Effects Of Water-cement Ratio Research Articles

Preparation and Study on the Waterproof Performance of Polystyrene Lightweight Composite Insulation Materials

In the experiment, polystyrene particles were used as lightweight aggregate to prepare lightweight composite insulation board which was mixed with fibers and waterproofing agent. The effect of water-cement ratio and volume ratio of polystyrene particles and cement on the density and mechanical properties of polystyrene insulation board was researched. And styrene-acrylic emulsion, stearic acid emulsion and composite emulsion waterproofing agent were used respectively to modify the waterproof of insulation board. Besides, the underlying action mechanism was explored. The results show that the optimum volume ratio was 5:1, and the optimum water-cement ratio was 0.45. And when the content of composite emulsion waterproofing agent was 8%, the 2h and 24h water absorption were 6.0% and 8.1% respectively.

Assessment of Hydration Degree of Cement in the Fly Ash-Cement Pastes Based on the Calcium Hydroxide Content

The hydration degree of fly ash and the calcium hydroxide (CH) content were measured. Combined with the equilibrium calculation of cement hydration, a new method for assessment of the hydration degree of cement in the fly ash-cement (FC) pastes based on the CH content was developed. The results reveal that as the fly ash content increase, the hydration degree of fly ash and the CH content decrease gradually; at the same time, the hydration degree of cement increase. The hydration degree of cement in the FC pastes containing a high content of fly ash (more than 35%) at 360 days is as high as 80%, even some of which hydrates nearly completely. The effect of water-cement ratio to the hydration degree of cement in the FC pastes is far less distinct than that of the content of fly ash.

Effect of Water-Cement Ratio on the Macrocell Polarization Behavior of Reinforcing Steel

The effect of water-cement ratio on the macrocell polarization behavior of reinforcing steel embedded in cement mortars was investigated by comparing and analyzing the macrocell polarization ratios and slopes of anodic and cathodic steels. Based on the experimental results, the relationship between macrocell potential difference and macrocell current density was also analyzed, and the mechanism of macrocell polarization affected by water-cement ratio was proposed. The results indicated that the water-cement ratios had little impact on the macrocell polarization ratios of cathode and anode. The lower water-cement ratio could reduce the macrocell current by decreasing the macrocell potential difference and increasing the macrocell polarization resistance of the cathode and anode.

A Review on Frost Resistance of Steel Fiber Reinforced Lightweight Aggregate Concrete

Compared with ordinay concrete, weight of lightweight aggregate concrete could be lower 20%-40% under same bearing capacity. Mixed with some given steel fibers in it, crack resistance and flexural strength will be improved. Once lightweight aggregate concrete mixed with steel fibers meets the requirements of frost resistance, it could be applied to most civil engineerings in a cold area. In this paper, the frost resistance mechanism of steel fiber reinforced lightweight aggregate concrete is introduced. The research status of frost resistance of steel fiber reinforced lightweight aggregate concrete is reviewed including the effects of water cement ratio, aggregate, mineral admixture and amount of fiber, frost resistance experimatal methods and engineering applications etc. Some further researches are prospected.

Experimental Investigation on the Influence of Water-Cement Ratio on Air-Void Parameters of Cement Concrete

This paper studies the effect of water-cement ratio [w/ on the air-void parameters of cement concrete, which has a significant influence on the durability of concrete. Based on the experimental investigation, it is found that the impact on the air content of hardened concrete due to different water-cement ratio is not great. Test results also indicate that with the increase of water-cement ratio, the spacing factors also experienced a marked rise, and the mean diameters as well as the specific areas of air voids evidently increased or declined, respectively, which may lead to an adverse effect on the frost resistance of concrete.

Experimental Study of Effects of Water-Cement Ratio on the Mechanical Property of High-Performance Cement-Based Iron-Tailings Grouting Material

This thesis aims to research the influence factors of the mechanical property of high performance cement-based iron-tailings grouting material (ICGM). By changing the parameter of water-cement ratio, the experiment is performed to contrast ordinary cement-based grouting material (OCGM) with ICGM. Their compression strength and anti-breaking strength are studied. Through the experimental results and the contrast of them, the influence of water-cement ratio on the mechanical property of the cement-based iron-tailings grouting material is evaluated and the reasonable water-cement ratio parameter is obtained. The experimental results show that the mechanical properties of ICGM reduce with the increase of water-cement ratio. Moreover, when the water-cement ratio reaches 0.31, there is an obvious reduction of early age strength. Thus, it is advisable to adopt 0.30 as the reasonable water-cement ratio.

Effect of Water-Cement Ratio on Carbonation and Steel-Corrosion Resistance of Recycled Concrete

This paper studies the effects of different water-cement ratio on recycled concrete strength, anti-carbonation capability, and protecting reinforce steel bar capability. Select the water-cement ratio 0.6,0.55,0.5,0.45,0.4 five cases of the pilot study.It shows that: recycled concrete cube compressive strength, anti-carbonation capacity and protecting reinforce steel bar capability are less than ordinary concrete.

