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

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.

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Determining the Contact Angle of Hardened Cement Paste Using Thin Layer Wicking Method

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.539.184 ◽

2013 ◽

Vol 539 ◽

pp. 184-188 ◽

Cited By ~ 1

Author(s):

Qian Tian ◽

Hang Zhang ◽

Yu Jiang Wang ◽

Fei Guo ◽

Ting Yao ◽

...

Keyword(s):

Contact Angle ◽

Thin Layer ◽

Cement Paste ◽

Hardened Cement ◽

Powder Size ◽

Hardened Cement Paste ◽

Time Curve ◽

Function Mechanism ◽

Chemical Admixtures ◽

Capillary Stress

Contact angle is a very important parameter to investigate the function mechanism of chemical admixtures as well as the capillary stress resulted from self-desiccation or drying. However, in most of the studies, it is only assumed to be 0 degrees. This paper studied the contact angle of hardened cement paste using thin wicking method. A serious of study was conducted on the influence of layer preparation, pre-contacting method, cement paste powder size, and suspension concentration on the measuring results. An optimized thin layer wicking method was proposed for determining the contact angle of hardened cement paste, which improves effectively the linear correlation of the penetration distance - time curve and satisfies the prerequisite of Washburn function.

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The effects of modifying additives and chemical admixtures on the properties of porous fresh and hardened cement paste

Construction and Building Materials ◽

10.1016/j.conbuildmat.2016.10.014 ◽

2016 ◽

Vol 127 ◽

pp. 679-691 ◽

Cited By ~ 5

Author(s):

Jurga Šeputytė-Jucikė ◽

Modestas Kligys ◽

Marijonas Sinica

Keyword(s):

Cement Paste ◽

Hardened Cement ◽

Hardened Cement Paste ◽

Modifying Additives ◽

Chemical Admixtures

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The impact of primary sludge from paper industry on the properties of hardened cement paste and mortar

Construction and Building Materials ◽

10.1016/j.conbuildmat.2018.04.011 ◽

2018 ◽

Vol 172 ◽

pp. 553-561 ◽

Cited By ~ 11

Author(s):

Jurgita Malaiskiene ◽

Olga Kizinievic ◽

Viktor Kizinievic ◽

Renata Boris

Keyword(s):

Cement Paste ◽

Paper Industry ◽

Hardened Cement ◽

Hardened Cement Paste ◽

Primary Sludge ◽

The Impact

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Microscopic Change in Hardened Cement Paste Due to High-Speed Impact

10.20944/preprints201812.0074.v1 ◽

2018 ◽

Author(s):

Yuya Sakai ◽

Ivwananji Sikombe ◽

Keiko Watanabe ◽

Hiroyuki Inoue

Keyword(s):

Cement Paste ◽

High Speed ◽

Impact Load ◽

Hardened Cement ◽

Hardened Cement Paste ◽

High Speed Impact ◽

Gas Gun ◽

Microscopic Change ◽

The Moment ◽

The Impact

Impact load was applied to hardened cement paste (HCP) specimens using a gas gun to investigate microscopic changes in the specimens and develop a better response model of concrete subjected to impact load. Plasma emission was observed at the moment of impact at 420 m/s and the colour of the portion near the impact point turned brighter. This brighter portion was analysed, and it was observed that the pore structure was coarser compared to the other portion; however, the results of thermogravimetry and X-ray diffraction analysis were similar. A possible reason is that the generated heat was instantaneous and the rate of the temperature increase in the HCP decreased due to evaporation of water in the HCP. These results indicate that during impact at a few hundred m/s, porosity increase due to heat effect is more dominant than porosity decrease due to mechanical compaction.

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PROPERTIES OF HARDENED CEMENT PASTE DEPENDING ON SILANE BASED CHEMICAL ADMIXTURES / CHEMINIŲ PRIEDŲ SILANŲ PAGRINDU ĮTAKA CEMENTINIO AKMENS SAVYBĖMS

Engineering Structures and Technologies ◽

10.3846/2029882x.2012.677409 ◽

2012 ◽

Vol 4 (1) ◽

pp. 29-36 ◽

Cited By ~ 1

Author(s):

Ieva Ragaišytė ◽

Mindaugas Daukšys ◽

Albertas Klovas

Keyword(s):

