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This work aims at enhancing the concrete performance using a new protective coating named as asphaltic polyurethane (As/PU) coating, which prepared at different NCO/OH molar ratios (1, 1.1, 1.2, 1.3 and 1.4). As/PU coating was prepared by the reaction of a fixed amount of methylene diphenyl diisocyanate (MDI) with the equivalent weight of mixed polyol (80% asphalt and 20% polyester). The performance of the prepared coatings was examined by the determination of curing time, dry film thickness (DFT), adhesion strength, and flexibility. The formulated coatings were applied on 28-days-cured concrete. The coated and uncoated concrete samples were evaluated regarding contact angle, water absorption, and chloride permeability. The resistivity of coated and uncoated concrete against sulfuric acid and sodium chloride solutions was evaluated. The preliminary results proved that the increase of NCO/OH molar ratio results in a remarkable increase in DFT, adhesion strength accompanied by decrease in curing time and flexibility of the prepared coatings. The concrete sample coated by As/PU with NCO/OH molar ratio of 1.4 demonstrates the highest contact angle associating with the lowest water absorption and chloride permeability. In addition the increase in NCO/OH molar ratio of the applied coating has a positive impact on the mechanical properties of concrete. The coated concrete samples recorded higher resistivity against acid and salt attack compared to uncoated one. This proves the eco-efficient use of the prepared As/PU as an innovative protective coating for concrete.

The motivation behind this work is to evaluate the impact of nano-magnesium calcite (NMC) waste on the performance of cement mortar (CM) and its resistivity to sulfate attack. The addition of urea and urease enzyme to ground water resulted in the removal of Ca2+ and Mg2+ as NMC precipitate (byproduct of treatment process). As a beneficial recycling method, NMC with different proportions were individually blended with CM to enhance its performance in normal and sulfate-rich media. The results revealed that the NMC has a positive impact on the early-ages compressive strength of CM. Where, the addition of 1 wt% of NMC led to a significant enhancement in the rates of strength development and total porosity reduction at all ages of hydration. Comparing with reference mixture, a highest performance in sulfate medium was obtained in case of all CMs containing NMC. Complementary, the CM incorporated with 1 wt% NMC showed the highest resistance to sulfate attack (up to 12-months) which associated with lower compressive strength regression, total porosity increment, sulfate expansion and consequently lower ettringite formation rate.

This work investigated the synergistic impact of silicate- and MgO-reactivity on the performance of Mg-silicate-based cement. Ceramic waste (CW) and glass waste (GW) as two silicate sources were used. Different decarbonation temperatures (800 and 1200 °C) were applied on magnesium carbonate to yield MgOs with different reactivities (MgO800 and MgO1200). Highest strength and shortest setting times associated with an enhancement in silicate dissolution rate and the formation of large magnesium silicate hydrate (MSH) were recorded in case of GW-MgO800-H2O system. The use of MgO1200 resulted in the retardation of MSH-formation rate in both of GW-MgO-H2O and CW-MgO-H2O systems. Comparing with GW-MgOs set, the CW-MgOs one showed the lowest performance at all curing ages. Due to high alumina content in CW, secondary hydrotalcite-like phases were detected in CW-MgOs alongside MSH-phase.

This study evaluates the synergistic impact of nano-silica (NS) and nano-clay (NC) on the hydration characteristics and microstructure of ordinary Portland cement (OPC) paste. Two main parameters, which strongly affect the physico-chemical and mechanical performance of OPC-pastes, including the hybrid NS and NC mass% (0, 1, 2, 4 and 6 wt% at NS:NC mass ratio of 1:1) and superplasticizer (SP) content, SP% (0 and 1 mass% with respect to OPC) have been studied. The results proved the addition of hybrid NS/NC has a good impact on the performance of OPC-pastes. All NS/NC-cement composites containing 1% SP showed the highest engineering properties comparing with composites with no SP. The composite containing the hybrid effect of 3 wt% NS:3 wt% NC:1 wt% SP presented the highest performance at all ages of curing as confirmed by X-ray diffraction, thermal analysis and scanning electron microscopy.

