The Effect of Modified Straw on Microstructure of Soil Consolidation Material

2012 ◽  
Vol 557-559 ◽  
pp. 904-908
Author(s):  
Liang Yan ◽  
Xiu Li Zhang
Keyword(s):  
Wheat Straw ◽  
Cement Paste ◽  
Interfacial Adhesion ◽  
Cement Hydration ◽  
Hardened Cement ◽  
Soil Consolidation ◽  
Fracture Elongation ◽  
Mass Fractions ◽  
Reinforced Cement ◽  
Consolidation Material

The application of wheat straw fiber reinforced cement-based composites (WFCC) was restricted because of the poor mechanical properties and lots of extractives of wheat straw in cement paste. In order to overcome the natural defects, the wheat straw was modified respectively by different mass fractions of NaOH, Na2SiO3and H3PO4solutions. The results show that, the various indexes of wheat straw fiber soaked by NaOH solutions (mass fraction 5%) for 12 hours were optimal. Moreover, its ultimate tensile strength and fracture elongation were respectively increased by 104.81% and 78.57%. Meanwhile, the modified fiber bundles arranged densely without damage phenomenon in WFCC, and surface of fiber was covered in massive cement hydration products, and the interfacial adhesion between fiber and hardened cement paste was improved.

scholarly journals The Effects of Nanosized-Palm Oil Fuel Ash on Early Age Hydration of Hardened Cement Paste: The Microstructure Studies

2021 ◽  
Vol 82 (2) ◽  
pp. 87-95
Author(s):  
Mohd Azrul Andul Rajak ◽  
Zaiton Abdul Majid ◽  
Mohammad Ismail
Keyword(s):  
Cement Paste ◽  
Palm Oil ◽  
Cement Hydration ◽  
Pozzolanic Reaction ◽  
Early Age ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Palm Oil Fuel Ash ◽  
Fuel Ash ◽  
Oil Fuel

Integration of cement-based products with nanosized-palm oil fuel ash as supplementary cementing material (SCM) amend its hydration’s degree at early age phase and the microstructural groundworks are relevant to explain the findings. Hence, the present work investigates the microstructure properties of the hardened cement paste (HCP) incorporating nPOFA to study on the effect of nPOFA in cement hydration at an early age phase. An Ordinary Portland Cement (OPC) paste as a set of HCP blended with microsized-palm oil fuel ash (mPOFA) (10-30%) and nPOFA (10-60%) were prepared and cured for 28 days. The microstructural examination of OPC, mPOFA and nPOFA cement pastes at 28 days curing age via Thermogravimetric (TG) analysis, X-Ray diffraction (XRD) analysis, morphology study and Fourier transform infrared (FTIR) spectroscopy analysis. In TG analysis, the relative weight loss of calcium hydroxide (CH) of nPOFA pastes is lower than OPC and mPOFA. Based on the CH peaks at 2?= 18.1°and 34.0° in the diffractogram, it shows that nPOFA pastes give the low CH peaks compare to OPC and mPOFA pastes. In addition, the nPOFA pastes form the dense and compact microstructure of HCP compare to other pastes. Observations from FTIR analysis, nPOFA pastes display a high frequency of Si-O band due to the high rate of pozzolanic reaction. Overall, the findings confirmed the contribution of nPOFA in accelerating the rate of cement hydration and pozzolanic reaction as it reduced the amount of CH in the cementitious matrix.

