Sufficient deformability can be achieved in concrete while maintaining segregation resistance either by using a chemical viscosity-modifying admixture (VMA) or increasing the fine content in the concrete. Using VMA, the initial cost of self-compacting concrete (SCC) increases, making it unsuitable for general construction. As a result, alternative methods for lowering the cost of SCC must be investigated. In this study, we assess the effectiveness of fly ash (FA) as a viscosity-modifying agent in the production of cost-effective and durable SCC. We also forge new pathways for sustainable development. The percentage of FA, superplasticizer dose, and water/binder ratio were varied, whereas the amounts of cement and water, as well as fine/coarse aggregate content were kept constant. Fresh properties, such as flow, filling and passing abilities, viscosity, and segregation resistance, were measured. Compressive/flexural strength, density, water absorption, and rate of water absorption of hardened SCC were also determined. The test results showed that fly ash can be used as an alternative to a VMA to produce cost-effective, self-compacting concrete. The slump flow of the various fresh-state concrete mixes ranged from 200 to 770 mm, with an L-box ratio of 0 to 1 and a flow time of 2.18 to 88 s. At 28 and 56 days, the compressive strengths of the concrete mixes with fly ash were found to be comparable to those of the control concrete mixes with VMA. The cost of ingredients for a specific SCC mix is 26.8% lower than the price of control concrete, according to a cost comparison assessment.

In this research study, environmentally friendly unburnt coal ash (CA) bricks were investigated as an alternative to conventional burnt clay bricks. In this research study, various physical and mechanical properties of unburnt CA bricks were investigated. The unburnt CA bricks were prepared by using 60% CA and 10% lime by weight. In these unburnt CA bricks, varying cement contents (5%, 10%, and 15%), sand contents (10% and 15%), and quarry dust contents (5% and 10%) by weight were used. A forming pressure of 29 MPa was applied through an automatic pressure control system either for 3 s or 6 s. The prepared bricks were moist cured for 28 days. The experimental results exhibited that unburnt CA bricks with 10% cement, 10% sand, and 10% quarry dust subjected to forming pressure for 3 s exhibited the highest compressive strength of 19 MPa and flexural strength of 2.1 MPa. The unburnt CA bricks exhibited reduced water absorption, reduced efflorescence, and lower weight per unit area than the conventional clay bricks. A cost comparison of unburnt CA bricks and clay bricks exhibited that unburnt CA bricks are cost-effective compared to clay bricks.

Steel reinforcement corrosion in concrete structures such as bridges, industrial plants, marine structures, and coastal buildings is a growing concern due to its impact on cost, safety, and serviceability. Corrosion leads to spalling, cracking, and reduced reinforcement diameter, which can compromise structural integrity. This study examines the behavior of concrete columns with corroded reinforcement in two phases. In the first phase, 72 columns of 150 × 150 mm cross-sectional dimensions and 300 mm length were cast and subjected to an accelerated corrosion technique. The study examined variables such as concrete cover, concrete strength, and corrosion exposure. The second phase involved studying the axial behavior of corroded columns concerning the effect of column length. Column specimens of 150 × 150 mm cross-sectional dimensions and lengths of 500 mm, 700 mm, and 900 mm were cast, corroded, and tested under axial compressive load. The study revealed that a 30 mm concrete cover offers 10% more protection against corrosion than a 20 mm cover. Continuous exposure to a corrosive environment reduces the load-carrying capacity by 50%, while columns with 28 MPa concrete strength can carry 4% more load. Longer columns are more susceptible to corrosion, leading to a significant reduction in load-carrying capacity and concrete cover damage. Therefore, maintaining adequate concrete cover, strength, and regular inspections are essential to address steel reinforcement corrosion and preserve structural integrity.

