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This study used reactive ultra-fine fly ash (RUFA) as the primary raw materials in the preparation of a novel RUFA geopolymer. Note that the solution to binder weight ratio was maintained at the same level by varying the concentration of the NaOH solution. Extensive analysis was conducted to characterize the flowability and mechanical properties. X-ray diffraction (XRD), Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS), Fourier transform infrared spectroscopy (FT-IR), mercury intrusion porosimetry (MIP), thermogravimetric (TG), and zeta potential analyses were used to examine the microstructure of RUFA geopolymers. Increasing the concentration of NaOH also led to an increase in compressive strength. A high NaOH concentration of 12 mol/L resulted in compressive strength of 97.6 MPa at 28 days. Finally, increasing the concentration of NaOH increased the formation of the primary reaction geopolymerization product, N-A-S-H gel, resulting in a denser microstructure with lower porosity.

LED waste quartz sand (LEDWS), which is a prominent by product of the LED manufacturing process, may contaminate the environment because it comprises specific heavy metals (e.g., As and Cu), which are hazardous ingredients to the environment when disposed of improperly. Therefore, this study investigated the use of light-emitting diode (LED) waste quartz sand to partially replace Portland Type I cement (OPC) to evaluate the feasibility of reusing it as a pozzolanic material. The SiO2, Na2O, and CaO contents in the LED waste quartz sand were 70.37, 16.52, and 9.19%, respectively. The results showed that the LED waste quartz sand met the Taiwan EPA regulatory thresholds. Microstructure analysis techniques, such as mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) and scanning electron microscopy (SEM), were used to measure the LED waste quartz sand-blended cement paste (LEDBCP) samples. Compressive strength analysis of the pastes containing 10 wt.% LED waste quartz sand showed that the LED waste quartz sand not only acts as a pozzolanic material to increase the density of the microstructure but also improves the compressive strength of the pastes. LEDBCP with LED waste quartz sand exhibited higher intensity diffraction peaks corresponding to calcium silicate hydrate and lower intensity diffraction peaks corresponding to portlandite (CH) compared with ordinary Portland cement samples at an early age. The gel porosity and pore sizes of the LEDBCP increased with increases in the proportion of LED waste quartz sand. LEDBCP with 10-20 wt.% LED waste quartz sand provides a paste with good pozzolanic characteristics.

In this study, ultra-fine spherical particles of silica fume and reactive ultra-fine fly ash were added to a mixture of commercial ultra-high-performance grout (UHPG) with the aim of enhancing the rheological properties, compressive strength, compactness, and permeability. This commercial UHPG study was conducted in collaboration with Triaxis Corporation (Changsha city, Hunan province, China). A water-to-binder ratio of 0.21 and a binder-to-fine aggregates ratio of 1.17 were used as fixed parameters, and the binders were a combination of type-II Portland cement, sulphoaluminate cement, silica fume, and reactive ultra-fine fly ash (RUFA). Polycarboxylate superplasticizer powder was used to control the rheology. The results revealed excellent compressive strength, volume stability, and resistance to chloride penetration. Mercury intrusion porosimetry and scanning electron microscopy tests revealed that the medium-sized RUFA particles with small silica fume particles completely filled the spaces between large cement particles to achieve optimal densification. This mixture also produced dense hydration and calcium-silicate-hydrates colloids, which filled the microstructures of the UHPG resulting in excellent engineering properties and durability. This commercially available UHPG mix responded to excellent compressive strengths approaching 120 MPa and exhibited good workability with a loss of slump-flow rate up to 33% after 60 min. It also exhibited very low abrasion resistance (0.5%), stable shrinkage and expansion rates (stabilization over 10 days), very low chloride diffusion coefficient (less than 0.1 × 10−14 m2/s) with a denser microstructure. This commercial UHPG (UHPG-120) has been developed to meet the needs of the market.

The accumulation of copper tailings in China has reached 2.4 billion tons, with much, and the comprehensive use rate was only 8.2%. Natural river sand was a non-renewable in a short time. Natural river sand distribution has strong regional limits. This study was focused on prepared C30 concrete pavement with copper tailings as fine aggregate. It could not only ease the pressure of natural sand shortage but also improve the comprehensive use rate of copper tailings and reduce environmental pollution. The range of copper tailings particles was 0.15–0.075 mm, which belongs to ultra-fine sand. There were still obvious differences between copper tailing and natural sand in compositions, shape, and particle grading. In this study, copper tailings were mixed with natural river sand as fine aggregates to mix the mixture of C30 concrete. The particle graduation and MB value of mixed sand after replacement of 30 wt.% and 100 wt.% copper tailings in river sand were conducted. The effect of 0 wt.%, 30 wt.%, and 100 wt.% replacement rate on the mechanical properties of C30 concrete, dry shrinkage performance, resistance to sulfate erosion durability were studied and evaluated. The experimental results show that: 30 wt.% and 100 wt.% mixed sand has more fine aggregate, poor grading, and the measured MB value is greater than 1.4. With the increase of the content of copper tailings, the dry shrinkage rate increased to 15.94 μm, and the compressive strength decreased by 55.7%.

This study was aimed to investigate calcium fluoride sludge waste resource reuse, and explore the feasibility of calcium fluoride sludge in cement-based materials used to replace the cement. The mechanical properties and durability of cement-based materials containing calcium fluoride sludge were performed using resistance test, absorption test, initial surface absorption tests, dry shrinkage test, compressive strength test, mercury intrusion porosimetry and scanning electron microscopy observation. The results indicated that partially replacing cement with calcium fluoride sludge improved the compressive strength, permeability and pore-structure, as well as 10% replacement of cement seems to give superior mechanical properties and durability due to the denser microstructures. Such dense microstructures observed in scanning electron microscopy images and narrow pore size distribution determined by mercury intrusion porosimetry.

