Hydrophilicity as a measure of the efficiency of the superplasticisers

W pracy przedstawiono wyniki badań budowy strukturalnej superplastyfikatorów nowej generacji stosowanych w technologii betonu. Badania struktury superplastyfikatorów przeprowadzono na próbkach przy wykorzystaniu chromatografii żelowej (GPC) oraz fourierowskiej spektroskopii absorpcyjnej w podczerwieni (FTIR). Przedstawiono wyniki badań wpływu tych superplastyfikatorów na właściwości reologiczne zaczynów cementowych. Wykazano, że skuteczność działania superplastyfikatora (zmniejszenie lepkości plastycznej) wzrasta z: zawartością polimeru superplastyfikatora w całkowitej masie posyntezowej próbki produktu technicznego, masą molową wagowo- średnią (Mw) polimeru superplastyfikatora, obecnością wolnych grup karboksylowych lub bezwodnikowych w polimerze oraz hydrofilowością polimeru superplastyfikatora: określoną stosunkiem absorbancji hydrofilowych grup eterowych do hydrofobowych grup estrowych w łańcuchu polimerowym. Powyższe stwierdzono dla superplastyfikatorów pochodnych kawasów: akrylowego (SP-A1 i SP-A2) i maleinowego (SP-M2 i SP-M1). Skuteczność działania superplastyfikatorów maleje wraz ze wzrostem zawartości wolnych, nieprzereagowanych z kwasami lub bezwodnikiem poli(glikoli etylenowych) PEG. Wykazano, że superplastyfikatory pochodne bezwodnika maleinowego (SP-M1 i SP-M2) o większej hydrofilowości (wykazanej badaniami strukturalnymi) charakteryzują się większą skutecznością działania niż superplastyfikatory pochodne kwasu akrylowego (SP-A1 i SP-A2).This paper presents the results of chemical structural investigations of four new-generation superplasticizers (denoted here as SP-A through SP-M2) used in concrete production engineering. The commercial product samples, the gel permeation chromatography (GPC) and the Fourier-Transformed Infrared Spectroscopy (FTIR) test methods were applied to the research. The effect of superplasticizers on the rheological properties of cement pastes was tested. The performance of a superplasticizer, i.e. the reduction of plastic viscosity, was demonstrated to be enhanced by: hydrophilicity of the SP polymer –understood as the ratio of hydrophilic ethers to hydrophobic esters in the polymer chain, SP polymer content in the bulk of the commercial product sample, weight-average molecular weight (Mw) of the SP polymer. The above relations were confirmed for the studied superplasticizers– the derivatives of: acrylic acid (SP-A1 and SP-A2) and maleic acid (SP-M2 and SP-M1). The efficiency of superplasticizers was found to decrease with the contents of the free poly(ethylene glycols) (PEGs) which remained unreacted with acids and/or anhydride. The superplasticizers based on the maleic anhydride derivatives (SP-C and SP-D) proved to be more efficient and to slow down the hydration process to a much higher extent than the superplasticizers – acrylic acid derivatives (SP-A1 and SP-A2)

Impact of chemical admixtures with different efect on properties of cement pastes and mortars

The presented research is aimed at demonstrating differences in the effectiveness of action between chemical admixtures available on the domestic market with a similar and different course of action in cement pastes and mortars. Admixtures with aeration, aeration and plasticizing, sealing, acceleration of setting time, and liquefaction effect came from different manufacturers and were used in the amount recommended by them. It has been shown that, in the case of chemical admixtures with different direction of effect, their effectiveness in cement mortars is conditioned by the mechanism of their action. However, for the admixtures with the same direction of action, but coming from different manufacturers, the decisive influence on their effectiveness in mortars is their dosage amount and the type and concentration of organic compounds used to produce these admixtures. The greatest improvement in the properties of mortar, demonstrated by their increased compressive strength, slight linear changes and lower absorbability, was obtained in the presence of liquidizing admixtures and slightly inferior in the presence of ones that accelerate setting time, plasticize, seal or aerate. On the other hand, the least beneficial effect on improving the functional properties of mortars was observed in the presence of aeration and plasticizing admixtures

The Influence of limestone microfiler in cement on the heat of hardening

W pracy przedstawiono wyniki badań wpływu mikrowypełniaczy wapiennych stosowanych w przemyśle cementowym jako dodatek mineralny do cementu na kinetykę oraz całkowitą ilość ciepła hydratacji cementu w obecności superplastyfikatora na bazie eteru polikarboksylowego (BP). Wykazano, że dodatek do cementu mączki wapiennej przyspiesza pojawienie się efektu krzemianowego, na krzywych szybkości wydzielania ciepła, a intensywność tego efektu wzrasta ze wzrostem stopnia rozdrobnienia mikrowypełniacza. Obecność superplastyfikatora (BP) w zaczynach cementowych z mikrowypełniaczem wapiennym powoduje opóźnienie pojawienia się efektu krzemianowego na krzywej szybkości wydzielania ciepła. Intensywność efektu krzemianowego podobnie jak w przypadku zaczynu bez dodatku superplastyfikatora jest tym większa im większy jest stopień rozdrobnienia mikrowypełniacza.The results of investigations of the limestone microfillers influence on the heat evolution rate and total heat of cement hydration in the presence of the superplasticizer (BP) are presented. It is shown that the addition of limestone microfillers to cement intensifies appearance of a silicate effect on the curve of heat evolution rate and intensity of t his effect increases with the growth of fin e fraction level in a microfiller. The presence of the superplasticizer in cement pastes with limestone microfiller delays appearance ofsilicate effect on the curve ofheat evolution rate. Similarly to cement pastes without a superplasticizer the intensity of t his effect increases with the growth of fin e fraction level in the microfiller

The resistance of mortars with fluidized beds boiler fly ashes and conventional fly ashes to acid corrosion

This paper presents the results of research undertaken to determine the impact of the aggressive environment of acid corrosion on the durability of cement mortars with the participation of fluidized beds boiler fly ashes and conventional fly ashes used separately and in the form of mixtures. The beneficial effect of fluidized beds boiler fly ashes on the physical properties of cement mortars has been shown, i.e. reduction of the contraction, decrease of weight loss and reduction of the destruction of mortars in acid corrosion. This effect was especially beneficial for mortars containing higher (45% by weight) content of fluidized fly ashes, used separately and in the form of mixtures, regardless of the aggressiveness of the environment (1%, 3% and 5% HCl solution)

Influence of the structural modification of polycarboxylate copolymer with a low dispersing ability on the set-retarding of Portland cement

Two structurally modified polycarboxylate (PC) copolymers were synthesized to explore the influence of structural modification with these polymers on the set-retarding of Portland cement. The dispersion ability of these polymers was eliminated by introducing very short graft side chains. The synthesized copolymer structures were verified by FTIR, GPC and 1H NMR analyses. The initial and final setting times, polymer adsorption capability, strength development, paste fluidity, and XRD of hardened pastes were tested. The test results indicate that the PC copolymers do not increase the cement paste fluidity due to their short graft side chain length, while a significant set-retarding effect is observed when the polymer structure is highly anionic, with the set-retarding effect increasing linearly with polymer dosage up to 1%. The adsorption of copolymer on cement grains rapidly reaches saturation within 5 minutes after mixing for both polymers. Adding these PC copolymers does not noticeably change the early strength development, although the polymers selectively affect the hydration behavior of C3S and C2S at very early ages. Early hydration of groups, such as C3S, C2S, C3A and C4AF, is not likely to be significantly involved in the mechanism by which carboxylate copolymers with very short graft chains delay cement setting.close0