New eco-friendly thermal-casting ductile CPNC-concrete and CPNC-mortar materials have been developed without Portland-cement or water-use. It needs three hours for thermal synthesis. It contains 5%, 10% or 15% green natural nanoclay–polymer nanocomposite CPNC as a bonding-agent instead of Portland-cement for mixing with sand and crushed-stones by heating at 250 °C in electric ovens. CPNC is a dry powder consisting of 5% montmorillonite (MMT) nanoclay and 95% high-density polyethylene (HDPE). The study includes mixing, thermal synthesis, mechanical, fracture, and ductility property testing, and characterizations of the chemical composition, microstructure morphology and homogeneity using EDAX, SEM and XRD. It has new properties, such as a homogenous-microstructure with bonding, self-compaction abilities, no-cracks, ductility, good compressive and tensile strengths, and good fracture properties. It does not exhibit steel corrosion; it has rapid processing, no-water curing, low-density, no-shrinkage cracks, no-sudden failure, no-pollution utilizing a new manufacturing technique. CPNC-concrete is developed to stop the Portland-cement industry problems, to produce a clean and green environment without Portland-cement damage for human beings and to conserve drinking water. It has potential for different applications in construction, and it is suitable for 3D techniques with fast construction. Furthermore, this material requires new special codes for design and construction. Progresses in fields of nanoclay-based polymer nanocomposite science30, geotechnical engineering31, structural engineering and concrete structure construction17 suffer from serious problems due to using Portland-cement; these issues have encouraged us to try to solve the problems with concrete and Portland-cement by using natural green applications of nanocomposites instead of Portland-cement11. Therefore, this research idea is studied, and these results can solve Portland-cement problems and find new materials of suitable processing techniques and properties that lead to new construction techniques which will need new design codes to replace the existing design codes17 regarding Portland-cement materials and concrete construction fields. In this study, we develop a new application of nanoclay-based polymer nanocomposites44 as green nanocomposite cements to replace Portland-cement for concrete and construction industries. As a result of the study, changes between conventional Portland-cement concrete and recent green CPNC-concrete conclude main differences; the main important results are avoiding a large ratio of environmental pollution during the production and application of Portland-cement40, avoiding diseases caused by cement dust and preventing use of drinking water for the concrete construction industry, especially for countries with few water resources. Moreover, these results can minimize construction time and prevent steel corrosion due to the absence of water use. This solution will use green natural materials that do not cause pollution, it will use polymers that are inexpensive, and it may use recycled polymers to prevent millions of tons of polymers from entering the environment every year. Developed CPNC-concrete and construction materials have many other advantages in comparison to Portland-cement-based materials40, like ductility, avoiding sudden brittle failure and crushing, saving water-consumption, eliminating use of Portland-cement, eco-friendliness, and new applications.The dangerous environmental problems of Portland-cement industries affect human healthResults of testing and characterization for investigating mechanical and fracture properties, chemical composition, microstructure morphology, bond and homogeneity of CPNC-concrete and CPNC-mortar are illustrated in figures and tables followed by detailed discussion.Results are shown in Table Mechanical properties testing includes both of compressive Table  and tens15, as shown in Fig. Regarding tensile strength test, Fig. Regarding mechanical properties testing of HDPE and CPNC, Fig. 45. Some tested samples of CPNC-concrete are shown in Fig. 4a2, where no separation at cracked zone because there is no sudden failure or rapid crack propagation due to ductile behaviour. Figure 4a3, represents load‒displacement relationship for fracture properties test o under SENB, for pure HDPE (M40060) and CPNC, where Fig. Ic) and fracture energy Gf.Fracture properties test results of HDPE and CPNC are shown in Table Chemical composition elements are shown in Table Characterizations results by SEM are shown for MMT, HDPE, CPNC, CPNC-concrete and CPNC-mortar where Fig. ), Fig. ) between nanoclay layers due to mixing. Figure ) between nanoclay layers due to mixing, and Fig. ) between nanoclay layers due to mixing.Test results are shown in each of Fig. , based on ASTM, test of compressive strength is carried out for CPNC-mortar made of sand and MMT nanoclay/polymer nanocomposites where amounts of CPNC relative to sand are 5%, 10% and 15% of sand weight. Sand size passes through sieve #16; CPNC is made of HDPE and MMT with a ratio of 5% MMT nanoclay to HDPE. Table 12, BS13 codes and ASTM15 standards; there are large differences between newly developed materials and Portland-cement materials according to Fig. 2a2.Regarding mechanical properties17, testing machine is a German-made Toni Technik GmbH, Model 2091 with a maximum capacity of 300 kN, as shown in Fig. 17 standard for samples of diameter (D) = 10 cm and length (L) = 20 cm, as shown in Fig. 17. Comparison includes data in Tables Regarding tensile strength test, which is a splitting test based on ASTMIc), fracture energy (Gf), type of fracture and fracture mode, have been investigated for standard tests of notched beams under three-point loads, including pre-crack at bottom edge (single edge notch beam (SENB) tests). Results are shown in Table 45 or critical stress intensity factor KIc, as shown in Eqs. (c), half notch length (a) and beam geometry and dimensions:f is calculated based on ASTM41. Results are shown in Table 17. In addition, failure mode is ductile without splitting or brittle cracks. There is only deformation with very slight ductile longitudinal cracking at sides of cylinders; conventional Portland-cement concrete behaviour is sudden brittle failure at middle of cross section without ductile deformation. The ductile deformation converts cylinder circular cross-section diameter of D = 10 cm, to an elliptical cross-section with vertical minor axis of 9 cm and horizontal major axis of 11 cm, as shown in Fig. f depends on fracture toughness KIc, which depends on critical load, crack length, dimensions, and modulus of elasticity. Concrete structures have an essential demand for ductility to allow warning signs before cracking and failure to avoid sudden brittle failure. Therefore, recent CPNC-concrete is convenient for building construction since it has sufficient ductility. Results of KIc and cracking modes of tested samples under compressive and tensile strength show and prove ductility properties of CPNC-concrete. In addition, these cracks can be repaired easily by exposing cracked zone to local thermal effect to repair it without additional bonding materials. Fracture and crack propagation characteristics prove aim of developed CPNC-concrete where load‒displacement relationships exhibit elastic‒plastic shape, and deformation is ductile without sudden brittle failure or splitting, as shown in Fig. 17. Following basics of fracture mechanics science, ductile CPNC-concrete does not fail suddenly while brittle Portland-cement concrete fails suddenly, which does not have large deformation before failure; as in cases of ductile or brittle‒ductile materials.Fracture properties results indicate fracture toughness and fracture energy, and they prove ductility of CPNC concrete; these results show that there is no sudden failure, crushing or rapid crack propagation of tested sample. Fracture properties, including fracture toughness (K in Eqs.  and 3),,Ic), fra, EDAX analysis shows that NC is composed of Si, Al, and O, CPNC is composed of MMT nanoclay and HDPE polymer where MMT chemical elements are Si, Al, O and C, while HDPE contains C and O. Therefore, relative percentage ratios of CPNC chemical composition elements are 0.4, 0.23, 8.69, and 90.48 for Si, Al, O, and C, respectively. These ratios explain that MMT ratio is very small in comparison to HDPE, and verify concept of CPNC, which depends on reinforcing polymer matrix with exfoliated nanoclay platelets at a ratio of approximately 1–5%. EDAX analyses in Table Regarding Chemical composition using EDAX characterizationRegarding SEM characterization, microstructure and morphology characteristics of MMT, HDPE , CPNC, CPNC-mortar and CPNC-concrete using scanning electron microscope (SEM) are investigated where Fig. 34 for calculating d, while Eq. (5) represents Scherer’s law35 for calculating crystal size D.˚, the changes are d = 4.3–3.7 nm and D = 17.8–35.7 nm. Figure 35. The change in the crystal size proves the bond, which enhances the mechanical and fracture properties. The calculations of d and D depend on the values of angle θ and the peaks. The results of d and D, are estimated according to the Bragg equation34 and Sherrer's law36. The d distances of NC and CPNC change due to the exfoliation of the nanoclay layers and dispersion in the polymer matrix. Additionally, D is changed for NC and CPNC due to the processing of CPNC; both d and D almost do not change while processing thermally cast no-cement CPNC-concrete, verifying the stability of CPNC, which is the agent that produces the bond strength and other properties.Regarding XRD characterization; Fig. 11. Therefore, this research involves developing a new green material for use instead of Portland-cement. Concrete is a heterogeneous, brittle, heavy material containing coarse and fine aggregates bonded by Portland-cement powder with water17. Conventional concrete is composed of 45–60% Portland-cement, and the amount of water is approximately 50% the amount of Portland-cement; this finding indicates that conventional concrete contains a large volume of Portland-cement and consumes a large volume of potable water for mixing and curing. Moreover, the mixing and casting of conventional concrete requires a long period (28 days) for processing and hardening. Conventional concrete processing consumes an additional large volume of potable water for essential curing during processing to prevent shrinkage cracks. This material is very brittle due to the use of Portland-cement17. Therefore, conventional Portland-cement concrete suffers easily from brittle fracture, rapid crack propagation and sudden failure; in addition, conventional Portland-cement concrete causes steel corrosion due to water use and absorption. Usually, concrete structures contain steel bars for reinforcing the concrete material to resist tensile stresses. Steel bars always suffer from exposure to corrosion processes, which causes severe deterioration of the steel material, reduction in the steel tensile strength, de-bonding between steel and concrete, crack formation and failure. The main reason for the corrosion process is the presence of water. Portland-cement concrete depends mainly on water for processing and curing, which indicates that it is impossible to prevent corrosion of steel bars inside the conventional concrete element. Additionally, this material suffers from its high thermal conductivity, representing a contamination source, heavy weight, water use, difficult processing, long hardening time, and the need for special