الفهرس 
Foam balls Lightweight concreteOnly 14 pages are availabe for public view
 |  | from | 291 |  |  |
| | | from | 291 | | |
Abstract
Researchers and industrialists’ interest in lightweight concrete (LWC) to be used in structural applications is steadily increasing. It is currently believed to have a promising future. It was restricted to use as partition wall, thermal insulation and rehabilitation work in the past. In the last few decades with the understanding of the phenomenon underlying LWC, efforts have been made to use foamed concrete in structural application. The main objective of the research was to investigate the mechanical and structural properties of foam balls lightweight concrete.
Foam balls lightweight concrete FBLWC is a type of concrete with cementations’ paste, fines, water, coarse aggregate and foam balls. The use of admixtures such as fly ash and silica fume, the foam concrete provides more strength. Foam balls lightweight concrete is a concrete weighing substantially less than that is made using gravel or crushed stone aggregates. FBLWC is usually chosen for structural purposes, which its use will lead to a lower overall cost of structure than will be expected with normal weight concrete. The general high unit cost of lightweight structural concrete is offset by reducing dead loads and lower foundation costs. A new kind of LWC (foamed balls lightweight concrete) was developed for foam balls lightweight concrete, in which conventionally aggregate is partially replaced by polystyrene foam particles, which combined the advantages of normal density concrete, cellular concrete and high workability.
Advances in the field of computer that aided engineering during the last two decades have been quite extensive and have led to considerable benefits to many engineering structures. In the building industry, the use of advanced finite element tools has not only allowed the introduction of innovative and efficient building products, but also the development of accurate design methods.
The main objective of this study was to determine the mechanical properties of FBLWC. The investigation focused on studying the compressive strength, tensile splitting strength, modulus of elasticity, stress-strain relationship in (compression and tension) and tension stiffening effect.
The research work included an experimental and a numerical phase. The experimental program included the testing of foam balls lightweight concrete specimens under concentric axial load in both tension and compression to obtain the actual stress strain properties of the produced FBLWC. The program consisted of twenty seven specimens of cubes, cylinders and prisms of FBLWC. Three standard cubes of dimension 150x150x150 mm and cylinders of dimension 150x300 mm were tested after 28 days to determine the compressive strength. Three cubes and five cylinders were tested after 28 days to draw the stress-strain relationship. One cylinder was tested to determine the Young’s modulus. The last three cubes were tested to determine the tensile splitting strength. Each prism with different steel bar diameter was tested to obtain the tension stiffening effect behavior of FBLWC.
This study showed that the use of foam balls in lightweight concrete clearly reduced the density of the concrete from 24.00 kN/m3 to 18.45 kN/m3 which represented a reduction of 23%. The average compressive strength for cube specimens was 27 MPa. And the average compressive strength for the cylinder specimens was 22.40 MPa. Also the ratio of the cylindrical compressive strength to the cubic compressive strength was about 0.81.
The stress-strain curve in tension was the average of direct tension for three specimens of 12 mm, 16 mm and 18 mm steel diameter in the middle of the FBLWC prisms. The curve assumed a linear relationship up to the concrete cracking strength, fcr. The fcr was 2.03 MPa and ԑcr was 0.00012. The calculated Ec was 16917 MPa. The difference between experimental Ec and calculated Ec from direct tension test was 2.5%. After cracking, where the average strain ԑm exceeded the cracking strain ԑcr, the stress-strain curve could be represented by exponential function up to average strain.
In the numerical phase, a finite element model was developed to be used for the simulation of nonlinear behavior of foam balls lightweight concrete. This finite element model was validated using previous experimental results available in literature and self-performed tests. The model would be calibrated and used to perform a parametric study on the behavior of foam balls lightweight concrete.