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Objective: To determine the effects of different polishing protocols and curing times on the surface roughness (SR), surface gloss (SG) and surface hardness (SH) of a bulk-fill composite resin (BCR). Methods: A total of 30 block-shaped specimens (40 mm long x 10mm wide x 2 mm thick) were made from Filtek Bulk-Fill composite resin and divided into two groups (n = 15) according to curing time (10 and 40 seconds). Each group was subdivided into five groups (n =3) according to the polishing: laboratory polishing with different silicon paper grits (G1:1200) → (G2:2400) → (G3:4000). Chairside polishing was performed using a series of Sof-Lex spiral (G4) and Jiffy Polisher (G5) points. The SR was measured by a surface profilometer. A Vickers indenter was used to test the SH, and a glossmeter was used to determine the SG at 60 degrees. The SR, SG and SH were quantified before and after polishing. A scanning electron microscopy (SEM) evaluation was then performed. Results: The curing time did not affect the surface properties of the BCR (P > 0.05). Signifinicant differences in SR (ranging from 0.1 to 2 μ) and SG (ranging from 20 to 90 GU [gloss unit]) were found according to the type of polishing protocol (P< 0.05). The SH values following different polishing protocols were significantly higher (ranging from 82 to 95 VH [Vickers hardness]) than the polishing values obtained before the polishing protocols (P < 0.05). Conclusion: The tested chairside polishing protocols presented lower SG and higher SR values than the laboratory polishing protocols. [ABSTRACT FROM AUTHOR]

In order to study the effect of mixed cementitious materials on the consolidation behavior of soft estuarine soils in South East Queensland, a series of oedometer tests were performed in the geotechnical laboratory. To fulfill the objectives, specimens were prepared with different additive content of stabilizing agents and were cured for 7 and 28 days, in which cement content remained at 10% while the content of bentonite was varied from 2.5% to 7.5%. The testing results indicate that both cement-treated and cementbentonite treated samples represented a significant decrease in compressibility compared with untreated samples, in which cement-bentonite mixture shows higher effect on soil stabilization than cement only. However, with the increase of bentonite content, the consolidation behavior of cement-bentonite treated samples did not change consistently which indicates that the effectiveness of cement-bentonite mixture has no linear relationship with the bentonite content and the optimum bentonite content is around 5%. [ABSTRACT FROM AUTHOR]

The dissolution of copper sulphide ores continues to be a challenge for the copper industry. Several media and leaching alternatives have been proposed to improve the dissolution of these minerals, especially for the leaching of chalcopyrite. Among the alternatives, pretreatment prior to leaching was proposed as an option that increases the dissolution of copper from sulphide ores. In this study, a mineral sample from a copper mining company was used. The copper grade of the sample was 0.79%, and its main contributor was chalcopyrite (84%). The effect of curing time (as pretreatment) in a chloride media on copper sulphide ore was evaluated at various temperatures: 25, 50, 70 and 90 °C. The pretreated sample and leaching residues were characterized by X-ray diffraction, scanning electron microscopy, and reflected light microscopy. Pretreatment products such as CuSO4, NaFe3(SO4)2(OH)6, and S0 were identified although with difficulty, due to the low presence of chalcopyrite in the initial sample (1.99%). Under the conditions of 15 kg/t of H2SO4, 25 kg/t of NaCl, and 15 days of curing time, a copper extraction of 93.1% was obtained at 90 °C with 50 g/L of Cl− and 0.2 M of H2SO4.

The direct foaming method combined with gelcasting was employed to prepare mullite ceramic foam. Triacetin, polyimide and hydroxypropyl cellulose were creatively proposed as gelling agent for gelcasting process, respectively. The influence of gelling agent on rheological properties and the correlation rule with the curing time were studied. The results show that different kinds of gelling agent have different influence on rheological properties. It is considered that the rheological properties have significant influence on the curing time. Ameliorating the thixotropy, improving the rate of viscosity growth, and enlarging the linear viscoelastic domain of foam slurry are conducive to shorten the curing time of foam slurry. Among these three gelling agents, the triacetin obtains the optimal effects, the initial curing time and curing time of foam slurry is both shortest.

