Abstract
The experiment was coducted using synthetic zeolite (modification A) obtained in the laboratory of Kaunas University of Technology by means of low-temperature synthesis (below 105 °C). Aluminium fluoride (AIF3) production waste as well as sodium hydroxide NaOH and aluminium hydroxide Al(OH)3were used to obtain a complex zeolite admixture. SEM analysis revealed that synthetic zeolite admixture was made of modification A zeolite and gypsite. SEM analysis results were confirmed by X-ray analysis. Three batches of specimens were made to determine the effect of synthetic zeolite admixture on the durability of hardened cement paste. The first batch was without synthetic zeolite admixture, the second batch and the third batch contained 5 wt% and 10 wt% of synthetic zeolite admixture, respectively. Synthetic zeolite admixture was found to have a significant effect on the durability of the hardened cement paste. The weight loss in the hardened cement paste containing 5 wt% of the admixture was three times lower, whereas the weight loss in the hardened cement paste containing 10 wt% of the admixture decreased up to 100 times. Santrauka Tyrimams atlikti buvo naudojamas sintetinis ceolitas (A modifikacijos), gautas atliekant žematemperatūrę (iki 105 °C) sintezę. Kompleksiniam ceolitiniam priedui gauti naudota aliuminio fluorido (AIF3) gamybos atlieka, taip pat natrio hidroksidas NaOH ir aliuminio hidroksidas Al(OH)3. Darbe SEM analizės būdu buvo nustatyta, kad sintetinio ceolito priedas sudarytas iš A modifikacijos ceolito ir gipsito. Atlikti rengenografiniai tyrimai taip pat patvirtino SEM analizės duomenis. Norint nustatyti sintetinio ceolitinio priedo įtaką cementinio akmens ilgaamžiškumui, buvo suformuotos trys partijos bandinių. Pirmoji partija buvo be sintetinio ceolitinio priedo, antroji – su 5%, trečioji – su 10% priedo. Nustatyta, kad sintetinis ceolitinis priedas turi didelį poveikį cementinio akmens ilgaamžiškumui. Cementinio akmens su 5% priedo masės nuostoliai sumažėja apie tris kartus, o akmens su 10% priedo cemento masės nuostoliai sumažėja iki 100 kartų.
Highlights
IntroductionThe most frequently observed fact in the testing of concrete resistance to de-icing salt solutions is that concrete subjected to 3% NaCl solution has the lowest frost resistance
The deterioration of concrete structures exposed to salts is a significant problem and a big concern in North America and northern Europe
Cement and synthetic zeolite admixture were dosed by weight, water and chemical admixtures were dosed by weight
Summary
The most frequently observed fact in the testing of concrete resistance to de-icing salt solutions is that concrete subjected to 3% NaCl solution has the lowest frost resistance More tests in this field were made by Marchand, Kaufmann and other authors (Marchand et al 1999; Kaufmann 2000). The evaluations of the effect of the type of salt solution on the destruction of concrete structures and the researcher opinions differ. The authors advise to use Portland cement with low alite content (C3S) in frost resistant concrete manufacturing. Many authors offer ungrounded and often controversial reasons of such destruction without adequate evaluation of concrete frost resistance enhancing elements well know to concrete technologists, for instance SiO2 microparticles, ash, sodium silicate solution, air entraining admixtures ir plasticizers. As other pozzolanic substances, add greater strength to concrete compared to cement (Su et al 2000)
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