Effect of Admixtures on Dynamic Elastic Modulus of Cement Paste at Early Age

The elastic modulus of cement paste is the key parameter for characterizing the mechanical response of concrete. In modern concrete technology, the admixtures are often used to enhance the performance of concrete. This paper introduces a nondestructive testing method to evaluate the dynamic elastic modulus of cement paste. Moreover, the effect of water-cement ratio and conventional admixtures on the dynamic elastic modulus of cement paste is investigated, in which three kinds of admixtures are taken into account including Viscosity Modifying Admixture (VMA), Silica Fume (SF), and Shrinkage-Reducing Admixture (SRA). The results from experimental investigation indicate that the dynamic elastic modulus of cement paste increases with decreasing water-cement ratio. The addition of SF increases the dynamic elastic modulus, however, the overdosage of VMA causes its reduction. SRA reduces the elastic modulus at early age without affecting the elastic modulus at later period.

In situ measurement of the permeability of concrete by FTIR-MIR

Fourier transform infrared spectroscopy with multiple internal reflection mode (FTIR-MIR) has been applied for the first time to measure the permeability of concrete. The effect of water-cement ratio and curing time on the microstructure and permeability of concrete was studied. Also, the penetration process of H2O and SO4(2-) through the concrete specimens was investigated. The results indicated that the movement of H2O through unsaturated concrete was mainly caused by capillary suction and the movement of SO4(2-) through unsaturated concrete should take into account diffusion, advection caused by a capillary suction flow and the reaction between SO4(2-) and the cement hydration products. The permeability of concrete was determined by its microstructure. With the decrease in water-cement ratio and the increase in curing time, the porosity and the connectivity of pores in concrete decreased, which resulted in the decrease of concrete permeability.

Effcets of Water-Cement Ratio on Tensile Basic Creep of Early-Aged Concrete

The effects of water-cement ratio on the tensile creep of early-age concrete under constant load were investigated. Creep and shrinkage of concrete under sealed curing condition was researched to determine the tensile basic creep of concrete. The results indicate that, as in compression, creep of concrete in tensile is very sensitive to water to cement ratio. The results also indicate that the tensile creep increases with the water to cement ratio. And that the tensile creep develops rapidly within the first day after loading.

Experimental Study on Application Properties of Macroporous Ecological Concrete without Sand

This paper suggests that deposition paste area is one of those leading control indicators of mix proportion design for the macroporous ecological concrete without sand. By analyzing the effect of water-cement ratio, amount of cement, and type of coarse aggregates on application properties of concrete, it puts forward that when carrying out the mix proportion design of the concrete, setting the water-cement ratio as 0.4 can help the macroporous ecological concrete without sand acquire satisfying application properties. Based on this idea, experiments to the later period strengths and the erosion resistance property of concretes are tried out. Finally, the result of this series of experiments shows that the macroporous ecological concrete without sand possesses necessary conditions for plants to survive and grow up.

The Effect of Water-Cement Ratio and Curing Age on the Strength of Recycled Concrete

The effect of water-cement ratio and curing age on the strength of recycled concrete was studied by experiment with the combination of the recycled coarse aggregate adding natural sand. The results showed that with the increase of curing age, the greater the water-cement ratio is, the smaller the strength growth rate is; the smaller the water-cement ratio is, the greater the strength growth rate is. There is a relatively larger increase in the growth rate of 90d strength than 28d’, which is significantly higher than that of the ordinary concrete. The linear relationship between water-cement ratio and strength of recycled concrete is worse than that of ordinary concrete. Under the same water-cement ratio and curing age, the strength of recycled concrete is lower than that of ordinary concrete, and the empirical formulas between the strength of 28d and 7d, 90d and 28d were obtained.

Experimental Study on Engineering Performance of Portland Cement Stabilization of Soil-Bentonite

Slurry trench cutoff walls, constructed using self-hardening cement-bentonite (SCB) are the most common form of in-ground vertical contaminant barrier in the world, and are increasingly being used in China. As a kind of vertical anti-seepage wall material， SCB slurry is requently used for the containment of contaminated groundwater and other envirofunental Protection Projeets abroad. Domestie applieation of cement-bentonite slurry walls is not extensive. The objective of this study was to evaluate the effect of water-cement ratio and cement content on the hydraulic behavior of SCB and soil–bentonite (SB) mixtures permeated with water. The experimental program included unconfined compression tests, expansion ratio tests and hydraulic conductivity tests. The test results indicated changes in hydraulic conductivity take place due to the variation of the water-cement ratio and permeant fluid. Cement is a main material in effecting the CSB strength of unconfined compression. Cement greatly influenced the CSB permeability coefficient. Addition of Portland cement to the SB mixtures increased their hydraulic conductivity when permeated with water. The hydraulic conductivity of the SCB specimens permeated with water was inversely related to the cement content.