This research investigates the nonlinear behavior of scaled infilled masonry (IFM), confined masonry (CM), and reinforced concrete (RC) structures by utilizing and validating two tests from the literature as benchmarks. The validation was based on a comparison with the pushover results of small-scaled physical tests and their numerical modeling. Numerical modeling of small-scale (1:4 and 1:3) IFM, CM, and RC models has been carried out with Finite Element Modelling (FEM) and Applied Element Modelling (AEM) techniques using SAP2000 and the Extreme Loading for Structures (ELS) software, respectively. The behavior of the structure under lateral loads and excitations was investigated using nonlinear static (pushover) and nonlinear time history (dynamic) analysis. The evaluation of the pushover analysis results revealed that for IFM, the %age difference of tangent stiffness was 4.2% and 13.5% for FEMA Strut and AEM, respectively, and the %age difference for strength was 31.2% and 2.8% for FEMA Strut and AEM, respectively. Similarly, it was also calculated for other wall types. Dynamic analysis results from FEM and AEM techniques were found in the fairly acceptable range before yield; however, beyond yield, AEM proved more stable. Finally, the results also showed that the numerical study can be utilized for the evaluation of small-scale models before performing the physical test.

A simultaneous crack extension pull-out model for post-installed anchor bar is presented. The anchor bar is such that used in various strengthening techniques to strengthen reinforced concrete structures. The properties of the infill material used for post-installed anchor bar are characterized by a nonlinear interface between the surrounding concrete and the anchor bar. This is a new type of anchor-infill assembly in which the infill material is divided into two layers for the purpose of providing a larger failure path length resulting in increase of the energy absorption and pull-out load capacity. The mechanical properties of the infill layer are different from the surrounding concrete. Therefore the existing pull-out model of deformed bars cannot be applied directly in this case. The interfacial de-bonding is examined by the strength criterion expressed in terms of interfacial shear stress. Pre-existing cracks representing artificial notches are assumed at the top of infill layers for identifying crack location and stabilizing its propagation direction. All the possibilities associated with two-cracks in the close vicinity have been investigated in detail. The objective of the analysis is to predict a set of material properties which result in simultaneous crack extension at the two interfaces and also to identify a simultaneous crack extension length which results in increasing the pull-out load capacity, increase in energy absorption and increased failure path length but achieved at lowest increase in pull-out deformation thereby proving the effectiveness of two-layer model. Limiting the pull-out deformation is desirable from the point of view of limiting damage.

Natural aggregate and attached mortar are the two main components of the recycled concrete aggregates (RCA), therefore, compared to natural concrete aggregates (NCA), RCA generally have significant heterogeneity. Due to variation in their expected behavior as a result of heterogeneity, the use of RCA in concrete for various applications is still very limited. Since the properties of natural aggregates and adhered mortar in RCA are mainly dictated by the quality of their parent concrete, the careful evaluation of properties of RCA derived from waste concrete of different sources is always required before their possible use in concrete. Research studies in the past have revealed that the strength of parent concrete has always had a considerable impact on the physical and mechanical properties of RCA. In this study, RCA were produced from four classes of parent concrete with respect to their initial strength (i.e., 21 to 28 MPa, 28 to 35 MPa, 35 to 42 MPa, and above 42 MPa) and were used in the manufacturing of concrete bricks by replacing 100% NCA (fine and coarse) with RCA. Tests were performed to evaluate the effect of the parent concrete strength on the physical and strength properties of RCA, and the mechanical behavior of recycled aggregate concrete (RAC) bricks. For comparison, Natural Aggregate Concrete (NAC) and burnt-clay bricks were also tested. RAC and NAC bricks were manufactured using 10% cement and under a casting pressure of 35 MPa. Compressive, shear, and flexure strengths and impact resistance of bricks were determined using standard tests. The results showed that the physical and strength properties, and water absorption of RCA were improved with the increase in strength of their parent concrete. The water absorption of coarse RCA obtained from low-strength concrete (i.e., 21 to 28 MPa) was 4.8 times higher than that of NCA, whereas coarse RCA obtained from concrete with compressive strength above 42 MPa showed almost similar physical properties as those of NCA. For RAC bricks prepared with RCA obtained from high-strength parent concrete (i.e., > 42MPa), 11% improvement in compressive strength, 2.23% decrease in the flexure strength, and 6.6% increase in the shear strength were observed in comparison with NAC bricks. Compression, shear, flexure strength, and impact resistance of RAC bricks were found to satisfy the requirements of local and ASTM Standards and were higher than those of burnt-clay bricks. This study finally concluded that fully RAC bricks manufactured using RCA derived from old concrete having compressive strength greater than 21 MPa are not only structurally viable but are also environmentally friendly and could help to manage construction and demolition (CandD) wastes efficiently and beneficially.