#Concrete slab crack repair methods cracker#
#Concrete slab crack repair methods series#
#Concrete slab crack repair methods crack#

#Concrete slab crack repair methods crack#

Rust has greater volume than steel and the expansion presses against the concrete putting it in tension and causing it to crack and pop off. But if there are chloride ions present, such as from deicing salts, the chloride destroys the 'passivating layer' of alkalinity around the steel, allowing it to rust.

Corrosion of reinforcing steel: Steel rebar is protected inside concrete because the concrete is very alkaline which prevents rust.

Here are a few typical concrete problems and their causes:

#Concrete slab crack repair methods cracker#

Take a saltine cracker and bend down the corner-it breaks in a diagonal line exactly the same as a concrete slab. Look at a diagonal crack across the corner of a slab panel where it was run over by heavy traffic or the subbase was poorly compacted-the bending force created tension across the top of the slab. The concrete was shrinking back in each direction from the corner and that diagonal crack is perpendicular to the direction of shrinkage. Think of a typical shrinkage crack running diagonally from a re-entrant corner in a concrete slab. Recognize that the crack is always perpendicular to the direction of the tension-always! Therefore, a crack implies that the concrete was in tension.

Start by thinking about the basic characteristics of concrete-strong in compression, weak in tension. So we've done our evaluation and now we are ready to determine what caused the damage-this is often called troubleshooting. Watch this easy-to-understand explanation of what causes concrete spalling, from concrete expert Chris Sullivan. Non-destructive evaluation (NDE) techniques include radar, infrared thermography, and impact-echo, and can reveal a lot without having to open up the concrete. Next, you can drill core samples for analysis in the lab or by a petrographer (someone who studies hardened concrete using microscopy). First, break away any damaged concrete to determine how deep the damage goes. If you need more information you might have to resort to some destructive and nondestructive evaluation techniques. Take lots of notes and photos-even video if that would more easily document the problems. Also be sure to have a tape measure to determine the extent of the repairs. Delaminated areas send back a dull hollow sound instead of the hard ringing of sound concrete. Pinging the concrete surface with the hammer will reveal delaminated areas that can be outlined with the paint. Do you have information about the initial construction (mixes, construction drawings, specifications)?ДЄ good tool to have at this point in the investigation is a hammer and some spray paint.For surface delamination, can you define it as thin scaling or deeper spalling or is it an overlay delamination?.Is there damaged (corroded) reinforcing steel?.

Is the damage superficial or does it go deeper into the concrete matrix?.

#Concrete slab crack repair methods series#

If the concrete structure is not in danger of collapse, evaluate it in a series of steps, starting with a simple visual examination: Washington State DOT Ground penetrating radar is used to create an image of the reinforcement inside the concrete. Deteriorated concrete and exposed rebar emphasize the need for immediate repairs.