Thermodynamic Interpretation of Carbonation Process of Portland Cement Hydration Products

2013 ◽  
Vol 753-755 ◽  
pp. 543-557
Author(s):  
Yan Jun Liu ◽  
Bo Tian Chen ◽  
Yong Chao Zheng
Keyword(s):  
Carbon Dioxide ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Cement Paste ◽  
Cement Hydration ◽  
Hardened Cement ◽  
Hydration Products ◽  
Hardened Cement Paste ◽  
Equilibrium Pressure ◽  
Carbonation Process

Cement hydration products carbonation is not only blamed for the carbonation-induced hardened cement paste or concrete cracking, also attributed to the pore water PH-value decrease, which causes the reinforcement corrosion under the existence of water and oxygen due to removal of oxide film passivating rebar surface, in hardened cement paste and concrete. Based on chemical thermodynamics, this paper presents the susceptibility of different cement hydration products to carbonation through calculating their Standard Gibbs Free Energy respectively, Gibbs free energy under temperature variation and the minimum equilibrium pressure of carbon dioxide triggering the carbonation process. The calculated results show that, under standard state (25°C, 100kpa), the minimum equilibrium pressure of carbon dioxide triggering carbonation process is significantly variable for different types of cement hydration products. For example, mono-sulfate sulfoferrite hydrates (3CaOFe2O3CaSO412H2O) is the most susceptible to carbonation, followed by mono-sulfate aluminate hydrates (3CaOAl2O3CaSO412H2O), while multi-sulfate sulfoaluminate hydrates (3CaOAl2O33CaSO432H2O) is the least vulnerable to carbonation, followed by silicate hydrates (5CaO6SiO25.5H2O). The findings in this paper are significant in understanding thermodynamic mechanism of cement hydrates carbonation and seeking the solution to prevent cement hydrates from carbonation-induced deterioration.

scholarly journals Effect of Ultrafine Additives on the Morphology of Cement Hydration Products

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1002
Author(s):  
Grigory Yakovlev ◽  
Rostislav Drochytka ◽  
Gintautas Skripkiunas ◽  
Larisa Urkhanova ◽  
Irina Polyanskikh ◽  
...  
Keyword(s):  
Silica Fume ◽  
Cement Paste ◽  
Cement Hydration ◽  
Chemical Reactivity ◽  
Xrd Analysis ◽  
Hardened Cement ◽  
Hydration Products ◽  
Hardened Cement Paste ◽  
X Ray ◽  
Strong Adhesion

The present research is focused on the investigation of the influence of ultrafine additives on the structure formation of hardened cement paste and the establishment of the mechanisms of the morphological transformations, which determine the properties of hydrated products. In the course of the research, the modification of ordinary Portland cement was performed by the suspension of multi-walled carbon nanotubes (MWCNTs), carbon black (CB) paste, and silica fume (SF). Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD) analysis, thermal analysis, and Fourier-transform infrared (FTIR) spectroscopy were used to study cement hydration products. The morphology of hardened cement paste depends on the chemical reactivity of additives, their geometry, and their genesis. The action mechanism of the inert carbon-based additives and pozzolanic silica fume were considered. The cement hydration products formed in the process of modification by both types of ultrafine additives are described. In the case of the modification of cement paste by inert MWCNTs and CB paste, the formation of cement hydration products on their surface without strong adhesion was observed, whereas in the case of the addition of SF separately and together with MWCNTs, the strong adhesion of additives and cement hydration products was noted.

Composite materials based on cement matrices

1983 ◽  
Vol 310 (1511) ◽  
pp. 191-202 ◽  
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Cement Paste ◽  
Metal Wire ◽  
Hardened Cement ◽  
Paper Briefly ◽  
Hardened Cement Paste ◽  
Recent Developments ◽  
Reinforced Cement ◽  
Cement And Concrete

All materials produced from inorganic hydraulic cements are composites of one kind or another because of their multiphase nature. This paper briefly considers the relevance of composite principles in predicting the mechanical properties of hardened cement paste, mortar and concrete and then discusses recent developments towards enhancing these properties by the addition of polymers and more particularly fibres. Fibres derived from glass, polypropylene and cellulose with metal wire are currently being used as cement reinforcements. Important properties of some of these practical fibre reinforced cement and concrete (F.R.C.) materials are discussed with particular reference to the replacement of asbestos products. Some examples of recent innovations in the manufacture of F.R.C. materials are given together with projections for their future use.