techniques and precautions in hot and cold weather. Portland-cement is not eco-friendly, harming the environment, human health, and economy11. The Portland-cement industry causes substantial environmental pollution, and cement dust has dangerous effects on human beings; cement dust causes serious diseases, such as cement eczema, lung cancer, skin burns, and chromate allergies11. Special storage conditions are needed to avoid deterioration of mechanical properties due to temperature change and humidity17.This research is carried out experimentally to develop and investigate new concrete and mortar materials free of Portland-cement and water; Portland-cement is replaced by a newly developed material called nanoclay-based polymer nanocomposite CPNC without using water for mixing. It is known that common conventional construction materials, such as concrete and mortar depend on the use of Portland-cement; however, these industries are dangerous sources of environmental contamination causing severe human health diseases, such as cancer40 by directly adding clay to Portland-cement. However, the present aim is different because previous researchers do not solve the problems of Portland-cement, but they encourage the use of Portland-cement and potable water. In this study, we aim to avoid Portland-cement use and reduce potable water use. Previous researchers have tried to add pure raw nanoclay particles to Portland-cement to produce conventional concrete mortar. The recommendations of concrete codes ACI12 and BS13 consider pure raw clay and silt as harmful substances that harm the mechanical properties of concrete causing debonding and cracks in concrete, making them prohibited materials in the concrete industry. Pure natural raw nanoclay particles are inorganic thermosetting hydrophilic materials in the form of sheets or nanotubes that absorb large amounts of water, causing harmful effects on concrete and steel if used as natural fillers; however, we convert them to another nanocomposite before using them in concrete. This study does not review the enhancement of Portland-cement mortar or concrete; instead, it aims to completely eliminate the use of Portland-cement. Some other researchers33 have looked for the enhancement of Portland-cement by using nanoclay; their research differs from code recommendations17, and it does not involve changing any negative effects of Portland-cement or replacing the material. For these reasons, raw nanoclay cannot be used in its natural shape as an inorganic agglomerated particle to enhance Portland-cement. Nanoclay particles should be covered with organic surfactant materials, such as octadecylamine, to modify particle surfaces into organic-like host materials to produce bonds between the coated clay particles and polymers, producing CPNC; CPNC includes nanoclay as a reinforcement for the polymer, which is a bonding agent, instead of Portland-cement. The processing method is a thermal casting process without using water for producing CPNC–concrete and CPNC–mortar; it avoids problems with Portland-cement while achieving new important properties. The developed material overcomes the problems of conventional concrete, which depends on a green natural nanocomposite-clay-based polymer nanocomposite (CPNC)-composed of a small ratio of exfoliated nanoclay of approximately 5% NC mixed with 95% high-density polyethylene (HDPE) processed through an extruder by melting synthesis. This research represents one of the new applications of nanocomposites made of natural green nanoclay particles and polymers; nanoclay platelets are used as reinforcement fillers to change and enhance the properties of the polymer matrix. Due to the unique properties of natural nanoclay platelets, such as very large surface areas and other thermal and mechanical properties, they enhance the thermal, mechanical, and fracture properties of polymers, transforming the polymers into sustainable nanocomposites resisting degradation, retarding fire, resisting heat, enhancing tensile and compressive strengths, and changing the mechanical behaviour and failure modes. Due to previous studies from us and of other researchers44, it is found that the best ratio of MMT to enhance the polymer properties producing CPNC is 5%. Researchers studying CPNC made of MMT nanoclay and polymers have usually tried to use several ratios between 1% MMT, 3% MMT, 5% MMT, and 10% MMT nanoclay, where they prove that 5% nanoclay is the best; if the amount of nanoclay exceeds 5%, it may enhance thermal properties but deteriorate the material mechanical properties. Therefore, we use a ratio of 5% CPNC to obtain good results and avoid concrete deterioration simultaneously. However, the idea of the research is new, and there are no similar CPNC-concrete or CPNC-mortar materials with zero Portland-cement or zero water made by the thermal casting technique utilized in our current study or by any other technique. Our study involves newly developed materials with new techniques. Therefore, there are no previous information or data regarding the mix design of the CPNC ratio44. Therefore, we use three percentage ratios of 5%, 10% and 15% CPNC to investigate whether the ratio of 15% represents the best ratio. The results indicate that the best global ratio of nanoclay particles embedded in the CPNC-concrete is (5% MMT)*(15% CPNC) = 0.75% MMT nanoclay. When using 10% CPNC, the MMT ratio is 0.5% of the total volume of concrete; for 5% CPNC, the MMT ratio is 0.25% of the concrete volume. Therefore, we cannot increase the ratio to more than 15% CPNC to avoid deterioration of the concrete; the other ratios of 5% and 10% have good results but are still not better than the 15% ratio. MMT nanoclay is expensive, and CPNC-concrete is inexpensive relative to the benefits. However, conventional Portland-cement design codes, such as ACI12, consider pure raw clay particles to be harmful substances for concrete; the harmful effects are increased by the 1% ratio. Although our nanoclay is not pure raw, it is still in the range of the allowable ratio of concrete design codes. In addition, since our new material is different from Portland-cement concrete for all sides, it needs special design codes. CPNC is a fine powder with special mechanical and thermal properties that enhance concrete and mortar properties. CPNC is a ductile material that reduces cracking, is thermally resistant, has good mechanical properties, and increases toughness and fracture energy. In this research, we develop CPNC–mortar and CPNC–concrete without Portland-cement or water using small dry ratios  of CPNC mixed with sand or sand and crushed stone, respectively. After dry mixing in special moulds, thermal melting synthesis is applied in electric ovens at 220–250 °C. The produced thermal casting CPNC-concrete is a homogenous, lightweight, low-density, self-compact, and ductile material without pollution. This material is a rapidly processed concrete without fracture, crushing or sudden failure. The study includes material synthesis, mechanical and fracture property testing, and characterizations of chemical components, microstructures and crystallography using SEM, EDAX and XRD. The results are suitable for an eco-friendly construction industry. Using CPNC as a bonding agent instead of Portland-cement reduces environmental pollution and potable water use, where CPNC-concrete contains 5–15% CPNC to produce CPNC-concrete within approximately three hours. Portland-cement concrete is not thermally resistant; CPNC–concrete is suitable for building insulation because it contains CPNC, which is thermally resistant.Some researchers have tried to enhance the properties of conventional Portland-cement18. While this material exhibits other properties, such as tensile strength and shear strength, Portland-cement is a very dangerous material11. The Portland-cement industry produces high-levels of CO2 pollution and consumes a large amount of oil and gas, additionally generating substantial amounts of cement dust and harming humans, animals, and plants. Moreover, Portland-cement is very easily affected by water vapour or humidity, and it requires special methods and buildings for storage. Portland-cement needs a lot of water for mixing with aggregates to produce enough bonding; it takes a long time and requires a special curing process involving water for almost one month. Hot climates or cold climates need very special techniques and durations for mixing and hardening. The material resists brittle fracture, sudden failure and crushing because of its ductility. The concrete undergoes fast processing, developing strength rapidly in a few hours. The material does not need water curing as in the case of conventional Portland-cement. The concrete may consist of coarse aggregate , fine aggregate (sand) and CPNC instead of Portland-cement. Additionally, this material can be made of only fine aggregate and a nanocomposite-based mortar. The ratio of coarse aggregate to fine aggregate is 2:1, but it may change according to the required material properties, such as strength. The nanocomposite is a CPNC that consists of a polymer matrix reinforced with nanoplatelets of MMT montmorillonite nanoclay or nanotubes, such as halloysite. The ratio of the CPNC to the aggregate changes between 5, 10, and 15% according to the weight, which controls the strength of the concrete. The CPNC ratio controls the density, porosity and specific weight of the concrete. For mix design, fine aggregate, and dry powder CPNC should be mixed first until homogeneity for approximately 5–10 min; then, it is mixed with coarse aggregates for approximately 5–10 min until it is homogenous. In this study, we include the steps of material preparation, moulding, mixing, casting, heat processing in ovens, cooling, removing the moulds, preparing the samples for testing, testing , and characterization using XRD, EDX and SEM, analysis of the results, discussion, and conclusion. CPNC is prepared first by using a twin screw extruder and pelletizer to produce a nanoclay–polymer nanocomposite (CPNC) powder reinforced by nanoclay platelets or nanotubes. CPNC dry powder is mixed with aggregates covering all aggregate particles; then it is melted by heating, melting all aggregate particles, and generating bond strength. After cooling, a high interfacial bond is achieved without fractures or cracks, producing highly ductile, self-compact, no-cement, and no-water CPNC concrete. The temperature is not less than 220 °C. The temperature and heating time control the strength of the concrete; the temperature must not be less than the melting point of the CPNC. The concrete is compacted by self-compaction under the weight of the aggregates. The microstructure and particle arrangement depend on the temperature and CPNC ratio. The casting method does not allow the possibilities of cracking or fracture. The density of CPNC concrete is 1.5–1.8 g/cm3, while the density of conventional Portland-cement concrete is 2.2–2.5 g/cm3. The aim of manufacturing the newly developed concrete is to produce green ductile concrete with functional properties, such as ductility, eco-friendliness, light weight, fracture resistance, thermal resistance, crushing resistance, corrosion resistance, self-compaction, high homogeneity, rapid hardening, high strength, reduced pollution, sudden failure resistance, without Portland-cement or curing and through a dry mixing process. This material can be applied for all construction and structural purposes, especially in arid and semiarid areas. The concrete requires a special type of casting. CPNC is reinforced with NC. Figure 3; the coarse