Introducing a Method to Determine Nonautoclaved Aerated Concrete Air content Based on Packing Theory

Abstract

This paper presents an experimental study on fresh and hardened properties of nonautoclaved aerated concrete (NAAC) mixtures. It also attempts to address a new method to determine the packing density and air percentage of NAAC mixtures. Different types of NAAC mixtures with various aluminum powder percentages and water-to-cement ratios were made. Results revealed that the new method (called the wet packing theory) is able to determine the percentage of air pores in the aerated concrete with high accuracy. Results also showed that there is an optimum aluminum percentage of approximately .934 from the perspective of minislump diameter and compressive strength. With an increase in the aluminum percentage compared to the optimum percentage, minislump (workability and flow-ability) and compressive strength reduced. Scanning electron microscope (SEM) images of NAAC indicated that the air voids were shaped as an artificial porosity. The results showed that with an increase in the amount of aluminum powder, packing density reduced. It was observed that the maximum air percentage increased with an increase in the amount of aluminum percentage from .934 to .1869.