Influence Of High Rock Wall Temperature On Mechanical Properties Of Lining Concrete In Tunnel

It is an international problem that high rock wall temperature will endanger thelining concrete, and a number of countries are focusing on it. However, the impact ofdifferent admixtures on mechanical properties of lining concrete has not yet formed asystem. This paper systematically studied the pattern of tunnel lining concretecompressive strength of slag, fly ash, slag and fly ash composite using in high rockwall temperature, also studied the impact of lining concrete compressive strength afterthe curing agent curing in high rock wall temperature.Curing system of lining concrete in high rock wall temperature is simulated bytwo stages, that is to say the concrete with mold cured in high temperature for1day,and then put the concrete into the standard curing room. High curing temperature is50℃、60℃、80℃, and relative humidity is50%、75%、100%.The effect of differentadmixture on concrete in high rock wall temperature is studied, combined with XRDand SEM. The results showed that:3days compressive strength of concrete increaseswith temperature rising, compressive strength of concrete after28days decreases withtemperature rising. The hydration rate of binder speeds up when temperatureincreased, so the hydration products generate too quick to evenly spread, mutualoverlap gets worse, causing the decreasing of concrete compressive strength after28days. When temperature is below60℃, the compressive strength of concrete withslag is higher than the one adding fly-ash; when temperature gets to80℃,thecompressive strength of concrete with fly-ash is higher than the slag ones. This is because activity of fly-ash significantly increases with temperature increment.In high temperature curing stage, when the temperature is80℃,compressivestrength of concrete improves with maintain humidity increasing. The60-daycompressive strength increase of concrete with slag is largest.In high temperature curing stage, when the temperature is80℃,relative humidityis50%,the influence of conservation agent to concrete is studied, the results show that:silicate conservation agent can increase the compressive strength of concretesignificantly compared to concrete without conservation agent; wax emulsionconservation agent can increase the compressive strength of concrete slightlycompared to concrete without conservation agent.The suggestion is adding fly ash to concrete in high rock wall temperature,notslag. In simulated curing system, increasing the dosage of cement in concrete canimprove the compressive strength of the lining concrete,strength grade needs toimprove when designing mix proportion.