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最常用的材料。它的使用继续增长，以建立新的结构，以及满足日益增长的需要，维修现有的结构。预计到2020年，普通波特兰水泥的使用量将是1990年水平的三倍，而普通波特兰水泥是混凝土粘合能力的主要成分。由于已知每吨普通波特兰水泥产生0.8吨二氧化碳，因此通过使用辅助胶凝材料来减少水泥消耗对于减少与建筑业相关的温室气体排放是极其重要的。然而，辅助胶凝材料可能反应缓慢，并且在混凝土中更多地使用这种材料需要外部活化。辅助胶凝材料的外部活化可以产生具有类似于上级力学性能的粘结剂，并已用于实际施工中。然而，仍然有许多因素，包括由于水分损失导致的高早期变形和对长期时间依赖性变形的有限理解，影响其更广泛的使用。该提案将首次研究此类可持续替代粘合剂的处理及其与随时间变化的变形的关系，以最终控制变形。拟议的工作计划还旨在a）通过培养材料科学方面的土木工程研究生，B）鼓励大学生到中学生学习可持续基础设施材料，以及c）增加妇女和代表性不足的学生对研究的参与。本提案的研究目标是提供基本的理解，如何反应机制，以及在碱激活的可持续替代粘结剂的反应产物的分子和纳米结构的安排，由辅助胶凝材料，与时间相关的变形的粘结剂。该建议假设上述因素可以通过添加纳米晶晶种剂来控制。在本项目中，将通过使用高分辨率电子显微镜和X射线散射来研究添加纳米晶晶种剂对碱活化粘结剂的反应机理的影响。关于生长机制的精确信息将是变革性的，因为它将允许修改和可能改进现有模型对这种粘合剂的反应动力学的预测能力。通过这一提议获得的基本理解对于提高碱活化粘合剂对浸出、风化和其他化学降解的抗性同样重要，因为它们也取决于粘合剂的分子和纳米结构。

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.