Acceleration Period Research Articles

Effects of chloride content on early hydration performance of cement pastes

In this paper, the effect of chloride ion content, ranging from 0% to 5%, on the early hydration performance of cement pastes was comprehensively investigated using isothermal calorimetry, low-field NMR, resistivity, and rheological tests. The results show that the hydration is accelerated, and the hydration peak is continuously advanced by increasing the chloride content from 0.5% to 2%. However, chloride content of 5% initially has an inhibitory effect, but after 19 h, it has an accelerating effect. The T2 spectrum exhibits a noticeable shift from 10 to 100 ms toward the range of 1–10 ms during the acceleration period, and the changing tendency of relative signal intensity (RSI) is consistent with the heat of hydration. The results of low-field NMR provide an explanation for the variation of early strength of mortars containing chloride. The effect of chloride ions on resistivity appears after mixing. The resistivity of chloride-containing pastes should be controlled by hydration and free chloride ions in the pore solution. Besides, the rheological properties are also affected by the chloride ion admixture and hydration process. The flowability is reduced with 0.5% and 1% Cl- but improved with 2% and 5% Cl-. The results provide a comprehensive characterization of the effect of chloride ions on the early hydration of cement pastes from various perspectives, and the results from different methods are consistent.

The potential of region-specific machine-learning-based ground motion models: Application to Turkey

Conventional ground motion models have extensively been established worldwide based on classical regression analysis of records. Alternatively, advanced nonparametric machine-learning (ML) algorithms may capture the complex nonlinear behaviour of earthquake motions. This paper investigates the efficiency of artificial neural network (ANN) and extreme gradient boosting (XGBoost) in predicting peak ground acceleration (PGA), peak ground velocity (PGV) and pseudo-spectral acceleration (PSA) (period, T = 0.03–2.0 s) for the Turkish dataset. The dataset involves 1166 records of 383 events with a moment magnitude (Mw) of 4.0–7.6, Joyner and Boore distance (RJB) of 0–200 km, focal depth (FD) less than 35 km, and site condition as the averaged shear wave velocity of the soil on the top 30 m (VS30) of 131–1380 m/s. The performance of the models is compared against empirical models in terms of root-mean-square error (RMSE), coefficient of determination (R2), Pearson correlation coefficient (r), and inter-event and intra-event residuals. To perform residual analysis, a likelihood function is developed. Findings reveal that the XGBoost approach gives an unbiased model with a higher correlation and lower residual than ANN. Finally, an online platform is provided for any interested users.

The role of nano-TiO2 on the mechanical properties and hydration behavior of C2S, C3S and C4A3[formula omitted

To clarify the details of hydration between nanomaterials and single minerals in cement, C2S, C3S and C4A3S‾ were prepared by chemical synthesis, and the effects of nano-TiO2 on the hydration properties of C2S, C3S and C4A3S‾ were explored to reveal the mechanism of different hydration stages from the perspective of hydration kinetics. The results suggested that nano-TiO2 did not essentially change the type of hydration products of C2S, C3S and C4A3S‾, but mainly acted as seeds to promote the nucleation and crystal growth of hydration products, and as fillers to form denser microstructures and higher strength. However, for C4A3S‾, the crystal growth of AFt at the late stage of hydration was further promoted by nano-TiO2, resulting in microcracks due to volume expansion of the hydrated matrix. Meanwhile, the relatively insufficient amount of alumina gel caused that the AFt could not being effectively cross-linked into a monolith, so the compressive strength decreased by 29.21% and 37.8% at 14d and 28d. The hydration kinetics shows that the acceleration period of C2S, C3S and C4A3S‾ appeared earlier by reducing the activation energy required for the reaction by nano-TiO2. However, the hydration kinetic processes of C2S and C3S (NG-I-D) and C4A3S‾ (NG-D) were not disturbed by nano-TiO2, but significantly increased the hydration rates of the corresponding stages and advanced the turning point of the control stage. This demonstrated that nucleation and crystal growth of hydration products of these minerals are promoted by nano-TiO2, and the difficulty of phase boundary reactions and diffusion was also weakened.

