Experimental Study of a Superabsorbent Polymer Hydrogel in an Alkali Environment and Its Effects on the Mechanical and Shrinkage Properties of Cement Mortars.

As internal curing self-healing agents in concrete repair, the basic properties of superabsorbent polymers (SAPs), such as water absorption and release properties, are generally affected by several factors, including temperature and humidity solution properties and SAP particle size, which regulate the curing effect and the durability of cementitious composites. This study aimed to investigate the water retention capacities of SAPs in an alkaline environment over extended periods by incorporating liquid sodium silicate (SS) into SAP-water mixtures and examining the influence of temperature. The influence of SAP particle size on mortar's water absorption capacity and mechanical behavior was investigated. Two mixing techniques for SAPs (dry and pre-wetting) were employed to assess the influence of SAP on cement mortars' slump, mechanical properties, and cracking resistance. Four types of SAPs (SAP-a, SAP-b, SAP-c, and SAP-d), based on the molecular chains and particle size, were mixed with SS to study their water absorption over 30 days. The results showed that SAPs exhibit rapid water absorption within the first 30 min, exceeding 85% before reaching a saturation point, and the chemical and temperature variations in the water significantly affected water absorption and desorption. The filtration results revealed that SAP-d exhibited the slowest water release rate, retaining water for considerably longer than the other three types of SAPs. The mechanical properties of SAP mortar were reduced due to the addition of an SAP and the improved cracking resistance of the cement mortars.

Reducing non-value added (NVA) activities through lean tools for the precast industry.

Lean management is a strategic approach that is used in construction industry, specifically aims at minimizing and ultimately eliminating non-value-adding activities, commonly referred to as waste, within construction projects. However, an increase in non-value added (NVA) activities within the precast industry has the potential to diminish both productivity and efficiency. The aim of this paper is to investigate the use of lean tools for minimizing NVA activities in the construction industry. A comprehensive literature review, the study identified Unnecessary Inventory (UI), Waiting Time (WT), Overproduction (OP), and Unnecessary Movement (UM) as major NVA activities that affect the precast industry. A structured questionnaire was designed and conducted among precast industry professionals and lean experts to collect data. The data was then analyze using partial least square test-structural equation modelling, including reliability and validity tests, to ensure data quality. Results indicated that the precast industry professionals widely utilized Just-in-time (JIT), Continuous Improvement (CI), and Total Quality Management (TQM) as lean tools to reduce NVA activities. A conceptual path model was developed to assess the impact of Lean tools on NVA activities. The results of the analysis reveal a strong positive relationship between Lean tools and NVA activities, with a ß value of 0.654. The findings of this study can be used for improving the productivity of construction projects by focusing on how to minimize NVA activities using lean tools in precast industry.

Identification and distribution of the "Candidatus Liberibacter asiaticus"-Asian citrus psyllid pathosystem in Saudi Arabia.

Citrus greening disease was first reported in Saudi Arabia during the 1970's when characteristic foliar and fruit symptoms were observed in commercial citrus groves, however, "Candidatus Liberibacter asiaticus" (CLas) was not detected in symptomatic trees until 1981-1984 when CLas-like cells were observed by transmission electron microscopy in leaves collected from symptomatic citrus groves in southwestern Saudi Arabia. Despite the anticipated establishment of the CLas-Asian citrus psyllid (ACP) (Diaphorina citri Kuwayama) pathosystem, CLas presence has not been verified in suspect trees nor have ACP infestations been documented. Given the recent expansion of citrus production in Saudi Arabia, a systematic country-wide survey was carried out to determine the potential CLas distribution in the thirteen citrus-growing regions of the country. Citrus trees were surveyed for presence of CLas-psyllid vector(s) and characteristic disease symptoms in commercial and urban citrus trees. Adult psyllids collected from infested citrus trees were identified as ACP based on morphological characteristics. Real-time, quantitative PCR amplification (qPCR) of the CLas ß-subunit of the ribonucleotide reductase (RNR) gene from citrus leaf and fruit samples and/or ACP adults, revealed trees were positive for CLas detection in ten of the 13 survey regions, however, CLas was undetectable in ACP adults. Phylogenetic and SNPs analyses of a PCR-amplified, cloned fragment of the CLas 16S rRNA gene (~1.1 kbp) indicated Saudi Arabian isolates were most closely related to Florida, USA isolates. Analysis of climate variables indicated that the distribution of the ACP-CLas pathosystem observed in Saudi Arabia was consistent with published predictions of terrains most likely to support establishment.

