Combination Of Lime Research Articles

E-CatBoost: An efficient machine learning framework for predicting ICU mortality using the eICU Collaborative Research Database.

Improving the Intensive Care Unit (ICU) management network and building cost-effective and well-managed healthcare systems are high priorities for healthcare units. Creating accurate and explainable mortality prediction models helps identify the most critical risk factors in the patients’ survival/death status and early detect the most in-need patients. This study proposes a highly accurate and efficient machine learning model for predicting ICU mortality status upon discharge using the information available during the first 24 hours of admission. The most important features in mortality prediction are identified, and the effects of changing each feature on the prediction are studied. We used supervised machine learning models and illness severity scoring systems to benchmark the mortality prediction. We also implemented a combination of SHAP, LIME, partial dependence, and individual conditional expectation plots to explain the predictions made by the best-performing model (CatBoost). We proposed E-CatBoost, an optimized and efficient patient mortality prediction model, which can accurately predict the patients’ discharge status using only ten input features. We used eICU-CRD v2.0 to train and validate the models; the dataset contains information on over 200,000 ICU admissions. The patients were divided into twelve disease groups, and models were fitted and tuned for each group. The models’ predictive performance was evaluated using the area under a receiver operating curve (AUROC). The AUROC scores were 0.86 [std:0.02] to 0.92 [std:0.02] for CatBoost and 0.83 [std:0.02] to 0.91 [std:0.03] for E-CatBoost models across the defined disease groups; if measured over the entire patient population, their AUROC scores were 7 to 18 and 2 to 12 percent higher than the baseline models, respectively. Based on SHAP explanations, we found age, heart rate, respiratory rate, blood urine nitrogen, and creatinine level as the most critical cross-disease features in mortality predictions.

Stabilization of a highly expansive soil using waste-tire-derived aggregates and lime treatment

This study investigates the combined efficacy of waste-tire-derived aggregate (TDA) materials and hydrated lime on the compactability, compressive strength and swelling potential of a highly expansive soil from South Australia. A total of 21 mix-designs, covering a comprehensive range of soil–TDA–lime combinations, were examined through standard Proctor compaction, unconfined compressive strength (UCS) and oedometer swell tests. The mobilized UCS exhibited a ‘rise–fall’ behavior, peaking at 5% TDA content and subsequently decreasing (monotonically) for higher inclusions of TDA. Increasing the TDA mean particle size (from 1.67 to 3.34 mm) also contributed positively to the UCS development. Addition of TDA to the soil/soil–lime-blends produced notable reductions in the swelling potential; the reduction was primarily governed by higher TDA contents, and, to a lesser degree, for larger TDA mean particle sizes. However, the role of TDA particle size in reducing swelling was found to be more significant than that of enhancing the UCS. As expected, lime treatment of the soil–TDA blends provided major further improvements to the UCS and swelling potential reduction; the achieved UCS improvements being positively proportional to the lime content and curing time. In view of the experimental results, soil–lime blends containing TDA to soil–lime mass ratios of up to 10% (preferably employing coarse-sand-sized equivalent TDA) can be deemed as suitable choices (capable of adequately mitigating the swelling potential, while simultaneously enhancing the UCS).

