Effect of Cement Paste Preparation Procedure and Cement Stone Age on its Phase Composition

2021 ◽  
Vol 887 ◽  
pp. 473-479
Author(s):  
I.N. Maksimova ◽  
N.I. Makridin ◽  
Anna V. Dergunova ◽  
Yu.V. Babenkova
Keyword(s):  
Phase Composition ◽  
Cement Paste ◽  
Cement Stone ◽  
Building Structures ◽  
Analysis Method ◽  
Optimal Sequence ◽  
Concrete Mixtures ◽  
Concrete Building ◽  
The Given ◽  
Mixing Water

Self-levelling and self-consolidating concrete mixtures formed with the use of superplasticizers are worthwhile for the manufacture of reinforced concrete structures. It is important to evenly distribute not only the mixing water in the system, but also the dissociated plasticizer ions for cement dispersed compositions with plasticizing additives. It is established that the optimal sequence of loading and mixing of the components of a cement composition is not only a promising direction for intensifying the manufacture of concrete building structures, but also a tool for improving the mechanical properties of cement brick and concrete made on its basis, as well as for increasing its durability and reliability. When superplasticizers are introduced into the pre-ground cement paste, the rheological properties of the compositions are improved, as well as the structure of the hardened composites. The given article is devoted to the study of the effect of the procedural factor and the duration of mixing of highly concentrated cement compositions with the addition of a superplasticizer based on naphthalene sulfonic acid (SP C-3) on the phase composition of hardened composites during various periods of hydration. Experimental results were obtained using the X-ray phase analysis method. Tested are 15 series of samples of cement stone with W/C ratio range between 0,18 and 0,27 and SP C-3 between 0 and 1.0 % by cement weight. Comparing the phase composition of cement stone after 28 days of hardening with that of 4,5 years, it was found that at first the C3SH2 phase, particularly enriched with calcium oxide, is formed, which decays over time and disappears in the 4,5-year hardening amples.

scholarly journals THE SELF COMPACTING CONCRETE (SCC) USING SEAWATER AS MIXING WATER WITHOUT CURING

2018 ◽  
Author(s):  
Erniati Bachtiar
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Sea Water ◽  
Splitting Tensile Strength ◽  
Test Method ◽  
Building Structures ◽  
Working Process ◽  
Self Compacting Concrete ◽  
Concrete Building ◽  
Mixing Water

The number of problems found in the construction world includes the difficulty or lack of fresh water in some areas to be mixed in the concrete, negligence in the maintenance of concrete and working process of concrete mainly on the concrete structures have a complex reinforcement and high concrete building structures. This study aims to find out the compressive strength, splitting tensile strength, absorption, and porosity of Self Compacting Concrete (SCC) using sea water as mixing water and with or without curing in sea water. The test specimens were made for each test specimen withthe variation on age 1 day, 3 days, 7 days, 28 days and 90 days. The test method of compressive strength according to ASTM 39/C 39M-12a standard, tensile strength according to ASTM C496 / C496M-11 standard and the porosity and absorption according to ASTM C642-13 standard. The result of research was 1) the decrease in compressive strength in the specimen SCC-SWC was from 3 days, 7 days, 28 days and 90 days consecutive 13.20%, 12.90%, 12.80%, and 12.50%; 2) the decreases in splitting tensile strength in the specimen SCC-SWC were from the age of 3 days, 7 days, 28 days until the age of 90 days consecutive by 3.10%, 8.05%, 9.51%, and 9.21%; 3) the increase in the porosity values on the specimenSCC seawater without cured in sea water (SCC-SWC) at age 3 days, 7 days, 28 days and 90 days was 2.86%, 7.90%,5.86%, and 5.55%, respectively; 4) the increase in the absorption values on the specimen SCC without curing at 3 days, 7 days, 28 days and 90 days was 15.80%, 20.57%, 15.84%, and 30.80%, respectively. The increase in mechanical properties (compressive strength and tensile strength) in the both of the specimen SCC-SC and SCC-SWC along with the decrease of porosity and absorption. Conversely, the decrease of compressive strength and tensile strength in the both of the specimen SCC-SC and SCC-SWC along with the increase in porosity and absorption value in the SCC

