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The performance of green mortars (GMs) incorporating an eco-cement made from various proportions of rice husk ash (RHA), ground granulated blast-furnace slag (GGBFS) and circulating fluidised bed combustion fly ash (CFA) was evaluated. Different RHA contents (15 wt%, 30 wt% and 45 wt%) were used to replace GGBFS (by weight) and these mixtures were activated by 15 wt%, 20 wt% and 25 wt% CFA by the total weight of GGBFS and RHA. The engineering properties of the mortars were examined by compressive strength, splitting tensile strength, water absorption, porosity and dynamic Young's modulus tests. Sulfate resistance tests and scanning electron microscopy (SEM) were conducted to evaluate the durability and microstructure of the GMs. The test results demonstrated that the content of RHA and CFA strongly impacted the properties of the GMs. The mortars with 20 wt% CFA and

This research investigated the effects of recycled fine aggregate (RFA) and fly ash (FA) content on the strength development and engineering properties of alkali-activated slag–MgO (AASM) mortar. Various mortar specimens in which natural sand was replaced by RFA in five ratios (0:100, 25:75, 50:50, 75:25, and 100:0) and 0%, 15%, 30%, and 45% of the slag content was replaced by FA were prepared. Finally, the MgO content was fixed at a constant 7.5% of slag and FA by weight. These mixtures were activated using a solution of sodium hydroxide and sodium silicate. Strength and engineering properties, including flowability, unit weight, water absorption, ultrasonic pulse velocity (UPV), electrical surface resistivity (ESR), and rapid chloride penetration test (RCPT), were evaluated for all of the mortar samples throughout 56 days of curing time. The findings demonstrate that RFA and FA contents significantly affected the properties of mortar specimens, with RFA negatively influencing these properties and the 15% FA content specimen showing the most significant improved strength and engineering properties. Moreover, all of the AASM mortar mixtures exhibited good strength and high durability, with high UPV and ESR values as well as low-RCPT results.

Brick and ceramic wastes are becoming one of the most abundantly generated construction and demolition waste (CDWs). However, the practice of utilizing high volume brick and ceramic waste as a precursor and fine aggregate materials in alkali-activated mortar has not yet been exhaustively studied. The main purpose of this research was to analyze the possibility of recycling brick and ceramic wastes as a precursor and fine aggregate in high volume basis in the development of alkali-activated brick and ceramic mortar (AABCM) under ambient temperature. In this respect, waste brick powder (WBP) and waste ceramic sand (WCS) were used as a precursor and fine aggregate, respectively, and ground granulated blast furnace slag (GGBFS) was used to replace WBP in a range of 0–50% at increments of 10% by volume. The AABCM samples were prepared and cured at an ambient temperature for 3, 7, 28, and 56 days: the compressive strength measured in the range of 24–93 MPa and ultrasonic pulse velocity (UPV) values were between 3112 and 4086 m/s indicating AABCM samples were in good condition; both showed improvement when the proportion of GGBFS was increased. The results of this study reveal the strong potential of using brick and ceramics as precursor and fine aggregate materials on a high-volume basis to produce AABCM under ambient temperature conditions.

The main purpose of this study was to develop a high-strength alkali-activated paste using a high volume of waste red clay brick powder (WBP) and waste ceramic powder (WCP) as source materials. The reference mixes in this study were prepared using 100% WBP and 100% WCP. In the trial mixes, the WBP and WCP comprised about 60% of the total weight of the starting materials, while fly ash (FA) and ground granulated blast furnace slag (GGBFS) comprised the remaining 40%. Increments of the latter in the different trial mixes varied from 10% to 30% of the total weight. A solution of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) was used as the alkali activator. Alkali-activated paste (AAP) samples were prepared and cured at ambient temperature for 3, 7, 28, and 56 days. Workability, compressive strength, ultrasonic pulse velocity, thermal conductivity, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analyses were conducted in order to study the engineering and microstructure performance of these samples. The test results revealed that the fresh AAP mixtures were highly workable with measured slump flow values of 235–300 mm. Moreover, the hardened AAP samples obtained high compressive strength results measured in the range of 36–70 MPa. The AAP samples with WBP showed better mechanical strength performance and denser morphology than those with WCP. It is attributable to the enhancement of alkali activation of the AAP due to the finer particle size and higher CaO content of the WBP as compared to the WCP. The results of this study further demonstrate the strong potential of using recycled WBP and WCP in the production of high-strength AAP.

