Abstract: High temperature damage on roadway had been particularly outstanding with the increment of mining depth. By mixing ceramsite, hydrophobic vitrified beads, fly ash and changing the dosage of sand in ordinary shotcrete, we designed orthogonal experiment to researching the variations of compressive strength, tensile strength, flexural strength and heat conductivity coefficient. Experimental results show that hydrophobic vitrified bead is a dominant factor that affects the strengths and heat conductivity coefficient of concrete, hence we recommend the optimum dosage of hydrophobic vitrified beads as 100%. Ceramsite is also a major factor affecting the flexural strength, with a contribution rate up to 60.61% and therefore we conclude the optimum ceramsite dosage to be 20%. With the increasing of fly ash content, heat conductivity coefficient firstly reduced and subsequently increased; while the strength of shotcrete is on the contrary. Finally, with the decline of sand dosage, heat conductivity coefficient had been reducing all the time whereas flexural strength had been increasing, and compressive and tensile strength firstly increased and then reduced; therefore the optimum sand dosage is 580 kg/m³.

Key words: shotcrete, heat preservation and heat insulation, orthogonal test, ceramsite, vitrified beads, fly ash, heat conductivity coefficient, strength