The vigorous promotion of reuse and recycling activities in Taiwan has solved a number of problems associated with the treatment of industrial waste. Considerable advances have been made in the conversion of waste materials into usable resources, thereby reducing the space required for waste storage and helping to conserve natural resources. This study examined the use of non-alkali activators to create bonded materials. Our aims were to evaluate the feasibility of using ground-granulated blast-furnace slag (S) and circulating fluidized bed co-fired fly ash (F) as non-cement binding materials and determine the optimal mix proportions (including embedded fibers) with the aim of achieving high dimensional stability and good mechanical properties. Under a fixed water/binder ratio of 0.55, we combined S and F to replace 100% of the cement at S:F ratios of 4:6, 5:5, 6:4. Polypropylene fibers (L/d = 375) were also included in the mix at 0.1%, 0.2% and 0.5% of the volume of all bonded materials. Samples were characterized in terms of flowability, compressive strength, tensile strength, water absorption, shrinkage, x-ray diffraction (XRD) and scanning electron microscope (SEM) analysis. Specimens made with an S:F ratio of 6:4 achieved compressive strength of roughly 30 MPa (at 28 days), which is the 80% the strength of conventional cement-based materials (control specimens). The inclusion of 0.2% fibers in the mix further increased compressive strength to 35 MPa and enhanced composite properties.

In this study, we coated fine recycled concrete aggregate (FRCA) with fly ash, slag, or polyvinyl alcohol (PVA) (viscosity: 44–50 cps), replaced 25% of the natural fine aggregate in concrete with the coated FRCA, and examined the durability and microscopic properties of the flesh concrete and hardened concrete. We then examined the effects of the various types of coating as well as the thickness on the properties of concrete. Our test results indicate that coating FRCA with fly ash or PVA increases the workability of the fresh concrete, whereas slag coatings slightly reduce the workability. Slag coatings increased the compressive strength, splitting strength, and durability of specimens to a greater degree than do fly ash or PVA coatings, regardless of the water-cement ratio. Furthermore, thicker coatings were shown to produce better results. Scanning electron microscopy images and mercury intrusion porosimetry tests verified that specimens containing FRCA coated with slag resulted in superior engineering properties.

In this study, it investigated the effects of adding a mixture of circulating fluidized bed co-fired fly ash and bottom ash on controlled low-strength material (CLSM). Experiment variables were as follows: (1) mixing of co-fired fly ash, cement, and pulverized coal fly ash in various proportions to evaluate the effectiveness of using co-fired fly ash as cementitious material in CLSM; (2) mixing of bottom ash and natural fine aggregate in various proportions to evaluate the effectiveness of using bottom ash mixture as aggregates in CLSM. The water-cement ratio of CLSM was fixed at 0.85. Assessments were conducted using a lump flow test, flow consistency test, ball drop test, chloride ion measurement, compression strength test, and length change test. Test results indicate the following: (1) increasing the replacement ratio of co-fired fly ash and bottom ash decreases flowability; (2) the addition of co-fired ash (containing chlorine), with bottom ash increases the amount of chloride ions in CLSM; (3) the addition of co-fired fly ash reduces setting time; (4) the CaO, SiO2, and Al2O3 in co-fired fly ash and bottom ash increase the compressive strength of CLSM; (5) the CaO contained in the mixture of co-fired fly ash and bottom ash causes CLSM to expand.

Recently, many people around the world have been concerned with environmental protection and sustainability. The goal of various countries&rsquo, research has been focused on how to regenerate existing resources. Circulation fluidized bed combustion (CFBC) technology is one of the emerging combustion technologies for electricity generation and produces more than 800,000 tons of CFBC fly ash (CFA) per year for combustion. CFA has been widely applied in cement additive, new building materials and cement-based materials. The goal of this study was to discuss the engineering properties of roller-compacted concrete containing CFA. Test subjects included compressive strength, flexural strength, absorption, setting time, unit weight, sulfate resistance, SEM microscopic observations and XRD ingredient analysis. Test results indicate the following: (1) using CFA as a substitute of fine aggregates up to 10 wt.% would improve the development of later flexural strength, (2) the increases in pre-pressure would increase the compressive strength and unit weight and decrease absorption, (3) using CFA would reduce the initial setting time by 30%&ndash, 60% and reduce the final setting time by 16%&ndash, 20%, (4) using CFA would reduce the absorption, (5) using CFA would reduce the unit weight by 0.5%&ndash, 2.8%, and the increases in pre-pressure would increase the unit weight by about 0.9%&ndash, 2.1%, (6) CaO in CFA helps to improve sulfate resistance, (7) scanning electron microscopy (SEM) observation shows that the increases in pre-pressure would reduce the pores, and (8) X-ray diffraction (XRD) analysis shows that the inclusion of CFA would increase the content of Ca(OH)2 in concrete.

