Search

Dense corundum-mullite brick for blast furnace ceramic pad was prepared using white fused corundum and tabular corundum as aggregates, andalusite fine powder, sillimanite fine powder, zircon sand powder and Guangxi soil as the matrix, and phosphate as the binder, introducing different amounts of α-alumina micropowder, tabular corundum fine powder and fused corundum powder. The properties of the prepared brick were studied. The results show that, the brick with 10 mass % of tabular corundum fine powder fired at 1 560 ℃ for 3 h in a tunnel kiln has the bulk density of 3.08 g · cm-3, the apparent porosity of 13.2%, the cold compressive strength of 178 MPa, the molten iron corrosion rate of 0.6%, the slag corrosion rate of 6.4%, the alkali resistance strength decreasing rate of 7.5%, and the thermal shock resistance of 32 cycles, which is both dense and of good thermal shock resistance. The slag resistance simulation test was performed, which proved that the prepared corundum-mullite brick is better than those currently supplied in the market. [ABSTRACT FROM AUTHOR]

The effects of nano-SiO2 and superabsorbent polymer on the hydration process of early-age cement paste are investigated through the physically bound water evolution test by means of the low-field nuclear magnetic resonance technology. The test results show that the hydration process can be characterized by four-stage patterns based on the zero points of the second-order differential hydration curve, i.e., the initial, accelerated, decelerated, and steady periods. The beginning time of each stage is postponed and the hydration duration is prolonged with an increasing water to cement ratio. The beginning time of each stage and the hydration duration are shortened with an increasing content of nano-SiO2. And the beginning time of each stage and the hydration duration are prolonged with an increasing content of superabsorbent polymer. Based on the test data and the Avrami–Erofeev model, a modified hydration model taking the influence of nano-SiO2 and SAP into account is proposed, and the predicted results are consistent with the test results. [ABSTRACT FROM AUTHOR]

In this paper, by testing the evolution of the physically bound water using the low-field nuclear magnetic resonance (LF-NMR) technology, the hydration process of cement paste with nano-CaCO3 (NC) and superabsorbent polymer (SAP) at early age is investigated. Results indicate that the hydration process can be divided into four periods according to the zero points of the second-order differential hydration curve: initial period, acceleration period, deceleration period, and steady period. Firstly, with the increase in the water to cement ratio, the starting time of the hydration period is delayed, and the duration becomes longer. Secondly, the addition of NC leads to the speedy arrival of each period and shortens the duration of each period in the hydration process, and the optimal NC content is 1.5%. Thirdly, with the increase in SAP content, the starting time of the hydration period is delayed and the duration becomes longer. Finally, based on the experimental results and the existing hydration model, the modified hydration model considering the content of NC and SAP is proposed. [ABSTRACT FROM AUTHOR]