Water Binder Research Articles

CO2 uptake model of limestone-powder-blended concrete due to carbonation

In this study, a model for evaluating the CO2 uptake rate of plain concrete and limestone-powder-blended concrete in both the service and recycling phases was proposed. First, a blended cement hydration model was proposed to evaluate the content of carbonatable substances, porosity and carbon dioxide diffusivity. In the service phase, a one-dimensional carbonation model was proposed to evaluate the carbonation depth. In the recycling stage, an unreacted core model was proposed to evaluate the carbonation process of spherical recycled concrete. Secondly, considering the concrete materials, structural elements and environmental exposure, a CO2 uptake model at the service stage and recycling stage was proposed. The total CO2 uptake rate is the sum of the CO2 uptake rates in the service stage and the recycling stage. The analysis results showed (1) as the limestone replacement rate increased from 0% to 20% (water–binder ratio is 0.3), the CO2 uptake rate in the service phase increased from 3.12% to 3.84%, and the total CO2 uptake rate increased from 22.82% to 26.11%. (2) Given a certain concrete mixture, as the surface area to volume ratio of structural units increased, or the amount of recycled concrete decreased, the CO2 uptake rate increased, but the total CO2 uptake rate did not change. (3) Given a certain limestone powder replacement ratio, as the water/binder ratio increased, the total CO2 uptake ratio increased. The contributions of this study are 1) propose an integrated hydration-carbonation-CO2 uptake model for limestone blended concrete, 2) clarify the differences of carbonation equations between service stage and recycling stage, and 3) determine the effects of concrete mixtures, structural element sizes and types, life cycle stages, and recycled concrete sizes on CO2 uptake.

Exploration Testing on High-Performance Cement-Based Materials Using Granulated Blast Furnace Slag as Fine Aggregates

This study investigates the feasibility of using granulated blast furnace slag (GBFS) as fine aggregates for high-performance cement-based (HPCB) materials. The mixture ratio of HPCB materials using GBFS as fine aggregates is calculated based on the dense packing theory of aggregates and the minimum water requirement. A series of cement-based material mixes are prepared with three water binder ratios (0.16, 0.18, and 0.2) and three GBFS replacement ratios (0%, 50%, and 100%). Various properties of the cement-based materials, such as the compressive strength, flexural strength, splitting tensile strength, and elastic modulus, are studied. The research on the selected HPCB material compositions using scanning electronic microscopy (SEM), hardened concrete pore structure determination (HCPD), and mercury intrusion porosimetry (MIP) enables a further understanding of the relationship between the mechanical properties and microstructures. The test results show that it is feasible to produce HPCB materials using GBFS as fine aggregates. Despite its large crushing value index and irregular particle shape, GBFS has hydraulic properties that can make up for these disadvantages. GBFS and mixed fine aggregate cement-based materials with good properties can be prepared with a reasonable mix design. The strength of such cement-based materials is consistent with that of ordinary quartz sand (QS) fine aggregate cement-based materials. The compressive, flexural, and splitting tensile strengths of GBFS and mixed fine aggregate cement-based materials may be higher than those of ordinary QS fine aggregate HPCB materials. The relationship between the compressive strength and porosity is in agreement with the formulas proposed by Powers, Ryshkevitch, Schiller, and Hasselman.

Experimental and statistical evaluation of rheological properties of self-compacting concrete containing fly ash and ground granulated blast furnace slag

This study examines an attempt to produce self-compacting concrete (SCC) containing fly ash (FA), ground granulated blast furnace slag (S) and both (FA + S). The effects of these materials on the rheological properties of the SCC mixes were studied experimentally. The study began with three groups of SCCs, each with 25% water binder (w/b) and 550 kg/m3 total binder content. Instead of superplasticizers (SP), the chemical admixtures were lignosulphonates (LS), which replaced Portland cement (PC) at levels by weight of 10%, 20%, 30% 40%, 50%, and 60%. The fresh properties of the mixtures were examined experimentally for slump flow diameter, T50 time, V-funnel time, and L-box height ratio. In the mixtures with FA alone, a continuous decrease was observed in compressive strength. Increases in strength ended at 40% in the case of FA alone, and 30% for both the S and FA + S mixes. Statistical analysis was carried out to assess the effect of experimentally substituted materials FA and S, with results showing that S had a greater influence than FA on T50 time, V-funnel, L-box height ratio, and compressive strength, while FA had more effect than S on the slump flow diameter test.

