Which Slump Type Is Best For Construction?

Which Slump Type Is Best For Construction
Concrete slump test – Wikipedia Measurement of Concrete Is called a Slump test For the orthopedic test, see, The concrete slump test measures the consistency of fresh concrete before it sets. It is performed to check the workability of freshly made concrete, and therefore the ease with which concrete flows.

Which type of slump is best for concrete?

Interpretation of results – The slumped concrete takes various shapes and according to the profile of slumped concrete, the slump is termed as true slump, shear slump or collapse slump. If a shear or collapse slump is achieved, a fresh sample should be taken and the test repeated. Only a true slump is of any use in the test. A collapse slump will generally mean that the mix is too wet or that it is a high workability mix, for which the slump test is not appropriate. Very dry mixes having slump 0 – 25 mm are typically used in constructing pavements or roads, low workability mixes having slump 10 – 40 mm are typically used for foundations with light reinforcement, medium workability mixes with slump 50 – 90 mm, are typically used for normal reinforced concrete placed with vibration, high workability concrete with slump > 100 mm is typically used where reinforcing has tight spacing, and/or the concrete has to flow a great distance. : 68 

Collapse Shear True
In a collapse slump the concrete collapses completely. In a shear slump the top portion of the concrete shears off and slips sideways. In a true slump the concrete simply subsides, keeping more or less to shape.

What are the 4 types of slump?

There are three types of slump that may occur in a slumps test, namely, true slump, shear slump and collapse slump. True slump refers to general drop of the concrete mass evenly all around without disintegration. Shear slump indicates that the concrete lacks cohesion. This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T.H. CHU. Advertisements

Is a higher or lower slump better?

Project Superintendent at Baker Concrete Construction, Inc | Leed Green Associate – Published Jan 30, 2019 What does slump equate to? This is a hard question to answer, even among experts. Slump is no longer a good indicator of actual quality. Slump testing was a way to anticipate strength in the mid-1900s.

  • There have been many changes in the construction industry including tying off when working at heights and limiting exposure to silica dust.
  • Unfortunately, acceptance of new information happens slowly.
  • With today’s high-performance mixes that use chemicals, slump testing is not a possible indicator of the water-cement ratio.

Concrete is not regularly tested under field conditions, and the small volume of test samples is not comparable to in place concrete. Slump tests are also very subjective among testing personnel. When different people run a slump test, they come up with variable results.

I have personally tested concrete out of the same wheelbarrow with two other people, and all three of us came up with different results. What level of variance among the people testing is acceptable? This is important to consider as loads are rejected for being one half-inch too high. Concrete test specimens are steadily mishandled and stored inappropriately.

Many testing agencies find it acceptable to store test specimens in a cooler, without maintaining a constant specified temperature. I have personally seen test specimens dropped on the pavement and rolled around in the back of a pickup truck. All these factors affect compressive strength, and this combined with a misunderstanding of slump reduces efficiency in projects.

  1. Contractors are held to high standards while the testing and data are not.
  2. When a load is rejected, it should be rejected by the contractor because it will not work for them.
  3. Higher slump increases the workability of concrete and eases in placement.
  4. The slump is critical when placing columns and walls as it helps the concrete consolidate inside formwork and reduce the number of bug holes and honeycombing.

Slump is also vitally important when placing post-tensioned slabs and beams. A low slump is a root cause for honeycombing in areas around post-tension cables and high concentrations of rebar. Honeycombing in these areas increases the risk of injury and damage during stressing.

  • People get gun-shy about higher slump as it expands the potential for non-compliance reports and rejected loads.
  • Ready-mixed concrete suppliers get preoccupied with this and end up offering a lower quality product to their customers.
  • Contractors pay top dollar for high-performance mixes only to receive a product that does not live up to the well-developed data backing it up.

Job specifications should omit slump requirements and allow contractors to place concrete that meets strength and air requirements. There should be an understanding between suppliers and contractors about the acceptable slump range. Ready-Mixed Concrete Associations are in agreeance that real performance outweighs set job specifications.

How do you choose a slump?

14th September 2017 / in How To / When working with concrete it is essential that you first test the consistency – or concrete slump – of the mix before you lay it, in order to make sure that the concrete is workable and able to set properly. The most popular way we do this is by performing a slump test.

