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To balance cost and performance of geopolymers, alkalinity of activating solution is critical. Alkalinity affects condensation that determines the final gel structures, but this effect is confounded by dissolution and is not understood from direct experimental evidence. In this study, we investigated effects of alkalinity on condensation for gels synthesized via a sol–gel method that eliminates dissolution process. As alkalinity increased, particle sizes of the gels increased as indicated by SEM, Si/Al ratios of the gels decreased but polymerization extent increased as supported by FTIR, 27Al and 23Na NMR, and composition analysis. The mechanism for the effects of alkalinity was proposed accordingly: (1) increasing alkalinity lowers the Si/Al ratio (i.e., more incorporation of Al) of the resulting products probably by affecting charging conditions of the Si and Al units; (2) the presence of Al(OH)4− units promotes their condensation with nearby species to increase the extent of polymerization; (3) enhanced condensation increases particle sizes of the gels even at microstructural level. This understanding on condensation independent of dissolution provides ways to control gel structures and Si/Al ratios and thus tailor properties accordingly, as well as to suggest a strategy (by altering Si/Al ratios during condensation) to develop kinetics-controlling admixtures.

Thunderstorm overshooting is rare but not an unusual phenomenon in a metropolitan of India, Kolkata (22.57° N; 88.36° E) during the pre-monsoon months (April–May). An attempt is made in this study to identify the important parameters differentiating the thunderstorms in overshooting and non-overshooting categories through data analytics from 2000 to 2015. The present investigation on parametric classification would facilitate in estimating the predictability of thunderstorms with overshooting which subsequently might assist in operational forecast of thunderstorm severity over Kolkata. The altitudes of lifting condensation level (LCL), wind shear, bulk Richardson number (BRN), gust speed, boundary layer characteristics and their correlation with thunderstorm cloud top height (CTH) and also their variation and distribution during overshooting (OTS) and non-overshooting (TS) thunderstorms are analyzed in this study. The result depicts that over Kolkata the intensity of storms during OTS is higher than during TS though the frequency of OTS is less than that of TS. The results further show that the potential temperature (θ), equivalent potential temperature (θe), mixing ratio (es) in the boundary layer, convective available potential energy, convective inhibition energy, BRN and gust speed play significant roles in regulating the CTH during OTS and TS thunderstorms over Kolkata.

The influence of temperature (T), potential temperature (⊖), vertical velocity (ω), specific humidity (q), geopotential height (hgt), zonal wind (ZW), total cloud cover (TCC), momentum flux (mf), latent heat flux (lhf), tropopause height, and kinetic energy of wind (KE) at various pressure levels from 1000 to 10 hPa on the variability in summer monsoon rainfall (SMR) over Gangetic West Bengal (GWB) (21.5° N–24.5° N; 86° E–89° E), India is explored in this research with NCEP reanalysis data set during the period from 1986 to 2016. The said period has been divided into three categories: excess rainfall years (ERY), normal rainfall years (NRY), and deficit rainfall years (DRY) based on the percentage rainfall anomaly over GWB. The principal component analysis (PCA) has been implemented with the evaluation of eigenvectors and correlation coefficients to extract the significant parameters from the original data set. The result shows slight decrease in rainfall and its anomaly over GWB during the summer monsoon (SM) season (JJAS) from 1986 to 2016, which is statistically insignificant. However, the rainfall is observed to be maximum for all the categories in the month of July with decreasing trend until September, whereas the rainfall is minimum in the month of June. The study shows slight cooling in tropospheric temperature than the climatology during ERY compared with NRY and DRY. It is observed that the availability of tropospheric moisture is more during ERY and is much less during DRY. The descending motion during DRY is found to lead subsidence and thus increase in surface temperature. The weak upper level wind during DRY leads to the reduction in moisture advection. The geopotential height is observed to descend during DRY making the level colder, whereas it goes up for NRY and ERY generating warmth in the upper level. The cold anomaly at upper level pulls down the tropopause height during DRY, whereas the warm anomaly during ERY and NRY pushes it up. The total cloud cover anomaly is observed to be positive during ERY and NRY with higher value for ERY and negative anomaly during DRY.