Predicting the strengths of date fiber reinforced concrete subjected to elevated temperature using artificial neural network, and Weibull distribution.

Date palm fiber (DPF) is normally used as fiber material in concrete. Though its addition to concrete leads to decline in durability and mechanical strengths performance. Additionally, due to its high ligno-cellulose content and organic nature, when used in concrete for high temperature application, the DPF can easily degrade causing reduction in strength and increase in weight loss. To reduce these effects, the DPF is treated using alkaline solutions. Furthermore, pozzolanic materials are normally added to the DPF composites to reduce the effects of the ligno-cellulose content. Therefore, in this study silica fume was used as supplementary cementitious material in DPF reinforced concrete (DPFRC) to reduce the negative effects of elevated temperature. Hence this study aimed at predicting the residual strengths of DPFRC enhanced/improved with silica fume subjected to elevated temperature using different models such as artificial neural network (ANN), multi-variable regression analysis (MRA) and Weibull distribution. The DPFRC is produced by adding DPF in proportions of 0%, 1%, 2% and 3% by mass. Silica fume was used as partial substitute to cement in dosages of 0%, 5%, 10% and 15% by volume. The DPFRC was then subjected to elevated temperatures between 200 and 800 °C. The weight loss, residual compressive strength and relative strengths were measured. The residual compressive strength and relative strength of the DPFRC declined with addition of DPF at any temperature. Silica fume enhanced the residual and relative strengths of the DPFRC when heated to a temperature up to 400 °C. To forecast residual compressive strength (RCS) and relative strength (RS), we provide two distinct ANN models. The first layer's inputs include DPF (%), silica fume (%), temperature (°C), and weight loss (%). The hidden layer is thought to have ten neurons. M-I is the scenario in which we use RCS as an output, whereas M-II is the scenario in which we use RS as an output. The ANN models were trained using the Levenberg-Marquardt backpropagation algorithm (LMBA). Both neural networking models exhibit a significant correlation between the predicted and actual values, as seen by their respective R = 0.99462 and R = 0.98917. The constructed neural models M-I and M-II are highly accurate at predicting RCS and RS values. MRA and Weibull distribution were used for prediction of the strengths of the DPFRC under high temperature. The developed MRA was found to have a good prediction accuracy. The residual compressive strength and relative strength followed the two-parameter Weibull distribution.

Flexural Response of Concrete Specimen Retrofitted with PU Grout Material: Experimental and Numerical Modeling.

Polyurethane (PU) composite is increasingly used as a repair material for civil engineering infrastructure, including runway, road pavement, and buildings. Evaluation of polyurethane grouting (PUG) material is critical to achieve a desirable maintenance effect. This study aims to evaluate the flexural behavior of normal concrete repaired with polyurethane grout (NC-PUG) under a three-point bending test. A finite element (FE) model was developed to simulate the flexural response of the NC-PUG specimens. The equivalent principle response of the NC-PUG was analyzed through a three-dimensional finite element model (3D FEM). The NC and PUG properties were simulated using stress-strain relations acquired from compressive and tensile tests. The overlaid PUG material was prepared by mixing PU and quartz sand and overlayed on the either top or bottom surface of the concrete beam. Two different overlaid thicknesses were adopted, including 5 mm and 10 mm. The composite NC-PUG specimens were formed by casting a PUG material using different overlaid thicknesses and configurations. The reference specimen showed the highest average ultimate flexural stress of 5.56 MPa ± 2.57% at a 95% confidence interval with a corresponding midspan deflection of 0.49 mm ± 13.60%. However, due to the strengthened effect of the PUG layer, the deflection of the composite specimen was significantly improved. The concrete specimens retrofitted at the top surface demonstrated a typical linear pattern from the initial loading stage until the complete failure of the specimen. Moreover, the concrete specimens retrofitted at the bottom surface exhibit two deformation regions before the complete failure. The FE analysis showed good agreement between the numerical model and the experimental test result. The numerical model accurately predicted the flexural strength of the NC-PUG beam, slightly underestimating Ke by 4% and overestimating the ultimate flexural stress by 3%.

