Foundation, Concrete and Earthquake Engineering

What to Do for Grout Losing in Mudjacking for Slab Foundation?

At first we will know about consistency of grout used for mudjacking of foundation. The grout consists of soil-cement and water or soil-cement-lime. In normal cases consistency is adjusted by solid and water ratio. Thinner grout travels over greater area and may escape from work area through bleeding. But thicker grout is restricted to limited area due to its consistency. But in some cases, thicker grout also may escape from the area intended to be grouted to have specific foundation repair to slab foundations. The situations are no or shallow perimeter beam, foundation having concentrated load which have less bearing area like interior fireplace etc. If thicker grout cannot solve the problem then the following methods are undertaken.

a. Stage pumping
Ongoing Mudjacking for a settled pavement slab
This is a method of pumping grout intermittently i.e. grout supplying is stopped after some grout is supplied to provide a period to thicken the grout and sometimes this period may be the time of initial set. This process of stage pumping is used repeatedly. But it should keep in mind that grout must not set in hose and shutdown time is calculated considering this fact.

b. Containment by shoring

In this method sheet piles of plywood or other suitable materials are driven around slab perimeter in to the soil strengthened by suitable bracing. Care should be taken not to escape grout through joints in sheet piling.

c. Underpinning

Underpinning is used to lift slab to support structural loads. The lifted slab up to desired level facilitates mudjacking into soil perimeter without any resistance to flow grouts. We have discussed resistance to mudjacking in the previous post. It is worth mentioning, that raised slab without shoring may result sometimes a way of escaping grout. Considering this situations sometimes sheet piling also associated with underpinning.

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