Let's take a brief look at this many times.
No this is not a cement grade which is strength related the type relates to the composition of the cement
the main cement types are some 1 2 7 5 and they are usually notated using the Roman numerals I T V Sam
one is your purer cement that has no admixture mixtures at all just the four oxides we discussed previously
seem two is generally a blend that can contain anything that does not contain CBS ground granulated
blast furnace slag Sims 3 is a blend with only GJ CBS some 4 is oppose Atlantic cement and sand 5 is
a composite cement there are also multiple letters that can be attached to each different type and to
make it even worse.
Different countries have different limits over how much cement extenders can be used in each type.
This can get very overwhelming so I always recommend figuring out what you want the concrete to do and
what characteristics you wanted to have and that will give you an idea of what you should be looking
for.
The more important aspect is figuring out what extender if any fits your needs is easily available and
is more economical than perhaps just a stronger portland cement mix that does the exact same thing I'm
a bit worried that I may be losing a few over here so I'll stop there for now and the cement extenders
if you would like me to go deeper into the effects the cement extenders have on fresh and hardened concrete
then head over to the Facebook group and let me know and I'll be happy to add it to the course.
Or to cement ratio the water cement ratio is the one you will most likely spend your time fighting about.
Engineers want a low cement or water ratio to keep the concrete strong whereas the site team wants a
higher water cement ratio to make the concrete more workable on site.
They work around for this is the chemical add mixtures which will cover in a later section but for now
let's consider a few use cases and rules of thumb when looking at masonry mortar or plaster the water
cement ratio is usually between 1 to one point 2.
This is a very wet mix that is highly workable and remember that often these mixes don't need to have
a high strength conventional concrete is generally between zero point four to zero point six percent.
Most of the concrete you will specify will be in this range your internal concrete will be closer to
the zero point six side whereas concrete subject to more extreme conditions will be closer to the zero
point for side.
Concrete was a water cement ratio of around zero point four five is ideal for conditions where you may
have a freeze thaw situation or high sulfate the concrete is more durable and less porous but also less
workable.
Be careful not to overdo the lower water cement ratio.
There is not often a need to specify a zero point four percent ratio on internal concrete.
All it does is make things more difficult for those on site who are placing the concrete anything below
zero point forces zero point two five is in the realm of high performance concrete which gets a little
bit too specialized and project specific to give any real meaningful general guidance on if you ever
come across it.
Make sure whoever is specifying this mix really knows that concrete it's very important okay.
I think that is about enough on cement.
Let's go in a different direction for a bit and consider the aggregates next.