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

混凝土是人类使用最多的材料，仅次于水。它的用途继续增长，以建造新的结构，以及满足日益增长的维修现有结构的需要。预计到2020年，普通硅酸盐水泥的使用量将是1990年水平的三倍。硅酸盐水泥是混凝土粘结能力的主要成分。每吨普通波特兰水泥会产生0.8吨二氧化碳，因此通过使用补充胶凝材料来减少水泥的消耗对于减少建筑行业的温室气体排放至关重要。然而，补充胶凝材料可能反应缓慢，并且在混凝土中更多地使用这些材料需要外部激活。补充胶凝材料的外部活化可以产生具有类似优异力学性能的粘结剂，并已在实际施工中得到应用。然而，仍然有许多因素影响了它们的广泛使用，包括它们由于水分损失而产生的高早期变形和对长期时间依赖性变形的有限理解。本提案将首次研究这种可持续替代粘合剂的加工及其与时间相关变形的关系，以最终控制它。拟议的工作计划还旨在a)通过培训材料科学土木工程研究生来促进研究和教育的整合，b)鼓励本科生到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。本提案的研究目的是提供基本的认识，如何反应机制，以及反应产物的分子和纳米结构排列的碱活化替代粘合剂由补充胶凝材料制成，与粘合剂的时间依赖性变形相关。本研究假设上述因素可以通过添加纳米晶播种剂来控制。本项目将通过高分辨率电子显微镜和x射线散射技术研究纳米晶播种剂的加入对碱活化粘合剂反应机理的影响。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抗浸出、开花和其他化学降解的能力同样重要，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.