aggregate is washed crushed stone with a particle size less than 4.75 mm and a density equal to 2570 kg/m3. However, the Portland-cement density is 2250 kg/m3, while the nanoclay density is 260 kg/m3 and the HDPE density is 980 kg/m3. The density differences between nanoclay and polymer relative to Portland-cement and aggregates are clear.The concept of the research is to produce green concrete that is suitable for construction by reducing the problems of conventional Portland-cement concrete, as shown in Fig. ) or only fine aggregate and nanocomposite (no coarse aggregate). The ratio of coarse aggregate to fine aggregate is 2:1, but it may be changed according to the required strengths and properties. The nanocomposite is a clay-based polymer nanocomposite CPNC that consists of a polymer matrix reinforced with nanoplatelets of MMT nanoclay or nanotubes. The ratio of the CPNC to the aggregate changes to 5%, 10%, and 15%, depending on the weight. The CPNC ratio controls the strength of the concrete. The CPNC ratio controls the density, porosity, and specific weight of the concrete. For mix design, fine aggregate, and dry powder CPNC should first be mixed until homogeneity for approximately 5–10 min and then mixed until homogeneity with coarse aggregates for approximately 5–10 min. The CPNC may be mixed in a hot mixer under various temperatures, depending on the melting point of the CPNC; the melting point changes based on the type of polymeric nanoclay composite. Then, the CPNC is cast in suitable moulds, where it is cooled normally. After a few hours, it is cooled and achieves the required strength without the need for curing. The coated moulds by aluminium, plastic or CPNC sheets are removed. Another method of casting involves casting the dry concrete mix in the moulds and microwave or oven heating the moulds for separate precast concrete elements. The temperature is at least 220 °C. The temperature and heating time control the strength of the concrete. The concrete is compacted by self-compaction under the weight of the aggregates. The microstructure and particle arrangement depend on the temperature and CPNC ratio. The Portland-cement industry produces a ratio of contamination of approximately 8% of CO2 pollution, which is a high ratio due to the industry being a single industrial product11. As basic data based on worldwide codes, concrete materials contain aggregates, Portland-cement, and water18. Aggregates of sand, gravel and crushed stones should always be clean particles and free of harmful substances15. Portland-cement under good storage conditions is a dry fine powder. Clean potable water is essential for mixing with cement15. The design of the concrete mix contains a cement content ratio equal to (0.35–0.6) with respect to the total unit volume of 1.0 m3. The ratio of cement content depends on the required compressive strength of concrete, where increasing the cement content ratio will increase compressive strength and vice versa. Moreover, the water content is a ratio of the cement content, where the average water content ratio is approximately (0.35–0.60) with respect to cement content. Water is essential not only for cement hydration but also for concrete curing, which is potable or distilled water15. This volume of water is very large with respect to the required volume of concrete for the construction of any structure, such as a building, bridge or dam. Water specifications are very restricted for containing any undesired substance that may harm the cement bond to aggregates, compressive strength, and cause steel corrosion15. More water is still needed for concrete curing15 for obtaining the maximum compressive strength after 28 days of casting. On the other hand, water is very rare in arid and semiarid areas, while underground water and sea water are not allowed for the concrete industry because of the presence of high ratios of chlorides and sulfates15. Therefore, the current research aims to save water in addition to avoiding Portland-cement contamination.Regarding testing and characterizations, testing includes mechanical and fracture properties, while characterization includes microstructure, interfacial bond, homogeneity, particle distribution using SEM, chemical composition using EDAX and crystallography, and changes in particle dimensions and distributions by XRD. The newly developed material is a thermally cast, no-cement, no-water, low-density, self-compact, ductile, corrosion resistant, brittle fracture resistant, functional, and green nanocomposite concrete. A new concrete material is fundamentally developed, tested and characterized. This material is made of aggregates and nanocomposite materials without cement or water. The material resists fracture, sudden failure and crushing. The casting technique depends on new technology using thermal casting through heating by microwaves or normal ovens or mixing under heating by thermal mixers. The concrete is quickly processed in a few hours to have a high strength; the processing time depends on the size and required type of concrete. This material does not require curing; it resists and retards fire. This CPNC-concrete can resist dynamic loads since it is ductile. The material has a high fracture toughness, fracture energy and strength without additional additives; it is thermally resistant, and controls heat transfer due to the use of thermally resistant CPNC. This material consists of aggregates and nanocomposites. The aggregate may consist of coarse  and fine (sand) aggregates. Additionally, the aggregate can be made of only coarse aggregate and nanocomposite , HDPE (M40060) and CPNC are shown in Table Materials include montmorillonite (MMT) nanoclay (NC), high density polyethylene (HDPE) for producing clay-based polymer nanocomposites (CPNC) and aggregates for producing mortar and concrete by using CPNC instead of Portland-cement. Aggregates are fine and coarse; the fine aggregate is washed sand of sizes less than 1.18 mm with densities of 2500 kg/mi is individual sample result, μ is mean value, and N is total number of samples.The instruments include a computerized extruding and mixing system for producing CPNC powder, including a laboratory station, twin screw extruder model , water bath, HDPE feeder, NC feeder and high-speed pelletizer. Other instruments are used to produce no-cement and no-water concrete, including mixers, ovens, and standard moulds for cylinders, cubes, and prisms. There is a testing machine for mechanical and fracture toughness testing, including a universal displacement control machine, for testing specimens of cubes and cylinders for compressive and tensile strengths and for testing the fracture properties of beams. The characterization instruments include a scanning electron microscope for SEM and EDAX and an X-ray machine. Testing samples include standard cylinders of dimensions (75 mm diameter and 150 mm height or 100 mm diameter and 200 mm height), standard cubes to mortar test dimensions (50*50*50 mm) and beams for testing fracture properties. The experimental work has three main phases: the first phase includes producing the CPNC, the second phase includes producing zero-cement CPNC-mortar, and the third phase includes producing zero-cement CPNC-concrete. Each phase includes the testing of mechanical properties and fracture properties in addition to EDAX, SEM, and XRD characterization processes, as shown in the associated tables and figures. Mechanical and fracture properties are determined in KSU laboratories at room temperature (21 °C) using a universal testing displacement control machine at a displacement rate of 0.2 mm/min. The components of newly developed clay-based nanocomposite concrete contain aggregates of fine particles, coarse particles, or both with CPNC. CPNC produces bonds between aggregate particles without Portland-cement or water on any other chemical additives. CPNC is a green material with good mechanical and fracture properties in powder, pellet, thread, rod, or sheet shapes. CPNC is a dry powder for producing CPNC-concrete. Additionally, the material can be used as pellets for producing concrete nanocomposites; however, fine powder is very important for homogeneity purposes. CPNC is added to the aggregate at a ratio of 5%, 10%, and 15% by weight; the mechanical and fracture properties and self-compaction ratio depend on the CPNC ratio in the concrete mix. Increasing the CPNC ratio increases the self-compaction ratio and the density. Therefore, the density, compressive strength, mechanical properties and fracture properties are controllable. The most important characteristic of CPNC concrete is ductile behaviour. Special mould preparation coted internally with thin sheets of aluminium is needed to facilitate sample removal from the moulds. Figure 30, and it is based on the melting point of HDPE. The system extrudes and produces CPNC as a raw powder material by adding dry NC powder to dry HDPE pellets in a twin screw extruder under the thermal effect of 250 °C; the powder undergoes a high shear extruding process to exfoliate and disperse MMT particles in the polymer chains. Before and during this process, the vacuum works to prevent any possibility of producing voids, gases, air bulbs or defects in the product. Then, the powder goes to the exit zone (die) to produce rods or threads. Then, the material passes through a cold-water basin at a suitable speed for cooling the rods. Then, the material passes inside a granulator with speed control to convert the rods into powders or pellets and collect them in a container. This process produces the required CPNC powder; additionally, it can be repeated several times to produce the required CPNC. Then, CPNC powder is added to the aggregates to start the processing of non-Portland-cement concrete. Both the mechanical and fracture properties of CPNC are investigated based on the standards of ASTM (D 638)16 and ASTM (D 5045)17. The results are shown in Table The first phase of experimental work is conducted to develop a CPNC bonding agent instead of Portland-cement. The agent consists of 95% pure HDPE M40060, reinforced by 5% MMT NC nanomer I.30T) synthesized by melt processing using a well-computerized and well-controlled high shear twin screw extruding system. CPNC is produced in a powder shape to be mixed with sand and crushed stones. The properties of the MMT nanoclay, HDPE polymer and CPNC are shown in Table 0T synthe18. The CPNC powder is produced in our nanoclay laboratory through a melt processing technique by using a commercial surface-modified MMT nanoclay: I.30T nanomer. CPNC mortar is synthesized by thermal casting and melting processing using electric ovens and cubic moulds of 5 × 5 × 5 cm3 and beams of 4 × 4 × 16 cm3 coated internally with thin aluminium sheets. CPNC concrete consists of CPNC powder and a mix of sand and crushed stones with a sand/crushed stone ratio of 1:2. CPNC–concrete is synthesized by a melt processing technique. The tested samples are cylinders that are tested for compressive and tensile strengths with standard dimensions of diameters of 7.5 and 10 cm and heights of 15 and 20 cm; the cylinder moulds are internally coated with thin aluminium sheets to facilitate sample removal. Other beam samples of standard dimensions (4 × 4 × 16 cm) made in internally coated moulds with thin aluminium sheets are prepared for fracture property testing. All samples are synthesized thermally at 250 °C using electric ovens. The first step of processing is mixing 5% CPNC dry powder with 95% dry washed sand for 5–10 min through a high shear mixer. The time of mixing is an important variable for