大掺量激活钢渣微粉-水泥稳定碎石性能及微观特性

为研究大掺量钢渣微粉-水泥稳定碎石的性能,采用自制复合激发剂激活钢渣微粉（ASSP）,开展了不同胶凝材料剂量（质量分数4%、5%和6%）大掺量（质量分数100%、90%、70%、50%）ASSP-水泥稳定碎石的7 d无侧限抗压强度（UCS）与5%胶凝材料剂量不同龄期（7,28,90 d）的UCS和劈裂强度（SS）试验;在此基础上,进行了5%胶凝材料剂量100%和70%ASSP-水泥混合料的抗压与劈裂回弹模量、抗冻性、干缩与温缩以及SEM、XRD微观试验,并与对照组P·S·A32.5水泥稳定碎石混合料性能进行了对比分析。结果表明：随着胶凝材料剂量增加,ASSP-水泥混合料的UCS和SS均越大,且同剂量下,70%和50%ASSP-水泥混合料强度与对照组的相当;通过调整胶凝材料剂量,大掺量ASSP混合料7 d的UCS完全能满足不同公路等级基层、底基层的要求;各ASSP-水泥混合料不同龄期UCS和SS、抗压与劈裂回弹模量的变化规律与对照组一致,均随剂量和龄期的增加而增大,抗冻性均满足要求;随ASSP掺量的增大,混合料干缩系数越小,温缩系数越大,掺入适量ASSP能减少混合料的干缩开裂;不同ASSP掺量混合料的主要水化产物为C-S-H、AFt和CH等,ASSP混合料的早期水化慢,水化产物数量少;28 d后70%ASSP混合料的水化产物C-S-H、AFt特征峰值与对照组相当,SEM结果与此一致;7 d后100%ASSP混合料胶凝浆体形貌和界面过渡区中浆体与骨料间连接不紧密,ASSP-水泥的浆体形貌较好,混合料结构密实,孔隙和裂缝的数量明显减少,较好地解释了混合料的宏观力学性能。可见,将大掺量ASSP-水泥稳定碎石用作路面基层完全是可行的,该研究为此类材料的推广应用提供了参考。

Performance and Micro Characteristics of Cement Stabilized Macadam with a Large Amount of Activated Steel Slag Powder

To discuss the performance of cement-stabilized macadam with large amount of activated steel slag powder, steel slag powder was activated by a self-made composite activator as an activated steel slag powder (ASSP). The 7-day unconfined compressive strength (UCS) of the ASSP-cement stabilized macadam for different cementitious dosages (4%, 5%, and 6%) and various large amounts (100%, 90%, 70%, and 50%) of ASSP and the UCS and splitting strength (SS) of different ages (7, 28 and 90 days) at 5% cementitious dosage were measured. The compressive and splitting resilient moduli, frost resistance, dry shrinkage and temperature shrinkage of 100% and 70% ASSP-cement mixtures at 5% cementitious dosage were then determined, and scanning electron microscope (SEM)and X-ray diffraction (XRD)micro tests were completed. For comparison, the corresponding properties of P·S·A 32.5 cement stabilized macadam mixture were ascertained. The results show that the UCS and SS of the ASSP-cement mixture increases with the increase in cementitious amount and that the strength of 70% and 50% ASSP mixture is equivalent to that of the control group under the same dosage. By adjusting the cementitious dosage, the 7-day UCS of the mixtures with a large amount of ASSP can fully meet the requirements of different highway-grade base and subbase. With increasing ASPP content, the changes in the UCS, SS, and compressive and splitting moduli of resilience with different ages were consistent with those of the control group, the values of which increased with the increase of dosage and age, and the frost resistance also met the requirements. Moreover, the dry shrinkage coefficient of the mixture became smaller, and the temperature shrinkage coefficient became larger, but the increment of average temperature shrinkage coefficient was far less than the decrease in the drying shrinkage coefficient, which indicates that adding ASSP to the mixture can reduce the cracking of the base course. The main hydration products of the mixture with different dosages of ASSP were C-S-H, Aft, and CH. However, early hydration of the mixture with ASSP was slow and the amount of hydration products was small. The characteristic peaks of C-S-H and AFt of the mixture with 70% ASSP in the later stage were equivalent to those of 0% ASSP and higher than those of 100% ASSP. The SEM results were consistent with the XRD results. The connection between the paste and the aggregate in the cementitious paste morphology and the interface transition zone in the 100% ASSP mixture was not close at the 7-day curing. However, by adding cement, the appearance of the ASSP cement paste improved, the structure of mixture densified, and the numbers of pores and cracks clearly decreased, which can better explain the macro mechanical properties of the mixture. The results demonstrate the feasibility of using large amounts of ASSP and cement stabilized macadam as a pavement base. This provides a reference for popularization and application of this kind of material.