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The role of nanozinc source (nanohydrozincite: nHZ; nanozinc oxide: nZO) on the performance of alkali-activated slag (AAS) was explored for the first time in the present work. The results showed that nHZ with different contents (0.5, 1.0, and 1.5 wt%) retards the early hydration rate of AAS, whereas nZO showed the lowest retardation effect. Zn(OH)

Geopolymer bricks from lead glass sludge (LGS) and alumina flakes filling (AFF) waste were synthesized in the present work. AFF waste was chemically treated to prepare sodium aluminate (NaAlO

This study represents the sustainable/safe consumption of lead glass sludge (LGS) in the fabrication of thermally insulating foamed glass via sintering (750–950º C) and chlorination processes. The impact of selected additives including calcium chloride (CaCl2) and sodium hydroxide (NaOH) on the foaming efficiency and Pb-stabilization has been deeply investigated. LGS is mainly lead silicate material with considerable content of calcium carbonate, which acts as foaming agent during sintering process. The newly developed foamed-materials exhibited thermal conductivity of 0.054–0.136 W/m.K, density of 0.23–1.10 g/cm3, porosity of 63.3–92.6%, and compressive strength of 0.10–2.69 MPa. X-ray diffraction proved that the immobilization mechanism was attributed to the transformation of free Pb within LGS into insoluble ganomalite Pb9Ca5MnSi9O33 phase. Adding NaOH enhanced the foaming process accompanied by a significant reduction in Pb-leaching. Incorporating CaCl2 has resulted in a retardation in Pb-leaching, which associated with Pb-stabilization and Pb-vaporization. In an attempt to reduce CO2-emission, the potential use of alkali-rich-wastewater (AW) as eco-friendly alkali source in lieu of NaOH was studied. Regardless of the variation in Pb-concentrations in leachates, all samples recorded Pb-concentrations lower than the safe limit (≤ 5 mg/l), achieving Pb-immobilization of 95.98–99.87%. The significantly reduced thermal conductivity and enhanced Pb-immobilization efficiency along with the reasonable compressive strength summarize the major innovation presented in this study.

This study focuses on utilizing a plant-derived urease enzyme (PDUE)–urea mixture to remove heavy metals from water as constituents of nano-carbonate minerals. The bio-removal process was conducted by individually mixing PbCl2, CuCl2, and NiCl2 solutions with a PDUE–urea mixture, followed by incubation for 24 h at 23 ± 2 °C. The preliminary results revealed that the proposed method exhibited high Pb removal efficiency (˃ 99%) in a short time (8 h); meanwhile, moderate Cu and Ni removal efficiencies (67.91% and 58.49%, respectively) were obtained at the same incubation time. The concentration of heavy metals (50–200 mM) had an insignificant effect on the bio-removal rate, indicating that the PDUE–urea mixture is highly effective for the removal of heavy metals at different concentrations. The bio-removal process involved the transformation of soluble heavy metals into insoluble carbonate materials. A spherically shaped nano-cerussite (4–15 nm), a malachite hexahydrate nanosheet (thickness 8 nm), and an ultrafine micro-hellyerite (thickness 0.3 μm) were the main minerals produced by the Pb, Cu, and Ni bio-removal processes, respectively. As a beneficial application, nano-cerussite was used as an additive in an alkali-activated slag/ceramic waste-based geopolymeric coating. A preliminary study proved that increasing the nano-cerussite content enhanced the resistance of the geopolymeric coating to sulfur-oxidizing bacteria, which is detrimental to normal concrete, particularly in sewer systems.

