Minimum Strength Research Articles

Higher order theory of quasi-isodynamicity near the magnetic axis of stellarators

The condition of quasi-isodynamicity is derived to second order in the distance from the magnetic axis. We do so using a formulation of omnigenity that explicitly requires the balance between radial particle drifts at opposite bounce points of a magnetic well. This is a physically intuitive alternative to the integrated condition involving distances between bounce points, used in previous works. We investigate the appearance of topological defects in the magnetic field strength (puddles). A hallmark of quasi-isodynamic fields, the curved contour of minimum field strength, is found to be inextricably linked to these defects. Our results pave the way to construct solutions that satisfy omnigenity to a higher degree of precision and also to simultaneously consider other physical properties, like shaping and stability.

Advanced Design for Experimental Optimisation of Physico-Mechanical Characteristics of Sustainable Local Hemp Concrete

The meaning of technological progress is to produce economic development and to increase the level of personal comfort. Sustainability can only be achieved if, at the microsystem level as well as at the macrosystem level, the secondary effects of the activities undertaken by people on the environment are in a state of neutrality compared to the impact they can produce on natural conditions. This neutrality can be intrinsic or can be achieved through coercive and compensatory measures. If we take into account the production of carbon dioxide that accompanies a product from the stages of conceptualisation, design, procurement of materials, execution, operation, maintenance, decommissioning and recycling the waste produced at the end of use, then nothing can be sustainable in pure form. Nevertheless, there are products whose production, both as a raw material and as a technological process, can be neutral in terms of carbon emissions. Moreover, they can even become carbon negative over time. This is also the case with eco-sustainable hemp concrete, whose capacity to absorb carbon dioxide starts from the growth phase of the plant from which the raw material is obtained and continues throughout the existence of the constructed buildings. Not only does it absorb carbon dioxide, but it also stores it for a period of at least 50 years as long as the construction is guaranteed, being at the same time completely recyclable. However, in order to obtain an optimal mixture from the point of view of raw material consumption, represented by industrial hemp wood chips and the binder based on lime and cement, multiple experiments are necessary. The study presented in this work is based on the use of an advanced method of experimental planning (design of experiments method), which makes possible the correlation between the values obtained experimentally and the algorithm that generated the matrix arrangement of the quantities of materials used in the recipes. This approach helps to create the necessary framework for parametric optimisation with a small number of trials. Thus, it is possible to obtain the mathematical law valid within the minimum and maximum limits of the studied domain that defines the characteristics of the material and allows the achievement of optimisation. The material is thus designed to satisfy the maximum thermal insulation requirements that it can achieve depending on a certain minimum admissible compressive strength.

Mechanical properties and durability of concrete containing coal mine waste rock, F-class fly ash, and nano-silica for sustainable development

Natural resources such as river sand and rock used for producing concrete tend to be depleted. Thus, it is necessary to find a new material for substituting the natural aggregate in concrete production. Waste materials such as coal mine waste rock, if these wastes are not treated properly, they negatively affect the environment and human health. Therefore, utilizing waste rock from coal mining to partially substitute aggregate in concrete manufacturing for sustainable development is urgent. In this study, crushed sand from coal mine waste rock (CSM) has partially replaced river sand and combined with F-class fly ash (FFA) and nano-silica (NS) to produce concrete with a minimum compressive strength of 35 MPa. Specifically, 40% of cement was replaced by 38% of FFA and 2% of NS, and river sand (RS) was replaced by CSM at contents of 0%, 10%, 20%, 30%, 40%, and 50%. Mechanical properties, durability, and environmental impact were conducted to evaluate the application of CSM in concrete for sustainable development. The results showed that the synergistic effects of fly ash and nano-silica in concrete helped CSM more environmentally friendly. The mechanical properties and durability of concrete using CSM were close to those of normal concrete using conventional aggregates with the required compressive strength of 35 MPa. The use of mine waste in concrete production has shown its effectiveness in replacing traditional aggregates (river sand), which can minimize environmental impact for sustainable development.

