Investigation into the Properties of Aerated and Fibre-Reinforced Aerated Concrete

Abstract

Aerated concrete (AC) is classified as lightweight concrete in which air voids are entrapped in the mortar by means of a suitable aerating agent depending upon the requirements of density and strength. It is a relatively new building material and is therefore not as well researched, documented and applied commercially when compared to normal concrete (NC) and masonry. To produce LWC for structural purposes, it should be designed with a density of 1300-1900 kg/m3 and a compressive strength of more than 20 MPa according to ACI.213R (2014). The scope of this PhD study covers material mixture design, experimental tests and finite element (FE) simulation on structural response of the designed AC materials. The statistical analysis software Design Expert and a Response Surface Methodology were used to optimise the AC mix. Aluminium is available in a range of particle sizes varying from coarse, through medium to fine. Silica Fume (SF) is used as an additional material with different content range from 5%-10% to enhance the compressive and flexural strength of the AC. However, the autoclave is limited by the operating parameters available which provides 100 - 140 °C, 0 - 2.4 bar. The experimental tests are limited to the compressive strength from 100 mm cubes whereas the modulus has been found using cylinders (200 mm long by 100 mm diameter), tensile strength from large dog-bone specimens (210 mm length and provided between grips), flexural strength from prism specimens (40 mm x 40 mm x 160 mm), porosity, sorptivity and water absorption from disk samples with diameter 70 mm and height 70 ±5 mm. FE simulations with a concrete damage plasticity (CDP) model for notched beam specimens with width = 150 mm, length = 550 mm and depth = 60, 90, 150 and 180 mm have been provided. FEM was used to predict the structural response of the beams made of steel fibre-reinforced aerated concrete after a validation work for a beam with different mesh size and geometric parameters (depth) was carried out. The results of the experimental works showed that the optimised mix design with the target values of the AC was realised by RSM. SF did not cause a superior increase in the strength characteristics of the material as compared to those of NC. The available autoclave did not have the capacity in terms of volume, temperature and pressure to make a significant contribution to this work. In addition, the coarse aluminium particles of the size of 125 µm with 0.5% content were the most suitable ones to produce a structural AC which matched the target of the density and strength of AC. Steel fibres with an aspect ratio of 67 had the higher compressive, tensile and flexural strength within the required density.

Date of Award	31 Dec 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Paul Nedwell (Supervisor) & Jack Wu (Supervisor)