Potential of resistance inducers for citrus huanglongbing management via soil application and assessment of induction of pathogenesis-related protein genes.

Huanglongbing (HLB) or citrus greening currently is the most devastating citrus disease worldwide. Unfortunately, no practical cure has been available up to now. This makes the control of HLB as early as possible very important to be conducted. The objective of this study was to investigate the efficacy of the application of salicylic acid (SA) and Phenylacetic acid (PAA) on one-year-old seedlings of different citrus species (Citrus reticulata, C. sinensis, C. aurantifolii) growing on C. volkameriana and C. aurantium by soil drench methods. Factorial analysis of variance showed the percent change in "Candidatus Liberibacter asiaticus" titer and disease severity on a different combination of citrus species growing on the two rootstocks treated with inducers and Oxytetracycline (OTC) were significantly different compared to the untreated plants. SA alone or in combination with OTC provided excellent (P-value < 0.05) control of HLB based on all parameters. The interaction between both factors (Rootstocks x Citrus species) significantly influenced the Ct value (P-value = 0.0001). "Candidatus Liberibacter asiaticus" titer in plants treated with OTC was reduced significantly with a range of -18.75 up to -78.42. Overall, the highest reduction was observed in the application of OTC on sweet orange growing on C. volkameriana (-78.42), while the lowest reduction was observed in the same cultivar which was treated with a combination of SA and OTC (-3.36). Induction of pathogenesis-related (PR) genes, i.e., PR1, PR2, and PR15, biosynthesis of Jasmonic acid and ethylene which are also important pathways to defense activity were also significantly increased in treated plants compared to untreated plants. This study suggests that the application of inducer alone is acceptable for HLB management. We proposed the application of SA and PAA as a soil drench on the citrus seedlings as promising, easy, and environmentally safe for HLB disease control on citrus seedlings.

Optimization and Modelling the Mechanical Performance of Date Palm Fiber-Reinforced Concrete Incorporating Powdered Activation Carbon Using Response Surface Methodology.

Date palm fiber (DPF) has been reported to have many advantages when used in concrete, however, its major disadvantage is that it causes a reduction in compressive strength. In this research, powdered activated carbon (PAC) was added to cement in the DPF-reinforced concrete (DPFRC) to lessen the loss in strength. PAC has not been properly utilized as an additive in fiber reinforced concrete even though it has been reported to enhance the properties of cementitious composites. Response surface methodology (RSM) has also been utilized for experimental design, model development, results analysis, and optimization. The variables were DPF and PAC as additions each at proportions of 0%, 1%, 2%, and 3% by weight of cement. Slump, fresh density, mechanical strengths, and water absorption were the responses that were considered. From the results, both DPF and PAC decreased the workability of the concrete. DPF addition improved the splitting tensile and flexural strengths and reduced the compressive strength, and up to 2 wt% PAC addition enhanced the concrete's strength and lowered the water absorption. The proposed models using RSM were extremely significant and have excellent predictive power for the concrete's aforementioned properties. Each of the models was further validated experimentally and was found to have an average error of less than 5.5%. According to the results of the optimization, the optimal mix of 0.93 wt% DPF and 0.37 wt% PAC as cement additives resulted in the best properties of the DPFRC in terms of workability, strength, and water absorption. The optimization's outcome received a 91% desirability rating. The addition of 1% PAC increased the 28-day compressive strength of the DPFRC containing 0%, 1% and 2% DPF by 9.67%, 11.13% and 5.5% respectively. Similarly, 1% PAC addition enhanced the 28-day split tensile strength of the DPFRC containing 0%, 1% and 2% by 8.54%, 11.08% and 19.3% respectively. Likewise, the 28-day flexural strength of DPFRC containing 0%, 1%, 2% and 3% improved by 8.3%, 11.15%, 18.7% and 6.73% respectively with the addition of 1% PAC. Lastly, 1% PAC addition led to a reduction in the water absorption of DPFRC containing 0% and 1% DPF by 17.93% and 12.2% respectively.

