Friday, August 7, 2015

The art of mixing cement

Welcome to our blog, Menfranco general blog
and this post, the art of mixing cement

This is an average mixer used on the building sites, it saves a lot of hard work, if we compare it to the times when everything was mixed by hand. Anyhow in this post we are talking about how to use it and how to go about mixing by hand.

The art of mixing cement

Learn to recognize and use the building materials when we use to mix cement; 

Now, that we have written what are the building materials you need to make many cement things, we have also explained above how to mix concrete by hand and other things, this procedure could also be applied to mix mortar and plaster etc. We have also explained how you could recognize the raw building materials; then we have taken you through with this procedure of how to mix concrete the old ways; and we believe that it can still be useful today, if you happen to be far away from anywhere that can supply ready mixed concrete.

You see, let us just imagine that you happen to need concrete, you live in the middle of nowhere and you have only a few tools, but you now a faraway place where you can go and buy some Portland cement; you are not going to buy anything else at that place, because it is too far and therefore too costly to bring it in, so the rest of the concrete materials you are going to find near the river banks. I know it is like going back in time a hundred years ago, but there are some part of the world that are still that far back and perhaps even more. Therefore learning how to recognize the basic building materials for making concrete, and then mixing concrete by hand can still be useful today.

In this article we are going to continue to describe most of the procedures that we have used during our lives when we were/are building with cement and we will do that in a few different ways, so that a record in writing exists for anyone that wishes to have an idea what it is all about. So we are going to add many articles every now and then hoping to be able to help any would be do it yourself small owner builders.

Now, we have to add that what we are writing here is only how we have done these things, and we know they work, however it is only our view and they work well in all minor jobs, but if you have important work, you should consult the local experts.

Now let us see how we should mix concrete with a mixer. 


Mixing concrete with a mixer

Now that we have seen how concrete was made the very old ways, let us see how concrete can be made using a mixer, and what the differences in the procedure are.

Okay, let us make this clear, there may be several ways how to mix you own concrete; you can mix it on the ground as we have done in one of the above description, you can mix concrete in a wheelbarrow, if you have a modern wheelbarrow with a good tray, or you can mix it with a mixer which would be very helpful to have, but what are the different procedures when you mix, in order to achieve the best result with the least amount of time and work:

The greatest difference for mixing concrete and also other cement materials is mainly this: when you mix by hand you can achieve the best result by mixing the materials with the cement before you add water, as this helps to make a more even mixture quicker: But when you use the mixer you don’t need to do that, in fact you can have better and quicker result by following this procedure here under:

Start the mixer and put in the mixer some water, approximately the proper amount to mix the whole batch, you know how much water to use once you have made a few batches. (Let us explain first)

Now before we proceed to mix, let us talk about the water amount, on building sites and in most other places, it is near impossible to tell you how much water you need exactly to start with, due to the fact that the material you are using contains an unknown quantity of water themselves, and therefore the quantity of water varies, you see the wetter the materials are, the less water you need and vice verse if they are dry.  

Now, let us assume that because you are new at doing this you are using a dry small bucket to measure the quantities of the building materials; in this case you have gravel and river sand in separate heaps, you know that this concrete is going to be mixed 6 to 1, but overall this batch you are going to mix 8 small buckets of gravel four of river sand and two of Portland cement:

Now the quantities above is how the best and strongest cement can be achieved, with a minimum of Portland cement used, as these are the quantities that would very likely be written in the specifications, if you have any specification written, and perhaps the ready mix people would use those amounts and have a perfect concrete, because the concrete mixer will mix it well and as dry as possible, just look at one of the photos that we have in this article to see what I mean.  But by experience on building sites usually we would be using a bit more river sand and a bit less gravel, as this makes it easier to work with overall.

But let me explain, the strongest cement is achieved by using the least amount of sand and water; however this sometimes becomes hard for the tradesman on site to use properly, since it is harder for him to compact it to the stage where there are no air bubble in it, unless he uses a vibrator, therefore the extra strength in the concrete could easily be lost and also to finish the top layer smooth becomes harder, because the concrete does not flow easily in place and there is not enough fine stuff at the top to finish it.

