Effect of Different Molecular Weights and Chemical Composition of Superplasticizers on the Structural Build-up of Cement Paste Using Dynamic Oscillatory Rheology

2019 ◽  
pp. 192-199
Author(s):  
Nonkululeko W. Radebe ◽  
Christopher O. Klein ◽  
Lei Lei ◽  
Manfred Wilhelm
Keyword(s):  
Chemical Composition ◽  
Cement Paste ◽  
Molecular Weights ◽  
Oscillatory Rheology

Preparation of graft copolymers by the reaction of polymeric acyl chlorides with monohydroxy-terminated polymers: An introductory study

1988 ◽  
Vol 53 (8) ◽  
pp. 1735-1744 ◽  
Author(s):  
Jitka Horská ◽  
Jaroslav Stejskal ◽  
Pavel Kratochvíl ◽  
Aubrey D. Jenkins ◽  
Eugenia Tsartolia ◽  
...  
Keyword(s):  
Light Scattering ◽  
Chemical Composition ◽  
Statistical Model ◽  
Graft Copolymers ◽  
Coupling Reaction ◽  
Molecular Characteristics ◽  
Gel Formation ◽  
Acyl Chlorides ◽  
Molecular Weights

An attempt was made to prepare well-defined graft copolymers by the coupling reaction between acyl chloride groups located along the backbone chain and monohydroxy-terminated grafts prepared separately. The molecular weights and the parameters of heterogeneity in chemical composition of the products were determined by light scattering and osmometry. The determination of molecular characteristics revealed that the degree of grafting was low. The results therefore could not be confronted with a statistical model at this stage. The problems encountered in the synthesis, e.g., gel formation, and the data relating to the soluble products are discussed.

scholarly journals ffects of Poly{Carboxylate–g–(Ethylene Glycol)Methyl Ether} on the Physical Properties of Cement Paste

2016 ◽  
Vol 7 (1) ◽  
pp. 47 ◽  
Author(s):  
Heon-Young Cho ◽  
Jung-Mok Suh ◽  
Jin-Man Kim
Keyword(s):  
Ethylene Glycol ◽  
Cement Paste ◽  
Methyl Ether ◽  
Optimal Range ◽  
Molecular Weights ◽  
Testing Method ◽  
Super Plasticizer ◽  
Optimum Formulation ◽  
The Relationship ◽  
Glycol Methyl Ether

<p>The comb type poly{carboxylate–g–(ethylene glycol)methyl ether} (P(C–g–E)) copolymers were synthesized at different monomer ratios. The relationship between the synthetic conditions, the molecular weights<br />(Mp, Mn, Mw, Mz and Mw/Mn) and the dispersion ability of these copolymers in cement paste has been established. The molecular weights of P(C–g–E)s were analyzed by GPC. The dispersion abilities and the dispersion stabilities of P(C–g–E)s in cement paste were tested by mini slump testing method. The optimum formulation for P(C–g–E) synthesis was found to be P23MM 17 mol.%: SMS 10 mol.%: MA 8 mol.%: SMA 65 mol.%: APS 0.2 mol.%. The key components in P(C–g–E) synthetic formulation for cement super-plasticizer are SMA and P23MM. The SMA/P23MM in P(C–g–E) synthetic formulation is related to the dispersion ability and stability of P(C–g–E) in cement paste. The SMA/P23MM in P(C–g–E) synthetic formulation also influences the molecular weights and the polydispersity of P(C–g–E). The optimal range of SMA/P23MM in the formulation as a cement superplasticizer is 3.50~5.50. The dispersion ability of cement paste added with the optimum P(C–g–E) is increased more 3 times than those of the others.</p>

scholarly journals Cracking and Chemical Composition of Cement Paste Subjected to Heating and Water Re-Curing

2016 ◽  
Vol 14 (4) ◽  
pp. 134-143 ◽  
Author(s):  
Michael Henry ◽  
Katsufumi Hashimoto ◽  
Ivan Sandi Darma ◽  
Takafumi Sugiyama
Keyword(s):  
Chemical Composition ◽  
Cement Paste

