Compressive Strength Of Cement Research Articles

The effect of SiO2/PEGMA/AA nanocomposites on hydration process and mechanical properties of oil well cement

SiO2 nanoparticles coated with PEGMA and AA (SiO2/PEGMA/AA) were synthesized by radical polymerization. The chemical structure and particle size distribution of the SiO2/PEGMA/AA nanocomposites were characterized. The zeta potential, rheological properties, hydration rate, hydration products, microstructure, pore structure and compressive strength of oil well cement were investigated. The results showed that the core–shell structure endowed the SiO2/PEGMA/AA nanocomposite with multiple functions, which could not only efficiently facilitate the fluidity of the cement pastes, but also significantly promote the cement hydration and densify the microstructure of hardened cement pastes. The compressive strength of cement with 2 wt% SiO2/PEGMA/AA nanocomposites was increased by 45.6% curing for 28 days, which was much better than cement with the physical blending of SiO2 nanoparticles and PEGMA/AA superplasticizer.

STUDY THE EFFECT OF ADDING GLENIUM 51 AND POLYMERIC PLASTICS ON THE MECHANICAL AND PHYSICAL PROPERTIES OF ORDINARY PORTLAND CEMENT

Cement is importance as one of the strategic construction of any civilization depends, and its paramount significance in the construction of building, roads, bridges and infrastructure, which requires the use of cement with special specification and thus the use of polymers as additives to increase the compressive, flexural and tensile strength of the cement used in construction. Cement producing can possibility with high specification and for multiple uses, some studies be carried out on the use of some available additives in small quantities so as to give the cement high desirable specification in terms of color, compressive strength, tensile and permeability compared to ordinary cement. This research aims to know the extent to which some of the physical and mechanical properties of cement mortar, such as compressive strength, flexural and tensile strength, are improved upon weight substitution of specific polymeric materials with high efficiency, such as, silica fume .styrene-butadiene, styrene- acrylic in low weight ratio so that it does not add a high economic cost to the production of therequired concrete .for specific uses and sheds light on the effect of different temperatures on the properties where studied in this study . The study showed that the addition of polymeric materials (Glenium 51, silica fume, styrene –butadiene) with different weight ratio of cement weight at 20°C led to obtaining the highest compressive strength, flexural and tensile strength at the optimum level to the development and improvement of properties. Mechanical and physical cement mortar compared to the reference cement free of additives .As for the use of styrene –acrylic, it had a negative effect and led to a decrease in the compressive and tensile strength .especially in the later ages compared to the reference cement. The optimum ratio of Glenium51 was added to the optimum ratio of each material separately and the mixture was added to the cement mortar at different temperatures( 7, 20, 55 )°C .The effect of additives on the properties of the cement mortar was studied. Also, a mixture (Glenium51, silica fume, styrene-butadiene, styrene-acrylic) was added in the optimum proportions for each material to the cement mortar at different temperatures, and this addition led to increase on compressive, flexural and tensile strength at all temperatures compared with reference cement. Silica fume, styrene-butadiene rubber and styrene acrylic were added separately to the cement mortar without Glenium51, then a mixture of silica fume, styrene-butadiene, and styrene-acrylic was added to the cement mortar .The results showed that the compressive, flexural and tensile strength of cement mortar increase while styrene acrylic decrease these properties when compared with the reference mixture.In addition, the study showed the effect of temperature to the properties of added polymers with cement mortar, All experiments were performed at different temperatures (The temperature which Iraq's climate is exposed under natural conditions.All experiments were conducted at different temperatures (7, 20, 55)°C respectively, to show the effect of degrees on cement compressive strength, which the degree7 represents in winter, 20 in spring and autumn, and 55 in summer.

