Key Engineering Materials Vol. 921

Abstract: Treatment of rich chromium effluent is a matter of concern in many leather industries. Nano zero valent iron (NZI) is considered as one of the promising adsorbent materials due to its large surface area. Also, biomaterials have great remediation efficiency because of their surface-active groups such as hydroxyl and carboxyl groups. In this paper, we study the use of nano-bio polymer complex (NBPC) in chromium removal. Batch experiments were carried out in terms of operating medium pH, contact times, initial chromium concentrations, and speed rates. The maximum chromium removal of 88% was observed at pH values 7.0, contact time 30 min, and speed rate 150 rpm for chromium concentration 100 mg/L. The adsorption linear isotherms fitted well to Freundlich’s model compared to Langmuir’s model. Treatment of tannery wastewater through NBPC beads showed a decrease in heavy metal concentrations at equilibrium with removal orders of Mn > Cu > Ni > Cr > Pb > Fe > Cd. The removal efficiency of chromium ions is 52% with specific uptake of 25.6 mg(Cr)/g(NBPC). Results showed a decrease in the organic loads represented in COD, BOD, ammonia nitrogen, nitrate, and phosphorous with removal efficiencies 51.8, 48.6, 66.1, 63, and 43.3%, respectively. The reusability of NBPC beads was studied for three subsequent cycles. Results revealed that the availability of NBPC beads for reuse but with removal efficiencies is less than that of the first cycle. X-ray diffraction, SEM micrograph with EDAX analysis, and FT-IR spectroscopy for NBPC beads were studied for surface characterizations.

Abstract: Concrete industry is one of the largest consumers of natural resources due to its consumption of huge volumes of natural aggregates, which represents around 70% - 80% of the concrete volume. The environmental and economic concern are the biggest challenge that concrete industry is facing. In this research, the issues of environmental and economic concern are addressed by using waste glass as partial replacement of coarse aggregates in concrete. The waste glass was used to replace the coarse aggregates using replacement ratios of 10%, 20%, and 30% by weight. The concrete specimens were tested for compressive strength, splitting tensile strength and flexural strength. Compression tests were carried out at 7 days and 28 days of age while the two other tests were carried out at 28-day age only. The results obtained were compared with those of normal concrete. The results concluded that there is feasibility in using glass wastes in concrete as partial replacement of coarse aggregates.

Abstract: The partial replacement of cement in concrete with the addition of granite Powder and nanosilica can help to increase the performance of cement mortar in concrete. The aim of the article is to investigate the performance of granite powder and nanosilica for the sustainable production of cementitious mortars. Mechanical, physical, and durability properties of these additives were first compared with the properties of cement. Afterward, a series of mortars modified with the addition of granite powder and nanosilica was made. The properties of the fresh mixes and the mechanical properties of the hardened composites were then tested. Finally, based on the obtained results, a cost analysis of the profitability of modifying cementitious composites with granite powder or flyash was investigated. We can conclude, it should be stated that both of these materials can successfully be used for the sustainable production of cementitious composites. This conclusion has a significant impact on the possibility of improving the natural environment by reducing the amount of cement production. More sustainable production of cement-based materials could enable CO₂ emissions to be decreased.

Abstract: This experimental research aims at investigating the possibility of utilizing local glass waste in the production of concrete for construction. Experimental program is conducted to study the effects of using glass powder (GP) obtained by crushing of local glass waste as partial replacement of cement on the fresh and hardened properties of concrete. Five percentages of GP were used: 0%, 10%, 15%, 20%, and 25% by weight of cement. For all concrete mixes, slump test was made for fresh concrete and tests were made for hardened concrete to evaluate compressive strength, splitting tensile strength and flexural strength. The experimental results show that workability increased by increasing GP content. Concrete compressive strength was reduced for all mixes with glass powder, but is improved by time. The positive effect of using GP as cement replacement extends to 20% on concrete tensile strength. The results showed that as the amount of GP increases the flexure strength. The use of 20 % glass powder as cement replacement decreased concrete compressive strength by 3.2% at 56 days, achieved better tensile strength at 28 days, increase flexure strength by 18.6% at 28 days and showed good performance compared to all other mixes.

Abstract: With the increasing interest in energy-efficient building design, building energy simulation programs are increasingly employed in the design process to help architects and engineers decide which design alternatives save energy more. This research is an empirical and analytical study using a ready-made software package to evaluate the energy efficiency performance of building envelopes using recycled waste material. These methods used available environmental alternatives material in the experiment. To verify the results, two practical cases are tested. Validation is examined by comparing experimentally measured data and computational simulation data during the same summer period time. Real cases with small-scale actual rooms that were used to generate data to validate numerical models. The focus of this study is to compare the experimental measured thermal behavior of traditional and waste materials in residential buildings with simulation results. This comparison allows determining the effect of using waste material in southern walls of a residential building at an indoor temperature during hot summer days, in which the measurements took place during June and July. Meanwhile, the results indicated that the indoor temperature of real models was higher than the temperature of simulation models with about 3°C to 6 °C at measuring time (six summer days). This increase is about o 5.4% to 11.8%. The findings also revealed that the use of waste material in the southern wall of a residential building could decrease the indoor temperature by about 0.2 - 3°C degree compared with the traditional material at the same wall. It means that waste materials in southern walls could decrease 0.9% to 4.1% of indoor temperature compared with traditional materials. This study found that the analytical and empirical small-scale models could contribute to determining the usage of waste material at southern walls of residential buildings. Also, the comparison of the results indicates that Design-Builder can predict indoor temperature to achieve thermal comfort with good accuracy and it can be used by researchers and designers to evaluate the thermal performance of buildings.

