and where N-grade (normal) concrete is used, forms may generally be removed after the expiry of the following periods:     
Type of Form Work (Location)                             Min period before striking Form Work
a)    Vertical formwork to columns, Walls, beam                             16 - 24 hrs
b)    Soffit formwork to slabs (props to be re-fixed immediately after removal of formwork)        3 days
c)    Soffit formwork to beams (props to be re-fixed immediately after removal of formwork)        7 days
d)    Props to slabs:          Spanning up to 4.5m (16 ft)                     7 days                  Spanning Over 4.5m (16ft)                    14 days  
e)    Props to beams & arches:    Spanning up to 6m     (55ft)                    14 days                 Spanning Over 6m     (55ft)                    21 days
12.    CONCRETE MIX RULES OF THUMB
•    ADDING 3L OF WATER TO ONE CUBIC METER OF FRESHLY MIXED CONCRETE WILL:
a.    Increase slump about 25mm (1 inch)
b.    Decrease compressive strength about 1 to 2 mPa (200 to 300 psi)
c.    Increase shrinkage potential about 10%
d.    Waste as much as 1/4 bag of cement
•    IF FRESHLY MIXED CONCRETE TEMPERATURE INCREASES 10 DEGREES:
a.    About 3L (1 gallon) OF WATER TO ONE CUBIC METER (per cubic yard maintains) maintains equal slump
b.    Air content decreases about 1%
c.    Compressive strength decreases about 0.5 to 1.2 mPa (150 to 200 psi)
•    IF THE AIR CONTENT OF FRESHLY MIXED CONCRETE:
a.    Increases 1%, then compressive strength decreases about 5%
b.    Decreases 1%, then slump decreases about 10mm 1/2 inch
c.    Decreases 1%, then durability decreases about 10%

13.    The main components of cast-in-place concrete floor systems are concrete, reinforcement (normal and/or post-tensioned), and formwork. The cost of the concrete, including placing and finishing, usually accounts for about 30% to 35% of the overall cost of the floor system.
14.    Where post-tensioned reinforcement is used, a concrete compressive strength of at least 40mPa (5,000) psi is usually specified to attain, among other things, more cost-effective anchorages and higher resistance intension and shear.
15.    Having the greatest influence on the overall cost of the floor system is the formwork, which is about 45% to 55% of the total cost.
Three basic principles govern formwork economy for site-cast concrete structures:
•    Specify readily available standard form sizes. This is essential to achieve economical formwork. Most projects do not have the budget to accommodate custom forms, unless they are required in a quantity that allows mass production.
•    Repeat sizes and shapes of the concrete members wherever possible. Repetition allows forms to be reused from bay to bay and from floor to floor, resulting in maximum overall savings.
•    Strive for simple formwork. There are countless variables that must be evaluated and then integrated into the design of a building. Economy has traditionally meant a time-consuming search for ways to reduce the quantities of materials. For example, it may seem appropriate to vary the depth of beams with the loading and span variations, providing shallower beams where the loads or spans are smaller. This approach would result in moderate savings in materials, but would create additional costs in formwork, resulting in a substantially more expensive structure—quite the opposite effect of that intended. Providing a constant beam depth while varying the amounts of reinforcement along the span length is the simplest and most cost-effective solution.
16.    ABRASIVE RESISTANCE of concrete increases with compressive strength and use of aggregate shall have low abrasion loss under standardized testing or high abrasion resistance
17.    For steel bars to lose one mm diameter due to corrosion, it takes about 12.5 years. For 6mm dia To corrode completely it takes about 75 years in good conditions. But due to practical reasons the number of years reduces due to hostile corrosive environment.  In coastal applications, poor consolidation of concrete, insufficient cover, use of chloride admixtures, 6mm rebar corrode completely in 5 years or less.
 

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

(OP)
asixth,
I think Young's E and high early strength concrete in steam heated curing would be a topic which would require a few pages and I would cover this as a in house training, not a manual, to complex.

Ron,
The reo rate per volume are from Price 2001 I think from memory, I know the slabs and beams  values are good "estimates", have never used the RW value, so I will check against some designs.
 

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

I think you should include also concrete admixture.  

RE: Chapter 4 preliminary design Properties of concrete

(OP)
if by admixtures do you mean water proofing I plan to have a short discription on how to handle.

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

RE...admixtures can include a broad range of things, but most common are air entraining admixture, plasticizers (Super P), water reducing admixture (decrease water,increase slump...but not necessarily a superplasticizer), set retarders, set accelerators, high early strength gain, and probably a few others I'm leaving out.

