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This study aims to develop the alkali activated slag-fly ash concrete (AASFC) using precious slag (PS) ball as the fine aggregate. The slag-fly ash proportion, sodium silicate/sodium hydroxide (SS/SH) ratio and sodium hydroxide concentration are the prime variables. The fresh concrete properties like workability, setting time and the hardened concrete properties of AASFC developed under ambient curing were analyzed and similar way by replacing with fly ash (FA). The sodium hydroxide concentration of 8 M, 10 M and 12 M, SS/SH ratio of 1.0, 1.5 and 2.0, alkaline liquid to binder ratio of 0.35 and variation in slag-fly ash proportion as major inputs for mix design. The test results showed that, the fresh state of AASFC blend has a shorter setting time of 12–16 min, because of calcium mineral from the FA, the workability and setting time of AASFC mix was enhanced by the addition of the tri-sodium phosphate as a retarder. At the higher SS/SH extent, the workability and setting time exaggerated, whereas the increased FA content and sodium hydroxide concentration had a greater influence on the fresh state of concrete. Also, the sodium hydroxide concentration, SS/SH ratio and slag-fly ash proportion are the most inducing parameters on the workability, setting time and strength parameters of AASFC.

ABSTACT Rennet milk curds were prepared under 4 different temperature and acidity conditions. The development of different types of inter-protein chemical bonds (disulfide, hydrophobic, electrostatic, hydrogen, and calcium bridges) was monitored for 60 min after curd cutting. Hydrophobic inter-protein interactions originally present in casein micelles in milk were substituted by electrostatic, hydrogen, and calcium bonds throughout the curd curing period. Disulfide bonds were not disturbed by the experimental conditions employed in the study, remaining at a constant level in all studied treatments. Acidification of curds increased the availability of soluble ionic calcium, increasing the relative proportion of calcium bridges at the expense of electrostatic-hydrogen bonds. Although pH defined the nature of the interactions established among proteins in curd, temperature modified the rate at which such bonds were formed.

This research work is carried out to find the self-healing time and mechanical properties of concrete by using Bacillus Subtilis and Escherichia Coli. These bacterias has the capability of healing the cracks by itself. M20 concrete designed as per IS 10262–2009 is taken as reference sample. Different mixes were casted varying the percentage of bacteria. The above-mentioned bacteria were mixed in percentages of 2%, 3%, 4% and 6% by weight of cement separately and combination of both bacteria at 50% each to make total 2% and 3% of mixed bacteria by weight of cement. Calcium Lactate (a calcium-based nutrient for the bacteria) is mixed at a constant 5% for all mix variations. All the mixing, casting, curing and testing is done as per standard practice. Slump cone test gave an increased workability of 45% with bacteria Bacillus Subtilis. Standard size cubes of 150 mm were casted (nine for each mix), cured and tested at the age of 7, 14, 28 days. Some samples were tested in Compression testing machine till cracks were evident and measurable. The bacteria gets activated when water comes in contact with it, starts to feed on calcium lactate and grow resulting in self-healing of cracks in concrete. It is observed that the cracks were healed within 48 hrs for 2% Bacillus Subtilis, 32 hrs for 3% Bacillus Subtilis, and 72 hrs for 4% Bacillus Subtilis, even after 72 hrs no evident healing was observed for 6% Bacillus Subtilis all percentages of Escherichia Coli and mix bacteria. Hence the optimum dosage for self-healing of concrete is 3% Bacillus Subtilis. Both Compressive strength and Split Tensile strength, tests are done as per IS 516-2002 (reaffirmed 2018) and results gave an increase of 60%, strength for samples with 3% Escherichia Coli bacteria.

Innovative approaches are under research to study the resistance of chloride ion penetration in concrete containing chloride ions, to minimize the impact of chloride ion penetration test errors in coastal reinforced concrete (RC), which is helpful to the design of coastal RC structures. In this study, the diffusion depth, free ion concentration and diffusion coefficient of chloride, iodide ions with different curing ages and GGBFS content were measured by the Rapid Chloride Migration Test (RCM) and Rapid Iodide Migration tests (RIM). The SEM-EDS and MIP were used to analyze the microstructures, pore size distribution and the hydrated products. The results show that the performance of GGBFS concrete against the diffusion of corrosive ions is affected by the curing age and the content of GGBFS. With the increase of GGBFS content, especially concrete with 60% GGBFS, the influence of chloride, iodide ion penetrating into concrete gradually becomes smaller. The long-age curing system is more conducive to the concrete resistance to the migration and diffusion of chloride, iodine ions. Compared with the ordinary concrete, the total porosity of concrete mixed with GGBFS is lower, the internal microstructures have fewer cracks and defects, the density is better, and the diffusion coefficient of chloride and iodide ions is also lower. In addition, using the concept of corrosive ion adjustment coefficient (conversion coefficient of diffusion between chloride ion and iodide ion) and applying the data regression analysis (DRA), it is found that there is a good quadratic parabolic function relationship between the GGBFS content and the ions adjustment coefficient.

In this study, the Geopolymer mortar had been examined under flowability and compressive strength using metakaolin. The binder content of 50% fly ash and 30% Ground Granulated Blast Furnace Slag (GGBFS) has been kept constant. The remaining 20% of binder is partially replaced by metakaolin to fly ash such as 5%, 10% 15% and 20%. The sodium silicate (Na2SiO3) solution molarity has been varied from 1.5 M to 2 M. The test results indicate that, the fine particles of metakaolin (up to 15%) improves the flowability and also act as a filler material and another hand, increase in molarity of the solution leads to decrease in flowability but increase in compressive strength had observed. The compressive strength of the Geopolymer mortar had been increased with increase in metakaolin content. The optimum proportion of 15% metakaolin with 1.5 M Na2SiO3 solution is suggested in terms of workability and compressive strength of Geopolymer mortar under ambient curing.

Recently, the capture of carbon dioxide (CO2) using alkaline waste and byproducts has garnered considerable interest. Construction sludge may be categorized as alkaline waste, as it often exhibits high alkalinity during its generation or intermediate treatment. Hence, researchers have attempted to accelerate pH neutralization and recycle alkaline construction sludge by curing it under a high CO2 concentration. By exposing concentrated CO2 gas to an alkaline sludge, cement hydrates such as calcium hydroxide and calcium–silicate–hydrate gels form calcium carbonate (CaCO3). Subsequently, the generation of CaCO3 is expected to reduce the pH of the sludge. However, the amount of CO2 captured in sludge has not been investigated extensively, unlike those of other alkaline wastes. Therefore, the amount of CO2 captured in alkaline sludge that is associated with pH neutralization is evaluated in this study. It is demonstrated that accelerated carbonation tests using a CO2 incubator and carbonate content evaluation tests based on the gas pressure method successfully reveal the amount of CO2 captured in the alkaline sludge that is associated with pH neutralization. Additionally, the test results show that the amount of mCO2 (i.e., the amount of CO2 captured per 1 g of dry mass of alkaline sludge) increases with ΔpH (ΔpH is the difference between the initial pH and the pH after the alkaline sludge is neutralized). A maximum of 0.021 g of CO2 is captured per 1 g of dry mass of alkaline sludge when the addition ratio of quicklime AQL = 3% and 0.040 g when AQL = 6%. The CO2 capture ratio mCO2/mCO2max, which represents the ratio of CO2 captured in the sludge to the maximum capturing capacity, increases with ΔpH. CO2 capture ratios of up to 90.0% and 84.9% are recorded when AQL = 3% and AQL = 6%, respectively. It is discovered that a higher AQL results in a higher mCO2. Moreover, the test results indicate that a higher AQL causes a more significant change in the CO2 capture ratio, even when the pH decreases slightly.

