含游离石膏高铁硫铝酸盐水泥熟料的组成设计与性能研究

Composition Design and Properties of Calcium Ferroaluminate Cement Clinker Containing Free Gypsum

本工作在高铁硫铝酸盐水泥熟料中引入游离石膏相(以C_(2)S/CaSO_(4)比呈现),并将其与铁相和煅烧温度作为正交试验三个因素,探究三因素对高铁硫铝酸盐水泥矿物组成与力学性能的影响规律,并借助XRD和SEM-EDS等表征手段分析了水泥熟料的物相组成、微结构以及水化产物种类。结果表明:含游离石膏相的高铁硫铝酸盐水泥熟料的主要矿物组成为C_(4)A_(3)$、C_(2)S、铁相、C_(5)S_(2)$和游离石膏,其中铁相矿物的实际组成为C4AF且其含量均大于设计值,而C_(4)A_(3)$矿物含量的实际值均小于设计值。随着煅烧温度升高,熟料中C_(4)A_(3)$矿物颗粒尺寸变大,含量增加,而圆棒状的C_(5)S_(2)$矿物颗粒减少,分解成了游离石膏和C_(2)S,且团聚状的游离石膏附着在卵粒状的C_(2)S颗粒表面上。当铁相含量为25wt%,游离石膏相含量分别为6.65wt%和11.12wt%时,高铁硫铝酸盐水泥熟料中后期的抗压强度均表现良好,其中N-7样品力学性能最优,3 d和28 d抗压强度分别为40.4 MPa和52.1 MPa。以28 d抗压强度为考察指标,正交试验的最佳方案是A_(1)B_(3)C_(3),且在其28 d龄期水化产物中观察到较多的AFm相。

The free gypsum phase was introduced into the calcium ferroaluminate cement clinker,presented by the ratio of C_(2)S/CaSO_(4),and the ferrite phase and the calcination temperature as three orthogonal factors were used to investigate phase composition and mechanical properties of calcium ferroaluminate cement in this paper.Phase assemblage,microstructure and hydration products of cement clinkers were also analyzed by means of XRD and SEM-EDS.The results indicate that the main mineral compositions of calcium ferroaluminate cement clinker are C_(4)A_(3)$,C_(2)S,ferrite phase,C_(5)S_(2)$and free gypsum,and the actual composition of ferrite phase minerals is C4AF with content greater than designed.The actual content of C_(4)A_(3)$mineral is less than the designed content.With the increase of calcination temperature,the size of C_(4)A_(3)$particles in clinkers grew large with the content increasing,while the round rod-shaped C_(5)S_(2)$particles are reduced and decomposed into free gypsum and C_(2)S,and the agglomerated free gypsum was adhered to the surface of egg-shaped C_(2)S particles.The compressive strengths of the calcium ferroaluminate cement clinker are excellent in the middle and late stages when the ferrite phase content is 25wt%,and the content of free gypsum phase is 6.65wt%and 11.12wt%,respectively.The N-7 sample has the best mechanical properties,and the compressive strengths are 40.4 MPa and 52.1 MPa at 3 d and 28 d,respectively.The best scheme of the orthogonal test is A_(1)B_(3)C_(3),which takes the 28 d compressive strength as the index.More hydration products of AFm phase was observed at 28 d.