The present study investigates the effect of magnesium oxide (MgO) on the respective performance of water- and air-cured alkali-activated fine slag (AAS). Ground granulated blast furnace slag (GGBFS) of two different fineness levels were used to produce two AAS mixtures. These mixtures were alkali-activated with sodium hydroxide and sodium silicate and prepared into samples by adding, respectively, 2.5%, 5%, 7.5%, 10% and 15% MgO by total binder weight. A series of tests, including slump flow, setting time, compressive strength, X-ray diffraction (XRD), scanning electronic microscopy (SEM) and thermogravimetric analysis were conducted in accordance with the relevant standards. In terms of findings, the addition of MgO promoted the hydration of AAS significantly at early curing ages. Optimum MgO content was 7.5% for slag-4000 specimens and 5% for slag-6000 specimens. Cracks were observed in the water-cured AAS samples, with greater cracking at higher levels of MgO content. Moreover, the results show that the main contribution of MgO is in the hydrotalcite-like phase (Ht), where it adds volume, which improves strength the AAS paste. The effect of MgO was significantly increased in the samples that used finer-particle GGBFS. Adding MgO contributed to the more formation of hydration products, which was observed in the present study using X-ray diffraction and SEM and derivative thermogravimetric analysis.

This paper presents the results of the experimental works to investigate the use of waste limestone from water treatment industry as fine aggregate in green concrete. Two concrete mixtures with a constant water-to-binder ratio of 0.3 were prepared for this investigation, in which, the normal concrete mixture was designed following the guidelines of ACI 211 standard, while the green concrete mixture was designed using densified mixture design algorithm (DMDA) technology. For comparison, both types of concrete samples were subjected to the same test program, including fresh properties, compressive strength, strength efficiency of cement, drying shrinkage, electrical surface resistivity, ultrasonic pulse velocity, and thermal conductivity. Test results indicate that both concrete mixtures showed the excellent workability due to the round-shape of waste limestone aggregate and the use of superplasticizer. In addition, the green concrete mixture exhibited a better performance in terms of engineering properties and durability in comparison with the normal concrete mixture. The results of the present study further support the recycling and reuse of waste limestone as fine aggregate in the production of green concrete.

This paper investigates both fresh and hardened properties of concrete produced with different particle sizes of coarse aggregate (CA). The CAs with the maximum sizes (Dmax) of 25 mm, 19 mm, 15 mm, 12.5 mm, and 9.5 mm were used to produce concrete samples with a water-to-binder ratio of 0.4. The workability, fresh unit weight, compressive strength, and ultrasonic pulse velocity (UPV) of the concrete were tested. Additionally, some concrete samples were fully immersed in 5% sodium sulfate solution in order to assess the performance of the concrete under sulfate attack condition. The experimental results show that the workability of fresh concrete increased with increasing the particle size of CA used, while the particle size of CA insignificantly affected to the unit weight of fresh concrete mixtures. The concrete mixture produced with Dmax of 12.5 mm obtained the highest compressive strength and UPV values in comparison with those of other mixtures. This study also found that the compressive strength values of concrete samples that fully immersed in sulfate solution reduced about 15% as compared with those of the concrete samples cured in lime-saturated water. All of the concrete samples prepared for this investigation exhibited good durability performance with ultrasonic pulse velocity values of above 4300 m/s. Test results also indicated that the concrete properties can be enhanced if the CA sizes were appropriately selected.

The present study evaluates the mechanical-microstructural characteristics of the densified high-performance concrete (HPC) incorporating high volume fly ash (FA). The densified mixture design algorithm (DMDA) technology was applied to design the concrete proportions. The effects of various FA contents on both fresh and hardened concrete were investigated. A scanning electron microscope (SEM) was used to observe the microstructure of the concrete samples. The effectiveness of using DMDA in mix deign was also discussed in this study. As the experimental results, the FA content was found to affect the concrete properties significantly. The maximum compressive strength value of 65.1 MPa was obtained at the concrete samples containing 40% FA. Additionally, the 40% FA samples exhibited a denser microstructure as compared to the others. Generally, all of the tested concrete samples exhibited good performance in terms of workability, strength development, water absorption, and porosity. The results of this study further show the effectiveness of using DMDA technology in proportioning of the concrete mixture.

Creep and shrinkage behaviors are critical factors in the precast/prestressed concrete industry because these factors allow engineers to assess the long-term performance of concrete and to develop life-cycle estimates for concrete structures. The current study presents the results of an experimental work that addresses creep and shrinkage behaviors as well as the development of compressive strength in ordinary Portland cement concrete (OPC), high-performance concrete (HPC), and self-consolidating concrete (SCC). The concrete mixtures created for the present study were used to fabricate prestressed bridge girders. A conventional method (ACI) was used to design the mixture proportion for OPC and a densified mixture design algorithm (DMDA) was used to design the mixture proportions for HPC and SCC. All concrete mixtures had the same target strength of 69 MPa (10000 psi) at 56 days. Additionally, a comparative performance in terms of strength development and creep and shrinkage behaviors of ACI and DMDA concrete is performed in the present study. Test results show that all of the samples attained the target strength after 28 days of curing and that the strengths of each continued to increase afterward. Importantly, the incorporation of pozzolanic materials into concrete mixtures affected the propagation of creep strain and shrinkage positively. Furthermore, the DMDA concrete sample delivered better long-term performance than ACI concrete in terms of compressive strength, creep strain, and shrinkage.

