Which cement for slab

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firearm12

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Hello friends,

Need an advise. we are going to cast slab for second floor in my house. there are many special water repellent cements in market (acc gold, Ambuja plus etc) which are little costly and as per companies are better for slabs. so it’s becoming a question of confusion whether we should go with normal cement + waterproofing chemical or use these special water repellent cements for roof slab. the question is that if a cement is water repellent then how will curing occur properly. Please advise if some has any personal experience with these cements And what approach will be better. thanks.
 

arj

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Hi Firearm12 , I dont know much about cements but considering this is a house which is really long term+ Safety considerations, better to go for something known even if there is a warranty .
While if it was a tech product I would have risked the new product, but for a house I personally would go for the tried and tested ie regular + additive
 

sanjivnayak

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Ambuja Plus or ACC Gold are their premium range of cement. Normally quantity of cement present in a certain volume of concrete (unit is cubic meter or cum ) determines the strength of concrete. Concrete is a mixer of cement, sand and aggregates added with water. The proportion of each of these components affect the strength of concrete. If the proportion of cement is more then strength is more. For roof slab M25 or higher grade RCC is suggested. The proper mixing of concrete , placement, curing required to achieve the desired strength. A higher grade concrete is dense, has more strength and water proof. But to achieve it is difficult due to various factors other than quality of cement. So we always find our slab is leaking. For which we go for a waterproofing of the slab by adding water proofing compound to concrete and lay an extra layer of waterproof compound over the slab.
 

firearm12

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Hi Firearm12 , I dont know much about cements but considering this is a house which is really long term+ Safety considerations, better to go for something known even if there is a warranty .
While if it was a tech product I would have risked the new product, but for a house I personally would go for the tried and tested ie regular + additive
That’s what i was thinking also, but contractor constantly trying to convince for new special cements. I watched a lot of YouTube videos also since last few days but not able to convince myself. So I thought maybe someone from civil engineering background in this forum might be able to give a better picture. only have time to think until tomorrow.

Ambuja Plus or ACC Gold are their premium range of cement. Normally quantity of cement present in a certain volume of concrete (unit is cubic meter or cum ) determines the strength of concrete. Concrete is a mixer of cement, sand and aggregates added with water. The proportion of each of these components affect the strength of concrete. If the proportion of cement is more then strength is more. For roof slab M25 or higher grade RCC is suggested. The proper mixing of concrete , placement, curing required to achieve the desired strength. A higher grade concrete is dense, has more strength and water proof. But to achieve it is difficult due to various factors other than quality of cement. So we always find our slab is leaking. For which we go for a waterproofing of the slab by adding water proofing compound to concrete and lay an extra layer of waterproof compound over the slab.

yes you are right but the water repellant properties of these new cements is what is confusing. One finds many demos on YouTube where they show that these cements don’t absorb any water. I only know that water is required for hydration of cement and if cement itself repels water, how it will hydrate.
 

sanjivnayak

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Hydration is a process which starts when we add water to cement which produces heat and the reaction continues for several weeks. Water added to cement during casting is enough for the reaction to occur. But due to exposure of concrete to air good amount of water evaporates for which we have to supplement water. concrete gains substantial strength by 28days. Concrete becomes fully waterproof by 28 days.
 

firearm12

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Hydration is a process which starts when we add water to cement which produces heat and the reaction continues for several weeks. Water added to cement during casting is enough for the reaction to occur. But due to exposure of concrete to air good amount of water evaporates for which we have to supplement water. concrete gains substantial strength by 28days. Concrete becomes fully waterproof by 28 days.
Ok so it seems its safe using these cements. Thanks.
 

rrunner

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Waterproofing chemical is a must for slab especially top floor terrace and water tank area. water "repellent" cement may be good for external plastering purposes. In my experience no matter what cement you use for the slab if there is an open joint on roof tiles/cement screed or crack water will seep through, so waterproofing is a must.
 

Sushant Sharma

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In the middle of it myself but just completed foundation and moving to plinth beams now. I only know of PPC and OPC cement.
The latter is used in high rise buildings and bridges etc because of much lesser time required for curing and is slightly more expensive. I am using PPC in M25 ratio. Just to add my experience with this is also limited to about 6 months. Are you referring to a third kind of cement?
 
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firearm12

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In the middle of it myself but just completed foundation and moving to plinth beams now. I only know of PPC and OPC cement.
The latter is used in high rise buildings and bridges etc because of much lesser time required for curing and is slightly more expensive. I am using PPC in M25 ratio. Just to add my experience with this is also limited to about 6 months. Are you referring to a third kind of cement?

