Papers by Author: Weena Lokuge

Abstract: This paper presents the outcomes from a laboratory based research study undertaken to evaluate the fundamental properties of permeable concrete, including compressive strength, global and local strain, elastic modulus (stiffness), porosity and permeability. Six permeable concrete mixtures were made with constant water - cement ratio of 0.34, using different aggregate sizes and sand percentages. The compressive strength range was 15-35 MPa, while the permeability varied between 1.5 to 5.5mm/s and the porosity varied between 25 to 35 %. Two testing methods were used to measure the strain and modulus of elasticity (MOE) of the permeable concrete namely, platen-to-platen method and strain gauge method. Considerable difference was found between the MOEs obtained by the two methods. The MOE determined using the platen-to-platen method consistently were lower in value, which has been attributed to the softness of the capping components, the interface between the specimens and the platen and overall machine compliance. The pore characteristics and their distribution were seen to have an influence on the material responses such as material stiffness and strain. A comparison drawn between the axial strain obtained by the strain gauge measurement and that deduced from the platen-to-platen measurement was undertaken to evaluate the strain homogeneity along with possible detection of the localization phenomena.

Abstract: This paper investigates the compressive properties of polyester based fillers with different proportions of resin, sand and fly ash. The research program aims at developing a polymer based filler for a glass fibre reinforced polymer (GFRP) tube to be used as a structural rehabilitation system. It has been initiated to improve fundamental understanding of this material and to provide the knowledge required for its broad utilization. In this development, sample trial mixes were considered based on several weight percentages of polyester resin, fly ash and sand. These weight percentages were selected after analyzing volumetric properties of sand. The effect of resin (binder), sand and fly ash contents on the compressive strength of polyester based fillers with respect to age is reported. It has been found that at the age of 7 days all the batches reached about 90% of the compressive modulus. The experimental compressive stress-strain curves reported here were compared with established analytical models for normal strength concrete.

Abstract: The authors conducted research aimed at developing a new type of permeable concrete material with enhanced structural strength. This paper presents and discusses the results of their investigation on the unaxial compressive stress-strain relationship of porous concrete made with two different mix designs with constant water to cement ratio. The concrete mixes were designed with a target compressive strength between 15-25 MPa and target porosity between 10-15% to study the effect of pore sizes on the stress-strain curve. The average pore space was increased by increasing the relative amount of large aggregate. The reduction in the relative amount of fine aggregate increased the average pore space and resulted in a reduction in mix stiffness and a marginal increase in ultimate strength.