This study used a sodium hydroxide (NaOH) solution to activate a mixture of water treatment sludge, fly ash, and slag, in order to produce a new alkali-activated controlled low-strength material (CLSM). Fresh properties of this new CLSM were investigated through the tests of workability, setting time, and ball drop time. Test results show that the addition of water treatment sludge (WTS) decreased workability. In addition, the addition of such WTS increased initial setting time and ball drop time, whereas the alkali equivalent (AE) shortened the initial setting time and ball drop time. At a liquid-to-solid ratio (L/S) of 0.9, a WTS content of 10%, and an alkali equivalent of 9%, the fresh properties for the CLSM conforms to the design principles and provisions of the Public Works Department, Taipei City Government, and is ideal for road construction in order to reduce traffic impact.

Thin-film transistor liquid-crystal display (TFT-LCD) waste glass can be used as a raw material for producing geopolymers, because it contains large amounts of silicon and aluminum in its amorphous structure. The setting time and compressive strength were evaluated to determine the quality of the geopolymer product with various amounts of nano-SiO2 (0% 3%) and TFT-LCD waste glass replacement (0% - 40%). The microstructures of the samples were characterized using mercury intrusion porosimetry (MIP), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The highest compressive strength and compact microstructure of the geopolymer was attained by adding 10% waste glass and 1% nano-SiO2. The results demonstrated that adding nano-SiO2 to the geopolymer substantially enhances compactness, improves uniformity, and greatly increases compressive strength. This work offers a low-cost route for fabricating geopolymers, because TFT-LCD waste glass can be used to partially substitute metakaolin in the composition of the geopolymer.

The present study evaluates the engineering properties and durability of an eco-friendly mortar that was produced using an innovative cement-free SRF binder. Samples of the binder, which incorporated ground granulated blast furnace slag (GGBFS) (S), rice husk ash (RHA) (R), and circulating fluidized bed combustion fly ash (CFBC) (F), were prepared for the present study using four different RHA/GGBFS weight ratios (0/100, 15/85, 30/70, and 45/55) and three different amounts of CFBC (10%, 20%, and 30%) as an activator. The properties of the mortar samples were evaluated using compressive strength, water absorption and porosity, ultrasonic pulse velocity (UPV), electrical surface resistivity (ESR), and sulfate resistance. The effects of RHA and CFBC contents on the properties of the mortar samples were studied. Test results showed that both the RHA and CFBC affected the properties of the mortar samples significantly. At later curing ages, the mortar samples that incorporated 20% CFBC and 30% RHA exhibited the highest compressive strength values. Furthermore, all of the cement-free mortar samples exhibited good durability, as indicated by high UPV and ESR values and high resistance to sulfate attack.

This study investigated the performance of cement-free binders incorporating ground granulated blast furnace slag (GGBFS), rice husk ash (RHA), and circulating fluidized bed combustion fly ash (CFA). Changes in packing density, water absorption, porosity, chloride penetration, and their correlations were evaluated in specimens produced using four different RHA/(RHA + GGBFS) weight ratios (0%, 15%, 30%, and 45%) and three different CFA/(RHA + GGBFS) weight ratios (10%, 20%, and 30%). The results indicate that changes in RHA and CFA proportions affected binder properties significantly. Furthermore, the high resistance to chloride penetration in the specimens support that these binders provide good durability.

The present study aims to investigate the engineering properties of foam lightweight material (FLM) that was produced using a mixture of ordinary Portland cement (OPC) and limestone powder (LP). The FLM samples were prepared with various proportions of LP (10%, 20%, and 30%) and different percentages of foam (9%, 12%, and 15%). Properties of the FLM were evaluated through the values of compressive strength, dry density, porosity, and thermal conductivity. Test results show that the foam contents affected all properties of the FLM significantly, whereas LP contents showed the insignificant effect to the FLM properties. Furthermore, the results of the present study showed a close correlation between porosity and other properties of the FLM as higher porosity resulted in lower density and thus lower thermal conductivity and mechanical strength.