Dispersing silica fume in cementitious materials by silane copolymerized polycarboxylate Superplasticizer: On the role of dispersion effectiveness as a function of silane concentration

In this paper, a commonly used vinyl based silane coupling agent (SC), namely γ-methacryloxy propyl trimethoxyl silane (MAPTMS) was designed to co-polymerize with polycarboxylate superplasticizer (PCE) to increase the compatibility of PCE with silica fume (SF). The role of dispersion effectiveness as a function of silane concentration was systematically analyzed. It was found that at lower MAPTMS concentration, the prepared SC-PCE showed better SF dispersion capability than the control PCE with increasing MAPTMS concentration. The increased particle dispersion effectiveness was confirmed by minimized volume average particle size of SF by two orders of magnitude (from 27.507 μm to 0.275 μm), as well as a much slower SF particles settlement speed in a model cement solution. Increment of cement compressive strength reconfirmed the positive effect of SC-PCE on particle dispersion. When the mole substitution of AA by MAPTMS overran to 40%, however, SC-PCE behaved like polymeric silane silica sol and gelled as indicated by increase of viscosity overtime. The dispersion ability of SC-PCE ceased to be in effect. A maximum substitution ratio of MAPTMS was therefore need to be considered when designing a more effective SC-PCE for SF, as well as for other siliceous SCM.

Application of fuzzy inference system (FIS) for assessment and predication of compressive asset of concrete containing fly ash

Fuzzy Inference System (FIS) for forecasting the 90 days compressive asset of cements containing low and high limes cinders have been modified by using MATLAB2016a. For motivation behind to modified this model is 160 specimens and 48 different mixes found form the literatures. Water, cover of the day, crushed stone-I (3–7 mm), Portland cement, Fly Ash (FA) replacement ratio has been used as input parameter in the FIS modelling system. The output is the boundary which is compressive strength of cement. The preparation and testing results advocate that the FIS modelling system have the durable potentially predict 90 days compressive strength of concretes fly ash and maybe used for some other purpose also. This FIS system provide the reasonable results with the comparison of previous studies.

An Insight into the Effect of Rice Straw Biochar on Compressive Strength and Thermal Conductivity of Cement

It is well known that is very important to improve the quality of cement material concerning its compressive strength and thermal conductivity, which may reduce its quantity of usage and improve the heat maintenance of a structure compared with the traditional cement. In order to improve the properties of cement and other building materials, the test pieces were prepared by incorporating rice straw biochar with different pyrolysis temperatures into cement paste, and the compressive strength and thermal conductivity were tested after curing under both wet and dry conditions. The results showed that with the increase of biochar incorporation, the strength and thermal conductivity of the test blocks were decreased, but the thermal insulation performance of them was increased, and the quality and density of the test block were reduced. Under the condition of wet curing, the strength of the test pieces enhanced greatly with the dosage of 1% and 5%. When the dosage was 1%, the strength of the wet curing test block was the highest, which was increased by 51.06% compared with the blank control. The block strength increased by 14.98%; the thermal conductivity of the test piece incorporating biochar was reduced, and the test piece with 10% of the dry curing showed better thermal insulation performance, and the thermal conductivity was reduced by 39.21%. It can be seen that the addition of biochar improves the strength of the test block and optimizes the thermal insulation performance of the cement.

Hierarchically Reorganized Multi-Layer Fuzzy Neural Networks Architecture Driven With the Aid of Node Selection Strategies and Structural Network Optimization