Ureolytic bacteria strains of Bacillus show its ability of calcium carbonate precipitation through metabolic activity. Different studies related to self-healing concrete material were reported associated with the generated calcium carbonate of Bacillus subtilis HU58 metabolism in recent communications. In this paper, recent findings of soil cementing with a combination of such precipitated products were presented. The experiments relied on the lab-scale studies with the use of sand-clay mixture as the controlled soil specimens. Bacillus bacteria and nutrients were mixed to introduce in the sand matrix and then curing in high moisture condition. The composition and morphology of soil specimens were characterized after solidifying by FTIR, XRD, and SEM. Water percolation and mechanical stability for the physicomechanical properties were also tested with the unconventional method. Discussing the relevant results can help to figure out the next experiments in the field of geotechnical engineering. From the perspective of this study, the sustainability factor should be considered to apply this promising technique for soil stabilization and improvement and/or for the formulation of bio-brick as an alternative to sintered clay-based brick. From the perspective of this study, this technique for soil stabilization and improvement and/or for the formulation of bio-brick can be considered a promising sustainable alternative to sintered clay-based brick.

Fly ash-based geopolymer is a crucial application for tackling climate change, limiting the production of greenhouse emissions. The main aim of this study was to determine the effect of the fundamental parameters on compressive strength to ensure a feasible and effective solidification of mine tailings. Three sodium hydroxide (NaOH) molarities (5, 8, and 10 M) and sodium silicate (Na2SiO3) were combined to form the alkaline solution. Four fly ash (FA) proportions (28%, 44%, 54, and 61%) of the dry mix and mine tailings (MT) were utilized as raw materials. This study demonstrated that both 25 °C and 65 °C have a considerable effect on the mechanical properties of geopolymers. The UCS value increased with an increase in NaOH molarity. In addition, the highest Unconfined Compressive Strength (UCS) value was achieved (36.04 MPa) at 10 M. Furthermore, the results also showed that UCS values kept decreasing with the increase of SiO2/Al2O3 and Na2O/SiO2 ratios. The optimal UCS values found were in the range of 0.28–0.38 liquid/solid ratio. It has been concluded that the previously mentioned parameters have a strong influence on the mechanical strength of fly ash-based geopolymer with the new proposed FA proportion.

Limestone calcined clay cement (LC3) is a new type of low-carbon cement that can reduce energy consumption and carbon dioxide emissions while meeting the performance requirements of ordinary cement. In this study, polypropylene (PP) fibers were mixed into limestone calcined clay cement-based materials to make new low-carbon ECCs. In this study, a total of 24 sets of specimens were designed for 4 groups of curing ages and 6 types of mix ratios. The compressive load–displacement data were measured the compressive curve characteristics were analyzed then, a compressive constitutive model of the composites was deduced and obtained. Through XRD, SEM-EDS and MIP experiments, the reasons and laws of the compressive strength ranges of adding PP fibers and LC3 to engineered cementitious composites (LC3-PP-ECCs) are further explained from the perspective of the pore size, microstructures and hydration products. The results show that, after 28 days, the compressive strength values of LC3-PP-ECCs generally decreases with increasing PP fiber content and the combined effect of PP fibers and hydration products causes the compressive strength of LC3-ECCs with 0.5% PP fibers to drop sharply. In addition, the specimens showed better properties in terms of toughness, ductility and energy absorption. However, in the microstructures, the addition of PP fibers will cause more internal defects and flaws. This results of this study can provide some theoretical experience and technical support for the engineering application of LC3-ECCs.

In this paper, copper foams cured MIL-101(CFCM)/isobutane double-bed adsorption cooling system (ACS) were designed and constructed by using the CFCM unit tube adsorbers. Adsorption cooling characteristic curves of CFCM/isobutane double-bed ACS were studied. Influence of cycle parameters and mass recovery process on the cooling capacity, specific cooling power (SCP) and coefficient of performance (COP) of the CFCM/isobutane double-bed ACS was investigated. Results show that under the conditions of cycle time of 600 s, pre-cooling/pre-heating time of 120 s, condensation temperature of 15°C and hot water temperature of 85°C with the flow rate of 20 L h−1, and cooling water temperature of 14-16°C with the flow rate of 50 L h−1, the cooling capacity, SCP and COP of CFCM/isobutane double-bed ACS is 65.20 kJ kg−1, 108.67 W kg−1 and 0.2260, respectively. Compared with basic cycle, the cooling capacity, SCP and COP of CFCM/isobutane double-bed ACS increases by about 26%, 24% and 22% under mass recovery time of 10 s. The cooling performance of CFCM/isobutane double-bed ACS remains stable after 100 sets consecutive basic cycles and 20 sets mass recovery cycles.

Mine tailings-based geopolymer was proved to be successfully created with enhanced strength for potentially construction and building materials applications. Through geopolymerization, the mining wastes can be reused and the storage, economic, and environmental issues can be mitigated. However, the geopolymerization effect was relatively limited comparing to the ordinary Portland concrete. Therefore, the additions of amorphous supplementary fly ash were considered in the paper. In this study, class F fly ash was utilized as an amorphous additive and the additional aluminum source to adjust the Si: Al ratio for better geopolymerization effects. To better understand the mechanical and fracture behavior of the geopolymer after adding fly ash, the Brazilian indirect tensile tests were then conducted to evaluate the influence of different fly ash additions, 5%, 10%, 15%, and 20%, on the tensile strength of the geopolymer. Meanwhile, besides the load-displacement relationships, the digital image correlation was used to investigate the crack initiation and propagation in the geopolymer disks with respect to different fly ash additions. The crack evolution was evaluated from the full-field strain field from digital image correlation. Crack opening displacements, failure patterns, and strain evolutions for the geopolymer disks with different fly ash additions were examined. Results showed that, under the presented sample curing condition, the geopolymer with 15% fly ash addition had the largest tensile strength. Geopolymer disks without and with lower fly ash additions had plastic deformation prior to the peak load that can obviously be classified into three different stages. The geopolymer made without and with lower fly ash additions had both tensile and shear crack modes.

