ASTM Requirements Research Articles

The Characteristics of Solid Soap with Varied Additions of Kefir Cheese Whey

Background: Kefir cheese whey is a product of fermented cheese whey wastewaste. Kefir cheese whey has been known to contain Lacofferin. Lactoferrin functions as an antimicrobial. Methods: This study focuses on producing solid soap from kefir cheese whey. The saponification reaction of saponification reaction of coconut and palm oil, with Natrium Hidroxide with kefir cheese whey, initiated the solid soap production. Results: show that all formulae of solid soap from kefir cheese whey showed good physicochemical characteristics, pH 10.09–10.98 (ASTM requirement 9-11), foam content 10.98-12.89. Soap Kefir cheese whey can be concluded that all formulas meet the requirements that all formulas meet the requirements established by SNI 3532:2016 and ASTM D 2022. Conclusions: The Best formula for solid soap variant kefir is 100 % whey. Thus, the giving of kefir whey is recommended for manufacturing kefir soap. It suggests that soap kefir cheese whey is recommended for use as an antibacterial agent in the manufacture of solid soap.

Assessing the mechanical properties of out-of-specification additive manufacturing Ti-6Al-4V powder recycled through field-assisted sintering technology (FAST)

A gas atomised Ti-6Al-4V powder, classified as out-of-specification for additive manufacturing (AM), was consolidated via Field-Assisted Sintering Technology (FAST). Fully dense 250 mm diameter discs with lamellar or bimodal microstructures were produced by FAST processing either above or below the β-transus temperature. Static and dynamic mechanical properties were assessed by testing full-size specimens in the ‘as-FAST’ condition. Material from both processing conditions exceeded the ASTM Ti-6Al-4V powder metallurgy requirements for yield/tensile strength and elongation. Furthermore, material from the edge of the disc processed below the β-transus temperature meets ASTM requirements for wrought Ti-6Al-4V. Fatigue performance also compared favourably with conventionally processed Ti-6Al-4V. This work establishes that surplus AM powders can be successfully recycled via the one-step FAST process and provides confidence that this ASTM-grade material can be used in a range of applications under both static and dynamic loading, which will improve the sustainability credentials of the AM sector.

One-stage microwave-assisted activated carbon preparation from Langsat peel raw material for adsorption of iron, manganese and copper from acid mining waste

This study describes the efficacy of microwave technology for the preparation of an activated carbon from Lansium domesticum peel as an adsorbent to adsorb Fe, Cu, and Mn from acid mine waste. In contrast to the conventional pyrolytic carbonization technique, the described method demonstrated several unparalleled advantages, including superior energy efficiency and remarkably rapid processing. The reported microwave irradiation method was able readily to achieve a morphology and extensive surface area similar to that of a sample produced using the traditional pyrolytic carbonization method for 2 hours, and this was accomplished in just 10 minutes. The activated carbon obtained was characterized using SEM-EDX, BET-BJH, and proximate test and applied to adsorb metal ions from acid mine waste to evaluate the isothermal adsorption model. The best power for activated carbon production was 400 watts for 10 minutes, which met the requirements of ASTM D 4607 for determining the iodine value of activated carbon. Optimal mass for adsorbing Fe, Cu, and Mn from acid mine waste was 4 grams with the removal percentages of 94.08%, 83.69%, and 90.67%, respectively. BET surface area was 1367.0385 m2/g along with a BJH cumulative volume and an average pore diameter of 1.112 cm3/g and 2.25 nm, respectively. This suggests that it possesses mesoporous characteristics and adheres to the Langmuir model during the adsorption process, signifying monolayer adsorption. Meanwhile, kinetics followed the pseudo-second-order rate equation.