Hydration and Microstructure of Nano Modified Cement Paste

2021 ◽  
Vol 321 ◽  
pp. 9-14
Author(s):  
Gintautas Skripkiūnas ◽  
Ekaterina Karpova ◽  
Rostislav Drochytka ◽  
Jakub Hodul
Keyword(s):  
Cement Paste ◽  
Cement Hydration ◽  
Aqueous Suspension ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Cement Pastes ◽  
Microstructure Observation ◽  
Multi Walled Carbon Nanotubes ◽  
Hardened Cement Pastes ◽  
Walled Carbon Nanotubes

Hydration of cement systems modified by nano additives requires the understanding of its mechanisms. The present research is focused on the investigation of hydration processes in cement pastes modified by multi-walled carbon nanotubes (MWCNTs) suspension. The ultrasonication method was used for homogenization of MWCNTs in the volume of an aqueous suspension. The hydration of cement pastes was assessed by the calorimetry test. The prolongation of cement hydration in case of modification by MWCNT suspension was observed. The microstructure observation by scanning electron microscopy (SEM) was performed for identification of MWCNT's dispergation in hardened cement pastes and for the observation of cement hydration products. The compressive and flexural strength were tested to evaluate the effect of MWCNT on mechanical properties of hardened cement paste.

The Combined Effect of the Plasticizer and Multi-Walled Carbon Nanotubes on the Cement Hydration Products

2018 ◽  
Vol 276 ◽  
pp. 21-26
Author(s):  
Gintautas Skripkiūnas ◽  
Grigory Ivanovich Yakovlev ◽  
Ekaterina Karpova ◽  
Anastasiia Gordina ◽  
Arina Shaybadullina
Keyword(s):  
Carbon Nanotubes ◽  
Cement Paste ◽  
Cement Hydration ◽  
Hardened Cement ◽  
Hydration Products ◽  
Hardened Cement Paste ◽  
Physico Chemical ◽  
Cement System ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

There are many research devoted to the influence of carbon nanotubes (CNT) on the structure and properties of cement systems. In the course of this research, the combined influence of of multi-walled carbon nanotubes (MWCNT) and polycarboxylate (PCE) plasticizer on the products of hydration and the properties of hardened cement paste was investigated. The strength characteristics of nanomodified hardened cement paste and the hydration products were determined by the usage of modern methods of physico-mechanical and physico-chemical analyses. Based on the physico-chemical investigations, it was concluded the necessity of additional experiments, associated primary with questions of uniform distribution of the nanostructures and their chemical interactions with another components of admixture and cement system.

scholarly journals COMPLEX ADMIXTURES FOR HIGH-STRENGTH CONCRETE

2002 ◽  
Vol 8 (4) ◽  
pp. 276-280 ◽  
Author(s):  
Gintautas Skripkiūnas ◽  
Žymantas Rudžionis ◽  
Vitoldas Vaitkevičius
Keyword(s):  
Silica Fume ◽  
Cement Paste ◽  
High Strength Concrete ◽  
Cement Hydration ◽  
High Strength ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Strength Concrete ◽  
Concrete Production ◽  
Paste Properties

The influence of naphthalene formaldehyde superplasticizers (NFS), lignosulfonate plasticizers (LSP) and silica fume on cement paste properties and complex usage of these admixtures for high-strength concrete production are investigated in this research. These admixtures influence the cement hydration products morphology and properties of hardened cement paste. The degree of cement hydration and Ca(OH)2 content in hardened cement paste were determined for analysis of cement hydration process with admixtures. Mechanical properties and porosity of hardened cement paste with the admixtures were tested. Optimal dosages of plasticizing admixtures and silica fume were estimated and the most efficient method of silica fume adding to concrete mixture was proposed. The results of investigation have been used for high-strength concrete production.

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