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Large quantity of water is required during the conventional curing methods. This becomes challenging in the areas facing water scarcity and for concreting work in high rise structures. In this work, we present a solution for the need of concrete which does not require extra water for curing. In the proposed solution, calcium lignosulfonate in different percentage was introduced as a self-curing agent in fresh concrete. The hardened concrete with calcium lignosulfonate was cured at ambient condition whereas the hardened concrete without calcium lignosulfonate was submerged in water for curing. The properties of fresh and hardened concrete with and without calcium lignosulfonate are compared. The results show a continuous increase in slump with the increase in calcium lignosulfonate, however, 0.3% calcium lignosulfonate is identified as an optimum percentage for desired mechanical property. The durability under saline environment is studied in term of loss in strength. Further, the change in strength is correlated with the mineralogical changes studied using X-ray diffraction results.

The construction industry is always in need of new technologies and products that improve technological characteristics. Alkali-activated materials appear as an alternative to reduce energy costs, improve technological properties and still present themselves as materials with the potential for incorporating industrial waste. The objective of this research was the development of roof tiles through the process of alkaline activation using ash from the kilns of burning of a red ceramic industry. After the process of processing the materials and their characterizations, prismatic specimens (115 × 30 × 20 mm) were made with the replacement of 0, 6.25, 12.5, 25 and 50% ash by metakaolin and subsequently separated into two groups, (i) subjected to curing at room temperature and (ii) subjected to curing at a temperature of 80 °C, in both cases with a curing time of 7, 14 and 28 days. After each curing period and group, the specimens were subjected to technological evaluation of water absorption, porosity, flexural strength and scanning electron microscopy. The results obtained demonstrate that the use of ash from ceramic waste, mainly replacing 12.5% of the metakaolin, promotes a reduction in water absorption and porosity, and an increase in flexural strength. The results obtained at 28 days in thermal curing are 44.05 MPa for 12.5% ash, much higher than the reference composition (16.02 MPa). The increase in strength happens due to the formation of tobermorite, due to the calcium present in the ash, and due to the formation of phases rich in potassium from the ash, such as kalsilite. Thus, it is concluded that the use of ash from ceramic waste is possible in the alkaline activation of roof tiles due to the occurrence of additional mechanisms of alkaline activation.

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.

Future human space exploration and habitation on the lunar and Martian surfaces necessitates in-situ resource utilization (ISRU) for the development of construction materials tailored for infrastructure and environmental protection. Here we explore the use of lunar and Martian regoliths to create construction materials with properties suitable for such structures as landing pads. Alkali activation of a spectrum of lunar and Martian regolith simulants generates geopolymer binders under ambient and vacuum curing conditions as well as exposure to extreme high and low temperatures (600 and -80 °C). Compressive strength is reduced for binders prepared from each simulant after curing under vacuum and exposure to sub-zero temperatures. In lunar simulant binders, the compressive strength is increased after heating to 600 °C, but the opposite effect is observed in the Martian simulant binder. Amorphous aluminosilicate content and percentage of small particles in the simulants are hypothesized to have a positive impact on compressive strength under ambient curing. Iron and magnesium content may be responsible for decreased compressive strength of the Martian binder after heating. This study offers a robust framework for comparing performance of different simulants under the same curing protocols and environmental exposures, as well as offering insight as to the effects of vacuum curing, and exposure to high and low temperature environments on cured binder samples. Developing a landing pad by transporting activator to the lunar surface is shown to be conceptually feasible within current payload constraints.

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.

Environmental sources are diminishing every day and hence, usage of available sources become even more important. The novelty of this research reports the experimental examination of applying Recycled Plastic (RP), Treated Wastewater (TW) and GGBS in concrete. Four groups of mixes were developed (Groups NW, TW, NWG, and TWG) with each group consisting of four mixes, providing a total of 16 mixes. Group NW: 100% Natural Water (NW) with different percent ratio of RP contents Group TW: 100% Treated wastewater (TW) with different percent ratio of RP contents Group NWG: 100% Natural Water (NW) and 50% GGBS (replacement with Portland cement [PC]) with different percent ratio of RP contents Group TWG: 100% TW and 50% GGBS (replacement with PC) with different percent ratio of RP contents. Scientific contribution to the knowledge is using recycled plastic material, treated waste water and 50% GGBS simultaneously in the concrete mix. The experiments performed to compare Fresh (Compaction Factor and Slump tests), Hardened (compressive – cube & cylinder, flexural-beam strengths) and thermal properties (density & thermal conductivity). Results indicate as the plastic ratio increases, the workability of the concrete, decreases (reduction range 5 to 50% in all groups). In addition, the compressive strength values decrease as the amount of recycled plastic increases. Specifically when 50% RP content is used, mixed were affected more in all groups where the mean strength is between 10 to 30 MPa. On the other hand, 50% RP content decreases the density and it was also determined that 100% treated waste water content affected the concrete properties less than RP content in the mix. However, 50% GGBS content did not show a positive effect on the results obtained which may due to a limitation of observing up to 28-day curing age. Finally, it can be recommended to use waste materials with lower thermal conductivity because it supplies thermal comfort for the occupants.

