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

Concrete is brittle material which generally consists of many micro cracks which are a potential source of crack propagation which leads to possible catastrophic failure and resulting fracture of concrete structures under service loads. The relationship of fracture energy to material properties has not been clearly identified, with most studies showing a relative insensitivity to the water-cement ratio, and concrete cracks propagate mainly along the aggregate-cement interface. This research is an experiment about the effect of water-cement ratio on fracture energy based on the RILEM method. The fracture energy is measured by testing under three bend points with the notch depth ratio is 0.25 and loading rate is 0.05 mm/sec using a closed-loop testing machine to produce load-displacement curve. Concrete used crushed stones with a maximum size of 19 mm which was tested at 56 days of age and has a water-cement ratio (w/cm) of 0.30, 0.40 and 0.6. The correlation between fracture energy and water-cement ratio are insensitive to each other. This can be seen when concrete containing a lower water-cement ratio (0.3) tends to have increased compressive strength but decreases fracture energy.

Fiber reinforced silt ceramsite concrete (FSCC) is the concrete that natural aggregates are partially or completely replaced by silt ceramsite, while fibers are incorporated to enhance its mechanical properties. Orthogonal experiments on the strength of two kinds of FSCC were conducted in 2017. Effects of three factors on 28-day cube compressive & splitting tensile strength of polypropylene fiber silt ceramsite concrete (PFSCC) and steel fiber silt ceramsite concrete (SFSCC) were studied respectively. The experimental results revealed that the effects of aggregate replacement rate, water-cement ratio, and fiber content on the compressive strength of PFSCC decreased in turn. The effects of aggregate replacement rate and water-cement ratio on the splitting tensile strength of PFSCC were equivalent, while the effect of fiber content was the least. The influences of aggregate replacement rate, steel fiber content and water-cement ratio on the compressive strength of SFSCC decreased in turn, while the effects of water-cement ratio, aggregate replacement rate, and steel fiber content on the splitting tensile strength of SFSCC increased. The further variance analysis showed that water-cement ratio and aggregate replacement rate had evident effects on the splitting tensile strength of PFSCC. A few suggestions were made for configuring fiber silt ceramsite concrete.

The effect of water-cement ratio on the microstructure of set Portland cement

Effect of nanocellulose on early hydration and microstructure of cement paste under low and high water-cement ratios

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.

Effects of Water cement ratios on strengths characteristics of concrete produced with Recycled Iron and Steel Slag (RISS) aggregates was studied to understand the structural integrity of RISS aggregate in concrete and to determine the veracity of RISS aggregate as alternative aggregate to granite in concrete works. Mineralogical composition of the aggregate showed Silicon oxide (quartz) as the common mineral; both aggregates are well graded, strong and durable. Lower water cement ratios improved both the compressive and flexural strengths of RISS and granite concrete.

A newly developed ultrasound method that acquires at the same time both reflected and transmitted P-waves, at different angles, using two immersion transducers of 0.5 MHz central frequency, is described in this present study. This non-destructive method allows calculating the longitudinal and transverse velocities, and thus, the Young modulus, so that its evolutions is followed in time domain. The closely correlation between the evolution in time domain of those calculated parameters and hydration properties of cement based materials was used to characterize the effects of different water-cement ratio and curing temperatures on early age hydration behaviour of cement pastes. To do so, cement samples were prepared by mixing Portland cement and freshwater. Results indicates that lower water to cement ratio reduces the workability and increases the Young modulus of resulted cement medium. Also, both ultrasound velocities and Young modulus values increases linearly with increasing curing temperature.

