Concrete and Screed

Concrete and screed and are formed of the same basic ingredients – cement, aggregates and water. But what makes them different is the size of aggregates, the cement grade, mix consistency, and their intended application or use.

Composition and Mix Proportion

Concrete in its simplest form is a rock like mass formed by the hardening of cement paste and aggregates mixed in a proportion of – 1 Cement: 2 Sand: 3 Coarse aggregates (ballast/gravel). But many variations are applied to this basic mix design to suit different uses and strength requirements.

Screed is a thin layer of cement paste and sand/ fine aggregates, laid onto a concrete floor base or under floor heating to act as a smooth flat levelling surface for taking on the final floor finish. Screeds generally follow a mix proportion of 1Cement: 3-5Sand (0-4mm washed sharp sand for levelling screeds).

For heavy duty screeds 25 percent of the 0-4mm sand is replaced by 6-10mm single sized aggregates, making the mix proportion 1:3:1 – cement:0-4mm sand:6-10mm single sized aggregates. This is done to facilitate trowelling and to increase the density of the screed.

Finish

Concrete has a wide range of uses as building material, as a wearing surface and in masonry. It can be given a range of finishes from coarse to extremely smooth, depending on the intended use of the concrete.

But screed is used to create a smooth level surface for the final finish. It is not intended to be used as a final wearing surface. But screeds should be able to provide sufficient support and strength to its intended use.

Consistency of mix

Looking at consistency, concrete is mixed to a wetter consistency while the screed mix should be of a semi-dry, non-crumbly consistency. For concrete, the slump rates depend on the application and mix design.

Being a wetter mix, concrete is usually applied using floats or piston pumps, whereas the semi dry screeds are installed using pneumatic pumps or forced-action mixers. However, certain screeds that use an anhydrite base instead of cement are mixed to a free-flowing consistency and are applied using grout pumps/worm pumps.

CVC ReadyMix, the perfect ready mix concrete.

Comments

The Advantages of Ready Mix Concrete

Ready-mix concrete is concrete that is manufactured in a factory or batching plant, according to a set recipe, and then delivered to a work site by truck mounted in–transit mixers. This results in a precise mixture, allowing specialty concrete mixtures to be developed and implemented on construction sites. Ready-mix concrete is preferred over on-site concrete mixing because of the precision of the mixture and reduced work site confusion. The advantages of ready mix concrete are the following. Quality assured - It is produced under controlled conditions using consistent quality of raw material. High speed of construction- Speed of construction will be fast if ReadyMix Concrete is used. Reduction in cement consumption -The consumption of cement will be reduced by 10 – 12 % due to better handling and proper mixing. Versatility in uses and methods of placing - The mix design of the concrete can be tailor made to suit the placing methods of the...

Production Process of Ready Mix Concrete

Ready mix concrete is a mixture of Portland cement, water and aggregates comprising sand and gravel or crushed stone. During the mixing phase the different components come together to produce a uniform mass of concrete. A ready-mix concrete plant consists of silos that contain cement, sand, gravel and storage thanks of additives such as plasticizers, as well as a mixer to blend the components of concrete. These components are gravity fed into the preparation bin. The quality of concrete can be maintained only if the formulation is carefully administered. The water dosage in particular must be very precise and the mixing itself must remain continuous and consistent. To accommodate all of these constraints, the concrete plants have been automated to ensure reliability throughout the manufacturing process using centralized computer. Finally, the concrete prepared in a batch plant is loaded into a mixer truck, also known as a transit mixer, which delivers it to the construct...

Composition of Concrete

Concrete is made up of three main ingredients: water, Portland cement, and aggregates. The ratio of the ingredients changes the properties of the final product, which allows the engineer to design concrete that meets their specific needs. Admixtures are added to adjust the concrete mixture for specific performance criteria. Water The water in the concrete mix should be clean and free of impurities. The amount of water relative to the amount of cement changes how easily the concrete flows, but also affects the final strength of the concrete. More water makes for easier flowing concrete, but also makes for lower strength concrete upon curing. Portland cement Cement hardens when it is mixed with water, which binds all of the ingredients together. Portland cement is the most common cement used. It is composed of alumina, silica, lime, iron, and gypsum. Small amounts of other ingredients are also included. Aggregates The majority of a concrete mixture is made up of coars...

CVC ReadyMix

Search This Blog