Experimental Study On The Performance Of Lightweight Aggregate Shotcrete

Artificial lightweight aggregate has the characteristics of high specific strength,good impermeability and high durability due to the special nature of its material.Due to the low weight of light aggregate,it can also reduce the rebound caused during the spraying process.Applying lightweight aggregate to shotcrete provides a new solution to give full play to the characteristics of lightweight aggregate.In this paper,based on the actual repair and reinforcement of the Mawei slope tunnel in G210 National Highway in Duyun,Guizhou,which was in disrepair and serious water leakage,the application research of lightweight aggregate in shotcrete was carried out.The thesis systematically studied the mechanical properties of light aggregate(shale ceramsite)shotcrete,the influence of concrete components on the performance;the permeability of concrete and the rebound theory of shotcrete,designed for the mix ratio of light aggregate shotcrete It provides a theoretical basis for practical application,further explains and enriches the springback theory of shotcrete,and provides a theoretical support for shotcrete to reduce springback.The thesis adopts the design method of orthogonal experiment in the design of the mix ratio of light aggregate shotcrete.Through the strength test of the concrete,the unit water consumption,water-binder ratio,fly ash substitution rate and silica fume substitution rate for light aggregate are studied.The influences of the compressive strength,splitting tensile strength and bonding strength of shotcrete were analyzed.The influence rules and weights of the material composition and replacement rate in shotcrete on the mechanical properties of light aggregate shotcrete were analyzed.The mix ratio design provides a theoretical basis.In this paper,the permeability resistance test of lightweight aggregate shotcrete was carried out.The influence of single and compound mineral admixtures on permeability was studied.An electrochemical workstation was used to establish the relationship between electrochemical parameters and concrete permeability.contact.The thesis explains the general theory of springback of shotcrete from the perspective of kinematics,and derives the influencing factors of springback of shotcrete.The self-made test equipment was used to study the influence of different aggregate densities on the contact stress,and the rebound influencing factors of different aggregate densities were calculated.The principle that the rebound of light aggregate shotcrete was lower than that of ordinary shotcrete was theoretically explained.The test results show that the basic mechanical properties of lightweight aggregate shotcrete can meet the requirements of ordinary shotcrete of the same grade,and the splitting tensile strength and bonding strength of light aggregate are slightly higher than ordinary shotcrete.Within a certain range,reducing the water-binder ratio and adding mineral admixtures can improve the mechanical properties of lightweight aggregate shotcrete.Based on the orthogonal test,the influence weight and the best mix ratio of each factor are obtained.The resistance to chloride ion penetration of light aggregate is about 40% higher than that of ordinary shotcrete.The addition of fly ash and silica fume can improve the resistance to chloride ion penetration of lightweight aggregate sprayed concrete,and within a certain range,the improvement effect is more obvious as the substitution rate increases,and the compounding effect is the best.The test results of the electrochemical test method are consistent with the electrical flux and RCM results.In the electrochemical impedance spectroscopy,RS and Rct and the penetration depth of the chloride ion show a Boltzmann curve.The electrochemical parameters can be used to characterize the resistance to chloride ion penetration.Combined with the process of aggregate kinematics,a general theory affecting springback is obtained.The resilience impact factor of ordinary concrete is mainly related to static and dynamic contact stress.The resilience impact factors of aggregates with different densities are dynamic and static contact stress,density,initial velocity and elastic modulus.By testing the static contact stress and elastic modulus of two different densities of aggregates,it is concluded that the impact factor of light aggregate spraying and concrete rebound is smaller than that of ordinary sprayed concrete,which is consistent with the conclusions drawn from practice and verifies the correctness of the theory Sex.