Additional Porosity as a Side Effect of Polycarboxylate Addition and Its Influence on Concrete’s Scaling Resistance

Abstract

A side effect of using modified polycarboxylates to liquefy a concrete mix is additional pores in the concrete. They change the air void system in hardened concretes, and can be used to evaluate the freeze–thaw resistance of concretes. The purpose of this study is to determine the impact of the abovementioned quantitative and qualitative parameters on the freeze–thaw resistance of concretes. The research program was performed on eight sets of air-entraining and non-air-entraining concretes with a variable content of superplasticizer based on modified polycarboxylates. The basic composition of and air-entraining admixture content in the air-entraining concrete mixtures were held constant. Pore structure tests were performed according to EN 480-11. Scaling resistance was determined according to PKN-CEN/TS 12390-9. The results showed that as the content of modified polycarboxylates increased, the pore structure was adversely affected, and, consequently, the air void parameters deteriorated. At the same time, the freeze–thaw resistance of the non-air-entraining concretes decreased. The pores sizes also changed. As the fluidity increased, the specific surface area decreased, and, consequently, the spacing factor increased. The air-entraining concretes, despite the deterioration in the pore structure due to the modified polycarboxylates, were found to be very good quality concretes after 56 freeze–thaw cycles in the presence of 3% NaCl.

Both Plasticizing and Air-Entraining Effect on Cement-Based Material Porosity and Durability

“…After 14 cycles, the shape was complete due to the periodic freezing and thawing process, and the mortar around the sample did not fall off seriously. Obtained test results indicated by Nowak-Michta et.al [42] show good scaling resistance results after freeze-thaw cycles.…”

Retardation Effects of Filter Mud in Molasses on Composite Silicate Cement

“…When ordinary Portland cement hydrates in sugar solution, lime and sugar react to form chelates. These chelates could be adsorbed on the nucleation center of Ca(OH) 2 and on C-S-H gels, thereby preventing cement from setting [ 20 ]; however, the addition amount of saccharides would affect the setting time of cement, and there was a critical dose of saccharides in retardation. On the one hand, when W/C was constant, the addition amount of saccharides was slightly lower than the critical dose, the formation of C-S-H was slow, and the setting time of cement was postponed.…”

“…When the addition amount of molasses and lignosulfonate increased from 0.25% to 0.50%, the air content in concrete increased from 0.3 and 1.6 to 0.6 and 2, respectively, and the slump increased from 14.5 cm and 17.5 cm to 18 cm and 20 cm, respectively. The air content could obviously change the workability of fresh concrete [ 20 ]. The slight difference in the slumps of the concretes in favour of the lignosulfonate-added one could be a result of the higher entrained air content of the latter concrete, because it is known that air entraining in concrete improves the workability, especially in lean mixes [ 21 , 22 ].…”

Review article: Atmospheric Pressure, Water with Air, Porosity and Strength of Concrete (In memory of Professor László A Gömze)

“…Finally, in 2020, Aneta Nowak-Michta once again showed that the problem of eliminating the porosity of concrete is not solved. Moreover, it showed that an attempt to in-crease the strength of concrete by additional introduction of modified polycarboxylates, which provide dilution of the concrete mix, leads not to a decrease, but to an increase in the porosity of concrete [60]. In the same year, the unsolved problem of concrete porosity was confirmed by Xiaohui Zeng and co-authors, who, based on a review of the literature, came to the conclusion that understanding of the mechanisms and main influencing [61].…”