In this study, a design methodology based on fuzzy sets inference and polynomial neural network(PNN) for hierarchically reorganized self-organizing network architecture is introduced to cope with over-fitting as well as multi-collinearity problems which generally appear in a conventional fuzzy neural network. The design method of the proposed self-organizing network structure provides an efficient solution to construct the hierarchically reorganized multi-layer fuzzy neural networks (HRmFNN) architecture through a synergy of multi-techniques such as L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -norm regularization, probability theory, and multi-optimization. The overall network structure is realized with the aid of parallel network structure with newly added inputs as well as effective neuron selection method through the exponential-based roulette selection technique for each layer in HRmFNN, and the least square error estimation (LSE)-based learning method with L2-norm regularization is used for constructing the stabilized network architecture, and their ensuring design methodologies result in alleviating the overfitting phenomenon and also enhancing the generalization ability. For the performance enhancement of HRmFNN directly affected by some parameters such as the number of input variables, collocation of the specific subset of input variables, the number of membership functions per each variable, and the order of polynomial in the consequent parts of the fuzzy rules, multi-particle swarm optimization (MPSO) is exploited for the effectively structural as well as parametric optimization of the proposed network. That is, the multi-optimization helps achieve a compromise between the better generation performance and the alleviated over-fitting leading to the stabilization of the proposed multi-layered self-organizing network structure with the aid of synergistic multi-techniques such as a) L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -norm regularization-based LSE learning, b) probability theory for effective neuron selection, and c) novel parallel network structure including newly added inputs and neuron selection method. The performance of the proposed network structure is quantified by comprehensive experiments and comparative analysis. It is also demonstrated through the application to cement compressive strength.

Prediction of Cement Compressive Strength by Combining Dynamic Models of Neural Networks

Prediction of Cement Compressive Strength by Combining Dynamic Models of Neural Networks

Influence of Tranexamic Acid on Elution Characteristics and Compressive Strength of Antibiotic-Loaded PMMA-Bone Cement with Gentamicin.

Purpose: The topical application of tranexamic acid (TXA) into the joint space during total joint arthroplasty (TJA) with no increase of complications, has been widely reported. We investigated the influence of TXA on antibiotic release, activity of the released antibiotic against a clinical isolate of S. aureus, and compressive strength of a widely used commercially prepared gentamicin-loaded cement brand (PALACOS R + G). Method: 12 bone cement cylinders (diameter and height = 6 and 12 mm, respectively) were molded. After curing in air for at least 1 h, six of the cylinders were completely immersed in 5 mL of fetal calf serum (FCS) and the other six were completely immersed in a solution consisting of 4.9 mL of FCS and 0.1 mL (10 mg) of TXA. Gentamicin elution tests were performed over 7 d. Four hundred µL of the gentamicin eluate were taken every 24 h for the first 7 d without renewing the immersion fluid. The gentamicin concentration was determined in a clinical analyzer using a homogeny enzyme immuno-assay. The antimicrobial activity of the eluate, obtained after day 7, was tested. An agar diffusion test regime was used with Staphylococcus aureus. Bacteria were grown in a LB medium and plated on LB agar plates to get a bacterial lawn. Fifty µL of each eluate were pipetted on 12-mm diameter filter discs, which were placed in the middle of the agar gel. After 24 h of cultivation at 37 °C, the zone of inhibition (ZOI) for each specimen was measured. The compressive strength of the cements was determined per ISO 5833. Results: At each time point in the gentamicin release test, the difference in gentamicin concentration, obtained from specimens immersed in the FCS solution only and those immersed in the FCS + TXA solution was not significant (p = 0.055–0.522). The same trend was seen in each of the following parameters, after 7 d of immersion: (1) Cumulative gentamicin concentration (p < 0.297); (2) gentamicin activity against S. aureus (strongly visible); (3) ZOI size (mostly > 20 mm) (p = 0.631); and (4) compressive strength (p = 0.262). Conclusions: For the PALACOS R + G specimens, the addition of TXA to FCS does not produce significant decreases in gentamicin concentration, in the activity of the gentamicin eluate against a clinical isolate of S. aureus, the zone of inhibition of S. aureus, and in the compressive strength of the cement, after 7 d of immersion in the test solution.