This work aims at enhancing the commercial viability of magnesium oxychloride cement (MOC) by preparing one-part MOC (just added water). It was synthesized by mixing of magnesium chloride (MgCl2) with magnesium oxide (MgO) at water to MgO (W/MgO) ratios, making MOC-paste in non-workable form. The MOC-slurry was immediately dried in an oven at 60 °C for 24 h, yielding solidified material which pulverized to produce one-part-MOC powder with a fixed particle size. Two major factors, which affect the performance of one-part MOC, were examined: the first is the increase of MgO/MgCl2 molar ratio, while the W/MgO ratio is kept maintaining constant. The second includes the increase of W/MgO ratio at constant MgO/MgCl2 molar ratio. One-part-MOC powder was mixed with water at W/MOC powder ratio of 0.25, and then cured. A traditional two-part MOC containing MgO (solid part) and MgCl2 solution (liquid part) was used for comparison. The results revealed that the W/MgO ratio and MgO/MgCl2 molar ratio strongly affect the performance of one-part MOC. The compressive strength development of the hardened cement pastes proved the continuation of hydrate phases formation after mixing one-part-MOC with water. At 14-day of curing, the compressive strength value of an optimal one-part MOC was found to be lower than that of two-part-MOC, containing the same MgO/MgCl2 molar ratio, by 14%.

The objective of this work is to prepare one-part geopolymer (OPG) cement using thermal activation of cement kiln dust (CKD) and feldspar (FS). A homogeneous CKD/FS dry-blend, at weight ratio of 60/40, was exposed to elevated temperature in the presence of soda ash (Na2CO3), yielding smelted glassy material. Rapid air cooling was conducted on the transformed material, followed by grinding to produce OPG-powder. Three main parameters including vitrification temperature (1200 and 1300 °C), heat treatment duration (2 h and 3 h), and Na2CO3 content (10 and 20 wt%), were examined. A partial transformation to amorphous structure was recorded after the exposure of CKD/FS to 1200 and 1300 °C for 2 h heat treatment duration (in the absence of Na2CO3). With the increase of treatment time (3 h at 1300 °C), the sintering of mineral was occurred, leading to the increase in their crystallinity. Thermal treatment in the presence of Na2CO3 has a potential impact on the transformation of CKD/FS to vitreous structure as confirmed by X-ray diffraction (XRD). Where, the use of 20 wt% Na2CO3 leads to produce glassy material, with 100% amorphous content, which can reacts with water to form binding material with 28-days compressive strength of 52 MPa.

An experimental investigation was performed to evaluate the impact of curing conditions on the physico-mechanical properties and firing resistivity of cement mortar (CM) containing reactive magnesium oxide (MgO). Three different curing media including Tap water (TW), normal carbonation (NC) and accelerated carbonation (AC), have been applied. Two MgOs with different reactivity were used (MgO550 and MgO1250); where, 550 and 1250 are referred to the calcination temperatures applied on hydromagnesite. 10 mass % of MgO550 as well as MgO1250 were individually added to CM. The cured CMs were exposed to different elevated temperatures (250, 500 and 750 °C) for 2 h soaking time. The phases composition and microstructure of CMs were investigated via Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) techniques. The results proved that the physico-mechanical properties and firing resistivity of control CM without MgOs cured in TW were superior to those exposed to NC and AC. The MgOs have detrimental impact on the properties of TW-cured-CM, due to the formation magnesium silicate hydrate with lower binding capacity compared to calcium silicate hydrate. Interestingly, the CM-MgOs cured in AC or NC showed the highest mechanical properties as well as firing resistivity compared to control sample at the same curing media, respectively. In AC and NC, the MgO1250 has a higher impact on compressive strength development and firing withstanding of CM compared to MgO550. The optimum curing condition and MgO type, which gave the highest engineering properties and the highest resistivity to elevated temperature were AC and MgO1250.

This study is the first attempt to investigate the possibility of incorporating nano-activated carbon (nAC), prepared from residual biomass of olive trees, on the properties of alkali-activated slag (AAS) pastes. After suitable preparation of nAC, it was added into AAS pastes at various levels starting from 0.5 to 3.5, by weight. The results of workability, compressive strength , total porosity and drying shrinkage were measured. Different techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA) and its derivative (DTG), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were used to identify the hydration products and the microstructural development of the AAS pastes with/without nAC. The results showed a negative effect of nAC on the workability of the mixtures. The incorporation of 1.5% nAC showed the highest compressive strength, the lowest total porosity and drying shrinkage. The incorporation of 3.5% nAC led to a reduction in the compressive strength and an increase in the total porosity and drying shrinkage. It can be concluded that the incorporation of suitable ratios of nAC can be beneficially used to resolve one of the main problems of AAS (i.e. drying shrinkage). Thus, the addition of nAC could enhance the probability of utilizing AAS as a good alternative to Portland cement .