The feasibility of recycling the reduction slag, limestone sludge, iron-oxide sludge, and stone sludge produced in the manufacture of cement was investigated through compressive strength testing, differential thermal and thermogravimetric analysis, X-ray diffraction, and 29Si nuclear magnetic resonance analysis. The major crystalline phases of ecocement clinkers, namely C3S, β-C2S, C4AF, and C3A, were observed. C3S content decreased and β-C2S and α-C2S content increased in the reduction slag. The compressive strength of EcoA pastes (ecocement contain 78% of limestone sludge, 19.51% of stone sludge and 2.49% iron-oxide sludge) was similar to that of commercial ordinary Portland cement. The Q0 (−70 ppm) species shifted to the Q1 (−80 ppm), and Q2 (−87 ppm) species during curing. The addition of stone sludge, iron-oxide sludge, and limestone sludge had no negative effect on the hydration of the cement pastes. In contrast, the addition of reduction slag negatively affected the formation of clinker minerals. Cement samples with reduction slag content of 1–7 wt % had lower 28-, 60-, and 90-day compressive strength than did the control mix. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 669–677, 2018

This investigation evaluates the characteristics of alkali-activated controlled low-strength materials (CLSM) that were produced using a mixture of red mud (RM) and ground granulated blast-furnace slag (GGBFS) with different RM-to-GGBFS weight ratios (100/0, 90/10, 80/20, and 70/30). A sodium hydroxide (NaOH) solution of 5M concentration was used as an activator. Characteristics of raw materials were checked carefully before using. The effects of GGBFS content on both fresh and hardened properties of the CLSM were evaluated through the tests of flowability, setting time, and compressive strength. Additionally, a scanning electron microscope (SEM) was used to examine the microstructural properties of the CLSM. Experimental results show that using more GGBFS in the mixture reduces flowability and increases the compressive strength of the CLSM. Moreover, the setting time of the fresh CLSM is associated positively with GGBFS content. Further, analysis of the optimal mixture was conducted basing on the test results. Thus, the properties of the CLSM sample containing 80% RM and 20% GGBFS conformed well to the requirements of the Public Works Department, Taipei Government, Taiwan. The results of this study further support the potential use of RM-GGBFS blends for the production of alkali-activated CLSM.

Waste materials have traditionally been discarded in landfills and often dumped directly into ecosystems without adequate treatment. However, possible reuse and recycling alternatives should be investigated and implemented. Recent environmentally friendly approaches have been aimed at achieving sustainable development by conserving natural resources and minimizing the discarding of materials. The objective of the present study was to investigate the hydration characteristics of reduction slag, limestone sludge, stone sludge, and iron-oxide sludge for fabricating four types of eco-cement clinkers. The compound raw materials were burned for 2 h at 1400°C to form eco-cement clinkers. The results showed that the major components of ordinary Portland cement (OPC), namely C3S, C2S, C3A, and C4AF, were present in the eco-cement clinkers. The compressive strength development of EcoA pastes (containing 78% limestone sludge, 19.51% stone sludge, and 2.49% iron-oxide sludge) was similar to that of the commercial OPC products. The compressive strength of the EcoD pastes (containing 71% limestone sludge, 19.51% stone sludge, 2.49% iron-oxide sludge, and 7% reduction slag) decreased as the amount of α-C2S increased. Mercury intrusion porosimetry indicated that the pore volume of the pastes gradually decreased with an increase in the curing time. Furthermore, the results of physical-mechanical tests showed that reduction slag, limestone sludge, stone sludge, and iron-oxide sludge can be used as raw materials in cement production at no cost to the producer, thereby reducing the production costs. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1466–1473, 2017

Controlled low-strength material (CLSM) is a self-compacting, flowable, and low-strength construction material that is used widely in variety construction applications. The present study evaluates the properties of CLSM that was prepared using a mixture of class-F fly ash (FA) and ground granulated blast-furnace slag (GGBFS) with the addition of three different ratios (0%, 10%, and 20% as calculated by combined FA and GGBFS weight) of waste water treatment sludge (WTS). A sodium hydroxide (NaOH) solution was used to activate these powder materials in the mixture in order to produce the alkali-activated CLSM. The effects of adding WTS on the properties of both fresh and hardened CLSM are evaluated using workability, setting time, drop ball time, unit weight, compressive strength, and toxicity characteristic leaching procedure (TCLP) tests. Moreover, a scanning electron microscope (SEM) coupled with an energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) is used to examine the microstructural properties of the CLSM. Results show that adding WTS to the CLSM samples reduces workability and increases fresh unit weight and compressive strength. Additionally, initial setting time and drop ball time are both associated positively with level of WTS content. Moreover, the liquid-to-solid (L/S) ratio and the alkali equivalent (AE) are shown to affect the properties of the CLSM significantly. The TCLP assessed leaching concentrations of heavy metals are all significantly below the regulatory thresholds that are currently allowed by the Environmental Protection Administration (EPA) in Taiwan. Finally, the properties of the CLSM sample with an L/S ratio of 0.9, WTS of 10%, and AE of 9% are found to conform well to the requirements of the Public Works Department, Taipei Government in terms of design principles and provisions.

