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Concrete is classified as a multi-composite material comprising three phases: coarse aggregate, mortar, and interfacial transition zone (ITZ). Fine and coarse aggregates occupy approximately 70–85% by volume, of which coarse aggregate typically constitutes more than two-thirds of the total quantity of aggregate by volume. The current study investigates the concrete performance produced using various recycled construction and by-product industrial waste coarse aggregates. Six types of coarse aggregates: manufactured limestone, quartzite, natural scoria, by-product industrial waste aggregate, and two sources of recycled concrete aggregates with densities ranging from 860 to 2300 kg/m3 and with different strength properties were studied. To determine the coarse aggregate contribution to the overall concrete performance, lean and rich concrete mixtures (Mix 1 and Mix 2) were used. Mix 1 (lean mixture) consisted of a ratio of water to cement (w/c) of 0.5 and cement content of 300 kg/m3, whereas a higher quantity of cement of 500 kg/m3 and a lower w/c ratio of 0.3 were used for Mix 2 (rich mixture). The results showed that while the compressive strength for different aggregate types in Mix 1 was comparable, the contribution of aggregate to concrete performance was very significant for Mix 2. Heavyweight aggregate produced the highest strength, while the lightweight and recycled aggregates resulted in lower mechanical properties compared to normal weight aggregates. The modulus of elasticity was also substantially affected by the coarse aggregate characteristics and even for Mix 1. The ACI 363R-92 and CSA A23.3-04 appeared to have the best model for predicting the modulus of elasticity, followed by the ACI-318-19 (density-based formula) and AS-3600-09. The density of coarse aggregate, and hence concrete, greatly influenced the mechanical properties of concrete. The water absorption percentage for the concrete produced from various types of aggregates was found to be higher for the aggregates of higher absorption capacity. [ABSTRACT FROM AUTHOR]

High molar mass materials (nano-silica slurry [NSS] and aggregate of steel furnace slag [ASFS]) can improve concrete shielding properties. However, only a few studies have been reported in this regard. Hence, this paper aims to determine the effect of NSS and ASFS on the properties of the resulting steel slag heavyweight concrete (SSHWC). The use of NSS in this study is a novel contribution. Furthermore, the maximum percentage of NSS to be introduced into the concrete for maximum effect was also optimized. This study also implemented an investigation program with six concrete mixtures prepared using ASFS as the primary by-product aggregate. The engineering, X-ray, and γ-ray attenuation characteristics of the SSHWC were evaluated. The results showed that the addition of NSS in SSHWC at the optimal content of 3% by weight of cement improved the X-ray shielding by 6.4%. Besides, all the concrete’s engineering and γ-rays’ properties were enhanced correspondingly.

Concrete is classified as a multi-composite material comprising three phases: coarse aggregate, mortar, and interfacial transition zone (ITZ). Fine and coarse aggregates occupy approximately 70–85% by volume, of which coarse aggregate typically constitutes more than two-thirds of the total quantity of aggregate by volume. The current study investigates the concrete performance produced using various recycled construction and by-product industrial waste coarse aggregates. Six types of coarse aggregates: manufactured limestone, quartzite, natural scoria, by-product industrial waste aggregate, and two sources of recycled concrete aggregates with densities ranging from 860 to 2300 kg/m3 and with different strength properties were studied. To determine the coarse aggregate contribution to the overall concrete performance, lean and rich concrete mixtures (Mix 1 and Mix 2) were used. Mix 1 (lean mixture) consisted of a ratio of water to cement (w/c) of 0.5 and cement content of 300 kg/m3, whereas a higher quantity of cement of 500 kg/m3 and a lower w/c ratio of 0.3 were used for Mix 2 (rich mixture). The results showed that while the compressive strength for different aggregate types in Mix 1 was comparable, the contribution of aggregate to concrete performance was very significant for Mix 2. Heavyweight aggregate produced the highest strength, while the lightweight and recycled aggregates resulted in lower mechanical properties compared to normal weight aggregates. The modulus of elasticity was also substantially affected by the coarse aggregate characteristics and even for Mix 1. The ACI 363R-92 and CSA A23.3-04 appeared to have the best model for predicting the modulus of elasticity, followed by the ACI-318-19 (density-based formula) and AS-3600-09. The density of coarse aggregate, and hence concrete, greatly influenced the mechanical properties of concrete. The water absorption percentage for the concrete produced from various types of aggregates was found to be higher for the aggregates of higher absorption capacity.