a good homogeneous distribution of the composite for conventional concrete made of Portland-cement or for any composite based on Portland-cement and water; in our research, time is a very important difference between our newly developed material and conventional Portland-cement composites. This important difference occurs for several reasons. We are not using raw nanoclay or Portland-cement. Our materials include sand, crushed stones and CPNC powder. All of the sand, crushed stones and CPNC powder materials are dry, hydrophobic and cohesionless particles that are not sticky and can easily be distributed and mixed. Nanoclay particles in our material are not added to sand and crushed stone as natural raw nanoclay; instead, they are already embedded in the polymer matrix to be applied as cohesionless CPNC particles. Therefore, there is no cohesion between particles during mixing, which may prevent homogenous distribution during the mixing process without the need for a long duration; instead, the material requires a very short mixing time. For Portland-cement composites and natural nanoclay, both agglomerated particles and cohesive material absorb water easily from the surrounding atmosphere because both are hydrophilic. This hydrophilicity makes mixing natural nanoclay or Portland-cement with other materials very difficult and nonhomogeneous; this characteristic indicates that the materials require water to facilitate mixing and distribution. Therefore, the uniformity levels of the distributions of Portland-cement or pure natural nanoclay to any other material are very difficult and may be impossible to be homogenous and uniform; in our case, it is very easy to mix the materials with very high uniformity and homogeneity, as seen in the cross sections of the cylinders in the manuscript. Moreover, nanoclay particles are always agglomerated at the microscale; this agglomeration is impossible at the nanoscale if the particles are directly mixed with Portland-cement or any other material, such as sand or crushed stones, even if water is used in the mix. Nanoclay can only be at the nanoscale if the agglomerated nanoclay particles are exposed to the effects of high shear, such as when using a powerful twin screw extruder, as in our study, or when using similar devices, such as tows and three roll mills, several times. Otherwise, the MMT clay particles still agglomerate at the microscale or larger, which does not produce nanocomposites. In addition, nanoclay requires a very large amount of water and a very long time to mix until it is on the nanoscale. This aspect is the actual challenge, and its study has generated competition between researchers and companies working in the field of clay-based nanocomposites, especially for MMT nanoclay; mixing may be easier for clay nanotubes, such as halloysite nanoclay, due to the high bonding between layers of MMT nanoclay. The only difficulty in the mixing process is during the manufacturing of CPNC using the extruding system. Then, the admixture is installed in cylinders, cubes and beams that are already internally coated with thin aluminium sheets to facilitate specimen removal after synthesis. Then, cylinders, cubes and beams are installed in the oven at 220–250 °C. It is better to turn the oven on before installing the samples until the temperature increases to the required 220–250 °C. The samples are left in the oven for approximately 30 min for the small cubes, and this process continues for other cylinder and beam samples for approximately three hours. As a precaution for compaction, the mould height must be increased for each cylinder by an additional 2.0 cm and for each cube and beam by an additional 1.0 cm; the mould height increase is achieved by increasing the height of the aluminium sheets because during melting, the CPNC concrete and CPNC mortar are self-compacted, reducing the height of the samples by a small amount. The same procedures are made for the beams (prisms) for mechanical and fracture property testing. For the beam samples undergoing fracture property testing, small notches with maximum lengths of approximately 2.0 cm are made at the middle of the bottoms of the beams for testing under the 3-point load SNB based on the ASTM standard17; other samples are tested under the same conditions of three-point loads without notches to investigate the maximum critical load of the tested beams of zero-Portland-cement. The results are shown in Tables 3, which is suitable for applications in all fields of civil and construction engineering.The materials are shown in Table 17. The tested specimens are cylinders, beams, and cubes. The cylinders are tested under compressive loads based on the ASTM standard test to investigate the compressive and tensile strengths of CPNC concrete; cubes are tested to check the compressive strength of CPNC mortar. Additionally, the material ductility, stress‒strain relationship and modulus of elasticity are evaluated. The beams (standard prisms) of both CPNC concrete and CPNC–mortar are tested to check the fracture properties, including fracture toughness and energy. In addition, a water absorption test is carried out based on ASTM, showing that the CPNC mortar does not absorb any considerable water amount after measuring the cube weight before and after immersing the cubes in water at room temperature. The tested samples and results are shown in Fig. The mechanical and fracture properties and the water absorption characteristics of CPNC mortar and CPNC concrete samples are tested based on ASTM17. The results of the tested beams for fracture properties are indicated in Table Ic) and fracture energy (Gf) for both beams made of CPNC mortar (sand + CPNC) and CPNC concrete (coarse aggregate + sand and CPNC with different ratios of CPNC). The test results are in Table The main mechanical properties have been investigated using a standard compression test since the main important mechanical property of the concrete is the compressive strength. The mechanical property testing includes compressive strength, load‒displacement relation, ductility, failure modes, and deformation shape. The fracture mechanics test results for fracture properties include fracture toughness, and fracture energy. The tested samples and test setup are shown in Fig. The mechanical properties are investigated through standard tests of cubes and cylinders; standard pre-cracked beams are tested to investigate fracture properties. Newly developed CPNC concrete involves a special processing technique for casting with new factors of compaction, bonding, compressive strength, tensile strength, specific-weight, Young's modulus, ductility and fracture properties; these parameters depend on the properties of the components, ratio, particle size, thermal properties and melting point. An increase in CPNC ratio controls compaction ratio, compressive and tensile strengths, ductility, concrete weight, modulus of elasticity, fracture toughness and fracture energy. An increase in the CPNC ratio increases compaction ratio and vice versa; compressive strength increases due to an increase in CPNC ratio from high bonding between aggregate particles and CPNC particles, which are reinforced polymers with nanoclay particles covering aggregate and sand particles. A change in heights of cubes or cylinders after thermal processing indicates a self-compaction ratio and changes in density and ductility. An increase in CPNC increases the ductility. Self-compaction is developed due to the melting of the CPNC and self-sedimentation of aggregate particles in the melted CPNC matrix based on the ratio of the melted CPNC viscosity concentration to the aggregate particle weight under gravity. Therefore, size and weight values of aggregate particles are very important factors for ductility, strength, E, and mechanical properties of no-cement CPNC-concrete. While conventional concrete requires curing with water for 28 days after casting, the recently developed CPNC-concrete does require any curing or water. For sample preparation, moulds of cubes and cylinders are prepared with a special method based on the thermal casting mechanism and the concrete mix behaviour; the moulds are compacted during heating. The moulds have reduced the heights, but they need their pre-excess heights to match the standard dimensions of cubes and cylinders after compaction. Since it is impossible to increase the height during heating, it is important to increase the heights of the cubes, cylinders and other types of moulds before casting with the expected ratio of height decrease to obtain the required standard height after thermal casting. Height of the sample decreases due to compaction and increases in other mould dimensions; these changes occur due to thermal expansion of the moulds. After cooling the moulds, increase in the mould dimension due to expansion is decreased once again, producing lateral pressure on the samples; this process represents self-prestressing, increasing the compressive strengths and the mechanical and fracture properties of the concrete samples.Ic) and fracture energy (Gf). This section is important for this study. The designer of concrete structures is always aware of cracks for safe design without fracture, cracking or failure and for a sustainable and safe lifetime; Portland-cement concrete is very brittle with easy possible fracture, rapid crack propagation and sudden failure. Therefore, it is necessary to study the fracture properties that control the design to prevent cracks by investigating the main intrinsic parameters of fracture toughness KIc at crack tips, and the critical fracture energy Gf. Based on the ASTM standard test for fracture toughness, experimental work is carried out for CPNC-concrete and CPNC-mortar samples.The fracture properties include fracture toughness  and the spacing (d) between atom layers according to Bragg’s law35 and Sherrer's law36 to determine the changes in distances between the crystal atomic surface (d) and the particle size before and after processing and the changes in the interfacial bonds between different components and homogeneity; the findings prove the achievement of other properties, such as the mechanical and fracture properties.The crystallography of the newly developed thermally cast, no-cement, no-water CPNC-mortar and CPNC-concrete materials and their components have been characterized by the technique of X-ray diffraction (XRD) based on Bragg's law30. CPNC concrete is evaluated based on the ACI code and ASTM C 140 to check the water absorption ratio17. The absorbing water ratio is zero (0.0%), proving that CPNC-concrete is a hydrophobic material due to use of CPNC; Portland-cement concrete17 is a hydrophilic material that absorbs water. Therefore, CPNC-concrete cannot cause steel corrosion. It has important properties relative to conventional Portland-cement concrete, as shown in Table Regarding comparing between CPNC-concrete and conventional concrete; CPNC-concrete is a suitable construction material for all types of buildings and infrastructures, including roads and highways, especially in arid and semiarid areas; it does need water for synthesis or curing, and it can be used as a thermal insulator because it contains clay-based polymer nanocomposites, which are thermally resistant and fire retarding functional nanomaterials. In reinforced CPNC-concrete elements CPNC can cover the reinforcement steel, producing high interfacial bonding with concrete and protecting steel reinforcement from corrosion. CPNC-concrete is convenient for 3-D printed structures, especially in areas with few water resources. Finally, CPNC-concrete