Setting and Strengthening Mechanisms of Cementitious Materials

1991 ◽  
Vol 245 ◽  
Author(s):  
W. Jiang ◽  
D.M. Roy
Keyword(s):  
Mechanical Properties ◽  
Setting Time ◽  
Construction Materials ◽  
Cementitious Materials ◽  
Cement Matrix ◽  
Chemical Characteristics ◽  
Strengthening Mechanisms ◽  
Portland Cements ◽  
Dental Cement ◽  
Physico Chemical

ABSTRACTThis paper highlights the physico-chemical characteristics of cementitious materials responsible for or involved in setting, and how these are related to the strengthening and mechanical properties. Five main mechanisms which can be used to increase cementitious materials strength were discussed. The substantially improved cement matrix materials can be obtained by deliberately using one or more above mechanisms. Experiments have been performed on ordinary portland cements and phosphate cements used as construction materials, whose setting time is several hours, and dental cement, whose setting time is several minutes.

scholarly journals Effect of TiO2 Nanoparticles on Physical and Mechanical Properties of Cement at Low Temperatures

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Li Wang ◽  
Hongliang Zhang ◽  
Yang Gao
Keyword(s):  
Mechanical Properties ◽  
Low Temperatures ◽  
Cement Hydration ◽  
Setting Time ◽  
Physical And Mechanical Properties ◽  
Xrd Analysis ◽  
Cementitious Materials ◽  
Strength Test ◽  
Hydration Degree ◽  
Time Test

Low temperature negatively affects the engineering performance of cementitious materials and hinders the construction productivity. Previous studies have already demonstrated that TiO2 nanoparticles can accelerate cement hydration and enhance the strength development of cementitious materials at room temperature. However, the performance of cementitious materials containing TiO2 nanoparticles at low temperatures is still unknown. In this study, specimens were prepared through the replacement of cement with 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, and 5 wt.% TiO2 nanoparticles and cured under temperatures of 0°C, 5°C, 10°C, and 20°C for specific ages. Physical and mechanical properties of the specimens were evaluated through the setting time test, compressive strength test, flexural strength test, hydration degree test, mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) analysis, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) in order to examine the performance of cementitious materials with and without TiO2 nanoparticles at various curing temperatures. It was found that low temperature delayed the process of cement hydration while TiO2 nanoparticles had a positive effect on accelerating the cement hydration and reducing the setting time in terms of the results of the setting time test, hydration degree test, and strength test, and the specimen with the addition of 2 wt.% TiO2 nanoparticles showed the superior performance. Refined pore structure in the MIP tests, more mass loss of CH in TGA, intense peak appearance associated with the hydration products in XRD analysis, and denser microstructure in SEM demonstrated that the specimen with 2 wt.% TiO2 nanoparticles exhibited preferable physical and mechanical properties compared with that without TiO2 nanoparticles under various curing temperatures.

Modified Plasters for Restoration and Finishing Works

2014 ◽  
Vol 923 ◽  
pp. 42-47 ◽  
Author(s):  
Myroslav Sanytsky ◽  
Tetiana Kropyvnytska ◽  
Roman Kotiv
Keyword(s):  
Compressive Strength ◽  
Chemical Composition ◽  
Cementitious Materials ◽  
Quality Parameters ◽  
Supplementary Cementitious Materials ◽  
Cement Matrix ◽  
Hydration Products ◽  
High Quality ◽  
Physico Chemical ◽  
White Portland Cement

The paper is devoted to the research and development of modified plasters for restoration and finishing works based on decorative multicomponent cements containing white Portland cement and supplementary cementitious materials (silica fume, metakaolin and fine ground limestone). This cements are similar to Roman cement by their chemical composition. The use of optimal granulometry of decorative multicomponent cements provide directed formation of microstructure of the cement matrix with the formation of stable hydration products. Compositions of modified plasters by the criterions of workability and compressive strength were designed. Physico-chemical modification of plaster by complex air-entraining admixture allows to obtain high-quality modified plasters with improved quality parameters.