The Effect of WHA and Lime for Shear Strength of Clay Stabilized by Cement

With the use of the additive, the clay's shear strength and bearing capacity increased. Usage waste material, Wooden Hush Ash (WHA), is tiny. The silicate content of WHA is almost the same as RHA. This study aims to utilize ASK for a stabilization material of high plasticity clay to increase shear strength. Unconfined Compression Strength (UCS) tests were performed to compare the UCS value of clay; clay with 5% cement; clay with lime; clay-cement with WHA; clay-cement with lime and WHA; and clay with lime and WHA. Before the UCS test, the sample was separated into two groups: with and without curing for 28 days, and with and without soaking for 4 days. While in conditions unsoaked, the qu value is uniform. Results show, without curing and soaked, qu values of all variations have the same value in the range of 350 kPa to 380 kPa. In conditions with curing 28 days with and without soaked, qu values range from 365 kPa to 485 kPa for mixtures with WHA and a combination of lime with ASK. While adding of 10% lime additive increases the qu value to 1100 kPa UCS testing results prove, with and without curing and soaked, lime is more optimal to increase the value of UCS than WHA. Replacement lime with WHA by 4% to 6% increases the qu value from 160 kPa to 465 kPa and 485 kPa and 110 kPa to 440 kPa to 475 kPa of soaked and unsoaked condition respectively. WHA can be used to reduce lime in soil stabilization.

Optimizing of the Parameters of Coconut Sugar Production Using Taguchi Design in Riau, Indonesia

The quality of coconut sugar produced from Indragiri Hilir Regency, Riau Province, is still fluctuating and has not compliant with SNI-01-3743 of 1995, which incorrect parameters in its production may cause incorrect parameters in its production. Optimizing of production parameters is needed to maintain the quality of coconut sugar. Coconut sugar quality indicators can be determined from the physical-chemical and organoleptic characteristics. Therefore, it is necessary to modify the parameters of coconut sugar production, aiming to obtain optimal production parameters to produce a standard production process and coconut sugar following consumer needs and SNI. The experimental design uses the Taguchi method, which consists of 4- factor variables: (1) the type of sap preservative, (2) defoaming agent, (3) the time of tapping, and (4) the cooking temperature of the sap. The multi-response loss function approach was used to select the best production process parameters based on the typical characteristics of qualities. The results showed that the optimal production parameters were obtained in a combination of mangosteen peel and lime as sap preservative, coconut milk as a defoaming agent, long-time tapping time of 8 hours (heating) +16 hours, and cooking temperature of 135oC with a yield of 15.58%, part of water-insoluble in 0.07%, (ΔE) color 62.30, hardness 99.92 N, moisture content 6.87%, ash content 1.96%, sucrose content 77.77%, reducing sugar content 8.09% with organoleptic test values close to 4 ( like) and equal SNI.

Evaluation of marine dredged sediment as reactive powder compared to ground basaltic pyroclastic materials for the development of eco-friendly lime-pozzolan binders

The combination of lime with natural pozzolans for the production of binders in masonry construction dates back to ancient times. These were largely ignored with the industrialization of the building sector even though their use for specific applications is of interest. The use of lime-pozzolan binders with the least amount of lime is a relevant opportunity to reduce carbon emissions due to the decarbonation of limestone for the production of quicklime but also to introduce new alumino-silicate materials. In this context, the present investigation intends to relate marine dredged sediment to pyroclastic materials and to mix it with hydrated lime without any thermal treatment but after micronization. The blends were moist cured either at 20 °C or 50 °C and the paper will discuss the pozzolanic reactivity through the study of compressive strength and reaction kinetics from 3 days to 180 days. Reaction product assemblage, microstructure, and porosity refinement were also addressed after advanced curing ages. Results have well illustrated the long-term pozzolanic reactivity of the marine sediment cured at 50 °C through the whole combination of initially available lime after 60 days and the compressive strength development providing 12 MPa after 180 days.

