Application Of Ultrasonic Testing Technology For Strength Of Autoclaved Aerated Concrete Block

Autoclaved aerated concrete block is a new type of wall material,which is widely used in construction engineering.Its compressive strength directly relates to the safety of buildings.However,the current detection methods have relatively backwards,and unable to quickly and accurately detect the compressive strength,which affects the progress of the project and may also adversely affects on the safety performance of the building.Therefore,there is an urgent need for the detection method that can be effective and fast to make up for these defects.Ultrasonic method is a method for judging the internal properties of solids by ultrasonic wave speed,which has fast and accurate characteristics.The ultrasonic method is applied to the compressive strength test of autoclaved aerated concrete,that is,the performance of the corresponding relationship between the ultrasonic wave speed and the compressive strength of the solid structure is used to mathematically fit the ultrasonic wave speed and the compressive strength of the autoclaved aerated concrete block.The corresponding mathematical formula is obtained to improve the detection efficiency while ensuring the accuracy of the detection results.The uncertainty caused by various factors in ultrasonic wave velocity experiment and compressive strength experiment was evaluated,which showed that the experimental state was stable,and the single measurement was used as the measurement result in each experiment.The uncertainty in the experiment was low,indicating that the deviation in the experiment is low.The main source of the uncertainty was the repeated experiment.In the course of the experiment,we should strengthen the control of the repeated experiment and reduce the uncertainty.The effects of stacking time,moisture content and dry-wet cycles on ultrasonic wave velocity and compressive strength were studied.The relationship between ultrasonic wave velocity and compressive strength was analyzed.The microstructure,crystalline phase and pore size distribution of autoclaved aerated concrete block detected by ultrasonic are analyzed.The results show that the hole of autoclaved aerated concrete block was not changed by ultrasonic method,and the autoclaved aerated concrete block could be tested by ultrasonic method.The compressive strength and ultrasonic velocity increase with the increase of stacking time from 8h to 1d,and the compressive strength and ultrasonic velocity decrease with the increase of stacking time after 1d.With the increase of water content,ultrasonic wave velocity and compressive strength decreased rapidly,and tended to be stable after the water content reaches10%-15%.The compressive strength and ultrasonic wave velocity of autoclaved aerated concrete block decreased gradually with the increase of dry-wet cycles.After 15 cycles,the compressive strength and ultrasonic wave velocity of autoclaved aerated concrete block tended to be stable.With the increase of the size of autoclaved aerated concrete block,the ultrasonic wave velocity kept stable at first and then decreases gradually.When the thickness of autoclaved aerated concrete block was more than 300mm,the ultrasonic wave velocity decreased rapidly.By collecting a large number of data,the mathematical formula between ultrasonic wave velocity and compressive strength was established and verified.Finally,the mathematical formula of ultrasonic testing for compressive strength of autoclaved aerated concrete block was expressed by the Eq.y=-1.9x~3+10.3x~2-14.9x+8.4,where x value range is 1000m/s-2700m/s.The applicable conditions are as follows:the stacking time of 28d-90d,the moisture content of about 10%,the dry-wet cycle times of 0 times.