Annually, the thermal coal industries produce billion tons of fly-ash (FA) as a waste by-product. Which has been proficiently used for the manufacture of FA based geopolymer concrete (FGC). To accelerate the usage of FA in building industry, an innovative machine learning techniques namely gene expression programming (GEP) and multi expression programming (MEP) are employed for forecasting the compressive strength of FGC. The comprehensive database is constructed comprising of 311 compressive strength results. The obtained equations relate the compressive strength of FGC with eight most effective parameters i.e., curing regime (T), time for curing (t) in hours, age of samples (A) in days, percentage of total aggregate by volume (% Ag), molarity of sodium hydroxide (NaOH) solution (M), silica (SiO2) solids percentage in sodium silicate (Na2SiO3) solution (%S), superplasticizer (%P) and extra water (%EW) as percent FA. The accurateness and predictive capacity of both GEP and MEP model is assessed via statistical checks, external validation criteria suggested by different researcher and then compared with linear regression (LR) and non-linear regression (NLR) models. In comparison with MEP equation, the GEP equation has lesser statistical error and higher correlation coefficient. Also, the GEP equation is short and it would be easy to use in the field. So, the GEP model is further utilized for sensitivity and parametric study. This research will increase the re-usage of hazardous FA in the development of green concrete that would leads to environmental safety and monetarist reliefs.

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.

Electromagnetic waves in the X-band (8.2–12.4 GHz frequency) are used for radar, satellite communication, and, in some countries, for wireless computer networks. Shielding allows to protect humans and electronic devices from harmful effects of these waves. Cement-based composites containing conductive material can be used for this purpose, and pyrolysed carbonaceous residues (biochars) are promising in this respect. Two different biochars originated from wood (CB) and sewage sludge (SSB) pyrolysis were used as fillers in cement-based composites. The electromagnetic shielding properties of these composites are analysed vs the type and amount of biochar added. The influence of water content arising from different curing and ageing in ambient conditions is investigated for one set of samples. Results show that CB and SSB contain 74% and 30% of graphitic carbon, respectively. In the composites, SSB particles are bulky and scarcely dispersed, while CB particles are elongated and homogenously distributed. Values of Shielding Effectiveness (SE) > 20 decibel at normal incidence are achieved for the composites containing 18% of CB biochar. The influence of ageing was also investigated for a sample with 18% of wood commercial biochar: increasing wet curing increases the shielding effectiveness, while increasing ageing in air decreases the shielding effectiveness values: after 10 weeks, the measured value is about 5 dB less. The evidence suggests that the amount of physically adsorbed water is responsible for this behaviour, and it should be taken into account when dealing with cement based composites used for electromagnetic shielding.

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.

Noncorrosive reinforcement materials facilitate producing structural concrete with seawater and sea sand. This study investigated the properties of seawater and sea sand concrete (SSC), considering the curing age (3, 7, 14, 21, 28, 60, and 150 d) and strength grade (C30, C40, and C60). The compressive behavior of SSC was obtained by compressive tests and digital image correction (DIC) technique. Scanning electron microscope (SEM) and X-ray powder diffraction (XRD) methods were applied to understand the microstructure and hydration products of cement in SSC. Results revealed a 30% decrease in compressive strength for C30 and C40 SSC from 60 to 150 d, and a less than 5% decrease for C60 from 28 to 150 d. DIC results revealed significant cracking and crushing from 80% to 100% of compressive strength. SEM images showed a more compact microstructure in higher strength SSC. XRD patterns identified Friedel’s salt phase due to the chlorides brought by seawater and sea sand. The findings in this study can provide more insights into the microstructure of SSC along with its short- and long-term compressive behavior.