First Report of Basal Rot of Onion Caused by Fusarium oxysporum f. sp. cepae in Saudi Arabia.

Onion (Allium cepa L.) is a globally important crop worldwide including Saudi Arabia. In November 2020, 2-month-old onion plants (cv. Redwing) in commercial fields within the Sajir area of Riyadh region (∼ 1.4 ha), showed symptoms of yellowing, wilting, stunting, bulb discoloration, rot in the basal parts of bulb and decrease in roots. In the advanced stages, the affected plants collapsed and died. The incidence of symptomatic plants ranged from 30 to 65% in the surveyed fields. To isolate the pathogen, symptomatic onion plants (n =20) were sampled. Diseased tissues from roots and bulbs were cut into small pieces (4 × 4 mm), sanitized with 1% sodium hypochlorite solution for 2 min, submerged in 70% alcohol for 20 s, then rinsed with sterile water, before plating on potato dextrose agar (PDA) medium. The plates were incubated at 25°C for 6 days. Subcultures of the mycelia grown out of the diseased tissues produced purplish pink fungal colonies on PDA. On carnation leaf agar, cultures were characteristic of Fusarium oxysporum as described by Leslie and Summerell (2006), with the presence of unicellular microconidia (3.8 to 7.8 × 1.7 to 2.5 µm, n= 50) without septa in false heads or short monophialides and slightly curved macroconidia (16.3 to 28 × 4.2 to 6.1 µm, n= 50) with two to four septa. Older mycelia developed many chlamydospores that were single or in short chains. To further confirm the pathogen identification, DNA was extracted from single-spore cultures of three representative isolates using the DNeasy Plant Mini kit (QIAGEN, Hilden, Germany). Three different fungal nuclear regions of internal transcribed spacer (ITS), elongation factor 1-α, (TEF1-α) and the second largest subunit of DNA-directed RNA polymerase II (RPB2) DNA were amplified by PCR and sequenced with the following primers: ITS4 and ITS5 (White et al. 1990); EF-1 and EF-2 (O'Donnell et al. 2008); and fRPB2-5F and fRPB2-7cR (Liu et al. 1999), respectively. Phylogenetic analysis based on the alignment of the ITS, TEF1-α, and RPB2 sequences using MEGA7 placed these isolates in the F. oxysporum clade. The ITS, TEF1-α, and RPB2 sequences of an isolate FOC-OR9 were submitted to GenBank (OL721757, OL764494, and OL764495 respectively). To confirm the forma specialis cepae, a fragment of the F. oxysporum f. sp. cepae gene Secreted In Xylem 3 (SIX3) was amplified by PCR (Kalman et al. 2020). The SIX3 amplicon (∼ 277-bp) was sent for sequencing, and the sequence was submitted to GenBank (OL828265). BLASTn analysis of the sequences showed 100% identity with F. oxysporum f. sp. cepae (KP746408). To fulfill Koch's postulates, pathogenicity tests were performed with healthy onion bulbs cv. "Redwing" of 100-150 g each. Prior to inoculation of onion bulbs, the dry bulb scales, one of the fleshy inner scales, as well as the roots were removed. Bulbs were then surface sterilized (as described above) and injected with 20 µl of a conidial suspension (106 spores/ ml) into the basal plate of each bulb and approximately 1 cm deep into the tissue. Six bulbs were inoculated for each isolate, placed in a mesh bag, and incubated at 28 °C in the dark. Six bulbs injected with sterile water and six non-inoculated bulbs served as controls. At the 4th week post inoculation, necrotic rot symptoms and brown discoloration were observed on the basal plates of these inoculated bulbs (similar symptoms to those observed in the field), while control treatments showed no symptoms. The pathogen was re-isolated from the basal plates onto PDA and identified morphologically and molecularly as F. oxysporum f. sp. cepae, thus fulfilling Koch's postulates. The test was repeated twice. This pathogen was previously reported causing onion basal rot in United Kingdom (Taylor, et al., 2013). To our knowledge, this is the first report of basal rot in onion caused by F. oxysporum f. sp. cepae in Saudi Arabia. It is recommended that preventive management should be considered as this disease may cause significant economic losses for onion growers in Saudi Arabia. Also, Fusarium mycotoxin contamination of onion bulb could pose a public health risk.