Fine-Grained Concrete for Repair and Restoration of Building Structures

2021 ◽  
Vol 1038 ◽  
pp. 317-322
Author(s):  
Alexandra Shyshkina ◽  
Alexander Shyshkin
Keyword(s):  
Rheological Properties ◽  
Operational Reliability ◽  
Optimal Combination ◽  
Cement Stone ◽  
Building Structures ◽  
Active Components ◽  
Fine Grained ◽  
Concrete Mixtures ◽  
Concrete Properties ◽  
Mineral Fillers

It is determined that the active components of modern concrete are active mineral fillers, such as microsilica, meta-kaolin, ash-bearing or compositions from them, as well as superplasticizers. The optimal combination of these additive modifiers allows you to control the rheological properties of concrete mixtures and to modify the structure of the cement stone in such a way as to provide concrete properties that provide high operational reliability of structures. However, they have certain disadvantages that hamper their widespread use. The purpose of the research is to determine the effect of reaction powders applied simultaneously with colloidal surfactant, on the strength of powdered concrete and the rate of its formation.

scholarly journals Assess the Effectiveness of protective Concrete coatings of microbiological sulfuric acid Aggression

2019 ◽  
Vol 97 ◽  
pp. 02022
Author(s):  
Viktor Sopov ◽  
Julia Danchenko ◽  
Ekaterina Latorez
Keyword(s):  
Sulfuric Acid ◽  
Building Structures ◽  
Predominant Role ◽  
Microbiological Processes ◽  
Repair Materials ◽  
Bactericidal Properties ◽  
Mineral Acids ◽  
Concrete Building ◽  
Modified Epoxy

Specification of corrosion processes in sewerage networks, the predominant role of microbiological processes in them requires the protection of concrete with materials resistant to specific biogenic sulfuric acid aggression. The effective protective materials, in this case, are those that, in addition to acid-proofing materials, have bactericidal properties. Polymer composite materials (PCM) of cold curing based on modified epoxy-resin, resins with dispersed oxides as fillers are widely used in construction. Unique properties and simple technologies make it possible to use them as injection formulations for repair, restoration and restoration of building structures and structures, waterproofing and facing materials, for impregnating, gluing and coating metal, wooden, brick and concrete building structures and parts. In the reconstruction and restoration of sewerage collectors operating under conditions of exposure to liquid biochemically aggressive media with mineral acids and organic substances, particular attention is paid to the permeability of repair materials. Based on the results of the study, PCM compositions were chosen whose estimated lifetime is about 20 years, ensuring reliable protection of the sewage collectors from corrosion.

scholarly journals POROSITY PARAMETERS OF CEMENT STONE CONTAINING CHEMICAL ADMIXTURES OF DIFFERENT PURPOSE / CEMENTINIO AKMENS SU SKIRTINGOS PASKIRTIES CHEMINIAIS PRIEDAIS PORINGUMO RODIKLIAI

2013 ◽  
Vol 5 (5) ◽  
pp. 530-535
Author(s):  
Lukas Venčkauskas ◽  
Mindaugas Daukšys
Keyword(s):  
Cement Paste ◽  
Cement Stone ◽  
Hardened Cement ◽  
Closed Porosity ◽  
Hardened Cement Paste ◽  
Chemical Admixtures ◽  
Average Size ◽  
The Impact ◽  
Plasticizing Admixture

