Papers by Keyword: Alkali Content

Abstract: A laboratory study was carried out to investigate the ability of neutralization of red mud(RM) using carbon dioxide gas at ambient conditions. It was to evaluate the removal of alkali in the red mud using CO₂.The neutralized red mud was characterized by X-ray diffraction(XRD) , FP-640 flame photometer and auto titration method. XRD patterns of red mud revealed that the intensity of sodalite was decreased by using CO₂. The pH of red mud was decreased from 11 to 8 . The specific advantages of these processes are that, through adding with hydrochloric acid(HCl) and N-Methyldiethanolamine(MDEA), the removal of alkali in the red mud (Na₂O) was decreased from 12.5% to 2.3% by adding with HCl.What is more , the removal ratio of sodium oxide in the red mud by adding with HCl can be received at 80%.

Abstract: The influence of Al₂O₃ on alkali content in concrete pore solution was investigated, Al₂O₃ was added into concrete by bauxite. The quartz glass as active aggregate was dipped in the NaOH solution with Al³⁺ and without Al³⁺ respectively. The morphology of the products was observed by scanning electron microscope, the element composition was analyzed by Energy analyzer and the mineral composition was measured by X-ray diffractometer. The results showed that alkali content in pore solution can be reduced effectively by Al₂O₃. The more content of Al₂O₃, the lower alkali content in pore solution. The existence of Al³⁺ changed the ASR products. The products inclined to crystal rather than gel and zeolite was formed. Therefore, the decrease of alkali content in pore solution and transformation of ASR products were the reasons of the substance containing aluminum inhibition ASR.

Abstract: This study has investigated the controlling ASR with high quality I class fly ash. The results show that the content of fly ash is more important than the quality of fly ash for the effect on preventing ASR. The solubility of alkali in fly ash has been studied in various alkali concentration solutions. The mechanism of a low content of fly ash accelerating swell of concrete but a high content of fly ash controlling swell is discussed for controlling ASR with fly ash contained high alkali content.

Abstract: In-situ inspection and lab study were combined to analyze the prestressed concrete girders of an existing railway bridge built in 1976 in North China. The reactive components in aggregates and the alkali content of concrete were investigated. Typical reaction product was found in site and was analyzed in lab. Residual expansion of concrete cores drilled from some girders was measured. From test results, it can be deducted that alkali silica reaction had affected the concrete girders and would continue to cause expansion in the future.