How to calculate slump in concrete?
- arrow-circle-right A flat metal plate is placed; if not available then a solid, non-absorbent surface can be used, on the floor. ...
- arrow-circle-right Freshly prepared concrete is poured in three stages from the top. ...
- arrow-circle-right On the third and the last stage, the extra concrete is flushed from the top of the mold.
What problems occur if concrete has too low a slump?
What Is Concrete Slump?
- Definition. Slump is a measurement of the workability or consistency of concrete. ...
- Slump and Quality. The lower the amount of water in a traditional concrete mix, the lower its slump. ...
- Slump Testing. Slump is tested with a slump cone. ...
- Warning. Do not use slump level to compare the quality of one mixture of concrete to a different mixture. ...
What concrete slump should I use?
- If concrete is required to be pumped then the slump value of 100 -125 mm is preferred.
- If concrete is directly discharged through the mixer on to the reinforcement then a slump value of 75–100 mm is preferred.
- If the concrete is used for a small work without or with minimal steel reinforcement then a slump of around 75 -90 mm is preferred.
How much slump is needed for the right concrete?
Slump is not design according to grade, rather according to situation where concrete will gonna placed. For heavily reinforced around 150 mm slump is good and for light reinforced section 100–120 mm slump will prove efficient.
What is a good slump for concrete?
Four-inch (4”) slump is very common with normal weight concrete and is a good for pumping. Slumps that are above average will cause reduced strength, durability, and permeability of the concrete. Admixtures should be used instead of water to achieve higher slumps so that you can maintain the quality of your concrete.
Is Higher slump good?
The higher the slump, the more workable or fluid the concrete. Low concrete slump means it's less fluid and has less workability. If the slump of concrete is too low, it won't shape very easily. If it's too high, you run the risk of having the gravel, sand and cement settle out of the mixture, making it unusable.
What does a higher slump mean?
High slump or "flowing" concrete mixes are economical ready mix products that allow maximum flowability without sacrificing strength by adding water at the jobsite. These high slump, high strength properties are attained through the use of high range water reducing admixtures (superplasticizers).
What happens if slump value is too low?
Slump Properties Concrete with a low slump has a high proportion of cement to water that makes it difficult to work with but provides it with greater strength. Each inch of slump that you add to your concrete mixture will decrease the effort required to work it.
What does 5 inch slump mean?
The 4- to 5-inch slump for decorative concrete is a relatively stiff mixture, but not quite as stiff as the 2- to 3-inch slump seen here. A higher slumped concrete is more more fluid and will flow some distance on its own.
What is a 3 slump in concrete?
0:436:103 Concrete Slump - YouTubeYouTubeStart of suggested clipEnd of suggested clipThe first layer fills the mold to a height of two and five-eighths inches. The second layer fillsMoreThe first layer fills the mold to a height of two and five-eighths inches. The second layer fills the mold to six and 1/8 inches and the third layer fills the mold to the top.
What happens when concrete slump is too high?
Increased porosity also results in more efflorescence, causing the color of the surface to be less intense or whitish. Excessive slump also can result from accidentally adding too much water-reducing admixtures or super-plasticizers to a mix. This can result in aggregate segregation and a serious loss of strength.
What does a 6 inch slump mean in concrete?
The 'slump' of concrete refers to the consistency of fresh concrete before it sets – the higher the slump, the more fluid the concrete is.
What does the slump rating mean on concrete?
In other words, it measures how easy the concrete is to push, mold and smooth out. Accordingly, its slump rating indicates what construction application the concrete is good for. The higher the slump, the more workable the concrete. If the slump of concrete is too low, it won't shape very easily. If it is too high, you run the risk ...
What happens if you slump concrete?
If the slump of concrete is too low, it won't shape very easily. If it is too high, you run the risk of having the gravel, sand and cement settle out of the mixture, making it unusable.
How big is a slump cone?
Slump is tested with a slump cone. This is a 12-inch tall, truncated cone open at both the top and the bottom. The top is 4 inches wide and the bottom is 8 inches wide. To test slump, you fill the slump cone to 1/4 of its height and tamp down with 25 strokes of a 3/4-inch steel rod.
What is concrete made of?
Concrete is traditionally made out of a mixture of cement, water, sand and gravel. Modern concrete mixes also add other ingredients such as fibers, plastics and various chemical admixtures. The ingredients and the mixture proportion determine the properties of concrete, including slump. Advertisement.
Can you use slump level to compare concrete?
Do not use slump level to compare the quality of one mixture of concrete to a different mixture. Use it only to compare the quality of different batches of the same mixture. This test does not indicate anything about the strength of the mixture.
Can you determine the quality of concrete from a slump?
The additional ingredients in modern concrete mixes make it impossible to determine concrete quality from slump, however. Concrete with plasticizers and a high slump may actually have less water than a traditional concrete mix with a low slump. Because of these additional ingredients, you can set the slump of a batch of concrete to practically any ...
How many inches are slumps?
Slumps are also determined by ACI standards although we can recommend the following: Reinforced foundation wall and footings: Slump shall be between 2 and 5 inches. Footings, caissons: 1-inch minimum, 4-inch maximum. Slabs, beams, building columns, and reinforced walls: 3-inch minimum and 6-inch maximum.