This research focuses on studying the effect of different supplementary cementitious materials (SCMs) such as waste ceramic powder (WCP), lime powder (LP), and ground granulated blast furnace slag (GGBS) in combination on strength characteristics and microstructure of quaternary blended high-strength concrete. To achieve the aims of the study, necessary physical and chemical composition tests were done for the raw materials. Then, mixes were designed into control mix with 100% Ordinary Portland Cement (OPC) and experimental mixes containing 30%, 40%, 50%, and 60% of GGBS, WCP, and LP in combination. Tests were conducted during casting and at curing ages of 7 and 28 days. Accordingly, the control mix which is concrete grade 50 (C-50) as per American Concrete Institute (ACI) mix design is used as a reference for comparison of test results with those specimens produced by partial replacement of SCMs. The characterizations of high-strength concrete are done using consistency, setting time, workability, compressive strength, flexural strength, and morphological tests. The optimum percentage replacement is 50% OPC replacement by 30% GGBS + 10% WCP + 10% LP. Based on the experimental investigations, the workability increases as the replacement level of SCMs increases from 30% to 60% by weight. Compressive strength and flexural strength results increase up to 11.41% and 20% when the percentage replacement increases from 30% to 50% of SCMs replacement at 28 days of curing time, respectively. There are also improvement in the microstructure and significant cost saving due to replacing OPC partially with SCMs with proportions mentioned above. Therefore, the practice of utilizing increased percentage of SCMs in quaternary blend in concrete can be beneficial for the construction industry and sustainability without compromising the quality of the concrete product.

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.

This paper presents a study on evaluating the effect of two key factors, namely, the hybridization of straight and hooked steel fibers and curing methods, on the mechanical properties of ultra-high-performance concrete (UHPC). The UHPC specimens using the same proportions of the water, binder, and filler were prepared considering five different combinations of straight and hooked steel fibers. The UHPC specimens were subjected to normal water curing and steam curing. The mechanical properties studied included the compressive strength, flexural strength, modulus of elasticity, flexural toughness, and steel-UHPC bond characteristics considering steel bars of two different strength grades (G60 and G230). The experimental data were used to discuss the effects of both the hybridization of steel fibers and curing methods on the mechanical properties of UHPC as well as to conduct an analysis of variance (ANOVA) and to obtain the empirical models correlating the variables with the mechanical properties. The test results exhibited a significant effect of the hybridization of the fibers on the studied properties of UHPC. The UHPC containing a higher amount of hooked fibers significantly enhanced the modulus of elasticity, flexural tensile strength, and flexural toughness. The performance of UHPC cured using steam was found better than that cured using water in all aspects.

To achieve sustainability in the field of civil engineering, there has become a great interest in developing reactive powder concrete RPC through the use of environmentally friendly materials to reduce the release of CO2 gas produced from cement factories as well as contribute to the recycling of industrial wastes that have a great impact on environmental pollution. In this study, reactive powder concrete was prepared using total binder content of 800 kg/m3, water to binder ratio (0.275), and micro steel fibers 1% by volume of concrete. The experimental program included replacing fly ash with (8, 12, 16) % by cement weight to find the optimal ratio, which achieved the best mechanical properties of (RPC) at 7, 28, and 90 days with standard curing. Some mechanical properties of reactive powder concrete (flow, compressive strength, tensile strength, and density) were verified. The results at 28 days showed that the compressive strength (96.5) Mpa, tensile strength (9.38) Mpa, and density (2395 kg/m3). The results showed that the percentage of replacement of 8% of fly ash with cement is the optimal percentage, which achieved the highest resistance compared to the others. The results also indicated that it is possible to develop RPC using fly ash with a high withstand stress, tensile strength, and density.

This research aimed to present the improvement of the cementitious material in high-volume fly ash using only one alkali activator. Fly ash was used as a partial replacement for Portland cement type I, varying from 0 to 60% by weight of the binder. Concentrations of NaOH varying from 0.00 to 1.25 molar were used as alkali activator. Paste properties and mortar compressive strength at the ages of 3, 7, 14, 28, 60, and 90 days of water curing were investigated. The results reveal that fly ash paste with an alkali activator provides shorter initial setting time when compared to control paste without alkali activator. The use of 0.50 molar NaOH concentration in mortar containing fly ash not exceeding 50% by weight of binder provides the highest compressive strength at any age of curing. At that concentration, there is a significant increase in the 28-day compressive strength of up to 45% over that of the control mortar. In addition, higher NaOH concentration (not exceeding 1.00 molar) has a significant positive effect on the compressive strength of mortar with higher fly ash content, especially over longer curing periods.

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.