Preparation and characteristics of paraffin/silica aerogel composite phase-change materials and their application to cement

In this study, microencapsulated paraffin/silica aerogel composite phase-change materials (MPCMs) were developed and incorporated into cement to impart heat storage/release capabilities. First, the hydrophilically modified MPCMs were subjected to a leakage test. Using a simple stirring method, the composite with an aerogel: paraffin mass ratio of 22:78 was demonstrated to have the best adsorption capacity. Transmission electron microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction analyses revealed that the paraffin was stable and physically encapsulated by the aerogel. The differential scanning calorimetry results showed that the encapsulated MPCMs had a fusion latent enthalpy of 94.45 J/g and phase-change temperature range of 20.8–34.4 ℃. The enthalpy was reduced by only 3.87% after 1000 freezing–thawing cycles. In the second part of the experiment, heat-storage cement (HSC) specimens were prepared to investigate the effect of MPCMs modified with silane coupling agents. The proportion of MPCMs and curing temperature were varied, and the effects of these variations on the compressive strengths of HSC stones were investigated. The compressive strength of the HSC samples was improved by adding multiwall carbon nanotubes (MWCNTs) to paraffin to form paraffin/aerogel composite MWCNT micro-encapsulated phase-change materials (CMPCMs). The results show that adding 1.53 wt% MWCNTs increases the thermal conductivity by 50.6% and refines the pore size and strength of the HSC stone. Furthermore, the 7-day strength of the HSC stone increased to 8.6 MPa by adding MWCNTs to 30 wt% modified CMPCM, meeting the requirement standard. Cement hydration calorimetry, performed using a TAM AIR isothermal calorimeter, revealed that MPCMs prolong the induction period of cement hydration, reduce the rate during the acceleration period of cement hydration, and absorb the heat of hydration. Moreover, the thermal regulation behaviour of 10 mm thick HSC plates was tested. The highest temperature difference was determined to be 2.36 ℃ and 1.92 ℃ during the heating and cooling processes, respectively, compared with that of plain cement plate, at the same time. Therefore, HSC panels have potential applications in building thermal management.

Insights into the acting mechanism of ettringite in expansive Portland cement

There are different theories about the acting mechanisms of ettringite in the expansive behavior of Portland cement. While it is widely recognized that a reactive source of alumina, sulfate, and calcium hydroxide, along with sufficient water, is required for ettringite formation, there are still varying perspectives on the amount, size, and morphology of ettringite crystals. This work brings insights into the mechanisms underlying the expansion of ettringite. For this purpose, cement pastes containing an expansive mixture were analyzed using an expansion measuring device, in situ X-ray diffraction, isothermal calorimetry and scanning electron microscopy. The results revealed that the content and size of ettringite crystals at the beginning of the acceleration period are critical factors for the development of expansive behavior.

Energy Harvesting and Acceleration Measuring Based on Time-Division Multiplexing Operation of a Single Piezoelectric Transducer

This letter presents a novel approach called energy harvesting and acceleration measuring (EHAM) using a single piezoelectric (PZT) transducer. The EH subsystem is a synchronous electric charge extraction (SECE) interface combining with an energy management circuit, which can harvest energy from PZT. The AM subsystem is for measuring acceleration-related signals. A time-division multiplexing strategy is employed in the EHAM system, where vibration energy is harvested during one period and vibration acceleration is measured in another period, and the harvested energy also powers the AM circuit. The prototyped EHAM system is implemented based on discrete components and tested with a conventional cantilever-based PZT harvester. Experimental results show that the EHAM system can perform EH and AM operations in a time-division multiplexing way. The EH circuit can harvest 1.76 mJ energy during 22 s with a PZT open-circuit voltage of 6 V. The AM circuit can measure accelerations with an accuracy of 95% under the mechanical resonance condition. The EHAM solution can be a candidate for self-powered acceleration measurement.

Strengthening mechanism of granulated blast-furnace slag on the uniaxial compressive strength of modified magnesium slag-based cemented backfilling material