The paper discusses various ways of activating phosphorus slags by introducing additives for the development of phosphorus slag binders (PSB), replacing cement. Considering that pseudowollastonite is the main mineral of phosphorus slags and without activating components does not possess the binding properties necessary for the production of building materials based on them, we used compositions of small amounts of sodium hydroxide with alkali metal salts, the anions of which form poorly soluble compounds with calcium. When choosing activating components, scarce alkaline additives were replaced by waste from chemical plants, which allows a passing solution of their practical use and environmental problems. The strength at a sodium hydroxide content of 1–4 % after curing of slag samples of various batches was in the range of 50.0–70.0 MPa. Samples of binders of normal hardening at the age of 28 days with a sodium hydroxide content of 0.5; 1.0, 2 and 4 % had the strength of 20.3; 35.4; 45.6; 55.8 MPa, respectively. The effect of the combined presence of alkali and salt is especially noticeable for small amounts of sodium hydroxide. Binders containing a composition of cement with salts under normal conditions and after curing showed a slightly lower strength than in an alkaline medium. With a constant cement content (4 %), the strength indicators increase with an increase in the proportion of the salt additive, reaching at 4 % its maximum value. The effect of the nature of activators on pH was determined. The data obtained indicate the advantages of using PSB and various industrial wastes with a low content of alkaline compounds in the production, В работе рассматриваются различные способы активации фосфорных шлаков путем введения добавок для разработки фосфорношлаковых вяжущих (ФШВ), заменяющих цемент. Учитывая, что псевдоволластонит является основным минералом фосфорных шлаков и без активирующих компонентов не обладает связующими свойствами, необходимыми для производства строительных материалов на их основе, мы использовали композиции из небольших количеств гидроксида натрия с солями щелочных металлов, анионы которых образуют плохо растворимые соединения с кальцием. При выборе активирующих компонентов ограниченные щелочные добавки были заменены отходами химических производств, что позволяет попутно решить проблемы их практического использования и защиты окружающей среды. Прочность при содержании гидроксида натрия 1–4 % после тепловлажностной обработки образцов шлака различных партий находилась в пределах 50,0–70,0 МПа. Образцы вяжущих нормального твердения в возрасте 28 суток с содержанием гидроксида натрия 0,5; 1,0, 2 и 4 % имели прочность 20,3; 35,4; 45,6; 55,8 МПа соответственно. Эффект совместного присутствия щелочи и соли особенно заметен для небольших количеств гидроксида натрия. Вяжущие, содержащие композицию цемента с солями, в нормальных условиях и после ТВО показали несколько меньшую прочность, чем в щелочной среде. При постоянном содержании цемента (4 %) показатели прочности увеличиваются с увеличением доли солевой добавки, достигая при 4 % своего максимального значения. Было определено влияние природы активаторов на рН. Полученные данные свидетельствуют о преимуществах использования ФШВ и различных промышленных отходов с низким содержанием щелочных соединений в производстве., У роботі розглядаються різні способи активації фосфорних шлаків шляхом введення добавок для розробки фосфорношлакових в'яжучих (ФШВ), що замінюють цемент. Враховуючи, що псевдоволластоніт є основним мінералом фосфорних шлаків і без активуючих компонентів не володіє в'яжучими властивостями, необхідними для виробництва будівельних матеріалів на їх основі, ми використовували композиції з невеликих кількостей гідроксиду натрію з солями лужних металів, аніони яких утворюють важкорозчинні сполуки з кальцієм. Під час вибору активуючих компонентів обмежені лужні добавки були замінені відходами хімічних виробництв, що дозволяє попутно вирішити проблеми їхнього практичного використання і захисту навколишнього середовища. Міцність при вмісті гідроксиду натрію 1–4 % після тепловологісної обробки зразків шлаку різних партій перебувала в межах 50,0–70,0 МПа. Зразки в'яжучих нормального твердіння у віці 28 діб з вмістом гідроксиду натрію 0,5; 1,0, 2 і 4 % мали міцність 20,3; 35,4; 45,6; 55,8 МПа відповідно. Ефект спільної присутності лугу і солі особливо помітний для невеликих кількостей гідроксиду натрію. В'яжучі, що містять композицію цементу з солями, в нормальних умовах і після ТВО показали дещо меншу міцність, ніж в лужному середовищі. При постійному вмісті цементу (4 %) показники міцності збільшуються зі збільшенням частки сольової добавки, досягаючи при 4 % свого максимального значення. Було визначено вплив природи активаторів на рН. Отримані дані свідчать про переваги використання ФШВ і різних промислових відходів з низьким вмістом лужних сполук у виробництві.

The effect of graphene oxide (GO) nanosheets on the spatial distribution of cement paste pores has been investigated. In this study, a scheme based on the radial distribution function is developed to analyze the spatial distribution of pores in GO-cement composites. By applying the developed scheme, the addition of 0.04% GO is found to reduce the spatial inhomogeneity of pores in cement paste by around 20% at all curing ages. The test results show that the compressive strength of the cement paste sample containing GO is increased by 30-40%, indicating the negative correlation between the spatial inhomogeneity of pores and mechanical properties of GO-cement composites. Besides the spatial homogenization effect of GO on pores, pore structure refinement by GO is also found to increase the mechanical properties of cementitious materials. The findings suggest the great potential of using GO to modify cementitious materials by homogenizing the spatial distribution of pores. The spatial distribution analysis scheme presented in this study can be used for the future structure-property study of nanoengineered cementitious materials with enhanced performance.

Glass fibre reinforced cement (GFRC) is a composite material with great ductility but it undergoes severe strength and ductility degradation with ageing. Calcium sulfoaluminate (CSA) cement is low carbon cement, and more importantly, it exhibits great potential to produce more ductile and durable GFRC. This study focuses on mechanical performance, e.g., compressive strength, stress-strain curve, and freeze-thaw resistance of CSA/GFRC as well as its microstructural characteristics under low temperatures. XRD was applied to investigate the hydration mechanism of CSA cement under −5°C, 0°C, and 5°C. It was found out that low-temperature environments have very little effect on the type of hydration products, and the main hydration product of hydrated CSA cement cured under low temperatures is ettringite. Moreover, low-curing temperatures have an adverse effect on the compressive strength developments of CSA/GFRC but the strength difference compared with that under 20°C reduces gradually with increasing curing ages. In terms of bending performance, both ultimate tensile strength and ultimate strain value indicate considerable degradation with ageing under low temperatures after 14 d. The ultimate strain value reduces to 0.34% at −5°C, 0.39% at 0°C, and 0.44% at 5°C compared with 0.51% for that cured at 20°C for 28 d. The tensile strength of samples cured at −5°C for 28 d is only 15.2 MPa, taking up only 40% of that under 20°C. CSA/GFRC also demonstrated great capability in the antifreeze-thaw performance, and the corresponding strength remains 95.9%, 94.7%, 94.2%, and 94.3%, respectively, for that cured under 20°C, 5°C, 0°C, and −5°C after 50 freeze-thaw cycles. Microstructural studies reveal that densification of the interfilamentary space with intermixtures of C-A-S-H and ettringite is the main reason that causes the degradation of CSA/GFRC, which may result in loss on flexibility when forces are applied, therefore reducing the post-peak toughness to some extent.

It has been established that during heat treatment of mixtures of waste activated sludge (WAS) and Fe2O3 under the conditions of oxygen deficiency at 800–1000 °C, reactive carbon, which initiates the reduction of Fe2O3 to Fe and the formation of C–FexOy mixtures, forms. Based on these compacted mixtures, having different electrical resistivity (from ~ 10–4 up to 10–1 Ω·m), it is possible to fabricate heating elements, whose working temperature ranges from ~ 100 °C up to 600 °C. Such heating elements can be used in the construction industry to accelerate the curing of concrete and its low temperature heating.

In this study, the potential usage of wastewater bottle strips produced from polyethylene terephthalate (PET) as a reinforcing material for strength properties of cement stabilized clay was investigated. For this purpose; unconfined compression strength tests were conducted to determine the parameters affecting the strength properties of cement stabilized-reinforced clay. Four different ratios of cement (0, 3, 6, and 9%) were used for clay stabilization and waste bottle strips obtained by cutting from waste pet bottles were used for reinforcement. Considering that the waste bottle strips behave similar to the fiber material; cement stabilized-reinforced clay samples were prepared with the ratios of 0, 0.5, 1.0, 1.5, and 2.0%, which are generally used as reinforcement ratios for soil. The specimens were stored in the curing room for 1, 7, 28, and 90 days until testing. Test results were evaluated according to cement content, water bottle strip ratio and curing time parameters. The experimental results showed that the optimum water bottle strip ratio for maximum strength gain ranged from 1 to 1.5%. It was also observed that the plastic strips and cement used for soil improvement also changed the strength-deformation behavior of the kaolin clay. Besides, the augmentation in cement inclusion level and curing period increased the strength of kaolin clay. (C) 2021 Karabuk University. Publishing services by Elsevier B.V.

