Influence Of Water-binder Ratio Research Articles

Study on desorption characteristics of water vapor in fly ash concrete materials

In this paper, water vapor desorption tests are carried out on water-saturated concrete materials with different water-binder ratios and fly ash content. The desorption parameters are analyzed using the adsorption curve analysis method, which enables the acquisition of desorption characteristics for concrete materials. By utilizing the desorption isothermal curve, the desorption rate is calculated and further analysis is conducted on the influence of water-binder ratio and fly ash content on this rate. The results indicate that the desorption and activation energy for water vapor desorption in concrete materials is higher than the adsorption energy at the first layer, suggesting that removing water vapor from inner pore walls is more challenging than its adsorption. The amount of water vapor released from concrete materials follows a power function over time, as does the rate of desorption. Under conditions of relatively low ambient humidity, an increase in the water-binder ratio leads to a decrease in the rate of desorption. Conversely, under relatively high ambient humidity, an increase in the water-binder ratio results in an increased rate of desorption.

Characteristic of Fresh and Harden Properties of Polyvinyl Alcohol Fibre Reinforced Alkali Activated Composite

Fibre can enhance the mechanical properties of cement-based composites, but fibre also degrades their workability. However, the quantitative effects of fiber content and length-diameter ratio on alkali-activated materials are still unclear. Various aspect ratio, volume fraction of polyvinyl alcohol fibre (PVAF), and various water-binder ratio were employed to prepare a total of 26 groups of fibre reinforced alkali-activated composite (FRAAC). The influence of PVAF fibre factor (product of fiber volume fraction and length-diameter ratio) on flowability, compactness, strength, and crack fractal dimension of FRAAC was researched. The influence of water-binder ratio on the plastic viscosity of FRAAC was more significant than that on the yield stress. When fibre factor was lower than critical value of 150, the influence of fibres could be overlooked. The reason was that the space between fibres was distant, so the flowability of FRAAC was not impacted by PVAF. At this time, fibres were challenging to restrict the cracks in matrix and increase their mechanical properties. When fibre factor was higher than critical value 150 and lower than density packing value 450, the flexural strength, compressive strength and crack fractal dimension of FRAAC were considerably enhanced, and the FRAAC could still flow easily under dead weight. When fibre factor were above 450, noteworthy fibre balling considerably decreased the flowability, leading to poor solidity and reduced compressive strength. Hence, the ideal content of PVAF in alkali activated composite is between 150/(l/d) and 450/(l/d).

Influence of Water-Binder Ratio on the Mechanical Strength and Microstructure of Arch Shell Interface Transition Zone

To prepare lightweight ultra high performance concretes used in the large-span and super-tall structure engineering fields, the effects of water-binder ratio on the mechanical performances, hydration products, and microstructure of the arched shell interface transition zone between the prewetting spherical lightweight aggregates and cement matrix were studied. The experimental results showed that adding prewetting spherical lightweight aggregates promoted the formation of an arched shell interface transition zone. And the hydration degree, microhardness, and elastic modulus values of the arched shell interface transition zone were still higher than the cement matrix. With the reduction of the water-binder ratio, the microhardness, elastic modulus, thickness, and compactness of the interface transition zone had an increase, and the internal curing action of the prewetting spherical lightweight aggregates was more obvious. Especially when the water-binder ratio was 0.18, the hydration degree of the arch shell interface transition zone increased by 18.27% compared with the cement matrix after 28 days curing time. It was concluded that the prewetting spherical lightweight aggregates could have better internal curing and arched shell effects in cement-based materials with a low water-binder ratio. Therefore, adding prewetting spherical lightweight aggregates was regarded as a potential measure to fabricate the lightweight ultra high performance concretes.