This study examined the permeability of concrete in which a portion of the cement was replaced with reactive ultra-fine fly ash (RUFA) or silica fume. RUFA is an industrial by-product from thermal power plants, with spherical particles ranging in size from 0.1 μm to 10 μm, which is smaller than the particles in conventional fly ash. In experiments, the water-to-binder ratio was fixed at 0.45, and various proportions of the cement (5 % or 10 %) were replaced with RUFA, silica fume, or a combination of the two (5 % RUFA + 5 % silica fume, or 8 % RUFA + 2 % silica fume). The inclusion of RUFA was shown to enhance workability and promote the pozzolanic reaction resulting in the formation of C-S-H colloids. The filling of pore structures by colloids increased the compactness and compressive strength of the specimens, and reduced dry shrinkage. The inclusion of RUFA was also shown to reduce chloride ion penetration and the non-steady-state migration coefficient, which are indicative of improved mechanical properties and reduced permeability. Overall, RUFA proved superior to silica fume as a cement replacement in terms of workability, permeability, and mechanical properties.

LED waste quartz sand (LEDWS), which is a prominent byproduct of the LED manufacturing process, may contaminate the environment because it comprises numerous nanoparticles of SiO2, Al2O3, and SiC, which are hazardous ingredients that are harmful to the environment and human health when disposed of improperly. Therefore, this study investigated the pozzolanic reaction behavior of these industrial byproducts to obtain a valuable processing method for LEDWS in cement. The results showed that with increased curing time, the strength of the pastes that incorporated 10% LEDWS approached that of ordinary Portland cement. A stretching broad band was centered at 1074–1081 cm−1 from chemically bound H2O in the hydrated calcium silicate (C–S–H). Thus, the correlation between the hydration degree of the paste that incorporated LEDWS and compressive strength evolution is crucial. The results implied that LEDWS can be used as a partial replacement source for cement applications; thus, LEDWS can be used as pozzolanic material.

In this study, it evaluated the effects of sand/aggregate (S/A) ratio on the flowability, strength, durability, and microstructures of self-compacting concrete (SCC). Testing was performed on specimens using five S/A ratios: 51%, 52%, 53%, 54%, and 55%. Slump flow tests, slump tests, and box tests were used to characterize the rheological properties of the concrete as well as the mechanical properties, including compressive strength, splitting strength, slant shear strength and ultrasonic pulse velocity. Durability was evaluated using tests of absorption, resistivity and initial surface absorption. Microstructures were examined using mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). The test results indicate that a higher S/A ratio improved flowability. A greater proportion of coarse aggregate (i.e., a decrease in S/A ratio) improved the mechanical properties by 10% compared to the control specimens (S/A ratio: 52%) at 56 days. A higher S/A ratio was shown to improve bonding capacity by enhancing the roughness of the particles and thereby increasing adhesion strength. A higher S/A ratio was also shown to improve the durability of the specimens by permitting denser packing; however, a higher S/A ratio resulted in a thinner interfacial transition zone. MIP analysis did not reveal a correlation between S/A ratio and the interfacial transition zone, whereas SEM photos indicated that a lower S/A ratio reduces the size of the interfacial transition zone.

For the sake of environmental protection and circular economy, cement reduction and cement substitutes have become popular research topics, and the application of green materials has become an important issue in the development of building materials. This study developed green pervious concrete using water-quenched blast-furnace slag (BFS) and co-fired fly ash (CFFA) to replace cement. The objectives of this study were to gauge the feasibility of using a non-cement binder in pervious concrete and identify the optimal binder mix design in terms of compressive strength, permeability, and durability. For filled percentage of voids by cement paste (FPVs) of 70%, 80%, and 90%, which mixed with CFFA and BFS as the binder (40 + 60%, 50 + 50%, and 60 + 40%) to create pervious concrete with no cement. The results indicate that the complete (100%) replacement of cement with CFFA and BFS with no alkaline activator could induce hydration, setting, and hardening. After a curing period of 28 days, the compressive strength with different FPVs could reach approximately 90% that of the control cement specimens. The cementless pervious concrete specimens with BFS:CFFA = 7:3 and FPV = 90% presented better engineering properties and permeability.

This study aims to examine the mechanical properties and microstructures of steel/iron slag blended mortar (SISBM), which contains two by-products of the steel and iron industries: steel slag (basic oxygen furnace slag, BOFS) and iron slag (blast furnace slag, BFS). Test results indicate that steel slag will have effective hydration reactions with iron slag and contribute strength. The optimal mixing ratio of steel to iron slags was 3:7 (by weight), and the compressive strength was about 83.59% compared with that of ordinary Portland cement mortar (OPM). The strength development was similar to that of OPM and the strength increased as the curing period increased. The X-ray diffraction analysis results implied that the main products of hydration could be C–S–H, C–A–S–H, CaO–MgO–Al2O3–SiO2, Fe0.974O, and C4AF. The scanning electron microscope images indicated that the distribution of Ca(OH)2 and CaCO3 increased as the inclusion of steel slag increased, perhaps resulting from insufficient reactions between B...

Fiber cementitious materials are composed of fibers, pozzolan and cementitious. Addition of fibers in cementitious materials may enhance its mechanical properties, particularly tensile strength, and ductility. This project is aimed to evaluate the mechanical properties of fiber cementitious materials which comprise fibers and silica fume in the mixes. Test variables include dosage of silica fume, mix proportions, steel fiber dosage and type. Compressive strength, direct tensile strength and splitting tensile strength of the specimen were obtained through tests. Test results indicate that the splitting tensile strength, direct tensile strength, strain capacity and ability of crack-arresting increase with increasing steel fiber and silica fume dosages. The optimum composite is the mixture with 5 % replacement silica fume and 2 % fiber volume. In addition, the nonlinear regression analysis was used to determine the best-fit relationship between mechanical properties and test parameters.

