Dry Cement Research Articles

Influence of rice husk ash inclusion on electrical characteristics of dry cement mortar

Influence of rice husk ash inclusion on electrical characteristics of dry cement mortar

Optimization Scheduling Strategy for Energy Storage and Cement Load Aggregation Considering Production Constraints

Abstract For energy-intensive cement enterprises closely related to adjustable potential and production processes, an optimization scheduling model is proposed based on the coupling relationship between tasks and materials, taking into account the production constraints of cement users. In addition, energy storage-side pumped storage is aggregated to regulate resources, further enhancing the flexibility of regulation. For pumped storage devices, the constraints include power constraints during the charging and discharging process, power equality constraints, state constraints during charging and discharging, energy state constraints, and final energy constraints. For cement enterprises, taking the example of the new dry cement production process, the generation/consumption of materials and the occupation/release of equipment in each process are analyzed. The state-task network method is used to abstract materials and processes into states and tasks respectively, establishing process constraints for cement load production. Case simulation verifies that the proposed method can effectively reduce the comprehensive electricity cost of pumped storage and cement enterprises while ensuring the normal operation of pumped storage and cement enterprises, providing data guidance and support for cement enterprises to participate in grid interaction.

Dynamic modeling of minimum mass of pore-gas for triggering landslide in stable gentle soil slope

This paper presents a dynamic modeling method to test and examine the minimum mass of pressurized pore-gas for triggering landslides in stable gentle soil slopes. A stable gentle soil slope model is constructed with a dry cement powder core, a saturated clay middle layer, and a dry sand upper layer. The test injects H2O2 solution into the cement core to produce new pore-gas. The model test includes three identical H2O2 injections. The small mass of generated oxygen gas (0.07% of slope soil mass and landslide body) from the first injection can build sufficient pore-gas pressure to cause soil upheaval and slide. Meanwhile, despite the first injection causing leak paths in the clay layer, the generated small mass of gas from the second and third injections can further trigger the landslide. A dynamic theoretical analysis of the slope failure is carried out and the required minimum pore-gas pressure for the landslide is calculated. The mass and pressure of generated gas in the model test are also estimated based on the calibration test for oxygen generation from H2O2 solution in cement powder. The results indicate that the minimum mass of the generated gas for triggering the landslide is 2 ppm to 0.07% of the landslide body. Furthermore, the small mass of gas can provide sufficient pressure to cause soil upheaval and soil sliding in dynamic analysis.

Shear behavior of cement-stabilized silty clay exposed to low-temperature curing

Cement-stabilized soils are widely used in civil engineering applications. However, they inevitably encounter low-temperature curing conditions, particularly in cold regions. In this study, shear experiments were conducted on cement-stabilized silty clays with different dry densities, cement contents, curing ages and temperatures. The factors influencing the shear performance of cement-stabilized soils were analyzed. The results showed that the peak value of the shear stress-displacement curve of the cement-stabilized silty clay increased with the vertical pressure, and the failure patterns for soils with and without cement significantly differed. Generally, the soils without cement underwent ductile failure, whereas the cement-stabilized soils experienced brittle failure. The shear strength and cohesion of the cement-stabilized soils increased with cement content, dry density, curing age and temperature. In addition, the ice and hydration products significantly influenced the internal friction angle of the cement-stabilized soils. An optimal cement content for silty clay was determined to obtain the largest internal friction angle, which ranged from 12% to 15%. Furthermore, at the curing temperature of −2 °C, the edge-face contact form accounted for the majority with a relatively high porosity, but the morphology of C-S-H changed from a sheet-like form to reticulate structure when the curing temperature increased to 22 °C. However, the contribution of the ice crystals to the shear strength was less significant than that of the hydration products. This study provides insights into the mechanical and microstructural properties of cement-stabilized soils in cold-region geotechnical construction.

Artificial intelligence approach for predicting compressive strength of foamed concrete

Accurately predicting the compressive strength of foamed concrete plays a key role in the wide application of foamed concrete in practice. This study investigates the performance of the six AI models in estimating the compressive strength of foamed concrete. A dataset of 150 samples available in the literature was used for training and testing the AI models. The dry density, cement and sand content, and water-to-cement ratio were employed as input parameters, while the 28-day compressive strength was used as the output parameter. Four statistical indicators were utilized to evaluate the performance of the AI models. The study results reveal that the AI models yield an accurate prediction of the compressive strength of foamed concrete. The best performance model in estimating the compressive strength of foamed concrete is the M5Rules model, while the least accurate model depends on the indicators used to measure the accuracy of the AI models.

