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Foamed concrete has considerable potential as a material for use in the construction industry. However, although some researches have been conducted on the characteristics of foamed concrete, thus far, knowledge on the behaviour of foamed concrete has been limited. Hence, predictions of the stability of foamed concrete under different conditions and mix constituents have been uncertain. The aim of the presented study is to investigate causes of instability of foamed concrete by examining its rheological properties and microstructure. This study explores the complex causes of instability in foamed concrete by examining the rheological parameters, the yield stress and the plastic viscosity, since the rheological properties affect the hardened state. Using flowability as a guide, the relationships are examined between yield stress and viscosity, specifically with reference to their effect on density and w/c ratio. Other factors affecting the rheological properties related to the proportions and fineness of the mix constituents are also considered. Thereafter, the microstructure of foamed concrete is examined to establish links with the rheological values and the relationship with stability. The microstructure, best described by the bubble sizes, has been found to be a function of yield stress, plastic viscosity, material fineness and surfactant types. The bubble diameters have been shown to range between 0.1 to 0.5 mm. Bubbles less than 0.35 mm in diameter correspond to stable mix with a drop in level of less than 5% in height in densities of 1000 kg/m3 and higher. The big bubbles link to unstable mixes and have been found to be a source of instability. Other chemical additions were shown to result in disintegration of bubbles. As this study unfolds, a relationship is established between bubbles and the yield stress values. Bubble sizes reduced when the yield stress increased. For flowability out of Marsh cone test taken between 1 to 2 minutes, the corresponding yield stress was between 6.0 N/m2 to 8.5 N/m2. For this range, the empirical bubble sizes were found to be between 0.33 to 0.35 mm in diameter. In examining the possible causes of instability, it was found that stability improved markedly with increase in density and lesser effect by other factors such as w/c ratio, constituent materials and specimen height. However, the rate of hardening was a dominant factor in stability as evidenced by the use of Calcium Sulfoaluminate cement, CSA and CEM I 52.5R cement which increased the setting times. Stability was drastically achieved even at lower density 300 kg/m3. Blends of CSA with CEM I 52.5R and fine fly ash, FAf, demonstrated similar results. This research has implications for the development of foamed concrete as a material that could be more widely used in certain construction contexts where stability in lightweight density foamed concrete is crucial. It has contributed to better understanding of the rheological properties and the effect on the microstructure, even though the results are based on empirical values. Hence, it is anticipated that the prediction of stability can be made through a selection of materials and proportions to suit different contexts and their requirements.

LFC is cementatious material integrated with mechanically entrained foam in the mortar slurry which can produce a variety of densities ranging from 400 to 1600 kg/m3. The application of LFC has been primarily as a filler material in civil engineering works. This research explores the potential of using LFC in building construction, as non-load-bearing partitions of lightweight load-bearing structural members. Experimental and analytical studies will be undertaken to develop quantification models to obtain thermal and mechanical properties of LFC at ambient and elevated temperatures. In order to develop thermal property model, LFC is treated as a porous material and the effects of radiant heat transfer within the pores are included. The thermal conductivity model results are in very good agreement with the experimental results obtained from the guarded hot plate tests and with inverse analysis of LFC slabs heated from one side. Extensive compression and bending tests at elevated temperatures were performed for LFC densities of 650 and 1000 kg/m3 to obtain the mechanical properties of unstressed LFC. The test results indicate that the porosity of LFC is mainly a function of density and changes little at different temperatures. The reduction in strength and stiffness of LFC at high temperatures can be predicted using the mechanical property models for normal weight concrete provided that the LFC is based on ordinary Portland cement. Although LFC mechanical properties are low in comparison to normal weight concrete, LFC may be used as partition or light load-bearing walls in a low rise residential construction. To confirm this, structural tests were performed on a composite walling system consisting of two outer skins of profiled thin-walled steel sheeting with LFC core under axial compression, for steel sheeting thicknesses of 0.4mm and 0.8mm correspondingly. Using these test results, analytical models are developed to calculate the maximum load-bearing capacity of the composite walling, taking into consideration the local buckling effect of the steel sheeting and profiled shape of the LFC core. The results of a preliminary feasibility study indicate that LFC can achieve very good thermal insulation performance for fire resistance. A single layer of 650 kg/m3 density LFC panel of about 21 mm would be able to attain 30 minutes of standard fire resistance rating, which is comparable to gypsum plasterboard. The results of a feasibility study on structural performance of a composite walling system indicates that the proposed panel system, using 100mm LFC core and 0.4mm steel sheeting, has sufficient load carrying capacity to be used in low-rise residential construction up to four-storeys.

Lightweight cellular concrete (LCC) is mainly a mixture of water, cement, and foam bubbles. LCC generally has a cast density between 20-60 pcf and an air content between 49-84%. LCC is often used as a fill material because it has a low unit weight which reduces settlement. LCC is increasingly being considered as a backfill behind Mechanically Stabilized Earth (MSE) walls and embankments. Although engineers are using LCC in MSE walls or free face walls (MSE wall without the concrete panels or reinforcements), there is presently a lack of information regarding the performance and behavior of LCC to guide them. This research attempts to answer questions on the design of MSE walls backfilled with LCC and free face LCC walls by providing a well-documented case history and evaluating if LCC can be modeled as a c-ϕ material. A steel frame test box (10 ft wide x 12 ft long x 10 ft high) with a MSE wall on one side was constructed for the research. The box was filled with four lifts of LCC with steel ribbed-strip reinforcements extending into the LCC behind the MSE wall panels at the center of each lift. After the LCC was cured, two static load tests were performed by applying a surcharge load to the surface of the LCC. In one test, surcharge pressure was applied adjacent to the MSE wall to produce failure of the wall system. In a second test, the surcharge pressure was placed adjacent to a free face of the LCC to produce failure. String potentiometers (string pots), load cells, pressure plates, and strain gages were used to measure the behavior of the MSE wall and free face wall during testing. These two tests provided a comparison between LCC behavior with a MSE wall relative to a LCC free face. Failure of the free face wall with unreinforced LCC backfill in this test can be predicted using Rankine’s lateral force equation using a c-ϕ model. Failure angle at the base of the free face wall was between 51-63° which corresponds with an average friction angle (ϕ) of 24° and cohesion (c) of 1575 psf with an upper bound ϕ = 34° and a c = 1285 psf. The presence of reinforcements in the LCC backfill behind the MSE wall increased the capacity of the wall to hold a surcharge load. The presence of reinforcements in the LCC behind MSE walls also led to a much more ductile surcharge pressure vs. lateral deflection curve for the MSE wall compared to the free face wall.

This graduation thesis is aimed to presentation heat isolation materials for the floor constructions. The experimental part is devoted physical - mechanical properties suggested very light concretes with the cement. The main part of the thesis is devoted to form of the transit and putting of the individual heat isolation materials. In the end are suggested structures of the floor constructions with the respect to their properties and price.