can resist the spread of diseases due to Portland-cement industry and applications. New special methods of design and construction, special codes are needed for these new materials. It will become a feasible material for future construction projects.Newly developed eco-friendly green CPNC-concrete and CPNC-mortar are thermally cast, zero-Portland-cement, zero-water mixing, no-crushing, no-brittle fracture, no-water-curing, self-compact, lightweight, low-density, ductile, rapidly processed, rapidly strengthened, and homogenous materials without pores or cavities. These are made of aggregates and nanoclay–polymer nanocomposite (CPNC). CPNC is made of reinforced polymers with nanoclay platelets, such as MMT and halloysite nanotubes. CPNC-concrete is ductile material resists cracking and does not suffer from crushing, sudden brittle failure, or shrinkage cracks. CPNC-concrete has good mechanical and fracture properties. It has good interfacial bonding between CPNC and aggregates, which enhances mechanical and fracture properties. The moulds of developed thermal-casting CPNC-concrete are special metallic moulds with internal removable thermal insulation lining of a very thin layer of aluminium sheets. It has no aggregate-segregation or bleeding as in cases of Portland-cement concrete. It is thermally resistant since it is made of thermally resistant CPNC that are suitable for arid areas. It does not need water; water is rare in arid areas. It is hydrophobic material since it does not absorb wate. It can reduce energy consumption for buildings since it contains CPNC, which is a fire retarding and thermal resistant material that can act as a building thermal insulator for controlling energy transmission. It is rapidly processing with quickly developing strength that does not need as long a time for synthesizing as Portland-cement concrete; Portland-cement concrete needs 28 days to reach 80% of its strength. Moreover, it is economical since it eliminates Portland-cement and water consumption and can use recycled polymer and natural clay


Salt-scaling resistance in the presence of recycled concrete aggregatesA strong bond between RCAs and new mortar was obtained after a freeze-thaw testPulse velocity after exposure to freezing-thawing cycles negligibly decreasedThe scaling rate increased with the increase in the water–cement ratioThe electrical resistivity of concrete after exposure to cycles has been investigatedConcrete wastes such as recycled concrete aggregates (RCA) make up a significant part of construction and demolition waste (C&DW) which can be used to minimize usage of natural aggregates and reduce carbon footprint. This paper studies the salt-scaling resistance of recycled aggregate concrete produced with pretreated RCAs. The test method for evaluating salt-scaling resistance in concrete according to DIN EN 1340: 2003 was performed. Four series of concrete mixes using natural aggregates, RCAs, manually pretreated RCA, and modified RCA in a desiccator were subjected to the different tests in terms of bulk electrical resistance in two directions (X and Y) before and after freeze-thaw cycles, ultrasonic pulse velocity, and weight loss of the surface layer of concrete specimens. Moreover, Scanning Electron Microscopy (SEM) of mixes was conducted and the microstructure of mixes considering the interface transition zone was studied. Results show that after exposure to cycles of freezing and thawing, the quality of concrete regarding ultrasonic pulse velocity did not change. The electrical resistance of specimens decreased significantly in X-direction and slightly in Y-direction after applying freeze-thaw cycles in all mixes. Nevertheless, surface modification of RCAs can increase electrical resistance and improve durability of concrete. SEM images show that the interface transition zone before and after freeze-thaw cycles remained unchanged which means strong bond between aggregate, new mortar, and old mortar. An estimation of the total charge passed indicated that all recycled aggregate concretes can be classified in a safe area and with very low chloride ion penetrability according to ASTM C1202. Marvila et al. [In concrete structures, after the mechanical performance, it is necessary to evaluate the durability of concrete. For instance; ion chloride penetration, alkali aggregate reaction, sulfate attack, freeze-thaw damage, salt scaling, to name a few, which are the major concerns for concrete structure ,2. Frosta et al. , reportea et al. .It is expected that more levels of damage consisting of more cracks, greater mass loss, surface scaling, and spalling occur whereas RCAs are incorporated in concrete mixes culminating in further penetration of aggressive agents  ,11. AlthAlthough the concise state-of-the-art review presented in the literature indicated that there have been a wide range of studies related to recycled aggregate concrete (RAC) performance, whether the treated RCAs can affect the durability performance of concrete in extreme climate events and hostile environments is unknown for sure. As only a limited number of technical papers related to the topic of the current manuscript can be found in the literature, the investigation of recycled aggregate concrete’s performance subjected to freeze-thaw cycles in the presence of deicing salts seems to be worthwhile . In addition, due to the significant heterogeneity of recycled concrete aggregates derived from different origin concrete, the amount of attached mortar, and other negative characteristics of RCA, durability aspects of concretes made with recycled concrete aggregates (RCAs) must be considered before any practical applications .Using treatment methods for enhancing properties of RCAs is an advantage to mitigate the challenges of concrete mixes casting with RCAs. There are found to be several methods for improving by many scholars conducted to date, the most important of which are (1) strengthening of attached mortar (AM) and (2) removing of AM . A revieSpecifically, this paper deals with the salt-scaling resistance of high-strength concretes consisting of conventional concrete (C60-C75) prepared with natural aggregates and recycled aggregate concretes (C50-C60) produced with RCAs which are untreated and treated by silica fume slurry around RCA’s surfaces. To this end, two surface modification methods to treat the surface of RCAs employed herein were considered with the aim to investigate the effect of the modification method on the salt-scaling resistance of mixes.Portland cement type Ⅱ and silica fume (SF) as supplementary cementitious materials and also for coating the surface of RCAs were used in this study. Properties of cement and silica fume are given in To provide convenient workability, a chemical admixture based on ether polycarboxylate was used and the quantity of superplasticizer was kept  which helps to eliminate the effect of chemical admixture on the durability characteristic of mixes.Recycled concrete aggregates were modified to strengthen adhered mortar on the aggregates. Two modification methods were considered in which silica fume slurry including 250 gr SF and 1000 cc water added to 8 kg of RCA. In the first method called RACCM, RCAs are coated by SF slurry manually. The RCAs were poured into SF slurry and the coated aggregates were transferred to the oven and dried for 72 h at 45 °C. For the second modification method called RACCD (Coated in Desiccator) to be used in mixes, RCAs were poured in a desiccator in a dry manner for 2 h and then SF slurry was added to the desiccator to seal the surface of RCAs in the desiccator for one hour. After which, RCAs were transferred to an oven-dried machine, the same as the RACCM method.This study aims to investigate the effect of deicing salts in freeze-thaw cycles on four series of mixes including normal concrete, recycled concrete with untreated aggregates, and two series of recycled concretes using pretreated RCAs in which the absolute volume method for concrete mix design was employed. Coarse RCAs with replacement of 100% were prepared in a laboratory using a small rock crushing machine. To separate impurities from the surface of RCAs, they were presoaked in water before mixing in concretes containing untreated recycled concrete aggregates. Freeze-thaw tests according to DIN EN 1340: 2003  were conTo measure the pulse velocity of samples before and after the freeze-thaw test, a portable ultrasonic non-destructive digital indicating tester (PUNDIT) was used. The bulk electrical resistance of mixes was conducted on specimens used in the freeze-thaw test before and after applying 28 cycles. The blue vectors in 2) from the surface of specimens after exposure to freeze-thaw cycles in the present of deicer salt can be found in The cumulative mass of scaled-off particles  values of concretes at 28, 91, 271 (before applying cycles), and 299 days (after exposure to cycles of freezing and thawing in X- and Y-direction) are shown in Turning to the details of bulk electrical resistance, results in Y-direction depict that all mixes resist against ion movement. However, a slight reduction of ER can be seen in mixes ranging 2–10% in normal concrete, 9.5–15% in the RAC group, 6–9% in RACCM, and 3–13% in the RACCD group. Decreasing in degree of saturation of the matrix and also other components of concrete such as aggregates, the electrical resistivity of the complex increases; “this is due to the reduction in resistivity of the pore solution (the conductive medium) and increase in tortuosity” .Very Low CIP classification of ASTM C1202 [According to the last investigation , authorscted See . As illuTM C1202 .In this paper deicer salt-scaling resistance of recycled aggregate concrete was evaluated. Concrete mixtures were prepared with natural aggregates, untreated RCAs, and pretreated RCAs. To strengthen adhered mortar on the surface of RCAs, silica fume slurry was used. The following results were derived.The data presented herein demonstrated that in the presence of deicing salts, recycled aggregate concrete is not resistant to scaling. However, it would be possible to utilize pretreated RCAs in applications exposed to freeze-thaw cycles providing a protective layer of conventional concrete on top of which recycled aggregate concrete is cast.After exposure to cycles of freezing and thawing, electrical resistivity of mixes decreased sharply in X-direction. The main reason for electrical resistivity reduction is ionic concentration on the surface of specimens in the presence of NaCl which facilitates ion movements. Electrical resistivity in Y-direction decreased after applying cycles in mixes containing RCAs which can be associates with frost damages of concrete under abrupt temperature changes. However, surface modification of recycled aggregate can assist in improving the electrical resistivity which means a beneficial effect on durability in terms of corrosion. Estimation of total charge passed of mixes after exposure to cycles indicated that pretreated recycled aggregates can resist against ion movements. The chloride ion penetrability remains in a safe area according to ASTM C1202. The ultrasound pulse velocity of recycled aggregate concrete after exposure to cycles of freezing and thawing can be classified in the excellent category in terms of ultrasonic response. The presence of RCAs did not follow a negative effect on the interface transition zone of specimens after exposure to cycles which means RCAs exhibited a strong bond with new mortar. However, some cracks on the surface of adhered mortar resulting from abrupt temperature changes can be found.


