An alternative approach to improve the compatibility of PCE in cement paste blend with coal gangue powder

Coal gangue(CG)is an environmental waste that faces an urgent demand for disposal in China.The utilization of CG in construction materials has broad application prospects and gained increasing interest.However,the poor compatibility of polycarboxylate superplasticizer(PCE)with CG powder hinders its efficiency in a wide range of applications.Here,this paper attempts to improve the compatibility of PCE with CG powder in cement paste based on the regulation of aggregation and the adsorption behavior of PCE.Dynamic light scattering(DLS)and fluorescence spectroscopy tests were carried out to understand the improved mechanism.The results indicated that the addition of CG powder increases the ionic strengths of the cement liquid phase,which makes PCE tend to aggregate at a lower concentration compared with no CG powder introduction.Adding(CH_(3)COO)_(2)Cu is beneficial for enhancing the workability of cement paste by reducing PCE aggregation while maintaining the compressive strength of cement specimens.Therefore,(CH_(3)COO)_(2)Cu extra addition can be regarded as an effective and sustainable way to improve the workability of cement paste with CG powder.

Carbothermal Reduction Synthesis of Al_2O_3-SiC Powders from Coal Gangue

The Al2O3 -SiC composite powders were prepared in argon atmosphere rising coal gangue and carbonaceous materials （ carbon black, active carbon and antbravite） as starting materials by carbothermal reduction. Effects of excessive carbon addition, carbon types. temperature, soaking time. shaping pressure, types and amount of additives on phase composition and micro-structure of the Al2O3 - SiC composite powders were investigated. The re.suits indicate that： temperature, soaking time and chloride additi＇ve have significant influence on the synthesized Al2O3 -SiC composite powders. Based on the results, the optimized Al2O3 -SiC composite powders , Al2O3 58 mass% and SiC 42 mass%, with particle size d50 ≤5μm were prepared using coal gangue and carbon black as starting materials after 3 h firing at 1550 ℃. and proper additive addition could reduce the temperattlre by 50 ℃.