Wet Screening Research Articles

Recovery of K2SO4 and Separation of SiO2/Al2O3 from Brown Corundum Fly Ash

Brown corundum fly ash (BCFA), which is the collected ash in brown corundum production, has received lots of environmental concerns due to its ultra-fine particle size and complex composition. Aiming to recycle the major elements including K, Al and Si from BCFA environmentally, this work proposed a simple and non-pollution process to utilize BCFA by water leaching, size screening and solution evaporation. The influences of water leaching conditions including leaching temperature, time and liquid-to-solid ratio was considered to optimize the K2SO4 recovery efficiency. Results show that the potassium sulfate content of the product is 75.7% after water leaching at 60 °C for 15 min with the liquid–solid ratio of 20:1. The wet screening and size separation with a 1 μm sieve can separate and enrich aluminum and silicon significantly. The aluminum-rich product is composed of 54.65% of alumina and 11.04% silica, with the alumina and silica ratio (A/S) of 4.95. The silicon-rich product with a particle size of less than 1 μm has a silica content of 57.57% can be used as high-value micro-sphere silica. The research results revealed in this work offers a potential and environmentally industrial treatment technique for the BCFA.

Flat foot at 5 to 6-year-old and history of delayed walking


 Background Flat foot, also known as pes planus, is a common problem in daily pediatric practice. For most children, this physiologic condition gradually disappears with age. However, flat foot that persists after the age of four might have developmental coordination disorder in the future and it may relate to the history of delayed walking .
 Objective To determine the prevalence of delayed walking in children with pes planus compared to children with normal foot curvature and to assess for a possible association between flat foot and history of delayed walking.
 Methods This cross-sectional study was done in 120 children aged 5-6 years. Foot curvature was evaluated by wet footprint test. Inclusion criteria include children in 3 playgroups in Tangerang from January to August 2018, in children aged 5-6 years. Children with history of neurologic diseases, genetic disorders, chronic diseases, disorders of the lower extremities except pes planus, and obesity were excluded. Grading of pes planus refers to Olivier et al. criteria and evaluation of delayed walking at 18-month-old was done through history taking from their parents.
 Results Of 120 children, 41 (34.2%) had pes planus while 11 (9.2%) had a history of delayed walking. Of those 11 children, 9 had pes planus. Most children with pes planus had grade I (78%). There was a significant association between pes planus and delayed walking (OR=10.8; 95%CI 2.2 to 52,9; P=0.001;).
 Conclusion In 5-6-year-old children, there is a significant association between pes planus grade 2 & 3 and history of delayed walking early in life. Wet footprint test screening for children with a history or signs of delayed walking may be used to identify pes planus in order to implement treatment in a timely manner.

Reprocessing feasibility of polymetallic waste rock for cleaner and sustainable mining

Mining operation produces significant volumes of waste rocks (WR) characterised by high heterogeneity in their physical, mineralogical and hydrogeological properties. The purposes of this study were to assess the acid-generating potential, evaluate reprocessing feasibility of polymetallic WR using desulphurisation process (i.e., gravity separation and flotation) and study the geochemical behaviour of desulphurised materials. The fresh WR was collected in the waste dump from Langlois mine at Lebel-sur-Quévillon (Quebec, Canada). The WR sample was divided into six fractions using wet screening: D < 0.053 mm, 0.053 < D < 0.3 mm, 0.3 < D < 0.85 mm, 0.85 < D < 2.4 mm and 2.4 < D < 5 mm. Chemical and mineralogical characterisations showed that fine fractions (D < 2.4 mm) were enriched in sulphide minerals (i.e., 4.6 wt% pyrite, 3.5 wt% sphalerite, etc.) and carbonates (i.e., 3.7 wt% calcite and 5.1 wt% ankerite) compared to coarse fractions (1.2 wt% pyrite, 1.1 wt% sphalerite, 3.2 wt% calcite, 5.2 wt% ankerite). The acid-generating potentials of different fractions were evaluated using acid-base accounting (ABA) and net acid generation (NAG) tests. Only one size fraction (F2) was acid generating and others were classified as uncertain. The degree of liberation of sulphides in the size fractions greater than 2.4 mm was negligible (<16%). Consequently, for this WR sample, 2.4 mm was defined as the diameter of physical locking of sulphide (DPLS). Based on DPLS, the WR were separated into two fractions; reactive (<2.4 mm), non-reactive (<2.4 mm) and then submitted to kinetic tests. Geochemical analyses of leachates of the coarse fraction (2.4 < D < 10 mm), the total sample (D < 5 mm) and –DPLS fractions (D < 2.4 mm) and the benign desulphurised materials (D < 2.4 mm) showed that pH values remained between 6.62 and 8.11 and the instantaneous concentrations of metals such as iron (Fe), copper (Cu) and lead (Pb) were below environmental limits (D019, Quebec, Canada), except for zinc (Zn) leached from the total sample which indicates a risk of contaminated neutral drainage. The pyrite oxidation rate within the coarse fraction was low (16.6 μmol/kg/day) compared to fine fraction (35.8 μmol/kg/day). A combined gravity–flotation process gave better results to decontaminate the waste rock (D < 2.4 mm), with a benign desulphurised material reaching a low sulphur content (0.23 wt%) and high sulphur recovery (89 wt%). The final concentrates from the combined gravity–flotation process showed high base metals (Zn, Cu and Pb) recovery (more than 87 wt%).