Impact of Compression Casting Technique on the Mechanical Properties of 100% Recycled Aggregate Concrete

The research work presented in this manuscript focused on the comparative examination of the influence of the Compression Casting Technique (CCT) and the conventional casting method (i.e., compaction through vibration) on the performance of 100% Recycled Aggregate Concrete (RAC). The minimum target compressive strength of 100% RAC was 15 MPa keeping in view its application in the manufacturing of load-bearing concrete masonry units. A total of 28 concrete compositions were prepared by varying the coarse to fine aggregates ratio (i.e., 70:30 and 60:40), cement content (10% and 15%) by weight of total aggregates, casting technique, and applied pressure for compression casting (i.e., 25, 35, and 45 MPa). The concrete compositions were tested to determine their density, compressive strength, Elastic Modulus (EM), and Ultrasonic Pulse Velocity (UPV). For comparison, samples of Natural Aggregate Concrete (NAC) were also tested for the same properties. The results highlighted the positive impact of CCT on the properties of 100% RAC. The compressive strength and EM of fully RAC was increased by 20–80% and 15–50%, respectively, by changing casting method from vibration to CCT. At casting pressure of 35 MPa and 15% cement, compressed 100% RAC exhibited compressive strength higher than vibrated NAC. The UPV value exhibited by 100% RAC was increased by changing the casting technique. The analytical models were proposed using regression analysis of experimental results to predict compressive strength and EM of compressed 100% RAC and NAC. These proposed models were evaluated using statistical parameters, i.e., average absolute error (AAE) and mean (M) and found to be able to predict the compressive strength and EM of RAC with reasonable accuracy as compared to the analytical models already existing in the literature. This study finally concluded that through CCT, 100% RAC with low cement content could achieve minimum target compressive strength of 15 MPa. The development and use of compressed load-bearing 100% RAC construction units would help to achieve sustainability in construction.

Photo-induced photoacoustic streaming and pineapple peel extract as final irrigant on extrusion bond strength of root filling material to canal wall.

Photon-induced photoacoustic streaming (PIPS) with pineapple peel extract (PPE) and ethylenediaminetetraacetic acid (EDTA) as a final endodontic irrigant on the push-out bond strength (PBS) of root filling material to conventional irrigation NaOCl with EDTA. An in vitro study at Dar Al Uloom University was conducted over three months. Root canal preparation was performed. Based on final irrigation, all the specimens were divided randomly into four groups (n=10) Group 1: 2.25% NaOCl+ 17% EDTA (control), Group-2: 2.25% NaOCl+PIPS + 6.25% PPE, Group-3: 2.25% NaOCl+PIPS + 17% EDTA, Group-4: 2.25% NaOCl + 6.25% PPE. Canals were obturated and sealed with AH Plus sealer. Root sectioning was performed at 1mm thickness and PBS testing was performed using the universal testing machine. The debonded samples were analyzed for failure mode. ANOVA compared the means and standard deviations (SD) of all investigated group. Assessment of multiple comparisons was performed using Tukey's post hoc test. The maximum PBS was demonstrated by the coronal section of Group-2 (2.25%NaOCl +PIPS+6.25%PPE) specimens (8.21±0.81MPa). The apical section of Group-1 (2.25% NaOCl+17% EDTA) specimens demonstrated minimum bond strength (2.80±0.18 MPa). The intergroup comparison revealed that Group-3 (2.25% NaOCl +PIPS +17% EDTA) and Group-2 demonstrated comparable outcomes (p>0.05). Group-4 (2.25% NaOCl +6.25% PPE) specimens established significantly lower values than Group-3 and Group-4 (p<0.05). Photon-induced photoacoustic streaming with pineapple peel extract and EDTA demonstrated better bond strength of root canal sealer and have the potential to be used as the final irrigant.

Use of final irrigants MTAD, Salvedora Perscia, Malachite green, and Ti-sapphire laser on push-out bond strength of Zirconia post