The present study examines the effect of adding random, short coconut fibers to various cementitious composites on the mechanical properties, plastic cracking, and impact resistance of these composites. Fibers underwent a washing and boiling pretreatment prior to being added to the composite mixture. Mixtures of the cementitious composites designed by Densified Mixture Design Algorithm (DMDA) method were made using different volume fractions of random, short coconut fiber (0%, 1%, 2.5%, and 4%) and different water-to-binder (W/B) ratios (0.3, 0.35, and 0.45). Furthermore, fly ash (FA) was used to fill the void between sand particles and ground blast furnace slag (GBFS) was used to substitute for the cement in the mix proportions. A variety of tests were conducted in accordance with the relevant standards to determine the properties of these coconut fiber cementitious composites. The findings show that higher volumes of coconut fiber in the mortar tend to reduce the density and to increase the superplasticizer dosage. The addition of coconut fiber and higher W/B ratios were associated with lower compressive strength and higher absorption. The 28-day flexural strength of cementitious sheets and the modulus of rupture, respectively, increased from 5.2 to 7.4 MPa and from 6.8 to 8.8 MPa, as the coconut-fiber-to-mortar ratio ranged from 0% to 4%. Adding coconut fiber positively influenced first-crack deflection, toughness indices, plastic cracking, and impact resistance in the composites.

This article presents the results of a study on the effects of solid-to-liquid (S/L) ratio and of curing temperature on strength development, phase composition, and microstructure in geopolymers that prepared using a mixture of class-F fly ash (FA) and residual rice husk ash (RHA) and a solution of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The samples were prepared at various S/L ratios (2.4–2.8) and then cured at various curing temperatures [room temperature (RT): 90°C] to investigate these effects. A compressive strength test was conducted on the samples after the curing process to determine the development of strength over time. Moreover, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to examine the microstructural properties of the samples. Furthermore, scanning electron microscopy was used to characterize the surface morphologies of the samples. This study found that the S/L ratio and the curing temperature had significant effects on the properties of the geopolymer samples. The compressive strength of all the geopolymer samples increased with curing age. The highest strength was obtained from the samples that were prepared at an S/L ratio of 2.6 and a curing temperature of 60°C. XRD and FTIR analyses showed that the major crystalline phases presented in the resultant samples were quartz, mullite, and cristobalite with the additional presence of minor zeolite phases. The results of this study support the use of FA and RHA as solid waste materials in the preparation of geopolymers. © 2016 American Institute of Chemical Engineers Environ Prog, 2016

The present study investigates the possibility of using a blended class-F fly ash (FA) and residual rice husk ash (RHA) in the production of green building bricks through the application of densified mixture design algorithm (DMDA) in order to provide a new use for solid waste materials. This study uses unground rice husk ash (URHA) as a partial fine aggregate substitution (10–40%) in the studied cementitious mixtures. Solid bricks of 220 × 105 × 60 mm in size were prepared under forming pressure of 25–35 MPa, a curing temperature of 90 °C, and a relative humidity of 50%, for tests that assessed: compressive strength, flexural strength, bulk density, void volume, and water absorption. The test results showed that all brick samples demonstrated excellent properties. Compressive strength and flexural strength ranged, respectively, between 20.2–33 MPa and 5.4–6.9 MPa. Additionally, up to 30% of URHA content, the values of water absorption and void volume ranged, respectively, between 8.8–15.7% and 1....

This study was designed to examine the mechanical properties and durability of high-performance recycled aggregate concrete (HPRAC) containing high percentages of construction and demolition waste (CDW). In the samples, natural coarse aggregate was replaced with recycled coarse aggregate at respective ratios of 30%, 40%, and 50%, and natural fine aggregate was replaced with recycled fine aggregate at respective ratios of 40% and 50%. The concrete mixtures were designed using the Densified Mixture Design Algorithm (DMDA) method with low cement content and water binder (w/b) ratios of 0.3, 0.4, and 0.5. Concrete samples were tested for compressive strength, splitting tensile strength, ultrasonic pulse velocity (UPV), electrical surface resistivity (ESR), thermal conductivity (TC), water absorption (WA), and rapid chloride penetration and were analyzed using scanning electron microscope (SEM) micrographs for microstructure. The results support a negative relationship in concrete between CDW content and strength and durability development as well as between the w/b ratio and mechanical properties and durability. However, all of the HPRAC specimens designed in this study using the DMDA method achieved a high strength range, good durability, and stability over curing time.

This study combines various proportions of class-F fly ash (FA) and residual rice husk ash (RHA) with an alkaline solution to produce geopolymers. All of the geopolymer samples were cured at 35 °C and at 50% relative humidity until the required testing ages. The effects of the RHA content (0–50%) and of the concentration of the sodium hydroxide (NaOH) solution (8–14 M) on the compressive strength development of the samples were then investigated. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to examine the microstructural properties of the samples. Further, scanning electron microscopy (SEM) coupled with energy dispersive spectrometer (EDS) was used to characterize sample surface morphologies and compositions. Results found that the samples prepared with a NaOH concentration of 10 M and a RHA content of 35% exhibited the highest compressive strength and that increasing the NaOH concentration and RHA content beyond these values exhibited decreasing compressive strength. Chemical analysis showed that the major crystalline phases presented in the resultant geopolymer were quartz, mullite, and cristobalite. Furthermore, minor zeolite phases were detected in all of the geopolymer samples. The results of the present study support FA and RHA as promising solid waste materials for use in the production of geopolymers.

