Sleeve grouting compactness has a significant effect on the mechanical properties of rebar connections. However, a detection method for the grouting compactness inside the sleeve is still lacking. Therefore, the aim of this paper is to propose a new acoustic emission (AE) detection technology for horizontal defects and vertical defects in sleeves with different grout compactness. The basic waveform characteristic of the AE signal is analyzed. The results show that the count of acoustic emission signals decreases with the increase of grouting compactness, and the reduction rate of vertical defects is larger than that of horizontal defects. The acoustic emission waveform is further processed through wavelet packet decomposition. It is found that with the increase of grouting compactness, the composition of approximately 125–187.5 kHz in the signal is accelerated to approximately 62.5–125 kHz. The grouting compactness index is constructed by wavelet packet energy ratio. With the increase of grouting compactness, the compactness index decreases exponentially, indicating that the presence of defects can greatly reduce the attenuation of elastic wave energy. The compactness index is highly consistent with the size of defects and has little relationship with the distribution of grout materials. Experiments show that the proposed method is effective when grout defects reach a certain degree and provides a new method for sleeve grouting compactness detection.

This study is aimed at the problem of limestone deterioration and damage caused by the combination of acid rain and the dry-wet cycle in Guilin. Samples of limestone were taken to study the influence of acidic dry-wet cycles on limestone deterioration and damage. This was accomplished by performing nuclear magnetic resonance (NMR) measurements and inductively coupled plasma atomic emission spectrometer measurements on the limestone samples. The study found that with an increase in the number of cycles, the curve of the rock continuously shifts to the right, but the range of movement still decreases with pH increasing values. The spectrum area, rock porosity, porosity deterioration, mass loss rate, and water absorption rate all increase with an increase in the number of cycles, but the growth rate continues to decrease, and the increase is negatively correlated with pH. After the dry-wet cycles, the mass concentration of each element in the beaker is Ca, Mg, and Fe in order from high to low, and the mass concentration of each main element in the reaction solution increases with the increase in the number of acidic dry-wet cycles.