This study represents the sustainable/safe consumption of lead glass sludge (LGS) in the fabrication of thermally insulating foamed glass via sintering (750-950º C) and chlorination processes. The impact of selected additives including calcium chloride (CaCl

Hybrid cement (HC) can be defined as alkali activated-blended-Portland cement (PC). It is prepared by the addition of an alkaline solution to high-volume aluminosilicate-blended-PC. Although this cement exhibits higher mechanical performance compared to conventional blended one (aluminosilicate–PC blend), it represents lower commercial viability because of the corrosive nature of alkaline solution. Therefore, this study focuses on the preparing one-part HC using dry activator–based BFS (DAS). DAS was prepared by mixing sodium hydroxide (NaOH) with BFS at low water to BFS ratio, followed by drying and grinding to yield DAS-powder. Different contents of DAS (equivalent to 70 wt.% BFS and 1, 2, and 3 wt.% NaOH) were blended with 30 wt.% PC. A mixture containing 70 wt.% BFS and 30 wt.% PC was used as a reference sample. The mortar was adjusted at a sand–powder (BFS-PC and/or DAS-PC) weight ratio of 3:1. The microstructural analysis proved that DAS-powder is mainly composed of sodium calcium aluminosilicate–activated species and unreacted BFS. These species can interact again with water to form calcium aluminum silicate hydrate (C-A-S-H) and NaOH, suggesting that the DAS acts as a NaOH-carrier. One-part HC mortars having 1, 2, and 3 wt.% NaOH recorded 7th day compressive strength values of 82%, 44%, and 27%, respectively, higher than that of the control sample. At 180 days of curing, a significant reduction in compressive strength was observed within the HC mortar having 3 wt.% NaOH. This could be attributed to the increase of Ca (within C-S-H) replacement by Na, forming a Na-rich phase with lower binding capacity. The main hydration products within HC are C-S-H, C-A-S-H, and chabazite as part of the zeolite family.

Herein, the possibility of including recycled glass powder as a promising material in amalgamation with slag to produce new binder materials activated by sodium silicate solution capable to resist high temperatures was studied. Slag was partially replaced with glass powder (GP) at ratios in the range of 0-15%, by weight, with a step of 5%. The powders were activated by a constant concentration of sodium silicate solution. The percentage of water absorption and compressive strength were monitored at the ages of 3, 7 and 28 days. After 28 curing days, the specimens were subjected to severe temperatures in the range of 400-1000 °C with a step of 200 °C for 2 h and the residual compressive strength was monitored. The results were analysed by X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and energy-dispersive X-ray spectra. The results revealed higher water absorption and lower compressive strength with the incorporation of GP. The incorporation of GP has a negative effect on the compressive strength of alkali-activated slag (AAS) pastes after exposure to 400 and 600 °C, whilst it has a positive effect after exposure to 800 and 1000 °C.

Hybrid cement (HC) can be defined as alkali activated-blended-Portland cement (PC). It was prepared by the addition of an alkaline solution to high-volume aluminosilicate-blended-PC. Although this cement exhibits higher mechanical performance compared to conventional blended one (aluminosilicate-PC blend), it represents lower commercial viability because of the corrosive nature of an alkaline solution. Therefore, this study focuses on the preparing one-part-HC using dry activator-based blast-furnace slag (DAS). DAS was prepared by mixing sodium hydroxide (NaOH) with blast-furnace slag (BFS) at low water to BFS ratio, followed by drying and grinding to yield DAS-powder. Different contents of DAS (equivalent to 70 wt.% BFS and 1, 2, and 3 wt.% NaOH) were blended with 30 wt.% PC. A mixture containing 70 wt.% BFS and 30 wt.% PC was used as a reference sample. The mortar was adjusted at sand: powder (BFS-PC and/or DAS-PC) weight ratio of 3: 1. The microstructural analysis proved that DAS-powder is mainly composed of sodium calcium aluminosilicate activated species and unreacted BFS. These species can interact again with water to form calcium aluminum silicate hydrate (C-A-S-H) and NaOH, suggesting that the DAS acts as NaOH-carrier. One-part HC-mortars having 1, 2, and 3 wt.% NaOH recorded 7-days compressive strength values 82, 44, and 27 %, respectively, higher than that of the control sample. At 180-days of curing, a significant reduction in compressive strength was observed within HC-mortar having 3 wt.% NaOH. This could be attributed to the increase of Ca (within C-S-H) replacement by Na, forming Na-rich-phase with lower binding capacity. The main hydration products within HC are C-S-H, C-A-S-H, and chabazite as one of zeolite family.

