The bond characteristics between steel fiber and a cementitious matrix play a crucial role in controlling the performance of steel fiber–reinforced concrete (SFRC). The bonding mechanisms of SFRC have attracted considerable attention over the last four decades and are still active research. This overview provides a state-of-the-art understanding of the major mechanisms governing the pullout behavior of steel fibers. Characteristics of different types of bond and their functions have been explained in detail. Primarily important are bond strength in each of its likely failure modes. Different factors affecting the bond strength include geometry, orientation and embedded length of fiber as well as matrix strength. A review of existing analytical papers investigates the bond mechanisms between steel fiber and cementitious matrix. The review shows that the most successful method to improve bond slip is to reinforce concrete with pre-deformed fibers. This review also provides useful information on how fiber geometry influences pullout behavior from the matrix for a known relative strength between the two constituents. The theory of bonding and its related parameters is surveyed. Finally, recommendations for future research and optimum applications of SFRC are considered.

Great efforts are being made at Brunel University, UK in attempt to develop natural fiber composites with desired structure and good overall properties for construction. This work focuses on the mechanical and morphological characterization of the pultruded composite rods made from hemp and wool fiber reinforcements. The results showed that the composite using polyurethane resin system has higher specific tensile and compressive strength as well as the Young's and compressive moduli compared with the polyester and vinyl ester composites, while the polyester composite exhibits better flexural strength. The SEM observation of the cross section and layered polyester and polyurethane composites has found defects on the interface of fibers and resin matrix. It is also revealed that fibers are not evenly distributed in the composites and more resin aggregates in areas close to rod surface. Meanwhile, voids have been noticed existing in both composites, but more of them are found in the polyurethane-matrix rod, which correlated to the higher water absorption for this composite.

The manufacturing process of geopolymer cement generally uses alkaline solutions mixed with alumina-silicate prime materials to form a cement paste. Other factors may be set up for the designated experiment, e.g., material constituents, activator’s concentration and curing regimes. One of the latent factors influencing the properties of geopolymer, which has received less attention, is a mixing method. General mixing and separate mixing processes, which have been previously studied, were synthesized as controlled procedures and compared with another alternative new mixing method called the pre-dry mixing process. The results have shown that the pre-dry mixing process provided high potential heat liberation, which could prove beneficial for curing purposes. It is confirmed that the proper mixing order leads to better results, especially for any of the alkaline-activated cementitious binders. With more practicality in field application, by just adding water, this process could be developed and applied in ambient temperatures.

This paper presents the fibre-matrix interfacial properties of hooked end steel fibres embedded in ultra-high performance mortars with various water/binder (W/B) ratios. The principle objective was to improve bond behaviour in terms of bond strength by reducing the (W/B) ratio to a minimum. Results show that a decrease in W/B ratio has a significant effect on the bond-slip behaviour of both types of 3D fibres, especially when the W/B ratio was reduced from 0.25 to 0.15. Furthermore, the optimization in maximizing pullout load and total pullout work is found to be more prominent for the 3D fibres with a larger diameter than for fibres with a smaller diameter. On the contrary, increasing the embedded length of the 3D fibres did not result in an improvement on the maximum pullout load, but increase in the total pullout work.