A review study on sustainable development of ultra high-performance concrete

<abstract> <p>A systematic literature review was undertaken in this report to illustrate the development concepts and properties of ultra-high performance concrete (UHPC). UHPC's affluent development relies on its compositional content, water–binder (w/b) ratio, and design mix approach, which contributes to denser and comparatively more homogeneous packaging of particles. Numerous research studies from around the world were used to compile a database on UHPC mechanical and durability properties. Moreover, the results of this study reveal that the curing conditions, aggregates, fibre dosage and characteristics, and curing time are the most important elements in determining the mechanical and durability qualities of UHPC. Furthermore, due to its ultra-high-strength features, superior fatigue behavior, and extremely low porosity, UHPC is considered a practical and long-term alternative for improved sustainable building, resulting in increased resilience to hostile environments. Besides that, attempts are being taken to resolve existing challenges (such as high initial costs, a lack of skills, and a lack of design code) and their solutions to their widespread economic use. This study aims to help architects, builders, and other construction stakeholders better grasp UHPC's basic features and capacities, which will help to understand this durable and long-lasting building material.</p> </abstract>

Анализ влияния плазменной активации на энергию поверхности волокон сверхвысокомолекулярного полиэтилена, на прочность волокон и армированных волокнами композитов

Completely saturated chemical bonds in ultrahigh-molecular-weight polyethylene (UHMWPE) fibers — are a reason for their low surface energy (FSE), i.e. inert properties. Elongated crystal structure of UHMWPE molecules ensures high anisotropic tensile strength of the fibers. An inertness is a problem for utilization these fibers in high-strength composites production. Surface energy (SE) difference of the fibers and a binder in fiber/matrix system hinders chemical interaction at interphase boundary and worsens fiber wettability. Increase in their FSE is a topical task for this problem decision. Necessary condition of FSE increase is the integrity of molecule structure, lying under modified surface. Low temperature, nonequilibrium plasma (LTP) treatment in a medium of argon and argon/propane mixture, used in this work for plasma activation of fibers’ surface, permits to abide by this condition. However, plasma ion bombardment during a process of activation can modify interior crystal structure and, as a result, decrease their strength. The rovings SK75 (Holland) and D800 (China) were used for study of the properties of UHMWPE fibers after plasma treatment. Activation effect on FSE, strength, and fibers’ wetting by water and epoxy binder before and after ageing was studied. Capillary wetting of the fibers by distilled water used for FSE evaluation. The data of filaments surface structure and their diameter change at maximal load, obtained by optical microscope study, were used for the analysis of FSE and epoxy matrix effect on the strength of fiber/matrix systems. Essential distinction of SK75 and D800 fibers properties is ascertained. Negative effect of fibers’ and matrix’s stiffness, as well as increased FSE of stiff fibers on the strength of fiber/matrix system is revealed.

Preparation and properties of recycled fine powder foam concrete

With the rapid development of the construction industry brought by the accelerated process of urbanization, the problem of random stacking and landfill of waste concrete can be seen everywhere, which seriously affects the environmental health. The secondary utilization of waste concrete as recycled aggregate has become a research hotspot. This paper mainly studies the influence of the cementing material system of recycled fine powder foam concrete on the water absorption performance of recycled fine powder foam concrete, and explores the feasibility of using recycled fine powder to prepare foam concrete. The experiment also used recycled fine powder instead of some cement to prepare foam concrete. The effects of the amount of recycled fine powder, the amount of hydrogen peroxide and the ratio of water to binder on the compressive strength, water absorption, thermal conductivity and microstructure of the foam concrete were studied. The results showed that the water absorption rate of recycled fine powder foam concrete increased with the increase of red brick powder content, but the water absorption rate gradually increased. When the content of hydrogen peroxide is 6%, the ratio of water to binder has a greater influence on the thermal conductivity of foam concrete. When the amount of hydrogen peroxide is higher, the influence of water binder ratio on thermal conductivity decreases.

Water permeability, strength and freeze-thaw resistance of crumb rubber-modified permeable concrete brick based on orthogonal test

Permeable concrete brick (PCB), as a new type of pavement material, is commonly used in sidewalks and parks owing to its environmental benefits. Crumb rubber, as an excellent pavement materials modifier, has many advantages in improving freeze-thaw durability of PCB. In this paper, a kind of rubber-modified permeable concrete brick (RMPCB) was prepared. The effects of water-binder ratio, designed porosity and crumb rubber content on compressive strength, split tensile strength, permeability coefficient and freeze-thaw durability of RMPCB were studied. Nine groups of tests were carried out by orthogonal design; range analysis and variance analysis were used to investigate the effect of three factors (water binder ratio, designed porosity and crumb rubber content) on the test results of RMPCB. The results show that porosity is the dominant factor in the properties of permeable bricks. Higher porosity can significantly increase the permeability coefficient of RMPCB, but weaken its strength and freeze-thaw durability. The split tensile strength and freeze-thaw durability of RMPCB are positively affected when crumb rubber content is 4% of the weight of cement. With the increase of water-binder ratio, the compressive strength of RMPCB first increases and then decreases, but the effect of water-binder ratio on other properties is not significant. The optimal water-binder ratio, design porosity and crumb rubber content for RMPCB are 0.30, 15% and 4%, respectively.