The conducted research has established a complex influenceand the impact of separate chemical admixtures of differentpurpose on the parameters of the porosity of hardened cementpaste such as open and closed porosity, the average size of poresand the rates of pore inequality. According to the parametersof the porosity of hardened cement paste, on the basis of A. E.Sheikin’s methodology, the number of freezing-thawing cycleswas predicted. This research used plasticizing, viscosity modifyingand antifoaming admixtures. It has been found that, when theamount of plasticizing admixture in cement paste (W/C–0.45) isconstant and makes 1.1% of the cement mass, and the amountof viscosity modifying and antifoaming the admixture increasesfrom 0.1 to 0.6% and from 0.05 to 0.3% respectively, the openporosity of hardened cement paste varies between 30.21% and31.06%, while closed porosity varies between 5.39% and 6.22%.When the amount of the plasticizing admixture in cement paste(W/C–0.45) exceeds 1.1% of the cement mass, the open porosityof hardened cement paste increases by 1.4 times and closedporosity decreases by 2.5 times. While adding 0.1% of the viscositymodifying admixture to cement paste, the open porosityof hardened cement paste is increased by 1.5 times and closedporosity decreases by 2.4 times. The amount of 0.05% of thecement mass of the antifoaming admixture results in the increasedopen porosity of hardened cement paste by 1.5 times and reducedclosed porosity by 3.5 times. Santrauka Tyrimo metu nustatyta kompleksinė bei atskirų skirtingos paskirties cheminių priedų įtaka cementinio akmens poringumo rodikliams – atvirajam ir uždarajam poringumui, vidutinio porų dydžio ir porų vienodumo rodikliams. Tyrimuose naudoti cheminiai priedai: plastifikuojantis, klampą modifikuojantis ir mišinyje susiformavusias oro poras suardantis priedas. Nustatyta, kad cemento tešloje (V/C – 0,45) esant pastoviam plastifikuojančio priedo kiekiui – 1,0 % cemento masės, klampą modifikuojančio priedo kiekiui kintant nuo 0,1 iki 0,6 %, o mišinyje susiformavusias oro poras suardančio priedo kiekiui kintant nuo 0,05 iki 0,3 %, cementinio akmens atvirasis poringumas svyruoja nuo 30,21 iki 31,06 %, o uždarasis – nuo 5,39 iki 6,22 %. Cemento tešloje viršijus plastifikuojančio priedo 1,1 % cemento masės, cementinio akmens atvirasis poringumas padidėja apie 1,4 karto, o uždarasis poringumas sumažėja apie 2,5 karto. Pridėjus į tešlą 0,1 % cemento masės klampą modifikuojančio priedo, cementinio akmens atvirasis poringumas padidėja apie 1,5 karto, uždarasis poringumas sumažėja apie 2,4 karto. Oro poras suardančio priedo kiekis 0,05 % cemento masės cementinio akmens atvirąjį poringumą padidina apie 1,5 karto, uždarąjį poringumą sumažina apie 3,5 karto.

scholarly journals Alkali activated cements mix design for concretes application in high corrosive conditions

2018 ◽  
Vol 230 ◽  
pp. 03007 ◽  
Author(s):  
Oleksandr Kovalchuk ◽  
Valentina Grabovchak ◽  
Yaroslav Govdun
Keyword(s):  
Corrosion Resistance ◽  
Phase Composition ◽  
Mix Design ◽  
Cement Stone ◽  
Hydration Products ◽  
Alkali Content ◽  
High Corrosion Resistance ◽  
Corrosion Resistant ◽  
High Corrosion ◽  
Alkali Activated

This paper covers the results of development of corrosion resistant ash alkali-activated cements based on regulation of phase composition of the hydration products through changing the alkali content, content of calciumcontaining cement constituents resulting in the increase strength and density of the cement stone. The results of study suggested to conclude that the cement compositions with predominance in the hydration products of weakly soluble low basic hydrosilicates of calcium, hydrogarnets and minerals similar to natural hydroaluminates exhibited the highest corrosion resistance. The results of comparison suggested to draw a conclusion that the alkali-activated cements Types APC III-400 and ACC V-400, according to National Ukrainian Standard DSTU B V.2.7, had high corrosion resistance compared to that of OPC, thus allowing to recommend the developed cements for the concretes intended for use in aggressive environments, inclusive of sodium and magnesium sulphates and others. Coefficients of corrosion resistance of concretes are higher than 1 after even 42 months.

scholarly journals THE ESTIMATION METHODS OF MICROFILLERS INFLUENCE ON CEMENT STONE PROPERTIES/MIKROUŽPILDŲ ĮTAKOS CEMENTINIO AKMENS SAVYBĖMS ANALITINIO ĮVERTINIMO PRINCIPAI

