What's that white powder on my concrete?
The white powdery substance is known as efflorescence. Efflorescene (which means "to flower out" in French) is the result of moisture in the concrete. As the moisture moves through the concrete, it picks up alkaline salts. When the moisture reaches the surface and evaporates, it leaves the salt behind on the surface.
Why does concrete crack?
Cracking of concrete is not unusual. Cracking can be the result of one or a combination of elements, such as thermal contraction, restraint (external or internal) to contracting, subgrade settlement, and applied loads. Cracking can be significantly minimized when the causes are taken into account and preventative steps are applied.
Cracked concrete is often caused by drying shrinkage. The two types of cracks are dynamic (cracks that continue to move and reappear with age) and static (mostly due to shrinkage that can be filled and/or coated). Portland cement has a water to cement ratio of .28 to cure. Water in excess of that needed for hydration, called water of convenience, is only required to make the concrete easier to place, consolidate, and finish. Once the concrete has been placed, finished, and cured, some of the excess water of convenience must escape in order for the slab to meet the manufacturer's moisture emission requirements The loss of water of convenience during the cure of the conrete causes dimensional change - shrinkage - and the shrinkage causes cracks.
All concrete cracks. It's just a matter of where and how much. Lubbock Garage Floors & More receives a lot of calls from distraught homeowners with crumbling concrete jobs. It's crucial to thoroughly check out any concrete contractor and ask for references.
Concrete trivia
- Concrete is a mixure of portland cement, sand, water, and aggregate.
- It can vary in hardness and finishes by batch.
- Concrete is produced at an estimated rate of 7 billion cubic yards per year, and is the second most widely consumed substance on Earth, after water.
- All roads lead to Rome, and 5300 miles of those roads were built from concrete. From 300 B.C. to 476 A.D., the Romans used pozzolana cement from Pozzuoli, Italy, to build the Appian Way, as well as the Roman baths, the Coliseum and Pantheon, and the Pont du Gard aqueduct in southern France.
- The cure rate is temperature-related, but generally:
- The initial set takes 3 to 12 hours.
- The initial cure 3 to 7 days.
- Fundamental full cure 28 days.
- Continues to cure for >> 90 years.
- The older concrete is the harder it becomes.
The above is for informational purposes only. Lubbock Garage Floors & More is a flooring specialist, not a concete contractor.
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