To Study the Partial Replacement of Cement by Eggshell, Chalk Powder with Addition of Basalt Fiber

Abstract: In concrete cement of Portland the aggregate are mixed with water and dry cement, they form a fluid of mass that mould easily into desired shape. The cement chemically react ingredient and water to form a matrix hard which the materials bind together into durable property stone that might use for many purpose. Use of chalk powder is also eco-friendly as the waste limestone or chalk material from industries as well as from schools and colleges, are effectively being used to form quality building materials. Basalt fiber is another solid strengthening material, which has wonderful mechanical properties and furthermore an eco-accommodating assembling process. Significantly number of examination has been directed on basalt fiber strengthened cement and has generally watched out for its mechanical properties. On the basis of previous researches which has been done we make a comparison of strength properties of concrete made with replacement and conventional concrete. Cement is replaced by Chalk, eggshell powder with addition of basalt fiber. Different specimens of the material are tested for strength. The result shows that concrete workability is fine and within limits after replacing cement with Chlak,eggshell powder with adding basalt fibers. However, workability gets reduced at higher replacement of materials. The strength parameters such as compressive strength, flexural strength, and split tensile strength also increase and show an optimum value at 8&8% cement replacement and 1.8% Addition of basalt fibers respectively. Test results are satisfactory up to 8&8% and 1.8% replacement. After this, there is a decrease in the strength of concrete. So, after this research work, we are able to find out that the replacement can be done to this extent but there may be chances of higher percentage of replacement by doing further investigations.

Processing of calcium sulfoaluminate eco-cement coatings containing microencapsulated phase change materials

On the one hand, calcium sulfoaluminate (CSA) eco-cements release about 40% less carbon dioxide (CO2) than Portland cement during fabrication; on the other hand, phase change materials dispersed in a cementitious matrix can help to optimise the indoor temperature of buildings, reducing carbon dioxide emissions related to heating/air conditioning. However, this is only economically viable if it is used as a thin layer (a coating). In addition, the combination of both materials supposes a double environmental benefit. Consequently, the main objective of this work is the preparation of a suitable homogeneous and well-adhered bilayer sample, composed of CSA and CSA-MPCM. To achieve this, in the first step, the effect of pH, temperature and stirring was studied for microencapsulated phase change material (MPCM) aqueous suspensions (47.3 wt%); second, the MPCM (45 wt% with respect to dry cement) was dispersed in a CSA paste; then, in a third step, a homogeneous well-adhered coating of CSA-MPCM, with undamaged MPCM, was obtained on a CSA matrix. This was achieved through rheological measurements and checked by microscopy. Finally, the corresponding CSA and CSA-MPCM mortars were characterised through their mechanical properties (compression) (70 and 13 MPa at 7 days, respectively) and thermal conductivity (2.06 and 1.19 W/mK, respectively).

Study on multi-performance optimization of basalt stone powder supplementary cementitious materials

In order to better apply basalt powder to supplementary cementitious materials (SCMs), this paper chooses the content of basalt stone powder, fly ash and slag as the influencing factors, and the 7d drying shrinkage rate, 28d drying shrinkage rate, fluidity, 7d and 28d compressive strength of mortar as the evaluation indexes of SCMs. Based on the response surface and multi-objective optimization method, the Box-Benken experimental design method was used to study the influence of the physical and chemical superposition of various factors on the properties of supplementary cementitious materials and optimize the ratio. The low-field nuclear magnetic resonance technique was used to detect the water change and porosity difference between the reference group and the optimization group at each age. The results show that the linear interaction and interaction of basalt powder, fly ash and slag have an effect on the strength, fluidity and drying shrinkage of cementitious materials. The optimal mixing ratio of basalt stone powder supplementary cementitious material is stone powder (10.8 %), fly ash (5 %) and slag (22.69 %). Under this mix ratio, the properties of basalt powder-assisted cementitious materials have been improved and close to the reference group. In the early hydration process, the physical filling effect of supplementary cementitious materials such as stone powder can better optimize the pore structure inside the slurry and the water loss is small, the strength is improved slowly, the dry shrinkage pure cement sample is similar, and the fluidity is improved. With the extension of hydration time, the water loss of the optimized group increased, and the strength and drying shrinkage increased.