Influence of Fly Ash Dosage and Desert Sand Replacement Ratio (DSRR) on the Carbonation Resistance of Concrete

Carbonation of concrete causes corrosion of the steel reinforcement and reduces the service life of the structure. Based on the reality that fly ash discharge is increasing year by year and construction sand is becoming increasingly limited, it is of practical importance to study the effect of fly ash dosage and desert sand replacement rate on the carbonation resistance of concrete. Orthogonal test L9(34) with four factors and three levels was designed to study the influence of water-binder ratio, fly ash dosage, sand ratio and DSRR on carbonation resistance of desert sand concrete (DSC). The results of the orthogonal tests were analysed by range analysis and ANOVA and a comparatively better concrete mix ratio was given. Next, single-factor tests were designed to investigate the effects of fly ash and desert sand replacement rates on the carbonation resistance of DSC respectively. The regression model among carbonation depth, fly ash dosage and DSRR was established. The experimental results show that the carbonation depth of concrete with fly ash as a single variable increases with the amount of fly ash, increasing more rapidly in the early stages than in the later stages. As the DSRR increases, the carbonation depth of concrete with desert sand as a single variable first decreases and then increases and reaches its lowest value when DSRR equals 20%. When fly ash and desert sand are mixed into concrete simultaneously, the carbonation depth reaches minimum value on the condition that fly ash dosage is 10% and DSRR is 20%.

The mechanical behavior of RPC under combined shear and compressive loads

In this study, the shear behavior of reactive powder concrete (RPC) in terms of shear strength and shear slip was studied by direct shear tests on cubic specimens and the influences of water-binder ratio, steel fiber volume ratio and normal compressive stress ratio were investigated. The test results indicated that using a low water-binder ratio and a reasonable fiber content could enhance the shear strength of RPC specimens. The RPC specimen containing steel fiber will not be severed into two individual parts due to the connection of steel fiber. Moreover, the normal stress was the key contribution to the shear strength, and the residual shear capacity was mainly provided by the friction of the shear surface. The cracking of the specimens became more severe but the shear strength in the cyclic horizontal test did not decrease obviously compared with that in the monotonic horizontal test. Applying the twin-shear unified strength theory to the test data, it was indicated that the elliptic curve showed a good agreement. Therefore, the unified twin shear strength theory could predict the proper RPC strength envelope curve under combined compressive-shear stress states.

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.

Study on properties of carbon fibre reinforced cement-based grouting materials

As an efficient, eco-friendly and economical solution for connecting precast concrete components, grouted sleeve connectors aroused widespread interest in engineering site. However, as the key material of grouted sleeve connection, grouting material needs to provide enough good performance to meet the engineering requirements. In order to better design the mix proportion of grouting materials, this paper studies the influence of water binder ratio, carbon fibre content, expansion agent addition and other factors on the performance of grouting materials, and optimizes the mixture ratio of grouting materials by analyzing the workability, compressive strength and expansibility, and analyzes the bonding performance of grouting materials by using the half-grouting steel sleeve connector.

Influence of water binder ratio on strength and acid resistance of concrete made up of mineral admixture as supplementary cementitious material

Mineral admixture concrete is proved to be beneficial to enhance strength and resistance of concrete against aggressive chemical environment. However, water binder (w/b) ratio is the major responsible factor to govern all the concrete material properties. So, for a strong and durable concrete, it is imperative to design a proper mix with suitable w/b ratio. The present study investigates the effects of w/b ratio on the compressive strength and acid resistance property of mineral admixture incorporated concrete. Fly ash (FA) and crusher dust (CD) were used in concrete as partial cement replacement at the level of 20%, 40%, and 60% to cast concrete cube of size (150 × 150 × 150) mm3 using three w/b ratios of 0.35, 0.38 and 0.4. The fresh concrete properties, the compressive strength of the different types of concrete samples at 365 days of water curing and the acid (5% H2SO4) resistance of those water cured concrete samples after 365 days of acid exposure have been investigated to study the impact of w/b on the strength and acid resistance properties of concrete. Full factorial DOE with ANOVA was conducted to determine the significance of the concrete type and w/b ratio on strength and strength loss of concrete under acid exposure. In addition, the Grey relational Analysis and the Response Surface Methodology (RSM) have been also used to find the impact of w/b ratio towards simultaneous optimization of strength and % strength loss on acid exposure to concrete.

