Hydraulic Slump

Equipment Slump cone & pan 5/8” x 24” long bull-nose rod Concrete scoop 12” ruler Bucket & sponge

Preparation Using the sponge, moisten the pan and the inside wall of cone Stand on cone fins

Procedure Using the scoop, carefully place the concrete in the slump cone Fill the cone 1/3 full (by volume)

Procedure Using the rod, rod the concrete 25 strokes; do not strike the bottom Start around the perimeter with the rod slightly inclined and spiral in toward the center

Procedure Continue the procedure for the second and third layers Rod the layers just slightly into the preceding layer. Do not strike the side of the cone.

Procedure Overfill the cone on the last layer. If the level of the concrete drops below the top of the cone, stop rodding, add more concrete and resume the count

Procedure Strike off the excess concrete using the rod as a striker Use a sawing and rolling motion

Procedure Clean the concrete from around the base of the cone While holding the cone in place by the hand-holds, step off of fins and hold cone down with hands

Procedure Lift the cone in a single straight-up motion in 3 to 5 seconds Turn the cone upside down and place it next to the subsided concrete

Procedure Place the rod across the base of the inverted cone. Measure from the bottom of the rod to the displaced center of the concrete Record to the nearest ¼”

How Do We Manage This? The Problem: “Slump Is Always On The Move” “Target” or “Slump Not To Exceed” will be specified by the engineer in the specification.  Ie, 3” plus or minus 1”  Ie, not to exceed 4” Slump decreases with time at varying rates Dependent on many factors including: ◦cement content and characteristics ◦Temperature ◦admixtures that are used Slump loss is particularly a problem when concrete is being transported long distances or if placement is delayed.

Strength is Compromised Result Of Adding Water to the Truck:

Solutions: Some mixing water is held back at the plant and added at the job site as long as:  Addition of water does not exceed specified W/C ratio  Addition of water does not exceed specified slump RULE OF THUMB: One gallon of water per yard of concrete will increase slump one inch READ: “CONCRETE IN PRACTICE: JOBSITE ADDITION OF WATER”

Another Solution: Superplasticizers & Water Reducers Acceptance of superplasticizers allows us to maintain desired water-cement ratios or reduce them while maintaining workability for placement. Use of superplasticizers will also allow placement of concrete at slumps higher than the typical 3" with a lower water- cement ratio. MUST BE APPROVED BY ENGINEER

REMEMBER: Any modifications to the concrete at the jobsite MUST be measured and recorded for quality assurance purposes!