Pozzolanic and hydraulic activity of bauxite for binder production

Bauxite is mainly used to produce aluminium and calcium aluminate cements. Both applications carry high environmental impacts. However, the carbon emissions generated from mining bauxite (3–5 kg CO2e/t) are negligible when compared those generated for aluminium or cement production (620–700 kg CO2e/t for CEM II). Hence, an alternative use for bauxite would lower environmental impacts worldwide. This paper measures the pozzolanic and hydraulic capacity of raw and thermally activated bauxite with a view to use it, as a binder, in construction.The results indicate that the bauxite is pozzolanic and, when fired over 900 °C it becomes slightly hydraulic. An amorphous reactive phase begins to appear at 300 °C, but the lime binding potential is enhanced at 550 °C because most of the aluminium is in amorphous form. Some active phases (except for ϒ- Al2O3) could not be detected with XRD due to their amorphousness. However, their pozzolanicity was evidenced with direct and indirect measurements.The bauxite's pozzolanic and mechanical indices are high, comparable or superior to other pozzolanic and cementing materials. Gibbsite, boehmite and kaolinite are the main phases in the bauxite. Their layered atomic structures with high specific surface areas (SSA) and active surface hydroxyls that enhance adsorption, and hence nucleation, precipitation and dissolution, provide a high pozzolanic activity. The high kaolinite content, and the presence of the highly-reactive, kaolinite-polymorph nacrite, enhance reactivity, and the presence of sulphates also contributes to the initial activity.The SSA of the bauxite particles, is superior to CEM II and other pozzolanic and cementing materials, and heating, even at low temperature (300 °C), drastically increases the SSA of the particles (by∼60%). The methods that determine initial pozzolanic activity rate the 550 °C bauxite as the most active, while the mechanical methods rate the 700–800 °C bauxites as the most reactive. This is because the high SSA of the 550 °C bauxite enhances lime combination in the earlier stages of the pozzolanic reaction, while the 700–800 °C bauxite has the highest amorphous/active alumina content which control late pozzolanic activity. As evidenced with XRD, at 700–800 °C, boehmite has disappeared, transformed into amorphous transition aluminas, and kaolinite has completely turned into reactive metakaolin.

Compressed unfired blocks made with iron ore tailings and slag

Growing demand for houses in urban India has increased the requirements for construction materials such as clay fired bricks and cement blocks. At the same time, conventional practice of brick manufacturing is not environment friendly due to high energy consumption and CO2 emissions during various stages of its production. Therefore, recent trend in research has been directed towards utilization of various industrial wastes and methods, which emerge as sustainable alternatives for environmental concerns arising in the construction industry. This study focused on utilizing mining waste, namely iron ore tailing (IOT) in development of stable blocks. It has reported various properties of compressed unfired blocks formed by IOT and ground granulated blast furnace slag (GGBS) in varying proportions and with a fixed amount of lime. The combination of GGBS and lime was found to be suitable in stabilizing IOT towards block production. Furthermore, a maximum compressive strength of 7.7 MPa was achieved for blocks after 28 days of air curing. Also, the addition of GGBS has reduced the water absorption and apparent porosity of the IOT blocks, confirming the positive interaction between IOT, GGBS and lime. It also indicates the prospective of blended binders in improving the compactness of the blocks, which will have direct influence on the durability and service life of the blocks. Finally, the results show that most of the developed blocks satisfy the requirement of IS 1077 specification and can be used in various applications such as load and non-load bearing walls, framed structures, foundations and pedestrian walkways.

Effect of fixator on color performance of bark extract from three tropical wetland species for fabric dye

Fixation is a stage in dyeing fabric or batik fabric with natural dyes to obtain the desired color and bind the color so that it does not fade quickly due to sweat, washing, sunray, and rubbing. Three fixators used as color binders were alum (Al2[SO4]3), lime (CaCO3), and tunjung (FeSO4). Each material showed a different color on each extract. This activity aimed to observe the color performance of bark extracts from three wetland species applied to batik fabric with 1 or 2 combinations of fixators. The results showed the color performance of batik fabric depended on the bark of tree species and the kind of fixator. The performance of bark extract with fixators produced darker and sharper colors than without the use of fixators. The application of lime on Rhizophora apiculata Bl. bark extract produced dark moderate orange color, while the combination of lime and tunjung produced very dark orange (Brown tone). The combination of lime and tunjung on Acacia mangium Willd and the Terminalia catappa L. barks gave a dark moderate orange color with different intensities. In contrast, the combination of alum and tunjung on Terminalia catappa L. bark extract produced a very dark greyish orange color.