An experimental study on the flexural behavior of RC member under long-term calcium leaching degradation

ABSTRACT Calcium leaching degradation could be happened in RC members due to the contact with pure water in underground conditions. And it is used that concrete with improved durability by using mineral admixture in the underground structures. Thus, it is needed to evaluate the resistance of calcium leaching for underground concrete mixed with mineral admixtures. In this study to evaluate the effects of long-term calcium leaching on the RC members mixed with mineral admixture are investigated. From the test results, when the RC member is attacked by calcium leaching, the yield load decreased, and the deflection at this time increased. And, the moment at the time of the inflection point of curvature decreased as well. Also, while a continuous decrease in compressive strength occurred with leaching period, the yield point and deflection value of an RC member with relatively low water binder ratio and low replacement ratio of mineral admixture as binder did not show significant changes. Consequently, when the concrete is applied to the underground structure which is exposed to a calcium leaching environment, it is not desirable to use high water-binder ratio or a large amount of mineral admixture as binder.

The effect of trio-fiber reinforcement on the properties of self-compacting fly ash concrete

Present study is aimed to investigate the mechanical and durability properties of trio-fiber self-compacting concrete (TFSCC) containing fly ash. Self-compacting concrete was produced in all experiments with a water binder ratio of 0.38%, steel fiber and brass-coated steel fiber rate of 2% and polypropylene fiber added in the rates of 0%, 0.05% and 0.1%. In the scope of the study, fresh concrete experiments were performed such as flow diameter and flow time to 50 cm diameter (t50), V-funnel flow time, L-box and J-ring. Hardened concrete tests were performed for mechanical properties such as compressive strength, tensile splitting strength, flexural strength, ultrasonic pulse velocity. Additional tests were conducted in terms of durability e.g. to determine the impact of high temperature (ultrasonic pulse velocity and compressive strength at 200, 400 and 600 °C), freeze–thaw test (weight loss, ultrasonic pulse velocity and compressive strength in 50, 100 and 300 cycles) and high–pressure capillarity tests. Microstructures of the concrete samples were examined by taking their SEM images. It was observed that as the rates of steel and polypropylene fibers increased in the mixes, the flow diameter decreased while it increased with the increasing rates of fly ash and brass coated steel fiber. It was also seen that as the rate of polypropylene fiber in the mixes increased, losses in resistance to freeze–thaw impact decreased. It was determined when considered micrographs taken using SEM that fly ash provides favorable effects on concrete like forming full compactness at micro level and CSHs by binding calcium hydroxide and resulting in adherence on interfaces.

Pore Structure, Morphology, and Strength of Self-Compacting Foam Material Backfilled Behind the Underground Pipe-Wall of Yellow River.

The backfill material for the underground pipe wall of Yellow River embankment was developed to avoid the high settlement and environmental damage caused by high filling and excavation. The interrelation between microstructure and compressive strength of the self-compacting foam backfill material with different water–binder ratios and density grades was investigated. The results indicated that the average pores size of the foam backfill material increased with increasing the water–binder ratio. Moreover, the compressive strength of the foam backfill material first increased and then decreased with continuously increasing the water–binder ratio. Based on the observation and the analysis of the computed tomography (CT) image, it can be found that the pore size of the foam backfill material decreased with the increment of the density grade. The overall findings demonstrated that the pore size and volume played an important role in affecting the performance of the foam backfill material used for the construction of the underground pipe wall of Yellow River embankment.

HPC produced with CDW as a partial replacement for fine and coarse aggregates using the Densified Mixture Design Algorithm (DMDA) method: Mechanical properties and stability in development

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.

Effect of Microsilica on Strength and Microstructure of the GGBS-based Cement composites

Cement production requires substantial energy and significantly accounts for global carbon dioxide emissions. Thus, the consumption of ordinary portland cement (OPC) must be reduced through incorporation of auxiliary materials. Also, the mechanical strength and durability of structures, in the construction industry, need to be improved for economizing the maintenance cost and increasing the service life. This study explores the effect of partial substitution of cement by granulated blast furnace slag (GGBS), and microsilica (MS), the industrial by-products. This study focuses on the use of 10% GGBS and 0-16% MS as a substituent of cement at a water binder ratio of 0.42. The fresh properties were determined to study the effect of these substituents. The compressive strength of all the mixes was determined after 3, 7, 28, and 56 days of treatment. The results were correlated through microstructural analysis. The study revealed that the cement composites with an optimal substituent dosage of 10% GGBS and 12% MS can attain adequate compressive strength and can be used for practical applications.