Corrosion of steel in reinforced concrete causes severe damage in durability as weakness support of reinforced elements. We investigate impacts of cement fraction and curing method on corrosion progression. Corrosion level is evaluated by measuring carbonation penetration and electrical conductivity in concrete plots as indicators of corrosion. Two types of cement were used, Normal and quick setting. For each cement type, two concrete mixes were used (3% and 8% C3A are designed). Six levels of CaCl2 ranging from 0.5 % to 3% were used to simulate corrosion. Also, two curing methods are compared, liquid water and steam application are used. Chloride ion in low alumina cement mortar progressed faster than high alumina. The results show significant increase in carbonation depth for (less cement) compared to (more cement) mixes. Also, steam curing showed less penetration than normal water setting method. Variation in carbonation penetration for 0.5 and 1 % CaCl2 is high close to double. Electrical potential of steel in cement mortar is negatively related with increasing calcium chloride content and with increasing cement content. Also, normal setting cement shows better corrosion protection as demonstrated by higher measured EC.

This study explores the coupling effect of pond ash (PA) and polypropylene (PP) fiber to control the strength and durability of expansive soil. The PA is used to chemically treat the expansive soil and PP fiber is adopted as reinforcement against tensile cracking. The sustainable use of PA and PP fiber are demonstrated by performing mechanical (i.e. unconfined compressive strength, split tensile strength and ultrasonic pulse velocity), chemical (pH value, electrical conductivity and calcite content), and microstructural analyses before and after 2nd, 4th, 6th, 8th and 10th freezing-thawing (F-T) cycles. Three curing methods with 7 d, 14 d and 28 d curing periods are considered to reinforce the 5%, 10%, 15% and 20% PA-stabilized expansive soil with 0.25%, 0.5% and 1% PP fiber. In order to develop predictive models for mechanical and durability parameters, the experimental data are processed utilizing artificial neural network (ANN), in association with the leave-one-out cross-validation (LOOCV) as a resampling method and three different activation functions. The mechanical and durability properties of the PA-stabilized expansive soil subgrades are increased with PP fiber reinforcement. The results of ANN modeling predict the mechanical properties perfectly, and the correlation coefficient (R) approaches up to 0.96.

This study aims to assess the long-term efficiency of silica fume used in the production of concrete exposed to sulfate solutions and seawater. The sulfate solutions used in the study were sodium sulfate and magnesium sulfate, and the seawater was provided from Black sea. The experimentation has continued for 4 years. The sulfate ion concentration of the sodium and magnesium sulfate solutions was adjusted to be 1300 ppm, which would be equivalent to the sulfate ion concentration of the seawater used in the test program. The total binder was 350 kg/m3, and cement was replaced by silica fume at a ratio of 10%. The concrete prisms produced were 40 × 40 × 160 mm standard prisms. In order to evaluate the efficiency of silica fume preventing sulfate attack, mass variation along with strength change has been taken into consideration as well as observational evaluation implemented throughout the experimentation. Concrete prisms cured under standard curing conditions were also produced for comparison purposes. Considering the compressive strength, seawater seemed particularly detrimental for concrete that does not contain silica fume. Hence, regarding the compressive strength change of concrete, it is realized that it is worth to take particularly into account the seawater effect in addition to the effect of sulfate solutions. The strength deterioration process of concrete prisms immersed in sodium and magnesium sulfate solutions seemed to be associated with the loss of stiffness and cohesiveness rather than expansion and cracking as opposed to the deterioration observed in case of seawater immersion. Visible cracks were formed in the prisms that did not contain silica fume immersed in seawater.

This study examines the effect of partially replacing cement with blue gumwood ash (BGWA) in stabilizing laterite soil to be used as a potential road base material. Initially, Ordinary Portland Cement was introduced to the soil at varying contents from 0 to 12% in steps of 3% by weight of the soil sample. Each wet sample of the soil was subjected to the Californian bearing ratio (CBR) and unconfined compressive strength (UCS) tests in determining the optimal soil-cement mix. Results show that CBR and UCS values increased as cement content increased, and a 6% cement content corresponding to a UCS value of 2.88 MPa at 7 days of curing met the specifications of the Overseas Road Note 31 to be used in the construction of road bases. The second treatment involved partially replacing the 6% cement content with BGWA in decreasing steps of 1%. Peak CBR value of 348% at 2% BGWA content (>160% recommended by Kenya road design manual) and UCS value of 2.99 MPa at 7 days of curing were obtained. Thus, BGWA can partially replace cement in stabilizing laterite soil for use in the construction of road bases as per the Overseas Road Note 31 specifications., 8 pages, 10 Figures, Published with International Journal of Engineering Trends and Technology (IJETT)

The effects of Na-montmorillonite (Na-Mt) content and curing age on enzyme-induced carbonate precipitation (EICP)-treated soil were studied. First, the effects of Na-Mt addition on the urease activity, Ca2+ precipitation rate, and pH of the solution were analyzed through tube tests. Then, Na-Mt-modified EICP was used to reinforce silty sand in the Yellow River flooding area in China. The solidification effect and action mechanism of Na-Mt were investigated via the unconfined compressive strength (UCS) test, calcium carbonate content (CCC) measurement, X-ray diffraction, and scanning electron microscope analyses, wherein soil treated by conventional EICP and soil treated with Na-Mt alone were considered the control group. Na-Mt improved the urease activity and Ca2+ precipitation rate, lowered the pH, increased the CaCO3 production through chelation, then regulated the morphology of the CaCO3 crystals and facilitated the formation of densely aggregated calcite. The CCC and mechanical parameters increased rapidly during the first 7 days of curing, and then slowed down. The incorporation of 8% Na-Mt enhanced the UCS and Ca2+ utilization ratio at curing age of 7 days by 1.4 and 2.72 times, respectively, compared with that of traditional EICP; and the optimal Na-Mt content was identified to be 8%. At Na-Mt contents lower than 8%, the mathematically expressed improvement effect of the Na-Mt-modified EICP on the soil strength was greater than the arithmetic sum of that when these two approaches applied individually; this result confirms that the Na-Mt-modified EICP technique proposed herein is an efficient approach for solidifying fine-grained soil.

Acid mine drainage presents an important threat to cementitious structures. This study is aimed at investigating the effect of cellulose nanocrystals (CNCs) on the acid resistance of cementitious composites. CNCs were added to mortar mixtures as additives at cement volume ratios of 0.2vol%, 0.4vol%, 1.0vol%, and 1.5vol%. After 28 d of standard curing, the samples were immersed in a sulfuric acid with a pH value of 2 for 75 d. The unconfined compressive strength (UCS) test, the density, water absorption, void volume test, and thermogravimetric analysis were carried out to investigate the properties of CNC mixtures before sulfuric acid immersion. It was found that the addition of CNC reduced the volume of permeable voids and increased the hydration degree and mechanical strength of the samples. Changes in mass and length were monitored during immersion to evaluate the acid resistance of mixtures. The mixture with 0.4vol% CNC showed a reduced mass change and length change indicating its improved acid resistance.

The objective of the investigation was to develop turmeric powder with improved quality using an instant decompression-assisted steam curing (IDASC) process. The IDASC treatment was administered on peeled turmeric slices in the ICPD treatment chamber, which was further followed by hot air drying of the treated slices (IDASC-HAD). The process conditions, namely, treatment pressure (TP), treatment time (TT) and temperature of drying (TD) were optimized for the minimization of hot air drying time (DT) and maximization of the yellowness value (YV) and curcumin content (CC) of the turmeric powder, by the application of an approach which combines the benefits of particle swarm optimization (PSO) with the response surface methodology (RSM). Micro-structure of the IDASC-HAD-treated turmeric slices were observed based on scanning electron microscopy (SEM) image. Turmeric powder obtained by the IDASC-HAD approach was compared with the conventional product for various functional properties. The best quality turmeric powder with DT of 325 min and YV and CC of 60 and 5.05%, respectively, was obtained under the optimum process conditions of the IDASC-HAD process, namely, TP of 3 atm, TT of 50 s and TD of 57 °C. The IDASC-HAD-based turmeric powder samples exhibited higher values of 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH), total phenolic content (TPC) and total flavonoid content (TFC) as compared to the conventionally produced ones. The improvements in the particle size and micro-structural characteristics were justified from the results of SEM. Turmeric powder produced by the IDASC-HAD method as applied to turmeric slices can be asserted as a product with improved antioxidant properties, which may have application in development of beverages with potential health benefits.

