Years ago, the only remedy for uneven sidewalks or foundations was what pros in the business call "rip-and-repour," which means tearing out the old pavement slab and pouring a new one—and spending a lot of time and money doing it.
But nowadays, rip-and-repour has been replaced with a process called "mudjacking"—also sometimes called "slabjacking"—a process that was used for years by highway and heavy industry contractors to level cracked, sunken, uneven pavement. The procedure was messy, the equipment loud and cumbersome, and far too expensive for use on domestic sidewalks, stoops, or slab foundations, but now, with better technology and new equipment, mudjacking is a viable alternative to the old rip-and-repour mantra.
Determine Your Need
During almost any new construction, the sheer weight of a newly poured slab of concrete compacts the subsoil underneath and causes it to "settle" until the subsoil is totally compressed. If the soil settles unevenly, leaving large gaps under the slab, the concrete may begin to tilt or sink into the gap below. If the tilt is acute, the slab may slide under another slab, or even crack.
The need for mudjacking is usually easy to spot. If a section of sidewalk or slab foundation has sunk into the ground—and the section hasn't crumbled or disintegrated too much—a specialist begins by drilling a small hole through the slab. After that, a mudlike substance commonly referred to as "slurry" is pumped through the opening and forced into the void under the sunken concrete, raising it to its original position and keeping it there. The hose is retracted, and the hole is filled in with concrete or asphalt. The slurry then solidifies and stabilizes the subsoil, making further sinking unlikely.
It sounds relatively simple, but the process is a lot more complicated than might appear. "Mudjacking is an art of raising sunken concrete to its original height," explains Tim Murray, the owner of Phillipsburg-based Level Right. "Every slab is different, and there isn't a prescribed method of mudjacking. Some [mudjackers] pump lime, grout, cement mortar, topsoil, or clay. It depends on what the individual mudjacker prefers and has experience with."