Natural-fiber-reinforced geopolymer composites are environmentally friendly materials that have garnered considerable attention. In practice, the drying shrinkage and uneven dispersion of fibers in geopolymers result in low flexural strength, which limits the use of large-scale composites. In this study, high-flexural strength geopolymer composites with self-assembled nanofiber networks were hybridized using in situ polymerization. Composites with different fiber contents were evaluated via morphology and mechanical strength assessments. A mixed nanofiber and geopolymer solution was created to achieve uniform dispersion, and then the geopolymers were optimized at the nanoscale level using a bottom-up approach to achieve self-assembled nanofiber networks with good interfacial bonding. Due to the water retention properties of the nanofibers and subsequent gel material, the networks facilitated internal curing of the geopolymers, thus preventing drying shrinkage. This ultimately reduced the weight loss and increased the density of the composites. In addition, high flexural strength properties were observed in composites with a fiber content of 0.5%, due to the combination of fiber reinforcement and porosity. Thus, this work introduces new considerations for geopolymer applications.

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.

Cemented paste backfill (CPB) plays an important role in the mining industry due to safety, cost efficiency, and environmental benefits. Studies on CPB have improved the design and application of paste backfill in underground mines. Direct shear is one of the most fundamental parameters for assessing backfill strength. This study harnesses direct shear tests to explore the low confining stress behavior of CPB. We perform all the tests in a standard apparatus on the combination of three binder contents of 4.2%, 6.9%, and 9.7% CPB with four curing times of 3, 7, 14, and 28 days, respectively. The applied confining stress levels vary in a range according to the in situ regime. Results are presented by strength envelope, stress-strain property, and shear strength with curing time and binder content. The data suggest that the shear strength follows the Mohr–Coulomb envelope in which the shear strength and behavior are time and binder content dependent. In addition, the results show that shear strength is strongly related to the binder content than the curing time, namely, the higher the degree of binder hydration, the higher the cementation binding force between CPBs.

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.

In those cases where construction-generated soils with high water contents are used as filling or embankment materials, it is sometimes difficult to satisfy the specified compaction degrees. Recently, soil stabilization using a paper sludge ash-based stabilizer (PSAS) has been developed. Paper sludge (PS) ash is waste generated by the incineration of PS discharged from paper mills. It has been found that PS ash can absorb and retain excess water; and therefore, PS ash can simultaneously improve the stability of muds when it is mixed with them. However, the current mixture design approach for PSAS-treated soils is only applicable to muds with water contents exceeding the liquid limits and cannot be applied to construction-generated soils in which the coarse fraction is dominant. Therefore, this study evaluated the effects of a PSAS on the compaction and mechanical characteristics of coarse-grained soils to use them as materials for irrigation earth dams. A series of compaction tests were conducted on two types of soil samples treated with a PSAS to investigate its effects on the compaction characteristics. The compaction characteristics obtained from the tests were assessed considering the water absorption and retention performance of the PSAS. It was found that the modified optimum water content w*opt of the treated samples, which was evaluated using the amount of water unabsorbed and unretained by the PSAS, was almost equal to the wopt of the untreated samples. Consequently, a new mixture design approach was proposed based on the compaction characteristics. The calculated results successfully demonstrated that, if the compaction curve of an untreated sample and the water absorption and retention ratio, Wab, of the PSAS corresponding to a certain curing period are obtained, the range in the PSAS addition amount, APS1m3, required to attain the targeted compaction degree, (Dc)target, for the curing period can be estimated without conducting compaction tests on the treated samples. Finally, the strength characteristics of the treated samples prescribed by the proposed mixture design method were investigated by conducting CBR tests and CU ¯ TC tests. Based on the test results, discussions were made on the contribution of the proposed mixture design to the strength development of the treated samples and on the development mechanism.

Plastic soil exhibits unfavorited geotechnical properties (when saturation), which causes negative defects to engineering structures. Different attempts (included various materials) were conducted to proffer solutions to such defects by experimenting in practical ways. On one hand, these attempts aimed to improve the engineering characteristics of plastic soil, and on the other hand, to use problematic waste materials as a stabilizer, like cement kiln dust, and to reduce environmental hazards. This paper explored the shrinkage, plasticity, and strength behavior of plastic soil enhanced with cement dust. The cement dust contents were 0%, 5%, 10%, 15% and 20% by dry weight of soil. An experimental series of shrinkage and plasticity tests and unconfined compression tests were carried out to explore the effects of cement dust on the quantitative amount of shrinkage, plasticity characteristics, and shear strength experienced by plastic soil. The effects of curing on soil strength were also investigated. The finding of this paper showed that the critical behavior and plasticity of plastic soil could be reduced by mixing the soil with 15% or 20% of cement dust. The undrained shear strength, cu, of plastic soil-cement dust mixtures increased with the increasing dust content up to 20%. In fact, this strength was affected by the curing period. The best enhancement was attained when the content of cement dust was 20%, and the undrained shear strength was increased more than three times at this content.