При моделировании процесса отверждения водно-дисперсионных и полиуретановых лакокрасочных материалов при терморадиационном нагреве за основу взят В-план второго порядка. Определены переменные факторы, сформирован план эксперимента и проведены соответствующие исследования. По результатам экспериментов найдены коэффициенты уравнений регрессии второго порядка, проведена проверка их значимости по критерию Стьюдента. Достоверность полученных зависимостей проверена при помощи критерия Фишера. Построив поверхности отклика и проанализировав полученные результаты, установлено, что основное влияние на время отверждения лакокрасочных материалов оказывает высота расположения излучателя над поверхностью образца. Изменение толщины наносимого слоя лакокрасочного материала оказывало несущественное влияние на время отверждения лакокрасочного покрытия. Установлено, что слишком быстрый рост температуры на поверхности образцов вызывал ухудшение качества. На изделиях наблюдалось появление таких дефектов поверхности, как "пузыри", "кратеры" и "проколы". В связи с этим, в дальнейших исследованиях решено оценить влияние положения излучателя на качество поверхности. Установлено, что полученные уравнения регрессии имеют практическую значимость для предприятий, занимающихся отделкой столярно-строительных изделий из древесины, а также мебельных деталей.

Lime concrete and lime treatment are two attractive techniques for geotechnical engineers. However, researches have rarely been carried out to study the effects of moisture and capillary action due to increasing groundwater level on geotechnical properties of lime concrete. The aim of this study is to investigate the effects of curing time and degree of saturation on some of geotechnical properties of lime concrete such as unconfined compressive strength (UCS), secant modulus (Es), failure strain, brittleness index (IB), and deformability index (ID) using unconfined compression tests. First of all, geotechnical and chemical properties of used materials were determined. After curing times of 14 d, 28 d, 45 d, and 60 d in laboratory condition, the specimens were exposed to saturation levels ranging from 0 to 100%. The results showed that the moisture and curing time have significant effects on the properties of lime concrete. Based on the results of scanning electron micrograph (SEM) test, it was observed that the specimen was characterized by a rather well-structured matrix since both the filling of a large proportion of the coarse-grained soil voids by clay and the pozzolanic activity of lime led to retaining less pore water in the specimen, increasing the UCS and Es, and consequently resisting against swelling and shrinkage of the clay soil. Moreover, due to the pozzolanic reactions and reduction of water, by increasing the curing time and decreasing the degrees of saturation, UCS, Es, and IB increased, and ID decreased. Based on the experimental results, a phenomenological model was used to develop equations for predicting the properties in relation to the ratio of degree of saturation/curing time. The results showed that there was a good correlation (almost R2 > 90%) between the measured parameters and the estimated ones given by the predicted equations.

Introduction: The use of earthen materials is common in hot and dry areas around the world, due to a cheap, abundant and easy access to materials. Today, the use of earthen materials is common in urban and rural areas in developing countries. In Iran earthen materials have partly shaped our architectural culture and identity. Kahgel is one of the oldest traditional plastering and mortars in Iran, which has been used to insulate the roof and facades of buildings from moisture and rainfall. Although the importance of processing and curing mortars and plasters is well known among architecture and building professionals and builders, no research has been conducted on the effect of processing time upon the physical quality and mechanical properties of traditional mortars, especially Kahgel. The main purpose of this study is to evaluate the importance and duration of curing process on the physical and mechanical properties of Kahgel using experimental methods. Material and methods: As the first step, soil samples were taken from different areas of Isfahan and then these samples were examined using different experimental methods. Then the most appropriate soil sample in terms of physical and mechanical properties was selected. Several samples of Kahgel mortars were produced using the selected soil sample and different percentages of straw fibers. For these kahgel samples the compressive strength, tensile strength, linear shrinkage and cracking were measured to determine the most appropriate combination of selected soil mixed with straw fibers. In the second phase of the study, the type of soil and straw percentage were not changed, while the processing time was considered as an independent variable. The new Kahgel samples were prepared by a variety of processing time and then their compressive strength and tensile strength were measured to examine the effect of the curing time on the mechanical properties of Kahgel. Results: The results indicate that the compressive strength dropped with increasing straw fiber content and increased with increasing soil content. The results of all the tests indicate that tensile strength of Kahgel increased with increasing straw fiber content up to 6 %, but the higher straw contents decreased tensile strength. The linear shrinkage of samples decreased with increasing straw fiber content. The results showed that the curing time of Kahgel affects its mechanical properties, especially compressive strength and tensile strength. Therefore, the mechanical properties of Kahgel can be improved by increasing the duration of curing time.

The objective of the presented paper is to investigate the performance of concrete containing volcanic scoria as cement replacement after 7, 28, 90, and 180 days curing. Five performance indicators have been studied. Compressive strength, water permeability, porosity, chloride penetrability, and reinforcement corrosion resistance have all been evaluated. Concrete specimens were produced with replacement levels ranging from 10 to 35%. Test results revealed that curing time had a large influence on all the examined performance indicators of scoria-based concrete. Water permeability, porosity, and chloride penetrability of scoria-based concrete mixes were much lower than that of plain concrete. Concretes produced with scoria-based binders also decelerated rebar corrosion, particularly after longer curing times. Furthermore, an estimation equation has been developed by the authors to predict the studied performance indicators, focusing on the curing time and the replacement level of volcanic scoria. SEM/EDX analysis has been reported as well.

