Known formally as Torre di Pisa (the Tower of Pisa) the region’s most famous piece of architecture has been leaning for hundreds of years. At its worst, the angle was about 5.5 degrees. However, stabilization efforts have reduced it to just about 4 degrees.

How was the lean reduced? Through several methods, none of which was slab jacking. We suspect that slab jacking was not utilized due to the nature and condition of the underlying soil. Keep reading to learn more about that.

200 Years of Construction

Many people do not realize that the Tower of Pisa took nearly 200 years to complete. Construction began in 1173 and was not completed until 1372. You might also not know that the leaning did not start after the structure was complete. It actually started just six years after construction began.

Builders had barely begun work on the seventh floor when they noticed the tower sinking on one side. A subsequent investigation revealed the soil underneath was too unstable. With a foundation of just 3 meters and heavy marble being the primary construction material, the tower was too heavy for the soil.

Constructed was halted for almost 100 years in order to allow the soil to settle. Some believe the tower would have eventually toppled had engineers not taken a break in construction.

Fears of Eventual Collapse

Construction was eventually completed in two more phases. The tower was opened to the public and soon became the centerpiece of the region. Over the next several hundred years, it was used for everything from scientific experiments to religious services. It was also used for military operations.

During World War II, the Germans were suspected of using the tower as an observation point. But because it was so important to Pisa’s architectural history, Allied forces decided not to destroy it. Fast forward to the 1960s and engineers began expressing genuine concern that the tower would fall over.

Shoring It Up

This brings us to how the tower was ultimately saved. Engineers knew they had to do something, or the tower would come down. They first tried attaching tons of counterweights to the high side in order to pull the tower back.

That effort produced limited results and the tower was closed to the public in early 1990. Its bells were also removed to take some of the weight off. Finally, engineers hit on the right solution: they decided to remove soil from the high end of the tower. This not only reduced the tilt to 4 degrees, but it also prevented the tower from leaning any further.

It turned out to be the correct solution for a curious reason: the soft soil is responsible for keeping the tower standing despite numerous earthquakes. The same problematic soil causing the tower to lean was also keeping it erect. This is why slab jacking was determined to be inappropriate. Engineers wanted to keep the soil as-is so as to not increase the chances of future earthquake damage.

In the end, removing soil accomplished the same thing as slab jacking, just in reverse. Rather than filling in voids underneath unstable soil, they created new voids on the other side, thus encouraging the structure to level itself. And now you know.

The post The Curious Case of the Leaning Tower of Pisa appeared first on Concrete Raising Company.

In previous posts we have talked about what causes sinking concrete. This post will deal with cracking. Though the two are often related in real-world settings, they do not have to be. A perfectly level piece of concrete can still crack. Likewise, a concrete slab can sink without cracking.

Compressive Strength vs. Tensile Strength

Concrete is a composite material consisting of fine aggregates, coarse aggregates, binder, and water. A concrete manufacturer might start with sand as the fine aggregate. Gravel is added as the coarse aggregate while Portland cement is the binder. Everything is mixed together with water to create the finished product.

As a composite, concrete is fairly strong. But there is a rub. There are two types of strength we are concerned about when it comes to things like concrete slabs, staircases, and larger structures. The first is compressive strength. The second is tensile strength. Concrete has a very high compressive strength but a comparably low tensile strength.

Compressive strength is the ability to withstand compression, or dead weight if you will. Tensile strength is the ability to withstand the force of being pulled in one direction or another. In the industry, we call this force ‘load’. Tensile strength is measured by putting a material under load and seeing how much force can be applied before it breaks.

More often than not, concrete cracks because its tensile strength is exceeded. Forces pull it in one direction or another until cracks appear. Sometimes, a force that seems to be pushing on the concrete (rather than pulling) results in failure.

Thermal Expansion

Concrete exhibits a comparatively low coefficient of thermal expansion. This is to say that it does not expand or contract a great deal when exposed to environmental conditions. However, expansion and contraction still do occur to some degree. If accommodations are not made to counter it, repeated cycles of expansion and contraction will lead to cracks.

The thermal expansion issue explains why concrete driveways and patio slabs in northern environments crack after just a year or two. The repeated freeze-thaw cycles of winter weather put too much stress on concrete slabs.

Concrete Shrinkage

Finally, all concrete shrinks as it matures. The most shrinkage occurs when concrete is still new and fresh. As it matures, the rate of shrinkage declines. All this is to say that concrete never stops shrinking altogether. Over time, shrinkage can lead to cracking.

The extent to which shrinkage cracking takes place is influenced by a number of factors including the tensile strength of a concrete recipe, the amount of water the concrete retains, the amount of tension it is subject to, and the amount of creep taking place within the slab or structure.

So many influences dictate that is nearly impossible to prevent cracking fully. Even the best concrete jobs are subject to cracking over time. So if you have cracking concrete on your property, don’t sweat it. Cracks are to be expected. Nearly all of them can be fixed without harming the integrity of the structure.

If you are dealing with cracked concrete that is also sinking, feel welcome to contact us. We are Salt Lake City’s specialists in slab repair. We can raise that concrete to its original level and fill in the cracks while we are at it.

The post The Science Behind Cracking Concrete appeared first on Concrete Raising Company.

Concrete slab repair may not seem like such a big deal when compared to replacing a roof or strengthening a weak foundation. In fact, structural repairs certainly are more important. And yet, a cracked or sinking concrete slab still puts downward pressure on the value of your home. It reduces value by creating a negative perception. The simple fact is that people do not like to see broken and sinking concrete. It causes them to worry.

Wondering What Else Might Be Wrong

Home buyers may not know all of the dirty little details about what causes concrete to sink and crack. But they do know enough to understand that there is some underlying issue going on. Seeing a sinking concrete slab during a home showing only causes potential buyers to wonder what else might be wrong with the property. This is obviously something to avoid.

A sinking slab may be nothing more than the result of underlying soil not being properly compacted before the slab was poured. The rest of the house, and its foundation, are in tip-top shape. Yet buyers might suspect something much worse is afoot; they might suspect the entire lot has settling problems.

As you might imagine, a sinking concrete slab can chase buyers away. That goes double for cracks in a foundation or concrete steps. How does this affect the value of your home? Through the simple law of supply and demand.

How Value Is Determined

Did you know that there is no static formula for determining the value of a home? Appraisers and home inspectors know the general guidelines, including the kinds of things that turn buyers off, and they also know how to compare homes against others in the neighborhood. But ultimately, your home is only worth what someone is willing to pay for it.

You could own the biggest and most beautiful mansion in town yet still have a property that is worthless to buyers. Let’s say an appraiser valued your home at $1.5 million. That is a paper value. If you list the home for a year and the best offer you get is $850,000, that is its value. You either take it or you take nothing at all, in which case you hold onto your property.

The Importance of Concrete Slab Repair

This understanding brings us back to the importance of concrete slab repair. If you have a cracked or sinking concrete slab, it is detracting from the value of your home. Reclaim that value by having the slab repaired. Remember that broken concrete gives potential buyers a poor impression of your property. Your goal is to increase the value by improving that perception.

Rest assured you do not have to spend a fortune to repair sinking concrete slabs or steps. The slab jacking process we utilize is fast, effective, and very affordable. Best of all, we can affect most repairs in just a couple of hours or so.

Remember, the true value of your home rests on perception. You can add value to your home by repairing any sinking and cracking concrete – be it slabs, steps, or the foundation. Concrete repairs improve perceptions which, in turn, increase value. It is no more complicated than that.

The post How Concrete Slab Repair Can Add Value to Your Home appeared first on Concrete Raising Company.