Effects of polycarboxylate superplasticiser on hydration characteristics and hardened properties of cement blended with seawater

The manufacturing of concrete using seawater provides a promising method to overcome shortages of fresh water and provides both economic and environmental benefits. However, the effects of superplasticiser on seawater-blended concrete, particularly from fresh to hardened properties, have not been thoroughly explored, which hinders the performance-based design of seawater-blended concrete. In this study, based on the water-film theory, the effects of two typical polycarboxylate superplasticisers (PCEs) on the hydrated characteristics and hardened properties of seawater-blended cement were systematically investigated. Water film thickness (WFT) was first analysed to determine the dispersion performance of the PCEs in seawater. The hydration heat was monitored using isothermal conduction calorimetry, and the products were analysed using X-ray diffraction, thermogravimetric analysis, and derivative thermogravimetry. Microstructures were investigated using scanning electron microscopy with energy-dispersive spectroscopy. In addition to compressive strength testing, the pore structures of the seawater-blended cementitious materials were analysed using mercury intrusion porosimetry. The results indicated that the incorporation of PCEs slightly increases the WFT in cement mixed with tap water and seawater. Furthermore, although seawater increased the hydration heat and densified the microstructures of the specimens with both PCEs, the hydration products were not influenced. Additionally, the compressive strength of cement with tap water and seawater decreased as a result of the increase in the proportion of capillary pores induced by incorporating PCEs.

Strength optimization of cementitious composites reinforced by carbon nanotubes and Titania nanoparticles

Carbon nanotubes (CNTs) and titanium dioxide (Titania) nanoparticles are simultaneously incorporated in a cement slurry, and their influence on the mechanical characteristics is investigated. Response surface methodology (RSM) is employed to maximize the strength properties at various incorporation ratios of CNT-COOHs, Titania nanoparticles, and surfactant following the Box-Behnken Design. The morphology and microstructure of the specimens are characterized by XRD, FTIR, and FESEM. According to the experimental results and the ANOVA analysis, it can be concluded that the simultaneous use of Titania nanoparticles and CNT-COOHs significantly enhanced the flexural and compressive strength of cement. The incorporation of Titania nanoparticles displays the most significant effect on compressive strength, mostly due to their nano-filling effect and the preparation of hydration products as nucleation sites. This study also proposes a new, faster and easier, method for the prediction of optimum weight percentages of nanomaterials and surfactants for experimental work.

Pemanfaatan Fly Ash Limbah Pembakaran Batubara sebagai Zat Mineral Tambahan (Additive) terhadap Perbaikan Kualitas dan Kuat Tekan Semen

A series of tests were carried out to determine the effect of the addition of coal combustion fly ash as an additional mineral (additive) on improving the quality and compressive strength of cement according to the Indonesian National Standard (SNI 15-2049-2004). Research methods include sample preparation, manufacture of cement with 0%, 5%, 8%, 12%, and 15% fly ash variations, chemical and physical properties of cement. The parameters measured were the level of chemical composition (%) using X-Ray Fluorescence Spectroscopy (XRF) ARL 9800 OASIS, free lime content (%) by volumetry, insoluble residue level (%) by gravimetry, compressive strength (kg/cm2), and smoothness cement (cm2/g). The results showed that the addition of fly ash increased the SiO2 content of cement, thereby increasing C3S and C2S compounds which are compressive strength components of a cement. Besides, the addition of fly ash is directly proportional to IR levels, compressive strength, smoothness, and inversely proportional to free lime levels. So the addition of fly ash can improve the quality of cement by increasing chemical components, increasing compressive strength, and reducing cracking or expansion of cement.

Building fuzzy relationships between compressive strength and 3D microstructural image features for cement hydration using Gaussian mixture model-based polynomial radial basis function neural networks