In this study, the impact of three different types of polymer on the flowability, consistency, setting time, density and mechanical properties of cement mortar were investigated. Three types of polymer with different percentage up to 0.25% (by dry weight of cement) were used. The flowability of cement mortar was kept at 110 ​± ​5% as recommended by ASTM standard. Addition of 0.25% of polymers (A, B, and C) reduced the required water to reach the standard flow by 26.5%, 26%, and 27% respectively. Also, the flowability, compressive strength, and flexural strength at different curing times were increased with increasing the polymer content. Addition of 0.25% of polymers to the cement mortar increased the compressive strength of the cement mortar by 197%–230% based on the types of polymer, water to cement ratio (w/c) and curing time. The tensile bonding strength of cement mortar increased by 45%–168% based on the types of polymer, w/c and curing time. Nonlinear model (NLM) was used to separate the effect polymer contents, w/c and curing time on the compressive strength of cement mortar. The Vipulanandan correlation model was also used to correlate the polymer content with the fluidity of cement paste, compressive and flexural strengths of cement mortar modified with different types of polymer.

In the industrial field, manufacturing time is one of the most important factors affecting production costs. Structural adhesives require long curing times (i.e., 3–4 weeks) before the joined components can be safely employed. The aim of the present work is to test the effect of several thermal treatments on a commercial epoxy structural adhesive on the final resistance of single lap joints, trying to attain the possibility of a curing time reduction. Aluminum alloy 5083, typically employed in marine applications, is used as the substrate. Both the adhesive and the joints are treated at different temperatures/times, and then tensile tests are carried out to obtain the mechanical resistance and study the failure modes. A statistical analysis allows the evaluation of the effects of the thermal cycles on the mechanical performances of the joints and the comparison with those cured with the standard procedure.

An option to improve the leaching efficiency of chalcopyrite is pretreatment prior to leaching. Pretreatment variables, such as the curing time and the addition of chloride, can increase the kinetics of copper extraction, particularly for sulphide ores. However, there has been little research on the topic. The reactions that govern this phenomenon have not been clearly identified. In this study, the effects of sulphuric acid and sodium chloride agglomeration and curing on chalcopyrite leaching were evaluated at various temperatures: 25, 50, 70, and 90 °C. The pretreated ore and leach residues were characterised by X-ray diffraction, scanning electron microscopy, and reflected light microscopy. Under the conditions of 15 kg/t of H2SO4, 25 kg/t of NaCl, and 15 days of curing time (as pretreatment), the following products were identified: CuSO4, NaFe3(SO4)2(OH)6, Cu2Cl(OH), and S0. Increasing the curing time and leaching temperature increased copper leaching. The copper extraction was 94% when leaching at 90 °C after pretreatment with 50 g/L of Cl− and 0.2 M of H2SO4. Elemental sulphur, jarosite, and copper polysulphide (CuS2) were detected in the leaching residues.

• A method to assess the phase assemblage combining various techniques. • Differences between phase assemblage of various cement pastes at different age. • The characteristics of C-S-H produced during the various reactions. For economical and ecological reasons, supplementary cementitious materials (SCM) are increasingly used in concrete. Although having a lot of advantages, concretes with SCM have different cement matrices and do not have the same evolution as a function of time as CEM I concretes. In this paper, the microstructure of various cement pastes with/without SCM (slag GGBS, fly ash FA and metakaolin MK), has been investigated as a function of the curing time. The microstructure was characterized not only by usual techniques such as XRD and TGA-DTA, but also by 29Si and 27Al NMR spectroscopy. The use of a combination of techniques for microstructural characterization allowed to quantify the proportion of each cementitious phase. This quantification showed the evolution of the cementitious matrices as a function of the binder content and of the curing time. For example, the alumina content in the C-S-H and the average length of C-S-H chains are higher for cement pastes with SCM than for OPC ones. Hydrated alumina phases proportions (AFt, AFm and TAH) are also higher in SCM cement paste. For MK and FA cement pastes, in addition to pozzolanic reactions, it seems that a small part of calcium from clinker hydration is used to form these aluminate phases. [ABSTRACT FROM AUTHOR]