This study is aimed to evaluate the tensile strength and impact resistance of cementitious materials which comprise steel fibers and silica fume in the mixes. Material variables include water-binder ratio, dosage of silica fume, steel fiber length and dosage. A designed tensile strength was used to perform the direct tensile in this study. Test results indicate that the compressive strength, splitting tensile strength and direct tensile strength of specimens for fiber length of 60 mm are higher than that of 35 mm. The inclusion of fibers in specimens containing silica fume has higher compressive and tensile strength; and lower impact resistance than the specimens made with silica fume. Incorporation of steel fiber and silica fume in composites achieves significantly higher increase in compressive strength, splitting tensile strength, and direct tensile strength than only individual use of steel fiber or silica fume and decrease in impact resistance than only individual use of steel fiber. Finally, the proposed direct tensile testing method is suitable for determining the tensile strength of fiber reinforce cementitious materials and generating the tensile stress-strain curves easily.

The pore distribution in cement mortar, which is highly related to compressive strength and permeability, vary with water-cement ratios and curing periods. This study used magnetic resonance imaging (MRI) to observe the pore distribution. Compressive strength tests, the rapid chloride-ion permeability test, and electrical resistivity tests were performed to determine the influence of pore distribution on durability. The results reveal that lower water-cement ratios and longer curing periods contributes to fewer pores in mortar specimens. SEM images illustrated how this may be influenced by the rate at which the hydration product, C-S-H colloids, is generated. In addition, the results of durability testing indicate that porosity and compressive strength, total charge passed, and resistivity display linear relationships, as porosity increases, the total charge passed increases, resistivity decreases, and compressive strength declines. The linear regression determined that the R2 of all relationships exceeded 0.90, thereby demonstrating the feasibility of applying MRI to assess the durability of concrete.

Residues of co-combustion are not addressed in Taiwan standards for fly ash use in concrete. This paper presents feasibility of re-utilizing CFB co-fired fly ash (CFFA) as an alkali activator for the eco-binder of CFFA and GGBS. The optimal mixture of the binder is specimen F3S7, which reaches 31.43 MPa that is 72.4% compressive strength of OPM at 56 days. XRD and SEM showed that CFFA activated the GGBS to generate CaO, which reacted with H2O, SiO2, and Al2O3 to form C–S–H and C–A–S–H pastes. Compressive strength reduction trend for F4S6 to F7S3 started after 28 days because high SO3 content.

This study investigates the feasibility of co-firing fly ashes from different boilers, circulating fluidized beds (CFB) or stokers as a sustainable material in alkali activators for ground granulated blast-furnace slag (GGBS). The mixture ratio of GGBS and co-firing fly ashes is 1:1 by weight. The results indicate that only CF fly ash of CFB boilers can effectively stimulate the potential characteristics of GGBS and provide strength as an alkali activator. CF fly ash consists of CaO3 (48.5%), SiO2 (21.1%), Al2O3 (13.8%), SO3 (10.06%), Fe2O3 (2.25%) and others (4.29%). SA fly ash consists of Al2O3 (19.7%), SiO2 (36.3%), Fe2O3 (28.4%) and others (15.6%). SB fly ash consists of Al2O3 (15%), SiO2 (25.4%), Zn (20.6%), SO3 (10.9%), Fe2O3 (8.78%) and others (19.32%). The mixtures of SA fly ash and SB fly ash with GGBS, respectively, were damaged in the compressive strength test during seven days of curing. However, the built up strength of the CF fly ash and GGBS mixture can only be maintained for 7–14 days, and the compressive strength achieves 70% of that of a controlled group (cement in hardening cement paste). The strength of blended CF fly ash and GGBS started to decrease after 28 days, and the phenomenon of ettrigite was investigated due to the high levels of sulfur content. The CaO content in sustainable co-firing fly ashes must be higher than a certain percentage in reacting GGBS to ensure the strength of blended cements.

This study analyzed the feasibility of ground-granulated blast-furnace slag (GGBS) and ground-granulated basic oxygen furnace slag (GGBOS) blended cements according to the standard specifications of ASTM C821-09 and ASTM C595/C595M-13. Through tests, this study verified that GGBOS can be used as alkali activators for GGBS and that the mixture proportions of S4I6 and S5I5 correspond with the physical and chemical requirements specified in ASTM C595/C595M-13. Among S3I7, S4I6, and S5I5, the mixture proportion of S4I6 exhibited the highest performance by reaching 90% of the compressive strength of ordinary Portland cement mortar.

This study focuses on the effect of the amount of silica fume addition and volume fraction of steel fiber on the engineering properties of cementitious materials. Test variables include dosage of silica fume (5% and 10%), water/cement ratio (0.35 and 0.55) and steel fiber dosage (0.5%, 1.0% and 2.0%). The experimental results included: compressive strength, direct tensile strength, splitting tensile strength, surface abrasion and drop-weight test, which were collected to carry out the analysis of variance to realize the relevancy and significance between material parameters and those mechanical properties. Test results illustrate that the splitting tensile strength, direct tensile strength, strain capacity and ability of crack-arresting increase with increasing steel fiber and silica fume dosages, as well as the optimum mixture of the fiber cementitious materials is 5% replacement silica fume and 2% fiber dosage. In addition, the Pearson correlation coefficient was conducted to evaluate the influence of the material variables and corresponds to the experiment result.