Synthesis of cyclic carbonates via CO2 cycloaddition reaction with epoxides is one of the promising strategies to valorize greenhouse gas CO2, thereby fixing it to the value-added chemicals. In this study, uniform copper oxide nanoparticles (Cu2O, Cu4O3) with variable oxidation states are stabilized by functionalized covalent organic frameworks (COF) and effectively utilized as a catalyst for the synthesis of cyclic carbonates under ambient temperature and atmospheric pressure. Characterization techniques e.g. powdered X-ray Diffraction (PXRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FT-IR) and nitrogen physisorption (BET) coupled with DFT studies predict that the copper oxide nanoparticles are anchored on the mesochannels of covalent organic frameworks through a covalent-coordinate linkage. The catalyst exhibits significantly high turn over numbers (TON, order of 105) and more than 99% selectivity towards synthesis of cyclic carbonates with exceptional recyclability.

Two different Coagulase negative staphylococcal environmental isolates BP/SU1(Staphylococcus epidermidis; MTCC accession number:9538) and BP/SU2 (Staphylococcus haemolyticus; MTCC accession number:5731) show a tendency to propagate in the biofilm mode specially on low surface energy mediums. In this study we have co-related the biofilm formation of the two species on polystyrene tissue culture plates with the quantity of utilizable sugar present in the culture medium. The dispersal of the same biofilms with common dispersing agents like NaIO4, DNase, and proteolytic enzymes has also been studied. Results indicate that though polysaccharides undoubtedly enhance the biofilm formation for both the species, their role as biofilm - material adhesive agents are minimal for these two strains.

Type K cement offers a lower slump than conventional concrete, even at a higher water-to-cement ratio. Therefore, a suitable chemical admixture should be added to the Type K concrete mix design at a feasible dosage to achieve and retain target slump. In this project, a compatibility study was performed for Type K concrete with commercially available water-reducing and air-entraining admixtures. Slump and air content losses were measured over a period of 60 minutes after mixing and a particular mid-range water-reducing admixture was found to retain slump effectively. Furthermore, no significant difference in admixture interaction between conventional and Type K concrete was observed. Another concern regarding the use of Type K concrete is that its higher water-to-cement ratio can potentially lead to higher permeability and durability issues. This study also explored the effectiveness of presoaked lightweight aggregates in providing extra water for Type K hydration without increasing the water-to-cement ratio. Permeability of concrete was measured to validate that the use of presoaked lightweight aggregates can lower water adsorption in Type K concrete, enhancing its durability. Extensive data analysis was performed to link the small-scale material test results with a structural test performed at Saint Louis University. A consistent relation was established in most cases, validating the effectiveness of both testing methods in understanding the performance of proposed shrinkage-mitigation strategies. Stress analysis was performed to rank the mitigation strategies. Type K incorporation is reported to be the most effective method for shrinkage-related crack mitigation among the mixes tested in this study. The second-best choice is the use of Type K in combination with either presoaked lightweight aggregates or shrinkage-reducing admixtures. All mitigation strategies tested in this work were proved to be significantly better than using no mitigation strategy.

Understanding the effects of silicate concentration of activator solution is critical for developing cost effective geopolymeric binders, and controlling their setting and hardening behavior. However, in calcium containing geopolymers, effects of silicate concentration of activator solution on the amount and nature of reaction products at different ages are still unclear. In this study, we examined class F fly ash and slag binders activated by both silicate and hydroxide solutions. Faster hardening from ultrasonic wave reflection and faster reaction from calorimetry were seen in the binder activated by silicates than that by hydroxides. Subtraction of infrared spectra, aided by selective chemical treatments, indicated the main reaction peak in calorimetry curves correlates with formation of calcium silicate hydrate/calcium aluminosilicate hydrate (C-S-H/C-A-S-H) of the same Ca/Si ratio in the hydroxide activated binder but formation of both C-S-H gel and potassium aluminosilicate hydrate (K-A-S-H) gel in the silicate activated binder. In additional tests, the main reaction peak of the silicate activated binder was delayed as silicates in the activator solution became less polymerized, further confirming contribution of K-A-S-H formation towards the main heat peak in calorimetry curve. Scanning electron micrographs showed products grew from surface into pore space in the hydroxide activated binder but within interstitial space in the silicate activated binder.

