Experimental Study on the Properties of Iron Mine Tailings Self-compacting Cement-based Materials
|School||Hefei University of Technology|
|Keywords||Iron mine tailings Self-compacting cement-based materials Rheology Mechanicalproperties Durability Pore structure Morphology and phase analysis|
The research, modern industrial waste used in the preparation of cement-based materials to eliminate or mitigate a serious impact on the environment, will become a focus area. Based on the reality of a large number of abandoned iron mine tailings produced from Huoqiu iron ore in Anhui province, the iron mine tailings was used as fine aggregate to replace part of the natural sand for self-compacting cement-based materials.The properites of iron mine tailings self-compacting cement-based materials were studies by the tests in this paper. The corresponding research works were summarized as follows:1. Raw materials of self-compacting cement-based materials were analyzed by Analysis of macroscopic features and microscopic techniques.The research contents were as follows:1) Analysis of macro-technical indicators;2) Qualitative and semi-quantitative analysis of raw materials were carried out by X-ray spectroscopy analysis(EDS);3) Phase analysis of raw materials was carried out by X-ray diffraction (XRD). The results can provide a basis for the properties of iron mine tailings self-compacting cement-based materials.2. The workability of iron mine tailings cement-based grouting material(IM) was studied with iron mine tailings ratio and water-binder ratio as variables.The results showed that performance index values of the workability for IM-2and M-lwere better than the others. The dynamic stability test and the static stability test were used the workability evaluation of iron mine tailings self-compacting concrete (ISCC) and self-compacting concrete (SCC). The results showed that ISCC-2and SCC-1had good work performances.3. Rheologies of IM and ISCC were first studies by the test methods in China.The Couette inverse problems for a Bingham fluid:"Reiner-Riwlin" equation and a Herschel-Bulkley fluid were derived by integration approach. The results showed that rheological curves of cement-based grouting material can meet Herschel-Bulkley fluid constitutive model with nonlinear characteristics, and IM-2had smaller shear stress than M-1when shear rates had the same values at the same point in time. Rheological curves of self-compacting concrete can meet Bingham fluid constitutive model with linear characteristics, and ISCC-2had greater shear stress than SCC-1when shear rates had the same values at the same point in time.4. Basic mechanical properites of iron mine tailings self-compacting cement-based materials were studies in different ages. The results showed that compressive strength of paste containing extre-fine natural sand was greater than paste containing iron mine tailings in different ages, but flexural strength had the opposite characteristics. Early compressive strength of cement-based grouting material rapid developed, and compressive strength of IM-2and M-1were more than 20MPa in one day age. There were similar growth laws for compressive strength of ISCC and SCC with ages, and the early strength development can be divided into three stages:the rapid development, the smooth transition and the steady growth.5. Carbonation resistance and anti-chloride penetration of ISCC and SCC has been studied to be used to reflect the durability. The results showed that carbonation ratesof ISCC-2and SCC-1were similar and had good performance of anti-chloride penetration.6. Pore characteristics and pore fractal dimension of cement-based paste and self-compacting concrete were studied by the mercury intrusion porosimetry (MIP) method. The results showed that pore characteristic parameters of three cement-based pastes change with can not find out apparent regularity. The test data of ISCC-2and SCC-1on pore characteristic parameters were close; the results showed that the microscopic pore structure of ISCC-2was not obvious deterioration trend after iron mine tailings added.7. Morphology, hydration products and micro-defects of three cement-based and two types of self-compacting concrete were investigated with ages by SEM, EDS and XRD, and the C-S-H gel was analyzed. The results showed that there were similar characteristics for early morphology of hydration products of three cement-based and two types of self-compacting concrete. Based on the phase analysis of the hydration products, new material has been found out when iron mine tailings involved in the hydration process.