Optimization of Structural Damage Repair with Single and Double-Sided Composite Patches through the Finite Element Analysis and Taguchi Method.

Over the last four decades, numerous studies have been conducted on the use of bonded composite repairs for aircraft structures. These studies have explored the repair of damaged plates through experimental, numerical, and analytical methods and have found that bonded composite repairs are effective in controlling crack damage propagation in thin plates. The use of double-sided composite repairs has been found to improve repair performance within certain limits. This study focuses on these limits and optimizes double-sided composite repairs by varying adhesive bond and composite patch parameters. The optimization process begins with a finite element analysis to determine the stress intensity factor (SIF) for various variables and levels, followed by the application of the Taguchi method to find the optimal combination of parameters for maximizing the normalized SIF. In conclusion, we successfully determined the stress intensity factor (SIF) for various variations and normalized it for optimization. An optimization study was then performed using the Taguchi design and the results were analyzed. Our findings demonstrate the repair performance of bonded composite patches using a cost-effective and energy-efficient approach.

Review of Piezoelectric Actuator Applications in Damaged Structures: Challenges and Opportunities.

Piezoelectric material transducers can work as an actuator or sensor. Generally, the actuator will be used to repair the structure, and the sensor will be used to find the health condition. In the last two decades, piezoelectric actuators have shown the capacity to lower and control the shear stress concentration and joint edge peel in adhesively bonded joint systems. Hence, this paper aims at reviewing the application of piezoelectric actuators in damaged structures and adhesively bonded combined systems based on three different repair investigation methods: analytical, numerical, and experimental. Moreover, the study also explores the delamination control of composite material beams and some other studies using a piezoelectric actuator. The specific aim of this work is to determine scientific challenges and future opportunities for considering piezoelectric materials in damaged structure investigations for novice researchers.

Evaluating the Influence of Elevated Temperature on Compressive Strength of Date-Palm-Fiber-Reinforced Concrete Using Response Surface Methodology.

Due to its availability and affordable processing, date palm fiber (DPF) is among the natural and sustainable fibers used in cementitious composites. Furthermore, DPF is an agricultural, organic, and fibrous material that when subjected to higher temperature can easily degrade and cause reduction in strength. Therefore, the influence of elevated temperatures on the unit weight and strengths of DPF-reinforced concrete needs to be examined. Under this investigation, DPF is used in proportions of 0-3% weight of binder to produce a DPF-reinforced concrete. Silica fume was utilized as a supplemental cementitious material (SCM) in various amounts of 0%, 5%, 10%, and 15% by weight to enhance the heat resistance of the DPF-reinforced concrete. The concrete was then heated to various elevated temperatures for an hour at 200 °C, 400 °C, 600 °C, and 800 °C. After being exposed to high temperatures, the weight loss and the compressive and relative strengths were examined. The weight loss of DPF-reinforced concrete escalated with increments in temperature and DPF content. The compressive and relative strengths of the concrete improved when heated up to 400 °C, irrespective of the DPF and silica fume contents. The heat resistance of the concrete was enhanced with the replacement of up to 10% cement with silica fume when heated to a temperature up to 400 °C, where there were enhancements in compressive and relative strengths. However, at 800 °C, silica fume caused a significant decline in strength. The developed models for predicting the weight loss and the compressive and relative strengths of the DPF-reinforced concrete under high temperature using RSM have a very high degree of correlation and predictability. The models were said to have an average error of less than 6% when validated experimentally. The optimum DPF-reinforced concrete mix under high temperature was achieved by adding 1% DPF by weight of binder materials, replacing 12.14% of the cement using silica fume, and subjecting the concrete to a temperature of 317 °C. The optimization result has a very high desirability of 91.3%.

Characterization of the Asian Citrus Psyllid-'Candidatus Liberibacter Asiaticus' Pathosystem in Saudi Arabia Reveals Two Predominant CLas Lineages and One Asian Citrus Psyllid Vector Haplotype.

