Development of Non-Clinker Based Cement for Hazard Reduction

混凝土一直是美国1.4万亿美元基础设施建设的首选材料。随着人口、工业化和城市化的快速增长，混凝土材料中使用的水泥越来越多，以满足日益增长的基础设施需求。因此，与波特兰水泥熟料生产有关的环境问题，如温室气体（二氧化碳、一氧化碳）排放和水泥生产副产品水泥窑粉尘（CKD）的处理，变得越来越重要。美国水泥工业每年产生约8000万吨二氧化碳和500万吨CKD。废弃CKD的处理不仅涉及土地使用问题，而且还涉及材料中化学物质（特别是重金属）的浸出对地下水的污染。同样，另一种工业副产品，从发电厂燃烧煤粉的烟囱气体中收集的粉煤灰，也通常被认为是一种广泛的废物。美国每年产生约5900万吨粉煤灰，其中80%被填埋。本研究的目标是探索一种有效的方法，通过开发一种环境友好、性能充分、成本有效的水泥产品（不含硅酸盐水泥熟料）来大量利用CKD和粉煤灰，用于未来的混凝土材料。CKD和粉煤灰已被少量用作混凝土的补充胶凝材料。由于这两种材料的不足，使用受到限制。例如，CKD含有过多的细颗粒和高碱含量，这通常会对混凝土的和易性和耐久性产生，，，，不利影响。大多数粉煤灰的水化速度很慢，有些含有很高的未燃烧碳含量。这些缺陷对于水泥和混凝土材料的强度发展和体积稳定性是不可接受的。然而，如果两种材料混合在一起，来自CKD的碱可能会激活粉煤灰的水化作用。提出的研究包括适当地将CKD与粉煤灰混合，以创造一种胶凝材料，其中材料的不足将转化为优势。拟议的研究计划包括六个主要任务：(1)原材料表征，(2)混合比例的统计设计和优化，(3)研磨过程，(4)混合材料化学和机械活化有效性的测试和评估，(5)制定新产品的验收标准，(6)测试和评估用新产品制成的混凝土的性能。任务2包含四个连续的步骤：设计、初步优化、改进和构造，从而有序地开发最佳混合物。通过一系列的化学、物理和力学实验来评估每一步优化的产品性能，从而不断得出下一个最优的混合配比步骤。系统研究不同磨矿工艺及其对碱活化和水泥水化的影响，以及促进水泥水化的养护条件。因此，四个关键问题，(a)碱活化，(b)高能磨矿，(c)比例优化，(d)产品性能，被整合到提出的无熟料ckd粉煤灰水泥的开发中。新产品的性能是通过定制化学、微观结构和制造工艺来设计的。一个跨学科的合作研究团队已经成立，包括来自伊利诺伊州埃文斯顿西北大学（NU）先进水泥基材料中心（ACBM）和伊利诺伊州斯科基建筑技术实验室公司（CTL）的成员。团队成员在混凝土材料科学、统计设计和分析、水泥化学、制造、指南开发以及混凝土测试和性能等领域具有互补的优势。通过共同努力，他们希望将CKD和粉煤灰从目前的环境负担和工业利润“小偷”成功转化为可行的建筑材料。

Concrete has been the material of choice for the nation's $1.4 trillion infrastructure. The rapid growth of human population, industrialization, and urbanization has led to more cement being used in concrete materials to meet the increasing needs of infrastructure. As a result, the environmental concerns related to portland cement clinker production, such as greenhouse gas (carbon dioxide, CO Z) emission and disposal of cement kiln dust (CKD), a by-product of cement manufacturing, have become increasingly important. The United States cement industry generates about 80 million tons of CO 2 and 5 million tons of CKD every year. The disposal of waste CKD is not only associated with the problem of land use but also with the contamination of ground water from leaching of chemicals (especially heavy metals) in the material. Similarly, another industrial by-product, fly ash, collected from the stack gases of power plants burning pulverized coal, is also commonly considered an extensive waste material. About 59 million tons of fly ash are generated annually in the United States and 80% is placed in landfills. The goal of the proposed research is to explore an effective way to substantially utilize CKD and fly ash by developing an environmentally friendly, sufficiently performing, and cost effective cementitious product (without portland cement clinker) for future concrete materials.CKD and fly ash have been used as a supplementary cementitious material in concrete in small amounts. Usage is limited due to deficiencies of the two materials. For example, CKD contains an excessive amount of fine particles and a high alkali content, which often impart a,,,,erse effects on concrete workability and durability. Most fly ash hydrates slowly and some contain a high unburned carbon content. These inadequacies are unacceptable for strength development and volumetric stability of cement and concrete materials. However, if the two materials are blended together, the alkalis from CKD may activate hydration of fly ash. The proposed research involves properly blending CKD with fly ash to create a cementitious material in which the material deficiencies will be converted into benefits.The proposed research program includes six major tasks: (1) raw material characterization, (2) statistical design and optimization of blend proportions, (3) the grinding process, (4) testing and evaluation for effectiveness of chemical and mechanical activation of the blends, (5) developing criteria for acceptance of new products, and (6) testing and evaluation for performance of concrete made with the new products. Task 2 contains four successive steps: design, preliminary optimization, refinement, and conformation, thus developing optimal blends orderly. A series of chemical, physical, and mechanical experiments will be used to evaluate product performance at each step of optimization, thus leading to the next optimal step of blend proportioning continuously. A systematical study of different grinding processes and their affect on alkali activation and cement hydration will be conducted along with the curing conditions that promote such hydration. Thus, four key issues, (a) alkali activation, (b) high-energy grinding, (c) proportion optimization, and (d) product performance, are brought together into the proposed development of a non-clinker CKD-fly ash cement. The new product performance is engineered by tailoring the chemistry, microstructure, and manufacturing process.An interdisciplinary collaborative research team has been formed, consisting of members from the Center for Advanced Cement-Based Materials (ACBM) at Northwestern University (NU), Evanston, Illinois, and Construction Technology Laboratories, Inc. (CTL ), Skokie, Illinois. The team members have complementary strengths needed for the proposed research, with expertise in the areas of concrete material science, statistical design and analysis, cement chemistry, manufacturing, guideline development, and concrete testing and properties. Working together, they expect the successful conversion of CKD and fly ash from a current environmental burden and industrial profit "thief' into a viable construction material.