Bioprospecting Microbial Diversity for Lignin Valorization: Dry and Wet Screening Methods.

Lignin is an abundant cell wall component, and it has been used mainly for generating steam and electricity. Nevertheless, lignin valorization, i.e. the conversion of lignin into high value-added fuels, chemicals, or materials, is crucial for the full implementation of cost-effective lignocellulosic biorefineries. From this perspective, rapid screening methods are crucial for time- and resource-efficient development of novel microbial strains and enzymes with applications in the lignin biorefinery. The present review gives an overview of recent developments and applications of a vast arsenal of activity and sequence-based methodologies for uncovering novel microbial strains with ligninolytic potential, novel enzymes for lignin depolymerization and for unraveling the main metabolic routes during growth on lignin. Finally, perspectives on the use of each of the presented methods and their respective advantages and disadvantages are discussed.

Enrichment of residual carbon in entrained-flow gasification coal fine slag by ultrasonic flotation

Entrained-flow gasification coal fine slag is a low value and difficult-to-separate solid waste. In this work, ultrasonic flotation experiments are adopted to enrich the residual carbon and are compared to conventional flotation. The concentrate yield and concentrate ash content decrease by 9.94% and 16.54%, respectively, with the flotation perfect index 12.60% higher. Scanning electron microscopy/energy-dispersive X-ray spectroscopy and thermogravimetric analysis show that the ultrasonic flotation has a positive effect on the residual carbon enrichment. Furthermore, the wet screening results prove that the ultrasonic flotation has a more significant crushing effect on the entrained-flow gasification coal fine slag particles than conventional flotation, mainly benefitting the flotation of small particles (i.e. 0.15–0 mm size fractions). Moreover, after ultrasonic emulsification, the collector can be dispersed more evenly and the surface tension of the collector-deionized water system is decreased, which is beneficial to improving the selectivity of the collector. In addition, with ultrasonic pretreatment at 180 W for 4 min in pulp and emulsification at 180 W for 20 s in the collector-deionized water system, the bubbles in the froth layer are the smallest and most stable, and the merging of the bubbles becomes less obvious.

PROPERTIES AND LIQUEFACTION RISK ON BULK CARGO CARRYING BUKIT GOH, KUANTAN BAUXITE; IN ACCORDANCE WITH IMSBC CODE

Bauxite is a raw material used in the production of alumina and, subsequently, aluminium. Like many metals, world demand for aluminium, and therefore bauxite, has grown substantially over the past 10 years in response to economic growth in emerging Asian economies. Bauxite is a relatively soft ore with a distinctive reddish brown colour. Bauxite ore from Malaysia exported to manufacturing country such as China to be processed into aluminium. Basic properties of bauxite are determined for exporting purpose in which several international specifications need to be followed while handling bauxite in order to ensure those raw materials are passing the standard to be imported. Laboratory test had been done to bauxite samples from Bukit Goh in Kuantan to determine its basic and morphological properties. It is found out that moisture content of raw Bukit Goh bauxite is higher compared to processed bauxite where it has the average of 24.33% over 7.16% only on the processed bauxite sample. For particle distribution, it shows that the processed bauxite has less fine particle compared to raw samples with the average of 16.60% compared to raw with 38.50%. Result from FESEM test proves that the lesser fine particle attached to the processed bauxite ore. Referring to the IMSBC Code, it can be stated that raw bauxite samples from Bukit Goh does not pass the standard. This is due to the presence of bulky fine particles which tend to absorb water more than granular particles that may lead to liquefaction to occur. Liquefaction during cargo transportation is high risk especially when there are strong current at the sea. In order to ensure the bauxite is passing the standard, beneficiation process must take place where it include washing, wet screening and mechanical or manual sorting.