The aim of this study is to examine the skill of climate forecast system version 2 (CFSv2) in simulating the synoptic features of Bay of Bengal (BOB) branch of summer monsoon (SM) during the onset over Gangetic West Bengal (GWB), India. Precise prediction of the onset time and the synoptic features associated with the onset is a major challenge in SM study. Better understanding of the synoptic and intra-seasonal variability during the propagation along with the mean simulation of monsoon features is crucial, especially for the operational models. The earlier studies focused mainly on the mean simulation of SM during June–September (JJAS) period. However, the main objective of the present study is to improve the understanding of CFSv2 model biases in simulating the synoptic features during the propagation of BOB branch of SM system till the onset over GWB. The skill of the coupled model is estimated for the years 2011 to 2015 with tropospheric temperature (TT), sea surface temperature (SST), mean sea level pressure (MSLP), winds at 850 and 500 hPa pressure levels, and rainfall rate (RR). The result shows that the observed characteristics are simulated, reasonably well, by CFSv2 model with quite high reliability unlike other coupled models. The CFSv2 has been able to simulate the position/variation during the onset; however, the model has not been able to estimate the intensity in some occasions. The gradients of pressure and SST have been slightly overestimated by the model. The model has not been able to simulate the winds at 850 and 500 hPa pressure levels in some occasions. The CFSv2 model in simulating the features during propagation of BOB branch of SM system shows disparity from observation in some occasions during 2011 to 2015. The result also reveals that the model biases remain unaltered during El Nino episode of 2011.

A polystyrene functionalized Zinc anthranilic acid complex catalyst has been prepared. The PS-Zn-anthra complex has been characterized by EDX, Scanning electron micrographs (FE-SEM), FTIR spectra, UV–vis spectra and thermogravimetric analyses. A greener and novel methodology was considered for the production of dicoumarol derivatives utilizing PS-Zn-anthra complex as a Lewis acid catalyst, non-toxic, mild in H2O employing heteroaromatic/aromatic aldehydes and 4-hydroxycoumarin. The catalyst also shows good catalytic activity in the cyclo addition of CO2 to epoxide. The results of activity of catalyst imply that the procedure adopted provides numerous advantages such as low loading of catalyst, operational simplicity, mild reaction conditions, quantitative yields, and short reaction time. The PS-Zn-anthra complex exhibited the elevated efficiency of recycling in these reactions. This catalyst can be recycled for five times without appreciable loss of its activity.

The regional features of Bay of Bengal (BOB) branch of summer monsoon (SM) are examined to identify the causes of delayed onset over Gangetic West Bengal (GWB) in the years having normal onset over Kerala coast. The normal onset over both GWB and Kerala is designated as Normal–Normal (NN) years, while delayed onset over GWB and normal onset over Kerala is termed Normal–Delayed (ND) years. The temperature gradient (TTg), winds at 850 and 150 hPa pressure levels, sea-surface temperature (SST), outgoing long wave radiation (OLR), low-level moisture convergence, instability, and rainfall rate (RR) are analyzed in this study using National Centers for Environmental Prediction and National Oceanic and Atmospheric Administration reanalysis dataset during the period from 1981 to 2015. The result shows that TTg over BOB plays a significant role in controlling the movement of BOB branch of SM. Warm SST is observed to prevail over north BOB during NN years. The divergence at 150 hPa and convergence at 850 hPa pressure levels are found to influence the propagation of BOB branch of SM during both NN and ND years. The winds at 850 hPa level converge over BOB and GWB during NN years, whereas winds converge more over eastern BOB and Indo-Chinese peninsula during ND years. Result depicts abundance of low-level (850–1000 hPa) moisture over eastern BOB and Indo-Chinese peninsula during ND years, whereas moisture is observed to converge over north and north-eastern BOB during NN years. The RR is observed to be slightly higher during NN than ND years. However, it may not be concluded from the analysis that delayed onset over GWB will be responsible for less RR over the study region.

Structure-property relationships of alkali-activated aluminosilicate gels are studied using rheology, neutron scattering, solid-state NMR, and TEM to develop a pseudo-ternary state diagram. Empirical gel states are classified by the rheological behavior (sol-gel transition and scaling of storage modulus with aluminum concentration). The state boundaries are compared to alkali-activated materials from the literature including denser binders. This work focuses on two compositions of dilute gels, formulated to specifically quantify the effects of pH and aluminum concentration on gel microstructure and rheology. Gels formulated at constant pH of 12.5 show a change in morphology and silicon coordination, but consistent mass fractal dimension as aluminum concentration is increased. This microstructural behavior contrasts the characterization of gels previously formulated with a variable pH (range 3–11) which is dependent on aluminum concentration. These results inform the complicated interactions in the polycondensation reaction of alkali-activated binders and lead to a state diagram which unifies many structure-property observations reported for these materials.

