CONCRETE DESIGN MIXTURE 1

[DaNiCa]

Hi!
I am a Quantity Surveyor, and I am tired/bored of my routinary daily activities as QS. I am now trying to read some reference online about below topic yet I can't open some site due to security of our company IP. I was not also good during my school days. Hope you find time answering my queries.
I am seeking for your an assistance on what classes & design mix ratios of the following concrete design mix:
1500 psi
2000 psi
2500 psi
3000 psi
3500 psi
4000 psi
5000 psi
6000 psi

Thanks in advance...

 

[dik]

I don't use anything below 3000 psi (20 MPa) and there are different cement types, water cement ratios, admixtures, aggregates, air content, slumps, etc. that will affect the cost. These vary locally and with time... it's best you obtain unit costs for a project at the time of document preparation from local suppliers.

Dik

 

[jgailla]

http://www.ce.memphis.edu/1112/notes/project_2/beam/ACI_mix_design.pdf

This is a good start.

 

[dik]

jgailla...

Good link...

Dik

 

[cvg]

try the Portland Cement Association

http://www.cement.org/cement-concrete-basics

ACI is also good, but may require membership and is costly to purchase the manuals and codes

https://www.concrete.org/

 

[DaNiCa]

Thank you dik, I didn't know that there's a lot of factor to consider in concrete design mixture.

jgailla, that help a lot. I'll be using that on my computation.

cvg, thank you for your response. The site you gave has a wide range of studies, I will read it little by little for me to understand it well.

Your response were related to each step I need to consider. First is the materials, then computation, then supporting studies/document for me to check my ratio. THANK YOU!!!

 

[dik]

For any big concrete project, you pretty much have to get unit rates at the time and in the location... if they have to haul the concrete 20km or 15 miles, it adds up, and if they are hauling it at 60mph or 30mph... also makes a difference.

Dik

 

[DaNiCa]

Hi Dik, does lag of time decreases the strength of concrete? in what way?

 

[Ron]

DaNiCa....get a copy of "Design and Control of Concrete Mixes" from the Portland Cement Association. Even an older edition would be helpful.

As dik notes, there are many considerations to be made in designing, mixing and controlling concrete. The "lag time" you asked about is a function of first introduction of water into the mix. That's when all the chemical processes start and the first 90 to 120 minutes are somewhat critical with initial set of the concrete, depending a lot on temperature. As with any chemical reaction, as temperature increases, the speed of the reaction increases thus causing the concrete to set up quicker. There are a lot of factors that play into this, but this one is fundamental.

 

[DaNiCa]

Thank you Ron, your reply makes it easy for me to understand about this time topic. Now I understand why sometimes our QA Engr & FE refused to accept the rmc from plant. This may be one of their issues.