In Saudi Arabia (SA), the citrus greening disease is caused by 'Candidatus Liberibacter asiaticus' (CLas) transmitted by the Asian citrus psyllid (ACP) Diaphorina citri. The origin and route(s) of the ACP-CLas pathosystem invasion in SA have not been studied. Adult ACP were collected from citrus trees in SA and differentiated by analysis of the mitochondrial cytochrome oxidase I (mtCOI) and nuclear copper transporting protein (atox1) genes. A phylogenetic analysis of the Wolbachia spp. surface protein (wsp) gene was used to identify the ACP-associated Wolbachia spp. A phylogenetic analysis of the atox1 and mtCOI gene sequences revealed one predominant ACP haplotype most closely related to the Indian subcontinent founder populations. The detection and identification of CLas in citrus trees were carried out by polymerase chain reaction (PCR) amplification and sequencing of the 16S rDNA gene. The CLas-integrated prophage genomes were sequenced, annotated, and used to differentiate CLas populations. The ML and ASTRAL trees reconstructed with prophages type 1 and 2 genome sequences, separately and concatenated, resolved two major lineages, CLas-1 and -2. The CLas-1 clade, reported here for the first time, consisted of isolates from SA isolates and Pakistan. The CLas-2 sequences formed two groups, CLas-2-1 and -2-2, previously the 'Asiatic' and 'Floridian' strains, respectively. Members of CLas-2-1 originated from Southeast Asia, the USA, and other worldwide locations, while CLas-2-2 was identified only in Florida. This study provides the first snapshot into the status of the ACP-CLas pathosystem in SA. In addition, the results provide new insights into the pathosystem coevolution and global invasion histories of two ACP-CLas lineages with a predicted center of origin in South and Southeast Asia, respectively.

Durability and Property Study of Decade Old Crumb Rubber Concrete Cored Specimens.

Crumb rubber concrete (CRC) is a concrete that contains rubber crumbs. This article presents a study of three experiments on long aged CRC specimens that were cored from a decade old CRC bridge deck in Tianjin, China. The three experimental tests conducted were: (1) the flexural stress-strain test on semi-circular disk specimens; (2) the accelerated steel-rebar corrosion test and (3) the carbonation test. In addition, the in situ carbonation test was also carried out on the CRC bridge deck. The flexural stress-strain test results showed that the CRC semi-circular disk specimens exhibited a ductile pattern and high-energy absorbing capacity with its flexural tensile strength being at 5 MPa and the flexural modulus of 10 GPa. The steel corrosion rust rate via the calculation of steel mass loss before and after the test in the accelerated steel-rebar corrosion test remained extremely low. The carbonation test results showed that in comparison with the prediction of two popular carbonation models, the carbonation in the CRC bridge deck took place at a much slower rate during the last 13 years. All of the results obtained in this study are reported for the first-time and indicate that these CRC cored specimens exhibit good mechanical properties and excellent durability characteristics after a decade in service, which may provide the technical knowledge for the possible future application of CRC in concrete constructions.

Evaluation of the mechanical performance of concrete containing calcium carbide residue and nano silica using response surface methodology.

Calcium carbide residue (CCR) is generated from acetylene gas production, and it is highly alkaline and contains a very high amount of calcium. Nano silica (NS), on the other hand, is mostly used in combination with other pozzolanic materials in concrete to ignite the reactivity of the material and to improve the properties of the concrete. This study investigated the effect of CCR incorporated in concrete mixtures to partially replace cement content at 0 to 30% (interval of 7.5%). NS was used as an additive by weight of binder at levels 0 to 4% in increment of 1%. Thus, response surface methodology (RSM) was employed to investigate the effects of CCR and NS on the properties of the concrete, including compressive strength, flexural strength, splitting tensile strength, modulus of elasticity (MoE), and water absorption. The RSM was used for model development predicted concrete's properties and carried out mixture multi-objective optimization by maximizing strengths, MoE, and minimizing water absorption. The results showed that using up to 15% CCR improved the strengths, MoE, and water absorption of the concrete. Adding up to 3% NS further enhanced the strengths, MoE, and water absorption significantly. The developed models for predicting the properties of the concrete using RSM were highly efficient with high degree of correlation. The optimization solutions indicated that the best optimum or best mix combination based on maximum strengths and MoE with minimum water absorption was achieved by replacing 10.6% cement with CCR and adding 1.95% NS by the weight of cementitious materials.

