Concrete for high temperatures

Journal of Materials Processing Technology

2003

The contemporary 120 W high power diode laser (HPDL) has been successfully used for the first time to fire an enamel glaze onto the ordinary Portland cement (OPC) surface of concrete. The enamel glazes were generated with laser power densities as low as 1 kW/cm 2 and at speeds of up to 780 mm/min, yielding a possible maximum coverage rate of 0.34 m 2 /h. The enamel glazes were typically 750 µm in thickness and displayed no discernible microcracks or porosities. Owing to the wettability characteristics of the OPC, it proved necessary to laser treat the OPC surface prior to firing the enamel. Mechanical testing of the HPDL fired enamel glazes revealed that the average rupture strength was 2.8 J, whilst the rupture strength of the untreated OPC surface was some 4.3 J. The average bond strength of the glaze was recorded as 2.4 MPa as opposed to 6.3 MPa for the untreated OPC. The HPDL fired enamel glazes exhibited exceptional wear and corrosion resistance, wearing by only 3.3 mg/cm 2 after 8 h and showing no discernible morphological or microstructural changes when exposed to acid, alkali and detergent. In contrast, the untreated OPC surface was attacked almost immediately by the reagents used and was worn by 78 mg/cm 2 after 8 h. In addition, the HPDL fired enamel glaze afforded the concrete bulk complete resistance to water absorption. The findings of life assessment testing revealed that the HPDL fired enamel glaze effected an increase in the wear life of the concrete by 4.5 to 52.7 times over an untreated OPC surface, depending on the corrosive environment.

Section: Operating Windowmentioning

confidence: 72%

The enamelling of concrete for improved performance characteristics by means of high power diode laser interaction

Journal of Materials Processing Technology

2003

“…7. The strength of the crushed ceramic tile mix in terms of increasing temperature is determined primarily by the waterglass, since the strength of the individual oxide compounds which comprise the ceramic tiles vary little or not at all at relatively low temperatures (<500 0 C) [29]. As is evident from Fig.…”

Section: The Role Of Sodium-silicate-solutionmentioning

confidence: 95%

Single-stage sealing of ceramic tiles by means of high-power diode laser radiation

Journal of Laser Applications

Lü

Edwards

et al. 2001

An investigation has been carried out using a 60 W high power diode laser (HPDL) to determine the feasibility of sealing the void between adjoining ceramic tiles with a specially developed grout material. A single-stage process has subsequently been devised using a new grout material which consists of two distinct components: a crushed ceramic tile mix substrate and a glazed enamel surface; the crushed ceramic tile mix provides a tough, inexpensive bulk substrate, whilst the enamel provides an impervious surface glaze. HPDL processing has resulted in crack and porosity free seals produced in normal atmospheric conditions. The single-stage grout is simple to formulate and easy to apply. Tiles were successfully sealed with power densities as low as 750 W/cm 2 and at rates of up to 420 mm/min. Bonding of the enamel to the crushed ceramic tile mix was identified as being primarily due to van der Waals forces and, on a very small scale, some of the crushed ceramic tile mix material dissolving into the glaze.

“…Petzold et al [39] have determined from differential thermal analysis (DTA) results that up to approximately 420 0 C, OPC remains relatively stable. Notwithstanding this, some dehydration does occur and water is also lost from the pores of the cement.…”

Section: Effects Of High Power Diode Laser Radiation On Ordinary Portmentioning

confidence: 99%

The influence of a high power diode laser (HPDL) generated glaze on the wetting characteristics and the subsequent HPDL enamelling of ordinary Portland cement

Surface and Coatings Technology

2001

High power diode laser (HPDL) surface glazing of the ordinary Portland cement (OPC) surface of concrete was found to effect significant changes in the wettability characteristics of the OPC. This behaviour was identified as being primarily due to: (i) the polar component of the OPC surface energy increasing after HPDL glazing from 3.46 to 15.56 mJm -2 , (ii) the surface roughness of the OPC decreasing from an Ra value of 21.91 to 2.88 µm after HPDL glazing and (iii) the relative surface O 2 content of the OPC increasing by 4.5at% after HPDL glazing. HPDL glazing was consequently identified as occasioning a decrease in the enamel contact angle from an initial value of 109 0 to 31 0 , thus allowing the vitreous enamel to wet the OPC surface.