Good Day:
Lets explain concrete mix and how your bricklayer is expected to mix your next foundation / decking.

Most time as Non-Construction experienced house builders, we put our trust on the bricklayers to mix our concrete rightly, however very few of them can be trusted to do the right thing - If your bricklayer negotiated for material and labour (its even more difficult to trust him) because he might be maximizing gain and reducing materials; often times even when you buy your materials; they tend to put in excess sand, granite ratio to minimize time spent in doing the job.

LETS DISCUSS THE BASIC RATIOS AND WHAT IS EXPECTED OF THEM.

We'll start by explaining what the ratio 1:2:4, 1:3:6 etc. means - What this means is the Cement, Fine aggregate and Coarse aggregate ratio. Where fine aggregate could be Sharp Sand or Stone dust and Coarse aggregate could be granite, gravel or stone-base (for certain project types).

1:2:4 therefore means, 1 part of cement : 2 part of fine aggregate : 4 part of coarse aggregate. This 'part' as used refers to volume. It means If I have 1 head-pan of cement, I'll need 2 head-pan of sharp sand and 4 head-pans of granite / gravel or 1 cup of cement, 2 cups and 4 cups respectively of sand and stone.

The above is the theory of the mixture.... but practically on site; their might be need to modify a bit.

Comparing Granite and Gravel:

Granite are basically rocks blasted and keep 'neat' while gravel are rocks that come with a lot of 'dirt' i.e sand. (in my terms) - It means if I have 2 head-pans of granite; I have 2 head-pans of granite but in the case of gravel, if I have 2 head-pans of gravel, what I have is probably 1 head-pan of gravel + 1 head-pan of gravel sand.

The implication is simply:

If I'm working with granite, I can maintain my mix ratios as theory has it but when working with gravel, you are expected to reduce the quantities of sand in it (because gravel itself contains too many sand) so you don't end having too much sand hence the theoretical ratios can't work.

Solution:
The solution to this is by mixing the first bag of cement & aggregate on site and adjusting the quantities accordingly.

Relationship Between Concrete Elements:

CEMENT - SAND - STONE relationship; In practice a 50kg of cement bag contains 2 head pan of cement; this means that if i have a plan to mix 1 bag of cement my mixing ratio would be:

1:2:4 = 1 bag of cement : 4 head-pans of sand : 8 head-pans of stone
1:3:6 = 1 bag of cement : 6 head-pans of sand : 12 head-pans of stone

but must you measure sand and stone in head-pans when you have large quantities to mix?

We have come to conclude also that 4 head-pans = 1 wheel barrow; so for my 1:2:4 mix - I'll have it as 1 bag of cement : 1 wheel barrow of sand : 2 wheel barrow of stone etc.

Over time on site however; you always find the above mix to have too much sand or too much stone....but that doesn't mean the ratios are wrong; IT MEANS OUR MEASUREMENTS ARE NOT ACCURATE - We can only get an accurate mix if we're using a batching plant (off-course not on our little project is this possible)

MY SOLUTION:
I've studied a ratio that works: and that's what I've always recommended on small projects, especially when the Manual Mixers (that mixes half bag at a time) are used.

1:3:3 is that mix.

HALF BAG OF CEMENT : 3 HEAD-PANS OF SAND : 3 HEAD-PANS OF GRANITE and if you're using gravel, you might need to reduce the sand content and increase the stone content to say 1:2:4 etc. mixed with about 30-35 ltrs of water.

Lastly; the other factor that affect this ratio is the size of stone; the smaller the granite size, the more you might need to add eg if I'm using the smallest chippings (1/4) of an Inch; I might need to make my ratio 1:3:4 instead of 1:3:3 to ensure adequate strength.


Lets create a 'healthy discussion' towards ensuring a safe construction practices...


Thanks.


Pics:
1. 1/2 bag Manual Mixer
2. Gravel (It is possible to get 'neat' gravel but most of the ones supplied are local and very dirty with sand here in Lagos)
3. Granite

nice write up

Is the mix same of you are using either gravel or granite

Teewhy2:
Is the mix same of you are using either gravel or granite

with gravel u might need to reduce the sand content because the gravel itself comes with a lot of sand....... it is advised to reduce the sand, try a mix with 1 bag to see how it affects the final concrete and stick to what is thought best for the rest of the mix.

Thanks

slimmdree:
nice write up

Thanks.. Appreciate

saydfact:


with gravel u might need to reduce the sand content because the gravel itself comes with a lot of sand....... it is advised to reduce the sand, try a mix with 1 bag to see how it affects the final concrete and stick to what is thought best for the rest of the mix.

Thanks

What are your thought on washed gravel? Say if left under the rain for a few months. Does I make it neater?

ceelog:


What are your thought on washed gravel? Say if left under the rain for a few months. Does I make it neater?

If you're buying granite - tell them to make sure i has enough stone. If it doesnt, reduce the sand in the mix..

@ DEXTROVERT: this is that article..

saydfact:
@ DEXTROVERT: this is that article..

Thanks boss
But my question is I see angulated rocks pieces not the broken granite used as foundation, I mean rock from which granite is formed, does it have any advantage or disadvantage when used as foundation against mixed cement:sand:granite

DEXTROVERT:


Thanks boss
But my question is I see angulated rocks pieces not the broken granite used as foundation, I mean rock from which granite is formed, does it have any advantage or disadvantage when used as foundation against mixed cement:sand:granite

OK... No you can't use rock for foundation.. The gravel rocks u saw were dug out of the ground... We used them for filling and as hardcore after filling..