Nanocomposites of methacrylate-based polyhedral oligomeric silsesquioxane (POSS) are used as resins in dentistry to fill dental cavities. In this article, molecular dynamics simulations (MDS) are used to study and understand the interactions of monofunctional and multifunctional methacrylate groups on hybrid resins containing POSS additives for dental applications. These interactions are further related to the structural properties of the nanocomposites, which in turn affect their macro-properties that are important, especially when used for specific uses such as dental resins. For monofunctional methacrylate, nanocomposite of methacryl isobutyl POSS (MIPOSS) and for multifunctional methacrylate, methacryl POSS (MAPOSS) are used in this study. Molecular dynamic simulations (MDS) are performed on both MIPOSS and MAPOSS systems by varying the amount of POSS. On a weight percent basis, 1%, 3%, 5%, and 10% POSS are added to the resin. Density calculations, stress–strain, and powder diffraction simulations are used to evaluate the macro-properties of these nanocomposites and compare them with the experimental findings reported in the literature. The observations from the simulation results when compared to the experimental results show that MDS can be efficiently used to design, analyze, and simulate new nanocomposites of POSS. These organic functional groups in POSS can be reactive or nonreactive which makes them useful in a wide range of applications. With the nonreactive R, they become soluble and compatible with other polymers, while with reactive R, they are amenable for use in grafting and polymerization reactions. Further, when R constitutes only one reactive group , POSS can be incorporated as a pendant in a network while if R has more than two reactive groups , POSS can be used as a crosslinking point. The inorganic core of POSS improves rigidity and stability while the organic functional groups affect flexibility, ductility, and processability when mixed with other materials. POSS with specific mono and multifunctional reactive groups are used as modifiers and crosslinkers in several polymer matrices targeted for improved mechanical, viscoelastic, barrier, and thermal properties. POSS has been a primary choice for synthesizing high-performance materials as it combines the benefits of organic and inorganic material characteristics. POSS is widely used in plastic additives, fluorinated superhydrophobic coatings, nanofiber membranes, electronics and energy applications, and biomedical applications [Search for novel polymeric composites with high mechanical stability and higher curing rate is underway for dental applications. Specific polymers named “dental resins” are used for cavity-filling applications. Adding hole-filling agents such as polyhedral oligomeric silsesquioxanes (POSS) to these polymers was found to improve the properties of the resins for dental applications. The experimental efforts have already been devoted to understanding the influence of POSS on the material properties of the resins. However, molecular simulations would be an ideal tool for understanding their properties at the molecular level. This insight into the molecular level relationship between the structure of additives and the resin will lead to the design of better novel materials. Polyhedral oligomeric silsesquioxanes (POSS) also called “spherosiloxanes” due to their spherical topology are a class of three-dimensional oligoromeric organosiliceous compounds. They have cage frameworks with different degrees of symmetry. They are 1–3 nm in diameter with the inner core made up of silicon and oxygen while the outer side is bonded to an organic functional group (R) leading to  Suite version 4.8.134 of Schrödinger 2022-4 release , which employed the OPLS4 force field . Using t8 s−1, and using a strain step size of 0.001 for 200 steps. These simulations are run for a maximum strain of 0.16, and the Young’s modulus is estimated from the slope of the linear portion within the elastic limit of the stress–strain curve. The simulation protocol involved using a simulation time of 250 ps with a time step of 2.0 fs and trajectory recording interval of 10 ps at a temperature of 300 K. Powder diffraction simulations are performed for all crosslinked composites using CuKa radiation with a wavelength of 1.54184 Å with a 2θ range between 5° and 70°.The stress–strain calculations were performed using the option of volume being conserved in all three directions, with a Poisson ratio of 0.5, a strain rate of 0.04 × 10The densities of the crosslinked control and other composites specified in V)% is the volume % shrinkage, curedρ and uncuredρ are the densities of cured and uncured polymer, respectively. For most of the resins used as dental composites, volume shrinkage is usually in the range of 1 to 6% [With respect to the density differences, the density of MAPOSS composites increased slightly as the amount of MAPOSS in the composite increased, while an opposite trend was observed with MIPOSS see . Methacr 1 to 6% . Wang et 1 to 6%  reported 1 to 6% ,22. FromMAPOSS has double bonds which are also involved in the curing/crosslinking process which in turn makes it bonded to the molecules of the polymer matrix while MIPOSS does not have double bonds which essentially makes it a standalone filler. Further, MIPOSS forms agglomerates within the polymer matrix while MAPOSS is more uniformly distributed in the polymer matrix. This is clearly observed as shown in From The Young’s modulus is estimated from the slope of the stress–strain curve within the elastic limit as shown in For more details on the graphical analysis of the stress–strain data for obtaining Young’s modulus, elastic stress, elastic strain, ultimate stress, and ultimate strain, refer to Madhuranthakam et al. ,13. The Nanocomposites of BisGMA, TEGDMA, MAPOSS, and MIPOSS were analyzed using molecular dynamics simulations. The structure interaction of MAPOSS and MIPOSS was confirmed and complemented by the experimental findings reported by Wang et al. . It was


Escherichia coli translation system and 1.96 Å resolution cryo-EM structure of THB-bound 70S ribosome with mRNA and initiator tRNA, independently suggest that THB binding at the intersubunit bridge B2a near decoding center of the ribosome interferes with the binding of A-site substrates aminoacyl-tRNAs and class-I release factors, thereby inhibiting elongation and termination steps of bacterial translation. Furthermore, THB acts as an anti-dissociation agent that tethers the ribosomal subunits and blocks ribosome recycling, subsequently reducing the pool of active ribosomes. Our results show that THB does not inhibit translation initiation as proposed earlier and provide a complete mechanism of how THB perturbs bacterial protein synthesis. This in-depth characterization will hopefully spur efforts toward the design of THB analogs with improved solubility and effectivity against multidrug-resistant bacteria.Thermorubin (THB) is a long-known broad-spectrum ribosome-targeting antibiotic, but the molecular mechanism of its action was unclear. Here, our precise fast-kinetics assays in a reconstituted  Thermorubin is a ribosome-targeting antibiotic. Here, using fast-kinetics and cryoEM, the authors reveal that thermorubin primarily blocks ribosome-recycling by tethering the ribosomal subunits besides impeding translation elongation and termination steps. There is an urgent need for the development of novel antibiotics with unique target sites to circumvent the ever-evolving problem of AMR among bacterial pathogens. However, the discovery of new antibiotics is rather challenging1. In that context, previously discovered antimicrobial compounds that have been neglected so far due to certain limitations can become attractive alternatives3. Understanding the molecular basis of action of these compounds could provide important clues for rational modification of the existing compounds4 or lead to the total synthesis of newer compounds to combat antibiotic resistance5.The global prevalence of antimicrobial resistance (AMR) among bacterial pathogens coupled with a barren antibiotic discovery pipelineThermoactinomyces antibioticus, a thermophilic actinomycete7. Originally discovered in 1964 as a broad-spectrum antibiotic, THB is effective against Gram-positive and Gram-negative bacteria with minimum inhibitory concentration (MIC) ranging from 0.025–0.05 μg ml−1 8. It is inactive against protozoans, yeast, filamentous fungi, and other higher eukaryotes6. Chemically, THB is a unique example of an aromatic anthracenopyranone metabolite, with anthraquinone moiety connected to an orthohydroxyphenyl moiety , THB has seldom been used for the treatment of infectious diseases10. Thus, it has been neglected for a long time and the precise mechanism of THB action remained elusive. This is probably also the reason for limited efforts towards design of the THB analogs with improved solubility.Thermorubin (THB) is a naturally occurring antibiotic produced by ety Fig.  presumabEscherichia coli uncovered its selective inhibitory effects on protein synthesis11. Subsequently, it was discovered that THB binds to 70S ribosome very tightly (Kd ≈ 20 nM) with an affinity ~100-folds higher than to individual ribosomal subunits, suggesting a single high-affinity site for THB binding formed by the subunit interface12. This suggestion was lately confirmed by a crystal structure of THB-bound 70S ribosome from the bacterium Thermus thermophilus13 which located its binding to the ribosomal intersubunit bridge B2a formed by the conserved nucleotides of 16S and 23S rRNAs of the small and large ribosomal