Reusing waste materials and reducing carbon emissions are crucial environmental concerns. Ground granulated basic oxygen furnace slag (GGBOS) and ground granulated blast furnace slag (GGBS) are the by-products of the steel industry and has positive effects on the environment because it reduces the problems associated waste disposal. This study reused these two products to completely replace cementitious materials, thus contributing to waste recycling, reducing the production demand for cement, and mitigating carbon emissions. Twelve mixture proportions were designed in this study, including an ordinary Portland mortar (OPM) as the control group and 11 steel/iron slag blended mortar (SISBM) experimental groups for the mechanical and cementitious characteristic experiments. The optimal mixing ratio for SISBM compressive strength ranged from GGBOS (steel slag): GGBS (iron slag) = 3:7 to 5:5 (by weight). At the age of 91 days, the compressive strength of SISBM reached 80–90% compared with that of the control group. Based on the pH values, free-CaO, and microanalysis results, the cementitious characteristics were mainly generated because the GGBOS increased the free-CaO or Ca(OH) 2 concentrations in the SISBM curing water and provided alkaline environments for Ca(OH) 2 to engage in the pozzolanic reaction with the SiO 2 and Al 2 O 3 in GGBS, forming crystals such as calcium aluminum silicate hydrate, (C–A–S–H), calcium silicate hydrate (C–S–H), and calcium–magnesium–alumina–silicate (C–M–A–S), which generated strength and strengthened microstructure.

This study is aimed to evaluate the effect of sugarcane bagasse ash fineness on the properties of cement-based composites. Three sugarcane bagasse ash contents (10, 20 and 30% by weight of cement) and three particle sizes of bagasse ash (particles less than 45, 75 and 150 μm) were used as a partial replacement for cement in mortar specimens with a constant water/cementitious ratio of 0.55. The pozzolanic strength activity test, compressive strength test and scanning electron microscope observations were conducted and compared. Test results indicated that the compressive strength decreased with the addition of sugarcane bagasse ash content increased. Addition of sugarcane bagasse ash to replace cement in cementitious composites could provide hydration and pozzolanic reaction, but it would still keep more rugged and some larger pores observed from the paste surface and resulted in the weaker microstructures and poorer properties in cementitious composites. In conclusion, the critical usage of sugarcane bagasse ash is 10 % with 45μm particles.

Rock wool is an inorganic fibrous substance produced by steam blasting and cooling molten glass. As with other industrial by-products, rock wool particles can be used as cementitious materials or ultra fine fillers in cement-based composites. This study investigated the microstructure of mortar specimens produced with cement-based composites that include various forms of rock wool particles. It conducted compressive strength testing, rapid chloride penetration tests, X-ray diffraction analysis, thermo-gravimetric analysis, and scanning electronic microscopy to evaluate the macro- and micro-properties of the cement-based composites. Test results indicate that inclusion of rock wool particles in composites improved compressive strength and reduced chloride ion penetration at the age of 91 days due to the reduction of calcium hydroxide content. Microscopic analysis confirms that the use of rock wool particles contributed to the formation of a denser, more compact microstructure within the hardened paste. In addition, X-ray diffraction analysis shows few changes in formation of pozzolanic reaction products and no new hydrations are formed with incorporating rock wool particles.

This study investigated the influence of individual constituents of calcined shale or hybrid constituents of calcined shale and fly ash or silica fume on the workability and compressive strength. Calcined shale is heat treated in a kiln and then ground to a finer powder and the calcination temperatures of 800 °C were used. The test results demonstrated that the workability and compressive strength decreased with the inclusion of calcined shale increased and the compressive strength of the specimens containing calcined shale all lower than that of the control specimens. It might be due to the higher water demand and lower CaO value. However, the hybrid batches with calcined shale and fly ash or silica fume enhanced better performance on compressive strength than individual constituents of calcined shale. The combination of 10 % calcined shale and 10 % silica fume in concrete seemed to give superior compressive strength and gave the highest value in the testing series. Finally, the inclusion of calcined shale is help to reduce the emissions of CO2and revealed an ecological advantage for concrete containing a binder blend of cement and calcined shale.

This study investigated the influence of crystalline sealers and curing environment on compressive strength, splitting strength and elastic modulus of cement-based composites. Four kinds of crystalline sealers addition (0 %, 3 %, 5 % and 7 %) were used in the concrete specimens. SEM observations were assisted in verifying the results of mechanical properties. The test results demonstrated that the specimens increased the mechanical properties with the inclusion of crystalline sealers increased. The crystalline sealers reacted with cement to produce the crystals and hydrations, which could fill with the pore and supply a denser microstructure. This appearance was verified by the SEM micrographs. In inclusion, the cement-based composites containing 7 % crystalline sealers seem to give superior mechanical properties, and make the pores become finer and enhance the durability.

This study employed Taguchi method to identify key factors influencing the protection provided by the surface treatment of reinforced concrete structures. We evaluated the protective characteristics of silicate concrete sealer (SCS) as well as its underlying mechanisms. An L12 (27) orthogonal array was produced using seven control factors and two levels to obtain the necessary data from only twelve experiments. Tests were performed to evaluate compressive strength, water absorption, and permeability. The major factors influencing the effectiveness of SCS included the water-binder ratio of the substrate, cumulative curing time of the sealer, content of pozzolanic material, and type of sealer materials. XRD analysis and SEM observation revealed the composition and efficacy of SCS in protecting concrete. The SCS reacted chemically with the cement hydration product Ca (OH)2 and filled the pore structure with C-S-H gel, which succeeded in greatly improving the mechanical properties of the concrete.