Manufacture of potassium chloride from cement kiln bypass dust: An industrial implementation case for transforming waste into valuable resources

The recirculation of chlorine within the kiln presents a major hurdle in co-processing domestic waste in cement kilns. This chlorine enrichment not only adversely affects the quality of cement, but also pose a serious challenge to the subsequent eco-friendly disposal of kiln dust. To solve this problem, a proper bypass system has been implemented in this study on a 4000 t/d new dry process cement rotary kiln, and the collection of chlorine-rich bypass dust outside the kiln (30 t/d) has been achieved. In addition, a comprehensive and innovative system has been developed, including water washing and subsequent triple-effect salt extraction, to achieve leaching of K+ and Cl from the bypass dust in the water rinsing liquid, while effectively removing harmful metal ions such as Pb2+. Finally, the extraction of high-purity KCl salt (6 tons/day, purity of 90 %) has been successfully achieved. It is worth noting that high-temperature flue gas rich in CO2 has been used to precipitate certain heavy metal ions, while steam from the waste-heat power generation system has been employed as a heat source for the potassium salt evaporation process. More importantly, all the materials, except for the KCl salt product, are returned to the cement kiln system without causing any secondary pollution. This study not only effectively addresses the negative impacts of chlorine element circulation within cement kilns during domestic waste co-processing, but also achieves a highly innovative engineering practice of transforming waste into valuable resources from kiln dust to high-purity KCl products. In brief, this work provides a reference example for future approaches to clean production, carbon reduction and resource utilization in the cement industry.

Electrochemical Impedance as an Assessment Tool for the Investigation of the Physical and Mechanical Properties of Graphene-Based Cementitious Nanocomposites.

This investigation explores the potential of electrochemical impedance spectroscopy (EIS) in evaluating graphene-based cementitious nanocomposites, focusing on their physical and structural properties, i.e., electrical resistivity, porosity, and fracture toughness. EIS was employed to study cement mixtures with varying graphene nanoplatelet (xGnP) concentrations (0.05-0.40% per dry cement weight), whereas flexural tests assessed fracture toughness and porosimetry analyses investigated the structural characteristics. The research demonstrated that the electrical resistivity initially decreased with increasing xGnP content, leveling off at higher concentrations. The inclusion of xGnPs correlated with an increase in the total porosity of the cement mixtures, which was indicated by both EIS and porosimetry measurements. Finally, a linear correlation emerged between fracture toughness and electrical resistivity, contributing also to underscore the use of EIS as a potent non-destructive tool for evaluating the physical and mechanical properties of conductive nano-reinforced cementitious nanocomposites.

Initial state of excavated soil and rock (ESR) to influence the stabilisation with cement

This paper investigates the initial state of excavated soil and rock (ESR). These initial states include dry density, organic content, water content (Wc), cement content (Cc), liquid index (LI), dry or wet mixing method. Three ESRs collected from tunnelling projects and kaolin were used in this study to compare. The specimens (i.e., 50 mm in diameter and 100 mm in height) were prepared in the laboratory and cured at 7 and 14 days, and then assessed by the unconfined compressive strength (UCS) test. The analysis shows that the ratio of Wc/Cc is the primary factor to obtain different UCS for high LI ESR and a simple equation is proposed for quick prediction. For ESR with a more general LI, predictive equations are also proposed in terms of artificial neural network (ANN) and genetic programming (GP) for 7-days curing time. The results indicate that the both ANN models with Bayesian Regularization (BR) algorithm outperform ANN with Levenberg-Marquardt (LM) and GP model are accurate to predict UCS of mixtures.

Electrified calciner concept for CO2 capture in pyro-processing of a dry process cement plant

Around two-thirds of the CO2 emission from the cement industry comes from calcite decomposition (CaCO3 → CaO + CO2), and most of this reaction happens in the calciner. So, it is possible to reduce the CO2 emission significantly by electrifying the calciner. This possibility is studied in this work through a process simulation model using Aspen Plus. The model is first calibrated with experimental results for a cement calciner heated by coal firing. The validated model is then electrified with three scenarios of gas recycling. Electrifying an existing calciner will require high gas recycling, while some alternative designs require no gas recycling. The results indicate that this method could reduce the CO2 emissions by as much as 78%. The total energy (including fans, calciner and kiln) required in the coal-fired calciner system is around 138 MW. The energy in the electrified system may vary between 154 MW for high gas recycling and 137 MW for no gas recycling. The net excess energy in the electrified calciner per captured CO2 unit varies between 0.6 MJ/kgCO2 for high gas recycling and −0.04 MJ/kgCO2 for no gas recycling.

