What Cement Should I Use to Cast Concrete With Rubber and Plastic Molds?

When casting concrete into ABS or rubber molds, should you use Portland cement and sand? Premixed bags of concrete? Premixed Bags of Sand Mix? Moulding Plaster? There are two primary rules, and a couple of secondary considerations that will determine what to use. First and foremost, follow the instructions on the product you are using. And be sure to wear protective clothing and equipment as specified by the cement manufacturer.

Mold Thickness and Size Matters - You can use bags of premix "Concrete" or bags of premix "Sand Mix" depending on what thickness you are casting. The main differences are the size of the aggregate in each type. Concrete has larger aggregate or gravel in with the sand and Portland cement, and is designed for castings of two-inches and thicker. These premixed bags of concrete should meet or exceed ASTM C-387 and will yield a compressive strength of 4,000 psi at 28 days, if mixed per instructions. Sand Mix is Portland cement and sand, as the name implies, and is designed for use at half-inch thick and up to two-inch deep mold thickness. Sand Mix used as directed and in accordance with ASTM C-387 yields a compressive strength of 5,000 psi after 28 days.

Where to Use Bags of Sand Mix - Cement tiles and thin brick veneer, which are usually about half-inch thick or thinner are best made with a Sand Mix. Stone veneer under two-inches thick, and most wall plaques would be cast with Sand Mix as well. If the items being made are for an interior application on a vertical surface, such as a brick or tile wall, you may use a plaster instead of Sand Mix. Using plaster would produce a lighter weight tile, brick or stone as well as allowing the use of ready-made wall tile mastic to install them. This comes in buckets, and is readily available in most home supply stores.

It should be noted that a half-inch thick cement tile, paver or brick can handle the weight of vehicular traffic, as in a driveway, if they are installed over a solid concrete base. The same holds true for covering a concrete patio. Stones of a half-inch thick, properly installed with thin-set and or mortar, and made with Sand Mix have a compressive strength of over 5,000 psi. The savings in raw material costs between pouring concrete into a half-inch thick mold, versus a two to three inch thick mold is substantial. So if you are covering a concrete sidewalk, patio or driveway, you may want to consider using a thinner mold.

Where to Use Bags of Concrete Mix - Driveway pavers, stepping stones, thick cast manufactured stone, garden and landscape edging, and anything that is going to end up being thicker than two-inches would require using pre-mixed Concrete-- the stuff with the gravel. The gravel makes it stronger and able to withstand the extra weight these concrete products are expected to handle when installed in a packed sand and gravel installation. A properly prepared base will give you years of service with very little maintenance.

Alternative to Using Bags of Premixed Concrete - For large projects, to save money, and to have more control over your mix design, I recommend using Portland cement, which comes in 94 lb. bags. You will also need bulk sand and/or gravel, additive, concrete color, etc., to make your stones. Or in the case of needing to make batches of light or medium weight stone for walls, you would want to start with Portland cement and a lightweight aggregate like lava rock, Vermiculite, Perlite, expanded shale, or other lightweight aggregate.

When making stone or tile for large projects, or commercially for resale, the savings in raw materials cost will make a big difference in your total cost of the project versus using bags of pre-mixed concrete or Sand Mix. Be aware that there are some negatives though. When designing and mixing your own batches you need to consider that you'll have to purchase bulk sand, and have a place to store it. The same holds true for gravel if the items you are making are thicker than two inches. If you need additional help or advice, there are a variety of mix designs, and other tips and techniques on our Training and Instructions website, as well as hundreds of other free articles relating to the concrete casting industry.

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Electric Cement Mixer Or Gas Powered Cement Mixer

One of the biggest inconveniences when mixing concrete, is running over an electrical cord, with your wheelbarrow, every time that you go to move a load of concrete that you have just mixed. One of the other inconveniences, when using a gas powered cement mixers, is the fact that you need to turn the gas motor off, when you're not using it and restart it, when you are.

Each one of these problems can irritate, the workers who are mixing the concrete. I have talked to people that use cement mixers on a regular basis and have gotten two sides to both stories. What's better than electric cement mixers or a gas powered cement mixers?

It all depends on what you're going to be doing with the cement mixer. If you're not going to be mixing your concrete, near electricity, it wouldn't be a bad idea to purchase a gas powered cement mixer.

If you don't feel like starting and stopping these large concrete mixing devices and you're not interested in going down to the gas station, every time that you run out of fuel, I would recommend that you purchase an electric cement mixer.

The most common cement mixer used by professionals, is a gas powered cement mixer. They have more power usually and seem to have less problems and can be located, anywhere. This makes a big difference, when you're working on large block walls, out in the middle of nowhere.

