Fundamental Study on Sustainable Alternative Binders for Concrete: Reduction of Long-Term Time Dependent Deformation through Nanoengineering

混凝土是仅次于水的人类使用最多的材料。它的使用继续增加，以建造新的结构，以及满足日益增长的对现有结构的维修需求。预计2020年普通波特兰水泥的使用量将是1990年水平的三倍。普通波特兰水泥是混凝土粘结能力的主要成分。众所周知，每吨普通波特兰水泥会产生0.8吨二氧化碳，通过使用辅助胶凝材料来减少水泥消耗量，对于减少与建筑业相关的温室气体排放至关重要。然而，辅助胶凝材料的反应可能很慢，在混凝土中更多地使用这种材料需要外部激活。辅助胶凝材料的外部活化可以产生类似于优异力学性能的粘结剂，并已在实际施工中使用。然而，仍然有许多因素影响其更广泛的使用，包括由于水分损失而导致的早期变形较高，以及对长期依赖时间的变形的了解有限。这项提案将首次研究这种可持续替代粘结剂的加工及其与依赖时间的变形的关系，以最终控制它。拟议的工作计划还旨在a)通过培训土木工程研究生学习材料科学，促进研究和教育的一体化；b)鼓励本科生通过中学生学习可持续基础设施材料；c)增加妇女和代表性不足的学生参与研究。该方案的研究目的是从根本上理解由辅助胶凝材料制成的碱激发可持续替代粘结剂中的反应机理以及反应产物的分子结构和纳米结构排列与粘结剂的时间依赖变形之间的关系。这一建议假设上述因素可以通过添加纳米晶播种剂来控制。在本项目中，将通过高分辨电子显微镜和X射线散射来研究纳米晶种子剂的添加对碱激发粘结剂反应机理的影响。关于生长机制的准确信息将是变革性的，因为它将允许修改和可能提高现有的此类粘结剂反应动力学模型的预测能力。通过这一建议实现的基本理解对于提高碱活性粘结剂的抗淋滤、风化和其他化学降解性能同样重要，因为它们还取决于粘结剂的分子结构和纳米结构。

Concrete is second only to water as the most used material by humans. Its use continues to grow to build new structures as well as to meet an increasing need for repair of existing structures. The projected use of ordinary Portland cement, the main component responsible for binding capacity of concrete, in 2020 is to be three times the level of 1990. As every ton of ordinary Portland cement is known to produce 0.8 tons of carbon dioxide, reduction of cement consumption by use of supplementary cementitious materials is extremely important to reduce greenhouse gas emission associated with construction industry. However, supplementary cementitious materials can be slow to react and greater use of such materials in concrete requires external activation. External activation of supplementary cementitious materials can produce binders with similar to superior mechanical properties and have been used in actual construction. However, there are still many factors, including their high early age deformation due to moisture loss and limited understanding of long-term time dependent deformation, that affect their wider use. This proposal, for the first time, will study processing of such sustainable alternative binders and its relationship with time-dependent deformation to ultimately control it. The proposed work plan also aims to a) advance the integration of research and education through training civil engineering graduate students in materials science, b) encourage study of sustainable infrastructure materials among undergraduates through middle school students and c) increase participation of women and underrepresented students in research. The research objective of this proposal is to provide fundamental understanding of how the reaction mechanisms, and the molecular and nano structural arrangements of the reaction products in alkali activated sustainable alternative binders made from supplementary cementitious materials, are related to the time dependent deformation of the binder. This proposal hypothesizes that the abovementioned factors can be controlled through the addition of nanocrystalline seeding agents. In this project, the effects of the addition of nanocrystalline seeding agents on the reaction mechanism of alkali activated binders will be studied through the use of high resolution electron microscopy and X-ray scattering. Precise information on the growth mechanism will be transformative as it will permit modification and possibly improvement of predicting capability of existing models for reaction kinetics of such binders. Fundamental understanding achieved through this proposal will be equally important for improving resistance of alkali activated binders against leaching, efflorescence and other chemical degradations as they also depend on the molecular and nanostructure of the binder.