Development and Airworthiness Certification of the Ti6Al4V Inlet Casing Inner Forging

The inlet casing inner has manufactured using Ti-6Al-4V alloy through a closed die-forging route. It undergoes cyclic loads in addition to operating in extreme conditions in high-temperature environments. The demanding mission requirement of these engines necessitates the inlet casing inner to be flawless throughout its life cycle while retaining its structural integrity. It makes the qualification for airworthiness of the casing, a daunting task. In addition, the qualification tests also help to evaluate the design and manufacturing processes (closed die forging) of the inlet casing inner. The tests also provide data for further improvement of the inlet casing inner in terms of strength and fatigue life. It helps to ensure that the inlet casing inner will be able to perform as expected throughout its operational life. All the batch and consolidated test results comply with the relevant ASTM, MIL standards, and test schedule requirements.

The effects of zircon particles on the mechanical and morphological properties of glass fibre reinforced epoxy composite

Recent studies have focused on improving the mechanical properties of thermosetting composites that seem to include inorganic nanoparticles dispersed throughout the matrix material. This study investigates the mechanical properties, crystallographic and morphological study of epoxy composites when ball-milled zircon filler is incorporated into epoxy at weight percentages of 0, 5, 10, and 15(wt%). Zircon nanoparticles and epoxy resin are blended using an ultrasonic liquid technique, and then compression moulding is used to make the composite materials. Using theoretical and calculated densities (g/cm3), the volume fraction of voids (%) in the prepared composites is estimated. The Mechanical tests were done in accordance with ASTM requirements. The average zircon particle size was found to be 73.26 nm using field emission scanning electron microscopy. The chemical composition, crystalline structure and the crystalline size (2.1 nm) of zircon particle was determined using X-Ray diffraction. In comparison to pure glass fibre reinforced epoxy polymer, the 10 wt% zircon particle's tensile strength, tensile modulus, flexural strength, and flexural modulus are 33.33%, 12.56%, 32.88%, and 15.74% higher, respectively. Strain energy for tensile test is 82.96%, elongation at break is 53.52% higher and strain energy for flexural test is 52.38%, elongation at break is 14.67% higher than pristine composites. As a comparison to neat sample, Shore "D" hardness at 10 wt percent ZrSiO4 is 5.88% harder, and Izod average impact strength (J/mm) is 63.20% greater. Pullout of fibre, damaged interfaces, filler dispersion and voids are identified using field emission scanning electron microscopy. Zircon filler of 10 wt% inclusion on epoxy with E-glass fibre reinforcement reportedly improves characteristics than other proportions, especially better improvement than plain sample. Because of this, the mechanical and structural properties of developed composites are enhanced by this approach. This research proposal would lead to a special combination of ZrSiO4 inclusion and E-glass fibre reinforcement in epoxy composites for aircraft structural applications.

Comprehensive studies of the influence of superficial strengthening with the FRCM system on the load‐bearing capacity and deformability of AAC walls

AbstractThis article presents the results of tests on walls made of AAC (autoclaved aerated concrete) strengthened with the FRCM system. The effect of the applied strengthening was determined based on the results of tests on masonry models subjected to compression, diagonal compression and shear. Models of walls without strengthening, strengthened on one and two sides were tested. The research models were built of masonry elements made of autoclaved aerated concrete (AAC) SOLBET OPTIMAL 4/600. The walls were erected on a system thin‐layer mortar, class M5, without filling the head joints. PBO fiber meshes embedded in a mineral matrix were used as superficial reinforcement. The walls were strengthened by applying the PBO‐MX GOLD MASONRY system mortar to the side surfaces of the models and the PBO‐MESH GOLD 22/22 mesh was embedded in it, and then the top layer of the PBO‐MX GOLD MASONRY system mortar was applied. The compressive strength test was performed on 18 models in accordance with the requirements of the PN‐EN 1052‐1: 2000 standard. In the case of compression, additional tests were performed on models weakened by a cut imitating cracking. The diagonal compression test was performed on 18 models in accordance with the requirements of ASTM E519‐81 standard. The shear load test was performed on 27 models in accordance with the requirements of the PN‐EN 1052–3: 2004 standard. A clear increase in load capacity in each type of test was noted in models strengthened on two sides. In models strengthened on one side, the positive effect of strengthening was observed only by increasing the deformability of the wall. Regardless of the test type, the use of surface reinforcement allowed for smoother behavior of the test models after the loss of load capacity in relation to models without strengthening.

