# Effects of Grout Compactness on the Tensile Behavior of Ground Splice Sleeve Connectors
## 1 Introduction  
Precast concrete construction is one of the main structural forms that has been widely adopted in China's construction industry. Compared with cast-in-place construction, the integrity and connection quality of precast concrete construction are critical for the safety and performance of the structure. Among all connection methods, the wet connection using grouted splice sleeve (GSS) is widely employed, which uses non-shrinkage grouting materials as bonding materials to ensure the continuity of load transfer. Sleeves are usually made by casting or machinery processing [1]. Grouting material uses cement as base material. After adding water and mixing with fine aggregate and a dry mix made of concrete admixture and other materials, the grouting material will have good fluidity, early strength, high strength, and minimum inflation [2]. The grout quality of GSS is, in a sense, covered in a black box. The factors affecting the grout quality of beam-reinforcement connecting sleeves are elusive and not always under control. For example, workers may not strictly abide by relevant construction standards, or in another case, grout slurry bleeding occurs during construction. Sleeves may have poor compactness and disengaging ends. These can result in bending failure, and excessive tensile stress at the connectors, presenting a safety risk to the operation of the fabricated buildings. The grout compactness has a certain impact on the mechanical properties of grouted splice sleeve connectors. However, no related research has been reported. To date, most studies focus on the monotonic tensile behavior of grouted splice sleeves in various forms due to factors such as production process, external shapes, and cavity structure [3]. Recently, only fully compact connectors are considered in the calculation of the tensile capacity of grouted splice sleeves. For example, [PERSON] et al. [4] studied two types of grouted sleeves, namely the welded bar sleeve (WBS) and the tapered head sleeve (THS). By fitting the tensile test data of 18 fully compact sleeve connectors (9 WBS and 9 THS), they established a bond-slip model describing the tensile behavior of the reinforcement grout. The predicted tensile capacity of the sleeve connectors was obtained by referring to the tensile capacity of the connector reinforcement. The results showed that the predicted values of the tensile capacity of sleeve connector are within 10% deviation from the experimental results. During the past decade in China, research on grouted splice sleeve technology was mainly concentrated on studying the tensile behaviors of sleeve connectors in view of various factors, such as grout age and rebar types [5], outer shape, and inner cavity structure [6; 7; 8; 9]. With the fast development of precast concrete structure manufacturing and construction technology, the shear-resistant and seismic-resistant performance of GSS has attracted increasing attention in recent years [10; 11; 12; 13; 14; 15]. For instance, [PERSON] and [PERSON] [10] studied three monotonic tests (axial tension and four-point bending with and without axial compression) and two cyclic tests (four-point bending and shear) on precast reinforced concrete column-to-column connections with GSSs. [PERSON] et al. [11] developed a full-scale precast reinforced concrete shear wall (PRCSW) endowed with single-row grout-filled sleeves connection, and conducted seismic experiments and numerical simulation of six-story precast box-modularized structures. Furthermore, the PRCSW specimen resembled the cast-in-place shear wall to study the performance design indices, such as failure modes, inter-story drift angle, ultimate force, ductility, and dissipated hysteretic energy. [PERSON] et al. [12] conducted experiments on precast columns connected by grouted corrugated steel sleeves, and a comparison with reference cast-in-place specimens was made. The results show that the precast specimens have similar hysteretic response and energy dissipation capacity as the reference ones. [PERSON] et al.