Oleic acid and oleylamine capped 3-D porous CeO2 nanocubes were synthesized by the hot injection method. The surface of the nanocube was modified with 2,4-dimethylphenol (DMP). The reducing and capping abilities of DMP to form Ag nanoparticles were explored to form noble metal nanoparticles over the porous CeO2 nanocubes support at room temperature. The surface modification and formation of Ag nanoparticles over the CeO2 support were thoroughly characterized with FTIR, UV-Vis spectroscopy, XRD, XPS, TEM, HRTEM, STEM, EDX and chemical mapping. This CeO2–Ag nanocomposite was found to have enhanced catalytic activities in the ‘click reaction’ as compared to unsupported Ag nanoparticles and porous CeO2 nanocubes; it was also found to have optimized catalytic activity in the carboxylation of terminal alkynes when Cs2CO3 was used as the base in DMF solvent at 80 °C. The reaction can give the desired product in yields as high as 98% under several experimental conditions via the green pathway. Recycling data showed that the catalyst could be reused five times without considerable loss of its activity and without any deterioration of physical conditions as observed by various characterization methods like TEM, EDX, XRD and XPS.

An efficient and recyclable catalytic system composed of palladium nanoparticles embedded over mesoporous TiO2 material (Pd@MTiO2) has been synthesized and its catalytic activity has been explored in Suzuki-Miyaura cross-coupling reaction of aryl halides in water medium. This catalytic system is a very simple and highly active protocol for carrying out the Suzuki coupling of aryl bromide and aryl chloride with boronic acids, which proceed smoothly in excellent yields under mild reaction conditions. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), and N2 sorption studies are used to characterize the Pd@MTiO2 material. Environmentally friendly reaction conditions, high product yield, tolerance of variety of functionalities in the reactants and reusability suggested future potential of Pd@MTiO2 for the synthesis of a wide range of biaryl compounds.

Layered 2D organic–inorganic hybrid perovskite (OIHS) of the diammonium series, 1,5 di-aminepentane tetrachloro mangenate ([NH3–(CH2)5–NH3] MnCl4) was prepared by slow evaporation and reducing temperature method and characterized by single crystal X-ray diffraction analysis. Its structure consists of organic cation, [NH3(CH2)5NH3]+2 extended in a zigzag fashion and inorganic anion, [MnCl6]−2 where Mn2+ is coordinated by six Cl− ion in octahedral fashion. The organic and inorganic segments are alternately stacked along c-axis where inorganic layer is extended through corner-shared octahedra sandwiched by the di-aminopentane molecules. The layers (organic and inorganic) were connected to each other through N–H···Cl hydrogen bonds and van-der Waals interaction to build cation–anion–cation cohesion. The hybrid crystal had orthorhombic non-centrosymetric system having I212121 space group with unit cell parameters a = 7.1742(3) A, b = 7.3817(3) A, c = 23.9650(10) A, V = 1269.13 A3 and Z = 4. The hybrid exhibited excellent catalytic activity towards sulphide and alkene oxidation using aqueous H2O2 as an oxidant. OIHS of the diammonium series [NH3–(CH2)5–NH3] MnCl4; 1,5 di-aminepentane tetrachloro mangenate were prepared by slow evaporation and temperature decrease method, characterized by single crystal X-ray diffraction. This complex exhibits excellent catalytic activity towards sulphide oxidation and alkene oxidation using aqueous H2O2 as an oxidant.

The paper provides a closer perspective on the series of discriminatory practices that affect both the infertile woman battling reproductive failures as well as the fertile surrogate who gestates on her behalf. It would bring out concerns on the persistence of stigma in the altruistic form of surrogacy, on the conceptual dimensions of stigma operating in what I call a surrogacy-space and most importantly on the law’s positionality in divesting (or not) the stigma entrenched in Indian surrogacy.

It is widely known that presoaked lightweight aggregate (LWA) is greatly beneficial for reducing autogenous shrinkage by providing additional water reservoirs for the mixture. However, in u...

Understanding the effects of nucleation seeds on reaction kinetics and microstructures of alkali activated binders (AABs) is important since it will help us control both early-age and long-term properties. For example, in the calcium-containing AABs, calcium silicate hydrate/calcium aluminosilicate hydrate (C-S-H/C-A-S-H) seeds have been proposed by others to act as nucleation sites to promote formation of geopolymer gel. In this study, we examined the nucleation effects by adding synthesized C-S-H and C-A-S-H seeds into class F fly ash-slag mixes activated both by potassium hydroxide and by potassium silicate solutions. From both calorimetry and ultrasonic wave reflection tests, we found seeding to accelerate reaction of the hydroxide activated binder but decelerate that of the silicate activated binder. Based on further chemical treatments and Fourier-transform infrared spectroscopic characterization, we found the acceleration in the hydroxide binder was due to enhanced formation of C-S-H/C-A-S-H, while the deceleration in the silicate binder was due to decreased formation of K-A-S-H gel despite the enhanced formation of C-S-H/C-A-S-H. Additionally, in both types of binders, we found dissolution of fly ash precursor was enhanced. Evidence in this study suggests that C-S-H seeds act as nucleation sites for further precipitation of C-S-H/C-A-S-H but not for formation of geopolymer gel.