Geopolymers, which are a new form of aluminosilicates, are environmentally friendly materials that exhibit high mechanical strength. Waste catalysts that contain a large amount of amorphous SiO2 and Al2O3 are highly soluble in alkaline solutions. This study investigated the effects of the SiO2/Na2O ratio (S/N) and various levels of waste-catalyst replacement on the properties of waste-catalyst metakaolin-based geopolymers (WCMBGs). The mechanical and microstructural properties of the materials were studied by performing compressive strength testing, porosity analysis, thermogravimetric analysis, 29Si magic-angle spinning nuclear magnetic resonance (29Si MAX NMR) spectroscopy, and scanning electron microscopy. When S/N was 1.93, WCMBGs containing 10% of the waste catalyst exhibited high compressive strength and low porosity. Thermogravimetric analysis indicated that the weight loss of the materials was related to the structural composition. 29Si MAX NMR results showed that the major structure of the elements Si and Al was Q4(3Al). The experimental results indicated that waste catalyst can potentially serve as a partial replacement for metakaolin and exhibits favorable mechanic characteristics.

Using solid waste materials in the production of construction materials has received considerable attention across the world. The present study investigates the feasibility of using the densified mixture design algorithm (DMDA) method to incorporate unground rice husk ash (URHA) as a partial fine aggregate replacement (0–40%) in the production of eco-friendly construction bricks. Fly ash (FA) and residual rice husk ash (RHA) are the main binder materials considered in this study. Solid bricks of 220 × 105 × 60 mm in size were prepared in accordance with official Vietnamese product standards in steel molds under 35 MPa forming pressure. After casting, the brick samples were stored at 35 °C and a relative humidity of 50% until the ages required for testing. The brick samples were checked for dimensions and visible defects. The effects of URHA content on the engineering properties of the solid bricks, including compressive strength, flexural strength, water absorption, bulk density, and void volume, were also investigated. The test results showed that all brick samples exhibited good physical and mechanical properties. Compressive strength and flexural strength ranged, respectively, between 20.9–31.5 MPa and 5.7–6.7 MPa. All of these values were significantly better than the values required by the official Vietnamese standards. The results of this study demonstrate a significant potential for applying URHA in the production of eco-friendly construction bricks.

This study investigated foamed lightweight aggregate (FLWA) manufactured with hydrogen peroxide (HP) as a foaming agent and using cold-bonded agglomeration process, a relatively low-polluting, energy efficient method of FLWA production. A number of the types of produced FLWA were surface treated to improve the performance of the aggregates. Moreover, 8 types of FLWA were used as coarse aggregate to produce self-consolidating concrete (SCC). A variety of tests were conducted to evaluate the effects of the foaming agent and the surface treatments on the properties of the cold-bonded lightweight aggregate. The workability, unit weight, and strength of the SCC specimens were determined in accordance with established standards. The FLWA type with the lowest specific gravity was binary mixture of 80% fly ash (FA) and 20% ground blast furnace slag (GBFS) at an HP concentration of 7%, which a specific gravity 1.27. The flowability, viscosity, and passing ability of all SCC mixtures met EFNARC requirements. Finally, the findings support that using foaming agent and modifying the surface of FLWA significantly affects the strength of SCC.

In this study, the changes caused by adding a waste catalyst on the properties of the final product were investigated by applying curing on samples of waste catalyst metakaolin-based geopolymers (WCMBGs) prepared with different solid-to-liquid (S/L) ratios (0.66–0.81) and at different waste catalyst replacement levels (0–40 wt.%). The mechanical properties of WCMBG samples, such as compressive strength and porosity, were determined after the curing process. Thermogravimetric and differential thermal analysis (TG/DTA), 29Si magic-angle spinning nuclear magnetic resonance (29Si MAS NMR), and scanning electron microscopy (SEM) were also used to determine their microstructural properties. When the S/L ratio was 0.76, WCMBG samples contained 10% waste catalyst exhibited greater compressive strength and lower porosity which were comparable with pure metakaolin samples. The TG/DTA results indicated that WCMBG samples contained 10 wt.% waste catalyst had more structural water and geopolymer gels. The results of 29Si NMR spectroscopy of the samples showed that the major structures of the Si and Al are Q4(3Al) and Q4(2Al), and strong resonances were between −85 and −95 ppm, respectively. Furthermore, the waste catalyst was the compromising resource material in preparing geopolymers.