RE: Chapter 4 preliminary design Properties of concrete

(OP)
I didn't think these had much impact on the engineering properties of concrete. I do have a talk about high early strength, but this is more mix talk, ie cement content and how to understand a mix design ect. Not super P's have not had much experience with spec'ing super P or water reducers ect.

I will have to give this idea more consideration.
 

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

RE....The most significant impact that admixtures have on concrete is usually a positive increase in the ability to consolidate the concrete.  Air entraining admixtures, low and high range water reducing admixtures, and set retarding admixtures all contribute to better consolidation, which provides better durability and more consistent properties of the concrete throughout its cross section.

Ron

RE: Chapter 4 preliminary design Properties of concrete

rowingengineer

I can't see the relevance of point 17 and question your corrosion rate.

If my 6mm bar corroded away in 75 years I wouldn't describe it as 'good conditions'.

RE: Chapter 4 preliminary design Properties of concrete

(OP)
Ron,
Thanks for the input if you don't mind I think I will just add this directly in, maybe with a bit of extra info if I have the time.

apsix,
point 17 is from experience with leaving a reo bar out exposed for a period of time, say if the construction gets delayed ect. I think I may need to reword this a bit, but I do think people need to know just how long you can leave reo/steel unprotected onsite before problems occur.
As for the word good, I will change this, good is not the correct description you are correct. I wanted good "exposed conditions" or similar.

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

It makes more sense now, you just need to add 'exposed to the elements' or similar.
Clarity suffers as the first 2 to 3 sentences are for exposed bar, while the last sentence is clearly about bar cast in concrete.

RE: Chapter 4 preliminary design Properties of concrete

(OP)
Better???
17.    for steel bars exposed to "mild" corrosive environments e.g. constructions sites, for a bar to lose 1 mm diameter due to corrosion, it takes about 12.5 years. For 6mm dia To corrode completely it takes about 75 years. But for practical reasons the number of years reduces in hostile corrosive environment.  

on the other foot; In coastal applications, poor consolidation of concrete, insufficient cover, use of chloride admixtures, 6mm rebar corrode completely in 5 years or less.

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

This thread could really go on forever. It is good that you are producing a standard's manual for graduates and getting things standardized across your company. I am trying hard in my office to start ensuring QA procedures are being followed and updated where necessary. I think your best approach would be to continually monitor this website like you do and update your manual based on questions that are posted. The 'Other Structural Engineering' forum gets a good variety of construction practice questions and technical knowledge question asked by practicing engineers, so an issue a experienced engineer is having it is certainly going to trouble a graduate.

Another good section to include in your manual would be fire requirements. It isn't something that is taught thoroughly in the universities and you don't tend to find too much technical data published in textbooks as it is set by various building regulators. Fire requirements will give the graduate a starting point when sizing column cross-sections and cover.

RE: Chapter 4 preliminary design Properties of concrete

RE...ditto on asixth's comments.  This endeavor will have good return for the graduates.  At the least, it will intice them to question things and give you and other an opportunity for mentoring.  Way to go.

I agree also about the fire resistance. Check a few of the writings by Armand Gustafero...he is/was the fire resistance guru in the US.

RE: Chapter 4 preliminary design Properties of concrete

(OP)
Good suggestions, I have am working through the "rules of thumb" at the moment and will add fire requirements and also if time permits add some generally fire deign. Only problem is at the end of this week I resign and the grade manual stops its development for a while I would imagine, starting a new job probably won't have the time again.

Reason for the manual: I currently have an undergraduate student, he did a thesis in association with our company, and did a great job, and unfortunately it was in wind turbines such won't help him much with the general day to day stuff.  So the reason for the manual comes about because I am leaving this fresh face to an office with one senior engineer whom is has no time. And I would hate for this guy to become only half of what he could.

I am going to post a lot of it in the FAQ now and see i it gets the nod.

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

(OP)
I would take the chance to thank everyone for their input thus far, I have start to post the first chapters in the FAQ, Just thought you would like to know.2thumbsup

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

RE...good job.  All of us with gray hair should be doing the same thing...you've shamed me to get back to writing. My current project is a stucco course.

RE: Chapter 4 preliminary design Properties of concrete

rowingengineer,

Item 6 - reinforcement at the compression face is useless if it is not in compression and not much use until it is significantly in compression (being at the compression face does not put it in compression).