FLEXURAL STRENGTH CHARACTERISTICS OF PAWPAW LEAF ASH AND BAMBOO LEAF ASH BLENDED CEMENT CONCRETE

This research focuses on flexural strength characteristics of pawpaw leaf ash and bamboo leaf ash blended cement concrete. Several tests were carried out, according to BS and ASTM requirements to determine the physical and mechanical properties of pawpaw leaf ash and bamboo leaf ash blended cement concrete, investigate the effects of curing age on flexural strength characteristics of pawpaw leaf ash and bamboo leaf ash blended cement concrete and examine the effects of percentage replacement of cement with pawpaw leaf ash and bamboo leaf ash blended cement concrete on flexural strength characteristics. A total of 60 cubes were cast, cured in water for 7, 14, 21 and 28days. Test results showed that the flexural strength of the concrete cubes increases with an increase in the curing age and decreases with increasing percentage replacement of cement with pawpaw leaf ash and bamboo leaf ash. The optimum replacement level of pawpaw leaf ash and bamboo leaf ash was obtained to be 5%. The study concluded that concrete containing the cement blends of cement and Pawpaw leaf ash and bamboo leaf ash at a replacement level of 5% is only recommendable for use in light concrete works construction.

A Review of Advances in Peat Soil Stabilisation Technology: Exploring the Potential of Palm Oil Fuel Ash Geopolymer as a Soil Stabiliser Material

This study aims to highlight the latest developments in the field of peat soil stabilisation technology via chemical stabilisation. The review examines the use of traditional stabilisers such as OPC and various non-traditional stabiliser materials, i.e., Palm Oil Fuel Ash (POFA)-OPC blends, chemical solutions, and geopolymer materials, to enhance the Unconfined Compressive Strength (UCS) characteristics of peat soils based on the ASTM D 4609 requirements. OPC, POFA-OPC blends, and alkaline solutions mostly produced stabilised soil samples that fell short of the ASTM requirements. Existing studies on the use of waste-derived geopolymers to treat peat soils are limited, while the use of POFA geopolymer materials has mostly focused on the improvement of clayey and silty soils. The results of soil stabilisation with geopolymer were very encouraging, as the strength gains were in line with the ASTM soil strength requirements. As a result of this review, it can be concluded that POFA geopolymer is a viable soil stabiliser material with the addition of Ground Granulated Blast Furnace Slag, and that the use of POFA-GGBFS geopolymer to enhance the strength properties of peat soils should be investigated. Doi: 10.28991/CEJ-2023-09-08-017 Full Text: PDF

Investigation of low-percentage graphene reinforcement on the mechanical behaviour of additively manufactured polyethylene terephthalate glycol composites

The current work investigates the influence of graphene on the mechanical properties of additive-manufactured polyethylene terephthalate glycol (Prince Edward IslandTG) composites. To this end, the graphene content is varied by 0.02 wt.%, 0.04 wt.%, 0.08 wt.%, and 0.1 wt.% to obtain different compositions of PETG/graphene composites. The filaments were prepared by mixing the PETG pellets and graphene flakes into the required quantity. Further, the mixture is extruded using a single screw extruder into small filaments with a 1.75 mm diameter. Using fused deposition modelling (FDM), the specimens were 3D printed following ASTM requirements. The fabricated PETG/graphene specimens are assessed for their mechanical properties, such as tensile, compression, flexural and impact characteristics. Finally, the fractography of the tested specimens is analysed using a scanning electron microscope (SEM). The experimentation of PETG/graphene composites reveals that the optimum mechanical properties can be achieved when PETG is reinforced with 0.04 wt.% of graphene. As opposed to virgin PETG, an increment of 89.71%, 81.76%, 21.60%, and 81.25% is witnessed in the tensile, compression, flexural, and impact strengths of the PETG/0.04 wt.% graphene composite. The outcome of this work is believed to pave the way for broadening the applications of graphene-based composites in electromechanical and smart structure engineering domains.

