| Rebound is a common nondestructive test method, mainly used in testing masonry concrete strength, detection the label of brick and mortar strength. Its main characteristic is nondestructive, easy and convenient to use, widely applied and low cost. Rebound Method is a method to estimate the compressive strength of concrete and bricks by using a spring-driven hammer to hit the surface of materials and measure the rebound value (the ratio of the initial length of the rebound from the spring) as a strength parameter.Since the beginning of reform and opening up, as rebound method is more and more widely applied, national standards and local standards have been revised in testing strength of concrete, label of bricks and strength of mortar by means of rebound. As the environmental friendly polices especially about energy-saving have been put in place and the field of non sintered arable bricks develops continuously, solid concrete bricks gradually have been applied to walls of various buildings.But the rebound method standard about the non sintered bricks is till blank.In order to a better development of non sintered bricks, it is necessary to establish a unified formula on measuring solid concrete bricks by means of rebound. Hunan University research the rebound method to test existing compressive strength of masonry brick building block in2010.and written in national regulations, but whether it is suitable For the solid concrete brick, no research precedent at home and abroad, research the reboundmethodpresumed common solidconcretebrick compressiv e strength, fill the gaps at home and abroad for the promotion and application of rebound method in block. This paper is one of the presumption ofcompressive strength of masonry series of achievements.Through the relevant tests and data analysis, this paper has established the for-mula which applies to solid concrete bricks using the principles of statistics. What have been done in this paper are as follows.(1) This paper covers the developing process and prospect of non sintered bricks home and abroad, the characteristics of solid concrete bricks, the principle of determination of solid concrete bricks’ compressive strength and the factors that may affect the rebound data.(2) Through the compared experiments of6standard solid concrete bricks in Hunan University, we have studied the influence mechanism of rebound values of different vertical pressure and distinguished test methods. (3) By testing specimen’s compressive strength of24standard solid concrete bricks in Hunan University.20data of R-f are obtained from the Rebound Test and the compressive test by ZC4brick rebound hammer. The data of R-f obtained from the ZC4brick rebound hammer is fitted with the Least Square Method in the style of power function.(4) By testing specimen’s compressive strength of3test walls in Sichuan Academy of Building Research,3test walls in Jiangsu Academy of Building Research,7test walls in Nanchong Quality Supervision Department, Analysis the curve fitting rebound strength curve precision for confirmatory(5)246data of R-f are obtained from the Rebound Test and the compressive test by ZC4brick rebound hammer. The data were divided into39groups. The average value of rebound value and compressive strength in each group were calculated. The data of R-f obtained from the ZC4brick rebound hammer is fitted with the Least Square Method in the style of power function. The regression analysis was also conducted. Consequently, the ZC4concrete rebound hammer strength calculation formula in the style of power function for the concrete bricks in the existing masonry is obtained.Confirmatory experimental results demonstrated that the degree of accuracy of the rebound strength curve for concrete common brick in existing masonry established in this thesis is high. As a result, it can provide some essential bases for revision of industry standard "The method of evaluating the non agglomeration brick strength grading by rebound method"... |
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