Experimental Investigation on Hydroabrasive Erosion of Steel Fiber UHPC and Rubber UHPC

Steel fiber ultrahigh performance concrete (UHPC) and rubber ultrahigh performance concrete (UHPC) adopt the methods of “rigidity overcomes rigidity” and “softness overcomes rigidity,” respectively, to resist the abrasion and cavitation erosion caused by water flow carrying large solid particles. The above two have been applied in engineering successfully, but there are differences in material properties, mechanical properties, and microstructures. In this study, we will analyze the difference of abrasion resistance performance of the above two kinds of UHPC, in terms of, for example, compressive strength, abrasion resistance strength, abrasion rate, and microstructure in different ages, so as to provide a new material and method. The results indicate that the steel fiber UHPC compressive strength is higher than that of rubber UHPC (containing 1% steel fiber), and the abrasion resistance performance of steel fiber UHPC is lower than that of rubber UHPC (containing 1% steel fiber) when the rubber content is 10% and 12.5%. With the increase of steel fiber content, the compressive strength of steel fiber UHPC is not significantly improved, and the influence of water‐binder ratio (W/B) on UHPC is higher than that of steel fiber content. With the increase of rubber content, the rubber UHPC compressive strength decreases, abrasion resistance strength decreases, and abrasion rate increases. The cement paste‐aggregate interface transition zone (ITZ) of steel fiber UHPC and rubber UHPC has few internal voids and high compactness; however, the ITZ of steel fiber UHPC is denser than that of rubber UHPC.

Pore structure characterization of early-age cement pastes blended with high-volume fly ash

High-volume fly ash is normally used as a partial replacement for cement to improve the workability, durability, and economic properties of concrete. The pore structure is an important factor affecting the performance of concrete. In this study, the influence of water-binder ratio (w/b) and fly ash content on the pore structure of early-age cement paste was determined using low-field nuclear magnetic resonance spectroscopy. Experimental results show that the most probable pore diameter increases with fly ash content and w/b and decreases with age. The porosity increases with w/b and decreases with age. A modified pore structure model, which is based on the existing models and the Weiball distribution, is proposed for high-volume fly ash cement-based materials.

Strength, Permeability, and Freeze-Thaw Durability of Pervious Concrete with Different Aggregate Sizes, Porosities, and Water-Binder Ratios

Pervious concrete (PC), as an environmental friendly material, can be very important in solving urban problems and mitigating the impact of climate change; i.e., flooding, urban heat island phenomena, and groundwater decline. The objective of this research is to evaluate the strength, permeability, and freeze-thaw durability of PC with different aggregate sizes, porosities, and water-binder ratios. The orthogonal experiment method is employed in the study and nine experiments are conducted. The compressive strength, flexural strength, permeability coefficient, porosity, density, and freeze-thaw durability of PC mixtures are tested. Range analysis and variance analysis are carried out to analyze the collected data and estimate the influence of aggregate size, porosity, and water-binder ratio on PC properties. The results indicate that porosity is the most important factor determining the properties of PC. High porosity results in better permeability, but negatively affects the mechanical strength and freeze-thaw durability. PC of 15% porosity can obtain high compressive strength in excess of 20 MPa and favorable freeze-thaw durability of 80 cycles without sacrificing excessive permeability. Aggregate size also has a significant effect on freeze-thaw durability and mechanical strength. Small aggregate size is advantageous for PC properties. PC with 4.75–9.5 mm coarse aggregate presents excellent freeze-thaw durability. The influence of the water-binder ratio on PC properties is not as significant as that of aggregate size and porosity. An optimal mix ratio is required to trade-off between permeability, mechanical strength, and freeze-thaw durability.