Compressive strength and piezoresistivity of smart cement paste modified with waste steel slag

This study intends to examine ordinary Portland cement (OPC) with a constant water-to-cement ratio (w/c) of 0.38 and different concentrations of steel slag (SS) from 0 to 30% weight of dry cement behaves in terms of compressive strength, electrical resistivity, and piezoresistivity. Since iron is the main constituent of steel slag, adding steel slag may improve electrical resistivity, which is the main requirement for structural health monitoring of cementitious material. Therefore, using the two-probe (2P) and four-probe (4P) approaches, the resistivity of cement paste was compared and measured from early curing to 28 days. The ideal value of steel slag was chosen for the electrical resistivity and piezoresistivity of cement paste at various curing times based on the compressive strength (CS) findings of smart cement paste modified with various steel slag contents. Since the wire probe is not considered in four-probe, the findings show that 4P is more accurate than 2P for detecting electrical resistivity. According to the findings of the piezoresistivity test, adding 15% of steel slag to cement improves piezoresistivity by 71% compared to cement alone and decreases compressive strength by 16.9% compared to cement without steel slag. At the same time, they were increasing compressive strength and piezoresistivity by 15.85 and 64%, respectively, while substituting 5% of the steel slag with cement weight. The electrical resistivity of cement paste was predicted using a Vipulanandan p-q model during 28 days of curing, as well as the change in electrical resistivity as a function of compressive strength at 3, 7, and 28 days. The Vipulanandan p-q model accurately predicted both the characteristics of electrical resistivity and piezoresistivity.

Rozwój badań nad scaloną uniwersalną domieszką do zaczynu cementowego

Due to the wide variety of drilling and cementing conditions, different grades of cements for different conditions need to be produced by factories. Nowadays, with the development of test methods and techniques, additional materials and substances, the trend has been to focus on some basic cement (base), which, with various additional substances or materials, can be modified according to the conditions of use. According to the technology adopted in Schlumberger, two portions of cement slurry are mainly used for the entire length of the annulus “lead” and “tail” i.e. literally the “leader” (the first portion) and the “tail’ (the second, last portion). Of course, the treatment of these portions with chemical reagents is different, and the first portion is several times larger in volume than the second portion. It is known that as a result of unsuccessful cementing, a gas-water-oil show may appear, leading to the removal of casing strings, fire, etc. As a result, this leads to the abandonment of the well. There is a time difference between the mixing of the first and subsequent portions of dry cement, especially the last ones, since while the subsequent portions of dry cement are just being mixed, the freshest ones have not yet been mixed at all, but the first portions are already finished; this portion of cement slurry in the well gradually begins to thicken under the influence of temperature and pressure. An effective reagent is needed. The optimal composition of the combined reagent should be considered as follows: CMC – 0.2%; FLS – 0.4%; Na2CO3 – 0.05%.

Probabilistic modeling of offshore deep cement mixing improved ground

Deep cement mixing (DCM) is an effective technique for ground improvement by injecting dry cement or cement slurry into the ground with continuous mixing and finally forming cemented soils with improved mechanical properties. A large-scale spatial distribution model is established in this study to investigate the characteristics of spatial variation in the unconfined compressive strength (UCS) of DCM clusters in a marine clay area. Variograms were used to determine the spatial variability and scale of fluctuations in the UCS data of DCM coring samples and the UCS of the natural ground from cone penetration tests. Referring to the layering characteristics of the study site, the auto-correlation structure was determined using random field modeling. Based on the generated spatial distribution and probabilistic assessment of UCS for the DCM construction site, this study compares the variations in spatial magnitude, uniformity, and variability of site-wide UCS before and after the construction of DCM clusters.

Control of Precalciner Temperature in the Cement Industry: A Novel Method of Hammerstein Model Predictive Control with ISSA

As the most critical equipment in the pre-calcination process of dry cement production, the temperature of the precalciner is an essential factor affecting the quality of cement. However, the cement calcination system is time-delayed, nonlinear, and multi-disturbance, which makes it difficult to predict and control the precalciner temperature. In this study, a deep learning-based Hammerstein model is proposed, and a model predictive control system is built to predict and control the precalciner temperature. In the prediction model, the CNN-GRU network architecture is used to extract the operating states of the precalciner, and an attention mechanism is employed to find and emphasize the important historical information in the extracted states. Then, an ARX model is built to predict the temperature of the precalciner using the extracted operating state information. The complex nonlinear model solution in the control system is formed into a linear control problem and an inverse solution problem. The generalized predictive control (GPC) is used for linear control, and the improved sparrow search algorithm (ISSA) is used for the problem of an inverse solution. Tested with data from a cement plant in Hebei, China, the prediction accuracy of the model proposed in this paper is 99%, and the established control algorithm has less overshoot compared to PID and better stability in anti-disturbance tests. It is demonstrated that the prediction model developed in this study has better accuracy and the control strategy based on this model has good robustness.