AIM: Evaluation of the push-out bond strength (PBS) of zirconia post-bonded to radicular dentin after using different final irrigants (MTAD, Malachite green (MG), Ti-sapphire laser and Salvadora persica (S.persica). MATERIAL AND METHOD: Forty human permanent single-rooted were decoronated above the cement-enamel junction. An experienced endodontist performed all the root canal instrumentation using ProTaper universal rotary files. Canals were irrigated using 5.25% NaOCl solution followed by EDTA as a final sterilant. Obturation with gutta-percha using AH Plus sealer was performed. Post-space preparation was completed using Gates Glidden and specimens were randomly assigned to four groups based on the final disinfectant received (n=10). Group 1: 5.25% NaOCl + MTAD, group 2: 5.25% NaOCl + MG, group 3: 5.25% NaOCl +Ti-sapphire laser, and group 4: 5.25% NaOCl + S. persica. The chemically polymerized resin was used to lute zirconia posts. PBS and failure mode analysis were performed using a universal testing machine and stereomicroscope at 40X magnification. Data were compared between the two groups with 95% CI using one-way analysis of variance (ANOVA) with the Tukey post hoc test. p=0.05. RESULTS: Group4(5.25% NaOCl+ S.persica) specimens demonstrated the maximum (8.94±0.14 MPa) bond strength. Conversely, the apical third of Group 2 (5.25% NaOCl+ MG) (2.87±0.15 MPa) samples revealed the minimum bond strength scores. Intergroup comparison exposed that Group 1 (1.3% NaOCl+ MTAD), Group 3 (5.25% NaOCl+Ti-sapphire laser), and Group 4 (5.25% NaOCl+ S. persica) at all three-thirds unveiled no significant difference in PBS (p<0.05). CONCLUSION: Ti-sapphire laser and Salvedora Persica possess the potential to be used as a final root canal irrigant to improve the push-out bond strength of zirconia post-to-root dentin.

Mechanical behaviour of adsorbent pervious concrete using iron slag and zeolite as coarse aggregates

Using low-cost industry waste and mineral adsorbentsto produce Adsorbent Pervious Concrete (APC) is a sustainable solution with manifold environmental advantages.This study investigates the engineering properties of APC to widen the potential of its further utilization as a post-treatment step in refinery and wastewater treatment plants. For this reason, coarse aggregate in pervious concrete was replaced by coarse iron slag and zeolite in portions of 25%, 50%, 75%, and 100% by volume. The statistical analysis of variance (ANOVA) and visualization of the microstructure of APC using Scanning Electron Microscopy (SEM), and Energy Dispersive X-Ray Spectroscopy (EDS) were also presented. Experimental results showed that replacing coarse aggregate with iron slag increased the APC’s strength, and the maximum value of compressive strength (16.80 MPa) occurred at 75% of replacement. Alternatively, increasing the zeolite proportion caused the strength reduction of APC, and the minimum compressive strength (9.40 MPa) happened in a sample with only coarse zeolite. The effect of cementitious paste thickness (CPT) on the compressive strength indicated that the iron slag did not markedly change the average of CPT, only a minor reduction compared to the control sample (0.30–1.5 mm), while zeolites caused considerable increase of average CPT (0.00–2.1 mm). Hence, increasing the average CPT resulted in reducing the APC compressive strength. Also, the specific gravity, resistance to compression, rectangular shape, and micropores on the surface of adsorbents affected the mechanical properties, porosity, and permeability of APC. All APC samples had a satisfactory porosity (more than 15%) and permeability (more than 1.17 mm/s), and the APC sample containing 75% of iron slag had the highest values. The role of adsorbents shape affects the porosity and permeability of APC, especially in the replacement portion of 50% and less, while for samples with more than 50% of adsorbents due to homogenization of the mix and having the same size as aggregates, the void content and infiltration rate approached the value of the control sample. Eventually, iron slag and zeolite based APC could potentially be used in wastewater treatment plants for post-treatment of wastewater as a new cleaner production.

Mechanical and durability performance of 100% recycled aggregate concrete pavers made by compression casting