Cement Paste ◽

Bending Strength ◽

Flow Characteristics ◽

Water Repellent ◽

Hardened Cement ◽

Control Specimen ◽

Cement Slurry ◽

Hardened Cement Paste ◽

Chemical Admixtures ◽

Chemical Admixture

The article focuses on the influence of water repellent, silane based concrete admixtures on the physical, mechanical and porosity properties of hardened cement paste. To obtain the expected results, six compositions of cement slurries were designed changing the amount and type of the silane based chemical admixture. In order to obtain technological, physical and mechanical properties of cement (slurry) stone, the following experiments, including a test on the flow characteristics of cement slurries, a test on compression and bending strength as well as the analysis of porosity and resistance to frost were accomplished. On the basis of the achieved results and using a different amount and type of silane based chemical admixtures, the flow characteristics of cement slurry has increased up to 1,47 times in respect to the control specimen. On the other hand, when using the above introduced silane based chemical admixtures, the obtained results show a decrease in the density and strength of compression and bending. By adding chemical admixture “WACKER BS 1701” 0,2% and taking into account the amount of cement, a decrease in density goes up to 2,4%. The most noticeable decrease in bending strength (26%) is obtained by using WACKER BS SMK 2101 (0,1% in respect to the amount of cement). In addition, the biggest decrease in compression strength (34,6%), considering the control specimen, can be noticed when using SILRES BS 290 (0,2%) as a silane based chemical admixture. Water absorption of the control specimen with no silane based chemical admixtures is very similar to those containing them (vary around 1). The properties of porosity (opened and closed) are also very close and vary around 2% at the maximum. The indicator of medium pore size-λ shows that the control specimen include large pores (λ = 7,92). In most cases, by using the silane based chemical admixture, minor pores are obtained (λ = 0,94 – 3,66). The results received following 100 cycles of freezing-thaw show that all specimens have passed the test. Their surfaces did not contain any cracking. Santrauka Straipsnyje nagrinėjama cheminių priedų silanų/siloksanų pagrindu įtaka cementinio akmens fizikinėms ir mechaninėms savybėms bei poringumui. Tyrimams buvo paruoštos šešios cemento tešlos, naudojant skirtingos koncentracijos silanų/siloksanų pagrindu pagamintus cheminius priedus. Tyrimo metu nustatytas cemento tešlos sklidumas, cementinio akmens tankis, lenkimo ir gniuždymo stipriai, poringumo parametrai bei atsparumas šalčiui. Nustatyta, kad naudojant skirtingos koncentracijos silanų/siloksanų pagrindu pagamintus cheminius priedus, cemento tešlos sklidumas padidėjo iki 46,3%, lyginant su kontroline tešla. Cementinio akmens tankis sumažėjo iki 2,4%, lenkimo stipris – iki 21,0%, gniuždymo stipris – iki 34,6%, lyginant su kontroliniu bandiniu be silanų/siloksanų pagrindu pagamintų priedų. Cementinio akmens be cheminių priedų silanų/siloksanų pagrindu vandens įgėris (12,16%), atviras ir uždaras poringumai yra panašūs kaip ir cementinio akmens su cheminiais priedais silanų/siloksanų pagrindu. Cementinio akmens bandiniai išlaikė 100 užšaldymo ir atšildymo ciklų atsparumo šalčiui bandymą.

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INFLUENCE OF MICROSTRUCTURE OF HYDRATE PHASES OF CEMENT STONE ON CONCRETE DURABILITY

Bulletin of Belgorod State Technological University named after V G Shukhov ◽

10.34031/2071-7318-2021-6-3-8-18 ◽

2021 ◽

Vol 6 (3) ◽

pp. 8-18

Author(s):

B. Trofimov ◽

K. Shuldyakov ◽

A. Mahmudov

Keyword(s):

Reinforced Concrete ◽

Cement Paste ◽

Frost Resistance ◽

Concrete Structures ◽

Air Entrainment ◽

Cement Stone ◽

Hardened Cement ◽

Reinforced Concrete Structures ◽

Hardened Cement Paste ◽

Structural Element

One of the main problems in modern concrete science is the low durability of reinforced concrete structures and constructions, especially those located in harsh climatic conditions and saturated with marine or mineralized water. Existing standards guide designers and builders to increase the density of concrete with increasing degree of aggressive impact, as well as through cyclical freezing of concrete structures, which taken as the main indicator of durability, air entrainment is mandatory. The problem is not only the provision of high frost resistance of concrete, but also finding a method of controlling it, which, as a rule, takes quite a long time. The destruction of concrete during cyclical freezing occurs not only due to the formation of ice in the pores of concrete, but also as a result of temperature stresses in concrete with ice, as well as the washing out of portlandite and aging of the cement gel – the main structural element of hardened cement paste. This means that the durability of the concrete can be ensured by maintaining the finely dispersed structure of the hardened cement paste, preventing crystallization of the gel from external influences or increasing its basicity. It is shown that only water reduction and pozzolanization, which provides residual portlandite content in Portland cement concrete stone 2–5 % by weight ensure the achievement of increased durability of concrete, reinforced concrete structures and constructions. A method is proposed to assess the stability of hydrate phases as well as the relationship between the durability and frost resistance of concrete.

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