Unlike steel, tensile strength in concrete is difficult to measure through direct testing because the brittleness of concrete will often produce local failure at both ends. This study presents a new method for testing the direct tensile strength of prismatic and cylindrical specimens. Concrete specimens with water/cement ratios of 0.45, 0.55, and 0.65 were designed and cast. Two #6 rebars were arranged along the longitudinal axis of specimens. The technique measured the direct tensile strength of the concrete by producing a uniform tensile stress along the length of the specimen, and, thus, minimized misalignment and stress concentration at both ends, which is predicted from finite element method analysis. This study found that the direct tensile testing method used here was a suitable method for estimating the tensile strength of concrete. The direct tensile strength of prismatic and cylindrical specimens with equal cross-sectional areas was similar. Although tensile strength is about 1/10 of compressive...

The use of rock wool waste, an industrial by-product, in cement-based composites has positive effects on the environment because it reduces the problems associated rock wool disposal. The experiments in this study tested cement-based composites using various rock wool waste contents (10, 20, 30 and 40% by weight of cement) as a partial replacement for Portland cement in mortars. The pozzolanic strength activity test, flow test, compressive strength test, dry shrinkage test, absorption test, initial surface absorption test and scanning electron microscope observations were conducted to evaluate the properties of cement-based composites. Test results demonstrate that the pozzolanic strength activity index for rock wool waste specimens is 103% after 91 days. The inclusion of rock wool waste in cement-based composites decreases its dry shrinkage and initial surface absorption, and increases its compressive strength. These improved properties are the result of the dense structure achieved by the filling effect and pozzolanic reactions of the rock wool waste. The addition of 30% and 10% rock wool wastes to cement is the optimal amount based on the results of compressive strength and initial surface absorption for a w/cm of 0.35 and 0.55, respectively. Therefore, it is feasible to utilize rock wool waste as a partial replacement of cement in cement-based composites.

This study investigates the properties of cement-based composites with addition of various recycled rock wools and compare with the properties of composites containing fly ash and ggbs. The use of recycled rock wool is with a cylindrical and fiber-shape particle less than 75 μm. Based on the chemical composition and particle size distribution, the material properties of recycled rock wool are similar to other pozzolanic materials such as fly ash and ggbs and can be use a supplementary cementitious material. The experimental results show that partially replacing cement with recycled rock wool improves the compressive strength and porestructure, but reduce the flow spread at the high level replacement. Therefore, the test results indicate that recycled rock wool is an effective mineral admixture, with 10 % to 30 % as suitable replacement ratio of cement for the difference water/cementitious ratios.

The effect of penetrating sealer on the structure of surface pore, mechanical properties, and durability of cement-based composites was studied. Concrete specimens with various water/cement ratios (w/c=0.35, 0.45, 0.55) were cast and treated surfaced with various amounts of penetrating sealer at different ages. The effect of penetrating sealer on the mechanical properties of concrete was assessed by compressive strength. And, the rapid chloride permeability was also explored to test concrete durability. Test results indicate that the application of penetrating sealer significantly improves concrete compressive strength and chloride resistance. By using scanning electron microscopes observation, the penetrating depth of penetrating sealer can be determined and is about 2 cm. The penetrating sealer in this study may be categorized as deep penetrating sealer.

The study evaluates the properties of concrete mixed with inorganic silicate admixture. The admixture was used in proportions of 3%, 5%, and 7% of the weight of the cement. We performed tests on compressive strength and elastic modulus to evaluate the mechanical properties of concrete. Results show that the addition of the inorganic silicate admixture has a positive influence on the mechanical properties of concrete, with the best results obtained with 3% admixture. MIP porosity measurements determined that the addition of inorganic silicate admixture increased the density of the porous structure. SEM microscopic analysis revealed many needle-like protrusions into the porous structure of concrete. XRF chemical composition analysis indicated that these structures comprised mainly Na2O and SiO2. Can with cement hydration products Ca(OH)2 bring in Chemical reaction. Inferred pore structure Within be C-S-H gel of needle-like protruding structure. it can improve the main cause of mechanical properties of concrete.

This study is aimed to evaluate the tensile strength of cement-based composites which comprise polyolefin fibers and silica fume in the mixes. Material variables include water-cementitious ratio, dosage of silica fume, steel fiber length and dosage. Test results indicate that the compressive strength and direct tensile strength of specimens for fiber length of 25 mm are higher than that of 50 mm. The strength properties increase with increasing fiber content. Incorporation of fiber and silica fume in composites achieves significantly higher increase in compressive strength and direct tensile strength than only use of fiber or silica fume. In addition, the compressive strength, splitting tensile strength, direct tensile strength and impact resistance are fairly correlated. It contributes that the fiber content influences crack arresting ability and the silica fume influences interfacial bonding effectively.

The studying used different metakaolin replacement ratio of cement mortar exposed to different environments to investigate the quality of cement with metakaolin basic mechanical properties of materials and white efflorescence quantify the effect of microscopic properties. The specimens were analyzed with Compressive strength test and Matlab image analysis. The results presented that: (1) Comparing with between the appropriate amount of metakaolin replacement of cement and control group, the compressive strength of the appropriate amount of metakaolin replacement of cement is higher than control group’s. Especially, the compressive strength of 15% metakaolin replacement of cement is the highest; (2) Matlab image analysis the amount found in white efflorescence into freezers > carbon tube ≒ normal atmosphere.

This study evaluated the mechanical properties of cement-based composites produced with added polyolefin fibers and silica fume. Material variables included the water-cementitious ratio, the dosage of silica fume, and the length and dosage of polyolefin fiber. Researchers conducted tests on compressive strength, splitting tensile strength, direct tensile strength, resistivity, rapid chloride penetration, and initial surface absorption, and performed microscopic observation. Test results indicate that the specimens containing silica fume have higher compressive strength than the control and specimen made with fibers. The specimens with polyolefin fiber and silica fume have considerably higher tensile strength and ductility than the control and specimens made with silica fume. The specimens containing silica fume and polyolefin fiber demonstrated better resistance to chloride penetration than composites with polyolefin fiber or silica fume. For a given volume fraction, short polyolefin fiber performs better than its long counterpart in improving the properties of concrete. Specimens containing silica fume demonstrated a significant increase in resistivity and decrease in the total charge passed and absorption. Scanning electron microscopy illustrates that the polyolefin fiber acts to arrest the propagation of internal cracks.