The efficiency of a commercially manufactured sulphonated oil (SO) agent in treating a highly expansive soil was investigated through an extensive experimental program. A total of six SO to water mass concentrations, i.e. 0.25, 0.5, 0.75, 1, 1.25 and 2.5%, were examined. The test program included swell–load oedometer, unconfined compressive strength and cyclic wetting and drying tests. SO-stabilisation amended the soil's mechanical behaviour through improvements achieved in swelling and strength characteristics. The reduction in swelling potential and swelling pressure was dependent on SO concentration, while the effect of curing time was found to be insignificant. A similar dependency was concluded for the unconfined compressive strength and stiffness of the stabilised soil. Both dependencies suggested an SO concentration of 1.25% capable of yielding an optimal stabilisation scheme. Results of the cyclic wetting and drying tests indicated that the beneficiary effects of SO-stabilisation at optimum concentration, particularly in ameliorating the adverse effects of swell–shrink-related volume changes and to some extent increasing the strength, are strongly preserved under the influence of alternate wetting and drying. [ABSTRACT FROM AUTHOR]

A total of 16 pullout specimens were tested to investigate the effect of curing conditions on bond behavior of near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) strengthening concrete under curing temperatures from 35 to 65°C (95 to 149°F) and curing times from 6 to 12 hours. It was compared to that of specimens in ambient conditions (16°C [60.8°F]). On these bases, a nonlinear local bond-slip model was proposed. Two key parameters-- A and B--are employed in the proposed bond-slip model, the specific expressions of which were mainly related to ultimate pullout load and peak shear stress of the specimen. The results show that the bond behavior of CFRP strip represents a negative quadratic curve with curing temperature and positive inverse tangent curves with curing time, respectively. The nonlinear local bond-slip model, considering the curing temperature-time, is deduced and validated. [ABSTRACT FROM AUTHOR]

The present article focused on the residual strains and deformation of the laminates fabricated by rapid hot press process using prepreg. Strain gauges and laser tracker were utilized to measure the residual strains and deformation of the laminates. By studying the effects of curing time and de-molding temperature on residual strains and deformation of composite laminates, the efficient curing conditions were proposed and good processing quality was ensured. The results indicate that the laminates with low curing degree incline to generate high residual stresses during curing and cooling processes. The effects of cure duration and de-molding temperature on the deformation degree and type of laminates are significant. In order to ensure both curing efficiency and low deformation, the curing time of the resin and de-molding temperature should be designed cautiously. The experimental results suggest that the curing duration longer than 12 min is needed, and the de-molding temperature should be no less than 40°C lower than glass transition temperature of the cured matrix. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The best fog seal with sand materials are optimized and selected. • A technical method for evaluating the open traffic time of fog seal materials is presented. • The evaluation index of traffic opening of fog seal with sand is proposed. Abstract Fog seal with sand (FSS) became a promising technique for the preventive maintenance of flexible pavements. However, there is no quick and effective test method to evaluate whether it is possible to open the road to traffic shortly after the rehabilitation work. This study aims to introduce a new evaluation method to confirm the exact traffic opening time. In this paper, experimental works were performed based on the empirical tests, in terms of penetration, ductility, softening point, viscosity, permeability, and sand optimization tests to determine the best material. Evaporation and load abrasion tests were conducted to attain essential information that will help in establishing the new evaluation method and standard. Meanwhile, Damping test was conducted to prepare the stained pad specimens for the image analysis using Image Processing Technology (IPT). Results show that Material C (from SealMaster) had the best performance of rejuvenation and permeability. In addition, when the application rate ranged from 1.4 kg/m2 to 1.68 kg/m2 and the temperature interval ranged from 20 °C to 40 °C, it took four hours or more to complete the curing process. Finally, 2% of the stained pixel was confirmed as a terminal condition. A standard protocol based on the damping test and IPT has been established to decide the exact curing time required prior to opening the road for traffic. [ABSTRACT FROM AUTHOR]

Induced stresses in sprayed concrete (or shotcrete) are quite complex to evaluate and depend on many factors such as the size and depth of the tunnel, the geomechanical characteristics of the surrounding ground in which the tunnel is excavated, the type of shotcrete, the evolution of its mechanical parameters over time and the excavation face advance rate. In particular, the evolution of the mechanical properties of the shotcrete is crucial regarding the interaction with the tunnel wall and the development of the bending moments and the normal forces which occur along the circumference of the lining. In this research, a new calculation procedure based on the combined use of two calculation methods, the convergence confinement and the hyperstatic reaction methods, is presented. Thanks to this procedure, it is possible to progressively apply the load acting on the lining as the curing phase of the concrete progresses and therefore with the evolution of its mechanical parameters. This procedure has been applied to several examples of calculation, obtaining useful considerations regarding the mechanical behavior of the shotcrete lining when some fundamental parameters of the calculation change. It is possible to achieve bending moments and forces in the lining with the progress of the load steps. It is also possible to determine the trend of the lining safety factor over time and at the end of the loading phase, allowing a proper design of the support, with particular attention to the type of shotcrete and the thickness of the lining. [ABSTRACT FROM AUTHOR]