Generally, chemical compositions and physical properties such as the contents of clinkers, surface area and particle size distribution are used to estimate cement compressive strength (CCS). However, the conventional approaches are limited by the high complexity of physical changes and chemical reactions during cement hydration, which perform poorly facing the complex and uncertain evolution of cement paste. Considering that the cement microstructure can directly reflect the state of cement hydration and the information related to CCS at microscale, microtomography, which can image three-dimensional microstructure of cement paste, offers scientists another way to study CCS. Moreover, it enables us to understand the formation mechanism of the physical properties of cement and helps design high-performance materials. This paper studies the relationship between cement microstructure and compressive strength using fuzzy neural networks. The fuzzy relationships between CCS and microstructural image features are built as the “if-then” format using the polynomial-based radial basis function networks with Gaussian mixture model (GMM-PRBFNNs) from microtomography images. The GMM-PRBFNNs are proposed to improve the performance by using GMM to generate membership functions for constructing the premise of the fuzzy rules. Moreover, four types of polynomials such as constant, linear, quadratic and modified quadratic are considered as the weights between the hidden layer and the output layer for the consequent of fuzzy rules. Experimental results manifest that the built fuzzy relationships not only perform well in approximating CCS but are also easy to comprehend.

Influence of MWCNTs on portlandite Ca(OH)2 hydrates in MWCNT – reinforced concrete

Purpose The aim of this research is to study the role and formation of hydration products particularly crystalline portlandite Ca(OH)2 in MWCNT-reinforced concrete at 28 days. Concrete is the largest manufactured building material in world in which cement, sand aggregates and water cement ratio plays governing role. Water–Cement ratio decides it strength, usage, serviceability and durability. As strength of concrete depends on formation of crystalline hydrates; therefore, water–cement ratio can alter formation of hydrates also. Unfortunately, concrete is the most brittle material and to overcome brittleness of conventional concrete is tailored with some fibers. Till now, multiwalled carbon nano tubes are the most tensile and strongest materials discovered. Addition of multiwalled carbon nano tubes changes basic properties of conventional concrete. Therefore, it is important to evaluate formation of crystalline hydrates in multiwalled carbon nano tube–reinforced concrete by micro structure analysis. Design/methodology/approach Till now, multiwalled carbon nano tube–reinforced concrete has not been analyzed at micro structure level. To accomplish the objective, four concrete mixes with 0.45, 0.48, 0.50 and 0.55 water–cement ratio having 0.5 and 1% multiwalled carbon nano tubes incorporated by weight of cement, respectively. For hardening property analysis, compressive strength was obtained by crushing cubes; flexural strength was obtained by three-point loading; and split tensile strength was obtained by splitting cylindrical specimens. For analyzing role and formation of crystalline portlandite Ca(OH)2 hydrates, X-ray diffraction test was conducted on 75-µ dust of each mix. Scanning electron microscopy analysis was performed on fractured samples of crushed cubes of multiwalled carbon nano tube–reinforced concrete samples to check aggloremation. Findings It was observed multiwalled carbon nano tubes successfully enhanced compressive strength, flexural strength and split tensile strength by 8.89, 5.33 and 28.90%, respectively, in comparison to reference concrete at 0.45 water–cement ratio and 0.5% multiwalled carbon nano tubes by weight of cement. When its content was increased from 0.5 to 1% by weight of cement compressive strength, flexural strength and split tensile strength diminished by 2.04, 0.32 and 1.18%, respectively, at 0.45 water–cement ratio. With the increment of water–cement ratio, overall strength decreased in all mixes, but in multiwalled carbon nano tube–reinforced concrete mixes, strength was more than reference mixes. In reference, concrete at 0.45 water–cement ratio crystalline portlandite Ca(OH)2 crystals are of nano metre size, but in carbon nano tube–reinforced concrete mix having 0.45 water–cement ratio and 0.5% multiwalled carbon nano tubes by weight of cement, its size is much smaller than reference mix, thereby enhancing mechanical strength. In reference, concrete at 0.55 water–cement ratio size of crystalline portladite Ca(OH)2 crystals is large, but with incorporation of multiwalled carbon nano tubes, their size reduced, thereby enhancing mechanical strength of carbon nano tube–reinforced concrete having 0.55 water–cement ratio and 0.5 and 1% multiwalled carbon nano tubes by weight of cement, respectively. Also at 1% multiwalled carbon nano tubes by weight of cement, agglomeration and reduction in formation of crystalline portlandite Ca(OH)2 crystals were observed. Multiwalled carbon nano tubes effectively refine pores and restrict propagation of micro cracks and act as nucleation sites for Calcium-Silicate-Hydrate phase. Geometry of crystalline axis of fracture for portlandite Ca(OH)2 crystals is altered with incorporation of multiwalled carbon nano tubes. Crystalline portlandite Ca(OH)2 crystals and bridging effect of multiwalled carbon nano tubes is governing factor for enhancing strength of multiwalled carbon nano tube reinforced concrete. Practical implications Multiwalled carbon nano tube–reinforced concrete can be used to make strain sensing concrete. Originality/value Change in geometry and size of axis of fracture of crystalline portladite Ca(OH)2 crystals with incorporation of multiwalled carbon nano tubes.

