Concrete Equivalent Mortar Research Articles

Relationships Between Key ASTM Test Methods Determined on Concrete and Concrete-Equivalent-Mortar Mixtures

Abstract Concrete batching requires considerable amounts of materials, energy, and time for testing. This highlights the importance of using alternative easier approaches based on mortars to simplify and speed up the experimental testing programs. This paper seeks to establish relationships between responses of ASTM Test Methods conducted on concrete and concrete-equivalent-mortar (CEM). Different series of mixtures having various cement contents of 300, 350, 400, and 450 kg/m3 and water-to-cement ratios of 0.4, 0.45, 0.5, 0.55, and 0.6 were tested. Test results showed that the CEM approach can adequately predict the slump, slump variations, water reduction, air content, setting time, and compressive strength of concrete with coefficients of correlation (R2) greater than 0.86. Conversely, moderate relationships were obtained when correlating the flexural strength and length change responses of concrete to those determined on CEM. This was mainly attributed to variations in the specimen dimensions and effect of the interfacial transition zone resulting from the presence of coarse aggregates.

Correlating Rheology of Self-Consolidating Concrete to Corresponding Concrete-Equivalent Mortar

The investigation reported in this paper seeks to develop a methodology to evaluate the rheological parameters and thixotropy of self-consolidating concrete (SCC) using those of concrete-equivalent mortar (CEM). The mixture proportioning of CEMs are derived from their corresponding concrete mixtures by eliminating the coarse aggregate fraction and replacing it by a certain mass of sand of the same surface area. SCC mixtures with water-cementitious material ratios (w/cm) of 0.35, 0.38, and 0.42 and coarse aggregate-total aggregate volume ratios (CA/A) of 0.44 to 0.53 were investigated. The mixtures with a w/cm of 0.38 and 0.42 incorporated low and moderate dosages, respectively, of a viscosity-modifying admixture to enhance stability. For each SCC, the dosage of high-range water-reducer (HRWR) was varied to cover a wide range of slump flow consistencies ranging between 570 and 730 mm (22.4 and 28.7 in.). All SCC mixtures were proportioned with 450 kg/m 3 (758.5 lb/yd 3 ) of ternary silica fume-ground granulated blast-furnace slag cement. A simple method is also proposed to determine the HRWR demand of SCC from that of the corresponding CEM. Test results showed that a good correlation can be established between the yield stress, plastic viscosity, and thixotropy of SCC and their corresponding CEM mixtures. Both thixotropy and plastic viscosity of SCC mixtures and their corresponding CEM mixtures are shown to vary primarily with variations in the w/cm and relative volume of coarse aggregate.

Development of a Plane Isothermal Calorimeter: Relating Apparent Activation Energy of Concrete and the Corresponding Mortar

Abstract This article describes the development and application of a new plane isothermal calorimeter with reduced and adjustable thickness. This innovative calorimeter allows the study of highly reactive materials such as cement grouts or concrete containing quick-setting cements and to perform tests at high temperatures. The development of the new calorimeter consists first of optimizing the dimensions and the geometry of the device. To achieve this, a numerical model is used and tested through a series of experiments. The device is validated through calibration as well as repeatability and reproducibility tests. A potential application of the new calorimeter is then presented focusing primarily on comparing at different scales, i.e., on concrete and on Concrete Equivalent Mortar, the hydration kinetics and the apparent activation energy.