SLABJACKING

SLABJACKING

Slab jacking is a technique for permanently raising a slab, preventing impact loads, correcting defective drainage, and preventing pumping at transverse joints by injecting grout under the slab. When necessary, the grout fills voids beneath the slab, restoring uniform support; it can also be used to lift the slab. Due to the complexity of the task and the specific equipment required, this work must be performed by an experienced contractor.

Need for Slabjacking

Any condition that causes non-uniform slab support, such as embankment settlement, approach slab settlement, settlement over culverts or utility cuts, voids under the pavements, differences in elevation of adjacent pavements, joints in concrete pavements that are moving or expelling water or soil fines, and pavement slabs, should be considered for slabjacking.

Location of Injection Holes

In the field, the location of injection holes must be identified. The jacking crew superintendent usually digs the holes, taking into account the size or length of the raised pavement area, the elevation difference, subgrade and drainage conditions, the position of joints or cracks, and how the slabs will be slanted or lifted. As a general rule, holes should not be less than 12 inches from a transverse joint or slab edge and should not be more than 18 inches away. The holes should be spaced no more than 6 feet apart, with each pumping hole raising no more than 25 to 30 square feet of slab. If the slab is too thick, further holes may be required. If the slab is cracked, additional holes may be required. The location of holes vary depending on the fault that needs to be fixed. A minimum of two holes can be utilised to slab jack a joint if faulting has not yet developed. To avoid elevating the adjacent slab while slab jacking a joint when one corner of the slab has faulted, the hole at the low corner should be set back. A single hole in the centre of the panel may be adequate where the pavement has settled and the slabs are in contact with the sub foundation.

Drilling Holes

Pneumatic drills, core drills, or other instruments capable of drilling grout injection holes through the concrete pavement and the base material drill holes 1-1/4 to 2 inches in diameter. The machinery must be in good working order and must be handled in such a way that the holes are vertical and circular. Down feed pressure should not exceed 200 pounds per square inch, whether applied by hand or mechanically (1,379 kilopascals). If the concrete pavement is too tight against the foundation material, an aeroplane or blow pipe may be required to create a cavity under the slab so that the grout pressure can work. The location where the pavement is laid and glued to a cement-treated or other stable basis. Grout holes should be bored entirely into the base material where the pavement is laid and attached to cement treated or other stabilised base material. Instead of being injected between the pavement and the base material, the grout should be injected below it.

Grout Mixtures

For slabjacking, a number of grout combinations have been effectively used. Three to seven parts fine aggregates or a mixture of aggregate and pozzolans or flyash to one part Portland cement with enough water to achieve the necessary consistency. To improve flowability, wetting agents or other additives can be utilised. The inclusion of a wetting chemical lubricates the grout and allows for runs of up to 6 feet (, as well as a reduction in “pyramiding” (a stiff grout may form a pyramid under the slab, leaving unfilled cavities). To maintain equal consistency, a defined method of proportioning the grout mixture should be utilised. Experience is the best judge of the right consistency to utilise for any given scenario. In most cases, a stiff mix is utilised to raise the pavement slabs, while a more fluid mix is used to fill cavities. A flow fault should be used to ensure consistency, and the hole in the low corner should be set back to avoid rising the adjacent slab. A single hole in the centre of the panel may be adequate where the pavement has settled and the slabs are in contact with the sub foundation.

Grout Pumping

The rate of grout injection should be uniform and as slow as possible, usually a minimum of 1/2 cubic foot (0.014 cubic meter) per minute to a maximum of 2 cubic feet (0.056 cubic meter) per minute. Initial pumping is normally at the lower rate and is increased as lifting progresses.

The grout injection rate should be consistent and as slow as feasible, ranging from 1/2 cubic foot (0.014 cubic metre) per minute to 2 cubic feet (0.056 cubic metre) per minute. Pumping is usually started slowly and gradually increased as the lifting advances. The lifting rate should be reduced as the required elevation is near. Regrouting in new drill holes and more slabjacking will be required if grout is extruded from joints, fissures, or the pavement edge before the goal elevation is attained. Slabjacking gauge pressures typically range from 75 to 200 pounds per square inch, with short pressure surges up to 600 pounds per square inch used to raise bonded slabs.

The most essential single component determining good Slabjacking is constant observation and analysis of pressure behaviour. If pumping continues, a rapid increase could indicate a flow stoppage, which could be followed by a buildup of pressure, excessive lift, and breaking. A drop in pressure without warning could indicate a loss of lift caused by subsurface leaking. When elevating slabs to rectify faulty joints or other elevation discrepancies in slabjacking operations, the temperature is critical. If the temperature is high, the concrete at the slab ends may be compressed and unable to move. To complete the lifting, it may be necessary to cut the joints free.process.

Elevation Control During Jacking

Before slabjacking activities begin, a mechanism for managing the quantity of slablifting and the final elevation of the pavement should be established. A straight edge can be used to fix faulty slabs. A tight stringline is sufficient for minor dips up to 50 feet (18.3 metres) in length, providing the joints are true and plane with those of the neighbouring pavement. An engineer’s level and rod should be used to evaluate the profile well beyond the dip for dips more than 50 feet (18.3 metres). This will prevent the pavement from bulging.

Plugging and Cleanup

After completing slabjacking in a hole and removing the discharge pipe, the hole should be immediately sealed. Tapered wooden plugs are temporarily inserted into the injection hole to keep the grout under pressure and prevent the mixture from flowing back. The temporary plugs are removed once slabjacking to the appropriate elevation is completed, and the injection holes are filled with a stiff one-part water, three-part cement grout or authorised concrete mixture. These portions are then completed to match the existing pavement as closely as possible. Excess grout and other materials should be kept off surfaces near the grouting procedure. To avoid unattractive discoloration and to remove the grout, the grout and cement slurry on the pavement should be broomed and washed off.

If your concrete slab is sinking, it’s extremely likely that it was put over improperly compacted fill earth. Subsurface erosion and soil shrinkage are further causes.You should not have to replace the concrete if you are fortunate enough to have a slabjacker in your region. By pumping a grout mixture or foam beneath your slab, these professionals can raise it back to its previous level. Mud jacking is a term used to describe the process of elevating concrete.They just drill holes in the settled slabs at strategic locations. They fill these holes with the specific mixture using a portable pump and flexible hoses. This method of lifting a slab can generally be completed in a few hours.Frequently, the expense to.

Slab Jacking’s Advantages

This concrete repair can be completed in almost every weather condition. A sturdy foundation is provided by the material injected beneath the slab.There is minimal or no impact on the landscaping.Nothing needs to be moved off the slab because the pump is capable of lifting the slab’s weight as well as anything else you’ve placed on it.Why Do People Use Concrete Sinks?After the foundation construction is completed, fill soil is almost always deposited along the side of the house and garage foundations. This fills in any holes left over from the foundation construction. A function Object { [native code] } will rarely take the trouble to compact this dirt.Soils are made up of solid particles as well as the gaps (voids) between them. However, vacuum gaps in soil can pose serious problems for concrete and buildings.

Soils are made up of solid particles as well as the gaps (voids) between them. Buildings and concrete slabs, on the other hand, can be severely harmed by vacuum areas in the earth. Buildings and slabs, for example, can physically suck air and water out of soils.

Also Check

Most Suitable Material For Construction