Breaking up a concrete slab does mandate a certain know-how. Here are the tools you can use, as well as those that might be a tad ambitious for your project. 

Demolishing a Concrete Slab: Why and How

Common Reasons Behind a Demo

• The concrete slab is damaged

• The concrete slab sunk/settled

• It has structural expansion cracks

• You're planning on building a new construction

• It has faulty insulation 

Understanding the Overall Process

Breaking up a concrete slab is a classic case when it comes to renovating existing structures. It’s typically done using one of the three following tools: 

• Sledgehammer

• Breaker hammer 

• Chisel 

The goal is simple: break up the concrete slab and then dispose of the rubble. 

The sledgehammer method is a good tool if you’re planning on breaking up the concrete yourself. Indeed, said method doesn’t require bulky equipment. A sledgehammer, maybe even a digging bar, is plenty to get the job done. However, such tools can’t break apart a thick concrete slab.

The breaker hammer may be the best option if you’re not planning on hiring professionals. However, it’s a bit more complex to use and requires a certain know-how and practice.

An electric or hydraulic chisel is the quickest, most effective, way to get the job done, but it’s also the most expensive. We’ll circle back to said tool in more detail in this article. 

How can you tell if a concrete slab was poorly done?

Cracks 

If you happen to have poured the concrete slab yourself, or hired a contractor lacking the necessary experience, odds are that it's cracked if it was poorly executed.

There are numerous reasons for cracking:

• Too much water was added to the mix

• Improper curing

• It was too cold outside when poured

• Lack of expansion joints

• Concrete’s weak resistance  

If the cracks are active, meaning they continue to expand, having to break up the slab is just a matter of time.  

Uneven

The concrete slab has to be flat and level. By that we mean a flatness of about half an inch (12 cm) high over a 10-foot span (3 m). Beyond said dimensions, measures can be taken to rectify the slab’s uneven characteristics: 

• Sandblasting

• Cutting 

• Self-levelling 

In some cases, especially when working with an old concrete slab (buildings over 50 years), the demolishing route may be best. 

Structural Problems

Believe it or not, the ground, along with the walls, foundation, and floors, is considered a structural component of a building. A problematic concrete slab can quickly lead to structural problems. This means that a weakness can become dangerous and put the building’s structural safety at risk. A concrete slab can be any of the following: 

• Not sturdy enough

• Deeply cracked

• Not sealed (air and water)

• Settling/sagging 

What tools can you use to break up a slab?

How to Manually Break Up Concrete: Hammer and Chisel Combo

A hammer and a chisel might seem like an archaic method to break up concrete. But, the reality is, that those two tools aren’t used to break up the entire concrete slab, but simply to cut around the rebar and electric wires.

If the concrete slab in question has rebar, the hammer and chisel combo will be inefficient. You’ll need to get yourself a grinder.

Sawing Through Rebar: A Crucial Step

Concrete slabs are most often composed of metal rebar. To break up concrete successfully, you need to use the right tools to cut the rebar:

• Bolt cutters

• Pliers

• Concrete grinder

• Reciprocating saw

You’ll need a diamond blade to cut through the rebar in extreme cases. 

When to use a breaker hammer or a hydraulic hammer?

Note that there are different types of breaker hammers: 

• Electric

• Pneumatic

• Thermal

• Gasoline

• Hydraulic

An electric breaker hammer is the standard tool for such a DIY project. It’s relatively lightweight and easy to handle, but not powerful enough to break up a concrete slab. The least amount of power needed to break up a concrete slab with a breaker hammer is between 10 and 20 kilos and 25 joules. 

On the flip side, a hydraulic breaker hammer is a super powerful tool. To be used, it must be plugged into a hydraulic socket. Hence why its use is limited to large-scale projects.  

Soundless, Dustless, and Vibration-Free Demolition Methods

Robot-Assisted Demolition

A demolition robot is a breaker hammer mounted on some sort of tracked vehicle. When in use, roll-over protective structures are deployed and the breaker hammer can commence operation.

If the robot is powered by electricity, the breaker hammer is indeed hydraulic and can easily weigh 200 kilograms. As such, you can proceed to break up a 23-inch (60 cm) thick slab.

Best used indoors, where no CO2 emissions are tolerated, it remains confined to big construction sites, such as residential projects.  

Using a Dicing Saw

A concrete grinder is part of the tools needed to break up concrete. Fitted with a diamond disc, it’s much faster than a chisel and hammer. However, it fails to match the efficiency of an electric chisel or pneumatic breaker hammer. 

Using a concrete grinder is a must when you can’t seem to cut through the concrete’s rebar.

The Pulverizer Method

A concrete pulverizer is a two-ton plier capable of literally pulverizing concrete. To use such sizeable pliers, you need a machine weighing between 18 and 27 tons. Using such a machine to break up a concrete slab yourself would be rather unconventional. 

Furthermore, this type of tool is solely used during the second phase of the demolition process. In other words, when the slab has already been broken into pieces can it then be pulverized.  

Hydrodemolition

Not unlike a concrete pulverizer, hydrodemolition is a tad extreme. Said method calls for using high-pressure water via a robot. We’re talking about 20,000 PSI (pound-force per square inch) for 60 gallons of water per minute, and at full force, 40,000 PSI at 11 gallons/minute.

Naturally, this method doesn’t generate sparks, concrete projections, or vibrations; however, it’s severely oversized to break up a concrete slab in your backyard. And, the only company offering such a service in Quebec is Formax Forage-Sciage.

Chemical Cracking Agent

Also known as a non-explosive and soundless cracking agent; said technique was developed as an answer to explosion-related issues, such as the following: 

• Shock waves

• Concrete projections

• Explosives failing to detonate 

A chemical cracking agent is made of powder materials expanding when mixed with water. To function effectively, holes must be drilled into the concrete, just like you would when inserting explosives. 

It’s then filled with said material and water. The concrete then expands, tumbling down, and simply needing to be picked up afterwards. 

How to Fix a Poorly Made Concrete Slab to Avoid Demolition

If a concrete slab was poorly done, it can be fixed using a levelling compound. The latter can be used to correct ground-level irregularities. It’s super simple to use. It’s nothing but a cement and mortar base compound. It can also be used to coat damaged concrete.

However, levelling has its limits: 1.18 in (3 cm).

If the concrete slab in question has deep-rooted damage, or it was too poorly executed, you should definitely head the demolition route. Hence why it’s best to go through professionals rather than attempting DIY constructions.  

How much does it cost to demolish a concrete slab?

Demolition costs depend on the surface to break up. Plan on spending anywhere between $7 and $22 per square foot. 

A Safe and Effective Demolition

While breaking up a concrete slab might seem like an intimidating practice, it’s a manageable task when done with the right tools and using the proper methods. This guide is meant to streamline the process, providing you with time-tested tips and essential safety guidelines. The importance of planning, choosing the right tools, and complying with safety standards can’t be underestimated. By applying such principles, not only will you be able to break up the concrete effectively, but you’ll also limit the potential risks to your person and environment. In a nutshell, breaking up a concrete slab is a step toward transforming and improving your space, when done competently and prudently.