Nanoconcrete (also spelled nano concrete or nano-concrete) is a form of

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

that contains

Portland cement Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th ...

particles that are no greater than 100 μm and particles of silica no greater than 500 μm, which fill voids that would otherwise occur in normal concrete, thereby substantially increasing the material's strength. It is also a product of high-energy mixing (HEM) of conventional cement, sand and water which is a bottom-up approach of nano technology.

Role of nano particles

The incorporation of ultra-fine particles into a Portland-cement paste within a concrete mixture in accordance with top-down approach of nano technology alters the concrete's material properties and performance by reducing the void space between the cement and aggregate in the cured concrete. This improves strength, durability, shrinkage and bonding to steel reinforcing bars.

Manufacture

To ensure the mixing is thorough enough to create nanoconcrete, the mixer must apply a total mixing power to the mixture of 30–600

watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...

s per kilogram of the mix. This mixing must continue long enough to yield a net

specific energy Specific energy or massic energy is energy per unit mass. It is also sometimes called gravimetric energy density, which is not to be confused with energy density, which is defined as energy per unit volume. It is used to quantify, for example, sto ...

expended upon the mix of at least 5000

joule The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applie ...

s per kilogram of the mix. and may be increased to 30–80 kJ per kilogram. A

superplasticizer Superplasticizers (SPs), also known as high range water reducers, are additives used in making high strength concrete. Plasticizers are chemical compounds that enable the production of concrete with approximately 15% less water content. Superplast ...

is then added to the activated mixture which can later be mixed with aggregates in a conventional

concrete mixer A concrete mixer (often colloquially called a cement mixer) is a device that homogeneously combines cement, aggregate such as sand or gravel, and water to form concrete. A typical concrete mixer uses a revolving drum to mix the components. F ...

. In the HEM process, the intense mixing of cement and water with or without sand in conditions of queasy laminar flow, Reynolds number 20-800 provides dissipation and absorption of energy by the mixture and increases shear stresses on the surface of cement particles. As a result, the temperature of the mixture increases by 20–25 and more degrees Celsius. This intense mixing serves to deepen hydration process inside the cement particles. The nano-sized colloid

Calcium Silicate Hydrate Calcium silicate hydrate (or C-S-H) is the main product of the hydration of Portland cement and is primarily responsible for the strength in cement based materials (e.g. concrete). Preparation When water is added to cement, each of the compounds ...

(C-S-H) formation increased several times compared with conventional mixing. Thus, the ordinary concrete transforms to nanoconcrete. The initial natural process of cement hydration with formation of colloidal globules about 5 nm in diameter spreads into the entire volume of cement–water matrix as the energy expended upon the mix. The liquid activated mixture can be used by itself for casting small architectural details and decorative items, or expanded with gas-forming admixture for making Aerated HEM Nanoconcrete as a

lightweight concrete Autoclaved aerated concrete (AAC) is a lightweight, precast, foam concrete building material suitable for producing concrete masonry unit like blocks. Composed of quartz sand (SiO2 with impurities), calcined calcium sulfate (CaSO4, a.k.a ...

. HEM Nanoconcrete hardens in low and subzero temperature conditions because the liquid phase inside the nano-pores of C-S-H gel doesn't freeze at temperatures from −8 to −42 degrees Celsius. The increased volume of gel reduces

capillarity Capillary action (sometimes called capillarity, capillary motion, capillary rise, capillary effect, or wicking) is the process of a liquid flowing in a narrow space without the assistance of, or even in opposition to, any external forces li ...

in solid and porous materials.

References

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