Productivity of Groundnut as Influenced by Integrated Use of Lime, Organics, Inorganic Fertilizers, and Biofertilizers in Acidic Soil of Tripura

A field experiment was carried out on acidic soil of Khowai district of Tripura during 2017 and 2018 to study the effect of application of various combinations of lime, farmyard manure (FYM), poultry manure (PM), and rhizobium with the recommended doses of NPK on groundnut (Arachis hypogaea L.) productivity. The experiment was conducted in a completely randomized block design with 13 treatments; each replicated thrice. The application of the recommended dose of NPK @ 20:60:40 kg ha-1 along with lime @ 1/5th Lime Requirement (LR), PM @ 5 t ha-1 and seed treatment with Rhizobium @ 20 g kg-1 of seed significantly increased the seed yield and recorded the highest Benefit : Cost ratio (B:C) compared to the recommended dose of NPK alone as well as other treatments combinations. Thus, in achieving higher groundnut productivity with better return in acidic soils of Tripura, integrated use of inorganic fertilizers (NPK @ 20:60:40 kg ha-1) combined with lime @ 1/5th LR, PM @ 5 t ha-1, and seed treatment with Rhizobium @ 20 g kg-1 of seed might be recommended.

Selective depression mechanism of combination of lime and sodium humate on arsenopyrite in flotation separation of Zn–As bulk concentrate

Lime (CaO) and sodium humate (NaHA) were used as the combined depressant for arsenopyrite pre-treated by CuSO4 and butyl xanthate. Micro-flotation tests show that the combined depressant CaO and NaHA achieved the selective depression of arsenopyrite. Closed-circuit lab-scale test results indicate that the synergistic effect of CaO+NaHA achieved a satisfactory flotation separation of sphalerite and arsenopyrite, for which the Zn grade and recovery of Zn concentrate were 51.21% and 92.21%, respectively. Contact angle measurements, adsorption amount measurements and X-ray photoelectron spectroscopy analysis indicate that the dissolved calcium species (mainly as Ca2+) were adsorbed on the mineral surfaces, thereby promoting NaHA adsorption. Moreover, the surface of the arsenopyrite absorbed more amount of calcium species and NaHA than that of the sphalerite, thereby accounting for the strong hydrophilic surface of arsenopyrite. The adsorption of NaHA on arsenopyrite was mainly chemical adsorption through its carboxyl groups and Ca atoms, whereas that on sphalerite surface was relatively weak.

Effects of Lime and Compost on Chemical Characteristics and Soil Hydraulic Conductivity of Alfisols at ATP Jatikerto Coffee Plantation

<span>Coffee in Indonesia is currently one of the most important plantation commodities. Inappropriate management of coffee plantations causes low soil quality especially in smallholder coffee plantations, one of which is the density (compaction) of soil in coffee plantations that has a clayey</span><span> t</span><span>exture. This study was aimed to analyze the effect of lime and compost application on the chemical characteristics and saturated hydraulic conductivity (SHC) of the soil. The experiment was carried out at Glasshouse Agro Techno Park (ATP) Jatikerto from September 2020-February 2021. Soil samples were taken from coffee gardens at a depth of 0-30 cm and 30-60 cm. The incubation study in the greenhouse used Factorial Complete Randomized Design with 12 treatments and 3 replications. Incubation was carried out for 8 weeks. Treatment factors include the depth of the soil sample (0-30 cm and 30-60 cm); compost (0 tons ha<sup>-1</sup>, 10 tons ha<sup>-1</sup></span><span lang="IN"> and</span><span>20 tons ha<sup>-1</sup>) and lime (0 tons ha<sup>-1</sup> and 2.5 tons ha<sup>-1</sup>). Results showed that the treatment combination of </span><span lang="IN">2.5 ton ha<sup>-1</sup> of </span><span>lime and </span><span lang="IN">20 ton ha<sup>-1</sup> of </span><span>compost gave the best results measured by the availability of N and K nutrients and an increase in the </span><span lang="IN">SHC</span><span>. However, results in this treatment were almost the same as treatment of </span><span lang="IN">2.5 ton ha<sup>-1</sup> of </span><span>lime and </span><span lang="IN">10 ton ha<sup>-1</sup> of c</span><span>ompost. </span><span>The combination of compost and lime has a significant effect on improving the chemical characteristics of the soil and the </span><span lang="IN">SHC </span><span>of the topsoil (0-30 cm) and the subsoil (30-60 cm).</span>

