Magazine of Concrete Research http://dx.doi.org/10.1680/macr.14.00313 Paper 1400313 Received 24/09/2014; revised 24/10/2014; accepted 22/12/2014 ICE Publishing: All rights reserved Magazine of Concrete Research Effects of paste-to-voids volume ratio on performance of self-consolidating concrete mixtures Wang, Taylor, Wang and Morcous Effects of paste-to-voids volume ratio on performance of self- consolidating concrete mixtures Xuhao Wang Research Assistant, Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, Iowa, USA Peter Taylor Associate Director, National Concrete Pavement Technology Center, Iowa State University, Ames, Iowa, USA Kejin Wang Professor, Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, Iowa, USA George Morcous Associate Professor, The Durham School of Architectural Engineering and Construction, University of Nebraska-Lincoln, Omaha, USA A well-proportioned self-consolidating concrete (SCC) mixture can be achieved by controlling the aggregate system, paste quality and paste quantity. This study aims to apply a concept that is based on paste-to-voids volume ratio (V paste /V voids ) to assess the performance of SCC mixtures. The relationship between excess paste theory and V paste / V voids was investigated. Tests were conducted on a large matrix of SCC mixtures that were designed for cast-in-place concrete construction. The mixtures were made with different aggregate types and sizes, and different cementitious materials. The workability, flow properties, compressive strength, shrinkage and surface resistivity of SCC mixtures were determined as indicators of SCC performance. Statistical analyses, response surface models and Tukey honest significant difference (HSD) tests, were conducted to relate the mix design parameters to the concrete performance. Test results revealed that slump flow of the SCC mixtures increased with V paste /V voids at a given viscosity. Strength increases with V paste /V voids up to a point (,150%), after which the strength becomes independent of V paste /V voids . V paste /V voids has little effect on the shrinkage of SCC mixtures, or their surface resistivity. Statistical analysis is an efficient tool to identify the significance of influencing factors on concrete performance. Notation D av the average aggregate diameter D pi projected diameter of the particles in size class i D ss average spacing between aggregate particle surfaces (particles are assumed to be spherical) d i average size of aggregate fraction i m i percentage of aggregate mass retained between upper and lower sieve sizes in fraction i n i number of particles in size class i P e volume of excess paste s i surface area of particles in size class i t final flow time until concrete stops flowing t 50 flow time for SCC mixture to reach a diameter of 500 mm V c total concrete volume V p paste volume V voids volume of voids in densely compacted aggregate determined in accordance with ASTM C29 V paste /V voids paste-to-voids volume ratio ç plastic viscosity ô dynamic yield stress Introduction The overall performance of self-consolidating concrete (SCC) ‘combines concrete’s existing ability to produce a wide range of engineering properties with an increased potential for construct- ability that exceeds anything possible with conventional concrete (CC)’ (Daczko, 2012). Nowadays, how to achieve a quality SCC with minimum impact, while meeting application requirements, has become a key issue in designing mix proportions. A critical aim of research dedicated to mix proportioning is to ensure that SCC mixtures have better performance and sustainability. A well-proportioned SCC mixture can be achieved by controlling the aggregate system, paste quality and paste quantity. The unique features of SCC mixtures are the fresh properties: flow ability, passing ability, filling capacity and stability. This can be obtained by properly selecting the aggregate system and paste quantity. However, other concrete properties, such as mechanical properties, shrinkage and permeability, need to be assessed as well. These are largely controlled by the paste quality, such as water-to-cementitious material ratio, supplementary cementitious material (SCMs) types and dosages, and use of chemical admix- tures. This study is aimed at applying a concept that is based on a paste-to-voids volume ratio (V paste /V voids ) to assess the perform- ance of SCC mixtures. Aggregate system and paste quality are varied in order to comprehensively understand the influences of V paste /V voids in a given paste system. 1