The hydrating active mineral in the modified magnesium slag-based (MMS-based) backfilling material is mainly β-phase dicalcium silicate characterized with slow speed of hydration and low early strength. This disadvantage restricts the application of modified magnesium slag (MMS) as cementitious material in backfilling mining to some extent. In this work, the strengthening mechanism of granulated blast-furnace slag (GBFS) on the uniaxial compressive strength (UCS) of MMS-based cemented backfilling material has been investigated systematically. The hydration heat tests reveal that the duration of induction and acceleration periods are gradually shortened and the appearance time of the second exothermic peaks are obviously advanced as the proportion of GBFS increases. The total normalized hydration heat releases of MMS-based pastes containing 0, 1%, 2%, 3% and 4% (solid-mass proportion) GBFS at 120 h are 15.76, 16.02, 18.40, 22.31, and 25.54 J/g, respectively. Compared with the blank control group, the hydration heat release of MMS-based paste at 120 h increased by 62% with addition of 4% (solid-mass proportion) GBFS. In addition, the TG-DTG tests shown that the final mass-losses of MMS-based cemented backfilling materials tend to increase with the increase of the amount of GBFS. The 3- and 7-days UCSs of MMS-based backfilling mortars tend to increase dramatically with the increase of proportion of GBFS. A small amount of GBFS (1 wt%) can significantly improve the 28- and 56-days UCSs of the MMS-based mortars. Compared with the blank control group, the UCSs of MMS-based mortars cured 3, 7, 28, and 56 days increased by 74.2%, 94.6%, 38.0%, and 24.1% respectively with addition of 5% (solid-mass proportion) GBFS. The SEM, XRD, FTIR, and TG-DTG tests show that the MMS-based mortars containing GBFS generated more hydration products, yielded more compact microstructures, and consumed CH more quickly compared with that of blank control group. Compared with fly ash (FA), GBFS dissolves faster in alkaline media (leaching reactive Al and Si early), and releases much more hydration heat and Ca2+ ions during the process of pozzolanic reaction. The above three factors strengthen the UCS of MMS-based mortar. The results of this study can provide theoretical guidance for the raw material ratio design and field application of MMS-based cemented backfilling paste.

Experimental Study of Turbulence Response in a Slowly Accelerating Turbulent Channel Flow

AbstractAn investigation of flow acceleration from initial statistically steady turbulent flow to final statistically steady turbulent flow is conducted experimentally using particle image velocimetry (PIV) and constant temperature anemometry (CTA). The turbulence response is investigated as the acceleration periods and acceleration rates are varied in a controlled fashion. This work expands the research by Mathur et al. (2018, “Temporal Acceleration of a Turbulent Channel Flow,” J. Fluid Mech., 835, pp. 471–490.) studying slower and longer transient flows. It also complements the numerical studies of a step increase in the flowrate of (He and Seddighi, 2013, “Turbulence in Transient Channel Flow,” J. Fluid Mech., 715, pp. 60–102. and He and Seddighi, 2015, “Transition of Transient Channel Flow After a Change in Reynolds Number,” J. Fluid Mech., 764, pp. 395–427.). The results obtained from the current investigations are qualitatively similar to those obtained previously. Consistent with previous studies, the response of turbulence in the current slow transient flow is again characterized by a laminar-turbulent transition. The initial increase of the flow development among the cases investigated can be categorized as faster, medium, and slower responses. Modifications are made to the equivalent Reynolds number and the initial turbulence intensity proposed earlier in order to account for the slow accelerating flow rates and the continuous change of the bulk velocities of the cases investigated. It has been shown that the critical equivalent Reynolds number based on these modifications and the initial turbulence intensity are well correlated for all cases investigated and a power-law relation is established.

Catalysis and Regulation of Graphene Oxide on Hydration Properties and Microstructure of Cement-Based Materials

Graphene oxide (GO) is a two-dimensional material that adds functionalized oxygen-containing groups on the surface of graphene through strong acid oxidation. The oxygen-containing functional groups on the surface make GO have good dispersion and surface activity. When GO is incorporated into cement-based materials, while providing nucleation sites for cement hydration, it can also react with ions released by cement hydration. Therefore, GO has a catalytic effect on the hydration process of cement and plays a role in regulating the morphology of the hydration products, which in turn affects the formation of the microstructure of cement-based materials. In this study, the catalytic and regulatory effects of GO on the hydration characteristics, pore structure, and internal interface of cement-based materials are reviewed. The analysis shows that the oxygen-containing functional groups on the surface of GO can absorb a large number of water molecules, promote the dissolution of cement particles in water, and adsorb the Ca2+ released by cement particles, thereby reducing the concentration of Ca2+ around the cement particles and shortening the induction period of cement hydration. In addition, GO can provide more nucleation sites for cement hydration and shorten the hydration acceleration period. GO promotes the formation of hydration products through the nucleation effect and gradually transforms needle-like and rod-like hydration products into flower-like or polyhedral-like crystals. In addition, GO optimizes the pore structure of cement-based materials when it affects cement hydration and the morphology of hydration products through the above-mentioned effects. In addition, it makes the connection between hydration products closer through the bridging effect, so that the total porosity of cement-based materials decreases, gel-pore content increases, capillary-pore content decreases, and pore structure is significantly optimized. Finally, while optimizing the pore structure of cement-based materials, GO has an obvious optimization effect on the interface transition zone (ITZ) of cement-based materials, which significantly reduces the ITZ width and increases the ITZ density.