A New Method for Predicting the Ingredients of Self-Compacting Concrete (SCC) Including Fly Ash (FA) Using Data Envelopment Analysis (DEA)

Self-compacting concrete (SCC) is a liquid mixture appropriate for putting in structures with excessive reinforcement without vibration. The application of SCC has found wide use in practice. However, its application is often limited by lack of knowledge on mix material gained from laboratory tests. This paper presents a nonparametric mathematical method for the design of SCC mixes containing fly ash, which called as data envelopment analysis (DEA). DEA have the ability to estimate a set of units (a unit is consisted of multi-input–multi-output), in order to determine their efficiencies. To create DEA models, a database of experimental data was collected from the technical literature and applied. The data applied in the data envelopment analysis approach are organized in a format of six inputs parameters that contain superplasticizer, coarse aggregates, fine aggregates, water–binder ratio, fly ash replacement percentage, and the total binder content. Four outputs parameters are predicted based on the DEA method as the V-funnel time, the slump flow, the L-box ratio, and the cylindrical compressive strength at 28 days of SCC including fly ash. In this paper, we predict the optimal level of input required to produce the level of output required by SCC using DEA. To validate the usefulness of the suggested model and better its proficiency, a comparison of the DEA model with other investigator’s empirical results and other models results such as ANN was performed, and a good assent was gained.

Stress–Strain Relationship Model and Gray Entropy Analysis of Recycled Coarse Aggregate Concrete

Abstract In this research, the effects of recycled coarse aggregate (RCA) gradation (5–10 mm, 5–16 mm, 5–20 mm, and 5–31.5 mm), RCA content (30 %, 50 %, and 70 %), fly ash content (10 %, 20 %, and 30%) and water–binder ratio (0.35, 0.4, and 0.45) on the stress–strain constitutive relationship of recycled aggregate concrete (RAC) were analyzed. For this purpose, 45 prism specimens were designed, and then it was obtained by gray relational entropy analysis that the water–binder ratio and RCA content have a considerable influence on RAC’s mechanical and energy absorption properties. A mathematical expression for the stress–strain constitutive relationship of the RAC concerning the four aforementioned factors was developed through experimental investigation and regression analysis. The proposed model is compared with the experimental date, and the result has a good fit.

Experimental study on durability characteristics of composite fiber reinforced high-performance concrete incorporating nanosilica and ultra fine fly ash

This study is aimed at investigating the durability properties of Composite Fiber Reinforced High-Performance Concrete. A 15% partial replacement of cement by weight was done with ultra-fine fly ash. The addition of nanosilica was in fractions of 0%, 1.5%, 3.0% and 4.5% by weight of cement. For each of the above combinations, 1.0% steel and 0.25% polypropylene fibers, respectively, by volume of the binders were added. A constant aggregate binder ratio of 2.0 and varying water binder ratios of 0.275, 0.300, 0.325 were used in this investigation.The sorptivity test was performed to assess the rate of absorption, and the rapid chloride permeability test (RCPT) was performed to assess the permeability of concrete. Test results revealed that all the mixes attained low to very low chloride permeability. The decrease in chloride ion permeability for mixes with nanosilica and ultra-fine fly ash ranged from 53.83% to 71.45% for 28 days curing period and 55.88% to 74.27% for 56 days curing period, as against the reference mix.‘Residual Compressive Strength’ and ‘Percentage Weight Loss’ for 28 and 56 days of immersion in 5% concentrated solutions of HCl, H2SO4, and MgSO4 were evaluated to study the effects of aggressive ions such as chlorides and sulfates on concrete. The weight loss observed ranged from 7.09% to 2.07% in the case of HCl, from 7.96% to 2.86% in the case of MgSO4, from 17.93% to 11.02% in case of H2SO4 for water binder ratio of 0.275 and 56 days of immersion. The percentage reduction in strength after 56 days of immersion for mixes with water binder ratio of 0.275 ranged from 14.39% to 8.92% in HCl, from 14.53% to 9.66% in MgSO4 and 14.81% to 10.92% in H2SO4.The outcomes of the study showed that a combination of 15% ultra-fine fly ash and 3% nanosilica is the optimum replacement level to achieve increased durability, reduced porosity and permeability due to improved macro and micrometer densities of concrete. In addition, steel and polypropylene fibers have also made a small contribution towards improving the durability of Composite Fiber Reinforced High-Performance Concrete.