The present study aimed to establish the durability indices of cement-based composites containing supplementary cementitious materials. The influences of compressive strength, permeability, and microstructure of cement-based composites containing fly ash and silica fume were discussed. The relationship between pore structure and corrosion behavior was investigated and compared. The results demonstrate that the addition of silica fume in cement-based composites resulted in a higher compressive strength, a lower absorption, a lower critical pore size, a lower chloride diffusion coefficient, and a lower corrosion rate. The composites containing 10% silica fumes performed better in permeability than composites containing 5% silica fumes, because silica fumes can narrow down the size of large capillary pores and densify the pore structure. The addition of fly ash in composites also enhanced the compressive strength and the permeability but was not as effective as silica fume. Unhydrated fly ash grains caused a looser pore structure and reduced the permeability. The combination of fly ash and silica fume enhanced the compressive strength and the permeability and specimens containing 5% silica fume and 10% fly ash had increased more in compressive strength and decreased more in permeability than specimens containing 5% silica fume or 15% fly ash. Moreover, the corrosion rate, the chloride diffusion coefficient, and the critical pore size were suitable for evaluating the durability of cement-based composites. A regression analysis found that the probability of rebar corrosion was greater than 90%, when the corrosion rate was 11.54 μm/yr, the chloride diffusion coefficient was 0.62 × 10 −12 m 2 /s, or the critical pore size was 26.71 nm.

Leaching is one of the major factors that alter the mechanical properties of cement-based composites. This study is aimed to investigate the effect of leaching on the properties of cement-based composites. Specimens with two water/cementitious ratios and two mineral admixtures were tested. An electrical potential was applied to accelerate the leaching process. Compressive strength test, scanning electronic microscopy, thermogravimetric analysis and X-ray diffraction analysis were conducted. Test results demonstrated that the calcium leaching reduced compressive strengths of concrete specimens, and such effect was prominent on the specimens without mineral admixtures. The leaching resistance increased with a decrease in water/cementitious ratio and an increase in amount of mineral admixtures. The mineral admixtures would reduce the amount of calcium hydroxide and refine the pore structure through pozzolanic reactions. A fair relationship was found between the calcium leaching and the compressive strength.

The concrete is a solid and porous composite materials, when the concrete exposure to moisture environment for a long-term, the pore water will penetrate into concrete cause hydration products leaching. Leaching of calcium ions increase in porosity and resulting in harmful ions ingress into concrete to reduce strength and durability of concrete. The purpose of this study is to evaluate the effect of water-binder ratio on calcium ion leaching behavior of cement-based material. The ammonium nitrate solution was used to accelerate leaching process. Leaching duration was 56 days, 91 days and 140 days, respectively. The leaching depth and compressive strength were measured. The results showed that leaching resistance increased with a decrease in water/binder ratio. The leaching depth showed that leaching behavior of the specimens without minerals admixtures can be divided into two stages, the first stage was leaching of calcium hydroxide and than the C-S-H gel were leaching.

This paper presents an experimental investigation on the effect of incinerator bottom ash (IBA) fineness and the cooled process of molten IBA on fresh mortar properties and compressive strength of hardened mortars. IBA with two finenesses, an original IBA, and a pulverizing incinerator bottom ash (PIBA) powder, with maximum particle size of 4.75 and 0.074 mm respectively were used to partially replace sand and Portland cement at 0%, 10%, 20%, 30%, and 40% by weight. The pozzolanic activity characteristics of powder were obtained from melting the above PIBA in an electric-furnace at 1450 °C for 1 h. and chilled by quenching in water (WIBA) and air (AIBA). Results indicate that incinerator bottom ash caused a reduction in compressive strength, unit weight, and flowability values when used as a replacement for sand and cement. However, IBA can be processed by melting to regain reactive pozzolanic activity, which may be used to partially replace cement.

This study investigates the properties of cement-based composites with addition of various rock wool wastes. The rock wool wastes are an insulating material. This study used rock wool waste with a cylindrical size distribution ranging from 17 to 250 μm, 30% of which is less than 150 μm. Rock wool waste can be used as a suitable substitute for coarse and fine aggregates, saving on the cost of natural aggregates and minimizing the environmental impact of solid waste disposal. In addition, because the composition of rock wool waste is similar to other pozzolan materials such as fly ash, ground granulated blast-furnace slag (GGBS), and silica fume, it can be considered as a supplementary cementitious material. Experimental results show that partially replacing natural aggregates with rock wool wastes improves the compressive strength, splitting tensile strength, abrasion resistance, absorption, resistance to potential alkali reactivity, resistivity, and chloride-ion penetration of cement-based composites. These improved properties are the result of the dense structure achieved by the filling effect of pozzolanic product. Pozzolanic strength activity index (PSAI) results and scanning electron microscope (SEM) observations confirm these findings. Therefore, rock wool wastes can act as either a cementitious material or inert filler in cement-based composites, depending on the particle size. The critical size appears to be 75 μm.