This study investigates the impact of low-cost barium carbonate and barium silicate nanoparticles (NBC and NBS, respectively) on the performance and phase composition of cement mortar (CM). The results reveal that the individual addition of NBC and NBS causes setting times shortening and mechanical properties increment. Nevertheless, the NBS exhibits the higher efficiency at all addition levels (1, 2, and 3% by weight of cement). The incorporation of NBC results in the consumption of sulfate within cement matrix and the formation of insoluble barite (BaSO 4 ) and calcium monocarboaluminate phases. Although the NBS also represents high efficiency in the uptake of sulfate, the reactive silicate within NBS plays a significant role in the formation of additional calcium silicate hydrate content through the consumption of portlandite (resulted from cement hydration). This could enhance the successful application of cement-NBS mixtures as super sulfate resistant cements.

This work focuses on the fabrication of white one-part alkali-activated magnesia-based cement (AAMC) using the vitrification of talc (Tc) in the presence of NaOH or NaAlO2. The results revealed that regardless of Na2O-source, increasing alkali-activator content (up to Na2O/Tc of 0.15) enhances the transformation of Tc from crystalline into amorphous structure with high hydraulic reactivity. Comparing to white Portland cement, one-part-AAMC synthesized in the presence of NaAlO2 shows higher early compressive strength, higher whiteness, and lower bulk density. This improves the capability of utilizing this mixture as a lightweight and a rapid-hardening cement in prestige construction projects and decorative works.

Construction and demolition (C&D) waste are generated during the creation of structure or building or when renewing or demolishing a current structure. C&D waste exhibits many environmental problems including diminishing landfill, increasing wastage areas, landfill contamination, and increasing energy required for waste disposal and transportation. The re-using C&D waste as an aggregate in concrete making have reduced extraction demanding and landfill pressure. The utilization of C&D as recycled concrete aggregate (RCA) alternative to natural one not only decreases environmental problems but also leads to the conservation of naturally occurring resources. On the other hand, the synthesis of an aggregate from powdered industrial solid waste was also found to have a good alternative to natural aggregate with lower specific gravity and high thermal insulation . This work have reviewed the application of C&D and synthetic aggregates for making structural and non-structural concrete. Owing to the contaminants attached on the surface of RCA, the replacement of natural aggregate with this aggregate has resulted in a significant reduction in the performance of cement concrete . Therefore, many approaches have been done to enhance the quality of RCA. Among these different methods, the carbonation and pozzolan slurry are regarded as the best methods for enhancing the properties of RCA. Synthetic aggregate could be prepared by different methods including sintering, cold bonding, and autoclaving. Lightweight aggregate synthesized by the cold-bonding method could be successfully applied to fabricate a moderate strength lightweight concrete. More research is required to evaluate the resistivity of lightweight concrete containing autoclaved lightweight aggregate.

In this paper, a simple eco-sustainable approach was applied to synthesize unfired building bricks , in which cement kiln dust (CKD), red clay brick waste (RCBW), and silica fume (SF) were the main ingredients. The CKD-RCBW-SF composite was adjusted at different weight ratios of 50-50-0, 50-40-10, 50-30-20, and 50-20-30 wt%. The fabrication process included three main stages, i.e. dry blending, water mixing, and casting. Different curing conditions were applied (water, air, and CO 2 -gas) to assess the effect of curing type on the performance of the prepared bricks. The results demonstrated that increasing SF content caused an increase in compressive strength escorted by a significant decrease in bulk density of the hardened bricks, regardless of curing type. All over of the curing media, the hardened samples cured in water showed the highest performance. The highest 28-days compressive strength value (47 MPa) was achieved by hardened CKD-RCBW-SF composite (at a weight ratio of 50-20-30 wt%, respectively) cured in water. Unlike its effect on the physical and mechanical performances, increasing SF content negatively influenced the capability of the hardened bricks to CO 2-sequestration. Specifically, the hardened bricks with no SF cured in CO2 gas for 28-days can sequestrate higher CO2 content (~75 kg/ton) compared to the hardened samples containing 30 wt% SF (~59 kg/tonne). The proposed method is not only considered as an innovative approach for mitigating CO2 emission resulted from the traditional bricks industry, but also strongly contributed to waste disposal, the conservation of the reserve of natural materials, the decrease of energy demand and processing cost, and the enhancement of the ability of the hardened bricks to CO2-capture.