Application of Low-Field NMR to the Pore Structure of Concrete

In the present study, we used low-field nuclear magnetic resonance (LF-NMR) measurements and mercury intrusion porosimetry (MIP) to evaluate the influence of the water–binder (w/b) ratio, fly ash (FA) replacement and curing regimes on the pore structure of concrete. The main advantage of LF-NMR is that it is nondestructive and suitable for large concrete samples compared with other traditional methods, such as MIP, adsorption methods and scanning electron microscopy methods. Hence, the LF-NMR relaxometry method measures the pore structures that are closer to reality. The LF-NMR relaxation time, T2, represents the change in the pore structure during the hydration and hardening processes of concrete. The results showed that the T2 spectrum of the concrete sample was mainly composed of 3–5 signal peaks. Additionally, the w/b ratio, FA replacement and the curing regimes have significant effects on the T2 spectrum, porosity, and pore size distribution of concrete. In addition, the compressive strength of concrete has a close relationship with its pore structure. Based on the LF-NMR test results, the relationship between the compressive strength and the porosity, pore size distribution of concrete was established.

Study on the basic performance of basic magnesium sulfate cement concrete

The influence of multiple factors – namely, cement type, cement strength grade, cement content and water–binder ratio – on the basic performance, including the slump and early compressive strength, of basic magnesium sulfate (MgSO4) cement (BMSC) concrete was researched. In addition, multiple non-linear regression models of the basic performance of BMSC considering the raw materials and mix proportions were proposed. The results show that when the apparent density and water–binder ratios of BMSC were constant, the slump of BMSC increased and the early compressive strength decreased with the increase in the cement content. With the increase in the water–binder ratio, the slump of BMSC increased gradually and the early compressive strength decreased gradually. With the increase in the cement strength grade, the slump and early compressive strength values of BMSC all increased. The slump and standard cube compressive strengths of BMSC had a multiple non-linear power function relationship with the cement strength grade, cement content and water–binder ratio. When the cement content of BMSC was 530 kg/m3, the standard cube compressive strength grade of BMSC that was mixed with fly ash reached 82.7 MPa, and the standard cube compressive strength grade of BMSC that was mixed with slag reached 70.5 MPa.

The influence of materials and production process on RPC compressive strength

In addition to the water binder ratio, the production process, fiber, silica fume and admixture have a significant impact on the compressive strength of RPC. Several factors such as materials and production process affecting RPC compressive strength were studied by experiments. It exhibits that the reinforcement influence of steel fiber on RPC is affected by the strength of composite matrix. The higher the strength of composite matrix is, the better the effect of fiber reinforcement is. The compressive strength of RPC can be greatly improved by vacuum vibration forming. The water demand and activity of silica fume have significant influence on the compressive strength of RPC.

Experimental Investigation on the Mechanical Properties and Microstructure of Basalt Fiber Reinforced Engineered Cementitious Composite.

This study investigated fundamental mechanical properties of a basalt fiber reinforced engineered cementitious composite (BF-ECC) with different volume fractions of basalt fiber (BF), water–binder ratio (W/B) and fly ash (FA) content. The compressive strength, splitting tensile strength, flexural strength and static modulus of BF-ECC were studied at 3, 28 and 56 days, respectively, to explore their development along the ages. Furthermore, the scanning electron microscopy (SEM) analysis was conducted to evaluate the microstructure of BF-ECC. Experiment results demonstrated that bond quality between the BF and the matrix is good, which leads to a significant increase in the flexural strength and splitting tensile strength. The pozzolanic effect of FA obviously improved the splitting tensile and flexural strength of BF-ECC after 56 days of curing, and the appropriate content of the FA content in the BF-ECC ranges from 50% to 60%.

Analysis of early structure formation of anhydrite binders from secondary raw materials using microcalorimetry

This article presents results of a research on changes in energy parameters of fluorogypsum composition of normal consistency with introduction of various additives (μΔn) such as sodium sulfate and sodium sulfite. Activity of binder in interaction with water was defined as the sum of thermal effect of hydration and thermal effect of dispersion of fluorogypsum crystal lattice. In order to compare processes of heat release in the studied gypsum-containing systems, the article presents results of analysis for the following ones: fluorogypsum binder – water, fluorogypsum binder – sodium sulfate – water and fluorogypsum binder – sodium sulfite – water. Research has shown that processes of hydration during by development of alternating exothermic and endothermic effects in systems containing fluorogypsum binders.