Preparation and Characterization of the Functional Properties of Synthetic Aggregates from Silico-Manganese Slag

A large number of natural aggregates are used in the field of construction materials, resulting in the exhaustion of natural aggregates. Therefore, looking for an alternative will slow down the consumption of natural aggregates. The sintering method not only consumes a lot of energy to prepare aggregates but also produces a lot of pollutants. In this study, silico-manganese (SM) slag was dried, ground into powder, and used as raw material. Solid and liquid alkaline activator methods were used to prepare SM slag non-burning aggregate (SMNA) by the cold bonding method. The effects of grinding time, amounts of solid and liquid alkaline activators, curing temperature, and the amount of added fly ash on aggregate properties were investigated. The aggregate microstructure was characterized by XRD, SEM, and FTIR methods, and the toxic leaching analysis of aggregate was performed. The results showed that with a fixed amount of liquid activator (16.2% wt.) and solid activator (15% wt.) and fly ash (20% wt.), respectively, and curing was performed at room temperature, the aggregate properties were optimal: the bulk density of 1236.6–1476.9 kg/m3 and the water absorption lower than 4.9–5.5%. The apparent density was 1973.1–2281.6 kg/m3, and the bulk crushing strength was 24.7–27.9 MPa. The XRD, SEM, and FTIR results indicated that amorphous gel could be formed from SM under an alkaline activator, improving the aggregate strength. The results of toxic leaching showed that the aggregate prepared from SM exhibited environmentally friendly characteristics. The SMNA was obtained via the simple and low-energy consumption production process, paving the new way toward large-scale utilization of SM.

Preparation of Artificial Aggregate Using Waste Concrete Powder And CO2 Fixed By Microorganisms

High carbon emissions, shortage of natural aggregates and environmental pollution of waste concrete powder (WCP) have become three imperative crises faced by the traditional concrete industry. The waste concrete crushed to prepare aggregates always has poor mechanical properties and low utilization of waste powder. In this paper, WCP was used to prepare artificial aggregates by cold-bonding disk granulation. And a novel approach for strengthening mechanical properties and improving CO2 sequestration of artificial aggregates was proposed based on using microorganisms. The microorganism enhanced the mechanical properties, porosity and microstructure of artificial aggregates. The apparent density, crushing strength and water absorption of artificial aggregates were increased to 2620 kg/m3, 9.1 MPa and 4.8 %, respectively. It showed a denser microstructure because more mineralization products with well crystallization reduced the porosity from 20.98 % to 13.88 %. The CO2 fixation of artificial aggregates increased from 7.39 wt. % to 16.00 wt. % due to the existence of microorganism. The compressive strength of concrete indicated that artificial aggregate could substitute the nature aggregates partially without affecting its strength, and the better rate should be controlled within 50 wt. %. This method has obvious effect on waste resource utilization and CO2 emission reduction, displayed good potential for future applications.

Comparison of Tensile Strength and Fracture Toughness of Co-Bonded and Cold-Bonded Carbon Fiber Laminate-Aluminum Adhesive Joints

The purpose of this work is to compare the co-bonding vs. cold-bonding route on the adhesive joint performance of a CFRP (Carbon Fiber Reinforced Polymer) laminate–aluminum connection. In particular, the overlap shear, tensile strength and Mode I and Mode II fracture toughness will be evaluated. The adhesives for co-bonding and cold-bonding are, respectively, a thermosetting modified epoxy, unsupported structural film and a two-component epoxy adhesive, chosen as representative of applications in the high-performance/race car field. The emerging trend is that, in tensile e Mode I fracture tests, the failure path is predominantly in the composite. Mode II fracture tests instead resulted in a cohesive fracture, meaning that, under pure shear loading, the weakest link may not be the composite. The lap-shear tests are placed midway (cohesive failure for co-bonding and composite delamination for cold-bonding, respectively), probably due to the different peel stress values related to the different adhesive Young’s modulus. The exploitation of the full capacity of the adhesive joint, hence the possibility of highlighting better, different performances of co-bonding vs. cold-bonding, would require consistent improvement of the out-of-plane strength of the CFRP laminate and/or to someway redistribute the peel stress on the bondline.

Computational Study on Surface Bonding Based on Nanocone Arrays

Surface bonding is an essential step in device manufacturing and assembly, providing mechanical support, heat transfer, and electrical integration. Molecular dynamics simulations of surface bonding and debonding failure of copper nanocones are conducted to investigate the underlying adhesive mechanism of nanocones and the effects of separation distance, contact length, temperature, and size of the cones. It is found that van der Waals interactions and surface atom diffusion simultaneously contribute to bonding strength, and different adhesive mechanisms play a main role in different regimes. The results reveal that increasing contact length and decreasing separation distance can simultaneously contribute to increasing bonding strength. Furthermore, our simulations indicate that a higher temperature promotes diffusion across the interface so that subsequent cooling results in better adhesion when compared with cold bonding at the same lower temperature. It also reveals that maximum bonding strength was obtained when the cone angle was around 53°. These findings are useful in designing advanced metallic bonding processes at low temperatures and pressure with tenable performance.

A review on the effects of artificial light weight aggregate in concrete

The disposal problem of industrial by-products like fly ash, heavy metal sludge, sewage sludge etc. are increasing day by day. To use by-products in large volume the applications like embankment fill or aggregate replacement material should be considered for sustainable development. This study is focused on properties of artificial light weight aggregate on concrete and the effect of cold bonded light weight aggregate on concrete through partial and complete replacement of coarse aggregates. Artificial Lightweight aggregate can be produced by nodulizing the by-product for example fly ash in a pelletizer with a proportionate quantity of water, cement and further hardened by cold bonding or sintering. Due to the impact of earth quake forces all over the world, the need for light weight structural design is increasing presently, as it reduces mass of the structure. The concrete produced is light weight in nature and has added the benefit of reducing overall cost, especially in transportation and placing etc. it has its own advantages like reduced dead load, and thus economic structures, high sound absorption and good fire resistance. Keywords—Artificial light weight aggregate, cold bonding, Fly ash, Fly ash aggregate, Pelletization, and Sintering.

Optimization of Binder for Improving Strength and Shatter Index of Briquettes for BOF Dust using Design of Experiments

Effectiveness of Recycling of steel plant waste is very much dependent on agglomeration technique. Sintering, pelletization and briquetting are some of the techniques which are frequently used for waste utilization. Aim of this study is to prepare composite briquettes by cold bonding technique, by which phsico-chemical changesoccurred at room temperature or low temperature. Two binders are mixed in proportion to achieve the required properties specifically strength and shatter index. The design of experiments is used to find the proper combination of binders to get the optimum value of properties. Experimental work for the same is carried out in such a way that minimum number of experiment can give output as desired. For this ‘Design of Experiment’ methodology is applied to select the runs of experiment. After the selection of orthogonal array and experiment combinations, Taguchi technique is used with two variable (starch and molasses) and three levels (2.5%, 5% and 7.5% of each) i.e. L9 Array to analyze the results. Minitab15 software is used. Conclusion and comments are based on the same.