Durability Performance of Self-Compacting Concrete Containing Crumb Rubber, Fly Ash and Calcium Carbide Waste.

Waste tire disposal continues to pose a threat to the environment due to its non-biodegradable nature. Therefore, some means of managing waste tires include grinding them to crumb rubber (CR) sizes and using them as a partial replacement to fine aggregate in concrete. However, the use of CR has a series of advantages, but its major disadvantage is strength reduction. This leads to the utilization of calcium carbide waste (CCW) to mitigate the negative effect of CR in self-compacting concrete (SCC). This study investigates the durability properties of SCC containing CR modified using fly ash and CCW. The durability properties considered are water absorption, acid attack, salt resistance, and elevated temperature of the mixes. The experiment was conducted for mixes with no-fly ash content and their replica mixes containing fly ash to replace 40% of the cement. In the mixes, CR was used to partially replace fine aggregate in proportions of 0%, 10%, and 20% by volume, and CCW was used as a partial replacement to cement at 0%, 5%, and 10% by volume. The results indicate that the mixes containing fly ash had higher resistance to acid (H2SO4) and salt (MgSO4), with up to 23% resistance observed when compared to the mix containing no fly ash. In addition, resistance to acid attack decreased with the increase in the replacement of fine aggregate with CR. The same principle applied to the salt attack scenario, although the rate was more rapid with the acid than the salt. The results obtained from heating indicate that the weight loss was reduced slightly with the increase in CCW, and was increased with the increase in CR and temperature. Similarly, the compressive strength was observed to slightly increase at room temperature (27 °C) and the greatest loss in compressive strength was observed between the temperature of 300 and 400 °C. However, highest water absorption, of 2.83%, was observed in the mix containing 20% CR, and 0% CCW, while the lowest water absorption, of 1.68%, was found in the mix with 0% CR, 40% fly ash, and 10% CCW. In conclusion, fly ash is recommended for concrete structures immersed in water, acid, or salt in sulphate- and magnesium-prone areas; conversely, fly ash and CR reduce the resistance of SCC to heat beyond 200 °C.

Mechanical Properties and Durability Performance of Concrete Containing Calcium Carbide Residue and Nano Silica.

Calcium carbide residue (CCR) is the end-product of production of acetylene gas for the applications such as welding, lighting, ripening of fruits, and cutting of metals. Due to its high pH value, disposing of CCR as a landfill increases the alkalinity of the environment. Therefore, due to its high calcium content, CCR is mostly blended with other pozzolanic materials, together with activators as binders in the cement matrix. In this study, cement was partially substituted using CCR at 0%, 7.5%, 15%, 22.5% and 30% by weight replacement, and nano silica (NS) was utilized as an additive by weight of binder materials at 0%, 1%, 2%, 3% and 4%. The properties considered were the slump, the compressive strength, the flexural strength, the splitting tensile strength, the modulus of elasticity, and the water absorption capacity. The microstructural properties of the concrete were also examined through FESEM and XRD analysis. The results showed that both CCR and NS increase the concrete's water demand, hence reducing its workability. Mixes containing up to 15% CCR only showed improved mechanical properties. The combination of CCR and NS significantly improved the mechanical properties and decreased the concrete's water absorption through improved pozzolanic reactivity as verified by the FESEM and XRD results. Furthermore, the microstructure of the concrete was explored, and the pores were refined by the pozzolanic reaction products. The optimum mix combination was obtained by replacing 15% cement using CCR and the addition of 2% NS by weight of cementitious materials. Therefore, using a hybrid of CCR and NS in concrete will result in reduction of cement utilization in concrete, leading to improved environmental sustainability and economy.

A Systematic Review of Piezoelectric Materials and Energy Harvesters for Industrial Applications.