Now let us go back to mix our concrete:  

So, after you have poured the water into the mixer, you put one single bucket of gravel and while the mixer turns put the two small bucket of cement into the mixer, the cement in the mixer will immediately mix in the water and the first bucket of gravel will make sure that it does not stick to the mixer, because it will cut though any lumps easily, now you add four buckets of river sand, and this again will mix very quickly and become like a thick cream, all you have to do next is to add the other seven bucket of gravel, once you have done that you only need to wait a little bit for the mixer to mix it properly and your concrete is ready. Now all you have to do is to tip your concrete in a wheelbarrow and take it to the place you need to concrete.

This is the quickest and best way to mix concrete in a mixer, as I have done it for thousands of times, but I need to say also that on building sites, where there is plenty of cement to mix and the workers have to try not to injury themselves, by lifting hundreds of bucket full of material all day long, they use to measure the materials by the shovelful, but you have to be an expert at doing that and get everything measured right.

I hope this description of how to mix concrete is clear enough for our readers to understand what we have described.

Before we leave this concrete discussions we would like to add a bit more information; you see concrete in itself is very strong in compression, but is lacks some strength under tension, so to make concrete very strong and last a very long time you need to use steel in the concrete; here is a link that will help to understand some of these issues.

 How to Make Concrete Even Stronger: 6 Steps (with Pictures)


And now let us talk about, mixing mortar, plaster or cement topping.


Mixing mortar, plaster or cement topping.

Now that we have described how to mix concrete by hand the old ways and also by using a mixer, the same ways can be used to mix mortar and/or hard plaster or cement topping etc. So now, we do not need to explain step by step how to mix them, but we will just describe only the different amount of things that are used; but try to remember that when you mix by hand, it is a lot easier to mix the dry materials first and then add water, but when you use the mixer it usually is better and quicker to start with the water first.

To mix mortar for the bricklayer;

Just by using brickies loams and Portland cement, this mixture by volume is most likely 4 part brickies loams to one part Portland cement, but it could vary from (3 to 1) to (6 to 1) the aim here is to give the bricklayers what is easy to work with, and at the same time you don’t want to make the mortar a lot stronger than the bricks when it dries, and you don’t want to make it too weak for the job you are doing, so it would make sense to see what the bricklayer reckons is good enough for the job; sometimes when making mortar you can replace part of the Portland cement with hydrated lime, plus other things to make the mortar easy to work with.

Mortar for cement blocks

The mortar for cement block is usually three parts fine plaster sand and one part cement, it is a bit different from the brickies loams, as it is thicker and stronger and very close to the blocks colours when dry.   

To mix cement plaster to plaster walls;

This mixture is usually 3 part plaster sand and 1 part Portland cement, in some countries where lime is easier to have than cement it can be made by using a mixture of lime and cement for the interior, we believe that there are a lot of old places that they have used lime only, the cement mixture is used wherever it is too wet.

Cement topping;

This mixture is usually 3 parts river sand to 1 part Portland cement; it can be used straight on the cement if it is still green, but when the cement is dry you need to make sure it is clean and a bit rough for the cement to bond, you may have to use tools to indent the existing concrete, then you have to wet the cement and also you may need to use some cement bounding agent and/or paint to concrete with this cement glue called Weldbond or  Bondcrete or whatever and place the topping cement according to the instruction supplied, if these concrete glues are not available, you have to wet the concrete that you have to lay the topping on, then make some slur of water and cement and somehow work it in with a brush as if you paint the concrete, and before this starts drying lay your topping on it. 

These three mixtures plus the concrete are the main things that are required when we build with cement, of course for those people that do not know how the different materials look like, is still hard to understand the hole procedure easily, but if they read a few times what we have already said they should have a fair idea of what we are talking about. Anyhow I have already described several things already, but I think that I need still to describe how to mix mortar with lime only, as it was done in the old day and here I am not talking just hydrated lime that you can buy at the hardware store, but I am talking about quick-lime as it comes from the kiln and slacked lime. 

This is: 
Menfranco general blog, 
The art of mixing cement
Next time with, slacked lime 
Some personal and religious links: 

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