Yes and no, from what i know its basically an opc cement thats mixed with some hydrophobic polymers that helps keeping water away. Most companies sell it and say its specially made for slabs and even plastering and helps waterproofing. e.g. ambuja plus roof special, acc gold, ultratech weather plus etc. Its costly (around 50rs more than normal ppc)
 

Sushant Sharma

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As suggested earlier by sanjivnaik, "The proper mixing of concrete , placement, curing required to achieve the desired strength. waterproofing of the slab by adding water proofing compound". I have only been worrying about doing this properly.
 

sanjivnayak

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As suggested earlier by sanjivnaik, "The proper mixing of concrete , placement, curing required to achieve the desired strength. waterproofing of the slab by adding water proofing compound". I have only been worrying about doing this properly.
In case you are using this Ambuja Plus type of special cement then water proofing compound may not be added to cement. But care should be taken that concrete grade is M25 minimum. In case you are using ready mix then procure from a known firm otherwise it is under your control. Waterproofing of top slab may be done by engaging professionals. A top screed is done over the waterproofing treatment for not getting damaged and the screed also helps in maintaining required slope towards rainwater pipes.
 

hannibal09

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What's your location. Concrete doesn't required waterproofing compound if shrinkage cracks are avoided. Depending on your location and heat, curing of concrete is most important. After curing period is over, get acrylic based waterproofing compound coating done. Thereafter install tiles with groove and fill those grooves with epoxy based compounds.
Also ensure to maintain slope towards downtake pipe to avoid collection of water at terrace.

Further garde of cement also matters regarding shrinkage cracks. Better to use 43 grade instead of 53. Also minimum nominal mix concrete of M25 or as per design.
 

Vivek Batra

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Since this thread is still hot, should I consider higher grade cement for constructing basement. I am quite worried about waterproofing of all the walls and floor of the basement.

Thanks
Vivek
 

hannibal09

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Since this thread is still hot, should I consider higher grade cement for constructing basement. I am quite worried about waterproofing of all the walls and floor of the basement.

Thanks
Vivek
Basement is always tricky as when leakage starts you can not repair from positive side and always rely on negative side.
For basement points to be consider
1. Ground water level
2. Is your basement on rock where stream forms from rain water
3. What's the ground floor finish around basement, to know how much rainwater will percolate
4. Do you have garden near basement.

Once you know how much water pressure your basement going to withstand, you can plan waterproofing accordingly.
Regarding grade of cement, there is 33, 43 & 53 ordinary portland cement(OPC) and Portland pozzolana Cement(PPC). For home construction, you should avoid using PPC. Regardless of cement grade, concrete grade matter like M25, M30 etc. As you use higher grade cement, content of cement reduces in producing same grade concrete.
Concrete hardening process requires water and higher the grade, higher the requirement. Therefore lower garde cement is advised to control shrinkage cracks. Cement 43 is ideal considering strength and curing requirements.
 

Vivek Batra

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Basement is always tricky as when leakage starts you can not repair from positive side and always rely on negative side.
For basement points to be consider
1. Ground water level
2. Is your basement on rock where stream forms from rain water
3. What's the ground floor finish around basement, to know how much rainwater will percolate
4. Do you have garden near basement.

Once you know how much water pressure your basement going to withstand, you can plan waterproofing accordingly.
Regarding grade of cement, there is 33, 43 & 53 ordinary portland cement(OPC) and Portland pozzolana Cement(PPC). For home construction, you should avoid using PPC. Regardless of cement grade, concrete grade matter like M25, M30 etc. As you use higher grade cement, content of cement reduces in producing same grade concrete.
Concrete hardening process requires water and higher the grade, higher the requirement. Therefore lower garde cement is advised to control shrinkage cracks. Cement 43 is ideal considering strength and curing requirements.
That's helpful, I will try to follow the ideal method of waterproofing from positive side.
 

sanjivnayak

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Waterproofing on outerside wall is required as water infiltration should be stopped at the source. Basement wall and flooring should be RCC with drainage facility and pumping facility. After observation in rainy season necessary grouting if necessary may be done.
 

Vivek Batra

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Reading all the stuff about basements and mositure issues, I am getting nervous :( and thinking about moving to second floor for my dedicated room.
 

sanjivnayak

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Reading all the stuff about basements and mositure issues, I am getting nervous :( and thinking about moving to second floor for my dedicated room.
National building code prohibits basement usage as residential purposes. Only commercial, parking, storage, machinery set up etc are allowed. And I am not sure if basement can be used for Home Bar. So pls check and in case it is allowed, make a sophisticated wine bar rather than a hometheatre in your basement.
 

Vivek Batra

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National building code prohibits basement usage as residential purposes. Only commercial, parking, storage, machinery set up etc are allowed. And I am not sure if basement can be used for Home Bar. So pls check and in case it is allowed, make a sophisticated wine bar rather than a hometheatre in your basement.
Bar is planned as well ;) , I have seen even swimming pools in basement in my city
 
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