Heavy freight or high speed rail operations cause dynamic aggressive environments for structural materials in a railway system, resulting in higher wear and degradation rate of traditional brittle cementitious materials. As such, the improvement in fundamental dynamic properties of the material is crucial. In this study, the focus is placed on the development of a concrete damping enhancement using crumb rubber, which has significant potential to mitigate pressing issues in modern railway industry such as railseat abrasion and impact damages in concrete sleepers, thermal expansion crack of track slabs, and so on. Also indirectly, the utilization of crumb rubber will enhance the recycling options of rubber tire wastes, which are not biodegradable. This paper will focus only on the early-age dynamic moduli of the engineered concrete using modal excitation technique. The comparative study to evaluate the influence of crumb rubber participles highlights vital changes in dynamic elasticity and damping coeffici...

CO2 fixation reactions are very demanding both from the perspective of mitigation of greenhouse gases as well as the successful utilization of this abundant C1 source. An efficient and recyclable catalytic system based on palladium nanoparticles embedded on mesoporous TiO2 (Pd@MTiO2) has been developed and it is explored as a heterogeneous catalyst for the synthesis of cyclic carbonates from the respective epoxides and CO2 under atmospheric pressure and at room temperature. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), ultraviolet-visible absorption spectra (UV-vis), X-ray photoelectron spectroscopy (XPS) and N2 sorption studies are used to characterize this Pd@MTiO2 material. Moreover, the catalytic reaction is green as the reaction involves the consumption of greenhouse gas CO2 and the reaction proceeds smoothly without any need for a solvent. High catalytic activity, ease of catalyst recovery from the reaction mixture and excellent recycling efficiency without any significant loss in catalytic performance suggested an environmentally benign catalytic pathway for the synthesis of cyclic carbonates over this Pd-nanocatalyst.

Due to an increasing amount of waste tires produced yearly, environmental concerns arise as waste tires in landfills pose both a fire hazard, and a habitat for rodents and mosquitos. As a result, the reuse of waste tires in the form of waste rubber in concrete has been attempted. Previous research work has shown that the inclusion of waste rubber in concrete results in a drastic decrease in compressive strength. The limitations regarding the use of rubberized concrete are related to the interfacial transition zone between rubber and paste. Due to mismatch in free surface energy between rubber and cement paste, an interfacial gap is often reported to be present. This investigation aims to determine the effect of expansive cement, specifically calcium sulfoaluminate cement (CSA), has on the performance on rubberized cement samples, and its effect on the interfacial transition zone. A comprehensive experimental plan was carried out including pullout and compressive tests, scanning electron microscopy (SEM) imaging of fractured surface, and non-destructive tests through resonant frequency and dynamic mechanical analysis (DMA); furthermore, a temperature sweep via DMA was done to determine damping factor as a function of temperature. Results from compressive strength indicate a marked increase in the performance of rubberized samples with expansive cement. Pullout results, dynamic modulus and damping ratio values, shrinkage measurements, and scanning electron microscopy (SEM) imaging validate the hypothesis that a decreased interfacial gap at the rubber-paste interface obtained from using expansive cement results in increased mechanical performance.

Shrinkage cracking in concrete is a widespread problem, especially in concrete structures with high surface-to-volume ratio such as bridge decks. Expansive cements based on calcium sulfoaluminate phase were developed to mitigate the shrinkage cracking of concrete. The compressive stress induced due to restrained expansion of concrete has been shown to counteract the tensile stress generated during drying shrinkage. This research attempts to address the differential behavior of fly ash type (i.e., Class C vs. Class F) on early-age expansion and hydration characteristics of ordinary Portland cement (OPC)–calcium sulfoaluminate (CSA) cement blend. It was observed earlier that the presence of Class C fly ash (CFA), unlike Class F fly ash, shortened the expansion duration of OPC–CSA cement blend, which was hypothesized to be correlated to early depletion of gypsum. This paper presents a detailed verification of the hypothesis. Addition of external gypsum to OPC–CSA–CFA blend led to simultaneous increase in expansion and disappearance of a shoulder peak in the calorimetric curve. Thermodynamic calculations using a geochemical modeling program (GEMS-PSI) revealed higher saturation levels of ettringite in presence of external gypsum, which led to higher crystallization stress, and thereby increased expansion.