In the present work, sustainable use of cement kiln dust (CKD) and feldspar (FS) in the production of pozzolanic materials with different reactivity and whiteness were investigated. The proposed method includes thermal treatment of CKD and FS at 1000 °C in the presence of sodium hydroxide to convert crystalline- FS/CKD -structure to amorphous one. Different FS/CKD mixtures were designed at weight ratios of 50/50, 66.66/33.33, and 80/20 (P-1, P-2, and P-4, respectively) to optimize the whiteness and amorphous content of the produced pozzolans. A preliminary study revealed that the amorphous content and the whiteness of the prepared pozzolan strongly depend on FS/CKD weight ratio. The optimum pozzolanic materials with high 89% whiteness and 100% amorphous content were obtained in the case of P-4. The individual replacement of white Portland cement by 30 wt % of the synthetic pozzolans resulted in the enhancement of 28-days compressive strength. The use of P-4 pozzolan not only increased the mechanical properties of white Portland cement, but also enhanced its whiteness. Non-thermally treated FS/CKD blend (as the counterpart of P-4 pozzolan) showed a lower pozzolanic activity as compared with thermally treated one. Regardless of the change in the strength activity index (SAI) and the rate of Ca(OH)2 consumption, all synthetic pozzolans demonstrated a higher pozzolanic activity.

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.

A cleaner production of one-part alkali activated cement (AAC) was implemented by mixing chemically treated concrete waste (CTC) with slag. The treatment process was conducted by the addition of NaOH to concrete waste (CoW) at NaOH to CoW weight ratios of 0.2, 0.1, and 0.05 (namely, CTC-1. CTC-2, and CTC-3, respectively), followed by mixing with water and drying. The solidified material was ground then dry-mixed with slag to create one-part alkali AAC powder with fixed particle size. The amount of CTC was varied to achieve constant Na2O content (2 wt %) in all mixtures. The results indicated that the prepared one-part AACs can react with water to yield hardened materials with acceptable compressive strength. Comparing with CTC-1 and CTC-3, the CTC-2 was found to have a dominant impact on the activation of slag hydration, which associated with the higher mechanical properties, lower pore volume, and drying shrinkage. The addition of lead bearing sludge (LBS) to one-part AAC containing CTC-2 resulted in a positive impact on the performance of the prepared cement. According to toxicity characteristic leaching procedures the prepared cement showed a potential effect on solidification/stabilization of Pb-containing-sludge.

The motivation behind this work is to sustainable utilization of water-cooled steel-slag and lead-bearing sludge (LBS: from glass crystal industry) in the cleaner production of alkali activated cement (AAC) with high performance and microbial resistivity. To prepare AAC, slag was individually blended with different LBS contents (0, 10, 30, and 50% with respect to weight of slag), then activated with sodium hydroxide (NaOH). Due to high CO2 emission resulting from NaOH-manufacturing, alkali activator was used with low concentration (3 wt, %) for activating the aluminosilicate precursors. A preliminary investigation proved that the mechanical and physical properties of AAC significantly enhanced with the increase of LBS content up to 30 wt %; meanwhile, 50 wt % LBS had a negative effect. The leaching test indicated that Pb-concentrations (mg/l) in leachate of all AAC-mixtures were below the safe limit of toxicity characteristic leaching procedure (TCLP). Agar diffusion test showed that the anti-bacterial and -fungal activity of AAC enhanced with increasing LBS content up to 50 wt %. From the standpoint of environmental impact assessment, the prepared cement showed 50-times lower CO2 emission compared with Portland cement.

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.