Highlights • The dynamic fracture toughness experiments are performed using the SHPB system. • The dynamic fracture toughness increases with loading rate and curing time. • The water content has little effect on the fracture toughness of fly-ash based mortars. • The water content has effect on the fracture toughness of GGBFS based mortars. • Proposal of formulas to describe effects of curing time and loading rate on fracture toughness. Abstract Alkali-activated binders made from industrial waste have become a potential alternative of ordinary Portland cement (OPC) because of their low energy consumption and greenhouse gas emissions. This paper aims to evaluate the fracture properties of alkali-activated-binder-based mortars subjected to dynamic loading. We investigated the mortars containing low-calcium (i.e., fly ash) and high-calcium (i.e., ground granulated blast furnace slag (GGBFS)) alkali-activated binders, which have different chemical properties and microstructures. The activators in these mortars are NaOH and sodium silicate solutions. Two groups of specimens made with different water ratios were tested for both fly ash and GGBFS based mortars. Split Hopkinson pressure bar (SHPB) system with the notched semi-circular bend (NSCB) specimen was used to conduct dynamic fracture tests, and dynamic mode-I fracture toughness was measured to provide a comprehensive understanding of the dynamic fracture behaviors of alkali-activated-binder-based mortars. The results show that the fracture toughness of alkali-activated mortars increases with the loading rate and curing time. Moreover, the water content has little influence on the dynamic fracture toughness of fly-ash based mortars, but it significantly affects the dynamic fracture toughness of GGBFS based mortars. Finally, the dependence of dynamic fracture toughness for fly-ash and GGBFS based mortars on the loading rate and curing time is described by empirical formulas. [ABSTRACT FROM AUTHOR]

Alkali-activated cements (AAC) have been extensively studied for different applications as an alternative to Portland cement (which has a high carbon footprint) and due to the possibility of including waste materials such fly ash or slags. However, few works have addressed the topic of stabilised soils with AAC for unpaved roads, with curing at ambient temperature, where the resistance to wetting and drying (WD) as well as the mechanical properties evolution over time is particularly relevant. In this paper, silty sand was stabilised with an AAC synthesised from low calcium fly ash and an alkaline solution made from sodium silicate and sodium hydroxide. The evolution of stiffness and strength up to 360 days, the tensile strength, and the performance during WD cycles were some of the characteristics analysed. Strength and stiffness results show a significant evolution far beyond the 28th curing day, but still with a reasonable short-term strength. Strength parameters deduced from triaxial tests were found to be very high with stress–strain behaviour typical of cemented soils. Durability properties related to resistance to immersion and WD cycles were found to comply with existing specifications for soil–cement, giving validity for its use as soil–cement replacement. [ABSTRACT FROM AUTHOR]

Abstract Thin spray-on liners (TSLs) are fast-setting multi component polymeric materials applied on rock or coal surface with a thickness of 2–5 mm that have fairly high tensile strength, adhesion, and elongation capabilities. Compared to conventional surface support elements, TSLs with polymer content exhibit different material responses over time. As a matter of fact, the creep behaviour of TSLs under a constant load has a significance for the evaluation of the long term performances of TSLs. This paper investigates the nonlinear creep behavior of a polymer based TSL for different curing times. Experimental studies were completed to show the nonlinear time-dependent response of the liner under various constant load and curing time conditions. Dogbone shape test specimens were sustained under constant loads up to 2 months of testing time for different test sets. New equations were proposed for rupture time prediction (creep rupture envelopes) which may aid support design engineers to estimate the effective permanent support time and maximum allowable strain amount of the TSL. Test results were used to construct nonlinear viscoplastic models and viscoelastic models consisting of one independent spring and multi Kelvin–Voight elements. A good agreement was obtained between model predictions and experimental values. Generated constitutive models might aid to further numerical studies in TSL literature. [ABSTRACT FROM AUTHOR]

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• The engineering properties of geopolymer-stabilized soils were illustrated. • Geopolymer gel formation has been validated in stabilized soils. • A contrasting investigation of different process parameters that influence the behaviour of soft soils was described. • UCS predictive models based on ANN and GMDH were discussed. • The mechanism of soil-geopolymer interaction was discussed. The efficiency and survivability of any structural component are determined not only by the quality of the building materials used but also by the geological conditions underneath the base of any structure. Soft soils (peat, clay, fine silt, and loose sand deposits)underneath the building structures are frequently the source of grave problems such as cracking, sinking, excessive settlement, and so on. It is never recommended to use untreated soil for engineering purposes. There are myriad techniques and additives (natural or man-made) available to enhance the engineering properties of these soils. However, due to impoverished performance, most of these methods are now redundant. These limitations have resulted in the rise of geopolymer as a feasible alternative to the conventional techniques of soil stabilization. Geopolymer stabilization occurs through the creation of a sodium and calcium aluminosilicate gel, which adheres to the neighboring clay particles and solidifies into a thicker, firmer matrix. This review investigates whether the stabilized soil can enhance engineering properties (strength, durability, permeability, stability, swell-shrinkage assets) and lessen the harmful impacts on the environment. Moreover, this review will aim to determine whether combining various additives with geopolymer can boost soil performance. [ABSTRACT FROM AUTHOR]