scholarly journals Effect of nano-silica as cementitious materials-reducing admixtures on the workability, mechanical properties and durability of concrete

2021 ◽  
Vol 10 (1) ◽  
pp. 1395-1409
Author(s):  
Changjiang Liu ◽  
Xin Su ◽  
Yuyou Wu ◽  
Zhoulian Zheng ◽  
Bo Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Building Materials ◽  
Setting Time ◽  
Microscopic Analysis ◽  
Chloride Ion ◽  
Cementitious Materials ◽  
Hydration Reaction ◽  
Ion Permeability ◽  
Nano Silica ◽  
Durability Of Concrete

Abstract Nano-silica (NS) is one of the most important nanomaterials in recent years. It is used as a new cement-based composite reinforcement in building materials because of its high volcanic ash activity. In order to achieve the goal of carbon peaking and carbon neutralization, combined with the research idea of cementitious materials-reducing admixture for concrete, under the condition of reducing the amount of cement in concrete by 20%, the influence of different dosages of NS on the setting time and mechanical properties of concrete was analyzed. In addition, the shrinkage performance, impermeability, and resistance to chloride-ion permeability of concrete were also studied. The results show that under the same curing conditions and ages, when the NS dosage is 2.5%, the compressive strength and splitting tensile strength of the specimen after 28 days of curing are the highest, reaching 40.87 and 3.8 MPa, which show an increase by 6.6 and 15.15%. The shrinkage performance of concrete increases with the increase in NS dosage. In addition, when the NS dosage is 2.0%, the durability of concrete has also been greatly improved. The impermeability of concrete increased by 18.7% and the resistance to chloride-ion permeability increased by 14.7%. Through microscopic analysis it was found that NS can promote the hydration reaction, generate more hydration products such as calcium silicate hydrate (C–S–H), enhance the interfacial adhesion between the matrix and the aggregate, and form a closer interfacial transition zone. Moreover, the addition of NS also reduces the cumulative pore volume in concrete, refines the pore size, and makes the internal structure of concrete denser.

scholarly journals Performance and Durability of Rendering and Basecoat Mortars for ETICS with CSA and Portland Cement

2021 ◽  
Vol 6 (4) ◽  
pp. 60
Author(s):  
Tiago Trigo ◽  
Inês Flores-Colen ◽  
Luís Silva ◽  
Nuno Vieira ◽  
Ana Raimundo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Energy Consumption ◽  
Portland Cement ◽  
Bending Strength ◽  
Setting Time ◽  
Cement Matrix ◽  
Calcium Sulfoaluminate Cement ◽  
Calcium Sulfoaluminate ◽  
Composite Systems

The production of Portland cement (OP) is commonly associated to significant level of energy consumption and gas emissions. The use of calcium sulfoaluminate cement (CSA) can be a sustainable alternative binder, since its production releases about half of the CO2 emissions and its clinker requires 200 °C lower temperatures, when compared to OP. Furthermore, CSA has fast setting time and achieves higher strength in shorter periods, as well as reduced shrinkage. This paper discusses the incorporation of CSA in rendering mortars and basecoat mortars for ETICS (External Thermal Insulation Composite Systems). The physical-mechanical properties of mortars made with OP and CSA cements were experimental evaluated. The results showed that the introduction of CSA generally improves shrinkage, compressive strength, water absorption at low pressure, enhances the tensile bending strength and decreases the setting time. The amount of CSA introduced into the mixture significantly affected the properties of the cement matrix.

scholarly journals Application of PET/Sepiolite Nanocomposite Trays to Improve Food Quality

Foods ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1188
Author(s):  
Teresa Fernández-Menéndez ◽  
David García-López ◽  
Antonio Argüelles ◽  
Ana Fernández ◽  
Jaime Viña
Keyword(s):  
Mechanical Properties ◽  
Food Quality ◽  
Barrier Properties ◽  
Packaging Material ◽  
The Other ◽  
Chemical Characteristics ◽  
Microbiological Characteristics ◽  
Physico Chemical ◽  
Food Needs ◽  
Lower Count

