Using Cement Paste Rheology To Predict Concrete Mix Design Problems

The complex interaction between cement and chemical/mineral admixtures in concrete mixture sometimes leads to unpredictable concrete performance in the field, which is generally defined as concrete incompatibilities. Cement paste rheology measurements instead of traditional workability tests can have a great potential to detect those incompatibilities in concrete before the concrete is placed to avoid setting time, workability, and curing-related issues, which sometimes leads to severe early-age cracking especially in severe weather conditions. The objective of the present study was to examine the applicability of the Superpave Dynamic Shear Rheometer (DSR) to measure cement paste rheology in one hand and identify cement and mineral/chemical admixtures incompatibilities based on cement paste rheological behavior on the other hand. Based on the extensive laboratory investigation, it is observed that DSR in modified form can measure cement paste rheology with permissible repeatability and sensitivity and has a great potential to identify cement and mineral/chemical admixture incompatibilities. The heat of hydration data from isothermal calorimeter test and setting time results for the studied mixtures have strongly supported the rheology-based observations. A procedure to formulate rheology-based acceptance criteria has been developed based on the available test results. Further refinement of these acceptance criteria based on detailed work covering a wide range of incompatibilities and validation through implementation efforts is warranted. This will ultimately help concrete producers and district laboratories to detect problematic combinations of concrete ingredients during the mixture design process. The researchers also investigated t he feasibility of the mini slump cone test as an alternative or supporting tool for the rheology test.

Estimating, modelling, controlling and monitoring the flow of concrete is a vital part of the construction process, as the properties of concrete before it has set can have a significant impact on performance. This book provides a detailed overview of the rheological behaviour of concrete, including measurement techniques, the impact of mix design, and casting. Part one begins with two introductory chapters dealing with the rheology and rheometry of complex fluids, followed by chapters that examine specific measurement and testing techniques for concrete. The focus of part two is the impact of mix design on the rheological behaviour of concrete, looking at additives including superplasticizers and viscosity agents. Finally, chapters in part three cover topics related to casting, such as thixotropy and formwork pressure. With its distinguished editor and expert team of contributors, Understanding the rheology of concrete is an essential reference for researchers, materials specifiers, architects and designers in any section of the construction industry that makes use of concrete, and will also benefit graduate and undergraduate students of civil engineering, materials and construction. Provides a detailed overview of the rheological behaviour of concrete, including measurement techniques, casting and the impact of mix design The estimating, modelling, controlling and monitoring of concrete flow is comprehensively discussed Chapters examine specific measurement and testing techniques for concrete, the impact of mix design on the rheological behaviour of concrete, particle packaging and viscosity-enhancing admixtures

This book presents the work of the RILEM TC 266-MRP, whose purpose was to enhance the reliability of rheological measurements performed on cement-based materials. It makes users more aware of potential sources of errors in the measurements, and provide guidelines on how to observe, counteract or eliminate the errors. Improving the reliability of rheological measurements will further enhance the use of rheology to investigate different aspects of the fresh properties of cement-based materials. After an introduction into mix design and applications, the book delivers a comprehensive overview of rheology definitions, behavior, and parameters; rheometers; measuring and analysis procedures; difficulties and challenges during measurements; relationships with specific empirical tests; and the behavior of concrete near a surface. This report on the measurement of rheological properties of complex materials such as concrete enables readers to understand the applicable concepts of rheology, and address the challenges on the measuring procedures, the rheological models and some errors and limitations of rheometers used.

"Robustness, which is defined as the capacity of a mixture to tolerate small variations in constituent elements, mixing parameters or temperature that are inevitable with production at any significant scale, is a key property to expand the practical implementation of self-consolidating concrete (SCC). At the first step, the effect of different amount of water, amount of superplastizer, mixing time, mixing speed and the addition time of superplastizer on the rheological properties of cement pastes with SCC consistency, has been evaluated. Two different SCC mix design concepts, the powder-type and VMA-type were selected for this research. The results show that the selected powder-type mix design is more robust than the VMA-type to a change in addition time of SP. Then, an experimental study was conducted to evaluate different mix design parameters by varying the binder combination, the type of PCE-SP and the addition of viscosity-modifying agent (VMA) to determine which particular parameters cause the largest difference in rheological behavior due to a variation in adding time of SP. In third step, the robustness of the "loss of workability" of flowable cement pastes, which is mainly affected by variations in the water content and the adding time of the superplasticizer, was evaluated. A comparison study was performed to develop a more accurate vision on robustness of cement paste, and also concrete, by taking into account the time-dependency of the rheological properties. Furthermore, the change in rheological properties of well-dispersed cement pastes subjected to different maximum shear rates has been conducted. It was shown that the choice of maximum shear rate during the rheological measurements is critical for the values of the rheological properties"--Abstract, page iv.

