Foundation, Concrete and Earthquake Engineering

Distressed Slab-On-Grade Foundation Raising by Polyurethane Foam Injection

Many foundations rest on slab that cast directly over ground. In commercial and industrial floors, the distressed slab by sinking, create many problems. It interrupts the functionality of a warehouse floor, when vehicular movement is necessary to enter and exit of goods. 

It also produces aesthetic and hygienic problems to the floor slab. In most industrial floor forklifts are very common to move around the floor. The repair of this slab is also expensive.

A cracked concrete surface

Raising effort of pavement slab sunk at junction with Polyurethane Foam InjectionWe have already discussed about injection method of cement grout for these purpose. Here we will discuss about another injection materials-its polyurethane foam. This type of material is very light weight, have short hardening period, leaving distressed slab to be repaired and serviceable within few minutes, even under the loading of heavy traffic or industrial forklifts.

Now we will discuss about the properties that make polyurethane foam a supreme injection material. We will discuss about setting time of it, in this post. We will finish this topic in the next part, where rest properties will be discussed. Here in some properties we will compare it with conventional mudjacking/slabjacking. You can read our posts on these traditional methods of repairing slab foundations.
Polyurethane Foam Injection provides-‘no excavation’ repair for slab foundation
a. Setting time:
This is important to make slab serviceable within few minutes, in very busy industrial or commercial floors, so that no interruption in shipment of goods or no hamper in regular service in a work station is occurred. Polyurethane foam serves this purpose accurately. Think within few minutes the floor is ready to serve. This is due to the super fast hardening properties of polyurethane foam-this is at most 15 minutes. 
Light Weight:

Now we will have idea about density of usual cement paste and polyurethane foam. The conventional cement grouts have weight around 150 lbs/cft whereas the polyurethane foam have density merely (2-10)lb/cft. As self weight of repair material is less, it produces overburden pressure, to soil beneath, of minimum value. This is also a very important factor to choose this material as repair and raising material.

A bottled 2 lb/cft polyurethane foam
Narrow Injection Holes:

In case of slabjacking the holes drilled to inject grout is around 1.5 inches whereas this foam requires mere 5/8 inch holes. Not only in hole diameter but also the foam have advantage over hole spacing. The injection holes required to penetrate foam is much further than of a slabjacking process.

Handling and Cleaning:

This work is much neater than grout injection. Being finished the injection of foam, the worker can pack up there instruments and materials very quickly i.e. demobilization time is less. Here in this process the cleaning operation for equipment is not required. Thus he work site can be left open for service without interrupting service area.


Polyurethane foam provides good thermal insulation too which produce a repaired area of not susceptible to extreme heat or extreme cold condition.

Moisture Retardation:

A distressed slab foundation to be repaired with polyurethane foam injection
Closed-cell polyurethane results a repaired surface, that restricts or act as barrier to moisture to penetrate through the concrete slabs. This property is particularly important where expansive soil lies beneath pavement or slab.

1 comment:

  1. specialists in structural repairs
    Leaning or bowing walls are just another symptom that your base has been shifted in some very unstable soil. Or soil swell exerts lots of pressure on all the walls to make them lean in toward the center area of your room.