In the last three decades, smart materials have become popular. The piezoelectric materials have shown key characteristics for engineering applications, such as in sensors and actuators for industrial use. Because of their excellent mechanical-to-electrical and vice versa energy conversion properties, piezoelectric materials with high piezoelectric charge and voltage coefficient have been tested in renewable energy applications. The fundamental component of the energy harvester is the piezoelectric material, which, when subjected to mechanical vibrations or applied stress, induces the displaced ions in the material and results in a net electric charge due to the dipole moment of the unit cell. This phenomenon builds an electric potential across the material. In this review article, a detailed study focused on the piezoelectric energy harvesters (PEH's) is reported. In addition, the fundamental idea about piezoelectric materials, along with their modeling for various applications, are detailed systematically. Then a summary of previous studies based on PEH's other applications is listed, considering the technical aspects and methodologies. A discussion has been provided as a critical review of current challenges in this field. As a result, this review can provide a guideline for the scholars who want to use PEH's for their research.

Molecular and physiological characterization of Fusarium strains associated with different diseases in date palm.

Several species of Fusarium cause serious diseases in date palm worldwide. In the present work, 14 SSR markers were used to assess the genetic variation of Fusarium strains isolated from diseased trees in Saudi Arabia. We also studied the effect of different temperatures on mycelial growth of these strains. The pathogenicity of four strains of F. proliferatum was also evaluated on local date palm cultivars. Eleven SSR markers amplified a total of 57 scorable alleles from Fusarium strains. Phylogenetic analysis showed that F. proliferatum strains grouped in one clade with 95% bootstrap value. Within F. proliferatum clade, 14 SSR genotypes were identified, 9 of them were singleton. Four out of the five multi-individual SSR genotypes contained strains isolated from more than one location. Most F. solani strains grouped in one clade with 95% bootstrap value. Overall, the SSR markers previously developed for F. verticillioides and F. oxysporum were very useful in assessing the genetic diversity and confirming the identity of Saudi Fusarium strains. The results from the temperature study showed significant differences in mycelial growth of Fusarium strains at different temperatures tested. The highest average radial growth for Fusarium strains was observed at 25°C, irrespective of species. The four F. proliferatum strains showed significant differences in their pathogenicity on date palm cultivars. It is anticipated that the assessment of genetic diversity, effect of temperature on hyphal growth and pathogenicity of potent pathogenic Fusarium strains recovered from date palm-growing locations in Saudi Arabia can help in effectively controlling these pathogens.

Mitochondrial Molecular Markers for Resistance to Bayoud Disease in Date Palm.

Bayoud disease, caused by Fusarium oxysporum f. sp. albedinis, is a very serious and destructive disease to date palm. Screening of date palm germplasm for resistance to bayoud disease is a crucial step to avoid or alleviate the disease consequences. Fortunately, it was discovered that there are two mitochondrial plasmid-like DNA molecules associated with susceptibility or resistance to bayoud disease. In this chapter, we present a fast, simple, and reliable technique to screen date palm germplasm for the presence of these mitochondrial molecular markers associated with susceptibility or resistance to bayoud.

Management of Asiatic Citrus Canker Under Field Conditions in Saudi Arabia Using Bacteriophages and Acibenzolar-S-Methyl.

Applications of formulated bacteriophages with skim milk and sucrose or nonformulated bacteriophages combined with acibenzolar-S-methyl (ASM) were compared with copper bactericides applications for suppressing Asiatic citrus canker (ACC) caused by Xanthomonas citri subsp. citri (Xcc) on leaves under greenhouse and field conditions in Saudi Arabia. Bacteriophages were applied one day prior to inoculation of Mexican lime (Citrus aurantifolia) plants with Xcc, then twice a week until the end of the trials. Copper hydroxide was applied once prior to inoculation and then every seven days afterward, whereas ASM was applied one week prior to inoculation and then every 21 days afterward. Under greenhouse conditions, the incidence of ACC on leaves was reduced significantly from 75.2 to 12.8% or 18.3% for plants treated with copper hydroxide or bacteriophages in combination with ASM, respectively. Applications of formulated phages in combination with ASM as soil drench under field conditions significantly decreased disease incidence by 14.8% (Trial 1) and 16.8% (Trial 2) compared with untreated control plants. Overall, the Xcc-inoculated plants treated with bacteriophages + ASM combination showed significant ACC reduction under greenhouse and field conditions. The bacteriophages + ASM combination tested in these trials can be an effective tool in the integrated management programs of Asiatic citrus canker disease.