Miniature pH detection probe for in-situ monitoring of cement paste inside

A miniature pH detection probe which was fabricated from an oxidized tungsten wire electrode and a solid-contact silver-silver chloride electrode was developed and used for monitoring alkalinity of cement pastes. The pH detection probe which was embedded in wet cement paste block showed the stable potential differences assigned to pH 12–14 for at least more than 2 months. Although the potential difference of the probe showed inconsistent values in dry cement paste, the probe recovered to show the correct values after the re-wetting of cement paste. In an accelerated corrosion test of rebar co-embedded in cement paste using a pH detection probe, the probe showed the potential difference shift in acidic direction and illustrated depassivation of steel surface, accumulation of corrosion products in the paste, and crack formation of the paste. It was indicated that the pH detection probe was effective to evaluate not only alkalinity but also the deterioration of reinforced concrete.

Emission characteristics of dioxin during solid waste co-processing in the Chinese cement industry

Development of co-processing technology in the cement industry in China is important for environmentally sound disposal and recycling of waste, and contributes to sustainable development of the cement industry. However, dioxin pollution could negatively affect promotion of this technology. Therefore, it is necessary to study the emission characteristics of dioxins in cement kilns. In this study, the emission characteristics of dioxins and factors influencing their generation during co-processing solid wastes were studied in 14 new dry cement kilns. The dioxin concentrations were very similar regardless of whether solid wastes were fed into the kiln. In blank runs without co-processing, the average dioxin concentration was 0.0097 ng international toxic equivalents (I-TEQ)/Nm3. By comparison, that for co-processing solid wastes was 0.012 ng I-TEQ/Nm3. These values meet the relevant emission standards. The type of co-processed solid wastes had almost no effect on the dioxin concentration. At larger production scales, the concentration of dioxin emitted in the flue gas decreased. The dioxin concentrations in kiln dust were obviously higher than those in clinker and raw materials. The average emission factor of dioxin per ton of cement was 30 ng I-TEQ/t, which is equivalent to that in cement kilns in other countries.

Improvements in the Engineering Properties of Cementitious Composites Using Nano-Sized Cement and Nano-Sized Additives.

The findings of an extensive experimental research study on the usage of nano-sized cement powder and other additives combined to form cement-fine-aggregate matrices are discussed in this work. In the laboratory, dry and wet methods were used to create nano-sized cements. The influence of these nano-sized cements, nano-silica fumes, and nano-fly ash in different proportions was studied to the evaluate the engineering properties of the cement-fine-aggregate matrices concerning normal-sized, commercially available cement. The composites produced with modified cement-fine-aggregate matrices were subjected to microscopic-scale analyses using a petrographic microscope, a Scanning Electron Microscope (SEM), and a Transmission Electron Microscope (TEM). These studies unravelled the placement and behaviour of additives in controlling the engineering properties of the mix. The test results indicated that nano-cement and nano-sized particles improved the engineering properties of the hardened cement matrix. The wet-ground nano-cement showed the best result, 40 MPa 28th-day compressive strength, without mixing any additive compared with ordinary and dry-ground cements. The mix containing 50:50 normal and wet-ground cement exhibited 37.20 MPa 28th-day compressive strength. All other mixes with nano-sized dry cement, silica fume, and fly ash with different permutations and combinations gave better results than the normal-cement-fine-aggregate mix. The petrographic studies and the Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) analyses further validated the above findings. Statistical analyses and techniques such as correlation and stepwise multiple regression analysis were conducted to compose a predictive equation to calculate the 28th-day compressive strength. In addition to these methods, a repeated measures Analysis of Variance (ANOVA) was also implemented to analyse the statistically significant differences among three differently timed strength readings.

Experimental Study on Unconfined Compressive Strength of Natural Rubber Modified Soil Cement

This paper presents the test results of experimental study on unconfined compressive strength of natural rubber modified soil cement. In this study, the cement content, defined as ratio of dry cement weight to dry soil weight, ranged from 4 to 12 percent and the rubber-cement ratio, defined as ratio of natural liquid latex rubber weight to dry cement weight, ranged from 0 to 0.08. It can be observed that the unconfined compressive strength increased with increasing value of rubber-cement ratio for the specimens with cement content of 4 and 8 percent. However, a decrease in unconfined compressive strength with increasing rubber-cement ratio was observed in the specimens with cement content of 12 percent. The effect of rubber-cement ratio on strength was found to be significant at low value for both cases. It was also found that the unconfined compressive strength was increased with increasing cement content. A linear relationship was found for specimens without rubber content. It should be noted that a unique relationship was found for the specimens with rubber content.