Analysis of biological mechanism of blood flow containing nanoparticles through an arterial stenosis

ABSTRACT This article aims to discuss the flow of nanoparticles in the blood through a stenosed artery in the presence of a magnetic field and periodic body acceleration. The overlapping shape of stenosis is chosen to show the impact of blood flow. The Bingham plastic fluid model is utilized to capture the non-Newtonian behavior of blood in the stenosed artery under diseased conditions. The resultant equations are solved analytically using the regular perturbation method. The impact of various emerging parameters on velocity, flow rate, effective viscosity, and wall shear stress are presented through graphs and discussed in detail. It is noticed that liquid velocity and flow rate increase whereas effective viscosity decreases with an increase in slip velocity and Womersley’s frequency parameter. It is also noted that liquid velocity and flow rate are decreased by enhancing the Lorentz force. The increase in body acceleration enhances fluid velocity.

Consistent seismic hazard and fragility analysis considering combined capacity-demand uncertainties via probability density evolution method

A consistent seismic hazard and fragility framework considering combined capacity-demand uncertainties is proposed, in light of the probability density evolution method (PDEM). The PDEM has solid theoretical basis in the reliability field, and it is integrated within the performance-based earthquake engineering (PBEE) for hazard-fragility assessment in this paper. During the analysis, the sample sets with different assigned probability are required to determine in advance, and the equivalent extreme events with virtual stochastic process are required to establish for solution. Both the uncertainties of capacity and demand are considered, and a combined performance index (CPI) is defined as concerned physical variable in PDEM, through pushover static and timehistory dynamic analyses. A non-stationary stochastic earthquake model is introduced using spectral representation of random functions, and the real characteristics of ground motions are reflected by one or two variables for each probability space. The peak ground acceleration (PGA) and spectral acceleration of the first period [Sa(T1)] of non-stationary stochastic ground motions are then obtained for each earthquake level, and the equivalent extreme events are also performed to discuss the statistical information of PGA or Sa(T1) through PDEM. The exceeding probability of PGA or Sa(T1) for each earthquake level is acquired, and a connection between the fragility value and hazard extent is built. The final 3D consistent hazard-fragility curves are then given, and the exceeding probability for different limit states, earthquake levels as well as intensity exceeding conditions can be predicted. Moreover, a comparison with the four classic approaches in the state-of-the-art is performed to verify the accuracy of PDEM procedure. In general, the framework avoids the pre-defined lognormal fragility shape and proves the combined efficiency and accuracy with the Monte Carlo simulation (MCS). The consistency from probabilistic hazard to fragility is realized without re-selecting earthquake waves, which is mainly attributed to the application of PDEM and non-stationary ground motions. The proposed framework provides new ideas for the consistent non-parametric hazard and fragility assessment scheme in the PBEE.

Understanding the role of C–S–H seed/PCE nanocomposites, triethanolamine, sodium nitrate and PCE on hydration and performance at early age

Compared to thermal curing, the application of C–S–H/PCE nanocomposites (CPNs) and triethanolamine (TEOA) compound admixture is a green and highly efficient hydration acceleration strategy. Commercial CPNs usually contain polycarboxylate (PCE) and residual sodium nitrate (NN). It is still uncertain whether their presence has some influence on the hydration of cement with this admixture. The experimental results show that TEOA-NN promotes hydration, and then the setting times are shortened and the early compressive strength is increased; it advances the start of the acceleration period, slightly increases tricalcium silicate (C3S) hydration, or further improves tricalcium aluminate (C3A) hydration. TEOA-PCE significantly retards C3S and C3A hydration at 1 d. In contrast, TEOA-CPNs exhibit excellent mechanical properties and hydration heat owing to its strong promotion of the hydration of C3S and C3A. These results can provide guidance for the formulated design of CPNs-based admixtures.

Study on the characteristics of alkali-activated fly ash-slag improved by cenosphere: Hydration and drying shrinkage

Cenosphere is coal-based solid waste material, which has similar chemical compositions to fly ash. In this paper, the effect of the cenosphere on hydration kinetics and drying shrinkage characteristics of AAFS pastes were explored, and the action mechanism of the cenosphere was deeply revealed. The results showed that the hydration induction period was prolonged, the hydration exothermic rate was reduced or the peak value was delayed during the acceleration period, and the 72 h hydration degree of the sample was increased when mixed with the cenosphere. The incorporation of more than 20% cenosphere significantly reduced the drying shrinkage of AAFS pastes. Comparing the results of compressive strength, drying shrinkage, and pore structure, the most suitable content of the cenosphere is 20%. To significantly improve the drying shrinkage of alkali-activated materials, the content can also be increased. The action mechanisms of the cenosphere are shown as the filling effect, pozzolanic activity, and surface effect. The addition of cenosphere reduces the amount of C-S-H, C-A-S-H and N-A-S-H gel phases, but increases the formation of silicates (calcium hydrosilitates and calcium hydroaluminates).

