Structural Performance of Ferrocement Panels under Low- and High-Velocity Impact Load.

The primary objective of this experimental study is to examine the response and energy absorption capacity of ferrocement panels exposed to low- and high-velocity impact loads. The panels are reinforced with two different types of mesh layers, namely, welded wire grid (WWG) and expanded wire grid (EWG), with varying percentages of steel fibers (SF). The ferrocement panel system is made up of cement mortar reinforced with 0-2% SF with an increment of 1% and wire grid layers arranged in three different layers 1, 2, and 3. A consistent water-cement ratio (w/c) of 0.4 is maintained during mortar preparation, and all panels are subjected to a 28-day curing process in water. The study utilized square-shaped ferrocement panels measuring 290 mm × 290 mm × 50 mm. The panels are exposed to repeated impact blows from a 2.5 kg falling mass dropped from a height of 0.80 m. The count of blows necessary to commence the first crack formation and the cause of ultimate failure are recorded for each panel. The study reports that an increase in SF content and the number of wire grid layers increased the number of blows needed for both the first crack and the ultimate failure. In the high-velocity impact test, 7.62 mm bullets are fired at the panels from a distance of 10 m with a striking velocity of 715 m/s. The study observed and analyzed the extent of spalling, scabbing, and perforation. The results showed that an increase in fiber content and the number of wire grid layers led to a decrease in the area of scabbing and spalling compared with the control specimens. It was also possible to see the mode of failure and crack pattern for impacts with low and high velocities.

Investigation of Alkali-Activated Slag-Based Composite Incorporating Dehydrated Cement Powder and Red Mud.

Recycled construction cementitious materials (RCCM) and red mud (RM) could be considered a type of discarded material with potential cementitious properties. Generally, landfilling and stacking are utilized to dispose of this type of solid waste, which can be detrimental to the environment and sustainability of the construction sector. Accordingly, a productive process for making eco-efficient alkali-activated slag-based samples with the inclusion of RCCM and red mud is studied in this paper. Dehydrated cement powder (DCP) is attained through the high-temperature treatment of RCCM, and red mud can be obtained from the alumina industry. Subsequently, DCP and RM are utilized as a partial substitute for granulated blast furnace slag (GBFS) in alkali-activated mixtures. Two different batches were designed; the first batch had only DCP at a dosage of 15%, 30%, 45%, and 60% as a partial substitute for GBFS, and the second batch had both DCP and RM at 15%, 30%, 45%, and 60% as a partial substitute for GBFS. Different strength and durability characteristics were assessed. The findings show that when both dehydrated cement powder and red mud are utilized in high quantities, the strength and durability of the specimens were enhanced, with compressive strength improving by 42.2% at 28 days. Such improvement was obtained when 7.5% each of DCP and RM were added. The results revealed that DCP and RM have a negative effect on workability, whilst they had a positive impact on the drying shrinkage as well as the mechanical strength. X-ray diffraction and micro-structural analysis showed that when the amount of DCP and RM is increased, a smaller number of reactive products forms, and the microstructure was denser than in the case of the samples made with DCP alone. It was also confirmed that when DCP and RM are used at optimized dosages, they can be a potential sustainable binder substitute; thus, valorizing wastes and inhibiting their negative environmental footprint.

Experimental Analysis of Channel Steel Member under Tension Load with Damage in the Unconnected Legs.

Damage occurring to steel element structures is highly possible due to tearing ruptures, corrosion, or the adoption of sudden loads. The damage has a great effect on their capacity to bear load and the corresponding elongation, as well as the distribution of the stresses in the cross-section of the element. Therefore, in the present research, experimental tests were carried out on 15 specimens of channel steel elements with different damage ratios in the unconnected legs and at different locations along the element's length. Through the test, the load and the corresponding elongation values were obtained for the control and damaged specimens. From the study of the different variables, it was demonstrated that the damage location does not significantly affect the load capacity, with a maximum difference of 1.9%. With the presence of the damage in only one leg at a ratio of less than or equal to 40%, the prediction of the value of the loss in the load is within the safe limit. However, if this ratio increases, there is a defect in calculating the loss in the load as it is greater than the effect of the damage. If there is any damage in the two legs of the channel together, the prediction of the loss of load is within the safe limit, where the loss is less than the effect of the damage ratio. We propose a model that can predict the capacitance of the axial load of steel channel elements through identifying the ratio of damage in the unconnected leg.

Effect of Polymers on Behavior of Ultra-High-Strength Concrete.

The development of ultra-high-performance concrete (UHPC) is still practically limited due to the scarcity of robust mixture designs and sustainable sources of local constituent materials. This study investigates the engineering characteristics of Styrene Butadiene Rubber (SBR) polymeric fiber-reinforced UHPC with partial substitution of cement at 0, 5 and 20 wt.% with latex polymer under steam and air curing techniques. The compressive and tensile strengths along with capillary water absorption and sulfate resistance were measured to evaluate the mechanical and durability properties. Scanning Electron Microscopy (SEM) was carried out to explore the microstructure development and hydration products in the designed mixtures under different curing regimes. The results indicated that the mixtures incorporating 20 wt.% SBR polymer achieved superior compressive strength at later ages. Additionally, the tensile strength of the polymeric UHPC without steel fibers and with 20% polymers was enhanced by 50%, which promotes the development of novel UHPC mixtures in which steel fibers could be partially replaced by polymer, while enhancing the tensile properties.