Abstract: The construction industry has recently focused on the use of sustainable and innovative building materials, which called for the production of many supplementary cementitious materials with concrete to make the concrete produced durable and sustainable. Since high-strength concrete has many advantages other than its high strength, it has recently been used in non-traditional applications after for a long time confined to well-known traditional applications. This study presents the effect of micro Ferrosilicon (FS) and mineral materials on high-strength concrete properties, where silica fume (SF), FS, and metakaolin (Mk) were used as additives to cement.Besides the consistency test, all-ages compressive strength, splitting tensile strength, modulus of elasticity strengthand water permeability were investigated on the produced HSC.Microstructure analyses are carried out by SEM and EDX tests. The results showed a continuous decrease in a slump with the increase in mineral material, however, 15% FS and 15% MK were determined as the optimum percentage of the desired mechanical property. HSC performs up to 88 MPa compressive strength, 7.49 MPa tensile strength, and 39.89 GPa modulus of elasticity, as well as good durability properties. Finally, the high-strength concrete under consideration is suitable for use in both conventional and non-conventional applications and supports sustainable development and infrastructure development.

Abstract: Phase change materials (PCMs) integration into cement mortar is among the new studies of interest regarding modern energy-saving techniques and developing the thermal properties in buildings. This study aims to integrate microencapsulated-PCMs (micro-PCMs) with cement mortar at 0, 5, 10, and 15% to replace natural sand for thermal properties improvement of the building envelope. In addition, the effect of using micro-PCMs on mechanical, thermal properties, and PCMs leakage problems were studied. The cement mortars incorporated with micro-PCMs were investigated by scanning electron microscopy (SEM), thermal conductivity, and mechanical properties as (compressive, flexural, and tensile). The results indicate a decreasing trend of thermal conductivity values with the increase in PCMs content in the cementitious system with the percentages of 11, 21, and 30% for 5, 10, and 15% PCMs, respectively. Similarly, mechanical properties results also confirmed that integrating incorporating mortars with PCMs resulted in the reduction in the compressive strength by 22, 31, and 46%, respectively. Therefore, using the PCMs with cement mortar can build envelope applications to store thermal energy, provide the indoor temperature at a comfortable range, and reduce the consumption energy in buildings.

Abstract: This paper presents an experimental study to investigate the effect of core drilling on the Reinforced Concrete (RC) column capacity. It also discusses how to restore the drilled RC column capacity. The experimental work consists of seven half-scale short rectangular concrete columns with cross section in width and depth equal to 160 and 300 mm, respectively. All specimens have the same column total and clear height which is equal to 1900 and 1300 mm, respectively. On loading at 40% of column load capacity, the core has been taken to stimulate what happens in nature where core is drilled in buildings. The discussion presents the different strengthening techniques for the core drilling zone to restore the un-voided column capacity, strengthen techniques such as using Carbon Fiber Reinforcement Polymer (CFRP) and anchored steel plates. The study showed good agreement of the results. Finally, recommendations are given for the reduction in the RC column load carrying capacity under the effect of core hole.

Abstract: During the last two decades, fiber reinforced polymer (FRP) reinforcing bars for concrete structure has been extensively investigated and a number of FRP bars are commercially available. Using glass fibers and unsaturated polyester resins, steel fiber reinforced polymer composite bars (SFCB) were manufactured and introduced to the commercial market. Lap splice of such bars must be thoroughly investigated. Limitations of steel reinforcement lengths available from the plant (generally 12 m), causing the construction actors to splice the reinforcement. The simplest and easiest way is to make a lap splice, which made overlap by a certain length is called the developing length of lap splice bar. The main objective of this research using the concept of material hybridization, is to investigate the effect of bar diameter after adding fibers & code equation coefficients for best efficient developing length for tensile lap splice in beams under flexure. Nine RC beams were casted with dimensions of (25*40*420) cms and concrete strength of 300 kg/cm². Beams were divided into three groups according to the fiber thickness added to 10 mms’ steel bars. First group contained three beams reinforced with hybrid bars of diameter 12 mms, 10mms steel coated with 2mms fiber. Beam one casted using bars with lap splice of 1.3*50φ, beam two casted using bars with lap splice of 1.3*55 φ & beam three casted using bars with lap splice of 1.3*60 φ. Second group contained three beams reinforced with hybrid bars of diameter 14 mms, 10mms steel coated with 4 mms fiber, beam one casted using bars with lap splice of 50φ, beam two casted using bars with lap splice of 55 φ & beam three casted using bars with lap splice of 60 φ. Third group contained three beams reinforced with hybrid bars of diameter 16 mms, 10mms steel coated with 6 mms fiber , beam one casted using bars with lap splice of1.3* 50φ , beam two casted using bars with lap splice of 1.3*55 φ & beam three casted using bars with lap splice of 1.3*60 φ . Beams were tested under four-point load to create a region of pure flexure stress. Load –deflection curves are presented along with percentage differences. Finally, conclusions were drawn and presented in this paper.