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

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

Mokslas - Lietuvos ateitis ◽

10.3846/mla.2013.83 ◽

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.

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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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