Inexorable land degradation due to agriculture expansion in South American Pampa

From 1985 onwards, South America has undergone a major expansion in agriculture at the expense of native vegetation (for example, native Pampa grassland). As an emblematic crop, the surface area cultivated with soybeans has increased by 1,000% between 1990 and 2020 in Uruguay. The environmental consequences of this massive land-use conversion on soil degradation remain poorly documented, although agriculture expansion is projected to continue to increase in the coming years in South America. In this study, sediment cores were collected in reservoirs located downstream of two contrasted agricultural catchments draining the Rio Negro River (Uruguay) to reconstruct the sediment dynamics and the sources of erosion associated with this expansion. Results demonstrated the occurrence of two periods of acceleration of sediment delivery since the 1980s. The first period of acceleration was recorded in the mid-1990s and was related to afforestation programs. The second and larger acceleration phase was recorded after 2000 during the soybean crop expansion. This period was marked by a greater supply of sediment from the native grassland source, highlighting the impact of agriculture expansion at the expense of native vegetation. Conservation measures should therefore be urgently taken to preserve biodiversity and soil functions in this region. The impacts on soil degradation of the massive land-use conversion of South American Pampa grasslands to agriculture are not well documented. This study estimates, over the period 1982–2019, the impacts of such conversion on the sediment cascade and how soil and water resources are affected as a result.

Dark energy with a triplet of classical U(1) fields

We present a new mechanism for cosmic acceleration consisting of a scalar field coupled to a triplet of classical U(1) gauge fields. The gauge fields are arranged in a homogeneous, isotropic configuration, with both electric- and magnetic-like vacuum expectation values. The gauge fields provide a mass-like term via a Chern-Simons interaction that suspends the scalar away from its potential minimum, thereby enabling potential-dominated evolution. We show this mechanism can drive a brief period of acceleration, such as dark energy, without the need for fine tunings. We obtain simple analytic results for the dark energy equation of state and dependence on model parameters. In this model, the presence of the gauge field generically leads to a suppression of long-wavelength gravitational waves, with implications for the experimental search for cosmic microwave background B-modes and direct detection of a stochastic gravitational wave background.

Global Leaf Area Index Research over the Past 75 Years: A Comprehensive Review and Bibliometric Analysis

The leaf area index (LAI) is widely used as an important indicator and ecological parameter of vegetation structure and growth status, but the LAI lacks bibliometric analysis. To further understand the LAI’s research status and frontier dynamics, we used 75 years of data (1947–2021) from the Web of Science for scientific bibliometric analysis. The results showed that 22,276 LAI re-search papers were published from 1947 to 2021. According to the characteristics of the literature growth, LAI research can be divided into five stages: incubation, cultivation, acceleration, evolution, and outbreak periods. The research power at the different stages had different characteristics. The overall research power of the United States is number one globally, followed by China, Canada, and France. The related disciplines were widely varied, involving agriculture (the most studied field of LAI research), environmental science and ecology, remote sensing, and other fields. The development of the Google Earth engine, cloud computing platforms, and unmanned aerial vehicle technology will provide more critical support for LAI research. The results of this paper quantitatively show the development history, research hotspots, and application of LAI research and provide a reference for understanding the current situation and development trends of global LAI research.

The time-dependent grout buoyancy behavior based on cement hydration mechanism

The grout buoyancy has a great influence on the segment during synchronous grouting of shield tunnel. Traditionally, the large buoyancy leads to certain types of tunnel distresses, such as convergence deformation, differential settlement, cracks, and water leakage. This paper made a detailed study on the time-dependent grout buoyancy behavior. The hydration heat test and LF-NMR test were carried out. Then the four periods of hydration rate curve were revealed, and the evolution rules of gel water, capillary water and free water were also obtained. The time-dependent grout buoyancy was tested by self-designed equipment, and the theoretical formula of grout buoyancy considering w/c ratio and time was proposed. The indoor test results were compared with the theoretical solution. The theoretical formulas could effectively predict the size and variation rules of buoyancy. The indoor test results showed that variation trend of cement grout buoyancy is consistent with the hydration rules. The buoyancy mainly exists in the initial period and the induction period, and decreases sharply to zero before the acceleration period. The initial setting moment is the one in which hydration rate is the largest.

