Application of infrared imaging to fresh concrete: monitoring internal vibration
The primary purpose of this research was to evaluate the use of infrared imaging cameras as a quality control tool to be used during concrete consolidation via internal vibration. The goal of this research was to monitor the surface of concrete slabs during and after consolidation by internal vibration. This was done in insulated slab forms to limit lateral heat loss and mimic larger sections of concrete. Concrete and concrete-making materials were also vibrated in a calorimeter and the amount of heat transferred from the internal vibrator to the surrounding material was quantified. The heat generation rate of internal vibrators was also investigated along with the effect of surface finish on the apparent temperature of fresh and hardened concrete. Internal vibrators were characterized by measuring frequency, acceleration, a-c current and power consumption, and vibrator head temperature while operating in different concretes, mortars, and with the vibrator head under varying degrees of mechanical restraint. This technology was tested under field conditions during site visits to precast concrete plants. Based on the data collected over the course of this research, and the field observations made, recommendations are given for using this technology as a qualitative tool to locate vibrator insertion points in a mass of concrete following the vibration process.
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List of Tables
Discussion of Laboratory Results
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a-c current accelerometer ACI Committee 309 amplitude angle of incidence apparent temperature approximately average calibration calorimeter cell calorimetric tests cement paste cement ratio change per mass Chapter clamp coarse aggregate computed concrete mixture concrete slab concrete Vibrator consolidation convection cylinder mold data acquisition system decrease density determined diameter electrical energy emissivity Equation flexible shaft formwork Forssblad fresh concrete hardened concrete heat transfer Holst infrared imaging system insulating jacket internal energy change internal vibrator Kosmatka and Panarese Lautz mass of water minutes mixing mixing test monitor mortar operating in air Portland cement radiation radius of action rate of surface results for experiment Schematic showing shown in Figure specific heat Styrofoam substance surface temperature change T2 one degree Table tachometer temperature data temperature difference temperature measurements thermal conductivity thermocouple Time-temperature results typically universal motor vibrator frequency vibrator head temperature vibrator insertion vibrator operation vibrator tip viewing angle water slurry water-cement ratio