  • This is done by filling a metal cone also known as an Abrams cone) with concrete mix before carefully removing the cone and measuring how much of the concrete stays in place.
  • The concrete slump is determined by calculating the difference between the height of the mould and that of the highest point of specimen.
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If the concrete mix is too wet then it will “slump” down one side and will need to be remixed. This is because concrete is weaker and more susceptible to cracking when the mix is too wet. If it is too dry then there will be no slump at all and you may need to add more water to the mix.

There are four categories of concrete slump, however in order for your concrete to be workable, you need to aim for a true slump. A true slump is where the top of the concrete mass slumps evenly all the way around, however the bulk of the mass stays in one place. If any other result is achieved from the slump test you will have to remix the concrete.

The other results are as follows: Collapse Slump – A collapse slump is exactly how it sounds. If you perform the test and the concrete mass has collapsed completely then this is what’s known as a collapse slump and it means you’ve added to much water. Which Slump Type Is Best For Construction

What is the ideal slump?

WORKABILITY Slump test is used to determine the workability of fresh concrete. Slump test as per IS: 1199 – 1959 is followed.The apparatus used for doing slump test are Slump cone and Tamping rod. Procedure to determine workability of fresh concrete by slump test.

I) The internal surface of the mould is thoroughly cleaned and applied with a light coat of oil. ii) The mould is placed on a smooth, horizontal, rigid and nonabsorbent surface. iii) The mould is then filled in four layers with freshly mixed concrete, each approximately to one-fourth of the height of the mould.

iv) Each layer is tamped 25 times by the rounded end of the tamping rod (strokes are distributed evenly over the cross section). v) After the top layer is rodded, the concrete is struck off the level with a trowel. vi) The mould is removed from the concrete immediately by raising it slowly in the vertical direction. Reporting of Results The slump measured should be recorded in mm of subsidence of the specimen during the test. Any slump specimen, which collapses or shears off laterally gives incorrect result and if this occurs, the test should be repeated with another sample.

  • If, in the repeat test also, the specimen shears, the slump should be measured and the fact that the specimen sheared, should be recorded.
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  • What is the ideal value of slump? Answer 1 In case of a dry sample, slump will be in the range of 25-50 mm that is 1-2 inches.

But in case of a wet concrete, the slump may vary from 150-175 mm or say 6-7 inches. So the value of slump is specifically mentioned along the mix design and thus it should be checked as per your location. Slump depends on many factors like properties of concrete ingredients – aggregates etc.

Also temperature has its effect on slump value. So all these parameters should be kept in mind when deciding the ideal slump Ques 2. How does a superplasticizer effect the slump of concrete? Answer 2 Value of Slump can be increased by the addition of chemical admixtures like mid-range or high-range water reducing agents (super-plasticizers) without changing the water/cement ratio.

Ques 3. How much time one should take to raise the cone? Answer 3 Once the cone is filled and topped off raise the cone within 5-10 seconds. Advertisements Ques 4. What are the dimensions of the cone used in Slump Test? Answer 3 The dimensions are Top Diameter – 10cm Bottom Diameter – 20cm Height – 30cm

Is low slump concrete stronger?

Slump – Slump is the measure of concrete consistency and fluidity. It shows the flow and overall workability of freshly mixed concrete. Simply put, the higher the slump, the wetter the mix. Four-inch (4″) slump is very common with normal weight concrete and is a good for pumping.

What is the maximum slump for concrete?

Title: Concrete Q&A: Slump Requirements per ACI 301 and Roughening of Existing Concrete to 1/4 in. Amplitude per ACI 318 Author(s): Publication: Concrete International Volume: 41 Issue: 5 Appears on pages(s): 72 Keywords: Date: 5/1/2019 Abstract: Q. ACI 301-101 calls for the slump to be proportioned to 2 to 4 in.

50 to 100 mm) prior to a high-range water-reducing admixture (HRWRA) being added and calls for a maximum slump of 8 in. (200 mm) at the point of delivery after the addition of the admixture. How is this handled when a HRWRA is added at the batch plant prior to arriving at the site? Q. When does ACI 318-141 require a 1/4 in.

(6.4 mm) amplitude on existing concrete before new concrete is placed against it?

What is a zero-slump concrete?

According to ACI’s Cement and Concrete Terminology (ACI 116R-90), no-slump concrete is freshly mixed concrete exhibiting a slump of less than 1/4 inch. Zero-slump concrete is defined in the same document, as concrete of stiff or extremely dry consistency showing no measurable slump after removal of the slump cone.

