scholarly journals Influence of Urena lobata Fibre Treatment on Mechanical Performance Development in Hybrid Urena lobata: Fibre/Gypsum Plaster Composites

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Jerum Biepinwoh Kengoh ◽  
Ekane Peter Etape ◽  
Beckley Victorine Namondo ◽  
Josepha Foba-Tendo ◽  
Yakum Renata Nafu ◽  
...  
Keyword(s):  
Moisture Transfer ◽  
Mechanical Performance ◽  
Autogenous Shrinkage ◽  
Nucleation Site ◽  
Lower Percentage ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Cement Composites ◽  
Cement Concrete ◽  
Performance Development

Autogenous shrinkage is related to the chemistry and changes in the internal structure of the cement concrete paste on drying. This problem of drying shrinkage in early stages that occur without any moisture transfer to the surrounding environment has triggered the incorporation of fibres in the cement concrete matrix to fill the micropores and control cracking (autogenous shrinkage). This study aimed at investigating the potential use of Urena lobata (UL) fibre as microreinforcement in enhancing mechanical properties of hybrid UL-fibre/gypsum cement composites used for plasters. The fibre was harvested from the coastal region of Cameroon and treated with 0.06 M NaOH over different periods. Dispersion of treated fibre bundles in the composite (at Wt. % UL-fibre dosages of 0, 1.5, 2.5, and 3.5) was facilitated by blending with the cement paste which also helped to improve interfacial bonding between the fibre and the cement matrix. The moisture/water absorption and flexural properties within the hardened cement matrix were quantitatively assessed, and it was observed that the incorporation of treated fibre accelerated the hydration process. The test results showed an increment in compressive strength and reduction in autogenous shrinkage for the hybrid UL fibre/gypsum cement composites, while lower percentage additions (less than 2.5%) of untreated fibre appeared to have adverse effects on specimens. It was observed that properly dispersed (blended) treated UL fibres filled the fine pores in the cement matrix by providing an additional nucleation site that resulted in a denser microstructure, which in turn enhanced the strengths and limited the autogenous shrinkage.

Research on Properties of Low Grade Cement-Based Composite Materials Modified by Silica Fume

2012 ◽  
Vol 174-177 ◽  
pp. 751-756
Author(s):  
Zi Fang Xu ◽  
Ming Xu Zhang ◽  
Jin Hua Li
Keyword(s):  
Silica Fume ◽  
Mechanical Performance ◽  
Raw Materials ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Low Grade ◽  
X Ray ◽  
Matrix Microstructure ◽  
Nano Powder ◽  
Strength And Durability

In order to notably improve the mechanical properties and durability of low-grade cement-based material, superfine silica fume was used to modify the cement-based composite based on special perfomance and effects of nano powder. The mechanical performance and durability were investigated.Then the phase compositions,microstructure and morphologies of as-received cement-based composite were studied by X-ray Diffractometer、TGA-DTA and SEM. The results show that： the best formula of raw materials is 1:1:0.025:0.015, and hydration can be accelerated and increasing of hydration products is observed after modification. In the hardened cement matrix, microstructure is very compacted and C-S-H gel forms densed structure, so the structure defect is notably reduced. This means that both strength and durability of cement-based composite are notably improved by the addition of superfine silica fume.

scholarly journals Influence of Dispersing Method on the Quality of Nano-Admixtures Homogenization in Cement Matrix

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4865
Author(s):  
Elżbieta Horszczaruk ◽  
Paweł Łukowski ◽  
Cyprian Seul
Keyword(s):  
High Speed ◽  
Mechanical Performance ◽  
Chemical Properties ◽  
Cement Composite ◽  
Cement Matrix ◽  
Cement Composites ◽  
Nano Sio2 ◽  
Mechanical Stirring ◽  
Physico Chemical ◽  
Nano Fe3o4

In recent years, a nano-modification of the cement composites allowed to develop a number of new materials. The use of even small amount of nano-admixture makes possible not only to improve the physico-mechanical properties of the cement materials, but also to obtain the composite with high usability, optimised for the given application. The basic problem of nano-modification of the cement composites remains the effectiveness of dispersing the nanomaterials inside the cement matrix. This paper deals with the effect of the type and size of the nanoparticles on the tendency to their agglomeration in the cement matrix. The main techniques and methods of dispersing the nanomaterials are presented. It has been demonstrated, on the basis of the results of testing of three nanomodifiers of 0D type (nano-SiO2, nano-Fe3O4 and nano-Pb3O4), how the structure and properties of the nanomaterial affect the behaviour of the particles when dissolving in the mixing water and applying a superplasticiser. The nanoparticles had similar size of about 100 nm but different physico-chemical properties. The methods of dispersing covered the use of high-speed mechanical stirring and ultrasonication. The influence of the method of nano-modifier dispersing on the mechanical performance of the cement composite has been presented on the basis of the results of testing the cement mortars modified with 3% admixture of nano-SiO2.

