Investigation Of Reducing-noise Materials Applied Into Highway Tunnel

According to the generation mechanism and control methods of traffic noise, this dissertation seeks to put forward the effective ways for reducing traffic noise in highway tunnel. By the theoretical investigation on the room-acoustics theory, a prediction model, the methods of determination of the parameters and two comparative measures of reducing noise are given to indicate the quieter concrete pavement and the sound absorption wall in the tunnel respectively. Thus, the objective of this study is to prepare the quieter concrete and porous absorption material applied into tunnel.The intercross analysis method and Bond-Test of the bond characteristic of exposed aggregate were conducted to design the strength of quieter concrete. The former is to determine the basic proportions such as W/C, Sp and the dosage of superplasticiser. The latter is to indicate the dosage of silica fume and the final designed strength of cement concrete pavement which avoids the near-surface exposed aggregate dropping from the concrete surface in service. As showed from the relative curve between the maximum pull force (Fmax) and the compressive strength (fc), an evident phenomenon can be observed that the development gradient of the Fmax-fc curve is properly clear compared with the Fp - fc curve. Moreover, a critical point of Fmax force, 17.31KN, appears at the 70Mpa compressive strength of exposed aggregate concrete. The value of Fmax intends to stabilize after passing that turning point. An objective suggestion from the experimental results can be represented that because the results of the development gradient of the Fmax- fc curve experimentally gives an estimate of the minimum bond between aggregate and matrix, the designed compressive strength of exposed dense concrete applied into the reducing-noise pavement be over 70Mpa to avoid the aggregate dropping from concrete surface. The comparison of interfacial zone according to the microscope images and microhardness values of different situations of exposed aggregate indicated the ITZ of the edge of exposed aggregate near to the atmosphere is obvious weakest than that of rest ones, and the absence of near-surface-depth weakness gradient of expose dense concrete approximately appeared below certain depth for high strength and normal strength concrete respectively. As for the reducing-noise performance of this pavement, the indirect method of testing the sound absorption coefficient is adopted and evaluatesthe reducing-noise performance. The sound absorption coefficient of normal concrete is 0.09in contrast to quieter concrete with 0.16 under 1000Hz.The proportions of sound absorption material were determined by the work ability of fresh foam mortar, strength property and sound absorption performance and systematically investigated by the single factor method. With the increase of gas former content, the flowability takes on the ladder development, and there is a suitable range of gas former dosage (0.3%~0.5%) for the requirement of workability where the pore distribution is well distributed and the workability is excellent. However, the strength development including the compressive and flexible strength is decrease with the increase of gas former content. Under the point of 0.4% gas former, the flexible strength cannot meet the requirement for the flexible strength. Moreover, the sound absorption coefficient of prepared specimens with 0.4% gas former is greater that that of both specimens with 0.3% and 0.5% gas former. When the water/cement is 0.725, the average absorption coefficient is 0.53. The 0.20~0.39mm range of the pore distribution of sound absorption material is available to the absorption performance by calculating the pore ratio and analyzing the results of optical microscope.As showed from the results of the practical testing after the application of reducing-noise materials, the reducing-noise quantity of quieter concrete pavement is 1.7dB~3.8dB and that of the absorption wall is 5.5~7.6dB. Compare with the treated and untreated experimental fields, the chaos time at 1000Hz...