This study examined the characteristics of geopolymer with solar panel waste glass. After 28 days of curing, the compressive strengths of the geopolymer samples containing 10 mass % and 20 mass % solar panel waste glass were 63.3± 1.8 and 49.1 ± 2.2 MPa, respectively. The geopolymer sample with 10% solar panel waste glass exhibited a stronger reaction than that with 20% solar panel waste glass, and the strength decreased as the amount of solar panel waste glass increased. Thermo-gravimetric and differential thermal analysis (TG/DTA) results showed that the mass loss of geopolymer after heating declined as the amount of solar panel waste glass increased. The principal peaks in the Fourier transformation infrared spectroscopy (FTIR) spectra correspond to the Si-O-Al bond in geopolymer. Scanning electron microscopy (SEM) observations indicated that the microstructures of the stronger samples were more homogeneous, and the microstructures of geopolymer with 10% solar panel waste glass did not exhibit substantial deterioration. The experimental results indicate that solar panel waste glass has the potential to serve as a partial replacement of metakaolinite and exhibits favorable mechanic characteristics.

The purpose of this study is to co-sinter washed-fly ash, limestone sludge, stone sludge, and iron-oxide sludge to fabricate 4 types of eco-cement clinkers. The compound raw materials were burned for 2 h at 1400°C to form the eco-cement clinkers, all of which met the toxicity characteristic leaching procedure requirements. The results show that the major components of ordinary Portland cement (OPC), C3S, C2S, C3A, and C4AF, were present in the eco-cement clinkers. The compressive strength development indicated that the EcoA pastes were similar to those of commercial OPC products. The compressive strength in the EcoG pastes decreased because of the amount the α-C2S increased. The mercury intrusion porosimetry results showed that the pore volume in the pastes gradually decreased when the curing time increased. Additionally, from the X-ray diffraction results, all the eco-cements produced Ca(OH)2 during hydration, which also increased with curing age. The scanning electron microscopy images of OPC and EcoA pastes showed that the pore volume decreased and the denser structural increased with the curing time increased. In addition, adding higher amounts of 1% washed-fly ash caused to increase the content of α-C2S. The result show that this co-sintered process from 1% washed-fly ash and 99% waste sludge (77% limestone sludge, 19.51% stone sludge and 2.49% iron-oxide sludge) to produce eco-cement with excellent mechanical characteristics. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 964–972, 2015

Effects of polypropylene (PP) fibers, steel fibers (SF) and hybrid on the properties of high-strength fiber reinforced self-consolidating concrete (HSFR-SCC) under different volume contents are investigated in this study. Comprehensive laboratory tests were conducted in order to evaluate both fresh and hardened properties of HSFR-SCC. Test results indicated that the fiber types and fiber contents greatly influenced concrete workability but it is possible to achieve self consolidating properties while adding the fiber types in concrete mixtures. Compressive strength, dynamic modulus of elasticity, and rigidity of concrete were affected by the addition as well as volume fraction of PP fibers. However, the properties of concrete were improved by the incorporation of SF. Splitting tensile and flexural strengths of concrete became increasingly less influenced by the inclusion of PP fibers and increasingly more influenced by the addition of SF. Besides, the inclusion of PP fibers resulted in the better efficiency in the improvement of toughness than SF. Furthermore, the inclusion of fibers did not have significant effect on the durability of the concrete. Results of electrical resistivity, chloride ion penetration and ultrasonic pulse velocity tests confirmed that HSFR-SCC had enough endurance against deterioration, lower chloride ion penetrability and minimum reinforcement corrosion rate.

An alkali-activating solution plays an important role in dissolving Si and Al atoms to form geopolymer precursors and aluminosilicate material. This study explores the effects of the SiO 2 /Na 2 O molar ratio (1.0–2.0) on the properties of nano-SiO 2 metakaolin-based geopolymers. The setting time, compressive strength, mercury intrusion porosimetry (MIP), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) are investigated to study the properties of the geopolymers. The results show that the compressive strength increased, and that the products of geopolymerization filled pores with curing time, causing the microstructure to become dense. Moreover, a nano-SiO 2 metakaolin-based geopolymer sample with a SiO 2 /Na 2 O ratio of 1.5 exhibited more strength, higher density, and less porosity. Applying the nano-SiO 2 to a geopolymer enhances compactness, improves uniformity, and increases strength.