Sustainable infrastructure developments require optimal use of natural resources and the recycling of the materials generated at the end of the service life of concrete structures. Construction and Demolition (C&D) waste in the form of Recycled Concrete Aggregates (RCA) has been used to manufacture structural and non-structural concrete which is known as Recycled Aggregate Concrete (RAC). However, not all the C&D waste could be incorporated into the structural concrete and the development of innovative construction products for the efficient and economic utilization of RCA is still under investigation. This study aimed to produce concrete pavers with 100% recycled aggregates and a minimum amount of cement through Compression Casting Technique (CCT). A comprehensive experimental investigation was carried out to find out the optimum values of fine to coarse aggregate ratio, cement contents, and casting pressure for the concrete pavers so that a minimum target compressive strength of 35 MPa at 7-days is achieved. The concrete mixes with fine and coarse aggregate contents of 60% and 40%, respectively, cement contents of 15% and 20%, and casting pressure of 20 MPa were found to be the most economical and feasible to produce concrete pavers exhibiting the target compressive strength. The mechanical (i.e., compressive and flexural strength) as well as durability (i.e., drying shrinkage, water absorption, cyclic ponding in sulfuric acid and sodium chloride salt solution) properties were investigated in detail for the pavers made from the selected optimum concrete mixes. The compressive and flexural strength of RAC pavers satisfied the minimum required strength values specified in international standards [GB – 28 635–2012, IS 15658:2021, A231.2–14, ASTM C936, ASTM C 1272, ASTM C902] and local [NHA & AJK] specification. The durability tests showed that the RAC pavers are resilient against salt and acid attack. The porous nature of RAC positively affected the pavers’ compressive strength, especially under a saline environment. The maximum water absorption of the RAC pavers was 6.34% which was found to be in the acceptable range, however, their drying shrinkage was higher than Natural Aggregate Concrete (NAC) pavers. As for the impact of casting technique, the properties of the RAC pavers were improved by employing CCT. To predict compressive strength based on the parameters of this study, an equation is proposed by regression analysis of the obtained compressive strength results which showed reasonable accuracy in predicting the strength of pavers. Finally, this study concluded that it is feasible and reliable to manufacture concrete pavers of 35 MPa compressive strength at 7-days (or 55 MPa at 28-days) by replacing 100% natural aggregates with recycled aggregates (both fine and coarse), using 20% cement content, and employing compression casting.

Enhanced microwave metrology using an optical grating in Rydberg atoms.

An enhanced measurement of the microwave (MW) electric (E) field is proposed using an optical grating in Rydberg atoms. Electromagnetically induced transparency (EIT) of Rydberg atoms appears driven by a probe field and a control field. The EIT transmission spectrum is modulated by an optical grating. When a MW field drives the Rydberg transition, the central principal maximum of the grating spectrum splits. It is interesting to find that the magnitude of the sharp grating spectrum changes linearly with the MW E-field strength, which can be used to measure the MW E-field. The simulation result shows that the minimum detectable E-field strength is nearly 1/8 of that without gratings, and its measurement accuracy could be enhanced by about 60 times. Other discussion of MW metrology based on a grating spectrum is also presented.

Investigation on Mechanical Strengths and Carbon Foot Print of Modified Foamed Concrete

This paper describes the work of a study carried out to investigate the mechanical strengths and carbon foot print of foamed concrete incorporating with local industrial wastes. Experiments were performed to obtain a minimum 28 days compressive strength of 15 MPa modified foamed concretes by using palm oil fuel ash (POFA) and fly ash (FA) as partial cement replacement and unprocessed rush husk ash (RHA) as partial fine aggregate replacement. Carbon footprint analysis was carried out by determining the CO2emission for each constituent materials in the modified foamed concrete mixes. Although incorporation of POFA in the foamed concrete containingRHA fine aggregate gained lower mechanical strengths compared to the use of FA, the minimum compressive strength is still can be attained. In terms of the sustainability, modified foamed concrete with 30% POFA or 30% FA was found an encouraging reduction of carbon foot print up to about 30% compared to the control foamed concrete. Based on eco-strength indicator, the optimum foamed concrete mix with POFA was found to be at 22.5% cement replacement level. The eco-modified foamed concrete has good potential in civil engineering construction and environmentally friendly.

Mechanical Strength Estimation of Self-Compacting Geopolymer Concrete using ReLU based Deep Neural Network