subunits, respectively (PDB 4V8A)13. This binding site partially overlaps with that of the other clinically important antibiotics such as aminoglycosides and tuberactinomycins15. The linear tetracyclic moiety of THB stacks between C1409-G1491 base pair within helix 44 (h44) of 16S rRNA and A1913 within helix 69 (H69) of 23S rRNA, while its orthohydroxyphenyl moiety stacks upon U1915 of H6913. The nucleotide corresponding to C1409 in the eukaryotic ribosome is not base paired, which might prevent stacking of the tetracyclic moiety of THB, explaining its selectivity towards bacterial ribosomes11. Moreover, THB binding to the bridge B2a induces C1914 to flip out from H69 and adopt a conformation that can be incompatible with binding of the A-site ligands13. However, early biochemical studies claimed that THB inhibits the binding of initiator tRNA to the P-site in an initiation factor-dependent manner12. Noteworthy, these studies on THB-induced translation inhibition relied largely on S30 cell-extract11 or poly-uracil (poly-U) mRNA-based translation assays12. Although bridge B2a harbors nucleotides interacting with IF1 and IF216, it remained unclear how the THB-induced conformational dynamics could interfere with the activity of the initiation factors in bringing fMet-tRNAfMet to the P-site of the 30S subunit and stabilizing it there during translation initiation. Moreover, in the pivotal biochemical experiments12 that led to the conclusion that THB inhibits the initiation of protein synthesis, more than 40% of the ribosomes still contained fMet-tRNAfMet even at a saturating THB concentration12. The uncertainties about the step of translation THB actually targets prompted us to undertake a detailed investigation of structure-function mechanisms of THB inhibition of bacterial protein synthesis.THB is a bacteriostatic antibiotic; early investigations using E. coli17 to clarify the effects of THB on initiation, elongation, termination, and ribosome recycling steps of translation. The results of our fast kinetics experiments combined with our cryo-EM structure of the THB-containing ribosome initiation complex at 1.96 Å resolution demonstrate that the ribosome-bound THB has virtually no effect on initiation. Instead, THB impedes A-site delivery and accommodation of aa-tRNA, thereby impairing elongation. It also inhibits severely A-site binding of the class I release factors (RF) thereby inhibiting translation termination. Furthermore, THB acts as a ‘glue’ that tethers the ribosomal subunits together and inhibits splitting of the post-termination ribosome into subunits. Collectively, these findings refute the earlier notion of THB as an initiation inhibitor and provide comprehensive quantitative insights into the mechanism of translation inhibition by THB.In this work, we use a reconstituted in vitro translation system assembled from purified translation components of E. coli based fully reconstituted translation system18 and followed the synthesis of fluorescent reporter protein GFP+19. THB reduced the production of GFP+ in a concentration-dependent manner  estimated from the mid-point of the hyperbolic fit was 35 ± 6 nM . Here, we studied the effect of THB on subunit association, occupancy of fMet-tRNAfMet in the 70S initiation complex (70S IC), and puromycin reactivity of fMet-tRNAfMet in 70S IC.The inhibition of the initiation factor-dependent delivery of initiator tRNA into the P-site of the ribosome has been claimed earlier as the focal point of THB inhibition of bacterial protein synthesisfMet, IF1, IF2, and IF3 (see “Methods” and Supplementary Note 20. The second-order association rate constant (ka) for subunit association was estimated using Supplementary Eq.  demonstrating that THB had no inhibitory effect on subunit association. THB also showed negligible to no effect on association of 50S with naked 30S . Comparison of the amounts of 70S-ribosome-bound f[3H]Met-tRNAfMet, in the presence and absence of THB, revealed no difference in the 70S IC formation  assay to estimate the extent of fGTP, and Phe-tRNAPhe with an excess of mRNA-programmed 70S ribosome carrying f[3H]Met-tRNAfMet in the P-site and a cognate (UUC) codon in the A-site in a quench-flow instrument. First, we monitored the time course of GTP hydrolysis on EF-Tu, which takes place concomitantly with aa-tRNA delivery to the A-site of the ribosome upon codon recognition  and dipeptide formation (τDip), respectively. Further, the sum of mean times of aa-tRNA accommodation and subsequent peptidyl transfer reaction (together referred as τA/PT) was estimated by subtracting τGTP from τDip22 (see Supplementary Note To pinpoint the exact step(s) of the elongation cycle affected by THB, we reacted ternary complexes  of the EF-Tu dependent aa-tRNA delivery reaction  for THB binding to the 70S ribosome in stopped-flow, monitored by the change in THB fluorescence at 340 nm10. The value of kTHB ~ 0.03 μM−1 s−1  codon in the A-site. We observed about 20-fold reduction in the ase Fig. . Thus, w3H]Met-tRNAfMet in the P-site but was programed with Met-Phe-Phe-stop or Met-Phe-Phe-Phe-stop mRNA coding for fMFF tri- or fMFFF tetrapeptide. These 70S ICs were mixed with a large excess of cognate ternary complexes EF-Tu•GTP•Phe-tRNAPhe (T3) and elongation factor G (EF-G) that translocate peptidyl-tRNA from the A- to P-site of the ribosomes. After rapid mixing in a quench-flow instrument, the time evolution of di- and tripeptide was measured in the case of Met-Phe- Phe-stop mRNA and that of di-, tri- and tetra-peptide in the case of Met-Phe-Phe-Phe-stop mRNA. From these experiments, the mean times of di- and tripeptide formation could be extracted in the first case and the mean times of di-, tri- and tetra- peptide formation in the second case (see Supplementary Note τTrip) 101 ± 9 ms, measured with 5 μM EF-G in the absence of THB, increased to 1024 ± 35 ms in the presence of THB  events from the measured τTrip (see Supplementary Eq. (23 for details). Surprisingly, the estimated τTrans was similar both in the presence and absence of THB, i.e. 63 ± 9 ms, indicating that THB does not affect EF-G catalyzed translocation. This conclusion was further confirmed by experiments in which the mean time for tetrapeptide formation τTetra was measured  irrespective of the presence or absence of THB as in case of tripeptide experiments , which does not include translocation. Thus, we conclude that THB does not affect EF-G dependent translocation. Instead, THB extends the elongation cycle time by impeding aa-tRNA delivery to the ribosome and its accommodation into PTC. Taking also into account that T3 outcompetes THB in the binding to the ribosome  of peptide release by RF2 in the absence of THB was 6.6 μΜ −1 s−1  was 5.6 s−1, similar to that measured in a previous report24. However, when pre-TC was pre-incubated with 5 μΜ THB, the rate of f[3H]Met release, kobs, dropped drastically by 550-fold, from 5.6 s−1 to about 0.01 s−1  consisting of 70S ribosome programmed with a Met-Stop mRNA and carrying a peptidyl-tRNA analog fMet-tRNAfMet and tRNAPhe were prepared as described17. BODIPYTM (BOP)•Met-tRNAfMet was prepared as described earlier38. In vitro transcribed XR7-mRNAs with strong Shine-Dalgarno sequence (AAGGAGG) and a small ORF AUGUUCUUCUAA (Met-Phe-Phe-stop), AUGCUCUUCUAA (Met-Leu-Phe-stop), AUGUUCUUCUUCUAA (Met-Phe-Phe-Phe-stop), and AUGUAA (Met-stop) were prepared according to Holm et al.35 Concentrations of the ribosomes, translation factors, tRNAs, and mRNAs were measured spectrophotometrically. THB (Thermorubin A) was purchased from AdipoGen Life Sciences and was dissolved in Dimethyl sulfoxide (DMSO) solution and stored at −20 °C. [3H] Met and [3H] GTP were from Perkin Elmer and all other chemicals were from either Merck or Sigma-Aldrich.All in vitro translation experiments were conducted at 37 °C in HEPES–Polymix buffer (pH 7.5) (5 mM HEPES (pH 7.5), 95 mM KCl, 5 mM NHE. coli along with 20 amino acids and energy pump components19. The reaction was started by the addition of in vitro transcribed and purified mRNA encoding a reporter protein (GFP+). To test the effect of THB on GFP+synthesis, we added THB in various concentrations (0–1 μM) to the reaction mixture. The synthesis ofGFP+ (at 37 °C) was monitored in real-time as the time-dependent increase in GFP+ fluorescence signal (excitation − 460 nm and emission − 518 nm) using a TECAN Infinite 200 PRO multimode plate reader. The experiments were done in triplicates.We used our reconstituted cell-free translation system containing active 70S ribosomes (1 μM), translation factors (1–10 μM), 20 aminoacyl tRNA synthetases (1–10 U), and tRNAs (bulk tRNA 100 μM) purified from fMet (2 μM) and Mix B − 50S ribosome (0.5 μM). The reaction was started by rapid mixing of the Mixes A and B in a stopped-flow instrument  equilibrated at 37 °C. All IFs were omitted for naked subunit association. The time-course of subunit association was monitored by following the increase in Rayleigh light scattering at 365 nm20. For THB experiments, 10 μM of THB was added to both mixes. The average data  were fitted with complex formation function (Supplementary Eq. (Two reaction mixes were prepared and incubated separately at 37 °C for 10 min. Mix A − 30S ribosome (0.5 μM), mRNA (Met-Phe-Phe-stop) (2 μM), IF1 (2 μM), IF2 (2 μM), IF3 (1 μM), and fMet-tRNAfMet (0.3 μM). THB (10 μM) was added to both mixes. Equal volumes of the two mixes were rapidly mixed in a stopped-flow instrument  at 37 °C and the resultant increase in BOP fluorescence (at 590 nm) due to the binding of BOP•Met-tRNAfMet to the 70S ribosomes as a function of time was monitored. For other experiments, either