Experimental and numerical study on stress-strain behavior of self-compacting SFRC under uniaxial compression

The properties relating to the compressive stress-strain curve of self-compacting steel fiber reinforced concrete (SFRC) were experimentally studied in this paper. Type of steel fiber, volume fraction of steel fiber and water-binder ratio were considered as the influence parameters. Test results showed that regardless of fiber type, self-compacting SFRC had greater compression toughness due to the better sustainability of descending portion of stress-strain curve, and the compression toughness ratio, axial compressive strength, peak-strain of self-compacting SFRC increased with the volume fraction of steel fiber. The influence of water-binder ratio was reflected by the strength of self-compacting SFRC. Based on the experimental data, the predictive models are proposed for the prediction of compressive stress-strain relationship of self-compacting SFRC.

Influence of Water-binder Ratio on the Microstructure of Air-entrained Concrete

The concrete’s microstructure affects its macroscopic properties such as the strength and the frost resistance. This research is to study the influences of different water-binder ratio on the microstructure characteristics of air-entrained concrete, which will be done by using both the mercury intrusion test and the optical lead test. The research aims to find out the influences of the change of water-binder ratio on the pore size distribution and pore structure of the air-entraining concrete and non air-entraining concrete. The research results showed that the water-binder ratio mainly influenced the pore gel pore volume in the non-entrained concrete, and the pore volume of capillary pores as well as excessive pores in air-entraining concrete increased along with the increasing of water-binder ratio. The most probable aperture and porosity also gradually increased, while the fractal dimension decreased, when the water-binder ratio increased. It was the increasing of entraining agent content in the air-entraining concrete that increased the pore fractal dimension. The lower average pore spacing factor was to get in the air-entraining, the higher water-binder ratio required more air content.

Effect of shrinkage-reducing admixture and expansive agent on mechanical properties and drying shrinkage of Engineered Cementitious Composite (ECC)

In order to reduce the drying shrinkage strain of traditional ECC and diminish the shrinkage differences between concrete and PVA (PolyVinyl Alcohol) fiber, this paper designs eighteen groups mix proportions based on Taguchi Methods. The influences of water-binder ratio, sand-binder ratio, fly ash content, expansive agent content, shrinkage-reducing agent content and PVA fiber volume content on the compressive strength, tensile properties and drying shrinkage are researched. In addition, the effect of PVA fiber on the crack resistance is investigated. The results indicate that the shrinkage strain of ECC increases with the raising of water-binder ratio, and decreases with the increasing of sand-binder ratio, fly ash content, expansive agent, and shrinkage-reducing agent; The anti-cracking performance is significantly improved along the fiber volume content changes, but it has little effect on ECC shrinkage strain. The compressive and tensile strength of ECC will greatly reduce with the increasing of shrinkage-reducing agent, rather, the compressive strength of ECC will enhance with the increase of expansive agent; But the expansive agent will lower the tensile strength and ultimate tensile strain. In the scope of this research, the water-binder ratio, sand-binder ratio, and fly ash content is about 0.25–0.33, 0.33–0.45, and 65% respectively. The research generated a set of reliable and valuable test data for the researchers and practical structural engineers in the field of ECC drying shrinkage.

A Novel Method for Measuring Porosity for Normal and High Strength Concrete

Abstract This paper described a novel apparatus for the measurement of porosity for normal and high strength mortar and concrete using vacuum-pressure saturation method. A detailed description of design, test procedure, and evaluation of results of the vacuum-pressure saturation apparatus was presented. Porosity values obtained using the apparatus were highly repeatable and reproducible. The apparatus could detect the effect of age, influence of water-binder ratio, and influence of supplementary cementitious materials of concrete and mortar mixtures. The apparatus yielded full saturation for high strength and dense mortar and concrete. The porosity values for normal strength concrete using the vacuum-pressure saturation apparatus were in good agreement with the results obtained using vacuum saturation method proposed by RILEM.