This paper aims to study the effect of Carbon Fiber Filament (CFF) with different ratios and lengths on the physical and mechanical properties of cement mortar. An experimental program included 3 cm fixed length of CFF with 0, 0.25, 0.5, 0.75, and 1% different ratios by weight of cement addition were used in cement mortar cubes. Another experimental program of 0.5% CFF ratio with 1, 2, 3, 4, and 5 cm different lengths by weight of cement addition was used in cement mortar prisms. The physical and mechanical properties of cement mortar containing CFF were experimentally investigated at 7 and 28 days of curing. Workability, by means of flow table test, were measured. Density is conducted for cubes and prisms at the age of 28 days. At ages of 7 and 28 days, compressive and flexural strengths were studied. The study showed a reduction in workability with the increase of CFF ratios and lengths by 0.0 to 2.7% and by 0.9 to 5.4% respectively. Moreover, an improvement in density, compressive, and flexural strengths was observed. At ages of 7 and 28 days, the results showed that compressive strength increased by 33 and 31% respectively at 0.5% of CFF ratio while the flexural strength increased by 125 and 327% respectively with CFF length of 5 cm. Doi: 10.28991/cej-2021-03091753 Full Text: PDF

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.

Objectives To specify the concentration of the liquid antibiotics to be added to polymethylmethacrylate (PMMA) and its impact on the quality of the spacer is the purpose of this study with liquid clindamycin added to different cements. Methods In the present study, eight different cement mixtures were prepared and investigated. In the following, number 1 indicates the references, 2 all cements after liquid clindamycin was added to the liquid cement compound, 3 all cements after liquid clindamycin was added to the cement powder, and 4 all cements after liquid clindamycin was added to the cement dough. After curing, cements were filled into metal moulds and a pressure of 3 bar was maintained for 30 min. Mechanical investigations were carried out according to ISO 5833 (2002) and DIN 53435 (2007). For microbiological tests, standardized cylindrical mouldings (diameter: 25 mm, height: 10 mm) were produced and incubated in 10 ml buffer solution at room temperature for 24 h. All eluates were generated by spreading previously established suspensions of Staphylococcus aureus, Staphylococcus epidermidis, Cutibacterium acnes and methicillin‐resistant Staphylococcus aureus (MRSA) with a 0.5 McFarland turbidity standard. Results Apparently, we found that in all investigated cases, the admixture of liquid antibiotic negatively affected the mechanical characteristics of the cement mould. Among the various test groups, the influence on the ISO compression strength and ISO flexural modulus of the investigated test groups was only minimal when liquid clindamycin was added to cement liquid. Compared to admixing of liquid clindamycin into cement powder or dough ISO compression strength and ISO flexural modulus and flexural strength showed the maximum reduction. The efficacy against chosen germs was reduced as well when liquid antibiotic was admixed instead of powder. This admixture of liquid anti‐infective agents resulted in a 234% enhanced elution after 10 days 29 a negative effect on the inhibition zones were detected during the previous period. Conclusion The admixture of powdery antibiotic is preferable to liquid antibiotics. If no powdery antibiotic is available, we can recommend the admixture of liquid antibiotic to liquid cement prior to dough production in case powdery antibiotics cannot be used. However, we discourage the admixture of liquid antibiotic to cement powder or cement dough during early low viscose phase., Experimental arrangement with Palacos R leading to the results.

This paper presents an assessment of the tumbling strength and reactivity behaviour of hybrid fuel briquette (HFB) produced from coal and torrefied woody biomass wastes. Briquettes were produced using 97% coal and 3% torrefied biomass with the blend of pitch and molasses in different ratios as a binder. The briquettes were treated in an inert environment at 200–300 °C for a residence time of 60 and 120 min in a tubular furnace. Fourier Transform Infrared Spectrophotometer (FTIR) was used to obtain the functional groups in the raw materials and the HFB. HFB were exposed to tumbling test (TSI+3mm) after curing and high temperature (1200 °C) exposure. Reactivity test (RI) of the HFB was carried out based on ASTM D5341M-14 standard. The FTIR spectra of the HFB show the presence of aromatic C C bonds and phenolic OH group. The TSI+3mm of the HFB samples drastically reduced from 95.5–98.3% for the treated to 57.4–77.4% for the samples exposed to 1200 °C. The reactivity indices of the HFB were in the range of 48–56%, which indicated that the HFB were highly reactive. Based on the TSI+3mm and RI, the HFB are suitable carbonaceous material in direct reduced iron making through rotary kiln.

