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Three-dimensional printing technology is transforming the construction industry, which is increasingly turning to advanced materials and techniques to meet environmental and economic challenges. This comprehensive literature review evaluated various binder materials, including cement, geopolymers, earthen materials, supplementary cementitious materials, polymers, and biopolymers, with a focus on their environmental impacts and rheological properties. The study revealed an increasing interest in cementitious binders, which deliver essential structural strength and exhibit a wide range of yield stress values (15 to 6500 Pa), influenced by binder type and supplementary materials such as nanoclay. However, the significant CO2 emissions associated with cement pose major sustainability challenges. As a sustainable alternative, geopolymers demonstrate lower yield stress values (800 to 3000 Pa) while ensuring adequate buildability for vertical printing and reducing environmental impact. These findings underscore the need to adopt sustainable binder matrices to align 3D printing construction practices with global sustainability goals. [ABSTRACT FROM AUTHOR]

This study evaluated the freeze-thaw (F&T) resistance of 3D-printed concrete by analyzing the effects of air-entraining agent (AEA) concentrations, curing methods, and core orientations. Concrete specimens (600 × 600 × 150 mm) with 0%, 0.1%, 0.15%, and 0.2% AEA were cured and tested after 28 days. Cores were drilled horizontally and vertically and then subjected to 360 F&T cycles according to ASTM C666/Procedure B. Microstructural analyses (BET, MIP, SEM, XRD) evaluated changes in pore structure. Results showed 25% of the samples endured 300 cycles without significant damage. F&T damage occurred primarily at interlayer bonds. Horizontal cores showed greater durability due to reduced interlayer gaps. AEA at 0.1% significantly improved F&T resistance and increased dynamic modulus by 15%. BET and MIP analyses showed a 20% increase in average pore size, while SEM confirmed air voids. Optimized AEA levels and curing methods improved the durability of 3D-printed concrete in frost-prone conditions. [ABSTRACT FROM AUTHOR]

A comprehensive evaluation of the results obtained according to the measurement of radon gas in buildings and concrete, which is the most consumed material in the world after water, in accessible studies carried out in the last 40 years is the main objective of this study. The paper additionally aims to address the gap in the literature by comparatively determining which parameters affect radon–concrete and radon–building relationships. The scientific knowledge compiled within the scope of this article was presented under the main headings of radon and radon gas measurements in concrete and buildings. Radon gas, also known as the "invisible killer", is considered the second most important cause of lung cancer after smoking (the gas is responsible for 3–14% of lung cancer cases in the world). The results determined that radon concentration limits have been applied in the range of 100–400 Bqm−3 in houses and 100–3700 Bqm−3 in workplaces. Studies conducted on the exhalation rate of radon showed that the radon exhalation rate of concrete may be in the range of 0.23–510 Bqm−2 h−1. The results of indoor radon concentration measurements revealed that values between 4.6 Bqm−3 and 583 Bqm−3 were obtained. Despite the existing literature, some researchers state that there is an urgent need for an improved and widely accepted protocol based on reliable measurement techniques to standardize measurements of the radon exhalation rate of construction materials and the indoor radon concentration of buildings. [ABSTRACT FROM AUTHOR]

The effects of air-entraining admixture (AEA), curing process, and core direction were studied as parameters in terms of their effect on the physicomechanical properties of 3D printed concrete. Four different AEA dosages (0%, 0.1%, 0.15%, and 0.2% by dosage of binder) were used to prepare the mixtures used for 3D printing. The influence of anisotropy on the printed concrete was studied by testing the cores drilled from the horizontal and vertical directions of the 3D concretes. The study also examines the efficiency of a specific spray-deposited chemical curing technique for improving the strength characteristics of 3D concrete. The addition of AEA reduced the unit weight significantly, thereby making the concrete ideal for lightweight structural members. Ultrasonic pulse velocity (UPV) testing on 3D printed samples showed that voids and air entrainment during the deposition process reduced the wave velocities. The ultrasonic wave velocity of cores drilled parallel to the printing direction was found to be slightly higher than cores perpendicular to the printing direction. However, the observation from the nondestructive tests did not agree with the compressive strength studies. The compressive strength of the cores drilled perpendicular to the direction of printing was higher than those drilled parallel, which can be due to the layers formed in the concrete during the filament deposition process. The 3D printing process reduced the compressive strength and induced anisotropy. The compressive strengths were reduced with air entrainment in the sample that was not 3D-printed. However, in the 3D-printed samples, 0.1% of AEA increased the vertical and horizontal strength compared to the samples without AEA. AEA in small quantities was found to be capable of improving the rheology of the mix and reducing the possible defects during the printing process, which resulted in better interlayer bonding. The durability aspect of air entrainment was studied using capillary water absorption, and it was found that the capillary water absorption increased with the addition of AEA. Microstructural studies using the Brunauer–Emmett–Teller (BET), Mercury Intrusion Porosimetry (MIP) and Scanning Electron Microscopy (SEM) on the 3D concrete revealed that the volume and size of the pores in the hardened matrix increased with the addition of AEA. The mechanical and durability studies showed that the optimal percentage of AEA is 0.1%. [ABSTRACT FROM AUTHOR]