Coefficient of Linear Expansion of Air-Entraining Concrete with Silica Fume

The effect of water-cement ratio, air content, silica fume and sand ratio of concrete on the coefficient of linear expansion(CLE) was studied by orthogonal experiment. The results show that under a certain amount of cement material, CLE of concrete increase as the water-cement ratio increases and the effect of water-cement ratio on CLE of concrete is remarkable; with the increase of blending ratio of silica fume, the CLE of concrete increases; the CLE of concrete reduces with 3.5% air content in concrete, but rebound with 6% air content in concrete; with the sand rate increases, CLE of concrete increases; CLE per unit compressive strength of concrete with silica fume decreases with increase of silica fume content; CLE per unit compressive strength of concrete with air content increase when air content increase.

Research on Expanded Polystyrene Light-aggregate Concrete

EPS(Expanded polystyrene)is used as light-weight.By adding fly ash and modified polymers in proper proportion aggregate, and cement is used as adhesive material, the uniformity and stability of pastes can be improved. The EPS light-weight concrete is obtained with good physical mechanical perform ance and some problems of segregated layers, weak interfacial bonding, and low density and strength etc, can be solved. The effects of water cement ratio and fly ash proportion on the mobitity of the mixture and the strength of the concrete are analyzed.

Use of Recycled Rubber Tires in Normal and High-Strength Concretes

This paper reports an investigation on the use of recycled rubber tires in producing normal- and high-strength concretes under tropical conditions, as experienced in Singapore and the Asia region. The tests performed on fresh concrete were a slump test and a determination of unit weight and air content. Tests on hardened concrete were nondestructive tests that included measurements of hardened density and ultrasonic pulse velocity; and destructive tests that covered a cube test to obtain the compressive strength of concrete, and an axial compression test on concrete cylinders to determine their stress-strain curves. The effects of water-cement ratio (w/c), rubber as aggregate replacement, rubber type, mineral admixture as cement replacement, steel fiber reinforcement, and curing age on the properties of rubberized concrete were assessed and compared. Recommendations were given on the applications of normal- and high-strength concretes containing recycled rubber in relation to their fresh and hardened properties.

視覚的評価方法にもとづくモルタル中の自由水のブリーディング挙動に関する実験的研究

Main purpose of the present study is to examine the rising behavior (bleeding) of free water in mortar by using a proposed visible evaluation method. A series of experiments of exp.1 to 3 was carried out. In exp.1, rising path of colored liquid as free water injected into mortar was observed. In exp.2, effect of water-cement ratio and volume of the injected colored liquid on its rising distance was examined, and the behavior of the internal bleeding water was idealized for modelling. In exp.3, applicability of the proposed model was verified through a 2-dimensional visualization experiment, using model materials. Consequently, it was shown by the devised visible evaluation method that the bleeding behavior in mortar can be checked qualitatively. Moreover, the rising process of the colored free water showed clearly that the proposed method is applicable to discuss the bleeding behavior in actual mortar and concrete.

靱性を付与したセメント系押出成形部材の曲げ性能に及ぼす親水性化加工ポリプロピレン短繊維形状の影響に関する実験的研究

Using polypropylene fibers treated hydrophilically for cementitious components by extrusion moulding, it has been confirmed that flexural behaviors of these components are improved. This paper deals with geometrical effects of this fiber from the viewpoints of improving the flexural behaviors of cementitious components on the basis of two series of experiments. The following items are clarified; l) Regardless of the geometrical effects of fibers, first cracked flexural strength and effective water cement ratio had a unique linear relation. 2) First cracked flexural strength could be predicted in general by extruding pressure. This knowledge was utilizable in the quality control in manufacture. 3) The relation between first cracked flexural strength and surface dry density was represented as a unique curve for every kind of fibers.

ボス供試体による構造体コンクリート強度の推定法の検討 : 鉄筋コンクリート構造物の健全性評価技術に関する研究

New method of evaluating the compressive strength of concrete in structures using BOSS: Broken off Specimens by Splitting Method was developed. Applicability of BOSS specimen was examined by comparing the compressive strength of specimens taken from a model structure by coring and by BOSS. Effects of water-cement ratio and the sampling height on compressive strength were studied with the variance analysis. It was confirmed that high correlation was found between compressive strengths of BOSS and core. Thus the BOSS based simple formula may be applicable to the prediction of compressive strength of concrete in structures.

Influence of Aggregate Type on Mechanical Behavior of Normal- and High-Strength Concretes

Effects of coarse aggregate type on the mechanical properties of both normal- and high-strength concretes (HSCs) were investigated under compressive loading. Basalt, sandstone, and Triassic and Devonian crushed limestone coarse aggregates were used in the concretes. For each coarse aggregate type, 6 concrete mixtures were made with the same portland cement and natural sand. Nominal slump, effective water-cement ratio, and cement content were kept constant in each concrete class. In all mixtures, the grading and maximum particle size were the same. Triassic limestone containing concrete had the highest compressive strength. However, in HSCs, the compressive strength of basalt containing concrete had the highest value. In HSCs, the hysteresis loops of Triassic and Devonian limestone concretes are generally narrower than those of basalt and sandstone concretes. It can be concluded that the irreversible energy up to prepeak stress in compression decreases significantly and the loop becomes narrower with an increase in compressive strength. The brittleness index increases substantially with the compressive strength of concrete.