The impacts of Persian Gulf water and ocean-atmosphere interactions on tropical cyclone intensification in the Arabian Sea

During the last two decades, the number of tropical cyclone (TC) events in the Arabian Sea has increased dramatically. These events have led to severe human and economic damage in Oman, Iran and Pakistan. Within this context, Gonu, Phet and Shaheen were the Arabian Sea's most destructive TCs on record, leading to a total of 6.07 billion USD in damages and 159 fatalities. Previous studies have mainly focused on atmospheric, sea surface temperature (SST) and anthropogenic impacts of TC generation and intensification. By contrast, oceanographic currents, Persian Gulf water outflow and the role of ocean-atmospheric interactions on the distribution of outflow water into the Arabian Sea and their impacts on TC intensification, are poorly understood. In order to address this issue, we use historical TC records, satellite data, atmospheric and reanalyzed oceanographic data to shed new light on the relationship between large-scale atmospheric forcing and ocean currents on TC intensification in the Arabian Sea. The results demonstrate that pre-monsoon TCs mainly occurred during co-existing La Niña, cold Indian Ocean Basin Model (IOBM) and anomalous northern hemisphere circulations over the Persian Gulf. By contrast, post-monsoon TCs were generally generated during warming acceleration period. Poleward movement of the monsoon belt provided the required humidity and energy for TC generation and increased upwelling events. Water salinity and temperature have increased in the north and northwestern parts of the Arabian Sea following rising upwelling events and a decrease in Persian Gulf outflow water depth. Rapid TC intensification has increased noticeably since 2007 and >72 % of cyclones have reached category 3 or more. We find that the rate of SST rise in the Arabian Sea is higher than the other parts of the northern Indian Ocean since 1998. SST and salinity in the Arabian Sea have been controlled by Persian Gulf outflow water and oceanographic currents. TC intensity is controlled by warm and saline (>36.6 PSU) water distribution patterns, mediated by eddy and jet currents. Rapid intensification of pre-monsoon TCs occurred by tracking to the north and northwest, with most landfalls occurring during this period. Post-monsoon TCs generally affect the center and the southwest of the Arabian Sea. The risk of intensive TCs manifests an increasing trend since 2007, therefore education programs via international platforms such as the International Ocean Institute (IOI) and UNESCO are required for the countries most at risk.

Effects of the phosphogypsum on the hydration and microstructure of alkali activated slag pastes

Effects of phosphogypsum (PG) on hydration process and microstructure of the alkali activated slag (AAS) pastes were discussed in this study, taking the natural gypsum (NG) as a reference. Hydration process was monitored by several kinds of measurements including the isothermal calorimetry, the electrical resistivity, the autogenous shrinkage and the 1H nuclear magnetic resonance. Hydration product assemblages were analyzed by the XRD, NMR, SEM and the mercury intrusion porosimetry (MIP)test. Results showed that less than 10 % of gypsums could retard the setting process of AAS pastes. PG could enhance the late strength although the early strength was decreased, but the addition of NG would reduce the strength at all ages. Induction period and the autogenous shrinkage were both reduced by gypsum gradually. Additionally, PG conducts to the higher MCL and higher polymerization degree of CASH gels than NG. And the addition of PG would refine the pore structure and produce a lower porosity than NG. Furthermore, the comprehensive analysis showed that the setting behavior happened at the initial dissolution period. And PG would delay the acceleration period, indicating the slower development of microstructure.

Identification of a Maneuvering Vessel based on Regular Operation

We present an approach for the identification of maneuvering vessels which is based on data collected during regular operations. In conjunction with previous work by the authors, this paper completes a comprehensive approach to estimating all parameters of a maneuvering model that fits exactly into the control system design concept developed as well. In this paper, the diagonal elements of the mass matrix are determined by evaluating acceleration periods of the vessel in the considered degrees of freedom. The contribution of the presented approach is the method of detecting and weighting all the available acceleration periods from a large database in order to automatically determine the parameters. Using a full-scale tugboat, the approach was tested and verified. In a real-time control loop application, dynamic positioning and a special tug maneuver were performed based on the estimation results from regular operation at fairly strong wind and current. The experiments indicate that the identification approach is extremely robust to disturbances from wind and current. This demonstrates the excellent performance of the entire system and validates the approach presented.