Steel slag-treated marine clay (SSTC) is a novel geomaterial used for recycling steel slag. This article reports the effects of the primary curing (the time delay between mixing and fill work) and the subsequent disturbances (the processes of remolding, handling, and placement) on the strength development of the geomaterial. The results of a series of experiments point to the possibility of improving the initial strength of SSTC for maritime fill work. Laboratory tests were performed to investigate the changes in and the recovery of the geomaterial strength brought about by one to three days of primary curing and the subsequent disturbances during various secondary curing times. In the field tests, three embankments, using SSTC that had previously undergone one or two days of primary curing, were constructed in seawater with an actual construction machine. The test results indicated that the initial strength of SSTC previously treated with one, two, or three days of primary curing increased to approximately 14 kN/m2. The loss in strength that occurred at the primary stage of curing was recovered at a later stage of curing, namely, after 28 days, and the strength of the SSTC in the three embankments was 52–70% of the sample that was cured without primary disturbance. Larger amounts of disturbances were applied to the SSTC in the field tests than in the laboratory tests. The field tests produced submerged embankments, 1.8 m in height, with average slopes of 1:2.1–1:2.9, by undergoing one to two days of primary curing. The strength of the SSTC in all the embankments recovered significantly with time after construction, and the unconfined compressive strength of the SSTC exceeded 200 kN/m2 at 100 days, which is deemed sufficient for the construction of embankments. Overall, it was confirmed that the one-day primary curing and the sea-bottom fill method presented better results than the two-day primary curing and the sea-surface fill method, considering the gradient of the slope and the strength-recovery characteristics of the SSTC.

To determine the duration of the heat treatment process on the heating medium (water)To determine the duration of the heat treatment process on the heating medium (water) temperature and layer thickness of the original sample using sous-vide technology, a chicken fillet was selected. The following diagrams were plotted and analyzed: temperature in the chicken fillet specimen as a function of duration of heat treatment process at heating medium (water) temperatures of 60, 70 and 80?C; temperature in the chicken fillet specimen as a function of duration of heat treatment process at thickness of 0.5; 1; 2 cm. Recommendations are given for choosing the optimum temperature regime and thickness of the layer of chicken fillets for cooking by sous-vide technology. At a temperature of water in the thermostat working chamber of 60? C can not be reached inside the sample of product to a temperature of 68-70 ? C, even after 5 minutes of exposure, so there is a possibility of harmful micro-organisms in the finished product. At a temperature of water in the thermostat working chamber of 80 ? C is intense heating of chicken fillets to a temperature of readiness, but the product remains raw because of the short duration of the process, with a further curing the product is heated to a higher temperature of 78-79 ? C, which reduces the quality of the finished product. Optimal selected heating medium temperature (water) in the working chamber of thermostat-70 ?C, which is in the range of recommended regulatory documentation temperatures. At this temperature, the product achieves the necessary cooking temperature of 68-70 ?C, and the duration of heat treatment is reduced by 2.9 times, energy consumption is reduced by 2 times and a high degree of readiness of the product is cooked.

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 surface properties of thermally modified ash wood with a powder coating were investigated, and the results were compared to the unmodified wood. The wood specimens were sanded with 80 grit sandpaper and then pre-heated at 80 °C for 5 min in an infrared oven. The surface of the unmodified and the modified wood specimens were coated with an epoxy/polyester (1 to 1 ratio) hybrid coating using an electrostatic corona spray gun at the pilot plant established in the laboratory. The coatings on the wood specimens were cured at different curing conditions in an infrared oven, i.e., 120 °C/15 min, 140 °C/10 min, and 160 °C/10 min. The results showed that the thermal modification (TM) of the wood caused a slight decrease in the mechanical performance of the surface system (wood substrate and coating film). For example, the scratch and abrasion resistance of the unmodified specimens at the curing temperature of 120 °C were 3.33 N and 135 revolutions but were 3.12 N and 120 revolutions after the TM. However, the average surface roughness (1.26 mu) and contact angle (60.8°) of the distilled water on the cured coatings on the modified wood were lower than those on the unmodified wood (1.86 mu and 80.8°, respectively).

