Dear Sir,
We all know that the water cement ration 0.45, which may vary due to the Mix-Design. But during the concrete due to changes of weather & materials SSD condition the slump changed (Generally Dropped) in mid time.
So looking the help from experience person, how many water may use for 1mm/5mm slump gaining. The equations also okay, I can check with our mix-design for getting the value.
Thanks in advance for your assistance.
As per IS code standard concrete mix design must have water content as 186 kg per cubic meter (for 20 mm size aggregate) of concrete for a slump of 50 mm. for any increase in slump value of 25 mm water required is 3% of this standard water content. (increasing at the rate of 3 percent for every 25 mm slump). Which means 0.6% for every 5 mm increase or decrease.
Infact the mix which is made at RMC and transported to the work site is either designed for higher slump taking into account the slump loss in the time required for placing of concrete from RMC to destination or superplasticizers are used intermittently during transport.
I advise you to refer IS 10262 which also has example of various type concrete mix designs.
To overcome temperature changes during casting, it is better to use additives that slow down the setting time.
If you want to gain slump without adding more water, the usual practice is to add plasticizer.
if I would like to answer this question with respect to physics the answer is surface tension.
Friction between the aggregate particle (Fine aggregate) increases due to water, and slump increases due to the phenomenon of surface tension.
keep on adding water or more W/C ratio reduces the friction among the particles and then slump collapse.
According to IS 10262:2019, a concrete mix designed for a 50 mm slump (using 20 mm aggregate) should contain 186 kg of water per cubic meter. A 25 mm increase in slump necessitates an additional 3% of the standard water content, equivalent to a 0.6% increase for every 5 mm change in slump. To adjust the slump without increasing water content, using a plasticizer is recommended.
The water undergoes reaction with cement to form C-S-H gel. The reaction is exhothermic which produces heat. The hydration will take place to harden the concrete. The quantity of water to be added depends up on the temperature condition also. Generally w/c ratio varies from 0.6 to 0.40. Higher the grade of concrete will have lesser w/c ratio. But to get workability plastisisers or super plastisisers are added. Thus water and plastisisers affect the slump of concrete.
- Badges
- Science topic