Recycling of bypass cement kiln dust in the production of eco-friendly roof tiles

Most of the research of building materials companies at present focuses on recycling waste to minimize the cost of their products and for the safe disposal of these wastes. In this work, the by-pass cement kiln dust (BCKD), the dust that is discarded from the kiln system was used for the preparation of roof tiles. It is partially used to substitute clay in percentages from 5% up to 25%. to prepare roof tiles abiding by ASTM C1167 for two objectives, the safe disposal of waste and the production of low-cost roof tiles. The raw materials were assessed by particle size analysis, XRD, and XRF. The mud was poured into moulds with dimensions of 150 * 30 * 25 mm3 and pressed under a pressure of 10 MPa then dried. The dried samples were fired to temperatures 1000, 1100, and 1150 °C with a soaking time of one hour for each temperature. The linear firing shrinkage, water absorption, bulk density, and breaking strength were measured to determine the properties of the fired specimens. The initial rate of absorption and runoff properties were also determined for the optimal samples. The results showed that samples containing 8% and 12% of BCKD waste that fired at 1100 °C and 1150 °C had cold water absorption of 14% and a saturation coefficient of 0.85, both of which were below the maximum values of the standard limits. Furthermore, the measured breaking strength of about 2700 N was much higher than the necessary minimum value. The results showed that samples met the requirements of ASTM 1167 for clay-type roof tiles containing 8% BCKD waste and fired to 1100 °C. For economic and environmental benefits, 1100 °C firing temperature is recommended than 1150 °C. The initial rate of absorption was found to be 2.8 kg.m−2 and the runoff properties were found to be 0.02 mg.l−1, 7.53, 110.5 mg.l−1 for total dissolved solids, pH and total solids respectively.

Performance of Concrete Developed by Enhanced Gradation of Natural Fine River Sands by Partial Replacement of Waste Quarry Dust

As construction activity continues to increase on a daily basis, the demand for fine and coarse aggregates is also rising. However, relying on a few sources would quickly deplete the natural sources of aggregates. In Lahore, Punjab, Pakistan, costly coarse pit sand from northern areas is used for concrete, as the local river sands (Ravi and Chenab) are fine and do not meet ASTM specifications for fine aggregates. To alleviate the pressure on one source, it is necessary to improve the gradation of natural river sand by utilizing quarry dust obtained during the process of crushing rock into crushed stones. This study conducted detailed experimental work to enhance the gradation of natural river sand by adding normalized quarry dust. Concrete mixes with three strengths of 21 MPa, 28 MPa, and 35 MPa were prepared by partially replacing natural river sand with quarry sand. Workability and hardened concrete properties were evaluated for all mixes, and cost analysis was performed for 28 MPa concrete. The results were compared with control concrete made with coarse pit sand. When river sand was enhanced by combining 40% river sand and 60% normalized quarry dust, the resulting sand met ASTM requirements. Furthermore, when some fines were removed from river sand and replaced with 50% normalized quarry dust, the sand also met ASTM grading requirements. The compressive and flexural strengths of concrete made with enhanced sand gradation increased by 10–25% and 9–17%, respectively, for 28 MPa concrete compared to the control concrete. Cost analysis showed that 28 MPa concrete made with enhanced natural river sand gradation was 8.6% more economical than concrete made with coarse pit sand.

Performance of Cement–Fly Ash Masonry Mortar with Sand from Mine Overburden as an Environment-Friendly Alternative to Conventional Fine Aggregate

