The paper deals with the properties and microstructure of Reactive Powder Concrete (RPC), which was developed at Cracow University of Technology. The influence of three different curing conditions: water (W), steam (S) and autoclave (A) and also steel fibres content on selected properties of RPC was analyzed. The composite characterized by w/s ratio equal to 0.20 and silica fume to cement ratio 20%, depending on curing conditions and fibres content, obtained compressive strength was in the range from 200 to 315 MPa, while modulus of elasticity determined during compression was about 50 GPa. During three-point bending test load-deflection curves were registered. Base on aforementioned measurements following parameters were calculated: flexural strength, stress at limit of proportionality (LOP), stress at modulus of rapture (MOR), work of fracture (WF), and toughness indices I₅, I₁₀ and I₂₀. Both amount of steel fibres and curing conditions influence the deflection of RPC during bending.

The old-new concrete interface is the weakest part in the composite structure, and there are a large number of microcracks on the interface. In order to study the mode II fracture performance of the bonding surface of old-new concrete, the effect of planting rebar and basalt fiber is investigated. Nine Z-shaped old-new concrete composite specimens with initial cracks are made. Nine shear fracture load-displacement curves are obtained, and the failure process and interface fracture are discussed. On this basis, the mode II fracture toughness and fracture energy are obtained. The regression equations for fracture toughness and fracture energy are deduced with analysis of variance (ANOVA). The results show that fracture toughness and fracture energy increase with the increase of planting rebar number and basalt fiber content. With the increase of the planting rebar number, mode II fracture toughness and fracture energy increase more significantly. Planting rebar is the major factor for mode II fracture performance.

To promote the application of rubber-cement composites as the main bearing structure and key components in practical engineering under frequent dynamic disturbances, in this work, the split Hopkinson pressure bar (SHPB) cyclic impact tests of rubber-cement composite specimens with four different confine modes were carried out in which the impact load increased sequentially. The relationship between average strain rate, ultimate strain and impact times and the relationship between peak stress, damage energy, ultimate strain and incident energy were analyzed. The results showed that the appropriate confine reinforcement treatment can make rubber-cement composite give full play to its deformation ability when it was completely damaged. Carbon fiber-reinforced polymer (CFRP) sheet and steel cylinder can work together with the rubber-cement composite matrix to resist impact load, which effectively improves the structural strength, damage fracture energy, and cyclic impact resistance of the rubber-cement composite. Finally, based on the effect difference of confine modes, the simplified plane force models of rubber-cement composite specimens with four different confine modes were established, which clearly revealed the completely different impact resistance mechanism of the rubber-cement composites with different constraints under cyclic impact loading.