There are many factors, which may affect on concrete quality. One of those is concrete curing. Self-curing concrete is the solution. It may produce by using chemical curing agents. The concept of those agents is to reduce the water evaporation from concrete. This research aims to study the effect of chemical curing agents on the behavior of self-curing concrete. Two different chemical curing agents were used to study the main mechanical properties of concrete. The main variables are; the type of curing agent (Polyethylene glycol "PEG400"–Poly Acrylamide "PAM") and its dosages. The results obtained in terms of compressive, tensile and flexure strength values. Test results showed that the self-curing concrete cured by each agent performed better in hardened properties compared to none cured concrete. Also, curing using the both agents together perform better than using each one individually.

This investigation is carried out to evaluate the repair and strengthening the techniques of elliptical paraboloid reinforced concrete shells with openings. An experimental program of several different techniques in repair and strengthening is executed. The materials, which are considered for strengthening, are; Glass fi ber reinforced polymers GFRP at different position of the shell bottom surface, steel strip and external tie. They loaded by four concentrated loads affected on the corners of the opening. The initial and failure loads as well as the crack propagation for the tested shells at different loading stages, defl ections and failure load for repaired and shells are recorded. A non-linear computer program based on fi nite element techniques is used to study the behavior of these types of shells. Geometric and materials nonlinearities are considered in the analysis. The effi ciency and accuracy of computer program are verifi ed by comparing the program results with those obtained experimentally for the control shell with opening and strengthened shells.

In this study, a new shear strengthening technique for reinforced self-compacting concrete (RSCC) deep beams was suggested and compared with some traditional techniques. An experimental test program consists of sixteen specimens of RSCC deep beams strengthened by different materials such as steel, glass, and carbon fiber reinforced polymers (GFRP and CFRP) was executed. Externally bonded layers (EBLs) and near-surface mounted reinforcement (NSMR) were used as two different techniques. The effects of the new technique which depends on using intertwined roving NSM GFRP rods saturated with epoxy were compared with the other models. The new technique for shear strengthening increases the load capacity from 36% to 55% depending on the anchorage length of GFRP rods. Two-dimensional nonlinear isoperimetric degenerated layered finite elements (FEs) analysis was used to represent the SCC, reinforcement, and strengthening layers of the tested models. The analytical results have been very close to the experimental results.

Usage of precast prestressed concrete hollow core (PPHC) slabs has been extensively spread out in roofing and flooring systems around the globe due to benefits of mass production and fast site construction. In this flooring system, prestressed precast hollow core slabs are used together with or without a cast in place concrete topping. A few research works focused on studying the effect of using concrete topping on enhancement of the structural integrity of the PPHC system. This paper presents an experimental study conducted to investigate the effects of using different types of cast in place (CIP) concrete toppings on the behavior of PPHC slabs. Ten typical full scale specimens of PPHC slabs were prepared in precast concrete plant under quality control program; specimens were classified into five groups. Group (1) includes two control specimens without topping, Group (2) contains two specimens with ordinary reinforced concrete topping, Group (3) involves two specimens with ordinary reinforced concrete topping connected to the top surface of the slab using steel anchors, Group (4) comprises two specimens with fibrous concrete topping, and finally Group (5) includes two specimens with ferrocement topping. All test specimens were tested under static line loading until failure. Cracking patterns, failure modes, cracking and ultimate failure moment capacities, and moment-deflection relationship have been illustrated, discussed, and analyzed in this study. Adding concrete topping to the PPHC slabs enhances flexural behavior directly under static line loading, as the cracking moment resistance was increased by about 6% to 31% and failure moment was increased by about 11% to 41% by using concrete toppings.

This paper presents an experimental and numerical investigation to determine the behavior of steel tubular columns filled with recycled aggregates concrete up to failure under constant axial compression loads. The experimental program included two steel tube columns, four recycled concrete columns and eight composite columns filled with different types of recycled coarse aggregates (granite and ceramic). Different percentages of recycled coarse aggregates: 0, 25 and 50 of the percentage of the coarse aggregates (dolomite) were used. The results of the numerical model that was employed by the finite element program, ANSYS, were compared with the experimental results. The results of the experimental study and the finite element analysis were compared with the design equations using different national building codes: AISC1999, AISC2005 and EC4. The results indicated that the recycled aggregates concrete infill columns have slightly lower but comparable ultimate capacities compared with the specimens filled with normal concrete.