Very often, pavements constructed in an economical manner or matching surface elevations of adjacent lanes cannot be designed for the soil conditions of the existing subgrade. Therefore, there is a need to stabilize the soil with an appropriate chemical substance in order to increase its strength to a satisfactory level. For the enhancement of subgrade soil strength characteristics, lime and cement are the most commonly used stabilizers. An experimental program was directed to the evaluation of a clayey soil and its mixtures with different cement contents performing tests on the index properties, the moisture-density relation, the unconfined compressive strength, and linear shrinkage. There is a definite improvement in strength. The time interval used to cure the prepared specimens affected positively both strength and plasticity features of the mixtures. A comparison with mixtures of the same soil with lime has been made, because of the wide use of lime in clay soil stabilization projects.

One of the common methods for quick determination of compressive strength as one of the most important properties for assessment of cement quality is to apply various modeling approaches. This study is aimed at finding a model for estimating the compressive strength of phosphorus slag content cements. For this purpose, the compressive strengths of chemically activated high phosphorus slag content cement prepared from phosphorus slag (80 wt.%), Portland cement (14 wt.%) and a compound chemical activator containing sodium sulfate and anhydrite (6 wt.%) were measured at various Blaine finenesses and curing times. Based on the obtained results, a primary stochastic model in terms of curing time and Blaine fineness has been developed. Then, another different dataset was used to incorporate composition variable including weight fractions of phosphorus slag, cement, and activator in the model. This model can be effectively used to predict the compressive strength of phosphorus slag content cements at various Blaine finenesses, curing times, and compositions.

The stabilization of soil through the addition of fly ash has been shown to be an effective alternative for improving the strength and stiffness of soil through the resulting chemical reactions. The chemical reaction that occurs dissociates the lime (CaO) in the fly ash, and the establishment of cementitious and pozzolanic gels (consisting of calcium silicate hydrate (CSH) gel and calcium aluminate hydrate (CAH) gel) binds the soil particles and increases the strength and stiffness of the soil. Investigations into the mechanical properties of sands stabilized with fly ash (fly-ash-stabilized sands) were conducted through a series of unconfined compressive strength (UCS) and direct shear strength tests for various fly ash percentages, curing times, grain sizes, degrees of saturation during sample preparation, and content of fines. It was found that the mechanical properties—UCS and direct shear strength (DSS)—of fly-ash-stabilized sands increased with both increasing fly ash content in the specimen and curing time, but decreased with increasing grain size, degree of saturation during sample preparation, and content of fines. The results indicated that fly-ash-stabilized sands required more than a month to attain their optimum performance with regard to binding sand particles.

The effects of three main factors, including polypropylene fiber content, composite cement content and curing time on the unconfined compressive strength of fiber-reinforced cemented clay were studied through a series of unconfined compressive strength tests. The experimental results show that the incorporation of fibers can increase the compressive strength and residual strength of cement-reinforced clay as well as the corresponding axial strain when the stress peak is reached compared with cement-reinforced clay. The compressive strength of fiber-reinforced cement clay decreases first, then increases with small-composite cement at curing time 14 d and 28 d. However, fiber-reinforced cement clay’s strength increases with the increase of fiber content for heavy-composite cement. The compressive strength of fiber-composite cement-reinforced marine clay increases with the increase of curing time and composite cement content. The growth rate increases with the increase of curing time. The failure mode of composite cement-reinforced clay is brittle failure, while the failure mode of fiber-reinforced cemented clay is plastic failure.

This data article provides a comparison data for nano-cement based concrete (NCC) and ordinary Portland cement based concrete (OPCC). Concrete samples (OPCC) were fabricated using ten different mix design and their characterization data is provided here. Optimization of curing time using the Weibull distribution model was done by analyzing the rate of change of compressive strength of the OPCC. Initially, the compressive strength of the OPCC samples was measured after completion of four desired curing times. Thereafter, the required curing time to achieve a particular rate of change of the compressive strength has been predicted utilizing the equation derived from the variation of the rate of change of compressive strength with the curing time, prior to the optimization of the curing time (at the 99.99% confidence level) using the Weibull distribution model. This data article complements the research article entitled “Prediction of the curing time to achieve maturity of the nano-cement based concrete using the Weibull distribution model” [1].