The present study aims at examining the physico-chemical factors influencing the expansion characteristics of OPC–CSA blend in the presence of mineral admixtures. Three different admixtures: Class ‘F’ fly ash (‘F’FA), Class ‘C’ fly ash (‘C’FA) and silica fume (SF) were used as 15%, 15% and 5% replacement of total cementitious binder. Longitudinal expansion of cement pastes prepared at w/cm – 0.44 showed that the Class ‘F’FA increased the expansion whereas the Class ‘C’FA and SF reduced the expansion. The pore solution of the OPC–CSA cement pastes was extracted at different ages to monitor the concentration of various ionic species. The saturation level of ettringite was determined using a geochemical modeling program (GEMS). Furthermore, an upper bound of crystallization stress was estimated. The expansion behavior in the presence of Class ‘F’FA and SF was found to be influenced by the changes in the stiffness, whereas the expansion of the Class ‘C’FA-based mixture was governed by faster hydration of ye'elimite.

Calcium sulfoaluminate (CSA) cements have been shown to have lower carbon footprint than that of Portland cement. In addition, the expansive nature of CSA-based cement can be utilized to enhance the resistance against shrinkage cracking by inducing compressive stress in concrete. The current paper reports the hydration and early-age volume changes of three OPC-CSA binary cement systems with varying CSA content. Hydration and phase development was monitored through calorimetry and quantitative X-ray diffraction. Expansion characteristics of OPC-CSA blends were monitored in saturated lime water. A geochemical modeling program (GEMS-PSI) was used to estimate the saturation levels of ettringite which had strong correlation with 1 day-expansion. The volume fraction of ettringite in a given pore volume was found to have a stronger correlation with expansion of OPC-CSA blends than the ettringite content. Furthermore, a poromechanical model was used for estimating the tensile stress in OPC-CSA blends.

Calcium sulfoaluminate (CSA) cements have lower carbon footprint than that of portland cement, which makes them a suitable alternative as a sustainable cementitious binder. Early-age expansion of CSA cements can be exploited to induce compressive stress in restrained concrete which can later counteract tensile stress developed during drying shrinkage, thus enhancing the resistance against shrinkage cracking. However, a proper understanding of the expansion behavior is critical to eliminate any risk related to expansion-induced cracking. This study examines the expansion and hydration characteristics of various ordinary portland cement (OPC)-CSA blends. Early-age expansion of paste samples was monitored. The increase in CSA cement content increased the extent of expansion. Samples having the highest CSA content (30% by mass) exhibited excessive expansion which led to their cracking. Quantitative X-ray diffraction, pore solution extraction, porosity, tensile strength, and dynamic modulus tests were performed to monitor the physico-chemical changes in OPC-CSA blends. It was shown that the ettringite supersaturation in the investigated systems gave rise to the crystallization stress, responsible for the expansion. Thermodynamic models enabled a reasonable prediction of tensile failure, particularly in the blends with the higher CSA content.

Alkali activation of a fly ash and slag mixture supposedly forms a combination of aluminosilicate and calcium silicate hydrate gel as reaction products. Fourier transform infrared spectroscopy (FTIR) is often used to characterize the complex nature of the reaction products. However, interpretation of FTIR results is difficult as the Si–O–T (T = Al, Si) vibrations from the initial ash, geopolymer product, unreacted slag, and calcium silicate hydrate yield an overlapping spectrum. This paper reports how the issue can be resolved by selectively dissolving calcium silicate hydrate and geopolymer product, and subtracting FTIR spectra of the insoluble residue from the original material to determine IR spectrum of the material dissolved.

An accelerated carbonation test (at 5 % CO2, 22 °C and 55 % RH) was carried out on bulk and powdered cement paste samples incorporating two different supplementary cementitious materials: microsilica and nanosilica. Extensive characterization using thermogravimetric analysis, scanning electron microscopy with X-ray microanalysis, and image analysis was performed at various degrees of carbonation, to study the fundamental effects of nanosilica on carbonation of main hydration products, calcium hydroxide (CH) and calcium silicate hydrate (C–S–H). Results at every stage were compared with the effects of microsilica addition to cement paste. Results suggested that incorporation of small amounts of micro or nanosilica can decrease the total carbonation of cement paste. In particular, nanosilica could reduce carbonation (decalcification) of C–S–H and the depth of carbonation significantly.