What strength of concrete should I use for a slab?
Typically, reinforced concrete ranging between 3,500 to 4,000 psi is used on footing and slabs on grade; between 3,500 to 5,000 psi on suspended slabs, beams and girders; and walls and columns normally require between 3,000 to 5,000 psi. When non-reinforced concrete is used different strengths will be required. If you are using it on footings and walls, a concrete strength of 2,500 psi could be enough while between 4,000 to 5,000 psi is needed for pavements. Outdoor concrete used on home improvements should be ordered with a strength ranging from 3,500 to 4,500 psi.
What is slump concrete?
According to the Tennessee Ready Mix Concrete Association, slump is a measurement of concrete’s workability, or fluidity. It’s an indirect measurement of concrete’s quality, states Gabriel Ojeda, president of Fritz-Pak Corp. in Dallas.
What is the difference between a lower slump and a higher slump?
Lower slump concrete is very stiff, and higher slump concrete is more fluid. Most people in the business agree that a typical slump for ordinary decorative concrete applications would be in the 4- to 5-inch range, but there’s no hard-and-fast rule. “The slump should match the application,” says Daczko. “It could be anywhere from 1 ...
What is an admixture in concrete?
Some admixtures make the concrete temporarily more fluid, so colors added to the mix disperse much better . Admixtures can often save the day, Ojeda points out, by increasing the slump without excessive water. They can fix concrete that is not quite what you ordered and they also can fill in when your crew is shorthanded or limited on the number ...
Why use an admixture?
There are any number of reasons why you would use an admixture, all of which have to do with improving characteristics of the concrete. “To ensure the best finished project, contractors should work with their ready-mix supplier to develop a mix design before the concrete is delivered to the job site,” Daczko advises.
Is concrete more permeable?
A higher slumped concrete is more more fluid and will flow some distance on its own. Photo courtesy of MC Magazine, National Precast Concrete Association. “If you use excessive amounts of water, sometimes referred to as ‘water of convenience,’ it makes the concrete a lot more permeable,” Harris says. “It won’t stand up to the test of time in ...
Does decorative concrete need a slump test?
Bob Harris, an industry leader and president of the Decorative Concrete Institute in Temple, Ga., says that although most decorative concrete contractors don’t conduct formal slump tests on the job, that doesn’t make using the proper slump any less important. “They need to understand the correlation [of slump] and how it affects ...
What is the slump test for concrete?
The 6 th edition of the Portland Cement Association’s Design and Control of Concrete Mixtures (1940) stated that the slump test was a rough measure of consistency —a general term meaning fluidity or wetness. It cautioned that: “This test was not an absolute measure of workability and should not be used to compare mixes of wholly different proportions or of different kinds of aggregates. Under conditions of uniform operations, however, changes in consistency as indicated by the slump are useful in indicating changes in the character of the material, the proportions or the water content.” Surprisingly, the recommended slumps for concrete were quite liberal, as follows:
Why is slump important?
Slump is also an important factor in placing structural members such as columns and walls since it affects the ease with which the concrete can be placed and consolidated to minimize honeycomb and bugholes. Thus, it’s in the contractors’ interest to control slump and other properties of fresh concrete.
When was the first ASTM procedure for slump?
It’s a problem with the specification. For many years, after the first ASTM procedure for slump was published in 1922 , concrete specifications included requirements for either a maximum slump or a slump range.
Is Slump a prescriptive specification?
Their belief is that some requirements in prescriptive specifications are not needed. Slump is one of these.
Is slump concrete a reliable indicator?
Care should therefore be taken in relating slump results obtained under field conditions to strength.”. Slump does affect the ease with which concrete can be transported, placed, and screeded, and is a fairly reliable indicator of batch-to-batch variability. That makes it important to contractors who have to place and finish the concrete.
Does concrete slump increase with water?
Under laboratory conditions, with strict control of all concrete materials, the slump is generally found to increase proportionally with the water content of a given concrete mixture, and thus to be inversely related to concrete strength. Under field conditions, however, such a relationship is not clearly and consistently shown.
Is slump a good indicator of hardened concrete?
So slump is no longer a good indicator of hardened concrete quality.
What is S1 slump?
S1 slumps are most likely to be used for kerb and pipework bedding because it’s quite a dry concrete mix. This is sometimes referred to as “semi-dry”. S2 slumps are used for simple strip footings and cast in-situ hard-standing slabs or when using a wheel barrow to move the concrete.
What is concrete workability?
Concrete workability. One of the basic attributes of any concrete is its workability or "consistence", that is, how easy it is to push one way, pull the other, and float to a smooth level surface. Workability is largely determined by how fluid the concrete is. This is referred to as "Slump". Essentially, the more fluid the concrete, the higher ...
What is S3 mix?
This is referred to as a "moist mix" and probably the most useful and most commonly specified consistence. S3 would be used for trench-fill foundations where a high flow is required. This is known as a "wet mix".
Is a slump a measure of water content?
Although slump is often seen as an indication of water content, it is more legitimately interpreted as a measure of consistence. Following the adoption of the new European Standard for Concrete in 2003 (BS8500), consistence (workability or slump) is now specified as being of a particular class.