scholarly journals On effect of superplasticizers and mineral additives on shrinkage of hardened cement paste and concrete

2018 ◽  
Vol 196 ◽  
pp. 04018 ◽  
Author(s):  
Grigory Nesvetaev ◽  
Yulia Koryanova ◽  
Tatiana Zhilnikova
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Hardened Cement ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Hardened Cement Paste ◽  
Mineral Additive ◽  
Mineral Additives

A model describing the variation in autogenous shrinkage and drying shrinkage of portland cement concrete, depending on the volume of aggregates and the shrinkage of hardened cement paste, is presented. The equation to calculate shrinkage of concrete as a function of the volume of aggregates and shrinkage of a hardened cement paste was proposed. Formulas are proposed that describe the change in the shrinkage of hardened cement paste as a function of water/cement. The results of studies of the effect of superplasticizers and mineral additives on the autogenous shrinkage and the drying shrinkage of hardened cement paste are presented. Concretes made with superplasticizer and mineral additive may have the potential lower the value of drying shrinkage. The shrinkage value can be lowered from 30% till 70%. Concretes containing superplasticizers and mineral additives can potentially have the autogenous shrinkage reduced to 75%, or increased to 180%.

scholarly journals Effect of Nano-SiO2 on the Microstructure and Mechanical Properties of Concrete under High Temperature Conditions

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 166
Author(s):  
Piotr Brzozowski ◽  
Jarosław Strzałkowski ◽  
Piotr Rychtowski ◽  
Rafał Wróbel ◽  
Beata Tryba ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Coarse Aggregate ◽  
Mechanical Performance ◽  
Mercury Porosimetry ◽  
Thermal Characteristics ◽  
Total Porosity ◽  
Cement Matrix ◽  
Cement Concrete ◽  
Structural Tests

The aim of the research was to determine how the admixture of nanosilica affects the structure and mechanical performance of cement concrete exposed to high temperatures (200, 400, 600, and 800 °C). The structural tests were carried out on the cement paste and concrete using the methods of thermogravimetric analysis, mercury porosimetry, and scanning electron microscopy. The results show that despite the growth of the cement matrix’s total porosity with an increasing amount of nanosilica, the resistance to high temperature improves. Such behavior is the result of not only the thermal characteristics of nanosilica itself but also of the porosity structure in the cement matrix and using the effective method of dispersing the nanostructures in concrete. The nanosilica densifies the structure of the concrete, limiting the number of the pores with diameters from 0.3 to 300 μm, which leads to limitation of the microcracks, particularly in the coarse aggregate-cement matrix contact zone. This phenomenon, in turn, diminishes the cracking of the specimens containing nanosilica at high temperatures and improves the mechanical strength.

Enhancement of Physico-Mechanical Characteristics of Graphene Nano Sheets Reinforced Cement

2018 ◽  
Vol 6 (8) ◽  
pp. 79
Author(s):  
M. M. Mokhtar ◽  
S. A. Abo-El-Enein ◽  
M. Y. Hassaan ◽  
M. S. Morsy ◽  
M. H. Khalil
Keyword(s):  
Mechanical Characteristics ◽  
Nitrogen Adsorption ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Cement Composites ◽  
Gravimetric Analysis ◽  
Electrical Characteristics ◽  
Phase Decomposition ◽  
Reinforced Cement ◽  
Consequent Improvement

Graphenenanosheets(GNSs) have unique physical properties that make them effective reinforcing materials. The attractive properties of graphene have led to enhance the graphene-polymer nanocomposites. This study investigates the effect of (GNSs) reinforcement on mechanical properties, pore structure and electrical characteristics of the hardened cement composites. GNSwere addedat different percentages of 0, 0.01, 0.02, 0.03, 0.04 and 0.05 wt. % of cement. Compressivestrengthwas determined at 28 days of curing.Thermo-gravimetric analysis (TGA)was used to detect the phase decomposition, the pore structurewas studied using nitrogen adsorption at 77.35°K technique,the microstructure wasexamined using scanning electron microscopy (SEM), and finally, electrical conductivity of graphene-cement composites was also studied. Results revealed that, considerable enhancements in compressive strengths by about 33%have been achieved by incorporating GNSs into cement matrix by about 0.04%.The integration of graphene into cement has significantly reduced the pore size of thepastes and led to a considerable improvement in the microstructure, with a consequent improvement in the electricalconductivity of these composites.