Fiber reinforcements provide many benefits to cementitious composites, including reduction of crack widths and increases in ductility. However, the interfacial transition zone between fibers and hydrated cement can contain a high proportion of calcium hydroxide and porosity. With their high moduli of elasticity, carbon nanotubes and carbon fibers could provide substantial mechanical reinforcement at multiple length scales, but only if their bond to the matrix can be controlled. Surface treatments of fibers and addition of supplemental materials in the matrix can influence both the mechanical interaction at the interface and the dispersion of these relatively small reinforcements. We performed a broad study of Portland cement mortar mixtures containing silica fume, plain or silica-functionalized carbon nanotubes, and carbon fibers to characterize changes in fracture properties. The early age hydration kinetics of cement pastes containing carbon nanotubes were compared using isothermal calorimetry. Early age fracture surfaces of cement pastes containing carbon fibers were observed using a scanning electron microscope. The notched beam test method of the Two Parameter Fracture Model was used to determine the fracture properties of each mix. We observed that silica fume and silica functional groups improved the fracture performance of mixtures containing carbon nanotubes and carbon fibers. Further optimization of dosage, size, and interface strength is required to fully utilize carbon nanotubes in cementitious composites.

An efficient and recyclable catalytic system composed of palladium nanoparticles embedded over mesoporous TiO

The degradation of hydration products of cement is known to cause changes in the micro- and nano-structure, which ultimately drive thermo-mechanical degradation of cement-based composite materials at elevated temperatures. However, a detailed characterization of these changes is still incomplete. This paper presents results of an extensive experimental study carried out to investigate micro- and nano-structural changes that occur due to exposure of cement paste to high temperatures. Following heat treatment of cement paste up to 1000 °C, damage states were studied by compressive strength test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) atomic force microscopy (AFM) and AFM image analysis. Using experimental results and research from existing literature, new degradation processes that drive the loss of mechanical properties of cement paste are proposed. The development of micro-cracks at the interface between unhydrated cement particles and paste matrix, a change in C–S–H nano-structure and shrinkage of C–S–H, are considered as important factors that cause the thermal degradation of cement paste.

A new furfural functionalized polymer-amine grafted with copper catalyst has been designed and employed for the N -arylation, O-arylation and S-arylation reactions under an open air condition to afford the corresponding coupled products in good to excellent yields. This solid supported catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), UV–vis spectroscopy and scanning electron microscope (SEM). The developed catalyst can be facilely recovered and reused five times without significant decrease in activity and selectivity. This result confirms that the polymer anchored complex was not leached during the reaction, suggesting the true heterogeneous nature of the catalyst.

Silver nanoparticles (Ag-NPs) have been finely dispersed at the mesoporous organic polymer via post-synthetic chemical grafting over mesoporous poly-triallylamine (MPTA-1). The resulting Ag-MPTA-1 nanomaterial has been characterized by elemental analysis, powder x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA), EPR spectroscopy and AAS elemental analysis. The Ag-MPTA-1 acts as an efficient heterogeneous nanocatalyst in the reduction of substituted nitrobenzenes via transfer hydrogenation. The material also showed excellent catalytic activity in one-step catalytic oxidative esterification of primary alcohols using molecular oxygen as a green oxidant. The catalyst is air-stable, inexpensive, easy to prepare and reused several times without significant decrease in activity and selectivity.

A nitrogen rich porous covalent imine network material (CIN-1) has been successfully employed for grafting silver nanoparticles (Ag NPs). The Ag NPs grafted CIN-1, Ag-CIN-1 has been characterized by elemental analysis, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA) and EPR spectroscopic studies. Ag-CIN-1 acts as a truly heterogeneous catalyst in the hydration of nitriles to amides and the A3 coupling reactions between the alkyne, amine and aldehyde to produce propargylamines by using water as a green solvent.

A new ruthenium-grafted mesoporous organic polymer Ru-MPTAT-1 has been synthesized via simple and facile in situ radical polymerization of 2,4,6-triallyloxy-1,3,5-triazine (TAT) in aqueous medium in the presence of an anionic surfactant (sodium dodecyl sulfate) as a template, followed by grafting of Ru(II) onto its surface. Ru-MPTAT-1 has been characterized by elemental analysis, powder XRD, HRTEM, FT-IR, UV-vis DRS, TG-DTA, FESEM and XPS characterization tools. The Ru-MPTAT-1 material showed very good catalytic activity in the Suzuki-Miyaura cross-coupling reaction for aryl halides and transfer hydrogenation reaction for a series of carbonyl compounds. The catalyst is easily recoverable from the reaction mixture and can be reused several times without appreciable loss of catalytic activity in the above reactions. Highly dispersed and strongly bound Ru(II) sites at the mesoporous polymer surface could be responsible for the observed high activity of the Ru-MPTAT-1 catalyst in these reactions.

