Despite arriving in liquid form concrete will harden over time starting on the first day and will continue doing so for days and weeks to come . Buildings made of concrete are among the strongest but unlike a steel or brick building they require time to become strong.
What is concrete? It is a mixture of cement, a coarse material, a finer material and water – and special chemical additives may be added to accommodate ambient temperature, color, etc. Depending on whether it will be used in a building, bridge, road, etc. the mix of material will change. In real estate applications concrete is typically made using cement, coarse grave and sand.
Cement, Coarse gravel and Sand
Concrete comes in liquid form and once it is poured it will take approx. 4 weeks to reach 90% of its design strength. 24 hours for someone to be able to walk in it, 3 days to be able to put serious weight on it (such as columns, bricks or machinery) and 28 days to get to 90% of the designed strength. To increase the strength and rigidity further steel rebars are usually added.
Some considerations when using concrete:
- Within hour after pouring concrete heats up considerably so don’t put anything on it that is susceptible to heat.
- It is not recommended to pore concrete when ambient temperature drops below 35-40 F unless measures are taken such as covering with special blankets or adding additives.
- Keeping concrete moist during the early curing will increase it final strength.
- Concrete settles and CRACKS! If you expect a finished concrete floor to have LESS cracks make saw cuts between (control joints) and around columns (isolation joints) to minimize cracking.
- Concrete turns a lighter color as it dries so make sure you account for that. If you are looking for a specific finish color the best thing is to mix a color dye into the concrete to maximize the chances of getting the final color you seek.
- Concrete in exposed exterior applications such as columns or decks in very humid or cold weather locales will almost definitively rust! In locations near the ocean or where there is salt spray, special varnishes can be applied regularly to prevent rusting.
- Finishing perfectly smooth exterior concrete virtually impossible. But it can be smoothed and painted after curing using a light application of concrete using a trowel and can be improved further if you apply paint.
It is generally believed that concrete has a useful life of 100 years but that could improve with the advent of technology that could preserve it even longer. Comparatively speaking it is a very short lifespan when compared to existing stone buildings that date back to 4800 BC!