Beneficiation of White Kaolinitic Sandstone to Produce Kaolin Concentrate from Wadi Siq-Rakyia Area in Wadi Araba, Jordan

Kaolinitic sandstone samples of Lower Cretaceous from Wadi Siq-Rakyia area in Wadi Araba/south of Jordan were studied and assessed as a source of Kaolin. Three channel samples and a composite bulk sample were studied for their mineralogical, geochemical, and grain size distribution analysis. The aim of this research work was to achieve kaolin concentration by examining the best-suited and cost-effective processing method(s) with appropriate product recovery. Following the initial sample characterisation at “bench scale”, a pilot study was performed on the bulk sandstone sample. Kaolin was accumulated in the fine size fraction (−125 μm) after agitating and wet screening of the sample. The −125 μm size fraction sample was used to produce kaolin concentrate. Hydrocyclone classification was applied in the pilot study for this purpose. The mass flowrate of the feeds and the products in the hydrocyclones was calculated for the bulk sample as well as the amount of water required operating the process. A kaolin-enriched product was produced following the use of hydrocyclones. A kaolin concentrate at a grade of 71% and a recovery of 78% was produced which could be used in the ceramic industry for tableware and sanitaryware.

Influence of Grinding and Classification Circuit on the Performance of Iron Ore Beneficiation – A Plant Scale Study

ABSTRACT Process flowsheet has a greater effect on equipment performance and operating conditions. For this purpose, performance of two iron ore beneficiation plants with the same equipment and feed characteristics but different arrangements in the grinding and classification circuit has been investigated. The first difference between the two plants was the screening type of HPGR product. Wet screening in the second plant caused higher classification efficiency, decreasing the circulating load, removing the dust production during operation. Wet screening caused to increased the moisture of HPGR feed which helped in improving the lifetime of HPGR rolls by a protective layer on the surfaces of HPGR rolls and between studs. Furthermore, it led to a reduction of HPGR feed rate, roll speed, and operating pressure. The feed rate of Ball mill in the second plant is lower and it has a finer product. As a result, ball consumption and rejected materials from trommel screen was decreased and pulp lifters lifetime was increased. In the second plant as well as the first plant,, the same hydrocyclone overflow d80 was achieved under lower operating pressure and the larger vortex finder diameter but the wear rate of hydrocyclone’s internal parts has been approximately double. The iron grade of tailings in the second plant was lesser by 2% and the iron recovery noted to be higher by 2%. The energy consumption decreased by 2 kWh/t of the ground ore in the second plant. As a result, the second plant was considered to be more efficient.

Diversity of Arbuscular Mycorrhizal Fungi from Liberica Tungkal Jambi Coffee Plant Rhizosphere on Peatland

Arbuscular Mycorrhizal Fungi (AMF) diversity found in Liberica Tungkal Jambi coffee plant rhizosphere which planted on peatland in Tanjung Jabung Barat, Jambi Province has not been reported. The existence of various types of AMF is important to know because AMF can increase growth and production of coffee plant. This study aims to identify the diversity of AMF species from coffee plant rizosphere on peatlands in Tanjung Jabung Barat. The soil samples were taken from the coffee plant rhizosphere in Parit Pudin, Senyerang, and Serdang Jaya villages at a 0-20 cm depth. The isolation was carried out by Pacioni’s wet screening technique and continued by centrifugation technique from Brunndret, while spore identification was performed based on morphological characterization and its response to Melzer’s solution. The results showed that both in Parit Pudin and Senyerang villages found two genus, i.e. Acaulospora and Glomus, whereas in Serdang Jaya Village only Glomus was found. In Parit Pudin obtained 1 Acaulospora sp. and 6 Glomus sp., in Senyerang found 3 Acaulospora sp. and 6 Glomus sp., and in Serdang Jaya only found 6 Glomus sp. In Parit Pudin village, the spores abundance of Acaulospora sp. and Glomus sp. were 5 and 63 spores per 50 g of soil samples. In Senyerang village, the spores number of Acaulospora sp. and Glomus sp. were 57 and 49.5 spores per 50 g of soil samples, while in Serdang Jaya Village, the number spores of Glomus sp. as much as 46.83 spores per 50 g of soil samples. In all locations studied, there were various types of AMF with different numbers of spores. Spores found in soil samples showed variations in spore shape, spore color, attachment of hypha stalks, and spore walls.