Cemented soil impermeable projects directly or indirectly contact an underground corrosive environment in most cases, which could cause reduced impermeability and malfunction of the cemented soil. Laboratory simulation permeability tests of cemented soil were conducted under different cement ratios in acidic and alkali environments. The variation in the permeability coefficient of the cemented soil was studied under different curing times, pH, and cement contents. Using scanning electron microscopy (SEM) and energy spectrum analysis, the permeability of cemented soil in acidic and alkali environments was studied at the microstructure level. The test results show that an acidic environment has a major effect on the permeability coefficient of cemented soil with a low cement content, and a greater cement content offers increased resistance to acid erosion. In an alkali environment of pH 9-13, the permeability coefficient of the cemented soil gradually decreases as the curing time increases. The research results provide technical parameters for the impermeability and durability design and application of cemented soil in impermeable projects, which has important engineering implications. [ABSTRACT FROM AUTHOR]

Abstract It is well known that the leaching of chalcopyrite has very slow kinetics. The generally higher reactivity of chalcopyrite in chloride as opposed to sulfate solutions has resulted in many studies of chloride systems for the hydrometallurgical treatment of chalcopyrite. Despite much progress on the chloride leaching process, agglomeration and curing has received less attention over the past years. This paper reports a study on the effect of addition of chloride ion in the agglomeration and the effect of curing time on the overall leaching process of chalcopyrite ore. The work involved leaching tests carried out in columns containing 3.0 kg of agglomerated ore irrigated with raffinate solution under ambient conditions. Experiments with agglomerates produced at different concentration of chloride (20, 50 and 70 kg/t) leach at approximately the same rate. It has been demonstrated that chloride ions presence is necessary to improve the leaching kinetics, but high concentrations of chloride are not essential under ambient conditions. The rate of dissolution of chalcopyrite ore agglomerated with high concentrations of acid and chloride ions increases as the curing period increases from 15 to 80 days observing extraction of copper up to 60% in 20 days of leaching. In all experiments, the shape of the leach curves indicate that the copper that has been solubilized during the curing period is rapidly leached followed by continuous slow leaching thereafter. This study supports the addition of chloride at the agglomeration stage as a viable route for the treatment of low-grade copper sulfide ore. Highlights • Ore agglomerated in extreme condition with high concentrations of acid and chloride increases the dissolution of chalcopyrite. [ABSTRACT FROM AUTHOR]

Abstract Combined treatment techniques have been adopted by many pavement designers and site engineers to improve the strength and stability of subgrades or foundation soils of expansive sites. In this regard, research was conducted to investigate the effect of curing time on strength development of black cotton soil (BC soil) stabilized with 10% quarry fines (QF) and varying percentages (0–16%) of cement kiln dust (CKD). Preliminary tests such as Atterberg limits, compaction parameter test together with a series of unconfined compression tests were conducted on soil mixtures. Specimens for unconfined compression tests were prepared at their respective optimum moistures, compacted using British standard light (BSL) compaction effort and tested at curing times of 7, 14, 21 and 28 days. Data from the study revealed that the curing duration exerted a significant influence on the stress–strain behavior of soil mixtures together with the strain at failure which decreased by about 30–50% as the curing time increased. Unconfined compressive strength data showed improved strength values ranging from 1.25 to 5.25 times higher than the value for specimens tested immediately after preparation. Data developed in this study are expected to be useful to pavement designers and site engineers in the field implementation of the stabilization scheme such as when to open the stabilized layer to construction traffic or when to proceed with further construction works. [ABSTRACT FROM AUTHOR]

Abstract Purpose The aim of this in vitro study was to assess conversion degree (DC), micro-hardness (MH) and bond strength of two dual-curing resin cements employed under translucent monolithic zirconia irradiated with different time protocols. Methods 84 square shaped samples of 1 mm thickness were prepared from high translucency zirconia blocks and divided into two groups (n = 24) according to the cement employed: (1) Rely-X Ultimate; (2) Panavia SA. Each group was further divided into 3 subgroups (n = 8) according to the irradiation time: (a) no light; (b) 20 s; (c) 120 s. Light curing was performed 60 s after the sample was placed on the diamond support of a FT-IR spectrophotometer with a high power multiLED lamp. Final DC% were calculated after 10 min. After 24 h, Vickers Test on the cement layer was performed. The same protocol was used to lute composite cylinders in order to evaluate microshear bond-strength test. ANOVA and Bonferroni tests were performed to find differences between MH and bond-strength to zirconia, while for DC% the Scheirer–Ray–Hare two-way test was used. Results The two cements reached higher DC% in subgroup (b) and (c). As concern MH, statistics showed an increase in curing time was able to improve MH significantly. Bond-strength was not affected by irradiation time only for Panavia SA. Conclusions The first null hypothesis has to be rejected since DC% and MH of the dual-cements tested were influenced by the curing time. The second null hypothesis is partially rejected since the bond strength was influenced by the curing time only for Rely-X Ultimate. [ABSTRACT FROM AUTHOR]