The key point of this investigation is to valorize CaCO3-rich wood biomass ash (WBA) from brick industry in the preparation of one-part white geopolymer cement (WGPC) using diatomite as main ingredient. The suggested method not only implemented for cleaner production of eco-friendly cement, but also used to WBA disposal. In the present work, WBA was treated with different sodium hydroxide concentrations (at NaOH: CaCO3 molar ratios of 2, 1, 0.5, and 0.25), followed by dying and pulverizing to produce dry activator powder with a fixed fineness. The impact of dry activator content, containing the same NaOH content (3 wt. %), on the performance of one-part WGPC was evaluated by setting times, total porosity, and compressive strength measurements. The results revealed that the compressive strength development enhances with time, associating with the continuation of aluminosilicate (in diatomite) dissolution and formation of strength-giving-phases such as calcium silicate hydrate and calcium aluminosilicate hydrate. The synergistic filling and nucleating effects of CaCO3 were recorded when 21.5 wt.,% of pretreated WBA, at NaOH/CaCO3 molar ratio of 0.5, added to diatomite to yield one-part WGPC with optimal 28-days compressive strength (48 MPa) and relatively high whiteness (85%). This qualifies the prepared one-part WGPC to be beneficially used as alternative to white Portland cement in decorative works and prestige construction projects.

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.

This investigation studies the effects of hot water and hot air curing on the strength development, transport properties, and freeze-thaw resistance of mortars incorporating low-heat blast furnace slag cement and nanosilica (NS). Mortar samples were prepared and stored in ambient conditions for 24 h. After demolding, mortar samples were subjected to two different hot curing methods: Hot water and hot air curing (40 &deg, C and 60 &deg, C) for 24 h. For comparison purposes, mortar reference mixes were prepared and cured in water and air at ambient conditions. Strength development (from 1 to 180 days), capillary water porosity, water sorptivity, and freeze-thaw resistance were tested after 180 days of curing. The experimental results showed that both curing regimes accelerate the strength development of mortars, especially in the first seven days of hydration. The highest early strengths were reported for mortars subjected to a temperature of 60 &deg, C, followed by those cured at 40 &deg, C. The hot water curing regime was found to be more suitable, as a result of more stable strength development. Similar findings were observed in regard to durability-related properties. It is worth noting that thermal curing can more efficiently increase strength in the presence of nanosilica, suggesting that NS is more effective in enhancing strength under thermal curing.

It is well known that the chemical precipitation is regarded as an effective approach for the preparation of nano-materials. Nevertheless, it represented several drawbacks, including high energy demand, high cost, and high toxicity. This work investigated the eco-sustainable application of plant-derived urease enzyme (PDUE)-urea mixture for synthesizing Zn–/Zr–carbonates and –oxides nanoparticles. Hydrozincite nanosheets and spherical-shaped Zr-carbonate nano-particles were produced after adding PDUE-urea mixture to the dissolved Zn and Zr salts, respectively. PDUE not only acts as a motivator for urea hydrolysis, but it is also used as a dispersing agent for the precipitated nano-carbonates. The exposure of these carbonates to 500 °C for 2 h has resulted in the production of the relevant oxides. The retention time (after mixing urea with urease enzyme) is the dominant parameter which positively affects the yield% of the nano-materials, as confirmed by statistical analyses. Compared with traditional chemical-precipitation, the proposed method exhibited higher efficiency in the formation of nano-materials with smaller particle size and higher homogeneity.

An environmentally friendly alkali activated cement powder was prepared by the transformation of air cooled slag (ACS), with low reactivity, into high reactive cementitious material. The recycling process was carried out by thermal activation of ACS in the presence of fluxing materials followed by quenching and crushing to produce cement powder with a fixed particle size, yielding alkali activated cement powder, which can react with water like Portland cement. Type and content of fluxing material were investigated in this communication. The results proved that there is no change in the crystalline structure of ACS when it exposed to 1200 °C (with no fluxing materials). Meanwhile, it can convert to amorphous material with a complete vitreous structure in the presence of sodium hydroxide and feldspar. The dissolution/condensation process of the amorphous aluminosilicate initiated after adding water to the prepared cement powder, yielding hardened cement pastes with higher mechanical properties as compared to untreated alkali activated ACS.