It is recognized that the presence of amorphous aluminosilicates, which have high ability to interact with alkalis, is one requirement for synthesizing conventional alkali-activated cements. This paper presents an innovative method for preparing alkali-activated calcium carbonate (CaCO3)-based cement, in which weathered-cement kiln dust (W-CKD) is the main precursor. Sodium oxide (Na2O) source (sodium hydroxide, sodium silicate, and sodium aluminate), Na2O-content (1.93, 3.87, 5.82, and 7.75 wt%), type of mixing water (tap and sea water), and the content of lead glass sludge (LGS: 10, 30, and 50 wt%) are the main compositional factors, which strongly affect the performance of the prepared cement. Pirssonite double salt CaCO3.Na2CO3·2H2O is alone main binding phase within sodium hydroxide-activated W-CKD with modest 28-day compressive strengths (~2–9 MPa). A significant enhancement in 28-day compressive strength (~15–21 MPa), which associated with the formation of calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H) was observed when sodium silicate and sodium aluminate used as alkali activators. On the other hand, mixing sea water with alkali activators results in the formation of nano materials with high effectiveness in the improvement of the mechanical performance of the prepared cement. Incorporating LGS within sodium aluminate-activated W-CKD enhances the formation of C-S-H accompanied by a significant improvement in the compressive strength of the hardened cement (25–52 MPa at 28-day of air curing). Moreover, all hardened W-CKD/LGS mixtures exhibit low Pb-leachability in acidic media. This strongly reflects on the safe application of these mixtures in the construction works.

This work focuses on the individual impact of nano- and ultrafine micro magnesia (N–MgO and UM-MgO, respectively) on the early performance of high volume fly ash (FA)-blended-cement mortar (CM). N–MgO and UM-MgO were synthesized using a thermal treatment of lightweight hydromagnesite at 550 and 1100 °C, respectively. Different contents of MgOs (1, 3, and 5 wt% by weight of powder) were individually added to FA-blended-CM. The results revealed that the N–MgO exhibits higher efficiency in the acceleration of early PC-FA system hydration compared to UM-MgO at all addition levels. The addition of 1, 3, and 5 wt% N–MgO to FA-blended-CM has resulted in the enhancement of 3-days compressive strength value by ~26, 94, and 103%, respectively; whereas the UM-MgO shows a modest effect. The small particle size, low crystallinity, and high hydration reactivity are the dominant features of N–MgO, which reflect on the enhancement of FA-pozzolanic activity accompanied by the acceleration of strength-giving-phases formation at early ages of hydration. To achieve the sustainability, we have recommend the use of N–MgO, as it contributes to cost minimization, energy saving, and the mitigation of carbon footprint.

In this paper, low-cost nano-zinc ferrite (NZF) was used to evaluate its efficacy, as compared with nano-zinc oxide (NZO), on the performance of the fresh and hardened alkali activated slag (AAS). An elongation in setting times and a reduction in early-ages’ compressive strengths were recorded in the case of AAS individually containing 0.5, 1, and 1.5 wt% NZO. A turning point was observed after 3 days of curing as AAS-NZO set represents compressive strengths higher than those of reference sample. The embedding NZF in alkali activated system has resulted in setting time shortening and mechanical properties improvement at both early and later ages. This means that the acceleration effect of nano-ferrite compensates the retardation impact of NZO on the activation of AAS-hydration. Regardless its promising properties, AAS-NZF composites demonstrate compressive strength, γ-ray radiation shielding, and anti-fungal activity higher than those recorded in the case of AAS-NZO one at all addition levels.

High drying shrinkage is considered as one of the main drawbacks which hinder the mass production of alkali activated slag (AAS). The formation of expansive phases was found to be the dominant factor for drying shrinkage reduction in sodium silicate-activated system. This work aims at studying single and synergistic effects of the prepared nano-magnesia (NM) and -alumina (NA) on compressive strength and drying shrinkage of AAS. A preliminary study revealed that the NM has a positive impact on the early age’s compressive strength of AAS; meanwhile NA had an opposite effect. Complementary, the drying shrinkage of AAS-NM significantly decreases with the increase of NM-content. Comparing with reference sample, the hybrid inclusion of 1 wt% NM and 1 wt% NA resulted in a significant drying shrinkage reduction and considerable compressive strength increment. The main reason behind this effect is the synergistic formation of calcium silicate hydrate and calcium aluminosilicate hydrate in parallel with expansive hydrotalcite and stratlingite phases as they have a potential effect on the performance of AAS including the retardation of water evaporation, reduction of pore volume, and drying shrinkage. This makes AAS-NM-NA composite can be beneficially used as a binder in the production of structural concrete with high durability.