Text

theses

Autoclaved Aerated Concrete (AAC) is a lightweight porous cementitious material, made from cement, fine silica sand, water, aluminum powder, and quicklime. AAC which has a density of 400 to 600 kg/m3 can be considered as inorganic foam. This material is attractive for use as building elements due to their light weight as compared to normal concrete, fire resistance, ease of construction, energy efficiency, and sound insulation. In most of these applications, the precast structural elements made of AAC are subjected compression and bending forces. Since the bending strength of AAC is very low, its flexural capacity is improved by using steel wire mesh and small size rebars. However, due to the weak bond between AAC and steel wires and small bars and potential corrosion, needed strength increases cannot be obtained. This dissertation studies the use of basalt fabric composite for enhancing the flexural strength of AAC beams and panels. It also evaluates the effect of higher temperatures on the flexural strength of plain and strengthened AAC beams. The basalt fibers were applied to the AAC using an inorganic matrix to preserve the fire resistance capability of both AAC and the basalt fibers. An experimental investigation was conducted to evaluate the capability of an inorganic matrix to fully develop the strength capacity of the basalt fiber in tension. Several series of strengthened AAC beams were tested in flexure following ASTM C 1452-06. Results show that the matrix is capable of providing the required bond between the basalt fibers and AAC. The strength capacity of basalt fibers was fully developed for tows and fabrics basalt reinforcement, and significant increase of flexural strength was achieved. The strengthening also reduced the loss of strength at elevated temperatures compared to plain beams. An analytical study was performed to predict the failure load in flexure. The failure load was predicted using three methods: elastic analysis, ultimate stress analysis, and non-linear analysis. The results of the analytical methods showed that the flexural strength of basalt fiber reinforced AAC beams can be reasonably predicted using the analytical models. The hand impregnation technique used to apply the matrix is conducive for easy field applications. The results show that the potential of significantly increasing the bending capacity of AAC panels making it a viable the system for practical applications. It is anticipated that the increase in strength will lead to longer spans and less thickness in exterior wall panels and roofing elements.

ETD_8768

Ph.D.

Includes bibliographical references

by Alaa Ali

doi:10.7282/T38K7DHS

ETD doctoral

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