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Concrete Cement

 

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Whats the difference between concrete and cement?

I have a small repair job to do on my window ledge and I am not sure if I need concrete or cement to fix it, what is the difference between concrete and cement, I am thinking that cement is a mixture of concrete and sand is that right, also when I watched my uncle mix up some cement several years ago he used a small squirt of washing up liquid in it (the stuff for washing dishes) any ideas why you would need washing up liquid in cement ??

If the repair is filling a crack then the easiest option would be to buy a Grout. You can get ready mixed cement and sand that is specially designed to have low shrink and gap filling properties, this is sometimes referred to as Grout. This option would also save you buying bags of separate sand and cement. You can just follow the instructions on the pack about mixing the grout and then fill the crack with it and smooth it off.
If you are repairing a chip on the edge of the window ledge you might be able to use grout although it could be too runny. You can buy grout in moust hardware stores and builders merchants. If yuo tell someone in the store what it is for they should be able to reccomend a product.

Safest option would be too mix up some mortar and reform the edge. You can use the mortar to fill the cracks too. Mortar is made from a mixture of Cement and building sand. Cement is a very fine grey powder that reacts with water and hardens. Again this can be bought in virtually all hardware stores and builders merchants.

When mixing your mortar always mix the dry ingredients thoroughly first. Use 1 portion cement and 3 portions sand. when you are ready to apply the mortar add some water to the dry mix and stir it. Keep adding water until the mix will hold the shape of a trowel pressed into it without the edges of the trowel shape crumbling (indicates too dry). If the mix is too wet it will not hold the shape of the trowel and water will collect in the indent.

When fixing the edge i would fix a nail or screw in the middle of the chip so that the mortar has something to grip, make sure it isn't long enough to poke out of the surface as this will shorten the life of the repair. While applying the mortar hold a board against the vertical side of the ledge and press the mortar in from the horizontal edge. Slide the board away once the chip is full and smooth off both faces carefully. Protect the mortar from the rain for 24 hours.

As for the difference between concrete and cement -

Concrete is made using cement, aggregate and fines (sand), Essentially mortar with aggregate in it. The aggregate stops the concrete shrinking and cracking this means it can be used for filling large spaces, it also gives the concrete very good compressive strength. This makes concrete sutiable for a huge variety of tasks, just not small repairs to a window ledge.

Cement itself is what makes concrete go hard, it is an ingredient. On its own it is of little use, once hardened it becomes very brittle and has little strength.

Oh and it is true the washing up liquid acts as a plasticiser making the mortar more workable, however the negatives mentioned above are a good reason to use the proper stuff.

Pouring a Concrete or Cement Patio Slab


 

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Drivers Go Into Wet Cement On 87th Street Onramp
A string of more than 10 drivers drove into freshly-laid cement on the northbound onramp to 69 Highway at 87th Street, causing a pair of the vehicles to get stuck and ruin the concrete work.