Palladium nanoparticles (Pd NPs) have been grafted at the surfaces of a Co-containing metal–organic framework material MCoS-1. The Pd NPs grafted material Pd(0)/MCoS-1 has been characterized by HR TEM, XPS and EPR spectroscopic analyses. Pd(0)/MCoS-1 showed excellent catalytic activities in Suzuki–Miyaura cross-coupling reaction for the synthesis of a diverse range of biaryl organics in water. Sonogashira cross-coupling between terminal alkynes and aryl halides has also been carried out over this Pd-nanocatalyst in water without the addition of any Cu co-catalyst. In both reactions the catalyst is easily recoverable and can be reused for several times without appreciable loss of catalytic activity. No evidence of the leaching of Pd from the catalyst during the course of reaction has been observed, suggesting true heterogeneity in our catalytic systems.

A new Schiff base oriented Co(III) complex, (CoL)Cl 4H2O (L = Schiff base), has been synthesized by careful design of the Schiff base ligand thorough oxidation of Co(II) to Co(III) during the reaction process. The complex has been characterized by single-crystal X-ray structure analysis and various spectral analyses. Structure analysis reveals that this monomeric complex crystallizes in triclinic P−1 space group. Supramolecular hydrogen bonding interactions among the guest water molecules and counter anion chloride leads to the formation of 1D water-chloride chain. A polymer anchored heterogeneous cobalt complex has been synthesized, characterized by various physicochemical techniques and successfully used for the oxidation of alkenes and sulfides using H2O2 as oxygen source. The influence of the various reaction parameters has been studied. The heterogeneous cobalt complex can be reused seven times without any significant loss in its catalytic activity.

A C–S–H series with calcium–silicon ratio 0.6–3.0 was synthesized by pozzolanic reaction. Phase composition, nanostructural and morphological characteristics were determined using XRD, XRF, SEM and 29Si NMR. Most of the samples were phase-pure, poorly crystalline C–S–H. Significant changes in the nanostructure of the C–S–H samples were observed when the calcium–silicon ratio reached values of 0.8, 1.0 and 1.5. At calcium–silicon ratio 0.8 the basal XRD peak began to develop, crosslinking between layers was seen below this ratio but not above, and there was a substantial decrease in mean silica chain length at this ratio. At calcium–silicon ratio 1.0 there was a pronounced microstructural change from granular to reticular and another substantial decrease in mean chain length (indicated by an abrupt increase in the Q1 peak intensity and decrease in the Q2 peak intensity). At calcium–silicon ratio 1.5 the basal XRD peak began to diminish again, the mean silica chain length decreased further, and isolated tetrahedra (Q0) were observed.

An eco-friendly, cheap and reusable polymer-anchored iron(III)-ferrocene Schiff base catalyst has been designed for the efficient oxidation of alkanes and alcohols. Oxidation reactions were done by using a greener oxidant 30 % aqueous hydrogen peroxide in acetonitrile medium at room temperature for alcohols and at 60 °C for alkanes. Both the alkanes and alcohols have been selectively oxidized to their corresponding aldehydes and ketones in excellent yields. This catalyst has shown excellent catalytic activity with high selectivity and recyclability. It is found that this catalyst can be reused up to six cycles without loss of its original activities.

This paper presents the microstructural development and hardening rate of fly ash-slag geopolymers. The solid precursors are treated with a potassium hydroxide-silicate activator of modulus 1.25. Ultrasonic wave reflection and Proctor penetration methods are used to determine the rate of hardening. Microstructural development is investigated using SEM-EDS, and the reaction rate is monitored using semi-adiabatic calorimetry. Both UWR and Proctor penetration methods capture changes in the hardening rate due to changes in the reaction mechanism. An increase in the rate of hardening is observed with the addition of slag. It is concluded that the calcium that dissolves from slag significantly influences both early and late age properties, and the availability of free calcium ions seems to prolong fly ash dissolution and enhance geopolymer gel formation. It is proposed that the hardening process is initiated by the precipitation of C-A-S-H and that rapid hardening continues due to accelerated geopolymerization.