I own an electric cement mixer and have been happy with it for years. Almost every job that I do, is right next to the house and there is usually an electrical outlet that I can plug into, located conveniently. I also enjoy the fact that I can turn the switch on or off, whenever I'm not mixing concrete. This is one of the most important things to me and would be a determining factor, on my choice, whether to purchase a gas powered cement mixers or an electric powered cement mixers.

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Top Ten Portland Cement Uses

When you decide to begin building your house, one of the most important considerations is about the cement that would be used. In fact, the commonest type of cement to be used across the world is Portland cement. The primary reason for this global general use is indeed its composition. Composed of concrete, mortar, stucco and grout, it is produced as a fine powder by grinding the Portland cement clinker with calcium sulfate. The origins of the cement can be traced back to in the initial years of the 19th century. Portland cement has today found its way as being the basic ingredient for ready-mix concrete. This adoption has been undertaken only after having successfully tested and recognized the fact that it creates a strong bond as compared to the early techniques of concrete production. With the increasing amount of importance that is continuously being attached to them, Portland cement, especially the one which forms a part of the ready-mix concrete, may be put to the following uses-

Uses-

The most important use of Portland cement is the production of concrete. It plays a pivotal role in setting and hardening the concrete. 
On being mixed with other aggregates, Portland cement begins to serve a dual purpose. One, it provides for the concrete products to be workable when wet and Two, it provides them to be durable when dry.
It is extensively used by the retaining walls and the precast concrete block walls as a major component to build a strong foundation of concrete.
By mixing it with water, Portland cement literally turns into a plastic stone and thereby it can be used for purposes and in places where stone was to be used and that too by keeping within the financial limits. 
It may be molded to obtain a hard and fire-proof material which may further be employed in designing buildings, shop floors, reservoirs and other foundations.
Any kind of iron or timber structure is exposed to corrosion either by air or water. But with a concrete casing, made by utilizing Portland cement, they can be effectively protected.
Any structure that is meant to support huge amounts of weight will bring Portland cement into use. These structures range from ground floors of multi-storey buildings to bridge floors and from bridge spans to dams.
Due to its ability to prevent corrosion, it is also put to use in ships, tanks and bunkers.
A blaze or a devastating fire may leave a structure completely burnt but with the use of Portland cement, this can be prevented. 
It is also brought into usage in mortars, plasters, screeds and grouts as a material which can be squeezed into gaps to consolidate the structures.

The use of Portland cements has galvanized ready-mix concrete production. Owing to the prominence which is being attached to them, these cements are said to have already made and left their mark.

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Cement Mixer Advice and Tips

The art of constructing buildings and making streets and sidewalks has been width us since the days of the Egyptians. While the technology used today to make concrete has certainly changed for the better, the Egyptians, Greeks, Romans used baking ovens where they mixed clay with straw and other earthen material to formulate material that was later used for construction. Today's concrete and cement mixers look so much different than their earlier counterparts. When you talk of cement mixers, most people envision the huge cement rotating drums that are mounted on large construction trucks that speed to and fro construction sites.

Sometimes, cement mixers trucks are also known as concrete mixer trucks. While cement and concrete are actually different, people refer to them interchangeably. Cement mixers use specialized technology that mixes sand, gravel, water and some chemicals to form cement which is a gooey substance that is used to make sidewalks and road paths.

These mixers are very convenient. In the past, people used to mix the concrete and cement themselves and this was not always very efficient because it was slow. The hand mixed cement mixers did not always do a good job. This was because of the time element and the composition element. The cement was then packed into wheel barrows then ferried to the construction site. But cement mixers have changed all this and are a much better option. They save time and encourage efficiency because the cement can be processed and mixed at the same time while the truck is on the way to the construction site.

Cement began being part of road construction in the 1800s and all this was brought about by the motor revolution which caused many cars to be manufactured. Then in the 1920s automobiles became more widespread and so did concrete mixers.

In the 1970s, there were some concerns raised by environmentalists regarding cement mixers and there were technological modifications made in order to ensure that the cement mixers were environment. Today, the cement mixers, use safer materials, emit less toxins, are skid resistant and are also more or less weather resistant. The 18-wheeler trucks have also been modified to support cement and transportation of that cement to and fro the construction site.

Today, over 90% of the roads in the United States are constructed using cement. Cement mixer trucks can be bought from the regular car dealers that sell ordinary cars. Companies like Ford, Fiat, Mercedes Benz all have truck divisions which sell cement mixer trucks. If you wanted to purchase a cement mixer truck you also might want to look online. If your budget is shoe-string then the best place to look for a cement mixer truck is online where someone may be selling a used truck. eBay also stocks good deals when it comes to cement trucks and the price is also affordable because eBay allows buyers to bid on the products.

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