Effects of simultaneous ultrasonic treatment on the separation selectivity and flotation kinetics of high-ash lignite

The purpose of this study was to investigate the effects of conventional flotation and simultaneous ultrasonic flotation in the pulp/froth zones on the separation selectivity and kinetics of high-ash lignite flotation. Particularly, the mechanism of ultrasonic flotation in the froth zone, which improved the flotation performance of lignite, was elucidated. Flotation tests, wet screening, SEM, and froth layer observation tests were employed to reveal the mechanism by which simultaneous ultrasonic flotation improved lignite flotation. The flotation results indicated that the lowest concentrate ash content was obtained using ultrasonic flotation in the pulp zone, while the highest concentrate yield and water recovery were achieved using ultrasonic flotation in the froth zone. The wet screening and SEM results indicated that ultrasonic flotation in the pulp zone afforded the best surface cleaning on the coal surface, which significantly improved the flotation selectivity of lignite. Ultrasonic treatment in the froth zone produced large bubbles and a thin froth layer due to ultrasonic cavitation and oscillation, thereby improving the recovery of fine particles by water entrainment. However, simultaneous ultrasonic treatment in the froth zone did not improve the separation selectivity of lignite flotation. In addition, the second-order model with rectangular distribution of floatability provided the best fit with the experimental data of all the flotation types, based on the analysis of the model fit and stability. Notably, the flotation rate constants of ultrasonic flotation in the froth and pulp zones were 1.8981 min−1 larger and 1.476 min−1 smaller, respectively, than those of conventional flotation.

Coupled DEM-SPH simulations of wet continuous screening

During screening, a liquid stream, besides the vibration, can be applied for the acceleration of the separation. The discrete element method coupled with the smoothed particle hydrodynamics (DEM-SPH) is used to numerically analyse wet continuous screening here. Within the applied DEM-SPH a new simple model for the representation of the screening surface is suggested in this study. In this model, the influence of the screening surface on the fluid is represented using external forces, which act on the SPH particles in close vicinity of the screen. A required validation of the DEM-SPH method for the analysis of a vibrated particle-laden system is performed by comparing obtained DEM-SPH results with the results derived using the DEM coupled with finite volume method. The performed simulations of dry and wet continuous screening demonstrate that flowing water, in most simulated cases, accelerates the separation of particles. The presented study demonstrates the potential of the coupled DEM-SPH method for the analysis of wet screening processes. To our best knowledge, the simulation of wet screening using a two-way coupled numerical DEM-SPH approach not resolving the flow around individual particles is demonstrated in the scientific literature for the first time.

Recycling valuable metals from spent lithium-ion batteries by ammonium sulfite-reduction ammonia leaching

The cathode powder is obtained by wet crushing and screening, and the leaching behavior of Li, Ni, Co, Cu, and Al is then investigated using a ternary leaching system composed of ammonia, ammonium sulfite, and ammonium bicarbonate. Ammonium sulfite is necessary as a reductant to improve the Li, Ni, and Co leaching efficiencies, and ammonium bicarbonate acts as a buffer in ammoniacal solutions. A detailed understanding of the selective leaching process is obtained by investigating the effects of parameters such as the leaching reagent composition, leaching time (0–300 min), temperature (40–90 °C), solid-to-liquid ratio (10–50 g/L), and agitation speed (300–700 rpm). It is found that Ni and Cu could be almost fully leached out, while Al is hardly leached and Li(60.53%) and Co(80.99%) exhibit a moderate leaching efficiency. The results show that the optimum solid-liquid ratio of the leaching system is 20 g/L, and the increase of temperature and reaction time is beneficial to metal leaching. The leaching kinetics analysis shows that the chemical reaction control explains the leaching behavior of Li, Ni, and Co well. Therefore, this work may be beneficial for further recycling valuable metals from leaching solutions by introducing an extraction agent.