Influence of the Chemical Composition of Bauxite on Mineral Formation and Properties of Sulfoaluminate-Ferrite Cement

2021 ◽  
Vol 325 ◽  
pp. 53-58
Author(s):  
Aleksandr A. Ponomarenko ◽  
Fedor L. Kapustin ◽  
Elena Makarova ◽  
Ekaterina S. Gerasimova
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Sulfur Dioxide ◽  
Specific Surface ◽  
Mineral Composition ◽  
Cement Paste ◽  
Setting Time ◽  
Physical And Mechanical Properties ◽  
Mineral Formation ◽  
Quality Coefficient

The influence of the chemical composition of bauxite on the mineral formation and structure of sulfoaluminate-ferrite clinker (SAFC), and physical and mechanical properties of cement based on it is studied. Ferrous bauxite, marble crushing screenings and neutralized fluorine-anhydrite were used for the synthesis of SAFC. The compositions of raw mixes of low-and high-alkaline SAFC are calculated with modular characteristics: Mf (ferritic modulus) = 0.35 and 0.7, Мs (sulfate modulus) = 0.167 and 0.5, respectively. Clinker synthesis from a raw mix containing ferrous bauxite with a quality coefficient of 1.7 must be carried out at a temperature of 1250 °C, which is reduced to 1200 °C for burning a raw mix based on bauxite with a quality coefficient of 2.2. Intensive decomposition of anhydrite occurs with the release of sulfur dioxide into the atmosphere at a temperature of 1300 °C, so it is not recommended to burn SAFC at this temperature. The mineral composition of the obtained SAFC is represented by sulfoaluminate, calcium sulfoferrite and free anhydrite. There is no C2S as a separate phase in clinkers, since in the process of their synthesis belite dissolves in 3С(A,F)·СŜ, mainly in the aluminoferrite phase. The use of bauxite with a quality coefficient of 2.2 in the SAFC raw mix increases the cement activity up to 54.2 MPa. Increasing its specific surface from 350 to 460 m2/kg significantly reduces the setting time of cement paste and increases the strength of sulfoaluminate-ferrite cement both in the early (up to 43.4 MPa) and late hardening periods (up to 67.3 MPa).

Effect of Uncontrolled Burning Rice Husk Ash in Foamed Concrete

2012 ◽  
Vol 626 ◽  
pp. 769-775 ◽  
Author(s):  
Josef Hadipramana ◽  
Abdul Aziz Abdul Samad ◽  
Ahmad Zaidi Ahmad Mujahid ◽  
Noridah Mohammad ◽  
Fetra Venny Riza
Keyword(s):  
Compressive Strength ◽  
Chemical Composition ◽  
Cement Paste ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
Amorphous Material ◽  
Fine Aggregate ◽  
Interfacial Zone ◽  
Wide Range ◽  
Foamed Concrete

Recently, foamed concrete has become a popular construction material that can be used in wide range of constructions application. Whilst the Rice Husk Ash (RHA) as agro-waste is contain high amount of silicon dioxide. RHA is produced in significant amount every year from agriculture countries. RHA has potential as a material to produce foamed concrete. In this research RHA has been used as a replacement for fine aggregate which used in construction as ordinary concrete material. In this study, foamed concrete with target density 1400, 1600 and 1800 kg/m3 has been produced. The compressive strength of foamed concrete with RHA has been tested. Concrete with Ratio 1:3 of RHA/Sand has higher compressive strength than ratios 3:1 and 2:2 of RHA/sand for every density. XRD and XRF test has been used to determinate chemical composition and crystalline structure of RHA. The result showed that RHA is an amorphous material which amorphous is important thing to pozzolanic process when hydration of cement paste. SEM and EDS test has been conducted to determine microstructure and chemical composition on microstructure of RHA foamed concrete. Amorphous RHA incorporating cement paste produces pozzolanic reaction. It is reduces the porosity and width of interfacial zone in such a way the density is increase.

scholarly journals Mitochondrial and cytoplasmic ribosomes from mammalian tissues. Further characterization of ribosomal subunits and validity of buoyant-density methods for determination of the chemical composition and partial specific volume of ribonucleoprotein particles