Basic oxygen furnace slag (BOFS) was ground to three levels of fineness as a replacement for cement at weight proportions of 10, 30, 50, and 70 wt.%. Fineness and weight proportion were shown to have significant effects on the flowability and setting time of the mortars. The expansion of BOFS mortars increased with an increase in the proportion of cement replaced, thereby exacerbating the effects of cracking. Optimal mechanical properties were achieved when 10 wt.% of the cement was replaced using BOFS with fineness of 10,000 cm2/g. The compressive strength of BOFS mortar is similar to that of ordinary Portland mortar, which makes BOFS suitable for the partial replacement of cement as a supplementary cementitious material. Scanning electron microscopy results revealed that the reaction of CaO with H2O results in the formation of C&ndash, S&ndash, H colloids, whereas the reaction of SiO2 with Al2O3 produces C&ndash, A&ndash, H colloids. The use of BOFS as a partial replacement for Portland cement could make a tremendous contribution to the steel industry and help to lower CO2 emissions.

This study aims to investigate the effect of adding circulating fluidized bed combustion (CFBC) ash, desulfurization slag, air-cooled blast-furnace slag and coal bottom ash to the controlled low-strength material (CLSM). Test methods include slump flow test, ball drop test, water soluble chloride ion content measurement, compressive strength and length change measurement. The results show that (1) the use of CFBC hydration ash with desulfurization slag of slump flow is the best, and the use of CFBC hydration ash with coal bottom ash and slump flow is the worst; (2) CFBC hydration ash with desulfurization slag and chloride ion content is the highest; (3) 24 h ball drop test (diameter ≤ 76 mm), and test results are 70 mm to 76 mm; (4) CFBC hydration ash with desulfurization slag and compression strength is the highest, with the coal bottom ash being the lowest; increase of CFBC hydration ash can reduce compressive strength; and (5) the water-quenched blast furnace slag and CFBC hydration ash would expand, which results in length changes of CLSM specimens.

In this study, the pore systems of cement‐based composites were investigated using absorption, rapid chloride penetration, rapid migration, ponding, mercury intrusion porosimetry (MIP), and scanning electronic microscopy (SEM). Direct current polarization resistance and other permeability parameters were used as indices to justify the effects of fiber and silica fume addition on the permeability of cover concrete. Cement‐based composites containing 10% silica fumes were found to have higher compressive strength, lower absorption, lower coefficient of chloride ion diffusion, lower penetration of chloride ions and higher polarization resistance than those of control specimens. Composites with a combined addition of fiber and silica fume further increased polarization resistance and compressive strength. Addition of silica fumes further improves the permeability of fiber cement composites due to the positive effect from pozzolanic reaction, which produces denser and more homogeneous structures in th...

The current study mainly investigated the influence of different tests on the abrasion resistance of concrete mixed with steel fibers and silica fume. The abrasion resistance was assessed at 28, 56 and 91 days on concretes with water-binder ratios of 0.35 and 0.55 where in some mixes silica fume was substituted by 5 % of cement by weight. Steel fibers of 0.5 % and 1.0 % of concrete volume were also added into the test concrete by replacement of coarse and fine aggregates. The results showed that concrete with higher compressive strength in Los Angeles abrasion tests also had better abrasion resistance. The inclusion of steel fibers into test concrete with a water-binder ratio of 0.35 resulted in a significant increase in compressive strength. This concrete also displayed better abrasion resistance and splitting tensile strength than reference concrete; in the test sample with a water-binder ratio of 0.55, the added steel fibers was unable to effectively produce cementation with the concrete. The inclusion of silica fume improved the abrasion resistance of concretes. In water abrasion testing, the abrasion resistance of concrete containing steel fiber was worse than that of concrete without steel fibers. In the water abrasion testing, the surface of steel fiber reinforced concrete was eroded by water and steel balls, and the impact caused the steel fibers to separate from the concrete and led to higher wear loss. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6460

Leaching of calcium ions increases the porosity of cement-based materials, consequently resulting in a negative effect on durability since it provides an entry for aggressive harmful ions, causing reinforcing steel corrosion. This study investigates the effects of leaching behavior of calcium ions on the compression and durability of cement-based materials. Since the parameters influencing the leaching behavior of cement-based materials are unclear and diverse, this paper focuses on the influence of added mineral admixtures (fly ash, slag and silica fume) on the leaching behavior of calcium ions regarding compression and durability of cemented-based materials. Ammonium nitrate solution was used to accelerate the leaching process in this study. Scanning electron microscopy, X-ray diffraction analysis, and thermogravimetric analysis were employed to analyze and compare the cement-based material compositions prior to and after calcium ion leaching. The experimental results show that the mineral admixtures reduce calcium hydroxide quantity and refine pore structure through pozzolanic reaction, thus enhancing the compressive strength and durability of cement-based materials.

This study investigated the basic mechanical and microscopic properties of cement produced with metakaolin and quantified the production of residual white efflorescence. Cement mortar was produced at various replacement ratios of metakaolin (0, 5, 10, 15, 20, and 25% by weight of cement) and exposed to various environments. Compressive strength and efflorescence quantify (using Matrix Laboratory image analysis and the curettage method), scanning electron microscopy, and X-ray diffraction analysis were reported in this study. Specimens with metakaolin as a replacement for Portland cement present higher compressive strength and greater resistance to efflorescence; however, the addition of more than 20% metakaolin has a detrimental effect on strength and efflorescence. This may be explained by the microstructure and hydration products. The quantity of efflorescence determined using MATLAB image analysis is close to the result obtained using the curettage method. The results demonstrate the best effectiveness of replacing Portland cement with metakaolin at a 15% replacement ratio by weight.