New PET and nanosepiolite materials are produced for its application in innovative packaging with better performance. In our previous work, we demonstrate that the use of different percentages of sepiolite modified with different organosilanes improved mechanical and barrier properties of PET. Nanocomposites permeability can decrease up to 30% compared to that of pure PET and the mechanical analyses show that, although PET nanocomposites are more brittle than virgin PET, they are also harder. In the present work, we are going to study the properties of this innovative packaging with real food analyzing mechanical properties related to the product transport together with permeability and microbiological characteristics. At the same time, it has been seen that it is possible to lighten trays, which is very important both industrially and environmentally. On the other hand, a good quality packaging for food needs to ensure that organoleptic and physico-chemical characteristics of the product inside are not modified due to migration of any of the packaging material to the food itself. Results obtained in this work also show lower count of aerobic mesophilic bacteria and Enterobacteriaceae (EB), reducing the incidence of food contaminations by microorganisms.

Non-Destructive Characterization of Cement Materials Using Ultrasonic Method - Application to the Study of Carbonation

2014 ◽  
Vol 1065-1069 ◽  
pp. 1791-1794 ◽  
Author(s):  
Son Tung Pham
Keyword(s):  
Mechanical Properties ◽  
Ultrasonic Method ◽  
Construction Materials ◽  
Young Modulus ◽  
Cementitious Materials ◽  
Margin Of Error ◽  
Before And After ◽  
Non Destructive ◽  
Non Destructive Characterization

The objective of this study is to realize a non-destructive characterization of cementitious materials using ultrasonic method. The motivation of our work is to show that the ultrasound can be applied not only in medical imaging but also in the assessment of construction materials, which is not widely known in this domain. In order to solve the problem, the ultrasonic velocity measurement was performed on the samples before and after carbonation of a standardized mortar at different periods. The results offer the possibility to determine the mechanical properties such as Young modulus E, shear modulus G and Poisson's ratio. This is an advantage for in-situ structures in comparison with destructive methods that require destroying the samples. The main contributions of this study are: 1) Ultrasonic occultation of cement materials is a reliable method with a small margin of error; 2) The values ​​of mechanical properties found by ultrasonic method are consistent with theoretical values ​​found in the literature; 3) The evolution of these mechanical properties is consistent with the densification of the microstructure during carbonation due to the formation of CaCO3.

scholarly journals Photocatalytic Activity and Mechanical Properties of Cements Modified with TiO2/N

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3756 ◽  
Author(s):  
Magdalena Janus ◽  
Szymon Mądraszewski ◽  
Kamila Zając ◽  
Ewelina Kusiak-Nejman ◽  
Antoni W. Morawski ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Photocatalytic Activity ◽  
Building Materials ◽  
Cement Content ◽  
Setting Time ◽  
Cement Matrix ◽  
Final Setting Time ◽  
Cement Mortars ◽  
Fresh State ◽  
Positive Effect

In this paper, studies of the mechanical properties and photocatalytic activity of new photoactive cement mortars are presented. The new building materials were obtained by the addition of 1, 3, and 5 wt % (based on the cement content) of nitrogen-modified titanium dioxide (TiO2/N) to the cement matrix. Photocatalytic active cement mortars were characterized by measuring the flexural and the compressive strength, the hydration heat, the zeta potential of the fresh state, and the initial and final setting time. Their photocatalytic activity was tested during NOx decomposition. The studies showed that TiO2/N gives the photoactivity of cement mortars during air purification with an additional positive effect on the mechanical properties of the hardened mortars. The addition of TiO2/N into the cement shortened the initial and final setting time, which was distinctly observed using 5 wt % of the photocatalyst in the cement matrix.

scholarly journals Design and predicting performance of carbon nanotube reinforced cementitious materials : mechanical properties and dipersion characteristics.