Nice write up. Very educating. Please what's the mixing ratio for block making?

loftyone:
Nice write up. Very educating. Please what's the mixing ratio for block making?

Thanks sir,

Sincerely i'm not an expert in block making, its formula or mix - whatever info I give on that wld be googled...... I wld try expanding my knowledge that way soon...

kudos to u @op
this is very educating
may God bless your knowledge

saydfact:


Thanks sir,

Sincerely i'm not an expert in block making, its formula or mix - whatever info I give on that wld be googled...... I wld try expanding my knowledge that way soon...

kudos to u @op
this is very educating
may God bless your knowledge

pls is hand made blocks good or manageable for bungalow building
just trying to reduce cost ni ooo

can a hand made block be stronger than a fabricated block, when the number of blocks moulded in one bag is smaller in quantity, compared to fabricated blocks?

can hand made blocks be used for one storey building house, since there will be pillars and round linted in the. house?

please ur advice on the three questions

thanks in advance

freshpzy1:
pls is hand made blocks good or manageable for bungalow building
just trying to reduce cost ni ooo

can a hand made block be stronger than a fabricated block, when the number of blocks moulded in one bag is smaller in quantity, compared to fabricated blocks?

can hand made blocks be used for one storey building house, since there will be pillars and round linted in the. house?

please ur advice on the three questions

thanks in advance

Morning, Hand made blocks can be stronger than Vibrated blocks if it has a better mix and well done.

Vibrating a block DONT make them strong, using the right cement and sand mixture is what makes a block strong.... whatever method u decide to use, QUALITY and CEMENT/SAND MIX is what you shd monitor.

have u read my other threads in the property section? see my signature. Thanks.

Goodluck...

Nice one op

Julivas:
Nice one op

saydfact:


Morning, Hand made blocks can be stronger than Vibrated blocks if it has a better mix and well done.

Vibrating a block DONT make them strong, using the right cement and sand mixture is what makes a block strong.... whatever method u decide to use, QUALITY and CEMENT/SAND MIX is what you shd monitor.

have u read my other threads in the property section? see my signature. Thanks.

Goodluck...

thank......God bless u

I will keep this in mind

I know one day I will be creating a thread for my building.....thanks

Please how many sqm of floor or spacewill the mix 1:3:3 cover. Thanks.

scrule007:
Please how many sqm of floor or spacewill the mix 1:3:3 cover. Thanks.

Hi, your question is incomplete - what you can rather ask is how many bags of cement is required for xyz(m3) - offcourse 1:3:3 can fill as much as you want...

saydfact:


Hi, your question is incomplete - what you can rather ask is how many bags of cement is required for xyz(m3) - offcourse 1:3:3 can fill as much as you want...

Ok. How many bags for 200m2 .

scrule007:


Ok. How many bags for 200m2 .

200m2 is a lot of SqM - Well thats 135 bags if properly mixed or less if not.

Regards

all my going to site, engineers use 1:5:5 or even 1:6:5 I have barely seen them implement standards. what would you say

Dunamix:
all my going to site, engineers use 1:5:5 or even 1:6:5
I have barely seen them implement standards. what would you say

why do you think building collapse is on the increase? same reason why after a small rain, the fence begin to fall or the plastered walls begin to powder.

The choices are ours....

Block layers are note engineers, no engineer will accept this concrete mix ratio that is not specified by BS code or SCP or even ASTM. Ask the guy who started this thread to give you the targeted strength of this fake concrete mix on 7 and 28 days, whether he will note fumble around. If you need technical knowledge of quantity calculations, then add me on Facebook @ sylva clement. Thanks

This is how we know the quack engineers, they don't following construction specifications

Hello, which Construction and Specification code is backing this mix ratio of 1:3:3?

Clemostica:
Block layers are note engineers, no engineer will accept this concrete mix ratio that is not specified by BS code or SCP or even ASTM. Ask the guy who started this thread to give you the targeted strength of this fake concrete mix on 7 and 28 days, whether he will note fumble around. If you need technical knowledge of quantity calculations, then add me on Facebook @ sylva clement. Thanks

Clemostica:
This is how we know the quack engineers, they don't following construction specifications

Clemostica:
Hello, which Construction and Specification code is backing this mix ratio of 1:3:3?

see pics below; there is a reason why 'your app' allows for that MIX MODIFICATION - its called RESEARCH...... lol

If you read my post well, I started by listing the standards and then going on to explain what my experience on many sites has taught me; kindly share your knowledge here for every1 to learn rather than inviting us to your facebook page....

THANKS


ALSO READ: http://civilengineersforum.com/concrete-mix-ratio/

[quote author=Naslee post=70718816][/quote]

OK... SOON

saydfact:

200m2 is a lot of SqM - Well thats 135 bags if properly mixed or less if not.
Regards

Did you consider the thickness of the slab?

phorget:


Did you consider the thickness of the slab?

afternoon.,, sorry your question isn't clear to me/..kindly ask in full or explain

Please I have three questions, please what quantity of sand, cement and granite/gravel stones will be required
1. To make a pillar that will be between block joining
2. To make lintel on 9 inch block
3. No of cement to lay 100 blocks