This book introduces fundamentals, measurements, and applications of rheology of fresh cement-based materials. The rheology of a fresh cement-based material is one of its most important aspects, characterizing its flow and deformation, and governing the mixing, placement, and casting quality of a concrete. This is the first book to bring the field together on an increasingly important topic, as new types of cement-based materials and new concrete technologies are developed. It describes measurement equipment, procedures, and data interpretation of the rheology of cement paste and concrete, as well as applications such as self-compacting concrete, pumping, and 3D printing. A range of other cement-based materials such as fiber-reinforced concrete, cemented paste backfills, and alkali-activated cement are also examined. Rheology of Fresh Cement-Based Materials serves as a reference book for researchers and engineers, and a textbook for advanced undergraduate and graduate students.

This book gathers the peer-reviewed contributions presented at two parallel, closely interconnected events on advanced construction materials and processes, namely the 2nd International RILEM Conference on Rheology and Processing of Construction Materials (RheoCon2) and the 9th International RILEM Symposium on Self-Compacting Concrete (SCC9), held in Dresden, Germany on 8-11 September 2019. The papers discuss various aspects of research on the development, testing, and applications of cement-based and other building materials together with their specific rheological properties. Furthermore, the papers cover the latest findings in the fast-growing field of self-compacting concrete, addressing topics including components’ properties and characterization; chemical admixtures, effect of binders (incl. geopolymers, calcined clay, etc.) and mixture design; laboratory and in-situ rheological testing; constitutive models and flow modelling; numerical simulations; mixing, processing and casting processes; and additive manufacturing / 3D-printing. Also presenting case studies, the book is of interest to researchers, graduate students, and industry specialists, such as material suppliers, consultants and construction experts.

This book introduces fundamentals, measurements, and applications of rheology of fresh cement-based materials. The rheology of a fresh cement-based material is one of its most important aspects, characterizing its flow and deformation, and governing the mixing, placement, and casting quality of a concrete. This is the first book to bring the field together on an increasingly important topic, as new types of cement-based materials and new concrete technologies are developed. It describes measurement equipment, procedures, and data interpretation of the rheology of cement paste and concrete, as well as applications such as self-compacting concrete, pumping, and 3D printing. A range of other cement-based materials such as fiber-reinforced concrete, cemented paste backfills, and alkali-activated cement are also examined. Rheology of Fresh Cement-Based Materials serves as a reference book for researchers and engineers, and a textbook for advanced undergraduate and graduate students.

This dissertation, "Effects of Water Content, Packing Density and Solid Surface Area on Cement Paste Rheology" by Hin-cheong, Henry, Wong, 黃憲昌, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled EFFECTS OF WATER CONTENT, PACKING DENSITY AND SOLID SURFACE AREA ON CEMENT PASTE RHEOLOGY submitted by Wong Hin Cheong Henry for the degree of Doctor of Philosophy at The University of Hong Kong in September 2007 High-performance concrete (HPC) has become increasingly popular in recent years. To produce HPC, addition of supplementary cementitious materials is virtually an essence. The use of these materials renders numerous possible mix combinations, making it difficult to optimize HPC mixes and limiting the usage of conventional mix design methods on HPC. In this regard, a comprehensive study aiming at developing a scientific mix design method for HPC has been launched. This thesis presents the findings on the first part of the study, which focuses on studying the scientific parameters governing the cement paste rheology. Due to the lack of a generally accepted method for measuring the packing density of cementitious materials, the postulation that the packing density has considerable influence on cement paste rheology has not yet been verified experimentally. Herein, a new wet packing method, which directly obtains the packing density by measuring the apparent density and voids content of cement paste, is developed. Using this method, the packing characteristics of pure ordinary Portland cement (OPC) and several blended cementitious materials measured under different conditions were acquired and compared with those obtained indirectly from consistence test. Based on the comparison, it is advocated that the packing density and water demand should be measured directly using the new wet packing method rather than other indirect methods. By using the wet packing method, the packing densities of cementitious materials containing OPC, pulverized fuel ash (PFA) and condensed silica fume (CSF) were measured. Results showed that the packing densities of pure cementitious materials could be improved by double blending and further increased by triple blending at appropriate proportions. The results also proved experimentally the postulation that packing density of cementitious materials could be improved by blending. Using the results, a ternary packing density diagram for determining the mix proportions for maximum packing density has been produced. Apart from experimental method, three existing packing models were also examined for their applicability on predicting the packing density of cementitious materials. By comparing the measured and predicted packing densities, together with some additional test results, it was found that in the presence of a third-generation superplasticizer the packing density of CSF is dependent on the lime content. When the effect of lime on the packing density of CSF is taken into accounted, very good agreement between the measured and predicted packing densities has been achieved, which verified the applicability of the models on cementitious materials. Although it is known that water content, packing density and solid surface area are the important parameters governing cement paste rheology, little progress has been made in evaluating the combined effect of these parameters on the rheology. In this thesis a new parameter called the excess water to solid surface area ratio is proposed to quantify the combined effect. A number of cement paste samples con