Extractions of size granding classes in undersize

On the basis of averaging of 544 balances of grain-size screening products distribution of the largeness classes extraction coefficients are set in a subsize product at dry and wet preparatory screening of ordinary coal and shallow machine class deslurring. Findings can be used for determination of indexes of the indicated technological operations at the calculations of quality-quantitative and water-slime coal preparations factories charts.

Structure based virtual screening, 3D-QSAR, molecular dynamics and ADMET studies for selection of natural inhibitors against structural and non-structural targets of Chikungunya

The transmission of mosquito-borne Chikungunya virus (CHIKV) has large epidemics worldwide. Till date, there are neither anti-viral drugs nor vaccines available for the treatment of Chikungunya. Accumulated evidences suggest that some natural compounds i.e., Epigallocatechin gallate, Harringtonine, Apigenin, Chrysin, Silybin, etc. have the capability to inhibit CHIKV replication in vitro. Natural compounds are known to possess less or no side effects. Therefore, natural compound in its purified or crude extracts form could be the preeminent and safe mode of therapies for Chikungunya. Wet lab screening and identification of natural compounds against Chikungunya targets is a time consuming and expensive exercise. In the present study, we used in silico techniques like receptor-ligand docking, Molecular dynamic (MD), Three Dimensional Quantitative Structure Activity Relation (3D-QSAR) and ADME properties to screen out potential compounds. Aim of the study is to identify potential lead/s from natural sources using in silico techniques that can be developed as a drug like molecule against Chikungunya infection and replication. Three softwares were used for molecular docking studies. Potential ligands selected by docking studies were subsequently subjected 3D-QSAR studies to predict biological activity. Based on docking scores and pIC50 value, potential anti-Chikungunya compounds were identified. Best docked receptor-ligands were also subjected to MD for more accurate estimation. Lipinski’s rule and ADME studies of the identified compounds were also studied to assess their drug likeness properties. Results of in silico findings, led to identification of few best fit compounds of natural origin against targets of Chikungunya virus which may lead to discovery of new drugs for Chikungunya.Communicated by Ramaswamy H. Sarma

A STUDY OF FLUID BED GRANULATION OF PRAVASTATIN TABLET USING DESIGN OF EXPERIMENTS

Objective: The objective of this study was to reduce size and weight of pravastatin tablet through quality by design approach; potential factors (spray rate, atomizing pressure, and inlet temperature) which could influence on the production process for critical process parameters of wet granulation using fluid-bed granulator were examined.Methods: The manufacturing process of the reduced weight and size formulation pravastatin tablet involves wet granulation, drying, granulate screening, blending, and tableting. Design of experiments study for wet granulation of the reduced weight/size pravastatin tablet was produced on 11 combinations of three factors (spray rate, atomizing pressure, and inlet temperature), which were chosen through initial risk assessment. The process of wet granulation was rated by measuring four responses: loss on drying (LOD) (%), bulk density (g/ml), product temperature (°C), and dissolution similarity (f2).Results: It was measured that LOD varied from 1.46 to 3.24%, bulk density from 0.34 to 0.51 g/ml, product temperature from 40.12 to 51.69°C, and dissolution (f2) of pravastatin from 52.14 to 58.91. Control strategy for wet granulation production of the reduced weight and size pravastatin tablet by our results demonstrated that the most optimized condition of three factors for wet granulation is spray rate (3–5 g/min), atomizing pressure (about 1 bar), and inlet temperature (65–90°C), respectively. Updated risk assessment and justification by all experimental data safely existed within the range of acceptance criteria were presented.Conclusion: It can be concluded that the ideal ranges of three factors (spray rate, atomizing pressure, and inlet temperature) in wet granulation were successfully identified.

Characterization and Beneficiation of Dry Iron Ore Processing Plant Reject Fines to Produce Sinter/Pellet Grade Iron Ore Concentrate

Characterization and beneficiation of dry iron ore processing plant reject fines of Khondbond region, India, was investigated. Different characterization techniques viz. size analysis, size-wise chemical and density analysis, X-ray diffraction analysis, sink-float analysis, thermo gravimetric analysis, scanning electron microscopy, and QEMSCAN were carried out. Based on characterization results, two process flow sheets comprising wet screening followed by conventional gravity concentration and two stage classification with different beneficiation routes were used to recover the iron values from reject fines containing 58.73% Fe, 5.54% Al2O3, and 6.6% SiO2. Finally, suggested flow sheet comprising of two stage classification and advance gravity concentration followed by the combination of grinding, classification, and froth flotation produced iron concentrate of 2.36% Al2O3 with 75.8% yield which can be used in sinter/pellet making.