Paper-based friction materials are porous materials that exhibit anisotropy; they exhibit random pore sizes and quantities during their preparation, thereby rendering the control of their pore structure difficult. Composites with different pore structures are obtained by introducing chemical foaming technology during their preparation to regulate their pore structure and investigate the effect of pore structure on the properties of paper-based friction materials. The results indicate that the skeleton density, total pore area, average pore diameter, and porosity of the materials increase after chemical foaming treatment, showing a more open pore structure. The addition of an organic chemical foaming agent improves the curing degree of the matrix significantly. Consequently, the thermal stability of the materials improves significantly, and the hardness and elastic modulus of the matrix increase by 73.7% and 49.4%, respectively. The dynamic friction coefficient increases and the wear rate is reduced considerably after optimizing the pore structure. The wear rate, in particular, decreases by 47.7% from 2.83 × 10−8 to 1.48 × 10−8 cm3/J as the foaming agent content increases. Most importantly, this study provides an effective method to regulate the pore structure of wet friction materials, which is conducive to achieving the desired tribological properties.

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%.

This study investigates the effects of two different Blaine fineness and three distinct curing conditions on the physico-mechanical properties of a geopolymer-ground granulated blast furnace slag (GGBFS) binder mortar activated through a combination of NaOH/NaS alkalis. By ensuring constant curing and mixing conditions, geopolymer mortar (GPM) specimens were prepared and evaluated to determine their capillary water sorption, capillarity coefficient, and change in unit weight, alongside their compressive strength and flexural strength 3, 7, 28, and 56 d after production. It was found that the capillary water sorption decreased by approximately 50% as the curing temperature of the water increased from ambient temperature to 22 °C. The coefficient of capillarity remained constant across the geopolymer materials, irrespective of the Blaine fineness of the GGBFS. Furthermore, the increase in the unit weight, owing to the variation in the Blaine fineness of GGBFS, results in a reduction in the water sorption properties of GPMs. The GGBFS and alkali-based binders imparted a continuous increase in the compressive and flexural strengths. The results revealed that a Blaine fineness of 6000 cm2/g in the GGBFS under water-curing conditions imparted the most significant advantageous effect on the physico-mechanical properties of a GGBFS binder mortar activated through a combination of NaOH/NaS alkalis.

This paper presents an investigation on the adoption of isothermal microwaving in curing ultra-high performance concrete (UHPC) embedded with steel fiber reinforcement. The plain UHPC and the one with varying levels of steel fiber reinforcement are developed by microwave heating at 80 °C for 30 min. The compressive and flexural strength, hydration products, microstructure and interfacial structure of the mixes are evaluated. The results show that, besides the common reactions of hydration, pozzolanic reaction, carbonation, a reaction consuming calcium carbonate is found to occur in the system; furthermore, a Hayne-like phase and a cancrinite-like phase are formed. The formation of them is reduced by increased reinforcement. The accelerated effects of microwave on reaction are found to vary with reinforcement. Accelerating hydration is beneficial from increased fiber contents. Steel fiber reinforcement is more effective in increasing the compressive and flexural strength of UHPC cured with microwaves than cured under standard conditions.

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 publication highlights the production of artistic castings by investment casting using combined ceramic molds. The features of the application of a refractory coating, duplex curing of ceramic shells, cutting of molds, removal of the model composition, annealing of ceramic molds, pouring and separation of the gating‑feeding system under conditions of mass production are considered. Hydrolyzed ethyl silicate (ETS) and aqueous alkaline silica sol are used as a binder. The hydrolysis is carried out with an acidic catalyst. The strength of forms on an aqueous binder before calcination (bending strength σi) is from 1.5 to 2 MPa. The presented technology allows flexible coverage of the entire range of art products. Castings weighing from 5 to 10 kg can be produced in one batch, which significantly reduces the production cycle.

Modern construction methods often result in concrete structures bearing loads at an early age, which is different from the stress condition under the standard curing in the laboratory. This study experimentally examined effects of different ages and external loads on subsequent mechanical and permeability properties of concrete, and investigated the mechanism of effect from the perspective of internal structure changes. The results show when the early age loading reaches 40% of the current concrete strength, the original internal structure of specimens will be severely damaged, reflecting significant increase in the proportion of mesopores and macropores and obvious connectivity cracks, thus making the mechanical and permeability properties deteriorate, and the earlier the applied load, the greater of this deterioration. However, when loading at 10%, the original internal structure cannot be changed greatly due to the low load level, and some parts of the original pores are even compacted rather than expanded which has little effect on subsequent mechanical and permeability properties of concrete.

