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Inner Mongolia Agricultural University (2019)

A Study of Durability and Service-Life Prediction Models for Aeolian Sand Powder Concretc

李根峰;

Titre : A Study of Durability and Service-Life Prediction Models for Aeolian Sand Powder Concretc

Auteur : 李根峰;

Grade : Doctoral Dissertation 2019

Université : Inner Mongolia Agricultural University

Résumé partiel
In the present study,aeolian sand powder samples were prepared using the widely distributed aeolian sand of Inner Mongolia(China),and a principle of "alkali activation"was adopted to stimulate the experimental activities.Meanwhile,aeolian sand powder concrete samples were prepared by replacing the cement-based cementitious material.Then,examinations were conducted regarding the deterioration and damage processes,as well as the deterioration mechanism of the aeolian sand powder concrete under both single and coupled conditions.These included freeze-thaw conditions,salt leaching,dry-wet conditions,carbonization,and sand erosion.The macroscopic properties were observed using such indexes as the relative dynamic elastic modulus,mass losses,carbonization depths,and the corrosion resistance coefficients of the compressive strength.The micro-morphology,micro-mechanics,hydration products and pore variation were studied by field emission scanning electron microscopy(FESEM),nanoindentation technique(NI),energy dispersive spectroscopy(EDS),X-ray diffraction(XRD),semi-quantitative full spectrum analysis(SQFSA)and nuclear magnetic resonance(NMR).Then,on the basis of this study’s macroscopic and microscopic experimental results,the activation mechanism of the aeolian sand powder,along with the durability of the aeolian sand powder concrete,were discussed in detail.The results of this study’s experimental processes revealed the following:1.During the modification tests of the aeolian sand powder,the activation rates of the aeolian sand powder were observed to have increased with the increases in the mass fractions of the activators.Also,with the increases in the alkalinity of the solutions,the dissolution amounts of the SiO2 and other active substances in the aeolian sand powder were found to have gradually increased.It was found that the results of the sodium sulfate powder were superior to those of the sodium hydroxide in regard to the modified effects of the aeolian sand powder.It was also determined that when the aeolian sand powder content was 15%and the sodium sulfate content was 2.0%,along with a pre-curing temperature of 35℃,the ettringite in the aeolian sand powder of the cement mortar specimen was highly developed.It had become fully filled in the intermal pores of the aeolian sand powder-cement gel system,and the intermal pores below 20 nm in the disconnected wool stoma had reached 85.69%.The proportion of the irreducible fluid saturation had also been increased to 94.311%,and the activity index had reached as high as 108.2%.2.With the increases in the number of freeze-thaw cycles,it was observed that the relative dynamic elastic modulus of the aeolian sand powder undergoing the coupling effects of the freeze-thaw and salt leaching conditions had first increased,then stabilized,and then dropped to the law of failure.At the same time,the aeolian sand powder concrete had produced an ettringite(AFt)in the magnesium sulfate solution of 3.0%>6%,gypsum(CaSO4)ean also be formed in 6.0%magnesium sulfate solution,and the needle columnar fibrous products had filled cracks caused by the frost-swelling stress conditions experienced by the concrete samples.

Mots clés : Aeolian sand; Aeolian sand powder concrete; Freeze-thaw; Salt leaching; Dry-wet; Carbonization; Aeolian sand erosion; Nuclear magnetic resonance; Service life;

Présentation (CNKI)

Page publiée le 3 février 2021, mise à jour le 25 novembre 2021