Interlocking brick is a material used for wall work in home construction. Called Interlocking Brick or Brick Interlock because the method of arranging the bricks is interlocked with one another. This interlocking brick itself began to be known in Aceh Province after the 2004 tsunami disaster. Interlocking brick is a block of compacted soil, made of cement, silt soil, and dried sand, measuring 300 χ 150 χ 100 cm3. Interlocking brick can function as a wall that can withstand structural and non-structural components. The purpose of this research is to get the compressive strength value of interlocking bricks designed with variations in the water cement ratio (WCR) so that the optimum compressive strength of interlocking bricks is obtained. The WCR used was 0.3; 0.4; and 0.5, while for the composition of cement, silt, and sand the ratio of 1:2:2 is used. The making of test specimens for testing the compressive strength of interlocking bricks is by cutting the interlocking bricks into cubes measuring 50 χ 50 χ 50 mm by 5 specimens for each variation so that the total of the total specimens are 45 specimens. Testing is done at the age of 7, 14, and 28 days. The results of the compressive strength of interlocking bricks using WCR 0.3 average compressive strength at the age of 7 days reached 8.10 MPa, 14 days reached 9.49 MPa and 28 days reached 10.94 MPa. For WCR 0.4, compressive strength on average at 7 days reaches 5.69 MPa, 14 days reaches 7.61 MPa and 28 days reaches 9.77 MPa. And for WCR 0.5 the average compressive strength at the age of 7 days reaches 5.36 MPa, 14 days reaches 8.25 MPa and 28 days reaches 9.93 MPa. From the compressive strength test results the interlocking brick with a WCR variation of 0.3; 0.4; and 0.5 with a mixture of 1:2:2 can be used as wall work material in house construction for structural construction and the optimum compressive strength value is obtained at WCR 0.3.

Effects of superabsorbent polymers (SAP) on the rheological behavior of cement mortars: A rheological study on performance requirements for 3D printable cementitious materials

Effects of water-cement ratio and superplasticizer dosage on mechanical and microstructure formation of styrene-butyl acrylate copolymer concrete

Foam concrete with different dry densities (400, 500, 600, 700, and 800 kg/m3) was prepared from ordinary Portland cement (P.O.42.5R) and vegetable protein foaming agent by adjusting the water-cement ratio through the physical foaming method. The performance of the cement paste adopted, as well as the structure and distribution of air pores, was characterized by a rheometer, scanning electron microscope, vacuum water saturation instrument, and image analysis software. Effects of the water-cement ratio on the relative viscosity of the cement paste, as well as pore structure and strength of the hardened foam concrete, were discussed. Results showed that water-cement ratio can influence the size, distribution, and connectivity of pores in foam concrete. The compressive strength of the foam concrete showed an inverted V-shaped variation law with the increase in water-cement ratio.

Effects of water-cement ratio, quantity and fineness of sand on the evolution of lime in set portland cement systems

It is often assumed that flexural strength of concrete has less significance impact on overall concrete strength. However, from fracture mechanics point-of-view tensile is an element the mechanics always look into due to cracking does associate with tension. In the research, fracture is translated into physical laboratory experiment by introducing notches. Physical laboratory works on concrete beams with three-point bend test configuration under static load and calculating outputs from laboratory with numerical equations. Three-point bend test method is conducted because from the testing, tensile strength or also recognised as flexural strength of concrete for each water-cement ratio could be attain. Thus, the aim of this article is to reveal and discuss the pattern of flexural strength of concrete on different water-cement ratio. The testing follows conventional fracture three-point bend test on concrete but with revised version by testing notched concrete beams. Normal three-point bend tests were run on concrete beams with different notch sizes; 30 mm, 15mm, and 5 mm respectively. There were three water-cement ratio decided in concrete mix; 0.3, 0.4, and 0.5. Thus, the trend of flexural strength of concrete follows the trend of water-cement ratio. Flexural strength increases when water-cement ratio increases up to water-cement ratio 0.5.

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.

In this paper, the effect of water-cement ratio and chloride ions on the concrete meso-structure was studied. Three kinds of concrete cubes with different water-cement ratios were immersed in fresh water and salt water, respectively. Then, the Electrochemical Impedance Spectroscopy (EIS) analysis of various test cubes were carried out by using electrochemical workstation. The results show that the salt water can improve electric double layer capacitance in the test cubes with the same water-cement ratio, but it can reduce some other parameters such as resistance of pore solution, resistance to transfer the hydrated electron, coefficient of diffusion impedance of concreter, which shows that the chloride ions diffused into the concrete in salt water and increase the ionic concentration in pore solution and C-S-H gel. However, the phase angle index is constant whether in fresh water or salt water, which shows chloride ions cannot affect the concrete meso-structure even though they can improve the ion concentration of pore structure. For the concrete test cubes which has different water-cement ratio in salt water, with the reduction of water-cement ratio, the electric double-layer capacitance of concrete remains unchanged, which indicates when the water-cement ratio becomes smaller, the porosity becomes lower, and the internal structure of concrete becomes denser.