A study of magnesia refractories containing glucose, citric acid, and metallic Al and their influences on structure, mechanical strength, and thermal shock resistance, is presented. Combined with thermodynamic calculation, microstructure, and properties analysis, the results show that formation of gluconates and citrates from the introduced glucose and citric acid enhanced the bonding of raw materials and the curing strength of samples. The pyrolysis of gluconates and citrates, and the oxidation and nitridation of metallic Al had significant effects on the microstructural evolution of magnesia refractories after high temperature treatments, mainly AlN and MgAl2O4 whiskers in pores and particle gaps. The formation and development of whiskers give rise to samples improved toughness and thermal shock resistance. Increasing the metallic Al content from 0 wt% to 2 wt% enhanced the fracture surface energy of samples heat treated at 1400 °C from 82.22 kJ/m2 to 119.75 kJ/m2. Meanwhile, after three thermal-shock cycles, the residual strength ratios of heat treated samples were elevated from 52.8% to 67.9%. On the basis of influences of phase transformation on the structure and properties of samples at different temperatures, considering the structural compactness and ability to withstand external stress for magnesia refractories used in metallurgical field, it is suggested that when glucose and citric acid are used as binders, the addition of metallic Al should be less than 3 wt%.

Calcium-strontium aluminate cement (CSAC) has been successfully prepared for the first time from celestite mineral and corundum (α-Al2O3) via solid-state reaction. Various mixing compositions containing 40–70 wt% celestite and 60–30 wt% alumina have been sintered at firing temperatures between 1550 and 1650 °C with an interval of 50 °C. Among these sintered mixes, four cement specimens (CA101-1600, CA101-1650, CA201-1600 and CA201-1650) were selected as the optimal mixes for CSAC preparation based on their physico-chemical and mechanical characteristics. These cement mixes were ground to form a very fine powder with a particle size of less than 4.85 μm and a specific surface area of greater than 3629 cm2/g. Upon mixing these cement mixes with water, they consumed mixing water within a range of 19–27 wt% to form workable cementitious pastes. The initial and final setting times of these four cement mixes were in the range between 80 to 90 min and 290–379 min, respectively. An average compressive strength of approximately ~62 MPa was reached after curing of these cement cubes in a 100% humidity cabinet for 28 days. The main hydration products detected in the cement pastes were strontium aluminate hydrates such as 3SrO·Al2O3·H2O (Sr3A.H2O) and 5SrO·Al2O3·11H2O (Sr5A.11H2O) along with a minority of calcium aluminate hydrate 4CaO·3H2O·3H2O (C4A3.3H2O) and aluminium hydroxide Al(OH)3. The obtained physico-mechanical results of the four cement samples have met the international standard requirements; demonstrating the high-susceptibility of celestite mineral to be utilized as a potential feedstock in the production of CSAC on an industrial scale.

The impact of green tea extract powder and rosemary extract powder, alone or in combination, on the quality characteristics of naturally cured pork sausages produced with white kimchi powder as a nitrate source was evaluated. Ground pork sausages were assigned to one of seven treatments: control (0.01% sodium nitrite and 0.05% sodium ascorbate), treatment 1 (0.3% white kimchi powder and 0.05% green tea extract powder), treatment 2 (0.3% white kimchi powder and 0.1% green tea extract powder), treatment 3 (0.3% white kimchi powder and 0.05% rosemary extract powder), treatment 4 (0.3% white kimchi powder and 0.1% rosemary extract powder), treatment 5 (0.3% white kimchi powder, 0.05% green tea extract powder, and 0.05% rosemary extract powder), and treatment 6 (0.3% celery juice powder, 0.05% green tea extract powder, and 0.05% rosemary extract powder). Naturally cured products had lower (p

Geopolymer is an environment-friendly cementitious material, which can effectively immobilize heavy metals. However, the existing study on solidification/stabilization (S/S) of heavy metal contaminated soil using geopolymer is very limited. In order to investigate the effects of geopolymer produced by activating fly ash (FA) and ground granulated blast-furnace slag (GGBS) (FA + GGBS) with composite activator of Na2SiO3 and NaOH on environmental and engineering properties of Pb2+ and Cd2+ contaminated soil, a series of tests including soil pH, leachate pH and electrical conductivity (EC), toxicity leaching, UCS and pH-dependent tests were conducted at different curing times. Additionally, scanning electron microscopy/energy dispersive spectroscope (SEM/EDS), X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) tests were performed to analyze the micro mechanism of FA + GGBS based geopolymer solidified contaminated soil. The results indicated that the UCS and pH of soil increased steadily with FA + GGBS content and curing time increasing. Moreover, as FA + GGBS content and curing time increased, the leached Pb2+, Cd2+ concentration decreased significantly, and the concentration was closely related to the pH of leachate. Compared with Cd2+, the solidification ratio of FA + GGBS based geopolymer for Pb2+ was lower. Besides, the leached Pb2+ and Cd2+ concentrations decreased first and then increased with increasing pH of extraction fluid. Microscopic analysis showed that the gel products of FA + GGBS based geopolymer were mainly C-(N)-A-S–H gels. However, the geopolymer structure became looser due to the existence of Pb2+ or Cd2+. The formation of Cd(OH)2 was the primary solidification mechanism of Cd2+, while Pb2+ was mainly immobilized in geopolymer structure by ion exchange. The MIP results showed that the volume of inter-aggregate pores between 0.01 and 1 μm reduced with increasing FA + GGBS content of solidified soil.

Sodium chloride (NaCl) is commonly used as a curing/preservative agent for raw hides and skins in tanneries and is removed through a soaking process with total dissolved solids (TDS) and other organic pollutants in effluent, causing significant pollution load to the environment. Hence, the present study evaluated to apply dried neem leaf powder (DNL) as an additive to reduce the usage of salt in skin processing and preservation. To make certain of DNL antimicrobial properties, solvent extracts were performed against proteolytic bacteria isolated from raw skins. Initial characterization of DNL revealed the presence of bioactive compounds nimbolide and dehydro salannol and acetone extract with 16.9-mm, 10-mm and 8-mm zone of inhibition against Salmonella sp., E. coli sp. and Bacillus sp. identified using phenotypic conventional biochemical screening method. Further, skin curing experiments were carried out using four different treatments of DNL (10% 15%, 20% and 25% w/w) along with 15% w/w of conventional salt to obtain an optimum concentration for pilot-scale studies. Thus, the application of optimal DNL (15%) and salt (15%) resulted in no physical changes such as smell and hair slip and was taken for further studies for hydroxyproline activity, pollution load and organoleptic properties along compared with control 40% salt. DNL-aided salt less preservation of freshly flayed goat skins at ambient condition showed no hair slip or putrefaction during the preservation period with significant reduction of TDS (86%) and chloride (71%) in soak liquors compared to conventional salt preservation and enhanced organic load requiring additional treatment. However, the application of the organoleptic, physical and hydrothermal properties of resulting leathers produced from the DNL applied skins was on par with results of leather obtained from conventional salt. Thus, our results demonstrate DNL-aided salt less preservation method is able to reduce the amount of salt for preservation of goat skins significantly, leading to reduced salinity issues during leather processing.