What is the recommended slump for column?

25 to 75 mm is correct.25-100 mm for Beams and Columns.

What happens if slump is too high?

FAQs – What is a concrete slump test? A concrete slump test or slump cone test is used to determine the workability or consistency of concrete mix prepared at the laboratory or the construction site during the progress of the work. A concrete slump test is carried out from batch to batch to check the uniform quality of concrete during construction.

  • To read more about the slump test of concrete, please click here,
  • What are the slump test criteria? If the slump value does not fall into the specified slump range, a check test should be carried out on another portion of the same sample.
  • If the second test fails as well, the concrete is assumed to have failed the project’s requirements, as per standard specification for ready mixed concrete (ASTM C94).
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What does high slump value indicate? High slump value means the water-cement ratio of concrete is high. Hence, both the strength and durability of concrete may get reduced.

How much slump is too much?

Weighing options and making decisions – Your first impulse is probably to place the concrete anyway. This option gets the best productivity from labor and doesn’t strain relations with your ready-mix producer. The risk, however, is that work can both look and be compromised, and the resulting lower durability might force you to remove and replace at some point in the future.

Another solution is to send the load back to the plant and add more portland cement to “dry it up.” Sometimes more aggregate is added as well. But there is unpredictable chemistry between concrete that is starting to hydrate and newly added material. One outcome is that the concrete passes through the initial set phase very quickly, reducing the time you have to complete your work.

If you are stamping patterns in concrete, you may not be able to finish your decorative applications. If one load of concrete is too wet in a sequence of loads, you should reject that load because the results will be significantly different from the others.

If there is more than one load involved in a placement, another option is to spread the load low, placing concrete with the proper slump on top of it. This can work if the concrete still has structural integrity. Your decision about whether to accept or reject concrete also will depend on just how wet the mix is.

Many specifications permit slump variances of 1 inch. If the slump exceeds 1½ inches from what was ordered, reject it.

What is high slump concrete used for?

Home Products & Services Ready-mixed Concrete Flowing Concrete (high slump)

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 is a 3 slump in concrete?

One thing to take into consideration here is the ‘slump’ of the concrete – read on to find out more about what this is and how it affects your work. Concrete slump class.

Class Slump range Target slump
S2 50 – 90 70
S3 100 – 150 130
S4 160 – 210 180
S5 210 – N/A 220

What is high slump and low slump?

What is concrete slump? – Simply put, concrete slump refers to the workability and/or consistency of the concrete mix. Slump can also be described as how fluid the concrete mix is. If it has a higher slump rating, it is more fluid and ‘workable’, and conversely, a lower slump rating means the mix is less fluid and workable. The slump of the concrete mixture is established using a slump test.

What is a 4.5 slump?

Testing Slump in Your Concrete Mix and Why It Is Important How would you define slump? 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.

  1. In Dallas.
  2. And Joe Daczko, group manager of concrete technology for Degussa Inc.
  3. Formerly Master Builders) in Cleveland, maintains it’s a measurement for consistency, both from a quality-control perspective and to determine how fluid or stiff a material is.
  4. However you define it, though, the bottom line remains the same: Slump is a test for the rigidity of uncured concrete.

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 to 10 inches depending on what you’re doing.
  • If you’re paving a road, you need a much stiffer material that can stand on its own.
  • If you’re doing a wall, the flow needs to be much more fluid.” And if you’re pouring a patio, it needs to be somewhere in between.
  • Photo courtesy of Grace Construction Products.

Sizing it up 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.

  1. They need to understand the correlation and how it affects the overall finish and structure of concrete,” he says.
  2. Harris, who teaches concrete techniques across the country and beyond, likes to explain it this way to his students who are just getting started in the business: If you make grape Kool-Aid and it’s too strong, you add water.

The new mixture isn’t as sweet and it’s not as deep a shade of purple. The same holds true for integrally colored concrete: If you change the slump by the addition of excess water, you change the makeup of the entire mixture as well as the intensity of the color.

  • 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.
  • 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 aggressive environments and to things like de-icing salts and certain chemicals that could attack the concrete.” Basically, if you add too much water to your mix, it dilutes the cement paste and weakens the concrete mixture.

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The materials segregate, with the heavier aggregates sinking to the bottom, the sand staying in the middle and the cement floating to the top. “You end up with a cement-poor bottom and a cement-rich surface,” says Ojeda, adding that a weaker surface is prone to cracking due to cement’s inherent shrinking qualities.