New insights into the role of space on the microstructure and the development of strength of multicomponent cements

The hydration, porosity, and compressive strength of cements at varying water/cement and limestone/cement ratios were investigated. Thanks to the broad range of the effective water/cement studied, new insights into the nature of the C–S–H phase and the basic mechanisms behind the formation of mechanical performance were gained. The mechanical properties of the main hydrated phase, the C–S–H, are governed by the available space. It was shown that the space available modifies the C–S–H microstructure, which in turn is reflected in the pore volume and porosity distribution. In high-porosity environments, a C–S–H with the higher amount of gel pores forms and efficiently fills the porosity. Contrarily, in low-porosity environments, the coarse microstructure forms. Furthermore, the available space has impact on the clinker reaction and chemical composition of the C–S–H. It was demonstrated that the available space alone is responsible for a part of the microstructure modifications ascribed to the pozzolanic and semi-hydraulic reactions.

Effect of Different Activators on Rheological and Strength Properties of Fly Ash-Based Filling Cementitious Materials

In this paper, lime, gypsum, NaOH, and Na2SO4 are mainly used to study the activation degree and activation mechanism of fly ash, and L9 (34) orthogonal table is used for the orthogonal test. The influence of different activators on the rheological and strength properties of slurry was analyzed. The microstructure and hydration products of fly ash cement cementitious body were studied by SEM and XRD. The results show that the bleeding rate of slurry containing activator fly ash system is between 2.24% and 3.37%, which is much higher than that of pure cement slurry (9.25%). Therefore, the addition of this system can improve the fluidity of slurry, and the optimal scheme is a3b2c2d2. The results show that the compressive strength of cement with activator fly ash system is much lower than that of pure cement, but the increase of strength is between 31% and 85%, which is much greater than that of pure cement (35%–46%). The optimal scheme is A2B2C3D3 or A3B2C3D3 at 3 days and A1B3C2D3 at 28 days. According to the scanning results of SEM and XRD, the addition of activator can significantly improve the hydration degree of fly ash and form a more complex network structure without obvious gap.

Monitoring the variability of cement compressive strength using Multivariate Exponentially Weighted Moving Covariance Matrix (MEWMC) control chart

Cement quality plays an important role in ensuring the infrastructure development of a nation. PT “X” is a business entity engaged in cement production. The high demand for cement has driven PT “X” to constantly improve the quality under the established standards. In general, the quality of cement is determined by the compressive strength of cement measure on the 3rd, 7th, and 28th days. In this paper, the MEWMC control chart is used to monitor the compressive strength of cement. MEWMC is an exponentially weighted control chart for monitoring the stability of the covariance matrix of a process. Using the optimum weighting value λ is 0.1 in phase two, the monitoring results show that the cement quality has been statistically controlled or there is no process shift.