2020 ◽  
Author(s):  
Mahyar Ramezani
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Aspect Ratio ◽  
Flexural Strength ◽  
Experimental Test ◽  
Cementitious Materials ◽  
Matrix Composition ◽  
Cement Matrix ◽  
Test Results ◽  
Cement Ratio

Recently, Carbon Nanotubes (CNTs) are drawing considerable attention of researchers for reinforcing cementitious materials due to their excellent mechanical properties and high aspect ratio (length-to-diameter ratio). However, CNTs might not disperse well within the cement matrix, resulting in little improvement or even degradation of concrete properties. The uncertainty in producing the consistent results in different studies might be attributed to multiple interactions between the experimental variables affecting the nanotube dispersion and the final properties of CNT-cement nanocomposites. Therefore, this research mainly focused on proposing equations that can reliably capture these interactions in order to correlate CNT dispersion with the mechanical properties. The main experimental variables studied included CNT concentration, aspect ratio, ultrasonication energy, ultrasonication amplitude, surfactant-to-CNTs ratio, water-to-cement ratio, sand-to-cement ratio, and hydration age of specimen. The study reported in this research was conducted in two parts: experimental program and modeling. In the experimental part of this research, a total of 63 different mix proportions were used to evaluate the flowability, mechanical properties, and durability characteristics of cement pastes and mortars containing CNTs. Using experimental test results reported in this study and the literature, three critical relations were proposed to consider the CNT dispersion, cement matrix composition, and hydration age of cement. The proposed critical relations were then added to available theoretical models in the literature. The flexural strength and elastic modulus of CNT-cement nanocomposites were predicted through a state-of-the-art probabilistic model using a Bayesian methodology. Finally, the developed probabilistic models were used to identify the optimum ranges of the experimental variables to maximize the mechanical properties. This was done through computing the conditional probability of not meeting the specified design requirement. The experimental results indicated that addition of CNTs could significantly improve different properties of cementitious materials, if the optimum range of each variable was used. Also, to achieve the desired mechanical properties, various combinations of the experimental variables might be used. The proposed prediction models were shown to capture the interactions between the experimental variables for predicting the mechanical properties within ±15% and ±18% of the experimental test results for flexural strength and elastic modulus, respectively. Based on the findings of this research, contour plots were developed to provide practical guidelines for future engineers to design CNT-cement nanocomposites.

scholarly journals A review of the effect and optimization of use of nano-TiO2 in cementitious composites

2022 ◽  
Author(s):  
Mahmud Sami Döndüren ◽  
◽  
Mohammed Gamal Al-Hagri ◽  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Setting Time ◽  
Cementitious Materials ◽  
Partial Replacement ◽  
Cementitious Composites ◽  
Nano Materials ◽  
Microstructural Properties ◽  
Nano Tio2 ◽  
Cement Based Materials

There are some problems and weaknesses related to cement-based materials, such as their very low tensile strength, low chemical resistance and the huge contribution of cement production to industrial CO2 emissions. One possible method to reduce the impacts of such problems is the partial replacement of cement in cementitious materials with nano materials. This work provides a detailed review of incorporation of one of the most widely used nano materials, namely nano-titanium dioxide, and its effect on the properties of cementitious composites. Different properties have been considered in the current study, such as fresh properties, mechanical properties (compressive strength, split tensile strength and flexural strength), durability (permeability, ultrasonic pulse velocity (UPV), electrical resistivity, carbonation resistance, freeze and thaw resistance and sulfate attack resistance) and microstructural properties. This paper also investigates the optimum content of nano-TiO2 in cement-based materials. Moreover, the cost effectiveness of use on nano-titania in cementitious composites has been discussed. Nano titania reduces the workability and setting time of cement-based materials. It can be very effective in improving the mechanical properties, durability and microstructural properties of cementitious composites.

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