矿物掺合料对水泥基材料化学收缩与光谱性能的影响

Effect of mineral admixture on chemical shrinkage and spectral properties of cement-based materials

为了研究矿物掺合料对水泥基材料收缩性能的影响规律,对不同矿物掺合料(锂渣、粉煤灰、钢渣)、不同掺量(20%和60%)、不同水胶比(0.30和0.40)下水泥基材料的化学收缩和光谱特性进行研究,同时分析化学收缩与浆体中官能团之间的相关性。结果表明:水泥基材料的化学收缩大致可以分为加速阶段、变缓阶段和平缓阶段且可采用双曲线模型来拟合,相关系数在0.98以上。矿物掺合料等质量替代水泥后,水胶比为0.40且掺量为20%时,水泥-锂渣浆体、水泥-粉煤灰浆体和水泥-钢渣浆体的最大化学收缩分别约为纯水泥浆体的81.2%、97.2%和91.0%,掺量由20%增加至60%时,水泥-锂渣浆体、水泥-粉煤灰浆体和水泥-钢渣浆体的最大化学收缩分别降低了1.9%、1.8%和5.0%。可见水泥-粉煤灰浆体的化学收缩最大,水泥-钢渣浆体的化学收缩次之,水泥-锂渣浆体的化学收缩最小。4种水泥基材料的波谱相似,均以3 647、3 451、2 937、2 361、1 651、1 418、1 124、978和451 cm^(-1)为主要的特征峰,其中水泥基材料的化学收缩受波数1 124、3 451、1 418、978、3 647 cm^(-1)的影响较大。该研究可为矿物掺合料在混凝土中的合理选用提供依据。

Chemical shrinkage of cement paste could result in the crack of concrete, which affects the volume stability and durability of concrete. In order to reduce the shrinkage performance of concrete, this paper discusses the effect of common mineral admixture（lithium slag, fly ash, steel slag） on the chemical shrinkage and the spectral characteristics of cement paste, and analyzes the correlation between the chemical shrinkage of cement paste and the functional groups in cement paste. The results are as follows： The chemical shrinkage of pure cement paste and cement paste containing mineral admixtures（lithium slag, fly ash, steel slag） can be roughly divided into 3 stages, namely the acceleration phase（within 100 h）, slow phase（ in 100-700 h）, and flat stage（after 700 h）. When the ratio of water-binder is 0.40 and the admixture dosage is 20% for 3 kinds of admixture, the chemical shrinkages of cement-lithium slag, cement-fly ash and cement-steel slag paste are 81.2%, 97.2% and 91.0%, respectively, and they are reduced by 1.9%, 1.8% and5.0% when admixture content increases from 20% to 60%, respectively. The chemical shrinkages of cement, cement-lithium slag, cement-fly ash and cement-steel slag paste are 24.4%, 32.3%, 26.8% and 29.7% respectively when the ratio of water-binder reduces from 0.40 to 0.30 and the admixture content is 20%. The chemical shrinkage of 4 kinds of paste can be fitted with hyperbolic model, and the correlation coefficients are above 0.98. So, hyperbolic model can be used to predict the final chemical shrinkage of cement paste, but the hydration coefficient value can be chosen according to the ratio of water-binder, and kind and dosage of admixture. The chemical shrinkage and hydration heat are lowered when cement is replaced by the same quality lithium slag, fly ash or steel slag, and the chemical shrinkage of cement-fly ash paste is the biggest, followed by the chemical shrinkage of cement-steel slag paste, and the chemical shrinkage of cement-lithium slag paste is the minimal, which is lower than that of pure cement paste. In addition, water-binder ratio also affects the chemical shrinkage of cement paste and the effect of water-binder ratio is higher than lithium slag, fly ash and steel slag. The spectral characteristic of cement paste is affected by mineral admixture type, dosage of mineral admixture and water-binder ratio, but their influence is not the same, mainly due to the different chemical composition in lithium slag, fly ash and steel slag. The main characteristic peaks of pure cement paste and cement paste containing mineral admixtures（lithium slag, fly ash, steel slag） are 3 647, 2 937, 3 451, 1 651, 2 361, 1 124, 1 418, 451 and 978 cm^-1. Through the analysis of the general linear single variable model in SPSS 20.0 statistical software, it is found that the chemical shrinkage of cement paste can be affected by functional groups in the cement paste, and the effect is bigger when the wave number is 1 124, 1 418, 3 451, 3 647 and 978 cm^-1. Through the study, it is found that after the same quality mineral admixture（lithium slag, fly ash, steel slag） is used to replace cement, the chemical shrinkage of cement paste can be effectively reduced, and the spectral properties of cement paste can be changed. Therefore, the mineral admixture can be chosen according to the situation of the mineral admixture in actual engineering, so as to enhance the volume stability and durability of cement concrete with mineral admixture（lithium slag, fly ash, steel slag）.