Refractory Concrete | Brief Introduction
High alumina cement finds extensive use in producing refractory concrete, which withstands high temperatures, in combination with heat-resistant aggregates. Notably, when exposed to high temperatures and humidity, high alumina cement concrete experiences a significant reduction in strength.
However, desiccated high alumina cement concrete retains satisfactory residual strength even when subjected to elevated temperatures, undergoing minimal conversion.
Completely dried alumina cement exhibits exceptional resistance to dry heat, making it a renowned refractory material.
Alumina cement concrete demonstrates ceramic bonding instead of hydraulic bonding at extremely high temperatures.
High alumina cementitious refractory concrete commonly utilizes crushed refractory brick as an aggregate. Refractory concrete with crushed refractory brick can withstand temperatures of approximately 1350°C.
Aggregates like sillimanite, carborundum, and dead-burned magnesite enable refractory concrete to endure temperatures up to 1600°C.
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Refractory concrete serves a wide range of purposes, including forming foundations for furnaces, coke ovens, and boiler settings. It also finds application in constructing fire pits, electric furnaces, ordinary furnaces, and ranges. Furthermore, high alumina cement proves valuable in producing refractory mortars.
High alumina cement exhibits a slow-setting characteristic but boasts fast hardening properties.
Incorporating specific proportions of ordinary Portland cement significantly reduces the setting time of high alumina cement.
Various scenarios involve the utilization of a specific blend of high alumina cement and ordinary Portland cement. This blend proves valuable when there is a requirement to address specific challenges, such as halting water inflow or undertaking intertidal construction.
In such cases, the unique properties of high alumina cement, when combined with ordinary Portland cement, offer advantageous characteristics for achieving the desired results.
Additionally, this particular blend is also effective in reducing pumping time for underwater projects, making it an ideal choice in such circumstances.
By carefully selecting and proportioning the high alumina cement and ordinary Portland cement, engineers and construction professionals can optimize the performance and efficiency of their projects in these challenging scenarios.
Fig 2.3
Fig. 2.3 shows the setting time of mixtures of Portland cement and alumina. It can be seen from Fig. 2.3 that when either of the two types of cement constitutes between 20 and 80 percent of the mixture, the flash setting can occur.
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The values shown in the graph are only approximate. When employing such a combination, the actual dosage and resulting setting time need to be determined through trial and practice.