For lightly reinforced slabs and shallow T beams, it is a waste of money. In those cases, extra tension reinforcement is much more useful.

RE: Chapter 4 preliminary design Properties of concrete

(OP)
Ron,
Good to see that a positive impact has occurred, hope the course runs well for you, I always enjoy attending or giving courses. Mind you some of the younger folk are starting to look at me strangely when I go to these courses for inexperienced engineers. I don't think it occurs to them that that I'm not there to learn about the subject (however every now and then I get two or three helpful hints at a time) the reason I am there is to learn about presentation, some guys really set the place alight while others don't.

On another topic, I have no idea what stucco is, did a quick search found a place called NOCSA, and I would suggest they added a photo or two to their website for guys like me. I assume that it is like cement sheeting of some kind, but as they say "assumes make an ass out of u and me".


 

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

(OP)
Rapt,
Thanks for the insight, will have to give this some thought, because I am talking about deflection creep, and while your comments are correct about the efficiency of the slab with regards to Ieff ect which will intern affect deflection, will just need to work out a good clarification note.
Thanks again.

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

RE...stucco is,technically, portland cement plaster.  It is used as a wall surfacing.  Almost universally improperly applied resulting in severe deterioration of wood framing and substrate.

RE: Chapter 4 preliminary design Properties of concrete

(OP)
So kind of like compressed FC (fibre cement sheeting), would be interested to know what problems are associated with this type of product with regards to application.

I really only know of a few problems, if you have a relatively dry atmosphere and very large seasonal temperature variations  the stresses built up in FC sheeting were at times large enough to crack the corners of the sheeting, hence you need joints lots of joints. The other problem I know of is the thermal grade difference if you put it on steel in an external situation, the steel will expand more and crack it up.
 

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

RE...stucco is a "field fabricated" material.  It is essentially 3 coats of mortar (slightly different than typical mortar, but not much) applied in a prescribed manner.  For a wood-framed, sheathed structure, here's the process....

1.  Apply an air infiltration barrier (Tyvek or similar)
2.  Apply a water resistive barrier (Asphalt saturated felt)
3.  Apply a layer of self-furring, galvanized steel lath (diamond mesh is most common) attached only at the structural members.
4.  Apply a 3/8" (9.5mm) thick layer of stucco mortar onto the lath, pushing the material through the lath to create embedment.  Before the layer sets up, scarify the surface in a horizontal direction.  Allow to cure for at least 24 hours, preferably more.  Moist curing is necessary.  This is called the "scratch coat".
5.  Apply another layer of stucco mortar on top of the first coat, again to a thickness of 3/8".  Do not scarify this layer.  This is called the "brown coat" (there's a reason for this name...has to do with differences in the mix proportions for this coat).  Allow to moist cure for 24 hours or more.
5.  Apply a 1/8" thick finish layer.  Texturing may be added on top of the finish layer, but is not included in the total thickness requirement of 7/8".
6.  Paint the surface.

This is a simplified summary...it gets a bit more complicated for joints, wall penetrations such as windows and doors, and at junctions with other materials.

The most common problems we see are improper flashing and waterproofing at the windows (you have to treat the wall as if it were a roof), improper installation and fastening of the lath (usually too much fastening, causing the lath to be too flat against the substrate, thus little embedment), improper installation of accessories such as control joints and weep screeds, improper installation of the stucco layers (insufficient curing time between layers), and improper design/layout of necessary joints.

Volumes have been written about stucco.  It can be a very durable, attractive surfacing for walls.  It can also be a nightmare, particularly when not done properly or bastardized by "synthetic" cure-all materials and procedures (i.e., "one-coat" stucco systems, poorly designed EIFS, etc.).

RE: Chapter 4 preliminary design Properties of concrete

(OP)
Never heard of the stuff before (did a quick Aust search and yes the product is used in Aust), So thanks for the information. I have a feeling that i will run into in the future and thanks to you Ron, I will be better equipped. Hope the presentation goes great.

I would give you a star but apparently one is the limit per thread.

When in doubt, just take the next small step.
 

RE: Chapter 4 preliminary design Properties of concrete

(OP)
Parts of the "rule of thumb" section of the grad manual are posted in the FAQ. 2thumbsup Still have footing, caps and fire (and a few others) to go, but alas I am out of time for now, so this now goes on the back burner until such time I get another grad student.sadeyes

Feel free to comment, suggest amendments ect.

When in doubt, just take the next small step.
 

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