ABSTRACT A deep learning artificial neural network model developed in Tensorflow using the ReLU function is presented in this paper to determine the effect of nine different input parameters on the mechanical strength of self-compacting geopolymer concrete (SGC). With the application of the above model, it has been observed that the convergence outcome of our model is predicted with minimum error. The novelty of our model is the ReLU function which improves the accuracy of the results. Our study presents a systematic investigation of the compressive strength, flexural strength, and tensile strengths of SGC depending upon nine vital parameters, such as GFS, Fly ash, NaOH, Na2SiO3 content, Age of specimens, Slump Value, T50, L Box and J Ring value as input. A large number of experiments were conducted to prepare a comprehensive database of the mechanical strength of Flyash-GFS-based SGC. The database has a total of 396 samples which were collected from 132 distinct mixtures, where the minimum and maximum compressive strength value is 7.7 Mpa and 66.7 Mpa, respectively. For the prediction based on deep learning, authors have performed an adequate number of iterations for both training and testing using error estimation parameters such as mean absolute error (MAE), mean square error (MSE), and root mean square error (RMSE). The error parameter values for the compressive strength of SGC are 2.42, 2.94 and 1.07, respectively, for MAE, RMSE and MSE. The other mechanical properties and their error parameter have also been thoroughly evaluated in our work.

Mechanical, durability, and microstructural properties of mortars containing spent mushroom substrate as partial fine aggregate replacement.

Replacing conventional fine aggregates with spent mushroom substrate (SMS) is aimed at developing a sustainable lightweight masonry mortar. It is also an alternative solution for the current improper mushroom waste disposals. Density, workability, compressive strength, specific strength, flexural strength, ultrasonic pulse velocity, water absorption, sorptivity, and equivalent CO2 emission in relation to sand reduction in mortars containing 2.5-15.0% (by volume) SMS passing through a 4.75-mm sieve were investigated. As the percentages of replacement increased from 2.5 to 15.0%, the density of the SMS mortar reduced up to 34.8%, with corresponding compressive strengths of 24.96 to 3.37 MPa. Mixes with up to 12.5% SMS met the minimum compressive and flexural strengths as stated in the ASTM C129 standard. In addition, the equivalent CO2 emission of the mixes reduced 15.09% as the SMS content increased while cost-effectiveness increases up to 98.15% until 7.5% SMS replacement. In conclusion, the use of SMS as fine aggregates up to 12.5% is a viable mix design strategy for producing sustainable lightweight mortar with a lower carbon emission.

Fusion splicing of plastic optical fibers using a mid-IR fiber laser

This work demonstrated the fusion splicing of plastic optical fibers (POFs) using a 2.8 μm continuous-wave fiber laser. This mid-IR laser-based fusion splicing technique does not require the use of adhesives or any other treatments. The performance of the proposed method was investigated by assessing the optical transmission, tensile strength and bending strength values of POF specimens after fusion bonding while employing various splicing conditions. An optical transmission of 0.76 was obtained by splicing under appropriate conditions. A minimum bending radius and tensile strength of the POF samples were found to be 1.5 mm and 13.5 N, respectively.

ISO1083/JS/400-15

Abstract ISO1083/JS/400-15 is a ferritic spheroidal graphite cast iron that has a minimum tensile strength of 400 MPa (58 ksi) and a minimum elongation of 15%, when measured on test pieces machined from separately cast samples. It has a tensile strength exceeding that of the highest-tensile-strength grade of gray cast iron, together with much higher elongation and impact resistance. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and shear strength as well as fatigue. It also includes information on casting and heat treating. Filing Code: CI-105. Producer or source: International Organization for Standardization.

Functional outcomes and complications after treatment of distal radius fracture in patients sixty years and over: A systematic review and network meta-analysis

AimThis network meta-analysis aims to compare functional outcomes and complications between conservative treatment and surgery for distal radius fractures in patients aged 60 years and over. MethodsWe searched the PubMed, EMBASE, and Web of Science databases for randomized controlled trials (RCTs) assessing the effect of conservative treatment and surgery for distal radius fractures in patients aged 60 years and over. Primary outcomes included grip strength and overall complications. Secondary outcomes included Disabilities of the Arm, Shoulder, and Hand (DASH) scores, Patient-Rated Wrist Evaluation (PRWE) scores, wrist range of motion and forearm rotation, and radiographic assessment. All continuous outcomes were assessed using standardized mean differences (SMDs) with 95% confidence intervals (CIs), and binary outcomes were assessed using odds ratio (OR) with 95% CIs. The surface under the cumulative ranking curve (SUCRA) was used to determine a hierarchy of treatments. Cluster analysis was performed for grouping treatments based on the SUCRA values of primary outcomes. ResultsFourteen RCTs were included to compare conservative treatment, volar lockedplate (VLP), K-wires fixation, and external-fixation. VLP outperformed conservative treatment for 1-year and minimum 2-year grip strength (SMD; 0.28 [0.07 to 0.48] and 0.27 [0.02 to 0.53], respectively). VLP yielded the optimal grip strength at 1-year and minimum 2-year follow-up (SUCRA; 89.8% and 86.7%, respectively). In a subgroup analysis of patients aged 60 to 80 years old, VLP outperformed conservative treatment in DASH and PRWE scores (SMD, 0.33 [0.10, 0.56] and 0.23 [0.01, 0.45], respectively). In addition, VLP had the fewest complications (SUCRA = 84.3%). Cluster analysis suggested that VLP and K-wire fixation were more effective treatment groups. ConclusionEvidence to date demonstrates that VLP provides measurable benefits in grip strength and fewer complications to those 60 years of age and over, and that benefit is not reflected in current practice guidelines. There is a subgroup of patients where K-wire fixation outcomes are similar to those of VLP; defining this subgroup may yield substantial societal benefits.

