The incorporation of Supplementary Cementitious Materials (SCMs) greatly influences the pore structure and rheological properties of High Performance Concrete (HPC). Rheology affects the behaviour of hardened concrete and pore structure can give insight into the microstructure of the concrete and its performance in terms of both strength and durability. Hence, modification of rheology which is possible to control at the time of production can be extremely helpful in enhancing the performance of concrete. In this paper, an attempt has been made to link rheology with pore structure of HPC. The approach will provide better understanding and controlling of HPC and will give impetus to utilize SCMs in the production of HPC. The use of SCMs conserve energy and saves the use of cement which results in reduction of emission of carbon dioxide in the atmosphere. SCMs such as Fly Ash (FA) and Silica Fume (SF) were incorporated as partial cement replacements for the preparation of binary and ternary blended systems. The pore structure of hardened blended systems study was conducted using MIP and rheology such as plastic viscosity and yield stress using the two-point test. It was observed that the incorporation of SF decreased the plastic viscosity of concrete as compared to the reference mix whilst the FA content increased the plastic viscosity and a reasonable relationship exists between plastic viscosity and yield stress. The ternary systems reduced volume of large pores as compared to the reference mix. There exists a reasonable relationship between rheology of fresh concrete and pore structure of hardened concrete.

The feasibility of the preparation of strain-hardening cementitious composites (SHCC) relies to a great extent on the properties of one of its main constituents, quartz sand. The particle size distribution (PSD) of such sand should satisfy certain criteria specifically for SHCC to deliver quasi-static responses under tensile stress. The successful use of naturally available sand helps preparation of a cost-effective SHCC. The aim of the current paper was to evaluate the potential use of white quartz sand that is naturally available in the Arabian Gulf with different PSDs to produce different mixtures of SHCC. These mixtures were prepared with different ranges of workability to obtain optimized fresh and hardened properties with improved strain-hardening response. The effect of workability on the compressive, flexural and tensile properties has shown that there is an optimal workability range among the defined ranges that provided improved strain-hardening responses under tensile stress. The mode o...

Cement is one of the main constituents of concrete material and it is one of the main sources of carbon dioxide emissions in the environment. Fillers within a range of 5–7% from different sources can be used as a replacement of cement without compromising the properties of concrete or even tailoring for required property. This paper investigates the influence of inactive silica filler and silica fume on the mechanical- and durability-related properties of concrete with different strengths. The investigated mechanical properties focused on compressive strength at different ages up to 400 days, while the durability-related properties focused on porosity and rapid chloride ion penetrability (RCPT). Two types of ultrafines, namely quartz ultrafine and silica fume, were used. Concrete mixtures with four different water/binder ratios (0.25, 0.30, 0.35, 0.40) were prepared for various dosages of quartz ultrafine (0%, 5%, 8%, 10%, 15%, 25%, and 35%) and different dosages of silica fume (0%, 8%, 10%, and 12%). The results revealed that the compressive strength and durability related properties of concrete with different dosages of ultrafines and silica fume were significantly affected; however, there was a negative impact of ultrafine filler on the compressive strength after replacement of more than 8% of ultrafines. The strength relationships for the concrete with different water-to-cement ratio were assessed and certain modifications were proposed for ultrafines and silica fume. Predictive models were proposed for predicting the compressive strength of concrete in terms of RCPT and porosity for different levels of replacements of ultrafines and silica fume.

The present paper thoroughly investigates the effects of mix design with various water-to-binder (W/B) ratios, types of mineral admixture and types and sizes of local sands on the tensile ductility of engineered cementitious composites (ECC). White and red dune sands—denoted W and D, whereas their sieved forms are denoted SW and SD, respectively—were collected from the Arabian Desert, the second largest on the earth. Fly ash (FA) and ground granulated blast furnace slag (GGBFS) were separately used as mineral admixtures in the production of ECC. The development of ductility in ECC mixtures incorporating FA was found to reduce with curing time, whereas it was found to increase with GGBFS. An ECC mixture containing 62% GGBFS with W/B ratio of 0.35 has delivered the best fresh and hardened properties with strain capacity of 4.2% and tensile strength of 5.2 MPa at 28 days. Water sorptivity of fully cracked dune sand–based ECC mixtures was lower than that given by normal concrete. It is concluded that dune sand–based ECC mixtures have provided comparable results to the reference silica sand–based ECC mixtures.

The current study aims to investigate the effect of using hybrid bars on the bending characteristics of hybrid fiber-reinforced concrete (FRC) beams. For this purpose, a series of flexural tests on FRC beams were conducted. Four FRC beams were fabricated, each with a section of 120 mm × 185 mm and an overall length of 1.5 m. The FRC beams’ tension reinforcement consisted of a hybrid configuration of steel and glass fiber-reinforced polymer (GFRP) rebars. The concrete mix included a hybrid fiber content of 1% by volume, with 0.75% for hooked-end steel fibers (SF) and 0.25% polypropylene fibers (PP). The simply supported FRC beams were tested under the action of two-point loads. The results demonstrated that the inclusion of hybrid fibers substantially improved the crack widening and propagation in FRC beams compared to normal concrete (NC) beams. The maximum load capabilities of the FRC beams surpassed those of the NC beams up to 13.2%. The GFRP bars further enhanced the beams’ load-carrying capacity with an observed increase of up to 42.5%, when compared to the steel-reinforced FRC beam (BFRC-3S). Additionally, hybrid reinforcement improved ductility, with increases of 39.1% and 167.1% when one or two GFRP bars were replaced by steel, respectively.

Currently, reinforced concrete (RC) columns rely heavily on closely spaced steel ties for confinement and ductility under axial compression. However, tie congestion and construction limitations often reduce confinement efficiency, creating a need for alternative hybrid reinforcement solutions. A series of ten one-third scale circular RC short column specimens of 240 mm diameter and 1.2 m height were fabricated to investigate the effects of different internal confinement configurations. The columns were reinforced longitudinally with six steel rebars of 10 mm diameter (a steel ratio of 1%), and transversely with 6 mm diameter steel ties at varying spacings. All column specimens were cast using 25 MPa concrete, and their cores were internally wrapped with welded wire mesh (WWM) and carbon fiber reinforced polymer (CFRP) strips to enhance their confinement performance. The experimental program focused on evaluating the axial load capacity, axial strain, and ductility. Compared to control RC columns having conventional steel rebar ties, the specimens incorporating hybrid internal confinement of WWM and CFRP exhibited up to 38% and 180% increases in peak loads and ductility, respectively, and failed by buckling of the longitudinal steel bars, followed by rupture of the CFRP strips/WWM layers. These findings suggest that the use of internally wrapped composite systems in RC columns is particularly suitable for applications where dimensional constraints are critical. Additionally, an analytical model was proposed to predict the peak loads of the confined columns. The peak load predictions for various confinement configurations aligned well with the corresponding peak loads measured in experiments.