Mudjacking

Typical Specifications for Pressure Grouting / Mudjacking (Interior Slabs)

SUMMARY

This item shall consist of furnishing all labor, equipment and materials and performing all operations necessary for pressure grouting (mudjacking) or interior labs and includes such items as drilling injection holes, placing material, and monitoring the grouting operation to eliminate damage to the structure from excessive lift.

The amount of grouting required for the project is unknown and will be governed by the conditions encountered as the work progresses. The floor areas to be grouted are indicated on the Contract Drawings.

Pressure grouting shall consist of filling all voids under the existing floor slabs and raising the floor slabs to the required elevations.

QUALIFICATIONS

Work under this section will be accepted only from the contractors meeting the following requirements:

• Ten (10) years of experience performing work on projects of similar size and complexity.

• The ability to provide grout materials specified herein.

• A record of satisfactory completion of at least five (5) projects of similar size and complexity.

SUBMITTALS PRIOR TO EXECUTION OF WORK

Sequence of work.

Description of work tasks and proposed equipment.

Proposed grout mix design including admixtures proposed. The mix design shall address shrinkage or expansive characteristics of the mix.

Method of documentation to record results of the operation including the location of the grout holes, monitoring of the slab displacements, and volume of the grout injected.

MATERIALS

Grout: The grout used in the process shall consist of Portland Cement, non-expansive soil and water, so proportioned as to obtain optimal grout take and penetration at the point of injection and optimum volumetric flow of material. Fly ash may be used in combination with Portland Cement, however, total volume not to exceed 50% of Portland Cement volume. The materials used shall be proportional to produce a minimum compressive strength of 40,000 PSF and a maximum of 120,000 PSF at 28 days.

Cement: Portland Cement shall be Type I and conform to "Specifications of Portland Cement", ASTM Designation C-150. The cement shall be fresh and properly stored.

Soil: Non-expansive loess or loam.

Excluded Materials: Benonite and clays.

EQUIPMENT

Grout Mixer: The mixer shall be high speed colloidal or equivalent capable of producing consistent and homogeneous mixture free of lumps. Enough water shall be added to produce a well-mixed grout having the consistency of a thick cream and permit consistent flow of material under the slab.

Pump: The pump shall be an air-operated, double diaphragm pump or air-operated positive displacement pump capable of delivering variable pressures from 1 to 100 PSI with a pump bypass at 100 PSI and capable of delivering the material in a consistent and uniform manner. The pump shall be capable of producing a minimum flow rate of 80 GPM. Flow volume and cutoff should be able to be controlled at the injection nozzle. The hopper shall be a gravity or open suction and feed screw designed to match the pump requirements.

Drilling: Holes shall be drilled in a diameter of 1 1/2" to 2".

The equipment shall be in good condition and shall be operated in a manner that the holes are not "out-of-round". Holes shall be drilled in a manner to minimize breakout at the bottom of the slab.

CONSTRUCTION METHODS

Primary Injection Points: Primary injection points shall be laid out a maximum 10 foot grid spacing over the area which is to be grouted.

Secondary and Subsequent Injection Points: Secondary and subsequent injection points (if required) shall be located by the "Split-Spacing" method, in which the interval between the grout holes is progressively halved by installing and grouting intermediate holes until the grouting results indicate that a continuous grouted mass has been obtained under the slab. This is to prevent "piering" of material under the slab. Grout procedures that employ a piering method of slab lifting are strictly prohibited.

Sequence of Operation: The sequence of operations as follows below shall be maintained over a given section of the are to be grouted:

Grout at the primary injection points from the periphery of the area inward.

Drill additional holes and grout the secondary injection points if required.

Repeat the grouting to verify the complete distribution of material under the slab until the void is filled and the required degree of vertical displacement (if required) is obtained.

Injection of Grout: Grout shall be injected under a pressure sufficient to properly deliver and place the material. Typical pressure should not exceed 10 PSI in free flow and not exceed 100 PSI in lift. In general, as thick a grout as possible shall be used.

Monitoring Adjacent Facilities:

During grouting, foundation walls, walls and floor slab shall be visually monitored continually during the pumping.

Pumping shall be stopped when excessive quantities of grout return to the slab surface through cracks, joints or adjacent holes. Water displaced from the void structure shall be allowed to flow out freely. Excessive loss of the grout through cracks, joints, or from back pressure in the hose shall not be tolerated. A proprietary effort should be maintained to prevent back pressure "blow outs" and hose failure. Any excessive spillage of grout material is to be immediately cleaned up.

Hole Patching: Upon completion of the pressure grouting, holes shall be sealed flush with the surface of the slab with a sand/cement material and match the surrounding slab in texture.

Raising Slabs: Slabs shall be raised by grouting below the base of the slab to be raised. No effort shall be made to raise a structure until the underlying voids have been satisfactorily filled by pressure grouting. Each point shall be pumped until above a 0.05 foot is rise is noted, at which time the next point shall be grouted, proceeding in this way around the area of the slab so as to raise as nearly uniform as practicable. The grouting pressure shall not exceed 100 PSI during lift. Grouting shall be stopped when either the floor is raised to the required grade or when, in the opinion of the operator, further grouting might damage the structure.

DOCUMENTATION (if required by the Engineer)

The contractor shall document the progress of the work and submit to the Engineer all pertinent results of the operation.

The documents shall show location of injection points relative to building walls, time of start pumping, total amount of grout injected at this point, and remarks concerning blow-outs, uplift or other pertinent information.

PROTECTION AND CLEAN-UP

The contractor shall, as necessary, protect all building components from grout spillage, water or any damage occurring during operations.

The floor shall be thoroughly cleaned upon completion of the grout operations.

QUALITY CONTROL

The owner may engage testing services to perform tests on the grout mix to verify material components, and determine strength and shrinkage characteristics.

In addition, the owner may randomly take core samples through the completed floor slab and sub-base to verify complete coverage of grout and filling voids.

Areas of non-compliance will require re-grouting at no additional expense to the Owner.