• Overview on the heavyweight concrete (HWC) constituent materials, design, production and application. • Mechanical and physical properties of HWC. • The constituent materials utilised to produce HWC. • The importance of HWC to isolate harmful radiation. • Scientific knowledge gaps have been proposed in HWC production. Promoting concrete quality is a logical inevitable choice for humanity in global revolutionary development. This study highlights one of the most important types of concrete, namely, the high density concrete, which is used widely in nuclear power plants and many other modern scientific and industrial applications. It can efficiently absorb and attenuate the dangerous types of radiation. It is low cost. These features make this type of concrete important in many relevant fields and applications. It is used as partition walls for rooms of examination in hospitals, laboratories and others. The attenuation degree of the biologically dangerous types of radiation (such as gamma rays, alpha rays, beta rays and X-ray) during the propagation of these rays through the mass of the shielding materials is in proportion with the atomic mass of the shielding material. Some of these rays can be stopped easily by a piece of paper (like α) or a thin layer of aluminium (such as β-ray). However, some of them (such as gamma rays) has ultrapenetration ability and can penetrate through the living bodies and cause destructive ionisation to biological cells. Thus, the concrete material that can properly shield from such rays is important and is the primary focus of discussion of this review. An overview of the works conducted to produce high density concrete for various engineering and radiation attenuation applications is provided. The important aspects are described in detail, such as the high-density concrete properties, materials used, physical and chemical material's properties, mechanical properties and durability and the effect of the interfacial transition zone's density on the properties of heavy weight concrete. The major advantages and contributions of this study are not restricted to the comprehensive review of the past works that led to the development this important type of concrete. The knowledge gap in this field of work is highlighted. An extensive review of literature reveals the difficulties related to the scarcity of work on the drastic reduction of the water/cement ratio to achieve high density concrete with reasonable workability using modern chemical admixtures, the approach of promoting high-density concrete through hybridisations of fibres and the reduction of their permeability by using the nanomaterials as mineral admixtures. [ABSTRACT FROM AUTHOR]

The radiation shielding properties have been investigated for heavyweight high performance fiber reinforced cementitious composites (HPFRCC) produced with silica sand-quartz powder blend, granulated ferrous waste or barite as fine aggregate. The study also dealt with the effects of water-binder ratio (aggregate concentration), curing regime and steel fiber volume fraction on the radiation attenuation coefficient. Linear (µ) and total mass attenuation coefficients (µ/ρ), half-value layer (HVL) and tenth-value layer (TVL) were determined at photon energies of 0.2 MeV, 0.662 MeV and 1.25 MeV. The total mass attenuation coefficients (µ/ρ) were also calculated using XCOM computer code for the novel shielding cementitious composites. The results showed that it is possible to produce HPFRCC with dry unit weight greater than 3745 kg/m 3 and compressive strength of 190 MPa by utilizing granulated ferrous waste as fine aggregate. HPFRCC incorporating barite as fine aggregate enhances the shielding efficiency against 0.2 MeV, whereas using granulated ferrous waste as fine aggregate leads better performance for the attenuation of photons at energies of 0.662 MeV and 1.25 MeV. [ABSTRACT FROM AUTHOR]