Abstract There is an increasing demand for fine aggregate for use in concrete and mortar. In this study, sand extracted from mine overburden from two locations through the wet-sieving process was used as alternative fine aggregate in mortar. The behavior has been benchmarked with mortar using conventional river sand and coarse and fine sand obtained from crushed stone. Combination mortar with ordinary portland cement and Class C fly ash was used as a binder. The sand-to-binder ratio was fixed as 3, as per ASTM C270-19ae1, Standard Specification for Mortar for Unit Masonry, whereas the fly ash–to–cement ratio was varied from 0.75 to 3. The water required to achieve a constant flow value of 110 ± 5 % was determined. The water retention of fresh mortar and dry density, compressive strength, and drying shrinkage of hardened mortar were determined. Mortar mixtures with sand from mine overburden with a fineness modulus of 2.36 conformed to the water retention requirement of ASTM C91/C91M-18, Standard Specification for Masonry Cement, whereas very fine sand did not satisfy. Masonry mortar with different mixture proportions and fineness modulus of fine aggregate resulted in a range of compressive strengths, satisfying a wide range of mortar designations as per ASTM C270-19ae1, BS EN 998-2, Specification for Mortar for Masonry - Part 2, and IS 2250, Code of Practice for Preparation and Use of Masonry Mortars. For mortar with a fine aggregate of different origins (river sand, crushed stone coarse sand, sand from overburden with fineness modulus 2.67, 3.01, and 2.36, respectively), a marginal variation in drying shrinkage across strength was observed. The maximum drying shrinkage of the higher fly ash–to–cement ratio of the mixture with finer sand was 1,600 microstrain.

A study on oxidation stability improvement of a palm oil‐derived biodiesel by a synthetic antioxidant

AbstractBiodiesel, an alternative for conventional diesel, can be produced from renewable resources such as vegetable oils. One of the most crucial characteristics of biodiesel fuel is oxidation stability, which significantly influences the stability of biodiesel during prolonged storage. In fact, biodiesel is less resistant against oxidation than the conventional diesel. In order to transcend this problem, additives are employed. This work uses the Rancimat technique to examine the effects of various antioxidants additives on the oxidation stability of different produced biodiesel. The oxidative stability of biodiesel produced from rapeseed, palm, sunflower and waste cooking oil were evaluated after assuring that the properties of used oils and produced biodiesel complied with the ASTM requirements. Palm biodiesel was selected since it showed the highest oxidation stability of 1.32 h. The experimental findings demonstrated that the two antioxidants investigated (phenolhydrazine and thiamine hydrochloride) are boosting oxidation stability, however phenolhydrazine is providing a higher oxidation stability than thiamine hydrochloride. The optimal amount of phenolhydrazine was found to be 2550 ppm and resulted in an oxidation stability of 6 h. This great enhancement of oxidation stability (454%) ascertained that phenolhydrazine is a strong antioxidant to be utilized in order to enhance shelf life of natural source‐derived biodiesels. The mentioned antioxidant was not yet studied in literature which confirms the novelty of our work.

Manufacturing and Characterization of Polymer Concrete with Aggregate from Sand, Egg Shell and Sugarcane Waste with Epoxy Resin Binder as Sound Absorber

Environmentally friendly polymer concrete by utilizing waste has been widely developed, one of which is sugarcane fiber waste and egg shell powder. Utilization of this waste is not optimal, for that by being used as a filler in polymer concrete, it is expected that it will have a higher economic value. This study was to determine the composition of the epoxy resin binder and the mechanical characteristics of polymer concrete fabricated using sugarcane fiber waste with an epoxy resin adhesive. Variations in composition made of sand, egg shells (1 : 1) or (50 g : 50g), bagasse waste 0%, 1%, 2%, 3%, 4% and 5% of the total weight. Epoxy resin composition variation of 20%, 25% and 30% of the total weight of sand and egg shells. Then carried out the characteristics in the form of density test, water absorption, porosity, compressive strength and tensile strength. From the test results, the characteristics of polymer concrete have optimum values, namely density (1.76 g/cm3), water absorption (4.04%), porosity (5,252%), compressive strength (26,27 MPa), tensile strength (4,06 MPa). Of the three samples, the best in the A5 sample with a sound absorption coefficient of 0.237 met the requirements of ISO and ASTM C.384.

