Cellular Concrete & its Facets of Application in Civil Engineering

Cellular Concrete is a cementitious paste of neat cement or cement & fine sand with a multitude of micro/macroscopic discrete air cells uniformly distributed throughout the mixture to create a lightweight concrete. The concrete is manufactured in two methods viz. First by mixing a preformed foam (surfactant) or mix-foaming agents mixture into the cement & water slurry with the hardening of concrete, the bubbles disintegrate leaving air voids of similar sizes. Second designated as Autoclaved Aerated Concrete (AAC), consisting of a mix of lime, sand, cement, water & 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 to be molded. Each mold is filled to one half of its depth with the slurry. The gasification process begins & the mixture expands to fill the mold above the top similar to baking a cake. After the initial setting, it is 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. HPCC has is an excellent insulator & significantly reduces the transfer of heat through concrete member. With a low water absorption, high tensile strength, high fire resistance & sound retention, this corrects deficiencies in the sand reducing bleeding. Besides structural forms cellular concrete finds application in as Flowable Fill or Controlled Low Strength Material (CLSM), Low Density Controlled Low Strength Material (LD-CLSM) which is a an engineered backfill material used as an alternative to compacted fill that can make backfill faster, being selfleveling, making total compaction within a few hours of placement. Compressive strengths can be adjusted according to the project requirements. Placing as a permanent material or permitting re-excavation at a later date is the paramount advantage of this material.