Treatment of industrial electroplating wastewater for metals removal via electrocoagulation continous flow reactors

AbstractA real industrial electroplating rinsing wastewater was collected and subjected to physical and chemical examination. The study showed that it can be categorized as high strength wastewater, at pH- 2, COD 1430 mg/l, and high level of metals above permissible limits, namely: 150, 30, 25, and 2.9 for Ni, Cu, Zn, and Fe mg/l respectively. Therefore, metals must be adequately removed before discharging to avoid any hazardous impact on the environment. Similar synthetic wastewater was prepared to study the effect of chemical coagulation for the precipitation of metals. The optimum removal rate was achieved by using a combination of lime and ferric chloride at 100 and 30 mg/l respectively. The chemically treated electroplating wastewater was subjected to an electrocoagulation study. A comparison between iron and stainless-steel electrodes for the removal of metals was investigated. Furthermore, the effect of different electric voltages, and contact time on metals removal efficiency were also examined. It was found that the optimum removal capacity was achieved when a stainless steel electrode was employed in the presence of ferric chloride as coagulant, at 10 volts, 30 min. contact time, and pH 9 for synthetic solution. In a batch treatment system, the real industrial wastewater was treated at the predetermined optimum operating conditions; the removal of metals was 92.1%, 87.8% and 82.9% for Ni. Zn, and Cu respectively. By employing a continuous flow reactor for the treatment of the same real wastewater and under the same operating conditions, metals removal rate increased to 98.9%, 97.4% and 96.6% for Ni. Zn, and Cu respectively. The level of metals in the final treated wastewater copes with Egyptian Environmental Regulation. The overall results confirmed that the electro-coagulation (EC) technology offers an effective alternative process in combination with the conventional chemical coagulation process for reaching high removal performance of toxic metals from the electroplating wastewater. The advantage of EC technique is achieving high treatment efficiency instead of expensive chemical reagents, high construction cost and/or other conventional processes. In addition, the final treated water can be reused for rinsing process in the electroplating industry and/or discharging without any environmental hazard effect. It is also recommended to employ solar energy instead of electricity to reduce cost of operation.

Strength characteristics of kaolin clay mixed with RHA, sand and lime

Kaolin clays are inadequate for supporting overlying pavement and foundation structures due to their low bearing capacity and volumetric variations. Soil stabilization is the possible solution for resolving these issues and increasing the soil's bearing capacity. The viability of using an agricultural waste product like rice husk ash along with sand and lime as effective medium expansive kaolin clay stabilizers was investigated through experimental assessment. The unconfined compressive strength and split tensile strength of samples at optimum moisture content were evaluated using 28 different combinations of RHA (10%, 20%, and 30% of the weight of untreated clay), lime (6%, 9%, and 12% of the weight of untreated clay), and sand (10%, 15%, 20%, and 25% of the weight of untreated clay) over three distinct phases of curing (0, 7, and 28 days). The MDD increases with the addition of sand, while the OMC decreases. With increasing curing periods, UCS values increased. The samples for the UCS test and the STS test were prepared and cured in a humidity chamber at three different lime contents (6%, 9%, and 12% by weight). The initial UCS of pure kaolin clay was 155.68 kPa, which improved to 1311.23 kPa after 9% lime treatment with 28 days of curing. The STS of untreated clay was 14.2 kPa, which improved to 36.94 kPa after 9% lime treatment with 28 days of curing. According to the findings, a mixture of clay, RHA, lime, and sand can be employed as lightweight fill material in embankments and retaining walls. It also provides a safe option for managing rice husk ash as an excellent subgrade element for pavement construction.

