About Concrete

Once you have established a basic understanding of a simple concrete mix you can begin to learn more about new concrete technologies and the true limitations of this incredible building material – hint, there are not many!

By changing the volume and type of aggregates that you use in your cement mix you can create many different types of concrete suited to different applications. In general the goal of substituting aggregates is to have the concrete remain consistently strong as a finished product. Some examples of concrete advanced techniques are:

1) Color or dye in the concrete
2) Lightweight concrete
3) High strength concrete
4) Decorative concrete

Even all of these options are just the tip of the iceberg for what concrete is capable of. The extreme limitations of current concrete technology being researched and developed are transparent (translucent actually) concrete which will show a silhouette through concrete that is meters thick! Limitations of concrete strength is self supporting concrete which does not require the mechanical assistance of steel grid work. Concrete strength used to be measure is PSI however mPa or mega Pascals is the current unit of compressive concrete strength referring to the amount of force the concrete can ensure before failure.

Coloured Concrete
You can add powder or liquid pigments to your concrete to achieve interesting and dynamic colors. Common colors would be brown, red, dark grey, tan and other similar earth tones. To get more vibrant concrete colors you can use pure white Portland cement in place of regular cement, as well as pure white sand instead of regular sand. This white mortar mix will react well to more vibrant colors and pigments. The amount of pigment or dye that you use will depend entirely on the brand that you choose. The best method is to purchase from a specialty concrete supply store which will have a far better selection of quality concrete color additives than your local hardware supply store.

Lightweight Concrete
You can replace all or part of the sand in a 3:1 mortar mix with aggregate materials that are much lighter in nature than sand. The result will be a concrete that is much lighter, but also vastly weaker than a 3:1 sand mortar. There are many applications for lightweight concrete with many of them being decorative such as planter pots or garden statues. The most common lightweight aggregate material substitutions for making concrete are:

Vermiculite – which is a mineral and often sold as “pool base” in larger quantities from pool stores which will make a relatively strong, but compressible concrete. The insulation value of vermiculite is very high, more than ten times as high as sand, so vermiculite concrete mixes are often used for sound dampening and insulating.

Peat Moss – Using peat partially in place of sand will result in a concrete that is much weaker than traditional 3:1 mortar and even much weaker than vermiculite concrete. The texture of the concrete is somewhat earthy and finishing and detail work con be slightly difficult by comparison with other mixes.

Saw Dust – This is another readily available and cheap aggregate substitutions used to achieve a lightweight concrete. In addition to providing a rough and inconsistent texture to the concrete, the wood ingrained will often stain and discolour creating an interesting and unique pattern. Too much sawdust can make the concrete unacceptably weak very quickly – more so than vermiculite and peat moss.

Perlite – This is commonly used for gardening and is recognisable in that it is completely white and very similar in texture to styrofoam beads. The main advantage of this aggregate choice is the fact that it is white. It has a similar overall feel as vermiculite however the concrete produced with vermiculite is much easier to work and finish than concrete made with perlite.

Usually you can replace up to two of your three buckets of sand with an alternative aggregate. Vermiculite can be mixed with straight cement without sand and still remain strong enough to suit several tasks such as swimming pool floors. The other aggregates will yield a concrete that will break under its own weight.

High Strength Concrete
The current strength for concrete is measured in mPa with the average sidewalk concrete being 10-15 mPa where as foundations for homes usually start at 20-25 mPa. High rise commercial concrete is closer to 35 mPa as is swimming pool construction concrete.

The strengthening of concrete over and above what a 3:1 mortar mix will yield requires engineering and testing. If you order concrete from a ready mix or bath plant you can specify precisely how strong you want the concrete to be. If you are mixing it yourself and want to make the concrete as strong as reasonably possible there are a few things that you can do.

Glass Fibres – Glass fibres and fibreglass are two different additives which you can put into your concrete to help make it cohesively stronger as well as minimize hairline cracking in the concrete during the curing process.

Water Reducer – is a liquid that you can put into the concrete in place of water. The water reducer will increase the viscosity and workability of the cement dramatically without affecting the finished strength negatively. The more water that you put in concrete the weaker the finished product will be. In place of water reducer you can also use the absolute minimum water possible to get the concrete workable to make it as strong as possible.

Powder Additives – Combinations of highly dense powders such as silica fume and fly ash can potentially help to make concrete stronger by filling in some of the microscopic spaces left in regular concrete by the larger sized aggregates. These tiny aggregates are dangerous to work with because the airborne particles are small enough to damage your lungs should you breathe them. Most of these powder additives will be hard to locate for the average DIY enthusiast.

Decorative Concrete
In place of sand you can also add just about any other substance such as glass or coloured beads, pieces of plastic or metal, rubber or anything else you can think of. Most commonly you would use this concrete to create an exposed aggregate where loose aggregate is imbedded into the top of partially cured concrete. Exposed aggregate with small coloured stones is very common and you likely have seen this before. Exposed aggregate with marbles and microchips is less common to be sure – but not any less possible.

With some basic practice you can learn to create incredible things such as statues, pool decks, artificial rocks, ponds, waterfalls and decorative art.

Canadian author and second generation swimming pool expert Steve Goodale has written dozens of online tutorials for swimming pool and artificial rock construction, renovation and repair.


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What You Need To Know About Pouring Concrete

Tips for pouring Concrete

Here are tips and instructions on working with concrete. Take the time to read these directions thoroughly; following them can save you time and effort. It can also help you end up with a neater, more satisfactory installation–with far.