The performance of cellulose fiber-reinforced cement-based composites (CFCCs) depends not only on the characteristics of the cement matrix and fibers but also on the bonding property of the matrix and fibers. The durability of cement-based composites including various properties such as impermeability, frost resistance, and carbonization resistance has an important impact on the long-term service life of the matrix structure. The presence of a large number of hydroxyl groups on the molecular chain of cellulose can promote the formation of intra- and intermolecular hydrogen bonds of cellulose. This special structure imparts the cellulose high hydrophilicity, which leads the cement hydration C-S-H gel to adhere to the surface of cellulosic fibers (CFs) and induce its growth. The cavity of CFs has good water absorption and can be used as an internal curing fiber for the continuous hydration of cement-based composites. But CFs in the Portland cement matrix tend to deteriorate under strong alkali conditions. This paper presents a review of the research on the durability of CFCCs. The methods and paths to improve the durability of CFCCs are summarized and analyzed from the perspectives of the internal curing of CFs, the deterioration of the performance of CFs in the matrix, and the use of many types of supplementary cementitious materials. Finally, the development and engineering application of CFCCs have been prospected.

The search for new materials to replace Portland cement (PC) has increased due to the high release of carbon dioxide (CO2) and the exploration of raw materials for its production. In this case, supersulfated cement (SSC) appears as an option. SSC consists of up to 90% blast furnace slag and small percentages of calcium sulfate and alkaline activator. This cement has some characteristics similar to PC with the advantage of using less raw material. However, some studies have identified the instability of the ettringite formed in the hydration of SSC although this phenomenon has not been studied in detail in previous research. Therefore, this study aimed to evaluate the behavior of different supersulfated cement compositions, comparing the hydration processes, and identifying the influence of their chemical composition on the instability of ettringite. Microstructural analyses of XRD, TGA, and SEM showed instability of the phases formed from all SSC compositions at 49 days of curing. Mechanical strength and calorimetry analyses showed the best behavior using gypsum as a source of calcium sulfate. Also, the SSC with the highest calcium sulfate content showed lower instability of ettringite and greater compressive strength.

This study seeks to investigate the time and the temperature of the formation of the composites faujasite-geopolymer gels in the reaction medium, and also study the compressive strengths and the microstructural properties of the hardened composites after curing at room temperature. Sodium waterglass from rice husk ash, incandescent and fluorescent bulbs known as low-value silica-rich wastes were used as hardeners for the preparation of the composites at room temperature. The X-ray patterns of the composites using sodium waterglass from incandescent and fluorescent bulbs indicate the reflection peaks of faujasite-Na and the broad hump structure belonging to the geopolymer networks. Whereas the one using sodium waterglass from rice husk ash shows only the broad hump structure. The semi-adiabatic results show that geopolymer gels are formed after 18 min at the temperature of the reaction medium of 38 °C in the composites when sodium waterglass from rice husk ash was used as a hardener. Whereas they are formed after 10 min at the temperature of the reaction medium of 34 and 43 °C in the composites using sodium waterglass from incandescent and fluorescent bulbs, respectively. Zeolite type faujasite-Na is formed after 72 and 40 min at the temperature of the system at 76 and 90 °C in the composites using sodium waterglass from incandescent and fluorescent bulbs, respectively. The increase in the temperature of the reaction medium leads to the crystallization of faujasite. The compressive strengths of the hardened composites using sodium waterglass from rice husk ash is higher (47.54 MPa) compared to those from the incandescent bulb (22.42 MPa) and the fluorescent bulb (12.53 MPa). It was found that faujasite-geopolymer composites could be obtained at non-hydrothermal condition using sodium waterglass from incandescent and fluorescent bulbs. It appears that the formation of faujasite in the structure of geopolymer cements decreases the compressive strength of the composites.

For the resource utilization of the solid waste coking sulfur paste and the improvement of performance of the asphalt mixture, a method for preparing modified asphalt mixture with coking sulfur paste modifier (CSPM) is herein proposed. Compared with the matrix asphalt mixture, the Marshall stability of the 30% CSPM modified asphalt mixture increased by 38.3%, the dynamic stability increased by nearly one time (reaching 1847.5 times/mm), the splitting strength ratio increased by 39.3% while the splitting tensile strength decreased by 11.7%. After curing, the performance of the CSPM modified asphalt mixture was further improved. The results show that CSPM improved the high temperature stability and water damage resistance of the asphalt mixture, and the low-temperature anti-cracking performance of that was slightly reduced. Chemical analysis of asphalt binders shows that a little sulfur reacted with asphalt to produce polysulfide compounds (R-Sx-R′), and a part of sulfur existed in the form of crystalline sulfur which was further increased after curing. The presence of crystalline sulfur as an inorganic filler is the key point for improving the high temperature stability and water resistance performance of modified asphalt mixture.

This study elucidates the effects of the particle size, carbonation time, curing time and pressure on the efficiency of carbon storage in Portland cement mortar. Using pressure chamber experiments, our findings show how carbonation efficiency increases with a decrease in the particle size. Approximately 6.4% and 8.2% (w/w) carbonations were achieved in the coarse-sand and fine-sand based mortar samples, respectively. For the hydration/curing time of 7 h, up to 12% carbonation was achieved. This reduced to 8.2% at 40 h curing period. On the pressure effect, for comparable curing conditions, 2 bar at 7 h carbonation time gives 1.4% yield, and 8.2% at 5 bar. Furthermore, analysing the effect of the carbonation time, under comparable conditions, shows that 4 h of carbonation time gives up to 8.2% yield while 64 h of carbonation gives up to 18.5%. It can be reliably inferred that, under similar conditions, carbonation efficiency increases with lower-sized particles or higher-surface areas, increases with carbonation time and higher pressure but decreases with hydration/curing time. Microstructural analyses with X-ray diffraction (XRD) and scanning electron microscopy (SEM) further show the visual disappearance of calcium-silicate-hydrate (C-S-H) together with the inhibition of ettringite formation by the presence of CO2 and CaCO3 formation during carbonation.

In recent times, the production of polyethylene ground plastics has increased markedly in the Philippines. However, current levels of their usage and disposal generate several environmental problems. Recycling is one of the most important actions that are being made to reduce these impacts. The present study used polyethylene ground plastic wastes to investigate their possible use as plastic aggregate in concrete application. The shredded plastic wastes were used in concrete with partial replacement of ½ kg and 1kg by volume of conventional coarse aggregate. Three types of concrete specimens including one without plastic aggregate were used in the study for comparison. All the concrete specimens were tested for their different mechanical properties after a curing period of 28 days. Various physical properties of all aggregates and fresh concrete properties were also tested in the laboratory, these include pound per square inch (psi), Mega Pascal (MPa), Kilo Newton (KN), and the type of fracture. The test for psi, MPa, and kN resulted that concrete mixtures with 1kg ground plastic produced the best result among the three samples having 3150 Psi, 21.7 MPa, and 395.7 KN, respectively. Moreover, the specimens were loaded under a monotonic uniaxial compressive load up to failure by using MATEST hydraulic testing machine with the indicator of kN. The result showed that both standard mixtures of concrete and the standard mixture of concrete with ½ kg polyethylene ground plastic have a comparison infraction that has a result of an SW-Shear Wedge of Type 5, while the standard mixture of concrete with 1kg polyethylene ground plastic has a conical type of a fracture. Based on the several tests conducted, it is concluded that the standard concrete mixture with 1kg polyethylene ground plastic provided the best result compared to other specimens. Furthermore, the use of polyethylene ground plastic waste in the standard concrete mixture provides some advantages like on reduction of plastic wastes, prevention of environmental pollution, and energy saving.