The mechanical characteristics and structural properties of the products of alkali-activated metakaolin reactions are affected by the raw material composition and the concentration of alkali activator used. This study quantitatively analyzed the effects of the solid-to-liquid ratios and nano-SiO 2 additions on the mechanical characteristics and flexural strength of metakaolin-based geopolymers to obtain optimal geopolymer proportions. The weight and short-range network ordering of samples were examined using a thermogravimetric analyzer and 29 Si magic-angle spinning nuclear magnetic resonance. Nano-SiO 2 particles with the average particle size of 10 nm were added up to 3 wt% to the geopolymer system and could accelerate the geopolymerization as a result of increased geopolymer gels amount and hence increased the flexural strength. The results show that a metakaolin-based geopolymer sample with a solid-to-liquid ratio of 1.03 containing 1% nano-SiO 2 exhibited higher strength, higher density, and lower porosity than other samples. These characteristics are essential for understanding the mechanical strength, thermal stability, and fundamental structure of geopolymer systems. The results also indicated the potential for nanotechnology geopolymer applications.

In this study, wet sewage sludge was used as the principle material and waste glass used as the additive to manufacture lightweight aggregate (LWA). The effects of different mass ratios of waste glass to sewage sludge and sintering temperatures on the aggregate properties were investigated. The selected LWA was used as coarse aggregate for producing lightweight concrete (LWC) with high workability. Results showed that the used of waste glass improved sintering temperature, decreased water absorption and increased failure point loading and bulk density of aggregate. The addition of 30–50% of waste glass produced the high quality LWA with bulk density lower than 2 g/cm3, water absorption lower than 10% and failure point loading as high as 892 N. Workable lightweight concrete with the 28-day compressive strength of 49 MPa was obtained. Results of surface resistivity and ultrasonic pulse velocity of LWC indicated that the produced LWC could be considered as good quality concretes.

The objective of this paper is to compare the performance of concrete containing fly ash and slag under different water-to-cementitious materials ratios and different cement paste content. The densified mixture design algorithm (DMDA) was applied in the concrete mix design. Concretes designed by DMDA with excellent flow-ability and without bleeding and segregation were obtained. The proper paste amount the better the workability and the less the workability loss. On the basis of sufficient paste amount condition, the study discovers that the less the cement paste amount as well as the denser the blended aggregate, the lower the early-age compressive strength will be, on the contrary, the higher the long-term compressive strength becomes. To design of good quality concrete, the amount of cement paste and water should be minimized as low as possible to obtain the high ultrasonic pulse velocity.

Thin-film transistor liquid crystal display (TFT–LCD) waste glass comprises mainly SiO2 and Al2O3, which are suitable raw materials for geopolymer. This study investigates the effects of the amount of foam agents on the properties of waste glass-based cellular geopolymer. In this investigation, samples underwent a series of tests to determine their quality, including mechanical characterization, compressive strength, flexural strength, fire resistance, thermal conductivity, Fourier transform infrared spectroscopy, and scanning electron microscopy. The experimental results show that the mechanical strength and thermal conductivity decreased with the addition of foam agents, indicating that foam agents can reduce the thermal transfer. The pore volume increased with the amount of increase in foam agent. These results indicated that the amount of foam agent has a more substantial effect than waste glass replacement in geopolymers. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 538–550, 2014

This investigation examines the chemical and physical behaviors of waste catalyst (WC), a byproduct of the petroleum refining industry, used as a component of cement-based materials. WC was recycled as a pozzolanic material partially to replace cement to enhance the pozzolanic activity of pastes contained WC. Fourier transformation infrared spectroscopy (FTIR), differential thermal and thermogravimetric analysis (DTA/TGA) and 29Si magnetic angle spinning/nuclear magnetic resonance (29Si MAS/NMR) approaches were adopted to relate both the hydration products of pastes contained WC and the structural features to its cementitious activity. The cementitious activity of WC was evaluated by testing the compressive strength of blended cement pastes. The results demonstrate that the blended cements that contained 10% WC exhibited favorable cementitious activity owing to the formation of C-S-H C-A-H and C-A-S-H materials in the hydration products, and an increase in densification. The substitution of cement by WC would have an additional positive environmental impact because it would permit the recycling of a byproduct of the refinery industry in Taiwan that otherwise would remain in the environment as a waste product. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 353–358, 2014

This paper focuses on the application of Fuller`s ideal gradation curve to theoretically design blended ratio of all solid materials of high performance concrete (HPC), with the aid of error function, and then to study the effect of rice husk ash (RHA) on the performance of HPC. The residual RHA, generated when burning rice husk pellets at temperatures varying from 600 to , was collected at steam boilers in Vietnam. The properties of fresh and hardened concrete are reviewed. It is possible to obtain the RHA concrete with comparable or better properties than those of the specimen without RHA with lower cement consumption. High flowing concrete designed by the proposed method was obtained without bleeding or segregation. The application of the proposed method for HPC can save over 50% of the consumption of cement and limit the use of water. Its strength efficiency of cement in HPC is 1.4-1.9 times higher than that of the traditional method. Local standards of durability were satisfied at the age of 91 days both by concrete resistivity and ultrasonic pulse velocity.