A novel Artificial Neural Network-based model for predicting dielectric properties of banana fiber filled with polypropylene composites

The objective is focusing on the prediction of dielectric properties of the polypropylene composites reinforced with banana fiber using an Artificial Neural Network (ANN). To prepare the composites in accordance with ASTM requirements, randomly oriented banana fibers were combined with polypropylene at volume fractions of 20%, 30%, 40%, and 50%. For these composites, the impedance analyzer was used to determine dielectric characteristics such as the dielectric constant, tan δ, and ac conductivity. To estimate the dielectric properties, an artificial neural network is used with a supervised training strategy. The data set was assembled using ReLU, sigmoid, and tanh, three activation functions. Forecasting the outcome variables used temperature, frequency, filler content, and polymer content as input factors. Comparing the model utilizing ReLU to the other two activation functions, the MSE value was 0.32, and the R2 value was 0.98. Dielectric parameter values from both experiments and ANN modeling show a similar pattern. The dielectric properties of fiber-reinforced polyester matrix composites can be accurately predicted using ANN, reducing the need for manual intervention.

Performance, emissions, and combustion in turbocharged diesel engines: The effect of rapeseed oil biodiesel-diesel blends

The need for sustainable alternative fuels is becoming increasingly urgent because to the rapidly expanding demand for automobiles and the growing concerns over the fossil fuel diminution. This research looks into how biodiesel, specifically blends made from rapeseed oil (RSO), can fill this new need. The RSO is created through transesterification, which yields a biodiesel with characteristics that meet ASTM requirements. In a 5.1 kW, single-cylinder, turbocharged Diesel engine (Turbo-DE), the performance, emissions, and combustion (P-E-C) characteristics of several RSO-diesel blends (B20, B40, B60, and B80) are examined and contrasted with those of pure diesel. According to the findings, brake thermal efficiency slightly decreases as biodiesel proportion in the blend rises. The environmental advantages of these blends are offset by a sizable decrease in smoke, CO, and hydrocarbon emissions. On the other hand, greater biodiesel ratios result in higher emissions of NOx and CO2. The thermal efficiencies of the brakes for diesel, B20, B40, B60, and B80 blends were found to be 29.3%, 28.6%, 27.9%, 27.2%, and 26.9%, respectively, in the detailed results. While smoke emissions decreased from 55% (diesel) to 40% (B80), NOx emissions ranged from 1556 ppm (diesel) to 1718 ppm (B80). The B20 blend?s combustion characteristics closely resemble those of diesel, with maximum cylinder pressures and ignition delay of 78 bar, 73 bar, 20%, and 18%, respectively, for diesel and B20. These results offer a good starting point for additional investigation into sustainable alternative fuels by shedding light on the prospective performance and ecological impact of biodiesel-diesel mixes.

Valorization of unmodified, filter-pressed bauxite residue as a precursor for alkali activated inorganic polymers in a one-part mixing process

The valorization of bauxite residue faces severe challenges arising from its unreactive chemistry and ecotoxicity. The construction sector is widely considered the most viable option for the large-scale consumption of bauxite residue to mitiate its continued global accumulation. However, the use of bauxite residue as a supplemetary cementitious material in concrete is limited by its chemical composition and the degradation it causes in the structural properties. Alkali activation of bauxite residue is an alternative technique to produce construction materials, but conventional methods require either high-temperature calcination of the bauxite residue or the use of large proportions of other precursors to form strong alkali activated materials, adding significant cost. This has stymied commercial efforts to valorize bauxite residue. In this study, an alternative methodology is showcased to alkali activate bauxite residue in its filter-pressed form, eliminating the need for drying and calcination. This is the first alkali activation process to utilize high content of bauxite residue (>70%) without drying and milling, offering a substantial reduction in valorization costs and complexity. Alkali activated materials composed of 80% bauxite residue were produced that exceed 11 MPa in strength, meeting the ASTM requirements for interior bricks. The microstructure was characterized by mercury intrusion porosimetry and isothermal nitrogen adsorption. The alkali activation pacified the trace metallic pollutants in the bauxite residue and the leachate meets surface water standards. This methodology presents a unique avenue to valorize bauxite residue at a large scale as a construction material without cost-prohibiting pretreatment steps.