Вдосконалення технології виробництва та покращання якісних характеристик комплексного флюса

The article considers the possibility of increasing the efficiency of the modern agglomeration process, which is carried out by improving the technology of complex flux production. The domestic and world experience of development and use in the processes of smelting of metallurgical raw materials of a new type - complex flux - is summarized. It is noted that this type of flux adds a significant set of mineralogical compounds to the sintering charge, which significantly improve the sintering conditions and the quality of the sintering raw materials. A method of producing a complex flux by combining the processes of calcining limestone and the formation of calcium ferrites is proposed. The possibilities and advantages of using specialized software for the analysis of limestone dissociation reactions under different conditions are shown. One of the directions for the production of a complex flux of a given composition and properties is highlighted, the basis of which is the production of combined granules formed by pieces of limestone with a coarseness and a shell of iron ore materials (concentrate, iron ore), by combining the processes of calcination of limestone and the formation of calcium ferrites. Thermodynamic analysis shows the high reliability of the interaction of lime with oxides of ore material with the formation of a complex flux of the given composition and properties. The process is implemented by sintering on a conveyor machine using agglomeration technology. The main parameters of the technological mode of complex flux production have been developed. It has been proven that in the development and improvement of the technology for the production of complex flux from limestone granules with rolling of iron-containing material, the correct choice of limestone size, fuel, as well as the values of other technological parameters is of great importance. The results of the conducted research confirm the technological feasibility of the chosen direction of complex flux production due to the combination of lime and ferrite heat production processes.

Hygric properties of wheat straw biocomposite containing natural additives intended for thermal insulation of buildings

Straw concrete is a biobased composite developed for thermal insulation of new buildings and thermal rehabilitation of old buildings. It is made of the combination of wheat straw, lime or plaster binder and natural additives (hemoglobin, casein, gelatin). The natural additives are used to improve the thermal and mechanical properties of the material. The characterization of these composites has shown an attractive thermal conductivity and an acceptable mechanical strength. The present paper focuses on the hygric characterization of these materials which have different constituents (straw aggregates, binder and additives). Three properties were experimentally determined, namely, sorption–desorption curves, water vapor permeability and moisture buffer value (MBV). These hygroscopic properties are of great importance when it comes to the comfort of the building. The isothermal water vapour diffusivity was also estimated from the sorption curve and the water vapor permeability. The impact of the sample thickness on the moisture buffer value (MBV) was also highlighted. The results showed that the studied composites have excellent hygric properties which can contribute significantly to ensure hygrothermal comfort in buildings. These hygric performances are competitive with those of other insulating bio-based materials studied in the literature and better than those of conventional materials used in construction.

Effect of cement kiln dust, lime and fly ash on metal leaching characteristics of oil sands tailings from Alberta, Canada

