Ghada N. Mohamed

A versatile building material, foamed concrete is made of cement, fine aggregate, and foam combined with coarse aggregate. This study provides a description of how constant coarse aggregate replacement (50%) of LECA and foamed concrete, which are lightweight concrete types, by zeolite as a filler and PEG-400 as a plasticizer, water retention agent, and strength enhancer affect the mechanical properties of the cement. A study that examined the characteristics of cellular lightweight concrete in both its fresh and hardened forms was carried out for both foamed concrete and LECA concrete. In order to do this, a composite of zeolite and polyethylene glycol 400 was made using the direct absorption method, and no leakage was seen. Zeolite was loaded to a level of 10% and 20% of the total weight in cement, while 400 g/mol PEG was used at levels of 1%, 1.5%, and 2% of the cement’s weight. Various mixtures having a dry density of 1250 kg/m³ were produced. Properties like dry density, splitting tensile strength, and compressive strength were measured. An increase in the amount of PEG400–zeolite was seen to lower the workability, or slump, of both foamed and LECA concrete, while the replacement of aggregate by zeolite resulted in an exponential drop in both compressive and flexural strengths.

In this study, hybrid nonlinear finite element models (FEM) were developed to examine the flexural performance and the ultimate load capacity of bonded and unbonded two-way reinforced concrete post-tensioned (PT) slabs that were pre-strengthened with external carbon-fiber reinforcement polymer (CFRP) laminates. Full 3D simulations, using ANSYS models, have been created for five different slab samples that were selected from a previously available experimental study. The model results were assessed to enable further numerical analysis. The result calibration included measurements of first crack loads, ultimate loads, deflections, strains in the extreme fiber of concrete, strains in CFRP laminates, and failure modes. The results proved a good correlation between FEM output and experimental ones. Based on this, the influencing parameters that affect plate stiffness, as well as the bending capacity of PT slabs, were examined by performing a detailed parametric study. The parameters included real-life load simulation, cable-to-CFRP strength contribution, and CFRP laminate location selection. The results demonstrated that strengthening using CFRP laminates have significantly increased the ductility index of both bonded and unbonded PT concrete slabs by 62.18% and 59.87%, respectively. In addition, strip strengthening locations near supports are much more effective than in the middle of slabs. Additionally, the CFRP strengthening contribution is very considerable in slabs with low PT ratios.