There’s a huge difference in adjusting the slump with chemicals rather than with water, Harris continues. By using water-reducing admixtures, you can change the slump without affecting the integrity of the concrete mix. Photo courtesy of Degussa Admixtures.

High-range water reducers, sometimes referred to as superplasticizers, increase the mix’s flow, improve workability, disperse the cement more evenly and allow you to reduce the amount of water in your mix by a certain percentage, making for a more durable product in the long run. It must be kept in mind that they work for a limited amount of time.

The use of admixtures There is a wide range of admixtures that can be used to “fix the mix,” says Ojeda, whose company is well known for its handy Fritz-Paks that can be tossed into the ready-mix truck at the job site, bag and all. Fritz-Pak Corp.’s admixtures are designed to restore loads of concrete that might otherwise be rejected and to improve the performance of problem concrete by modifying its characteristics and enhancing workability.

Photo courtesy of Degussa Admixtures. 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.

“Besides adjusting slump, there are admixtures that can be used to slow down the set of concrete or accelerate it, improve the strength, control cracking, protect against freeze-thaw cycles and add coloring, just to name a few.” Some admixtures make the concrete temporarily more fluid, so colors added to the mix disperse much better.

  1. Admixtures can often save the day, Ojeda points out, by increasing the slump without excessive water.
  2. 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 of stamps.
  3. Using a technique called step retardation, he says, you can discharge half the concrete and retard the other half.

You can start stamping at one end and work from soft to medium to hard before getting to the next section that’s just starting to set. Again, you go from soft to medium to hard to get a consistent pattern. Mike Costello, a regional manager with Dayton Superior, points out that admixtures have been around ever since they first started building concrete dams, but he marvels over the variety available today.

“With the latest admixtures, you can have just about any slump you want. You just decide what you want your concrete to do and you can create a mix design to cause that to happen.” Harris points out that not every job or application requires an admixture. But more contractors should be aware that help is there when they need it.

: Testing Slump in Your Concrete Mix and Why It Is Important

Does higher slump mean higher workability?

The procedure used to determine a slump was first introduced in the early 1920’s. The original ASTM method was used to assess the overall quality of concrete. A higher slump meant it was more flowable, or workable. This workability had a direct correlation to how much water was added to the mix.

  1. Workability equaled more water.
  2. Therefore a higher slump meant a higher water-cement ratio.
  3. This would ultimately lead to lower strengths.
  4. Decades ago, this philosophy was probably true.
  5. However, with innovation and advances in mix designs, now this idea is fundamentally flawed.
  6. Cementitious materials and aggregates can have significant impacts on workability, but at the same time not disrupting the water-cement ratio.

After all, water-cement ratio is what ultimately determines strength, workability does not. Admixtures such as mid-range water reducers and superplasticizers have the ability to reduce water-cement ratio while adding workability (higher slump). We end up with high strength, quality concrete with a higher slump.

What is a 5 slump?

A-5-inch slump in concrete is a collapsed slump which implies excess of water in the concrete above the average normal slump. This type of slump is not acceptable for certain structural concrete works such as beams, columns, slabs and foundations which require a slump of 3 inches.

Which is the weakest concrete?

The weakest mix in the list is 1:5:10 cement :fine aggregate (sand):coarse aggregate (gravel). It has a compressive strength of 5 MPa (725 psi).

What is a 3 slump in concrete?

One thing to take into consideration here is the ‘slump’ of the concrete – read on to find out more about what this is and how it affects your work. Concrete slump class.

Class Slump range Target slump
S2 50 – 90 70
S3 100 – 150 130
S4 160 – 210 180
S5 210 – N/A 220

What is S3 slump concrete?

Concrete @ your Fingertips

Class Slump range Max. allowable deviation on range limit (mm)
S1 10 – 40 0 – 60
S2 50 – 90 30 – 110
S3 100 – 150 80 – 170
S4 160 – 210 140 – 230

What is the recommended slump for column?

25 to 75 mm is correct.25-100 mm for Beams and Columns.

What is the difference between low slump concrete and high slump concrete?

What is concrete slump? – Simply put, concrete slump refers to the workability and/or consistency of the concrete mix. Slump can also be described as how fluid the concrete mix is. If it has a higher slump rating, it is more fluid and ‘workable’, and conversely, a lower slump rating means the mix is less fluid and workable. The slump of the concrete mixture is established using a slump test.