Concrete is a construction material that consists of cement (commonly Portland cement), aggregate (generally gravel and sand), water and admixtures.
Concrete solidifies and hardens after mixing and placement due to a chemical process known as hydration . The water reacts with the cement, which bonds the other components together, eventually creating a stone-like material. It is used to make pavements, architectural structures, foundations, motorways / roads, overpasses, parking structures, brick / block walls and footings for gates, fences and poles.
Regular concrete brick pavement
Regular concrete is the lay term describing concrete that is produced by following the mixing instructions that are commonly published on packets of cement, typically using sand or other common material as the aggregate, and often mixed in improvised containers. This concrete can be produced to yield a varying strength from about 10 MPa to about 20 MPa, depending on the purpose, ranging from blinding to structural concrete respectively. Many types of pre-mixed concrete are available which include powdered cement mixed with an aggregate, needing only water.
High Strength Concrete:
Use of Plasticizers
Plasticizers are additives that soften the materials (usually a plastic or a concrete mix) they are added to. Although the same compounds are often used for both plastics and concretes, the desired effect is slightly different. The plasticizers for plastics soften the final product increasing its flexibility. Plasticizers for concrete soften the mix before it hardens, increasing its workability , and are usually not intended to affect the properties of the final product after it hardens.
Superplasticizers are chemical admixtures that can be added to concrete mixtures to improve workability . Strength of concrete is inversely proportional to the amount of water added or water-cement (w/c) ratio. In order to produce stronger concrete, less water is added, which makes the concrete mixture very unworkable and difficult to mix, necessitating the use of plasticizers and superplasticizers.
Use of Plasticizers in concrete usually results in higher compressive strengths in the range of 20 to 40 MPa. Use of Superplasticizers results in strengths in the range of 60 Mpa (Previous Generation) to 120 Mpa (New Generation : Polycarboxylic Ethers)
Plasticizers are commonly manufactured from lignosulfonates , a by-product from the paper industry. Superplasticizers have generally been manufactured from sulfonated naphthalene formaldehyde or sulfonated melamine formaldehyde , although new generation products based on polycarboxylic ethers are now available.
Polycarboxylate Ethers (PCE)
Polycarboxylate Ethers (PCE), the new generation of superplasticisers are not only chemically different from the older sulphonated melamine and naphthalene based products but their action mechanism is also different, giving cement dispersion by steric stabilization, instead of electrostatic repulsion. This form of dispersion is more powerful in its effect and gives improved workability retention to the cementitious mix. Furthermore, the chemical structure of PCE allows for a greater degree of chemical modification than the older generation products, offering a range of performance that can be tailored to meet specific needs.
Concrete Curing Compound
Concrete Curing Compounds when sprayed or brushed on newly laid concrete surface forms a tough and elastic membrane thereby reducing the loss of water from concrete during early-hardening period. The concrete gets adequately hydrated by matrix water since evaporation of water from the surfaces is minimized by the film barrier of resin. The concrete achieves maximum beneficial properties including increase of mechanical strength.