In this research, the potential improvement of some geotechnical characteristics of soft clay soil using the low Calcium fly ash was evaluated. (These characteristics include unit weight, shear strength, compaction characteristics and soil plasticity characteristics). In addition, the X-ray diffraction test was performed to measure the mineralogical changes in the soft clay soil when the low Calcium fly ash is added. The ordinary Portland cement was used to activate the fly ash. The total percent of flash and cement was10% to investigate the variation in the effectiveness of activation. The optimum moisture content that which computed by the compaction test was adopted in the rest of the experimental program. The test results revealed that the cement could be used to improve the activating of the fly ash efficiently. The maximum value of dry density was marginally affected due to activation from 1.747 to 1.738 g/cm3 along with a corresponding change in optimum water content from 17.45 to 15.5 %. The soil cohesion parameter increased from 188 to 206 kN/m2 whereas the angle of internal friction rose from about 56.7o to 59.1o. Finally, the results of the unconfined compression test reveal that the cement-activated fly ash could present better results than those obtained from a 28-days curing cement.

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

This study aims to evaluate experimentally the potential of expansive soil stabilization using different additives: zeolitic tuff (ZT), lime, and a combination of lime and ZT. Four different percentages of ZT (10%, 20%, 25%, and 30%), three percentages of lime (2%, 4%, and 6%), and variable percentages of their combinations were used to stabilize the soil for pavement subbase application. Atterberg limits, pH, compaction, linear shrinkage, swelling, unconfined compressive strength (UCS), and California bearing ratio (CBR) tests were performed on treated and untreated soil specimens at different curing times. Results showed that ZT additives effectively reduced the plasticity, linear shrinkage, and swell potential in addition to increase the maximum dry unit weight, UCS, and CBR. The results of this study were supported by a microstructural analysis using scanning electron microscopy (SEM) associated with the energy-dispersive X-ray spectroscopy (SEM/EDX) technique. It was determined that the UCS and CBR values for the 4% lime stabilized soil increased by 22% and 70%, respectively, after the addition of 25% ZT. Based on evaluation of the results, an optimum mixture of 25% ZT and 4% lime stabilized soil can be used in pavement subbase applications as it achieved the minimum strength target.

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.

In the case of cement-stabilized soils cured under the influence of overburden stress, it is necessary to consider two different timelines of cementation and consolidation, along which the structures of stabilized soils evolve. These two timelines are interrelated and ought not to be considered separately, especially in the early stage of curing when significant structural changes occur. In this study, the strength and deformation characteristics of cement-stabilized clay subjected to overburden stress during curing was investigated using an unconfined compression test apparatus. For this purpose, three types of specimens were prepared by stabilizing very soft clay with different amounts of cement. Overburden stress was applied for three different time durations during curing. In the series of unconfined compression tests conducted on the specimens with no overburden stress applied during curing, the axial stress initially increases rapidly, then was maintained before finally dropping. In the series of tests with overburden stress applied during curing, the axial stress continues to increase gradually before rapidly declining. The values of unconfined compressive strength are larger for the specimens subjected to overburden stress during curing. The values of the unconfined compressive strength also increase linearly as the duration of applied overburden stress increases. The increase in strength apparently occurs due to increasing dry density accompanied by a decrease in the water content due to the drainage of pore water during the application of overburden stress.

Increased development in the field of construction with the use of sand, stones etc. depletes the natural resources and thus resulted in the scarcity of construction materials. Furthermore, generation of waste from several industries such as steel slag, copper slag, blast furnace slag etc. are being dumped in the nearby landfills leading to disposal problems. The scarcity of construction materials necessitated the utilization of suitable alternative materials with equivalent physical and chemical characteristics. This paper investigates the suitability of copper slag (CS) as a substitute to natural fine aggregate (NFA) in the concrete. The concrete mixes are prepared with 0%, 10%, 30%, 50%, 70% and 100% of copper slag at 0.45 w/c ratio. The behaviour of CS in the concrete was assessed by hardened properties such as compression, tension and flexure at 7, 14, 28 and 90 days and durability properties such as water absorption, porosity and chloride ion penetration at 56 days. Results indicate that the replacement of CS beyond 50% affects properties of the concrete; however increased curing improved the properties of the concrete at higher replacement levels. Characterization studies such as XRD and SEM was performed to examine the effect of CS on the properties of the concrete.