1997 ◽  
Vol 3 (10) ◽  
pp. 69-75
Author(s):  
Juozas Deltuva ◽  
Žymantas Rudžionis
Keyword(s):  
Relative Density ◽  
Silica Fume ◽  
Cement Paste ◽  
Heterogeneous Material ◽  
Estimation Methods ◽  
Cement Stone ◽  
Structural Element ◽  
Regular Form ◽  
Amorphous Sio2 ◽  
Hardening Process

The concrete and cement microfillers are materials of different fineness, such as wastes of production or pulverized rocks. According to their influence on cement hardening process, they may be classified into inert microfillers or chemically active ones. The chemically active microfillers, such as silica fume, fly ashes and others, have more then 50% amorphous SiO2, that takes part in cement hardening process. Inert microfillers, such as granite, dolomite, sand dust and others, in most cases have no influence on the cement hydration. The usage of microfillers in concrete is common, but so far no clear dependence between the quantity of added microfillers and properties of concrete has been established. One of possible ways to estimate the microfillers influence on the products with cement binder is the structural element method. The structural element is the smallest cell, approximated to a spatial figure of regular form, that has all components with the same proportions, as in all the volume of heterogeneous material. The essence of this method is to divide the mix in to bigger particles, that are named “nuclei” of structural elements and take 50% of all mix volume, and smaller particles, that form cover layers of the nuclei and make up the rest of the volume of the mix. The dependence between the relative density of loose materials and relation (1) between the diameters of the bigger and smaller particles of the structural element has been estimated. This relation is changed when microfillers are added to the cement. There is a possibility to optimize relative density by (2), (3) and (4) relations, if the granulometric composition of the cement and microfillier is known. The experimental and calculated results of this optimization are shown in Table 1. The properties of pressed cement stone with inert microfillers admixture are presented in Table 2. Formulae for calculating the relative density (8) and compressive strength (11) of hardening cement have been estimated. The chemically active microfillers, such as silica fume, interact with Ca(OH)2 and form new CSH. The density and strength of cement stone increased after this interaction. The influence of chemically active microfillers on the relative density of the cement stone is given in (12). The density of cement stone increases to 4.5% and strength increases to 40.2%, if the quantity of inert microfillers in the cement paste reaches 10%. The density of cement stone increases to 7.4% and strength increases to 54.7%, if the quantity of chemically active microfillers in the cement paste reaches 10%.

scholarly journals Polymerization of Isobutylene in a Rotating Packed Bed Reactor: Experimental and Modeling Studies

2021 ◽  
Vol 11 (21) ◽  
pp. 10194
Author(s):  
Wenhui Hou ◽  
Wei Wang ◽  
Yang Xiang ◽  
Yingjiao Li ◽  
Guangwen Chu ◽  
...  
Keyword(s):  
Strong Dependence ◽  
Average Molecular Weight ◽  
Packed Bed ◽  
Packed Bed Reactor ◽  
Mixing Efficiency ◽  
Polymerization Temperature ◽  
Analysis Method ◽  
Rotating Speed ◽  
Rotating Packed Bed ◽  
The Given

Polymerization of isobutylene (IB) for synthesizing highly reactive polyisobutylene (HRPIB) is characterized by a complicated fast intrinsic reaction rate; therefore, the features of its products exhibit a strong dependence on mixing efficiency. To provide uniform and efficient mixing, a rotating packed bed was employed as a reactor for polymerization of IB. The effects of operating parameters including polymerization temperature (T), rotating speed (N) and relative dosage of monomers and initiating systems ([M]0/[I]0) on number-average molecular weight (Mn) of HRPIB were studied. HRPIB with Mn of 2550 g·mol−1 and exo-olefin terminal content of 85 mol% were efficiently obtained at suitable conditions as T of 283 K, N of 1600 rpm and [M]0/[I]0 of 49. Moreover, the Mn can be regulated by changing T, N and [M]0/[I]0. Based on the presumptive-steady-state analysis method and the coalescence–redispersion model, a model for prediction of the Mn was developed and validated, and the calculated Mn values agreed well with experimental results, with a deviation of ±10%. The results demonstrate that RPB is a promising reactor for synthesizing HRPIB, and the given model for Mn can be applied for the design of RPB and process optimization.

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