Numerical-Experimental Assessment of the Arumã Fiber as Reinforcement to the Cementitious Matrix

2014 ◽  
Vol 600 ◽  
pp. 460-468
Author(s):  
Maria Gorett dos Santos Marques ◽  
João de Almeida Melo Filho ◽  
Julio Cesar Molina ◽  
Romildo Dias Toledo Filho ◽  
Raimundo Pereira de Vasconcelos ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Mechanical Performance ◽  
Experimental Tests ◽  
Cement Composite ◽  
Cement Matrix ◽  
Cement Composites ◽  
Experimental Assessment ◽  
Bending Tests ◽  
The Family ◽  
The Matrix

Composites of high mechanical performance reinforced by fibers need a well set arrangement of them in the matrix so that under reinforcement which they can be submitted, a desirable performance can be shown. Thus, the cement composite studied has a cement matrix which received a reinforcement made by arumã fibers, shaped in bidirectional frames distributed in three layers. Arumã is a typical plant from the Amazon, species from the genus Ischnosiphon polyphyllus, part of the family Marantaceae. This study had the purpose of assessing the cement composites mechanical behaviour from the bending tests in four points and puncture tests in sheets which were supported by the four edges. Having presented mechanical results, a numerical simulation was made through the SAP2000 NonLinear® software, with the aim to obtain a numerical computational model able to represent the composites behaviour up to the point where the loading reaches the greatest amount. The numerical results present a good correlation with those obtained in the experimental tests.

scholarly journals Preparation and Mechanical Properties of Graphene Oxide: Cement Nanocomposites

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Fakhim Babak ◽  
Hassani Abolfazl ◽  
Rashidi Alimorad ◽  
Ghodousi Parviz
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Graphene Oxide ◽  
Cement Mortar ◽  
Cement Matrix ◽  
Cement Composites ◽  
Xrd Diffraction ◽  
Calcium Silicate Hydrates ◽  
The Matrix ◽  
Scanning Electron

We investigate the performance of graphene oxide (GO) in improving mechanical properties of cement composites. A polycarboxylate superplasticizer was used to improve the dispersion of GO flakes in the cement. The mechanical strength of graphene-cement nanocomposites containing 0.1–2 wt% GO and 0.5 wt% superplasticizer was measured and compared with that of cement prepared without GO. We found that the tensile strength of the cement mortar increased with GO content, reaching 1.5%, a 48% increase in tensile strength. Ultra high-resolution field emission scanning electron microscopy (FE-SEM) used to observe the fracture surface of samples containing 1.5 wt% GO indicated that the nano-GO flakes were well dispersed in the matrix, and no aggregates were observed. FE-SEM observation also revealed good bonding between the GO surfaces and the surrounding cement matrix. In addition, XRD diffraction data showed growth of the calcium silicate hydrates (C-S-H) gels in GO cement mortar compared with the normal cement mortar.

scholarly journals Application of the nanoindentation method in assessing of properties of cement composites modified with silica-magnetite nanostructures

2018 ◽  
Vol 163 ◽  
pp. 02002 ◽  
Author(s):  
Elzbieta Horszczaruk ◽  
Roman Jedrzejewski ◽  
Jolanta Baranowska ◽  
Ewa Mijowska
Keyword(s):  
Mechanical Properties ◽  
Magnetite Nanoparticles ◽  
Positive Influence ◽  
Cement Matrix ◽  
Core Shell ◽  
Indentation Modulus ◽  
Cement Composites ◽  
Interfacial Zone ◽  
Berkovich Indenter ◽  
The Core

The results of investigation of the cement composites modified with 5% of silica-magnetite nanostructures of the core-shell type are presented in the paper. The nanoindentation method employing three-sided pyramidal Berkovich indenter was used in the research. The mechanical properties and microstructure of the modified cement composites were evaluated on the basis of the values of hardness and indentation modulus measured inside the cement matrix and in the aggregate-paste interfacial zone. The results were compared with those obtained for the reference composites without nanostructures. The positive influence of the presence of silica-magnetite nanoparticles on the tested properties was found out.

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