大粒径再生粗骨料混凝土墩基础竖向受压性能

为了实现建筑垃圾资源化高效利用，将大粒径再生粗骨料应用于混凝土基础中，考虑墩基础直径和不同施工方式两方面的因素，制作两个不同尺寸（尺寸分别为800 mm×2 500 mm、1 000 mm×2 500 mm）的大粒径（再生粗骨料粒径为 40~80 mm）再生粗骨料混凝土预制墩基础和两个普通混凝土现浇墩基础，通过墩基础原位轴压静载试验，对大粒径再生粗骨料预制墩基础在砂土地基中的荷载-沉降曲线特性、墩底地基土压力分布、破坏模式和竖向承载力等进行分析。在此基础上，分别制作了3个尺寸为 250 mm× 500 mm（圆截面直径×试件高度）再生混凝土墩柱和3个相同尺寸的普通混凝土墩柱，通过墩柱轴压试验对墩柱破坏过程进行研究。研究结果表明：浇筑大粒径再生粗骨料混凝土墩柱时加入钢丝网片，能够阻止大粒径再生粗骨料下沉，使得再生粗骨料均匀分布，从而保证再生混凝土墩柱的浇筑质量；再生混凝土墩柱受压发生破坏时，大粒径再生粗骨料发生断裂破坏，再生粗骨料与普通混凝土的界面黏结性能良好。再生混凝土墩柱的轴压承载力较普通混凝土墩柱的降低15%。在砂土地基中，大直径再生粗骨料混凝土预制墩基础与普通混凝土现浇墩基础在达到竖向极限荷载之前均未发生墩身破坏，表明这两种墩基础可用于砂土地基中。

Study on vertical compression behavior of precast pier foundation filled with large-size recycled coarse aggregate concrete

Using large-size recycled coarse aggregate concrete (LRCAC) in pier foundation can effectively improve the efficiency of utilization of construction waste. Considering the factors of pier foundation diameter and different construction methods, two precast pier foundations filled with LRCAC (with particle size of recycled coarse aggregate of 40-80 mm)and two ordinary concrete cast-in-place pier foundations (with dimensions of 800 mm×2500 mm and 1000 mm×2500 mm, respectively) were made. Based on the in-situ axial compression static loading test of pier foundation, the characteristics of load-settlement curves, soil pressure distribution, failure modes and vertical bearing capacity of the two types pier foundations were analyzed. Three pier column models filled with LRCAC and three ordinary concrete pier column models (with dimension of 250×500) were designed respectively, and the failure process of pier body was studied by axial compression test. The results show that adding ‘steel wire mesh’ in the pouring of pier columns can prevent the sinking of large-size recycled coarse aggregate, and make the recycled coarse aggregate evenly distribute in the test piece, so as to ensure the pouring quality of pier columns. When the pier column failes under compression, the recycled coarse aggregate appears fracture failure, and the interface between the recycled coarse aggregate and the new concrete matrix is well bonded. The bearing capacity of pier column filled with LRCAC is 15% lower than that of the ordinary concrete pier column. In the sandy ground, there is no damage to the pier body before the precast pier foundation filled with LRCAC and the ordinary concrete cast-in-place pier foundation reach the vertical ultimate bearing capacity, which indicates that the two pier foundations can be applied in the sandy ground.