This work aims at preparing different nano-minerals using bio-precipitation method (BPM). Nano-calcite (NC), nano-giorgiosite (NG), nano-witherite (NW) have been prepared by the addition of plant-derived urease enzyme (PDUE) to urea/CaCl2, urea/Ca(CH3COO)2, urea/MgCl2 and urea/BaCl2 solutions, respectively. Nano-Mg-calcite (NMC) was precipitated by dissolving PDUE and urea in ground water (GW). Salt type plays an important role in the morphology, crystallinity, and particle size of nano-minerals. PDUE has higher effectiveness on Ca2+ removal from GW; meanwhile, it has a lower impact on Mg2+ removal. Where, the Ca-hardness varied from 1460 to 20 mg/l after the treatment of GW with PDUE. At the same pH, the Mg-hardness (1833 mg/l) slightly reduced to be 1210 mg/l. By raising pH, using one-molar sodium hydroxide solution, the removal of Mg2+ enhances. The BPM not only used to prepare innovative NMC-mineral from GW, but also applied to reduce GW-hardness.

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.

Non-Portland cement or alkali-activated slag is regarded as non-friendly for users, due to the corrosive nature of alkaline solution. This negatively affects the mass production and commercial viability of this cement. In this work, user- and eco-friendly one-part non-Portland cement (NPC) was prepared by blending ground-granulated blast-furnace slag (GGBFS) with stable dry activator (SDA). SDA was synthesized by mixing two moles of NaOH with one mole of MgCO3 or dolomite, followed by drying and pulverizing to a fixed particle size (namely, SDA-M and SDA-D, respectively). The Mg source was chosen to prepare active magnesia with no firing. So, this process was considered as eco-friendly method for this purpose. Ordinary Portland cement (OPC) was used for comparison. The SDA-M content plays a circular role on the reduction of drying shrinkage of one-part NPC. The SDA-M has a potential impact on the compressive strength development of one-part NPC compared to SDA-D. NPC containing 12 mass% SDA-M (NPC-12) gave compressive strength values superior to those of OPC at all curing ages, suggesting that the NPC-12 can be beneficially used as an alternative to OPC as confirmed by X-ray diffraction (XRD), thermogravimetric analysis (TGA/DTG), and scanning electron microscopy (SEM).

The goal of this study is to produce an environmentally, and user friendly ready-mix alkali activated cement (RM-AAC) by thermal activation of concrete waste (CW) in the presence of sodium hydroxide (NaOH). Two major compositional factors, which play an important role in the performance of RM-AAC, i.e. temperature and NaOH percentage, were investigated. The CW showed high stability under thermal treatment up to 1200 °C; meanwhile it can be converted to distorted structure with high amorphicity in the presence of appropriate NaOH content. RM-AAC powder can react with water, forming hardened material with an acceptable compressive strength. Due to the white color of RM-AAC powder, it can be beneficially used in prestige construction projects and decorative works.

The key point of this work is to study the impact of sulfur oxidizing bacteria (SOB), namely Acidithiobacillus Thiooxidans NCIMB 8343, on the properties of eco-friendly alkali activated slag (AAS), ceramic waste (AACW) and glass waste (AAGW) industrial solid wastes. Ordinary Portland cement (OPC) was used as reference. After 14-days of curing in tap water, all hardened cement pastes were exposed to pure carbon dioxide, which decreased the pH value of hardened cement surface, allowing the bacterial attack. The detrimental impact of biogenic sulfuric acid, induced by SOB, was evaluated by measuring the cationic leaching, weight, compressive strength and total porosity variations. The change in phase composition and the morphology of cement phases was investigated by Fourier transformer infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The AAS (with low Ca/Si ratio) showed the higher resistivity against SOB attack comparing with OPC-paste (with high Ca/Si ratio) up to 360-days of incubation. On the other hand, the AAGW (containing low alumina content) exhibited biodegradable signs with higher Na-leaching rate, higher compressive strength declination and porosity increment rates as well as larger weight loss as compared to AACW (containing high alumina mass, %).

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 .