Chondroitin sulphate is a sulphated glycosaminoglycan biopolymer composed over 100 individual sugars. Chondroitin sulphate nanoparticles (NPs) loaded with catechin were prepared by an ionic gelation method using AlCl3 and optimised for polymer and cross‐linking agent concentration, curing time and stirring speed. Zeta potential, particle size, loading efficiency, and release efficiency over 24 h (RE24 %) were evaluated. The surface morphology of NPs was investigated by scanning electron microscopy and their thermal behaviour by differential scanning calorimetric. Antioxidant effect of NPs was determined by chelating activity of iron ions. The cell viability of mesenchymal stem cells was determined by 3‐[4, 5‐dimethylthiazol‐2‐yl]‐2, 5‐diphenyl tetrazolium bromide assay and the calcification of osteoblasts was studied by Alizarin red staining. The optimised NPs showed particle size of 176 nm, zeta potential of −20.8 mV, loading efficiency of 93.3% and RE24 % of 80.6%. The chatechin loaded chondroitin sulphate NPs showed 70‐fold more antioxidant activity, 3‐fold proliferation effect and higher calcium precipitation in osteoblasts than free catechin. [ABSTRACT FROM AUTHOR]

With the use of glauberite mineral (GM) and sodium hydroxide (SH) alkaline catalysts to stimulate slag powder's internal cementation activity and incorporate the two fine-grained solid wastes, such as quicklime (Q) and desulfurized ash (DA), a new cementitious material suitable for mine tailings was developed to replace traditional ordinary Portland cement (OPC) for reducing cement-related costs. A series of uniaxial compressive strength (UCS) tests were carried out on cemented tailings backfill (CTB) samples containing different activators. The results showed that (1) the highest UCS values of 14-day and 28-day cured CTB samples were 1.259 MPa and 2.429 MPa, respectively, and the effect of different activator types was in the order of SH > GM > DA > Q and SH > GM > Q > DA; (2) the relationship between UCS and activator dosages followed the function y = ax3 − bx2 + cx − d. Compared with the OPC 32.5 R cemented samples, the minimum strength growth factor was 1.45, and the maximum reached 2.03; (3) the optimal proportion of DA slag formula was 4.5% or 5.0% Q, 19% DA, 2.5% GM, and 0.7% SH. The aforesaid new cementitious materials met the mine's UCS requirements with a relatively low cost (17.04–17.20 €/ton) and solved the stacking problem of solid wastes on the surface well. Ultimately, this study provides a useful reference for the development of mineral binders. [ABSTRACT FROM AUTHOR]

Geopolymer concrete is an inorganic polymer composite which has the potential to build an eco‐friendly and sustainable construction by replacing the existing conventional concrete. Herein, cement is totally replaced by mineral admixtures rich in aluminosilicates such as fly ash and is formed by the alkali activation using alkaline activator solutions, such as sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). Fly ash, a waste material from industry, can be incorporated in the manufacture of geopolymer concrete. The replacement of cement by fly ash in geopolymer concrete reduces the huge energy consumption and restricts carbon dioxide emission to the atmosphere during its production. In this paper, experimental investigations have been carried out involving the variation of total aggregate content (viz., 74, 76, 78, 80, and 82%), NaOH concentration (8, 10, 12, and 14 M), and curing temperature (60, 70, 80, 90, and 100°C) on the strength of geopolymer concrete by keeping a constant alkaline liquid to fly ash ratio of 0.45 and a 24‐hour rest period. It is concluded that 76% of total aggregate content is suitable for producing geopolymer concrete without hindering the workability. Further, strength of geopolymer concrete has been found to be increased at 90°C having 12 M NaOH concentration. [ABSTRACT FROM AUTHOR]

ABSTRACT: Polyurethane/water glass (PU/WG) grouting materials were prepared in presence of different proportions of catalyst. The effects of catalyst on the mechanical properties, thermal properties, and chemical cross‐sectional morphologies of the grouting materials were also investigated. Catalyst addition can significantly increase the chemical reaction rate, reduce the gel time and curing time, and improve the thermal stability of PU/WG grouting materials. It was found that the grouting material containing 0.1 wt % BDMA + 0.1 wt % DBTDL demonstrated high fluidity, short curing time, and high early‐stage and late‐stage (up to 66.1 MPa) compression strengths. However, when the content of the added catalyst was equal to 0.5 wt %, fine cracks were formed in the material structure accompanied by the detachment of spherical particles from the PU matrix, which significantly deteriorated its mechanical properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46460. [ABSTRACT FROM AUTHOR]