Sinan T. Erdoğan

Comprehensive Evaluation of AIMS Texture, Angularity, and Dimension Measurements

Aggregates are the most widely used construction materials in the world in structures built from both asphaltic and portland cement concrete composites. The performance of these composites is affected by aggregate shape characteristics (e.g., angularity, texture, and dimensions). The aggregate imaging system (AIMS) is a computer automated system that was developed to measure aggregate shape characteristics using digital camera images of aggregates. This paper addresses four issues concerning AIMS measurements: (1) enhanced ways of handling and classifying the large data sets typically generated; (2) enhanced automation in processing fine aggregate images that appear to contain touching particles; (3) an improved consideration of measurement variability or repeatability between different operators, different AIMS units, and for aggregate placement and orientation; and (4) comparison of AIMS dimensional measurements with true three-dimensional measurements using X-ray computed tomography on a large coarse a...

Properties of Ground Perlite Geopolymer Mortars

Perlite is a volcanic aluminosilicate abundant in several countries that are major producers of portland cement. The amorphous nature and silica-to-alumina ratio of ground perlite indicate that it can be activated with alkaline solutions. This study presents the strength development of mixtures containing only ground perlite as their powder binder, activated with sodium hydroxide and/or sodium silicate solutions, at room temperature or using oven curing. The structure of the formed geopolymers is investigated using X-ray diffraction, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The thermal stability and acid resistance of the mixtures are evaluated. Sodium silicate-activated mixtures slowly reach moderate strengths at room temperature but sodium hydroxide-activated ones do not develop strength regardless of activator concentration. Both activators produce geopolymers with high strengths with 100°C dry oven curing. Sodium silicate-activated specimens are more resistant to high temperatures but less resistant to a sulfuric acid solution than are sodium hydroxide solution-activated specimens. Being natural and having a more consistent chemical composition compared with most artificial pozzolans make perlite an attractive geopolymer raw material.

Simple Estimation of the Surface Area of Irregular 3D Particles

AbstractShape-related properties of irregular particles are of interest in many fields. The volume and dimensions of rocks, such as coarse and larger fine concrete aggregates, can be physically measured rather easily. However, the surface area is difficult to measure physically, if at all possible. A combination of computed tomography and spherical harmonic analysis can be used to calculate the surface areas of micrometer-sized to centimeter-sized particles. This paper compares the success of several approaches that use easy-to-measure properties, specifically the orthogonal length, width, and thickness of a particle and its volume to estimate its surface area. A training set of 3,359 particles varying widely in size and shape is used to develop regression equations between various shape parameters. These equations are then used to estimate surface areas of cement and aggregate particles in three different validation sets. Improvements are offered to some existing surface area estimation methods. Finally,...

Prediction of Elastic Moduli Development of Cement Mortars Using Early-age Measurements

This paper presents an investigation of the time development of dynamic and static elastic moduli of eight mortars made using CEM I cements with contrasting properties. Mixing and the preparation of dynamic testing prism specimens conformed to EN 196-1. A non-standard specimen and bending test setup was devised for measuring the development of static Youngs modulus. It was determined that dynamic Youngs moduli determined using an ultrasonic pulse velocity test are often but not always greater than those determined using a resonant frequency test. The ratio of static Youngs modulus to dynamic Youngs modulus for a particular cement mortar increased nearly linearly with increasing static modulus after age 3 days, and this increase can be predicted using the measured 3-day static modulus. Also, methods for predicting the increase of static and dynamic modulus and decrease of Poissons ratio of mortars, from age 3 to 56 days, using measured 3-day elastic moduli are presented. Predicted 56-day values of static Youngs modulus, dynamic modulus, the ratio of these, and Poissons ratio for the eight different mortars were within 5 % of the measured values. The observed relations between different elastic properties may be useful for verification of prediction models.