COMPRESSIVE STRENGTH OF FOAMED CONCRETE IN RELATION TO POROSITY USING SEM IMAGES

Abstract

Foamed concrete specimens were examined for compressive strength at (28 and 180) days air sealed curing, as well as at 28 days water cured. Also, the microstructure of fifteen selected FC specimens was investigated for porosity in relation to compressive strength using Scanning Electron Microscopy (SEM) images. Twenty two batches of FC specimens of the densities (1100, 1600 and 1800) kg/m3 were made with fine sand and brick aggregates with toner and metakaolin (MK) inclusion as additives, they were casted in polystyrene cube moulds of (100x100x100) mm. Results show, it is possible to produce FC with high compressive strength in the range of (28.5 to 59.2) N/mm2, with a variety of materials, while the 1600 kg/m3 density with the inclusion of toner and MK20 is the favourite, which can be used for structural elements. Conventionally, compressive strength is in an inverse relationship with porosity, as porosity increases, compressive strength decreases, but using toner and MK20 can alter this relationship between porosity and compressive strength, where by it is possible to produce a relatively light weight high porosity FC matrix to exhibit high compressive strength. Maturity of the FC at 180 days, can demonstrate an increase in the compressive strength. The microstructural investigations through SEM images revealed, the FC mix made with sand or brick only, exhibits an irregular shape factor of the micro pore system with the pore size in the range of (10 to 70) µm, while those made with the inclusion of toner and MK20 have a regular shape factor of a matrix of finer micro pore system of the sizes in the range of (0.01 to 10.0) µm, all of which are evenly distributed, and have a big influence on the properties of the FC, particularly, on compressive strength. Contrary to the conventional method of air sealed curing for FC, water curing method can equally give the same or a slightly better result in respect of compressive strength for some particular densities.