1977 ◽  
Vol 168 (2) ◽  
pp. 245-259 ◽  
Author(s):  
Ada Sacchi ◽  
Ugo Ferrini ◽  
Paola Londei ◽  
Piero Cammarano ◽  
Nadir Maraldi
Keyword(s):  
Chemical Composition ◽  
Specific Volume ◽  
Buoyant Density ◽  
Volume Ratio ◽  
Partial Specific Volume ◽  
Ribosomal Subunits ◽  
Molecular Weights ◽  
Mitochondrial Ribosomes ◽  
Density Methods ◽  
Cytoplasmic Ribosomes

1. At 0–4°C mitochondrial ribosomes (55S) dissociate into 39S and 29S subunits after exposure to 300mm-K+ in the presence of 3.0mm-Mg2+. When these subunits are placed in a medium containing a lower concentration of K+ ions (25mm), approx. 75% of the subparticles recombine giving 55S monomers. 2. After negative staining the large subunits (20.3nm width) usually show a roundish profile, whereas the small subunits (12nm width) show an elongated, often bipartite, profile. The dimensions of the 55S ribosomes are 25.5nm×20.0nm×21.0nm, indicating a volume ratio of mitochondrial to cytosol ribosomes of 1:1.5. 3. The 39S and 29S subunits obtained in high-salt media at 0–4°C have a buoyant density of 1.45g/cm3; from the rRNA content calculated from buoyant density and from the rRNA molecular weights it is confirmed that the two subparticles have weights of 2.0×106 daltons and 1.20×106 daltons; the weights of the two subunits of cytosol ribosomes are 2.67×106 and 1.30×106 daltons. 4. The validity of the isodensity-equilibrium-centrifugation methods used to calculate the chemical composition of ribosomes was reinvestigated; it is confirmed that (a) reaction of ribosomal subunits with 6.0% (v/v) formaldehyde at 0°C is sufficient to fix the particles, so that they remain essentially stable after exposure to dodecyl sulphate or centrifugation in CsCl, and (b) the partial specific volume of ribosomal subunits is a simple additive function of the partial specific volumes of RNA and protein. The RNA content is linearly related to buoyant density by the equation RNA (% by wt.)=349.5−(471.2×1/ρCsCl), where 1/ρCsCl=[unk]RNP (partial specific volume of ribonucleoprotein). 5. The nucleotide compositions of the two subunit rRNA species of mitochondrial ribosomes from rodents (42% and 43% G+C) are distinctly different from those of cytoplasmic ribosomes.

scholarly journals Nanofibers for drug delivery – incorporation and release of model molecules, influence of molecular weight and polymer structure

2015 ◽  
Vol 6 ◽  
pp. 1939-1945 ◽  
Author(s):  
Jakub Hrib ◽  
Jakub Sirc ◽  
Radka Hobzova ◽  
Zuzana Hampejsova ◽  
Zuzana Bosakova ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Polyvinyl Alcohol ◽  
Polymer Structure ◽  
Release Profile ◽  
Polyethylene Glycols ◽  
Aqueous Environment ◽  
Molecular Weights ◽  
Molecular Length ◽  
Pharmacologically Active ◽  
Pharmacologically Active Compounds

Nanofibers were prepared from polycaprolactone, polylactide and polyvinyl alcohol using NanospiderTM technology. Polyethylene glycols with molecular weights of 2 000, 6 000, 10 000 and 20 000 g/mol, which can be used to moderate the release profile of incorporated pharmacologically active compounds, served as model molecules. They were terminated by aromatic isocyanate and incorporated into the nanofibers. The release of these molecules into an aqueous environment was investigated. The influences of the molecular length and chemical composition of the nanofibers on the release rate and the amount of released polyethylene glycols were evaluated. Longer molecules released faster, as evidenced by a significantly higher amount of released molecules after 72 hours. However, the influence of the chemical composition of nanofibers was even more distinct – the highest amount of polyethylene glycol molecules released from polyvinyl alcohol nanofibers, the lowest amount from polylactide nanofibers.

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