Highly deleterious variations in COX1, CYTB, SCG5, FK2, PRL and PGF genes are the potential adaptation of the immigrated African ostrich population

Because of variable inconvenient living conditions in some places around the world, it is difficult to collect reliable physiological data for ostriches. Therefore, this study aims to provide a comprehensive in silico insight for the nature of polymorphism of important genetic loci that are related to physiological and reproductive traits. Sixty-nine mature ostriches ranging over half of Iraq were screened. Six exonic genetic loci, including cytochrome c oxidase I (COX1), cytochrome b (CYTB), secretogranin V (SCG5), feather keratin 2-like (FK2), prolactin (PRL) and placenta growth factor (PGF) were genotyped by PCR-single stranded conformation polymorphism (SSCP). Thirty-six novel SNPs, including seventeen nonsynonymous (ns) SNPs, were observed. Several computational software programs were utilized to assess the extent of the nsSNPs on their corresponding proteins structure, function and stability. The results showed several deleterious functional and stability changes in almost all the proteins studied. The total severity of each missense mutation was evaluated and compared with other nsSNPs accumulatively. It is evident from the extensive cumulative in silico computation that both p.E34D and p.E60K in PGF have the highest deleterious effect. The cumulative predictions from the present study are an impressive guide for the genotypes of African ostriches, which bypassed the expensive protocols for wet laboratory screening, to identify the effects of variants. To the best of our knowledge, this is the first investigation of its kind on the analyses and prediction outcome of missense mutations in African ostrich populations. The highly deleterious nsSNPs in the placenta growth factor are possible adaptive mutations which might be associated with adaptation in extreme and new environments. The flow and protocol of the computational predictions can be extended for various wild animals to identify the molecular nature of adaptations.

Exploration and Identification of the Indigenous Arbuscular Mycorrhizae Fungi (AMF) in the Rhizosphere of Citronella (Andropogon nardus L.) in the Dry Land Regions in West Sumatra Province, Indonesia

Climate change has an impact on the transition function of the wetland to dry land. This shift led to the increased of the dry land area with less potential for food crops and horticulture. Citronella plants have been identified as one of the lemongrass crops that able to survive in the dry land area. However, the resulting yield to produce citronella oil is still very low at 0.8 to 1.0%. In this regard, Arbuscular Mycorrhizae Fungi (AMF) was indicated to be able to increase the absorption of nutrients and water in many plants in the dry land regions. The type of AMF that compatible enough with citronella plant was not identified yet. The purpose of this study was to determine the number and diversity of AMF in the rhizosphere of indigenous citronella (lemongrass). The study was conducted from August to November 2015 in three regions of cultivation of citronella using survey methods and wet screening. The study found four important AMF geniuses in the study site; there are Glomus, Acaulospora Gigaspora, and Sclerocystis.

Low-Temperature Atomic Layer Deposition of MoS2 Films.

Wet chemical screening reveals the very high reactivity of Mo(NMe2 )4 with H2 S for the low-temperature synthesis of MoS2 . This observation motivated an investigation of Mo(NMe2 )4 as a volatile precursor for the atomic layer deposition (ALD) of MoS2 thin films. Herein we report that Mo(NMe2 )4 enables MoS2 film growth at record low temperatures-as low as 60 °C. The as-deposited films are amorphous but can be readily crystallized by annealing. Importantly, the low ALD growth temperature is compatible with photolithographic and lift-off patterning for the straightforward fabrication of diverse device structures.

Effect of Wet Screening in the Elastic Properties of Dam Concrete: Experimental In Situ Test Results and Fit to Composite Models

AbstractThis paper proposes the use of the maturity method and a two-phase composite model for the prediction of dam concrete modulus of elasticity. The methodology was validated with test results obtained from experimental in situ setup using creep cells placed in the dam’s body, subjected to variable environmental conditions. It is shown that composite models can be used to predict the modulus of elasticity of in situ dam concrete based on the modulus of elasticity of the wet-screened concrete.