Enhancing lightweight concrete with silica fume: A nonlinear finite element analysis of plastic damage

The paper presents a novel plastic-damage constitutive model for two types of lightweight concrete (LWC), namely aerated concrete (AC) and recycled coarse concrete with no fine aggregate (RC). The model has the potential to improve the ductility and toughness of the LWC, while simultaneously reducing its damage level. The amount of silica fume (SF) used in the concrete mix determines the extent of these improvements. Therefore, an experimental investigation was used to determine the optimal percentage of (SF) that should be used in the proposed model for the two types (LWC). These types of concrete included recycled coarse aggregate at a ratio of 6:1 to the amount of cement, which allowed for the incorporation of waste materials into the concrete mix. Additionally, aerated concrete (AC) was produced by adding composite fly ash (FA) and aluminum powder (AL) in proportions of 10% and 0.2%, respectively, based on the weight of the cement fresh and hardened concrete tests were carried out, for 7,14, and 28 days on the samples tested consisted of 36 cubes measuring 150 x 150 x 150 mm and 9 cylinders measuring 150 mm in diameter and 300 mm in height, the highest compressive strength was achieved when using an optimal proportion of SF and FA in AC3 and RC3 for aerated and recycled (LWC), respectively. This proportion involved a 20% addition of silica fume (based on cement content). Furthermore, the numerical study demonstrated that the proposed algorithm is effective and resilient in finite element analysis FEA ABAQUS software to develop a concrete plastic-damage (CDP) constitutive model suitable for RC3 and AC3 to simulate the tension stiffening behavior with stress strain diagram. This model employs two damage variables to represent tensile and compressive damage independently. Furthermore, this model utilizes a combined approach of continuum damage mechanics and plasticity theory, which is known as the compression cylinder model of lightweight concrete with a damage plasticity (CDP) method. These investigations also provide valuable insights into the impact of SF on the plasticity behavior of LWC concrete, which can enhance its ductility, and toughness, and reduce its damage level depending on the percentage of SF. In addition, the numerical results employ statistical regression analysis to establish the equations that indicate the relationship between compression stress and tensile strength (ƒc and ƒt) for high-strength values from all samples (AC3 and RC3).