Influence of knots on the adhesion of wood from young Eucalyptus grandis plantations

ABSTRACT The structural use of wood from young trees requires gluing smaller timber pieces to form large elements. In young Eucalyptus timber of structural dimensions, knots do not significantly diminish the mechanical properties, yet their influence on wood adhesion has not been widely studied. Therefore, the aim of the study was to assess the influence of knots on the bond quality of face-glued wood from young E. grandis. Wood from seven-year-old E. grandis trees was tested in shear on the bond-line (polyurethane adhesive) using paired samples of knot-containing and clear wood samples. Knot features did not correlate with shear strength or wood failure percentage. Knot-containing samples had a lower percentage of wood failure (5.8%), but the same shear strength as clear wood samples. Below a wood density of 650 kg m−3, clear and knot-containing wood behaved similarly, but above this value, knots influenced wood adhesion negatively. By simulating glulam beams with high-density wood on the outer lamellas, it was possible to show that shear stress on those bond-lines is lower than the minimum shear strength observed on dense knot samples. Hence, lower adhesion caused by knots on denser wood probably does not represent a significant problem for glued laminated products from young Eucalyptus grandis trees.

Effects of un-parallel notches on the granite fracture properties and acoustic emission phenomena under biaxial test: PFC computation and experimental verification

To assess connections between these notches throughout fracture formation under stress, the mechanical performance of granite specimens with two non-parallel notches underwent a biaxial compression test. The first notch had a 45° angle, whereas the second had a variable angle (0°, 45°, 90°, 130°, and 180°). Three ligament angles (0°, 45°, and 90°) were measured between the inner tips of two notches and the horizontal axis. The ligament length, distance between the inner tips of the two notches, and both notch lengths were each 2 cm. These samples were examined at 0, 1, and 3 MPa confining pressures. By using the particle flow code (PFC), simulated results of the evaluations were run after the trials. It was discovered that the specimens’ failure strengths were influenced by the notch’s geometric characteristics, which in turn impacted the failure mechanism as well as fracture geometry. The number of tensile fractures had an impact on the specimens’ failure strengths. Whilst also increasing the ligament angle, more induced tensile cracks were produced. In the early stages of loading, just a few AE events were found, but after that, they multiplied quickly before approaching the peak stress. By raising the confining pressure, the AE hits were increased and delay failure was occured. The failure strength and AE hits are significantly impacted by the second notch’s angle. In constant ligament angel, the compressive strength of models containing overlapped joint were more than that with non-overlapped joints. In models containing non-overlapped notches, the model with ligament angles of 0° and 45° had maximum and minimum compressive strength, respectively. In models containing overlapped notches, the model with ligament angles of 90° and 45° had maximum compressive strength and minimum compressive strength, respectively. In all ligament angles, minimum compressive strength was occurred when the upper joint angle was 45°. Both the computational and experimental methodologies showed that the specimens’ failure pattern and compressive strength were very comparable.