This article aims to evaluate the mass transport properties in concretes with different contents of polypropylene microfiber (0% and 1%, by concrete volume) and crystalline admixture (0%, 1%, and 3%, by cement mass). Water absorption by immersion, water absorption by capillarity, and air permeability tests were performed to evaluate the properties of mass transport. Images of the microstructure of the concretes were used to support the hypotheses discussed. The tests were performed immediately after curing (28 days) and after curing plus 35 and 70 days of wetting and drying cycles. The combined use of polypropylene microfibers and crystalline admixtures may increase the properties of mass transport at an early age. Nevertheless, the nucleation of hydrated phases around polypropylene microfibers contributed to the densification of the concrete pores over time. The crystalline admixture can close larger pores and reduce connectivity between them in the first ages (first 35 days). However, the effect of crystalline admixtures in filling capillary voids requires more time to occur (around 70 days). The void index was reduced between 0 and 70 days by 47%, 42%, and 44% for reference, F + 1CA, and F + 3CA concrete mixtures, respectively.

Both electrolytic manganese solid waste (EMSW) and phosphogypsum (PG) are solid waste that can cause serious pollution to the environment. Therefore, we try to solidify/stabilize heavy metal ions without adding other curing agents. We found that the Mn2+, Ni2+, Zn2+, Pb2+ and Cd2+ concentrations are 2432.00, 1.47, 3.80, 0.22 and 0.06 mg/L in the EMSW liquid leaching, and 0.26, 2.14, 8.62, 2.79 and 0.57 mg/L in the PG liquid leaching. The optimum conditions for synergistic stabilization/solidification are as follows: The ratio of EMSW to PG is 1:3, the stirring time is 2 h, and the solid–liquid ratio is 1:5. Under these conditions, the Mn2+, Ni2+, Zn2+, Pb2+ and Cd2+ concentrations in leaching liquid were reduced to 599.10, 0.33, 0.56, 0.06 and 0.01 mg/L, and the corresponding curing rates were 75.37%, 77.79%, 85.39%, 72.52% and 77.61%, respectively. When the Ni2+, Zn2+, Cu2+, Pb2+ and Cd2+ concentrations were within the permitted level for the GB8978-1996 test suggested by China’s environmental protection law, the residual manganese content in the leaching liquid of cured EMSW was too high to reach the emission standard. This work indicates that the synergistic stabilization/solidification of heavy metal ions has certain application potential.

Mineral waste wool represents a significant part of construction and demolition waste (CDW) not yet being successfully re-utilized. In the present study, waste stone wool (SW) and glass wool (GW) in the form received, without removing the binder, were evaluated for their potential use in alkali activation technology. It was confirmed that both can be used in the preparation of alkali-activated materials (AAMs), whether cured at room temperature or at an elevated temperature in order to speed up the reaction. The results show that it is possible to obtain a compressive strength of over 50 MPa using SW or GW as a precursor. A strength of 53 MPa was obtained in AAM based on GW after curing for 3 days at 40 °C, while a similar compressive strength (58 MPa) was achieved after curing the GW mixture for 56 days at room temperature. In general, the mechanical properties of samples based on GW are better than those based on SW. The evolution of mechanical properties and recognition of influential parameters were determined by various microstructural analyses, including XRD, SEM, MIP, and FTIR. The type of activator (solely NaOH or a combination of NaOH and sodium silicate), and the SiO2/Na2O and liquid to solid (L/S) ratios were found to be the significant parameters. A lower SiO2/Na2O ratio and low L/S ratio significantly improve the mechanical strength of AAMs made from both types of mineral wool.

In this investigation, it was studied the effect of curing temperature on the mechanical properties of pastes made with calcium sulfoaluminate cements synthesised from industrial wastes at a relati...

Peat is an exceptionally problematic soil for construction purposes and is often stabilized by traditional stabilizers (like cement), which emits 0.95-ton carbon dioxide (CO2) per ton of cement during their production. Alkali-activated ground granulated blast furnace slag (GGBS) with its low carbon dioxide (approximately 0.07-ton CO2) emissions and higher strength gain provides a promising substitute to traditional stabilizers. Therefore, this study presents the viability of alkali-activated GGBS-stabilized Indian peat. The three types of peats (sapric, fibric, and hemic) were collected to cover a wide range of variations of fibre (6–73%) and organic content (21–79%). The sodium hydroxide (NaOH) molarities (M) of 6, 9, 12, and 15 were used to activate specimens, with GGBS percentages of 10, 20, and 30% by weight of dry peat and alkali/binder ratios of 0.5, 0.7, and 0.9. The test results show that the UCS of peat-GGBS depends on the molarity of NaOH, A/B, electrical conductivity (EC), pH, curing period, and organic content of the peat-GGBS matrix. The optimum combination for the peat-GGBS blend is 20% GGBS, NaOH molarity of 9, and A/B ratio of 0.7. Furthermore, it was found that UCS increases with the curing period and decreases with organic content (OC). The formation of aluminium silicate, sodium aluminosilicate, and potassium aluminosilicate responsible for strength gain is confirmed by XRD. The FESEM micrographs reveal that these products result in the filling of pore spaces to form a smooth and dense soil-binder matrix.

Integration of cement-based products with nanosized-palm oil fuel ash as supplementary cementing material (SCM) amend its hydration’s degree at early age phase and the microstructural groundworks are relevant to explain the findings. Hence, the present work investigates the microstructure properties of the hardened cement paste (HCP) incorporating nPOFA to study on the effect of nPOFA in cement hydration at an early age phase. An Ordinary Portland Cement (OPC) paste as a set of HCP blended with microsized-palm oil fuel ash (mPOFA) (10-30%) and nPOFA (10-60%) were prepared and cured for 28 days. The microstructural examination of OPC, mPOFA and nPOFA cement pastes at 28 days curing age via Thermogravimetric (TG) analysis, X-Ray diffraction (XRD) analysis, morphology study and Fourier transform infrared (FTIR) spectroscopy analysis. In TG analysis, the relative weight loss of calcium hydroxide (CH) of nPOFA pastes is lower than OPC and mPOFA. Based on the CH peaks at 2?= 18.1°and 34.0° in the diffractogram, it shows that nPOFA pastes give the low CH peaks compare to OPC and mPOFA pastes. In addition, the nPOFA pastes form the dense and compact microstructure of HCP compare to other pastes. Observations from FTIR analysis, nPOFA pastes display a high frequency of Si-O band due to the high rate of pozzolanic reaction. Overall, the findings confirmed the contribution of nPOFA in accelerating the rate of cement hydration and pozzolanic reaction as it reduced the amount of CH in the cementitious matrix.

International audience; This study aims at investigating the lime treatment effect on the changes in microstructure and water retention property of compacted saline soil, with consideration of the aggregate size effect. Two soil powders with different maximum aggregate sizes (Dmax = 0.4 and 5 mm) were prepared and stabilized by 2% lime. The microstructure, total suction and matric suction were determined at various curing times. Results showed that the lime treatment caused a rapid decrease in micro-pores and an increase in macro-pores due to the flocculation of soil particles. During curing, the percentage of micro-pores decreased and that of nano-pores increased slightly. Due to the modification of microstructure, the matric suction increased significantly at 90-day curing. However, the curing time effect on the total suction was insignificant. This was due to the fact that the Ca2+ and Mg2+ in soil pore water and the Ca2+ from hydrated lime were consumed in the precipitations of CaCO3 and Mg(OH)2, cation exchanges and pozzolanic reaction, resulting in a reduction in osmotic suction. Therefore, the increase in total suction was slight, as the increase in matric suction was balanced by the decrease in osmotic suction. The treated specimens with larger aggregates exhibited a larger modal size and thus had a smaller air entry value. The aggregate size effect on the water retention property of total suction and matric suction was found to be insignificant, which could be explained by the similar pore size distribution at micro-pore range and the same soil mineralogy for specimens with different aggregates.