  • Determining the Type of Concrete to Use
  • Mixing Your Own Concrete
  • Estimating the Materials Needed
  • Building the Forms for Pouring Concrete
  • Pouring Concrete
  • Reinforcing Concrete
  • Different Ways to Finish Concrete
  • Letting the Concrete Cure



You can use many different types of concrete. Ready-mix concrete, which requires only the addition of water, is the simplest to use. It is ideal for small jobs but can be quite expensive for big projects.

Transit-mix concrete is delivered to the job site in revolving barrel trucks. This is the simplest and easiest way to buy concrete for large projects. However, you’ll be paying for the delivery of the concrete and the convenience of premixing. Check local sources for competitive prices on transit-mix concrete.

You-Haul concrete is available in some areas. You buy the concrete and rent a You-Haul trailer mixer for transporting the concrete to the work site with your car or truck. Again, you have to pay for the premixing and the trailer rental. Check locally for prices on You-Haul concrete.

The least expensive way to purchase concrete for large projects is to buy the dry ingredients and mix them yourself at the job site. Of course, this requires a lot of work, and you must either rent or purchase the necessary mixers and other equipment.

The type of concrete you use will be based on the amount of concrete you need and local prices for the various types.



There are four basic elements in concrete: Portland cement; a fine aggregate, such as sand; a coarse aggregate, such as crushed rock or gravel; and water.

The aggregates (sand and gravel) usually make up from 2/3 to 3/4 of the volume of any finished concrete. All aggregates should be clean and free of organic matter.

The water used for mixing concrete should be clean and free of acids, alkalies, oils and sulfates.

Although the ingredients in concrete are always the same, the finished results depend on the proper mix of the four elements.

The proper mix of ingredients is determined by the intended use of the concrete.

For foundations and retaining walls, use about 6-1/4 gallons of water for each sack of cement if the sand is damp. However, if the sand is wet, 5-1/2 gallons of water will easily do the job.

Concrete that’s mixed for pouring sidewalks, stepping stones, slabs, etc., requires about 5-3/4 gallons of water per sack of cement if the sand is damp and about 5 gallons if the sand is wet.

If you are pouring heavy footings for walls where waterproofing is not a factor, mix the concrete with 1 part cement, 3 parts sand and 4 parts gravel.

For sidewalks, steps, driveways, etc., use 1 part Portland cement, 2 parts sand and 3 parts gravel.

For small jobs, you can measure the ingredients using an ordinary galvanized or plastic pail.

Measure a cubic foot of sand or concrete with a wooden box measuring 12 x 12 x 12 inches.

A wooden box measuring 12″ x 12″ x 12″ can give you an accurate measurement for 1 cubic foot of sand or concrete.

Nail 3/4″ half-round to one side of the box at carefully measured points. This will allow you to measure 1/4, 1/2 and 3/4 of a cubic foot.

Always follow the mixing instructions on the bag when mixing your concrete.



This table shows the number of cubic yards of concrete required to pour slabs of varying sizes and thicknesses.

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Concrete, Making Concrete Work

concrete, in construction, structural material consisting of a hard, chemically inert particulate substance, known as aggregate (usually sand and gravel), that is bonded together by cement and water.

Among the ancient Assyrians and Babylonians, the bonding substance most often used was clay. TheEgyptians developed a substance more closely resembling modern concrete by using lime andgypsum as binders. Lime (calcium oxide), derived from limestone, chalk, or (where available) oyster shells, continued to be the primary pozzolanic, or cement-forming, agent until the early 1800s. In 1824 an English inventor, Joseph Aspdin, burned and ground together a mixture of limestone and clay. This mixture, called portland cement, has remained the dominant cementing agent used in concrete production.

Aggregates are generally designated as either fine (ranging in size from 0.025 to 6.5 mm [0.001 to 0.25 inch]) or coarse (from 6.5 to 38 mm [0.25 to 1.5 inch] or larger). All aggregate materials must be clean and free from admixture with soft particles or vegetable matter, because even small quantities of organic soil compounds result in chemical reactions that seriously affect the strength of the concrete.

Concrete is characterized by the type of aggregate or cement used, by the specific qualities it manifests, or by the methods used to produce it. In ordinary structural concrete, the character of the concrete is largely determined by a water-to-cement ratio. The lower the water content, all else being equal, the stronger the concrete. The mixture must have just enough water to ensure that each aggregate particle is completely surrounded by the cement paste, that the spaces between the aggregate are filled, and that the concrete is liquid enough to be poured and spread effectively. Another durability factor is the amount of cement in relation to the aggregate (expressed as a three-part ratio—cement to fine aggregate to coarse aggregate). Where especially strong concrete is needed, there will be relatively less aggregate.

The strength of concrete is measured in pounds per square inch or kilograms per square centimetre of force needed to crush a sample of a given age or hardness. Concrete’s strength is affected by environmental factors, especially temperature and moisture. If it is allowed to dry prematurely, it can experience unequal tensile stresses that in an imperfectly hardened state cannot be resisted. In the process known as curing, the concrete is kept damp for some time after pouring to slow the shrinkage that occurs as it hardens. Low temperatures also adversely affect its strength. To compensate for this, an additive such as calcium chloride is mixed in with the cement. This accelerates the setting process, which in turn generates heat sufficient to counteract moderately low temperatures. Large concrete forms that cannot be adequately covered are not poured in freezing temperatures.

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