The permeation properties of concrete are strongly influenced by the degree of saturation of capillary pores. Test results of the Autoclam air permeability index (API) of radiation shielding concrete are presented. Concrete specimens were made with CEM I and CEM III/A cements and special aggregates for radiation shielding: crushed barite, magnetite, serpentine and amphibolite. Two procedures of accelerated drying with simultaneous measurement of moisture distribution in the specimens were proposed. The specimens were tested at different RH levels from a fully saturated state to an oven dried state. The linear relationship between the API and RH was obtained. Effects of heavyweight and hydrogen-bearing aggregates on air permeability index were revealed. [ABSTRACT FROM AUTHOR]

In this contribution the effect of nanosilica (NS) on the behavior of cement mortars containing quartz aggregate and two types of heavyweight aggregates (magnetite and barite) exposed to elevated temperature will be investigated. The cement mortars have been modified with nanosilica in quantities of 1%, 2%, 3%, 4% and 5% (by weight of cement). The samples were exposed to the elevated temperatures of 200 °C, 400 °C, 600 °C and 800 °C, respectively. The mass loss, flexural and compressive strength of the cooled specimens were determined. Additionally, by means of scanning electron microscopy (SEM) and optical microscopy the structure defects have been determined. The results clearly demonstrate that there is an optimal nanosilica content, in the cement mortar containing quartz and magnetite aggregate, improving the thermal resistance and preventing the crack extension (especially in the range of 200–400 °C). However, the study has also shown that cement mortars containing barite aggregate tend to crack and exhibit spalling as a result of low thermal resistance of the aggregate. [ABSTRACT FROM AUTHOR]

Alkali-silica reaction (ASR) is considered as a potential aging-related degradation phenomenon that might impair the durability of concrete in nuclear containments. The objective of this paper is the application of digital analysis of microscopic images to identify the content and size of quartz grains in heavy mineral aggregates. The range of investigation covered magnetite and hematite aggregates, known as good absorbers of gamma radiation. Image acquisition was performed using thin sections observed in transmitted cross-polarized light with λ plate. Image processing, consisting of identification of ferrum oxide and epoxy resin, and the subsequent application of a set of filtering operations resulted in an adequate image reduction allowing the grain size analysis. Quartz grains were classified according to their mean diameter so as to identify the reactive range. Accelerated mortar bar tests were performed to evaluate the ASR potential of the aggregates. The SiO2 content in the heavyweight aggregates determined using the image analysis of thin sections was similar to XRF test result. The content of reactive quartz hematite was 2.7%, suggesting that it would be prone to ASR. The expansion test, according to ASTM C1260, confirmed the prediction obtained using the digital image analysis. [ABSTRACT FROM AUTHOR]

Alkali-silica reaction (ASR) is considered as a potential aging-related degradation phenomenon that might impair the durability of concrete in nuclear containments. The objective of this paper is the application of digital analysis of microscopic images to identify the content and size of quartz grains in heavy mineral aggregates. The range of investigation covered magnetite and hematite aggregates, known as good absorbers of gamma radiation. Image acquisition was performed using thin sections observed in transmitted cross-polarized light with λ plate. Image processing, consisting of identification of ferrum oxide and epoxy resin, and the subsequent application of a set of filtering operations resulted in an adequate image reduction allowing the grain size analysis. Quartz grains were classified according to their mean diameter so as to identify the reactive range. Accelerated mortar bar tests were performed to evaluate the ASR potential of the aggregates. The SiO2 content in the heavyweight aggregates determined using the image analysis of thin sections was similar to XRF test result. The content of reactive quartz hematite was 2.7%, suggesting that it would be prone to ASR. The expansion test, according to ASTM C1260, confirmed the prediction obtained using the digital image analysis.