Accelerated carbonation of the cement-based materials has attracted worldwide attention due to the advantages of rapid strength gain and CO₂ sequestration. This work was designed to investigate the mechanism of γ-C₂S compacts under extended carbonation curing to further develop the accelerated carbonation technology. Based on the variation of the mechanical properties, microstructure, and the phase assemblages through the extended carbonation, a multi-step reaction mechanism is proposed in this work. The process can be divided into three stages: phase-boundary-controlled stage; product layer CO₂ diffusion-controlled stage; and CO₂ diffusion and calcium ion dissolution-controlled stage. Correlation between the calcium carbonate polymorph and the controlling factors is also investigated, in which the high calcium ion concentration is beneficial to the formation of calcite. Meanwhile, the stepwise pressurization curing regime based on the multi-steps is proposed to increase the strength obviously, which further verifies the mechanism of multi-step reactions.

The mould-ability of concrete into intricate forms and the versatility of its constituent materials has made concrete to be the most preferred construction material. However, in developing nations such as Nigeria, poor quality of concrete is listed among the common causes of building collapse. Thus, this study investigated the effects of chemical compounds of four commonly used local ordinary Portland cement brands on the compressive strength of normal concrete. The cement was labelled brands A, B, C, and D, respectively, while all the other constituent materials remained constant in this study. The HACH DR 200 direct reading spectrophotometer method was used to analyze the composition of the oxide in each of the cement samples, while the Bogue composition formula was used to estimate the compound compositions of the cement samples. A designed mix proportion of 1:2:4 (cement: sand: granite) at water-cement ratio (w/c) of 0.6 was used to produce the concrete with an expected target strength of 25 N/mm2. Also, the initial and final setting time of the cement samples and the workability of the concrete mixes were determined. Forty-Eight (48) numbers cube samples were cast and tested for compressive strength at 3, 7, 14, and 28 curing days, respectively, using a 150 mm concrete cubes. The result shows the setting time of the cement samples to be within an acceptable period. Also, results indicated that the cement brands have a significant percentage of Tricalcium Silicate (C3S) content and low percentage Dicalcium Silicate (C2S) content responsible for faster hydration rate and higher early strength gain of the concrete. However, it was observed that a higher percentage of Tricalcium aluminate (C3A) leads to higher strength gain from 7 to 28 days of curing age.

This study investigates the suitability of crushed polyethylene terephthalate (PET) waste, which is a non-biodegradable generated waste as a substitute material for natural sand in the production of hollow sandcrete blocks for sustainable infrastructure. The physical properties of the natural sand and crushed PET aggregate materials used in the batching mixtures which include; specific gravity, water absorption, bulk density and particle size distribution were determined. While the mechanical properties; density, compressive strength, and the water absorption of the produced hollow sandcrete block samples using the granulated PET aggregate as a replacement for natural sand at 5%, 10%, 30% and 50% were studied. Results showed that the PET aggregates exhibit lower physical properties compare to natural sand. The addition of the finely granulated PET aggregates as a partial substitute for natural sand gradually reduced the density of the hollow sandcrete blocks as the replacement increases in the mix. However, the water absorption tendency of the sandcrete blocks reduces as the percentage dosages of PET aggregate increases. A similar reduction trend was noticed in the compressive strength of the produced hollow sandcrete blocks. The results showed a strength reduction from 2.564 N/mm2 to 1.140 N/mm2 for sandcrete mixes containing 5% and 50% PET, respectively, and 2.991 N/mm2 to 1.510 N/mm2 for sandcrete mixes containing 5% and 50% PET, respectively as the percentage substitution of sand with PET increases for 7 and 28 days curing age. The obtained results indicate the possibility of using granulated PET aggregate at 5% sand replacement in production of hollow sandcrete blocks of comparable strength to conventional sandcrete blocks. This will help to promote green production for sustainable infrastructure and reducing the menace of plastic pollution in line with the UN Sustainable Development Goals.

The production of concrete based on Portland cement consumes huge amounts of water every year, but water conservation is becoming a global concern. To address this issue, a special bonding material activated by carbon dioxide instead of water was prepared. The hardening performance, the composition and microstructure of the reaction products and the hardening mechanism of this bonding material were evaluated. It was found that the compressive strength of the material reached 78·2 MPa after the carbon-dioxide-activated curing (CDAC) process. The main reaction products were determined to be calcite and polymerised silicon dioxide gels, which formed a dense microstructure and thus contributed to the material's excellent mechanical strength. Furthermore, in this process, water is not chemically consumed and can be easily recovered during the CDAC. The results indicate that this is an ideal bonding material for buildings in water-scarce areas.

Silica or silica-precursor systems are attractive for the protection of wood against biotic and abiotic damages and for improvement of the fire resistance. Alkali metal silicate solutions, also known as water glasses, colloidal silica (nanosilica dispersions) and other inorganic–organic hybrids resulting from the sol-gel chemistry of alkoxysilane compounds, are products available for this purpose. These chemicals are increasingly considered to formulate wood modification products or to develop surface coatings. This review article is focused on in-depth treatments of wood through dipping, soaking or vacuum-pressure impregnation methods. The techniques used to convert monomers and low molecular weight silicate species in water glasses into less soluble and leaching-resistant silica particles, such as heat treatment, acid treatment and reactions with multivalent metal cation salts, are discussed. The similarities and differences between the various raw-impregnation materials and the properties of the final products are highlighted. Water glasses after appropriate curing, colloidal silica and tetraalkoxysilane-based formulations all lead to deposition of silica particles (SiO2) at the surface of the cell walls, in lumens and pores. Low molecular weight organosilanes and other organo-modified formulations that are able to penetrate the wood cell walls and react with wood components are good dimensional stabilizers. The treated wood exhibits, in general, increased mechanical properties (strength, hardness) and improved resistance to biodegradation and fire retardancy. The efficiency of the treatments can significantly be enhanced to a level fulfilling the requirements for industrial applications by the addition of biocides, ultraviolet absorbers or antioxidants, fireproofing compounds (boron or phosphorus-based compounds, multivalent metal salts) and hydrophobic alkylalkoxysilanes. Silica acts as a barrier/support to many of these additives preventing them from leaching.

Global concrete demand is causing depletion of natural resources at an alarming rate. Self-compacting concrete (SCC) is an innovative solution as it uses less aggregates; however, the drawback of SCC is that high cement content is required compared to conventional concrete. Considering that cement production emits 7% of carbon dioxide (CO2) gas emissions, the use of high content of cement in SCC production is concerning. Though the high powder content of SCC may be of a concern, however, it allows the opportunity to substitute the cement content with supplementary cementitious materials. This experimental work was therefore conducted to reduce the cement content by substituting it with waste materials, such as eggshell powder (ESP) and palm oil fuel ash (POFA), and develop an eco-efficient SCC. The cement content was partially substituted by 0 to 5% ESP and 0 to 15% POFA by weight of total binder. A total of 90 cubes of 100 mm and 60 cylinders of 100 × 200 mm dimension were prepared to evaluate the compressive and splitting tensile strengths, modulus of elasticity, and Poisson’s ratio. Furthermore, the environmental impact assessment was conducted to assess the embodied CO2 and eco-strength efficiency of the developed eco-efficient SCC. It was found that the combination of POFA and ESP increased pozzolanic reactivity, developing additional calcium silicate hydrate gels, thus increasing strength. The combination of 2.5% ESP and 5% POFA (a total of 7.5% cement substitution) was deemed to be the optimal combination as it provided better strength in SCC after 28 days of curing, which leads to 9.66% higher compressive strength than the control SCC. Furthermore, the developed SCC was observed to be eco-friendly as it reduced embodied carbon ranging from 3.86 to 15.33% and eco-efficiency ranging from 2.38 to 15.48% on 28 days compared to the control SCC.