Potential Use of Scoria as a Cementitious Material for Green Concrete Production

The demand for cement, which is one of the key components of concrete, is high in Ethiopia, but it is the most expensive and environmentally unfriendly construction material. Due to the increasing concerns about the environment worldwide, researchers have started looking for other resources that can be used to reduce the pollution caused by the cement industry. One of the most effective ways to reduce the pollution caused by the cement industry is by using volcanic scoria powder as a partial replacement for cement in concrete production. Scoria is a locally available natural volcanic material in Ethiopia, especially around the rift valley regions. This natural resource can also be used to reduce energy consumption and the cost of production of cement. To investigate this study, nonprobability sampling techniques were adopted to collect samples from the study area. A differing proportion of scoria powder was considered as a partial replacement of cement after analyzing its characteristics, and its effect on the fresh and mechanical properties of hardened concrete was examined. The test results on the characteristics of scoria revealed that the material is suitable to be used as a supplementary cementitious material in concrete production; hence, its main constituents SiO2 + Al2O3 + Fe2O3 are higher than 70% as per ASTM C618. As the content of scoria powder replacement in cement is increased, it reduces the slump of freshly mixed concrete properties. The hardened concrete specimens made with 10%, 20%, and 30% partial replacement of cement with scoria achieved the specified minimum strength after 28 days of curing time. But concrete specimens made with 40% scoria content do not satisfy the minimum specified concrete strength even after 90 days. The significant strength achievement in scoria blended concrete specimens occurred when moving from 56 to 90 days of curing with 10% replacements. However, in reference specimens, this was observed during 28 days of curing times. The findings of this investigation revealed that scoria powder could replace cement by 30% for the production of normal concrete and it also has the potential to protect the environment from carbon dioxide emissions. These findings satisfy the basic strategy of green concrete production in worldwide.

Cure cycle optimization of infrared cured composites using Taguchi method

AbstractKnowing that cure cycle has a significant effect on the mechanical properties of the composite materials, determining the effects of cure cycle parameters – such as heating rate, maximum temperature, and dwell time, has gain importance. This study addresses the optimum cure cycle of an infrared cured carbon fiber pre‐preg material. An infrared oven equipped with 1 kW halogen infrared heating unit and vacuum system was used. Different cure cycles determined by means of Taguchi experiment design approach and a cure cycle was found maximizing the tensile strength of the material. Results showed that infrared curing is a strong alternative to the autoclave despite its shortcomings regarding the product geometry. The optimized cure cycle showed 23% increase in the tensile strength comparing the tested cure cycle which is resulted with the minimum tensile strength. Besides, comparing the specimens cured with the optimum cure cycle, the infrared cured specimens showed slightly higher tensile strength than the autoclave cured counterparts. According to Taguchi optimization, optimum values for maximum tensile strength were found as 10°C/min, 130°C for heating rate and 60 min for plateau time. According to the analysis of variance, the most effective parameter affecting the tensile strength was the heating rate.

Density and Strength Performance of Cellular Concrete Blended with Bentonite Clay and Polypropylene Fiber

Cellular concrete (known as foamed concrete) is a lightweight building material with low densities ranging from 900 kg/m3 to 1900 kg/m3, which can have potential applications in civil engineering practices. However, it is very weak in withstanding tensile loads which leads to cracks during shrinkage in the drying stage. Therefore, six different groups of cellular concrete are prepared for a possible application in grouting underneath the foundations to achieve a minimum compressive strength of 2000 psi (13.79 MPa) as per ASTM C476, and for soil nail grout with a minimum compressive strength of 3000 psi (20.86 MPa) as per ASTM C109 at 28 days. Furthermore, these mixtures are undergoing laboratory testing for pushout (using steel cylinders with varied diamters and thickneses) and pullout tests as the subsequent part of this project. All groups contain 0.34 water-to-cement ratio, same size and amounts of sands and superplasticizer (SP). The first group included four control mixes without bentonite and polypropylene fiber (PPF) additives with varied foam content (C1-F1,F2,F3,F4). The remaining groups consist of 17 different mixes blended with either one or both additives. The content effect of foam agent, bentonite clay, and PPF as additives on the density and compressive and flexural strengths of cellular concrete are investigated in this study. The results revealed that the introduction of bentonite and/or PPF in cellular concrete mixtures increased the density and strength. The results revealed that low dry densities (less than 1900 kg/m3) of blended cellular concrete mixtures can reach high compressive strength of 24.37 MPa with 4.74 MPa flexural strength that make them feasible for geotechnical and structural engineering applications.