Slump test is a laboratory or at-site test used to measure the consistency of concrete. The slump test shows an indication of the uniformity of concrete in different batches. The shape of the concrete slumps shows the information on the workability and quality of concrete. The characteristics of concrete with respect to the tendency of segregation can be also judged by making a few tamping or blows by tapping a rod on the base plate. This test continues using since 1922 due to the simplicity of apparatus and simple procedure. The shape of the Slump cone shows the workability of 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. It can also be used as an indicator of an improperly mixed batch. The test is popular due to the simplicity of apparatus used and simple procedure. The slump test is used to ensure uniformity for different loads of concrete under field conditions.[rx]
A separate test, known as the flow table, or slump-flow, test, is used for concrete that is too fluid (non-workable) to be measured using the standard slump test because the concrete will not retain its shape when the cone is removed.
The Slump Test is a neural tension test used to detect altered neurodynamics or neural tissue sensitivity. The purpose of this test is to place tension on the dural sheath of the sciatic nerve.
The slump test is described differently among sources. The common factor among sources is the reproduction of pain as tension is applied to the dura during testing. The technique depicted below is adapted from Mark Dutton.
To begin the test, have the patient seated with hands behind back to achieve a neutral spine. The first step is to have the patient slump forward at the thoracic and lumbar spine. If this position does not cause pain, have the patient flex the neck by placing the chin on the chest and then extending one knee as much as possible.
If extending the knee causes pain, have the patient extend the neck into neutral. If the patient is still unable to extend the knee due to pain, the test is considered positive.
If extending the knee does not cause pain, ask the patient to actively dorsiflex the ankle. If dorsiflexion causes pain, have the patient slightly flex the knee while still dorsiflexing. If the pain is reproduced, the test is considered positive. Repeat test on the opposite side. Over-pressure can be applied during any of the test positions.
Apparatus for Slump test
The followings apparatus are used in the slump test of concrete:
- Metallic mold in the shape of a frustum of a cone having bottom diameter 20 cm (8 in), top diameter 10 cm (4 in), and height 30 cm (12in).
- Steel tamping rod having 16 mm (5/8 in) diameter, 0.6 m (2 ft.) long with bullet end.
The patient should be sitting on the edge of the table while the examiner is by the side of the patient.
The slump test consists of several different steps:
- First, the patient slumps forward, rounding the shoulders[rx] so the examiner will then apply pressure to the trunk flexion.
- Next, the patient brings chin to chest and the knee is then actively extended.
- Afterward, the ankle is dorsiflexed. If pain is produced during any of the steps the examiner does not have to continue the test.
The test has several modifications all of which use different sequences of motions that create tension on the dural sheath.[rx]
During the Slump test following steps are followed:
- First of all, the internal surface of the mold is cleaned and free from moisture and free from other old sets of concrete.
- Then place the mold on the smooth horizontal, rigid, and non-absorbant surface.
- The mold is then filled with fresh concrete in four layers with taping each layer 25 times by taping rod, and level the top surface with a trowel.
- Then the mold is slowly pulled in vertical and removed from concrete, so as not to disturb the concrete cone.
- This free concrete deform all the surface to subside due to the effect of gravity.
- That subsidence of concrete in the periphery is a SLUMP of concrete.
- The height difference between the height of subsidence concrete and mold cone in mm is ‘slump value of concrete.
The positive sign is any kind of sciatic pain (radiating, sharp, shooting pain) or reproduction of other neurological symptoms. This indicates impingement of the sciatic nerve, dural lining, spinal cord, or nerve roots.[rx] This test can have a lot of false positives and should be used with another orthopedic test to make the final diagnosis.
Some caution is needed as the diagnostic accuracy of the slump test is under debate! During the slump test,the neural structures within the vertebral canal and foramen are slowly and progressively put on maximum stretch. A recent Cochrane review (on physical examination for lumbar radiculopathy due to disc herniation in patients with low-back pain), also looked at the available data on the Slump test.[rx] The authors listed two studies[rx] that reported results on the slump test. Stankovic et al (1999) present the results of the slump test at different cut-off values (angles at which pain occurred), showing that sensitivity of the slump test was poor (0.44, 95% CI:0.34 to 0.55), and specificity only slightly better (0.58, 95% CI:0.28 to 0.85) when using a strict cut-off (pain radiating below the knee). Sensitivity increased (but specificity decreased) when using a milder cut-off (pain anywhere).[rx] Majlesi et al (2008) reported similar sensitivity (0.84), but higher specificity (0.83), using an unknown cut-off for a positive test result.[rx] So it was not clear when a test was scored as “positive”. Also, the higher specificity might partly be the result of the case-control design of this study: patients with back pain were selected as controls if MRI findings were completely normal.