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In this study, the effect of evaporator pinch point temperature difference (ΔTPP,e) value in Organic Rankine Cycle (ORC) on system performance was determined. Under different applications of ORC, optimum ΔTPP,e value has been determined in ORC systems designed with different heat source temperatures. By changing the ΔTPP,e value, the heat input provided to the system, the mass flow of organic fluid, the evaporation pressure and the enthalpy drop in the turbine are affected. In thermodynamic optimization, the objective function is determined as turbine power maximization. Genetic algorithm optimization technique is used. Within the scope of low and high temperature ORC applications, the optimum ΔTPP,e value of different organic fluids under 10 different heat source temperatures (Low, 90-130 °C; High, 250-290 °C) has been determined. Low temperature organic fluids have been selected from dry, isentropic, wet and new-generation categories. High temperature organic fluids have been selected from the alkane, aromatic hydrocarbon, and siloxane categories. The effect of ΔTPP,e on fluids of different categories was determined for low and high temperature ORCs. It has been determined that taking the ΔTPP,e value constant regardless of the heat source temperature and organic fluid causes performance loss in ORC. [ABSTRACT FROM AUTHOR]

The purpose of this research was to compare self-compacting concrete (SCC) and conventional concrete (CC), which are used in beams with dense reinforcement, in terms of their carbonation resistance. It was observed that, in both air and moist curing environments, SCC had less carbonation depth than CC and the carbonation depths of both SCC and CC samples stored under moist curing were less than those of samples undergoing air curing. The experiments also showed that, regardless of the type of concrete, carbonation depth decreased with increasing concrete strength class. Furthermore, the study showed that beams produced from SCC were more uniform than CC beams. Consequently, instead of CC, SCC can be used to produce any reinforced concrete components in order to provide increased carbonation resistance and uniformity. The findings of this study may thus lead to increased usage of SCC in construction sites. [ABSTRACT FROM AUTHOR]

The neutron equivalent dose rates (µSv/h) of gypsum, steel-reinforced rubber waste tire, and gypsum-waste tire rubber sandwich composite samples were investigated. Prepared samples were irradiated with241Am-Be neutrons and transmission values were obtained using dose equivalent rates measured with a BF3neutron detector. Results were compared to those of concrete, and as a result of neutron shielding, the performance of gypsum, waste tire, and waste tire (steel-reinforced rubber) embedded gypsum samples was higher than that of concrete. This information may be useful for shielding design of nuclear application areas. [ABSTRACT FROM AUTHOR]

Abstract: In this study, addition of both nano-SiO2 (NS), nano-Al2O3 (NA) and nano-Fe2O3 (NF) powders and their binary and ternary combinations on the compressive strength and capillary water absorption of cement mortars containing fly ash (FA) were investigated. Powder amounts were used at ratios corresponding to 0.5wt%, 1.25wt% and 2.5wt% of the binder for all mixtures. Results show that addition of any single type of oxide powders at 1.25% increased compressive strength of the mortars much further than the other proportions. The use of NS+NA powders at 1.25% improved the compressive strength by the most compared to the control specimen. For all binary powder combinations, the rate of increase in strength reached generally their peak on the 28th day and gradually decreased through aging. Among all groups, the best results were obtained from the mortars added with NS+NA+NF powders at 1.25%. For this particular mortar, 7–32% increase in the compressive strength and 14% decrease in the capillary absorption were determined relative to the control specimen. Agglomeration formation due to excessive use of nano powders and their pozzolanic activity should be investigated in detail. The results were also compared with those obtained from Oltulu and Şahin (2011). [Copyright &y& Elsevier]

The effect of air-entraining admixture (AEA) on the fresh and rheological behavior of mortars designed to be used in 3D printers was investigated. Blast furnace slag, calcined kaolin clay, polypropylene fiber, and various chemical additives were used in the mortar mixtures produced with Super White Cement (CEM I 52.5 R) and quartz sand. In addition to unit weight, air content, and compressive strength tests, in order to determine the stability of 3D printable mortar elements created by extruding layer by layer without any deformation, extrudability, buildability, and open time tests were applied. Fresh and rheological properties of 3D printable mortars were also determined. It was concluded that the addition of AEA to the mortars decreased the unit weight, viscosity, yield, and compressive strength, but increased the air content, spread diameter, initial setting time, and thixotropy of 3D printable mortar. It is recommended to develop a unique chemical admixture for 3D printable mortars, considering the active ingredients of the chemical additives that affect fresh and rheological performance of mortar such as superplasticizer, viscosity modifying, and cement hydration control. [ABSTRACT FROM AUTHOR]