A number of medium to small sized barite deposits are located within the Mor Mountain Range, Pakistan. The present study evaluated eight barite deposits from the Lasbela area, Balochistan, Pakistan, representing the different parts of the Mor Range. Evaluation of the barite content and those properties important in the production of heavyweight concrete aggregate indicated that the material would be suitable for the construction of earthquake resistant buildings and for radiation shielding. [ABSTRACT FROM AUTHOR]

• Magnetite aggregate, carbon fibre and carbon nanotube were used. • Mechanical properties of hybrid composites were presented. • Best conductive filler combination is 100 MA, 0.3wt.%CF and 0.05 wt.%CNT hybridization. • 17% improvement of compressive strength can be observed at the best mix. • Maximum fractional change in resistivity of 44.7% has been achieved. Self-sensing cementitious composites have attracted substantial attention as a multifunctional construction material for structural health monitoring (SHM). This study aimed to develop self-sensing cementitious composites using a combination of macro, micro and nanoscale conductive fillers, as the hybrid fillers can take advantage of different types of conductive fillers and create a synergistic effect. Magnetite aggregate (MA), carbon fibre (CF) and carbon nanotube (CNT) were combined and used as the conductive fillers for the fabrication of self-sensing cementitious composites, where the mechanical properties, electrical properties and piezoresistive performance were studied. The MA at 100 wt% achieve the optimal mechanical properties, leading to a 5% increment in compressive and a 25% increment flexural strength with a value of 37.3 and 5.7 MPa. Additionally, multiple reinforcing effects were achieved when combining different types of functional fillers, which a single filler cannot achieve. The best conductive filler combination is MA, CF and CNT hybridisation, each at 100, 0.3 and 0.05 wt%, respectively. A 17% improvement in terms of compressive strength can be observed. And the piezoresistive response can achieve a maximum fractional change in resistivity of 44.7% and demonstrates enhanced linearity, repeatability, signal to noise ratio and stability. [ABSTRACT FROM AUTHOR]

• CIP and HP powders did not have a significant effect on mechanical properties. • Electrical conductivity gradually reduced with the particle content. • CIP and 12 mm CF composite produced a shielding efficiency of 51.30 dB. • 3 mm and 12 mm CF composite generated an EMI SE of 50 dB. • Limitations in the simulation software led to mismatch with experimental results. Research into electromagnetic interference (EMI) shielding has been growing over the last couple of decades due to shortcomings of existing methods and increased demand. Therefore, the construction industry has also been interested in fabricating a cement-based composite that could be used for EMI shielding without the use of additional cladding material. This research is focused on fabricating a cement-based composite that could be used for EMI shielding with the addition of carbonyl iron powder, heavyweight aggregate powder, and carbon fibres. Several mix designs were carried out by varying the additives used to find the content that would produce optimal properties. All the mixes were tested for their mechanical, electrical conductivity, and EMI shielding properties. EMI shielding tests were carried out per ASTM D4935 – 18 standard within 30 MHz to 1.5 GHz frequency range. The mix consisting of 20% carbonyl iron powder in combination with 0.7% of 12 mm CF produced an EMI shielding of 51.30 dB, which was the best result obtained for any mix in this research. An additional simulation was carried out using CST Studio software to see the theoretical level of shielding produced by these mixes. The simulation results showed near identical results to that of the experimental with smaller variation at specific frequencies. [ABSTRACT FROM AUTHOR]

Any sound concrete, in sections of sufficient thickness, can be used to construct a satisfactory biological shield. When space permits, conventional concrete is the most economical, satisfactory shield against radiation. However, when space is a consideration, high density concrete can be used for shielding. Most high density concrete for shielding has been made with naturally occurring iron ores, titaniferous iron ores, "hydrous iron ores, and barite. Although structural strength is an important factor in high density concrete, workability and density have been the major factors previously studied. This investigation showed that high strength concrete can be made using materials that provide high density, and that high density concrete can be made using proportions that ensure high strength. When high strength and high density are both desired, they can be attained by a direct combination of the standard practices developed for attaining each condition separately. Concrete made as part of this study using magnetite aggregate or ilmenite aggregate having a hardened unit weight of about 230 lb per cu ft had a compressive strength of 9000 psi at 7 days and I 1,000 psi at 28 days. [ABSTRACT FROM AUTHOR]

