Piti Sukontasukkul

Properties of Steel Fiber Reinforced Geopolymer

In this study, the mechanical properties of steel fibre reinforced geopolymer (SFRG) are investigated. The geopolymer is consisted of fly ash, silica fume and activator solution, sodium silicate and sodium hydroxide. Five mix proportions of fly ash and silica fume are varied to study the effect of fly ash/silica fume ratios (FA/SF). This experimental series focus mainly on flexural strength and flexural toughness performance of SFRG. Hooked-ends steel fibers are used at 0.5% and 1% by volume fractions. The experiment is carried out based on ASTM C1609 (beam specimens) for flexural performance. The results showed that fibre can significantly enhance the both flexural strength and toughness of geopolymer. The enhancement also increases with the increasing fibre volume fraction.

Improving thermal properties of exterior plastering mortars with phase change materials with different melting temperatures: paraffin and polyethylene glycol

ABSTRACT In this study, the effect of phase change material on properties of plaster mortar was investigated. Two types of phase change materials (PCM) were used: Paraffin 6035 and Polyethylene Glycol 1450. The PCM were mixed with plastering mortar at 2.5–15% by volume fractions. Experimental series required by TIS were carried out on both ordinary and PCM mortars including flow test, water retention, pull-off test, compressive strength and thermal properties (laboratory and field tests). Results indicated that fresh plastering mortar reacted with the PCM differently depending on the PCM type. The paraffin had a tendency to lower the flow and water retention while the PEG tended to increase them. In hardened stage, both the compressive and pull-off strengths were found to increase at a low PCM content and then decrease when PCM content was higher than 5.0%. For thermal properties, the PCM plastering walls displayed better performance than ordinary plastering wall as seen by the lower peak temperatures and the extended time to reach peak temperature. This research also showed the success of PCM’s application in hot and humid weather where PCM mortar together with hollow concrete blocks could help storing heat at the wall and maintaining the temperature inside the cubicles.

Electrical Resistivity of Cement-Based Sensors under a Sustained Load

This research was to study the influence of a sustained load on the electrical resistivity of a cement-based sensor. The cement-based sensor in this study was made of cement paste having water to cement ratio of 0.4 with the addition of graphite powder at 2% and 4% by weight of cement and carbon fibers at 2% and 4% by volume. The sustained load was applied on the cement-based-sensor using a sustain machine to control a compressive force continually at 30% of its ultimate compressive strength for a period of 30 days. The test results showed that the sustained load induced a creep strain on the cement-based-sensor. The graphite incorporated cement-based sensor showed higher creep strain than the plain cement-based sensor while the carbon fiber cement-based sensor showed lesser. In addition, it was shown that the creep strains affect the electrical resistivity of the cement-based sensors.

Application of Cement-Based Sensor on Compressive Strain Monitoring in Concrete Members

The aim of this research was to implement cement-based sensors in monitoring the change of strain in concrete structures in particular where a compression applies. The experiment was conducted in a laboratory by embedding a cement-based sensor in a 150x150x150 mm normal strength concrete cube. When the sensor-installed concrete cube was loaded, the relation between the fractional change in resistivity (FCR) and strain of the sensors was evaluated. In this study, all cement-based sensors were made of cement paste containing carbon fiber at 2% by volume fraction. They were then varied with the addition of graphite powder at 4% and silica fume at 15% by weight of cement. Thus, there were total four mix proportions. From the experimental results, all sensors provided a good corelation between the FCR and compressive strain. Among them, the carbon fiber plus graphite powder (no silica fume) cement-based sensor yielded the most excellent piezoresistive response.