The Performance of Coal Gasification Coarse Slag-weathered Sand Composite Fine Aggregate Concrete

CGCS （coal gasification coarse slag） and desert sand composite aggregate replacing river sand for the preparation of concrete （coal gasification coarse slag and desert sand composite fine aggregate concrete,abbreviated as CDFC） were investigated to study the effect of different CGCS dosages,the sand rate of concrete,and the dosage of fly ash （FA） in cementitious material on the mechanical properties of the concrete and the excessive zone at the aggregate interface.The experimental results show that,with the increase of CGCS admixture,the CDFC water-cement ratio decreases,and the strength shows first increase and then decrease;with the increase of concrete sand rate,the CDFC strength shows first increase and then decrease,and with the increase of FA,the CDFC strength shows first increase and then decrease,when the dosage of cementitious material is 360 kg/m3,the composite fine aggregate dosage is 872 kg/m3,and the coarse aggregate dosage is 983 kg/m3,the maximum compressive strength of its CGCS is 47.4 MPa.The microstructures of CGCS and hydration products were analyzed by X-ray fluorescence spectrometry （XRF）,X-ray diffraction （XRD）,Fourier transform infrared spectrometry （FTIR）,and scanning electron microscopy （SEM）.It is found that the CDFC as fine aggregate can generate hydration products such as hydrated calcium silicate gel （C-S-H） in the transition zone of the concrete interface,which can greatly improve the weak zones of the concrete,and improve the strength.