• Reuse of steel furnace slag aggregate to produce steel slag heavyweight concrete. • High strength heavy weight concrete modified with nano zinc and silica. • Physical, mechanical and fluid transport properties enhancement. • Gamma-ray attenuation property of nano zinc and silica heavyweight concrete. Due to the growing nuclear energy sector worldwide, it has been a global interest among researchers to improve the harmful radiation isolation properties of concrete for preserving both environment and human safety in nuclear power plant applications. While nano zinc oxide, nano-silica and steel furnace slag have high molar mass and favorable physical properties to improve high energy radiation attenuation properties of the concrete, scarce body of literature on the subject matter was reported. Hence, the study was aimed to investigate the suitability of the addition of nanomaterials such as nano-silica and nano zinc oxide for improving the mechanical, fluid transport and gamma-ray attenuation properties of heavyweight concrete (HWC) containing aggregate of steel furnace slag (ASFS). A new contribution of this study was the use of nano zinc oxide and nano-silica in concrete binder formulation to enhance the gamma ray shielding ability of concrete. A method was established for the optimization of the nano zinc oxide content used in combination with a constant amount of nano-silica to improve the various performance of heavy weight concrete. An investigation program was implemented with six concrete mixes which were prepared by utilizing ASFS with the addition of a superplasticizer, 3% of nano-silica in combination with (0.5–2.5%) of nano zinc oxide as an additive to produce high strength heavy weight concrete. The mechanical properties, fluid transport characteristics and γ-ray shielding performance were evaluated for hardened concrete samples. The inclusion of 1.5% nano zinc and 3% of nano-silica enhances the gamma-ray shielding and compressive strength by 16.3 and 6.6%, respectively, at 28 days as compared to the control mix (without nanomaterials). Besides, all the mechanical and fluid transport properties of the concrete were improved correspondingly. In conclusion, the combined use of nano-silica and nano zinc oxide is suitable to enhance mechanical strength, fluid transport and high energy radiation attenuation performance of steel furnace-slag heavyweight concrete (SSHWC). [ABSTRACT FROM AUTHOR]

• Nano-calcium carbonate (NCC) as a nano-additive enhances the properties of heavyweight concrete. • The optimal strength, fluid transport and gamma ray attenuation were achieved with 2% NCC. • Combination of silica slurry and NCC improved the various properties of heavyweight concrete. As the nuclear energy sector continues to grow worldwide, the improvement of concrete's radioactive isolation properties for preserving both the environment and human lives in nuclear power plant applications has received a global interest among researchers. Although nano-silica, nano-calcium carbonate, and steel furnace slag have high molar mass and favorable physical properties to improve the concrete's radioactive insulation properties, scarce literature on the subject matter has been published. The goal of this study is to investigate the appropriateness of using nanomaterials such as nano-silica slurry and nano-calcium carbonate as additives for the production of steel furnace slag (aggregate of steel furnace slag: ASFS)-based heavyweight concrete (HWC) with improved durability, mechanical strength, and gamma (γ)-ray attenuation properties. A new contribution of the study is the use of nano-SiO 2 slurry and nano-CaCO 3 in concrete binder formulation to enhance concrete gamma-ray shielding capability. An optimized content was developed for the nano calcium carbonate, in combination with a constant amount of nano-silica slurry, to improve the performance of the HWC. An investigation program was implemented with eight concrete mixes, which were prepared by utilizing ASFS as the main aggregate with 3% of nano-silica slurry in combination with (0–3%) of nano-calcium carbonate as additives to produce high strength HWC. The hardened concrete samples were evaluated for mechanical strength, fluid transport and γ-ray shielding properties. The effect of 3% nano-SiO 2 slurry and 2.0% nano-CaCO 3 on the compressive strength and gamma-ray shielding increased by 10.3 and 3.4%, respectively, at 28 days as compared to the control mix without nanomaterials additives. The other mechanical and fluid transport properties of the concrete were also improved significantly. In conclusion, the combined use of nano-silica slurry and nano-calcium carbonate would enhance the mechanical strength, fluid transport and γ-ray shielding properties of steel furnace-slag heavyweight concrete. [ABSTRACT FROM AUTHOR]