IF2 was incubated with BOP•Met-tRNAfMet in Mix B, or all IFs were absent. Experiments were carried out in triplicates and average data were fitted with an exponential function (Supplementary Eq. (Two mixes were prepared and incubated separately at 37 °C for 10 min. Mix A − 70S (0.25 μM), mRNA (Met-Phe-Phe-stop) (2 μM), IF1 (1 μM), IF2 (1 μM), and IF3 (0.5 μM) and Mix B - BOP•Met-tRNAfMet) binding to the mRNA-programmed 70S ribosomes21. In this assay, 70S ribosomes (0.5 μM) were incubated with mRNA (Met-Phe-Phe-stop) (2 μM), IFs (1 μM each), and f[3H]Met-tRNAfMet (0.6 μM) for 15 min at 37 °C to prepare 70S IC. THB (10 μM) was added to the IM before or after incubation (as indicated). To check f[3H]Met-tRNAfMet binding, an aliquot (50 μL) of 70S IC was applied to a nitrocellulose filter membrane (pre-soaked in HEPES–polymix buffer (pH 7.5)) connected to an air suction filtration assembly and washed twice with ice-cold HEPES–polymix buffer (5 mL). The radioactivity [3H] retained in the filter (representing the bound f[3H]Met-tRNAfMet to 70S ribosomes) was measured using QuickSafe scintillation cocktail in Beckman LC6500 counter. The experiments were repeated at least three times and the average radioactivity count (cpm) was plotted for each case.The nitrocellulose filter-binding assay was performed to measure the extent of initiator tRNA (f[3H]Met-tRNA3H]-Met-tRNAfMet (0.6 μM) at 37 °C for 15 min. Next, 200 μM of Pmn was added and incubated for another 5 min. THB (10 μM) was either pre-incubated with IM or added later to IM. The reaction was quenched by adding 50% formic acid and the samples were centrifuged at 14000 rpm for 15 min. Supernatant and pellet were separated, and 0.5 M KOH (165 μL) was added to the pellet. To both supernatant and pellet, 33% methanol was added and centrifuged at 14000 rpm for 15 min to extract [3H]fMet-Pmn formed. Radioactive [3H] counts (cpm) in both supernatant and pellets were measured using QuickSafe scintillation cocktail in Beckman LC6500 counter. Experiments were performed in triplicates along with negative controls .To check the accommodation of the initiator tRNA in the P-site of the 70S ribosome and subsequent activity in peptide bond formation we performed the puromycin (Pmn) assay. For that, we prepared an initiation mix (IM) by incubating 70S ribosomes (0.5 μM), mRNA (Met-Phe-Phe-stop) (1 μM), IF1(1 μM), IF2 (1 μM), IF3 (0.5 μM), and fMet-tRNAfMet (0.6 μM), 1 mM GTP and 1 mM ATP. EM - EF-Tu (10 μM), Phe-tRNAPhe (2-12 μM), Phenylalanine (200 μM), Phe-RS (0.5 μM), GTP (1 mM) and ATP (1 mM). In tri-and tetra-peptide experiments, EM was supplemented with EF-G (10 μM). THB was added to IM or EM or to both as indicated. Both IM and EM were incubated at 37 °C for 15 min. Equal volumes of each mix were rapidly mixed in a quench-flow instrument  and the reaction was quenched with 17% formic acid at different incubation intervals. Near-cognate reactions of GTP hydrolysis and dipeptide experiments were slow; therefore, the samples were mixed manually. The samples were processed as described earlier17. The average times of GTP hydrolysis (τGTP), dipeptide (τDip), tRNA accommodation-peptidyl transfer (τA/PT), tripeptide (τTrip), and tetrapeptide (τTetra) were estimated as described in Supplementary Note GTP hydrolysis and dipeptide formation experiments were conducted as described earlier3H]fMet-tRNAfMet in the P site and a stop codon (UAA) in A site), were prepared by mixing together 70S ribosome (2 μM), IF1 (2 μM), IF2 (2 μM), IF3 (2 μM), XR7 mRNA (10 μM), f[3H]Met-tRNAfMet (2.5 μM). Later, 2 mM Mg(OAc)2 was added to the mixture for stabilization of the complex. After incubation at 37 °C for 20 min the pre-TC was purified by ultracentrifugation  through a sucrose cushion (1.1 M sucrose) containing an additional 4 mM of Mg(OAc)2 at 4 °C for 2 h. The pellet containing pre-TC was resuspended in HEPES–polymix Buffer (pH 7.5) and stored at −80 °C.Pre-termination complexes (pre-TCs) (70S programmed with mRNA(Met-stop) carrying f[g for 15 min to separate released f[3H]Met in the supernatant and intact f[3H]Met-tRNA in the pellet. The pellets were treated with 165 μL of 0.5 M KOH at room temperature for 10 min to release f[3H]Met. The amount of radioactive f[3H]Met in supernatant and pellet was determined using QuickSafe Flow scintillation cocktail in Beckman LS6500 counter. As controls, aliquots of pre-TC were taken before and after QF experiments to monitor the spontaneous hydrolysis of f[3H]Met from f[3H]Met-tRNAfMet in pre-TC by manual quenching. Experiments were performed in triplicates and average data were analyzed using the single-exponential function in OriginPro 2016 (Origin LabCorp).For peptide release experiments, equal volumes of pre-TC (0.5 μM) and release factor (RF2) (0.5–10 μM), were rapidly mixed at 37 °C in a temperature-controlled quench-flow (QF) instrument  and samples were quenched at defined time intervals using HCOOH to a final concentration of 17%. The samples were centrifuged in the cold room (4 °C) at 20,000 × Phe (1 μM) for 5 min at 37 °C. Similarly, a factor mix (FM) containing RRF (20 μM), EF-G (10 μM), and IF3 (1 μM) was prepared. THB (10 μM) was either incubated with post-TC or added to the FM mix as indicated. Equal volumes of post-TC and FM were rapidly mixed in a stopped-flow instrument  and the time course of post-TC splitting into subunits was monitored as the decrease in Rayleigh light scattering at 365 nm27. The rate of post-TC splitting was estimated by fitting the data with the double-exponential equation in OriginPro 2016 (Origin LabCorp). Similarly, RRF (10–60 μM) was titrated for concentration-dependent effects against THB bound post-TC. Experiments were carried out in triplicates.The post-termination ribosome complex (post-TC), with an empty A-site and deacylated tRNA in the P-site, was prepared by incubating 70S ribosome (0.5 μM) with mRNA (Met-Phe-Phe-stop) (1 μM) and deacylated tRNA21, 70S ribosomes (0.5 μM) were incubated just with mRNA (Met-Phe-Phe-stop) (1 μM) for 15 min at 37 °C. Likewise, an initiation factor (IF) mix containing IF1 (8 μM) and IF3 (2 μM) was prepared. THB was added in the mRNA-70S mix or IF mix as indicated. The kinetics of dissociation of tRNA-free 70S into ribosomal subunits was monitored as described above. Moreover, for the assessment of THB-induced re-association of subunits, the mRNA-70S complex (0.5 μM) was first split into subunits by lowering the concentration of Mg++ to 1.3 mM . IF mix either contained both IF1 (8 μM) and IF3 (2 μM) or none. Both mixes were incubated for 10 min at 37 °C and rapidly mixed in a stopped-flow instrument. The time-course of Rayleigh light scattering at 365 nm was fitted to the exponential function as above.Alternatively, for IF1/IF3 mediated splitting assayfMet (5 μM) were added and the mixture was incubated for another 10 min. Quantifoil grids  were glow discharged , and 3 μL of the sample (mixture) was added onto a grid, the excess sample was blotted off (blot force: 0 and blot time: 3 s) and vitrification of the sample was performed by plunging the grid into liquid ethane using a Mark IV Vitrobot  operated at 4 °C and 95 % humidity. Grids were screened on a Glacios cryo-electron microscope (at 200 keV) with falcon III detector . The final data collection was carried out on a Titan- Krios   at 300 keV using a K3 direct electron detector (Gatan) with defocus range of −0.6 to −2.0 μm and electron dose of 1.025 e/Å2 per frame. A nominal magnification of 105,000x was applied, resulting in a final object sampling resolution of 0.8617 Å/pixel. A total of 13,944 micrographs were collected over 24 h.We first incubated 70S ribosomes (200 nM) with THB (10 μM) for 5 min at 37 °C. To this, XR7 mRNA (Met-Phe-Phe-Stop) (2 μM) and fMet-tRNA42. After patch motion correction and contrast transfer function (CTF) estimation, a total of 13,914 micrographs were selected for particle picking. Using blob-picker and followed by 2D-template-based particle picking, we extracted a total of 1,930,095 particles. This was followed by several rounds of 2D classification of the particles and selection of good particles while discarding junk particles. We curated a total of 1,776,568 particles from 2D classification and used them for the ab-initio reconstruction of 3D volumes. A total of 1,132,682 particles from good 3D volumes  were selected and further refined using heterogenous 3D refinement, homogenous refinement (legacy), and finally homogenous 3D refinement. A final map of our complex at 2.03 Å resolution was again processed to global and local CTF refinement, adjusted for per-particle defocus, and sharpened using the map sharpening function in CryoSPARC. The cryo-EM maps were visualized at each stage of 3D refinement using USCF chimera43. Details of the cryo-EM data processing are presented in Supplementary Fig. Data processing was carried out using comprehensive data processing package in CryoSPARC v3.3.1E. coli 70S ribosome (PDB ID 7K00)30 was used as a template for model building. First, model-to-map alignment was carried out using UCSF Chimera43. The map of THB-70S•mRNA•fMet-tRNAfMet (THB-70S IC) complex was refined using the Phenix real-space refinement45. The protein and rRNA chains were visually checked in Coot46 and manually adjusted wherever necessary. Antibiotic THB was manually docked into the experimental density, followed by real-space refinement in Phenix44. All figures showing atomic models were generated using UCSF Chimera43 and labeled with Adobe Illustrator (Adobe Inc.).The structure of the Further information on research design is available in the Supplementary InformationPeer Review FileReporting Summary