Viewed 2478 Times Published:2010-8-18 A Specified Density Concrete

A Specified Density Concrete [SDC] called High Strength Lightweight Structural Cellular Concrete or High-Performance Cellular Concrete [HPCC] / Air-Entrained Aggregate Concrete.

Cellular Concrete is a cementitious paste of neat cement or cement and fine sand with a multitude of micro/macroscopic discrete air cells uniformly distributed throughout the mixture to create a lightweight concrete.

It is commonly manufactured by two different methods. Method A, consists of mixing a pre-formed foam [surfactant] or mix-foaming agents mixture into the cement and water slurry. As the concrete hardens, the bubbles disintegrate leaving air voids of similar sizes.
Method B, known as Autoclaved Aerated Concrete [AAC] consists of a mix of lime, sand, cement, water and an expansion agent. The bubble is made by adding expansion agents [aluminum powder or hydrogen peroxide] to the mix during the mixing process. This creates a chemical reaction that generates gas, either as hydrogen or as oxygen to form a gas-bubble structure within the concrete. The material is then formed into molds. Each mold is filled to one-half of its depth with the slurry. The gasification process begins and the mixture expands to fill the mold above the top. Similar to baking a cake. After the initial setting, it is then cured under high-pressured-steam [180° to 210°C / 356°to 410°F] “autoclaved” for a specific amount of time to produce the final micro/macro-structure.
Recently, a direction to concrete compositions prepared by using aqueous gels [aquagels] is being considered as all or part of the aggregate in a concrete mix. Aquagel spheres, particles, or pieces are formed from gelatinized starch and added to a matrix. Starch modified or unmodified such as wheat, corn, rice, potato or a combination of a modified or unmodified starches are examples of aqueous gels. A modified starch is a starch that has been modified by hydrolysis or dextrinizaton. Agar is another material that can create a pore or cell in concrete. During the curing process as an aquagel loses moisture, it shrinks and eventually dries up to form a dried bead or particle that is a fraction of the size of the original aquagel in the cell or pore in the concrete. This results in a cellular, lightweight concrete.

High carbon ash, recycled aluminum waste and zeolite powders are additional mechanical structures suitable in the production of cellular lightweight concrete.
These cells may account for up to 80% of the total volumne. Weight of the concrete mixtures range from 220 kilograms per cubic meter [l4 lbs. cubic foot] to 1922 kilograms per cubic meter [120 lbs. cubic foot] and compressive strengths vary from 0.34 megapascals [50 pounds per square inch] to 20.7 megapascals [3,000 pounds per square inch].