Yes, you can mudjack cracked concrete, but the cracks will need to be repaired once the concrete has been leveled. If the concrete is severely cracked in multiple places, replacement may be a better option, but for less severe cracking, mudjacking is a good solution as long as cracks are correctly caulked and sealed.

A good slump height really depends on the project, but there is a use for nearly all slump levels. For example, low slumps are best in projects that require structure, such as curbs and roads. High slumps often require additional reinforcement, but they flow more freely into hard-to-reach spaces.

Generally speaking, push piers—or steel piers—are the best option for underpinning, as they reach down to solid bedrock to find support for your foundation rather than relying on soil, which could be subject to the same issues as the soil directly below your foundation. However, the best underpinning method for your home depends on your location, how far down the bedrock is, and the type of soil in your area. Helical piers are usually the best option for sandy soil or in areas where the bedrock is too deep to use steel piers.

On average, a mudjacking repair lasts between five and 10 years, though it can sometimes last for well beyond a decade under ideal conditions. Its longevity depends heavily on several factors, including the condition of the underlying soil, environmental conditions like freeze/thaw cycles and erosion, and whether the root cause of the sinking, such as drainage issues, is resolved. Because it doesn't always fix the underlying problem of loose soil, mudjacking is often considered a temporary solution. Proper maintenance and evaluation can help extend its lifespan.