Increasing interest is nowadays being paid to improving the thermal insulation of buildings in order to save energy and reduce ecological problems. Foamed concrete has unique characteristics and considerable potential as a promising material in construction applications. It is produced with a wide range of dry densities, between 600 and 1600 kg/m³. However, at a low density below 500 kg/m³, it tends to be unstable in its fresh state while exhibiting high drying shrinkage in its hardened state. In this study, lightweight aggregate-foamed concrete mixtures were prepared by the addition of preformed foam to a cement paste and aggregate. The focus of the research is the influence of fly ash, as well as fine lightweight aggregate addition, on the properties of foamed concrete with a density lower than 500 kg/m³. Concrete properties, including stability and consistency in the fresh state as well as thermal conductivity and mechanical properties in the hardened state, were evaluated in this study. Scanning electron microscopy (SEM) was used to study the microstructure of the foamed concrete. Several mixes with the same density were prepared and tested. The experimental results showed that under the same bulk density, incorporation of fine lightweight aggregate has a significant role on compressive strength development, depending on the characteristics of the lightweight aggregate. However, thermal conductivity is primarily related to the dry density of foamed concrete and only secondarily related to the aggregate content. In addition, the use of fine lightweight aggregate significantly reduces the drying shrinkage of foamed concrete. The results achieved in this work indicate the important role of lightweight aggregate on the stability of low-density foamed concrete, in both fresh and hardened states.

Structural lightweight concrete is preferred over traditional concrete due to its ability to reduce the dead load, minimize the size of load-bearing structural members, and provide more economical solutions for foundation deteriorations. This research sheds light on sustainable lightweight concrete using waste crushed clay bricks (CCB) as a lightweight aggregate. To reduce micro-crack propagation of the developed concrete, two types of fiber were implemented and investigated. Steel fibers (SF) with amounts of 0.5% and 1.0% by volume of concrete, and polypropylene fibers (PPF) with amounts of 0.1% and 0.2% by volume of concrete, were employed. Five reinforced concrete beams were made and tested in order to precisely evaluate the structural behavior of the proposed lightweight CCB concrete. Additionally, ABAQUS software for nonlinear finite element analysis has been utilized to simulate the tested beams and compare the numerical model predictions with the experimental findings. The findings revealed that the addition of SF and PPF exhibited a notable influence on enhancing the mechanical characteristics of lightweight CCB concrete. Adding 0.2% PPF increased the ultimate load and deformation capacity at failure by approximately 16% and 24%, respectively. Furthermore, after 28 days, the addition of 0.5% and 1.0% SF enhanced the compressive strength by around 11.7% and 17.6%, respectively. Moreover, a significant level of consistency between the results obtained from the numerical model and the experimental findings was observed. In general, the use of SF and PPF in CCB concrete successfully produced high-quality lightweight concrete with interesting results for use in reinforced concrete beams.

This paper includes the investigation of the soil–structure interaction (SSI) effect on the seismic response of 20 and 30-story reinforced concrete moment resisting frames (MRFs) rested on a piled raft foundation using the direct approach. After that, a study is conducted to show the impact of using a cellular raft instead of the designed solid raft on the dynamic response of the building. A study is introduced to select the best gap size for the cellular raft. The soil model is assumed as a single layer of sandy clay. Time history analysis by the direct integration method is performed under seven earthquake records (El-Centro, Northridge, Kobe, Chichi, Friuli, Kocaeli, and Loma), which are scaled to the Egyptian Code for Loads (ECP-201) response spectrum using a full 3D model by a finite element software named (Midas GTS NX). It is concluded that considering SSI significantly affects the dynamic response of high-rise buildings, and using cellular rafts generally leads to a decrease in their dynamic response.

Improving the thermal insulation properties of cement-based materials is the key to reducing energy loss and consumption in buildings. Lightweight cement-based composites can be used efficiently for this purpose, as a structural material with load bearing ability or as a non-structural one for thermal insulation. In this research, lightweight cement pastes containing fly ash and cement were prepared and tested. In these mixes, three different techniques for producing air voids inside the cement paste were used through the incorporation of aluminum powder (AL), air entraining agent (AA), and hollow microspheres (AS). Several experiments were carried out in order to examine the structural and physical characteristics of the cement composites, including dry density, compressive strength, porosity and absorption. A Hot Disk device was used to evaluate the thermal conductivity of different cement composites. In addition, X-ray micro-computed tomography (micro-CT) was adopted to investigate the microstructure of the air-entrained cement pastes and the spatial distribution of the voids inside pastes without destroying the specimens. The experimental results obtained showed that AS specimens with admixture of hollow microspheres can improve the compressive strength of cement composites compared to other air entraining admixtures at the same density level. It was also confirmed that the incorporation of aluminum powder creates large voids, which have a negative effect on specimens’ strength and absorption.

Lightweight concrete (LWC) can be considered as a structural material with unique characteristics such as reduced thermal insulation and low density. However, it consumes huge amount of artificial lightweight aggregates (LWA). Artificial LWA can be manufactured using sintering method or cold-bonded technique. Spite sintering method is more common due to low density of the produced LWA with appropriate mechanical characteristics, it has some economic and environmental drawbacks. Contrarily, cold-bonded technique has environmental and economic benefits due to potential lower energy consumption compared to sintering method. Nevertheless, its application still limited due to low mechanical properties as well as high density of the produced aggregate. This research presents a new method of producing sustainable core-shell artificial lightweight aggregate by using cold-bonded method. To minimize the aggregate density, expanded perlite particles with very low density was encapsulated in a cover layer made of powdered perlite, fly ash and cement. To improve mechanical characteristics of the produced aggregates, surface treatment using a mixture of microsilica and cement was applied. To compare the performance with sintered aggregates (expanded clay), several LWC mixes were prepared and tested. Mechanical properties, thermal conductivity as well as durability of LWC were measured. Scanning Electron Microscopy measurements were conducted to examine aggregate-cement matrix transition zone. The experimental results revealed that the performance of cold-bonded LWA is comparable with sintered LWA. Moreover, LWA with dry density in the range of 1200-1500 kg/m³ and compressive strength of 18-25 MPa was developed using cold-bonded LWA

In recent years, the presence of progressive collapse in tall buildings induced a catastrophic event which attracted the majority of the community’s attention. The purpose of this paper is to develop a 3D numerical analysis of tall building under column loss. A composite steel frame building with 25 stories with five spans in both directions is proposed. The building has 3 m story height and 8 m span in both directions. The building is designed through the commercial software SAP2000 software against wind loads based on Eurocode 1-2005. The focus here is to investigate various parametric studies under abrupt column loss of multi-story composite building. The effect of composite slab is considered with full composite action between beam and slab. The findings of a parametric formulation incorporating important parameters for the progressive collapse design technique are given and confirmed using nonlinear dynamic time history analyses. The assessment of results has been introduced based on deformation, axial force in columns, equivalent plastic strain, major moment and axial force in the considered beams above the column loss. Next, a probabilistic analysis has been performed to assess the behavior of composite steel buildings against column loss. The study investigates the critical column loss and pinpoints the location of the next critical column. The results show that the concrete grade, position of the removed column, beams cross-section, and place of bracings have a significant effect in the response of the building rather than the steel grade and bottom reinforcement density. The removal of exterior column has the significant increase of the axial force percentage by 111.4% for the corner column. The corner column removal gives the maximum equivalent plastic strain with a value of 0.00449. Furthermore, the results reveal the potential impact of uncertainty on the structural elements of the considered buildings through the progressive collapse analysis. The vertical displacement above the column is fitted with mean value of 0.0251387 m and with a coefficient of variation 0.01664.