The oil sands industry of Alberta generates huge amounts of tailings in a slurry form that typically require up to 40 years to consolidate in very large tailings ponds which are up to 150 m in height. Cement kiln dust (CKD), a byproduct of the ordinary Portland cement manufacturing process, as well as lime and fly ash, collectively referred to as geopolymers, may have the potential to reduce the tailings slurry consolidation period from 40 years, thus affecting the sustainability of such tailings facilities. However, first, it must be demonstrated that these geopolymers will also decrease the metal leaching from thickened tailings (TT) and mature fine tailings (MFT) from the oil sands industry. This study was focused on the use of geopolymers to reduce the environmental impact of TT- and MFT-tailings in the Alberta oil sands industry. Toxicity characteristics leaching procedure (TCLP) and static leaching test (SLT) was used to examine the leaching of metals from tailings, with the SLT test effectively mimicking the leaching process in the tailings ponds environment. Under non-acidic conditions corresponding to the SLT test results, iron concentrations with values of about 530-705 ppm were found to be lower than previous studies on oil sand tailing ponds (2400 ppm). Results showed that geopolymer amendment of TT and MFT significantly reduced the leaching of heavy metals. SLT tests showed that amendment of MFT with 7% CKD decreased Pb, Mn, and Fe leaching, whereas TT-amended with 4% CKD decreased Cu, Pb, Zn, Mn, and Fe. Overall, the CKD amendment of TT showed more than 95% efficiency in the reduction of leaching of all heavy metals. In TCLP tests, TT-amended with 2% FA decreased the leaching of Pb and Ni to acceptable levels with substantial efficiency in reducing the leaching of Fe, Cu, and Zn. TCLP tests also showed that among different amendments, TT-amended with 4% CKD or 2% FA were the most effective proportions for controlling metal leaching from TT, while MFT-amended with 7% lime/FA or 3% CKD were the effective proportions for reducing metal leaching from MFT. Thus, it is deduced that CKD at 3%-4% w/w amendment would work best for reducing leachate levels of both TT and MFT. While amendment of tailings by means of a combination of fly ash and lime also were effective in reducing the leaching of metals, these two geopolymers were not as effective as the CKD amendment.

Comparative Assessment of Deformation Under Plate Bearing Test and CBR Test for Subgrade Soil

A significant variation in the strength and deformation behavior of subgrade soil when tested in the laboratory and in the field. However, correlation of such variables is essential to evaluate the quality of the constructed subgrade. An attempt has been made in the present investigation to assess the deformation of control and stabilized subgrade soil in the laboratory and in the field. California bearing ratio (CBR) test was conducted in the laboratory and the static plate bearing test (PBT) was conducted in the field. Subgrade soil samples were stabilized with 6% lime, 17 % Cationic Emulsion, and combination of lime and emulsion. Similar stabilization was conducted at test sections in the field. The behavior of the control and stabilized soil in deformation under static PBT in the field and CBR in the laboratory was monitored and evaluated. It was noticed that polynomial correlation exists with high coefficient of determination between laboratory and field deformation for stabilized soil. It was observed that the deformation under CBR test decreased after implication of lime by (96 and 88) % for unsoaked and soaked testing conditions respectively. The deformation decreases by (92 and 85.6) % for unsoaked and soaked testing conditions respectively when emulsion was implemented. The deformation decreases by (91 and 88) % for unsoaked and soaked testing conditions respectively when combined stabilization was implemented. However, the deformation under PBT decreases by (75, 56, and 50) % for lime, emulsion, and combined stabilization processes respectively. It was concluded that testing condition (soaked or unsoaked) has no significant impact on the deformation of stabilized soil while it has a significant influence on the deformation of untreated soil under CBR test. On the other hand, the deformation of control soil shows no significant variation among field and laboratory testing in the model, however, the stabilized soil samples exhibit higher influence of field deformation on the polynomial models.

Stabilization of Expansive Soil Using Biomedical Waste Incinerator Ash

Expansive soils undergo high volume change due to cyclic swelling and shrinkage behavior during the wet and dry seasons. Thus, such problematic soils should be completely avoided or properly treated when encountered as subgrade materials. In the present study, the biomedical waste incinerator ash and lime combination was proposed to stabilize expansive soil. Particle size analysis, Atterberg limits, free-swell, compaction, unconfined compression strength, and California bearing ratio tests were conducted on the natural soil and blended with 3%, 5%, 7%, 9%, and 11% biomedical waste incinerator ash (BWIA). The optimum content of BWIA was determined based on the free-swell test results. To further investigate the relative effectiveness of the stabilizer, 2% and 3% lime were also added to the optimum soil-BWIA mixture and UCS and CBR tests were also conducted. In addition, scanning electron microscopy (SEM) tests for representative stabilized samples were also conducted to examine the changes in microfabrics and structural arrangements due to bonding. The addition of BWIA has a promising effect on the index properties and strength of the expansive soil. The strength of the expansive soil significantly increased when it was blended with the optimum content of BWIA amended by 2% and 3% lime.

