BEHAVIOR OF LIGHTWEIGHT CONCRETE UNDER UNIAXIAL ECCENTRIC COMPRESSIVE STRESSES

Abstract

This research was initiated with the objective of investigating the behavior of light weight concrete “LWC” by partial aggregate replacement with polystyrene foam under uniaxial eccentric compression. This is attributed to the fact that the reduced mass concrete reduces the imposed lateral load during earthquakes. Primarily, literature review was carried out in the field of LWC in order to determine the research gaps or weak points to commence this research. Accordingly, an experimental work was carried out. It encompassed three investigation phases (mix selection phase, stress block parameter phase and behavior under eccentric compression phase) All through the mix selection phase, five lightweight concrete mixes were investigated in terms of compressive, and tensile strengths. During the stress block investigation phase, LWC was examined in terms of stress block parameters. Throughout the eccentric load investigation phase, the behavior of LWC columns was examined under eccentric load. In the first phase the properties of the different mixes were determined in order to use suitable mix, in this study we used mix which have cylindrical compressive strength 30 MPa, cubic compressive strength 38MPa, tensile strength 3.35MPa, and density 18.1KN/m3. The second phase was aimed to determine the stress-strain distribution of LWC and evaluate equivalent compressive stress block parameters various parameters of the rectangular stress block, Two square half-scale columns specimens with dimension 200 x 200 mm and 1600 mm height was tested. It had two steel beams, each of them was connected at the top and bottom ends of the specimen to transfer the moment from the applied load to specimen. This phase results indicated that the stress block parameter k1, k2, k3 is equal 0.49, 0.37, 1.12 respectively when cylinder lightweight concrete compressive strength 30 MPa. From these values we found the stress block parameters α1 and β1 equal 0.78 and 0.73 respectively. For the third phase, six half scale LWC square specimens with different eccentric ratios (e/t) and different transverse reinforcement were tested under eccentric loads using the same dimensions as in the second phase. The results signposted that increasing eccentricity ratio change the behavior of columns failure from compression to tension failure, and it leads to reduced failure load of column due to generation additional moment, it resulting to increase lightweight concrete compression side strain value, reduce strain in the longitudinal reinforcement, and reduce the transverse reinforcement strain at failure load. On the other hand, the results designated