Comparative study of accelerated carbonation of plain cement and fly-ash concrete

Accelerated carbonation of plain cement concrete and concrete with fly-ash replacing cement partially, is discussed in the present paper. Mechanical properties such as compressive strength, flexural strength, modulus of elasticity, durability aspects such as depth of carbonation and porosity of carbonated concrete are studied. To study the influence of water binder ratio on the above-mentioned properties, water-binder ratios of 0.35, 0.50 and 0.65 are used. It is observed that the mechanical properties of carbonated concrete have increased with the duration of carbon dioxide exposure. So did the depth of carbonation, whereas the volume of permeable voids has reduced leading to the decrease in porosity. An expression to predict the depth of carbonation of fly-ash concrete has also been developed.

Influence of slag content and water-binder ratio on leaching behavior of cement pastes

In order to obtain quickly the influences of blast furnace slag and water-binder ratio on the leaching behavior of cement-based material and its corrosion resistance in water environments, an accelerated calcium leaching experiment on a slice specimen with slag-cement pastes in 6M NH4 Cl solution was carried out. Using the saturation-drying weighing method, X-ray diffraction (XRD) and the scanning electron microscope (SEM/EDS) measurement, the influences of water-binder ratio and slag content on the porosity, phase composition, microstructure morphology and Calcium-Silicon ratio of slag-cement pastes in the process of calcium leaching were analyzed. Results show that, compared to cement pastes without slag, the slag-cement paste with the appropriate slag content has a low rate of microstructure deterioration and a good leaching resistance. The optimum slag contents in slag-cement pastes are respectively 40% and 50% corresponding to the low and high water-binder ratio. The porosity, Calcium-Silicon ratio and microstructure morphology of slag-cement pastes exhibit small change in the process of accelerating leaching, and this indicates that the slag-cement pastes with the optimum slag content can provide the best performance of calcium leaching resistance in the soft-water environment.

Influence of Water Binder Ratio on High Performance Concrete

High performance concrete M60 cubes of 150 mm X 150 mm X 150 mm were tested experimentally under static loading. With the variation in the water binder ratios of 0.25, 0.28, 0.33, 0.39 and hyper plasticizer of 0.6%. 0.8%. 1.0%, 1.2% the cubes were cast and accordingly the cylinders were cast. For each ratio of water binder, 12 cubes and 2 cylinders were cast. Out of 12 cubes, 3 cubes were cured for 7 days, 3cubes for 15 days, 3 cubes for 21 days and the balance 3 cubes for 28 days. All the cubes were tested in a 2000kn compression testing machine. The load deflection curves, stress- strain curves were drawn for each cube and cylinder. The average compressive strength of each mix for different number of days of curing were calculated. The modulus of elasticity was calculated for each design mix.

A Comparative Study on Production of Autoclaved Aerated Concrete by Coal Gangue Fly Ash

In this paper, compared with common fly ash, the low-silicon coal gangue fly ash is used to produce fly ash autoclaved aerated concrete. The influences of water binder ratio, coal gangue fly ash content, calcareous content and conditioning agents on the compressive strength of the autoclaved aerated concrete are investigated. The results indicate the coal gangue fly ash has different properties from the common fly ash such as its granule appearance and the activity as AAC siliceous raw material. It is noting that the coal gangue fly ash can also be used to prepare AAC blocks by optimizing the raw material formulation and procedure and its B05 product can reach the China top industrial standard.

Study on Production of Autoclaved Aerated Concrete by Coal Gangue Fly Ash

In this paper, the low-silicon coal gangue fly ash is used to produce autoclaved aerated concrete. The influences of water binder ratio, coal gangue fly ash content, calcareous content and conditioning agents on the compressive strength of the autoclaved aerated concrete are investigated. Optimal raw material formulation and procedure are determined for the autoclaved aerated concrete. The compressive strength and frost resistance of autoclaved aerated concrete made by the optimal raw material formulation and procedure meet with the requirements of autoclaved aerated concretes of B05 grade, and its thermal conductivity, drying shrinkage reach the requirements of the relevant national standards of China.