Effect of the addition of kraft lignin from eucalyptus wood in the rheology of a CAP 50/70

ABSTRACT The study and development of new technologies for paving materials has been greatly motivated by the many problems that pavements have faced. Currently synthetic polymers have already taken their place in the market for the efficiency they have presented in several studies and when tested in service. However, this dependence on fossil fuels is of concern, mainly because of the environmental impact resulting from such use. Thus, alternatives based on renewable resources and still taken advantage of industrial processes have gained space. Lignin is a natural polymer, a byproduct of the pulp and paper industry, extracted from wood in the form of a black liquor by various processes, the kraft process being the main and most used. This material has already demonstrated great potential in some researches due to its association with the asphalt binder, mainly because it has antioxidant properties. Thus, this research aimed to verify the effect of the addition of lignin at 3%, 6% and 9% in the rheological properties of a conventional asphalt binder CAP 50/70 before and after the short term aging (RTFO). Conventional tests of penetration, softening point and elastic recovery were carried out in addition to special tests such as rotational viscosity and those performed in the DSR, in order to determine the parameters of the degree of performance, G *, δ and G*/sin δ, in addition to % Rec and Jnr, the latter through the MSCR. It was found that the binders modified by addition of lignin were more resistant to temperature variation, to permanent deformation, but mainly to aging, showing the performance of this material as an antioxidant, especially for the 9% content, although the other contents also have shown superior performance to the pure binder, proving that the use of lignin in general has proved to be viable both rheologically and environmentally when it is associated with the conventional binder.

摘要 道路工程面临诸多共性难题，极大推动了路面材料新技术的研究与开发。当前，合成聚合物凭借多项研究及现场服役测试中展现的优异性能，已在路面材料市场站稳脚跟。然而，此类材料对化石燃料的依赖引发广泛担忧，核心原因在于其生产使用过程中带来的环境负面影响。因此，基于可再生资源且可依托现有工业流程开发的替代材料逐渐获得关注。木质素是一种天然高分子，为制浆造纸工业的副产物，可通过多种工艺从木材中以黑液形式提取，其中硫酸盐法制浆工艺（kraft process）是主流且应用最广泛的提取手段。该材料因可与沥青胶结料复掺且自身具备抗氧化特性，已有多项研究证实其具备巨大应用潜力。本研究旨在验证掺量分别为3%、6%、9%的木质素对常规沥青胶结料CAP 50/70在短期老化（RTFO）前后的流变性能影响。试验涵盖针入度、软化点、弹性恢复率等常规性能测试，以及旋转黏度、动态剪切流变仪（DSR）测试等专项试验，以测定关键性能参数：复数剪切模量G*、相位角δ、G*/sinδ，以及弹性恢复率% Rec和不可恢复柔量Jnr，其中Jnr通过多应力重复蠕变恢复试验（MSCR）测得。研究结果显示，掺加木质素的改性沥青胶结料具备更优异的抗温变性能、抗永久变形能力，尤其在抗老化性能上表现突出，验证了其作为抗氧化剂的应用价值，其中以9%掺量的改性效果最为显著；尽管其余掺量的改性性能也优于纯沥青胶结料，整体而言，将木质素与常规沥青胶结料复掺无论从流变性能还是环保维度出发均具备实际应用可行性。