This paper examined the foamed concrete (FC) for permeability of total and capillary water absorption, at 28 days of air sealed curing. The microstructure of 15 selected FC specimens was investigated to determine permeability in relation to porosity and density using Scanning Electron Microscopy (SEM) images. The FC specimens of the densities (1100, 1600, and 1800) kg/m3 were made using fine sand and brick aggregates with toner and MK inclusion as additives. The microstructural investigation of the FC revealed, porosity measure as a percentage ratio of the area under investigation to be in the range of (39.65 to 77.7) %. The pore size is in the range of (0.01 to 70) µm, depending on the type of additive, for the mixes containing toner and MK, it is in a fine range of (0.01 to 10.0) µm. For the FC specimens, the finer the pore size, the less permeable and the stronger it is. Permeability is porosity and strength dependent, whereby high porosity leads to high permeability and low compressive strength for FC mixes made with sand or brick only with no additive inclusion. Meanwhile, the FC mixes made with the inclusion of additives, such as the toner and MK20 mixes, showed an evenly spread net of independent air voids with a regular shape within their matrix, which is beneficial in decreasing permeability. Therefore, besides the porosity and strength, the fineness of the pore matrix and the shape factor of the pores are two other key factors in controlling permeability. Toner and MK20 inclusion can enhance the capillary water absorption to reach almost water tight. Besides, MK30 and MK50 inclusion displayed adverse effect on permeability. Depending on the type of filler, the additive, and the percentage ratio of the porosity of the FC matrix at (1600 and 1800) kg/m3 densities, it is possible to produce FC with compressive strength between (55.1 and 30) N/mm2.
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.
This paper investigates the mechanical properties at a fresh and hardened states of a new foamed concrete. The aim is to develop and produce a hydrophobic lightweight foamed concrete with enhanced properties for structural use. Foamed concrete generally is made of ordinary Portland cement (OPC), fine aggregates, foaming agent, admixtures and water. Metakaolin (MK) and water reducing admixture were used with the mix in this study. The physical properties of the mixes in their fresh state, mainly the consistency of the mixes was determined. All the mixes prepared were undergone rheology test at fixed water/cement (w/c) ratio of 50%, testing for flowability and spreadability. Compressive strength testing was carried out on 100 mm cubes and the results revealed that the compressive strength of foamed concrete decreases with a reduction in density. Flexural strength and flexural modulus, which were tested on 100 x 100 x 500 mm prisms, were also found to decrease with the reduction in density. The use of MK improved compressive strength as well as flexural strength development for normal and foamed concrete. Higher improvement was noted for the flexural strength with the use of a higher dosage of MK.
This paper investigates the effect of toner as a new material on enhancing compressive strength and permeability of foamed concrete (FC). The aim is to develop the FC through testing the reaction of toner with the cement of the FC, to produce a hydrophobic lightweight FC to use for structural elements. Foamed concrete is generally made of ordinary Portland cement (OPC), sand, foaming agent, and water with a well spread pore structure. The experiment was carried out on 100 mm cubes. Results for toner inclusion of all the mixes, when added in the right quantities, showed high improvement for water penetration and compressive strength in comparison to the published data on FC for the use as structural material, which is a step forward in the advancement of FC to meet the aim of this research.
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