In this study, a series of three-point bending tests were carried out with notched beam structures made of polyvinyl alcohol (PVA) fiber-reinforced ultra-high-performance concrete (UHPC) to study the effect of volume fractions of PVA fibers on the fracture characteristics of the UHPC-PVAs. Furthermore, in order to meet the increasing demand for time- and cost-saving design methods related to research and design experimentation for the UHPC structures, a relevant hybrid finite element and extended bond-based peridynamic numerical modeling approach is proposed to numerically analyze the fracture behaviors of the UHPC-PVA structures in 3D. In the proposed method, the random distribution of the fibers is considered according to their corresponding volume fractions. The predicted peak values of the applied force agree well with the experimental results, which validates the effectiveness and accuracy of the present method. Both the experimental and numerical results indicate that, increasing the PVA fiber volume fraction, the strength of the produced UHPC-PVAs will increase approximately linearly.

In this paper, hydroxypropyl methylcellulose (HPMC) is used as a new additive for porous vegetarian concrete (PVC) to improve its void structure and strength. The effect of the HPMC on the fluidity of the mortar was first investigated by a viscosity test. Then the cement hydration process was determined for analyzing the effect of the HPMC on the strength and durability of the hardened PVC. Subsequently, experiments to investigate the mass transport and compressive strength characteristics, as well as the vegetarian properties, of the concrete were carried out. The results show that the bonding forces between the recycled aggregates and packing layer are elevated by viscosity improvement. The viscocity and flowability are significantly related to the dosage of HPMC from 0.0‰ to 0.3‰. The harden time is also delayed while the content of HPMC increases.The segregation phenomenon caused by the recycled aggregate powder in porous concrete could also be relieved by adding HPMC. The durability of PVC in the wetting–drying cyclic test is significantly improved by incorporating HPMC. The results of the vegetarian test also prove that, with HPMC mixing, sufficient space would be created in porous concrete, which is more suitable for plant growth due to a large number of existing pore channels.

UHPC is the most potential matirals in deep underground constructions due to its remarkable strength and durability. This paper investigated the effects of different water-cement ratios, active material dosages, polymer admixtures, curing conditions and polymer fiber materials on the physical and mechanical properties of ultra-high performance concrete (UHPC). It was found that the optimal binder-aggregate ratio of UHPC was 45:55. UHPC mixed with silica fume exhibited higher strength and volume shrinkage rate than that mixed with blast furnace slag and fly ash with polycarboxylate superplasticizer adding. The addition of superabsorbent polymers shrinkage reducing agent(CS) could improve UHPC fluidity to a certain extent, but when the dosage exceeded 3\%, the surface displayed certain spalling, with strength reduced from 170.1 to 134.1MPa. Hence, CS dosage is recommended to be controlled within 3\%. Curing at 90$^\circ$C can not only shorten the curing time, but also improve the strength. Two types of fibers was investigated in this paper. The result showed that addition of polyvinyl alcohol fiber (PVA) was optimal for the performance optimization of UHPC than alkali resistant glass fibre(AR-GF). Additionally, the creep performance test showed that the long-term creep strength under multistage loading was about 212MPa, and the long-term creep deformation greatly affected the stability of UHPC structure.