Pozzolanic and Cementing Activity of Raw and Pyro-Processed Saudi Arabian Red Mud (RM) Waste

This paper investigates the composition, properties and reactivity of a red mud waste generated in Saudi Arabia with a view to find alternative materials to replace construction binders of high environmental impact. The phase transformation triggered by the sintering of the RM up to 1000°C is determined with thermal and X-Ray Diffraction analyses. Reactivity is investigated with chemical and physical methods including the Chapelle test, setting times, mechanical index and microscopy. The RM is clearly pozzolanic, and its activity is mainly due to the reaction of feldespathoids and the formation of zeolitic and feldspathoid-based hydrates. The positive effects of the thermal treatment are seen below 750°C, and include the loss of water in the zeolite/feldespathoids, and the destruction of the crystal structures of the clay minerals inherited form the parent bauxite. The negative effects of the thermal treatment are evidenced over 750°C, with a decrease in specific surface area, devitrification and crystal formation, whereby the active transition aluminas and the fedespathoids/zeolites (mainly cancrinite) transform into nepheline, tricalcium aluminate (C3A) and gehlenite. Despite the occurrence of nepheline, C3A and gehlenite in the RM sintered at 1000°C, the formation of pozzolanic hydrates that cause setting and strength development are greater at lower temperature. The optimum thermal treatment that enhances pozzolanic activity lies at c.400°C, as evidenced by the highest lime combination, the greatest mechanical index and the fastest set. The RM consists of gibbsite and boehmite, inherited from the bauxite, and cancrinite, chantalite and sodalite formed during the Bayer process. Feldespathoids have formed, instead of zeolites, due to the available silica and the high alkali content of the RM. The quick lime -CaO -, added twice during the refining process, has transformed the original goethite into hematite, and produced cancrinite. The Saudi RM has high SiO2 and high alkalinity, and an abundant specific surface area available for reaction. The chloride and carbon contents are low, and no environmental toxicity is inferred from its chemistry.

Valorization of phosphogypsum as a road material: Stabilizing effect of fly ash and lime additives on strength and durability

Phosphogypsum is a by-product from the phosphoric acid industry following the wet process. Known for its low cost, this process generates large amounts of phosphogypsum, the management of which has so far remained problematic due to the impurities it contains including heavy metals, radionuclides and acidic residuals. It is above all, its acidic nature that hinders its use as a road material since it increases its solubility which in turn makes it sensitive to water variations. This paper presents an investigation on the stabilization of Moroccan phosphogypsum, through neutralizing acidity, while considering both techno-economic and environmental constraints. To this end, mixtures of phosphogypsum and fly ash were prepared then activated with varying quicklime additions (beyond Initial Consumption of Lime) to develop different combinations of phosphogypsum (40–80%), fly ash (20–60%) and lime (4–20%). These have been tested for their mechanical and mineralogical properties at different curing periods (7, 28, 90, 180 days) besides durability against Wetting/Drying cycles, in order to evaluate the stabilizing effect of fly ash and lime. Results from Unconfined Compressive Strength (UCS) tests showed a strength increase with fly ash and lime addition with increasing the curing time. The UCS at 180 days varied between 1 and 3 MPa for formulations containing 4% lime (ICL) while those with 12–20% lime reached 4–7 MPa (12 times higher than UCS at 7days). As for durability, these showed weight losses of up to 10% upon W/D cycles, a strength loss of up to 56% and high porosity compared to formulations with higher lime content which rather gained up to 264% in strength. The influence of curing time and mixture composition on the mineralogy of the prepared composites was assessed through XRD and TGA analyzes highlighting the formation of ettringite as main hydration product responsible for strength development.