Effects of silane‐modified nano‐CaCO3 particles on the mechanical properties of carbon fiber/epoxy (CF/EP) composites

AbstractIn this study, the effects of silane‐treated nano‐CaCO3 particles on the flexural, Mode‐I, Mode‐II and interlaminar shear strength (ILSS) properties of carbon fiber/epoxy composites are investigated experimentally. The surface of nano‐CaCO3 particles is treated with a silane coupling agent, namely, (3‐Glycidyloxypropyl) trimethoxysilane (GPTMS). Three‐point bending, double cantilever beam (DCB), end‐notch flexure (ENF), and short beam shear (SBS) tests are carried out on the prepared composite specimens according to the relevant ASTM requirements. The results show that with the dispersion of 5 wt% silane‐treated nano‐CaCO3 particles the flexural modulus, flexural strength, Mode‐I fracture toughness, Mode‐II fracture toughness, and ILSS values can be enhanced by 16.8%, 13.6%, 25.7%, 19.6%, and 19.8%, respectively, compared to reference composites. The storage modulus is also increased by about 15.3% with the silane‐treated nano‐CaCO3 particles. The silane‐treated nano‐CaCO3 particles had no significant effect on the glass transition temperature of the composites.

Fatigue Fracture of Aluminum Wires in High-Voltage Electrical Cables in Alaska

Several wires in aluminum conductor cables fractured within 5–8 years of, service in Alaskan tundra. The cables were comprised of 19-wire strands; the wires were aluminum alloy 6201-T81. Visual and metallographic examinations of the cold-upset pressure weld joints in the wires established that the fractures were caused by fatigue loading attributable to wind/thermal factors at the joints. The grain flow at the joints was transverse to the wire axis, rendering the notches of the joints sensitive to fatigue loading. An additional contributory factor was intergranular corrosion, which assisted fatigue crack initiation/propagation. The failure was attributed to the departure of conductor quality from the requirements of ASTM B 398 and B 399, which specify that “no joints shall be made during final drawing or in the finished wire” and that the joints should not be closer than 15 m (50 ft). The failed cable did not meet either criterion. It was recommended that the replacement cable be inspected for strict compliance to ASTM requirements.

Towards greener one-part geopolymers through solid sodium activators modification

This paper investigates the influence of various solid activators and their mixing parameters on the physical, mechanical and microstructural characteristics of greener one-part geopolymers (OPG) based on high calcium fly ash. The high calcium fly ash that has rarely been explored was utilised to develop OPG in this study. The anhydrous sodium metasilicate (Na2SiO3) with negative environmental impact propelled the partial replacement of Na2SiO3 with sodium hydroxide (NaOH) and sodium carbonate (Na2CO3). Two sets of high calcium fly ash OPGs were developed: (1) the MH-OPG comprised Na2SiO3 and NaOH; (2) the MC-OPG comprised Na2SiO3 and Na2CO3. The optimal MH-OPG (73 MPa) and MC-OPG (75 MPa) exhibited superior compressive strength, higher than the minimal requirement (>28 MPa) of ASTM C150/C150M-18 for construction binder material. Various solid alkali activators triggered different reaction mechanisms, yielding distinctive reaction products that contributed to strength growth. The sodium calcium aluminosilicate hydrate ((N,C)-A-S-H) gel was developed in MH-OPG, whereas the sodium carbonate hydrate, sodium aluminosilicate hydrate (N-A-S-H) and calcium aluminosilicate hydrate (C-A-S-H) binding phases were developed in the MC-OPG. Although Na2CO3 reduced the water demand, improved the fluidity and setting time, the MC-OPG was more sensitive to the alteration of mixing compositions, suggesting a tougher performance control during field application than the MH-OPG. The total embodied carbon (EC) of MC-OPG was lowered by 15.4% compared to that of MH-OPG. The embodied carbon index (ECI) of MH-OPG and MC-OPG were 81.3% and 84.7% less than that of OPC products. This work suggests that substituting Na2SiO3 with NaOH or Na2CO3 effectively produced a greener construction material without compromising mechanical strength.