Hybrid-based Deep Belief Network Model for Cement Compressive Strength Prediction

AbstractCompressive strength is one of the most important qualities of concrete, and most of the conventional regression models for predicting the concrete strength could not achieve an expected result due to the unstructured factors. Moreover, the utilization of machine learning and statistical approaches playing its vital role in predicting the concrete compressive strength based on mixture proportions accounting to its industrial importance as well. In this manner, this paper attempts to introduce a new deep learning-based prediction model that makes the prediction more accurate, hence Deep Belief Network (DBN) is used. Moreover, to make the prediction more precise, it is planned to have the fine-tuning of activation function and weights of DBN, which makes the model efficient in its performance. For this purpose, an improved optimization concept is introduced called Lion Algorithm with new Rate Evaluation, which is the modified Lion Algorithm (LA). Finally, the performance of the proposed model is evaluated over other state-of-the-art models concerning certain error analysis.

Formosa Plastics USA begins operation of new LDPE unit at Point Comfort site

The construction season is limited in northern countries due to the severe cold weather conditions and their detrimental impacts on concrete quality. Thus, there are excessive expenses required annually for insulation and energy-intensive heating systems for cold-weather concreting. This experimental study aimed to investigate the potential of using high-strength one-part alkali-activated blast furnace slag (AAS) in cold weather without the need for supplementary heating systems. Therefore, the impacts of different subzero curing temperatures on the hardened properties of one-part AAS mortar in comparison with cement mortar were assessed. After casting, mortars were immediately cured at a temperature of 23, −5, −10, and −20 °C, up to 56d. The results showed that the lower the curing temperature, the lower the UPV and compressive strength of cement and one-part AAS mortar; however when the curing period was fixed, one-part AAS mortar registered higher UPV and compressive strength than cement mortar at all curing temperatures. Owing to additional room temperature curing, the hardened properties of AAS mortar were significantly improved. The findings were further supported by microstructural and thermogravimetric analyses.

One-part alkali-activated blast furnace slag for sustainable construction at subzero temperatures

The construction season is limited in northern countries due to the severe cold weather conditions and their detrimental impacts on concrete quality. Thus, there are excessive expenses required annually for insulation and energy-intensive heating systems for cold-weather concreting. This experimental study aimed to investigate the potential of using high-strength one-part alkali-activated blast furnace slag (AAS) in cold weather without the need for supplementary heating systems. Therefore, the impacts of different subzero curing temperatures on the hardened properties of one-part AAS mortar in comparison with cement mortar were assessed. After casting, mortars were immediately cured at a temperature of 23, −5, −10, and −20 °C, up to 56d. The results showed that the lower the curing temperature, the lower the UPV and compressive strength of cement and one-part AAS mortar; however when the curing period was fixed, one-part AAS mortar registered higher UPV and compressive strength than cement mortar at all curing temperatures. Owing to additional room temperature curing, the hardened properties of AAS mortar were significantly improved. The findings were further supported by microstructural and thermogravimetric analyses.

Temperature Regulation Effect of Low Melting Point Phase Change Microcapsules for Cement Slurry in Gas Hydrate-Bearing Sediments

Since natural gas hydrates only exist stably at low temperature and high pressure, hydration heat of cement slurry is easy to cause hydrate decomposition. Therefore, low-heat cement slurry system must be used during well cementing in gas hydrate-bearing sediments. In this paper, temperature-regulated microcapsules with binary alkanes as core material and CaCO 3 as shell were prepared based on self-assembly method. In addition, the hydrophilic modified graphite was added into core material to improve the temperature sensitivity. The morphology, thermal property and hydrophilicity of microcapsules were characterized by multi-techniques.The hydration property, setting behavior and compressive strength of cement slurry/stone with microcapsules was studied. The pore distribution of cement stone was analyzed by means of micro-computed tomography (micro-CT). Moreover, the effect of cement slurry hydration on hydrate-bearing sediments was tracked by a hydrate-bearing sediments damage simulation device. Compared with standard group, maximal hydration temperature decreased 3.7 °C by adding microcapsules. The simulation trail showed that the addition of microcapsules can impede the damage to hydrate-bearing sediments which are associated with cement slurry hydrating.