Cement mortar and bindings

Cement mortar

The word cement is often used where we actually mean grout or mortar. Cement is a raw material which is mixed with water and other materials (e.g., sand, lime and possibly gravel). After the cement is processed it turns into masonry mortar, grout, mortar or concrete. For bricklaying or filling joints it’s not the actual cement you use, but the processed mortar product in which cement is used. This article also describes how to make mortar, and then how to waterproof the mortar. Because without additional measures concrete and masonry eventually get symptoms of rising damp.

Cement mortar is a commonly used binding agent for any type of brickwork or concrete. It glues the brickwork or concrete together. In addition to cement there’re other binders you can use. And it has to comply with a large number of requirements. For example, composition, strength, shape restraint and binding. In the Netherlands there are three types of cement used on a large scale. Portland cement, Portland fly ash cement and blast furnace cement. Different cement mortars are also specific to the application areas due to their specific characteristics.

Cement mortar

What are the properties of cement?

Portland cement has the ability to quickly harden. Portland cement with fly ash has a slower development of hardening. The final strength is at least equal, but Portland cement with fly ash can achieve a greater density. Blast furnace cement with high slag content can result in a very dense structure. Therefore aggressive substances such as chlorides and sulfates won’t be able to penetrate. This makes blast furnace cement suitable for use in contact with sea water, water or soil that contains sulfates and other aggressive environments.

Making the mortar

Cement is a finely ground bonding agent (consisting mainly of calcium silicate hydrogen). Together with water it forms a plastic mass which is hard, both in the open air or in water. Mixing it with other substances like masonry sand or lime you can create masonry cement. Bricklayers use masonry cement for building a wall and crafting the joints. Also, concrete is made on the basis of cement. For concrete, the cement becomes less mixed with sand, but with gravel.

To make mortar you will need a masonry arch and a bucket and – especially in larger quantities – preferably a mixer. If you don’t have a blender, you can use the trowel to mix the grout. This tool is required for the masonry itself, but can also be useful for mixing. First, the dry substances must be mixed properly with each other. This is the cement, sand and lime. Only after that the water can be added. Always use clean materials, each pollution reduces the quality of the mortar. During the making of the mortar, the ratio can be controlled conveniently by pulling a slot in the container filled with grout. If that slot retains its shape and does not fill with water, the proportions are correct. Never make more mortar than you can process in an hour or two to prevent dehydration.

For the do-it-yourself-er there is a wide range of masonry cement and mortar bags for merchandise. These already contain the desired ratio of sand and lime. Only the water must be added and your ready to go.

Mixing ratio

For mortar is the standard ratio: 1 part cement and 3 parts sand. Finding the exact composition is a matter of knowledge and experience. It is also partly determined by the application for which the mortar is used. For example, one sees for masonry facade of exterior walls with hard clinker often a recipe of 1 part of cement, 3.5 parts of sand and a quarter lime. Whereas for the same job, but with much softer limestone, a completely different mixing ratio is recommended, namely 1 part cement, 9 parts sand, 2 parts lime.

The right ratio for the cement mortar also depends on the type of brick that is used, and the location of the masonry (inside or outside). In addition, water has to be added to the cement. By using more water is to process the grout more fluid and, therefore, easier. But too much water means that decreases the binding force. Thereby, after drying shrinkage cracks occur. In general, well-made mortar sticks to a wall and do not bleed.

Waterproofing cement

The above described conventional method of making masonry cement does have one major drawback: the mortar is in fact not waterproof. The brickwork won’t be waterproof and rising damp is not stopped. In concrete, the moisture absorption can even affect the armaments with carbonation of your reinforced concrete as a result.

Fortunately, there is an effective solution to this problem: Cement-mix. It’s is a fluid that replaces the water in the mixing of mortar, concrete or mortar. You can add the mix directly into the mixing container, bucket or cement mixer in the same proportion as you would have used water. The product works from the inside and connects all the particles in the concrete, mortar and mortar with each other. Thanks to this solution the cement or mortar is completely waterproof and water-repellent, and it stops rising damp. Therefore the use of Cement-mix is a great solution for all bricklayers.

Crystal formation in cement

If cement reacts with water it forms part of the pores between the grains of cement crystals. These crystals grow into each other forming a dense structure. It also affects the sand and gravel grains, there arises a physical-mechanical connection. As long as there is water, the crystal formation continues. However, more and more slowly because the pores are shrinking. Water is partly chemically bonded getting into the smaller pores of concrete. By the binding the water jells, the concrete mortar hardens. In that phase of hardening, it is important for the fresh concrete not to move or vibrate, because that breaks the brittle structure.