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

In order to study the effect of water cement ratio on the damage degree of concrete at different stress levels, the acoustic and acousto-ultrasonic characteristics of concrete with different water cement ratio under multi-stage loading were analyzed. It was concluded that with the increase of the damage degree of concrete, the damage variable and the third harmonic ratio increased, while the acousto-ultrasonic velocity and acousto-ultrasonic energy decreased. Among them, the third harmonic ratio was the most sensitive parameter affecting the damage degree. The compressive strength of concrete decreased with the increase of water cement ratio, and they were linearly related. Furthermore, with the increase of the stress level or the increase of the water cement ratio, the damage of concrete occurred during the holding period increased.

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.

To design a reasonable packing material, solve the problem of solid pollution brought by the iron ore mining, alleviate a lot of backfilling affect national economic development and the current situation of environmental governance. Backfilling materials in this paper, we study the different water-cement ratio pack slump and uniaxial compressive strength and discusses the workability of water-cement ratio on filling body and the influence of uniaxial compressive strength. The experimental results show that with the increase of water cement ratio, the filling body's workability is better and uniaxial compressive strength is lower. When water cement ratio is 0.4, workability and strength of filling body is the best. The experiment provide reliable data for engineering application practice, at the same time to provide reference for other related experiment.

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.

Foam concrete is a type of environmental protection and energy-saving concrete product that contains a large number of small, closed pores and has considerable strength. This experiment aims to study the compressive durability of foam concrete with hydrogen produced by chemical foaming under freeze-thaw cycles. Through the mass loss rate, resonant frequency, dynamic elastic modulus of test blocks under different freeze-thaw cycles. From the measurements and calculations of relative dynamic elastic modulus and uniaxial compressive strength, it is concluded that with the increase of water-cement ratio, the durability index increases from 0.4 to 0.5 and 0.6, and the uniaxial compressive strength decreases. With the increase of air content and porosity, the loss of dynamic elastic modulus increases, which has different effects on the mass loss rate of test blocks with different water-cement ratios. The water-cement ratio has little effect on the test block, the loss rate of b2 is the largest and b1 is the smallest in the test block with 0.5 water-cement ratio, the loss rate of c3 is smaller in the test block with 0.6 water-cement ratio, and the loss of other groups is larger, but the mass loss rate of all 12 groups of test blocks does not reach 5%, and the durability is guaranteed.

Experimental study on expansion and cracking properties of static cracking agents in different assembly states

Jet grouting is one of the most widely applied soil improvement techniques. It is suitable for most geotechnical problems, including improving bearing capacity, decreasing settlement, forming seals, and stabilizing slopes. One of the difficulties faced by designers is determining the strength and geometry of elements created using this method. Jet grouted soil-cement columns in soil are a complicated issue because they are dependent on a number of parameters such as soil type, grout and water flow rate, rotation and lifting speed of monitor, nozzle jetting force, and water to cement ratio of slurry. This paper discusses the effect of the water-cement ratio on the physical and mechanical characteristics of soilcrete. In the laboratory, sandy soil mixed with cement grout with water-cement ratio varies from (0.7:1 to 1.4:1). To evaluate the characteristics of soilcrete, 96 specimens were prepared in the laboratory and tested at different curing times. The results indicate that the Uniaxial Compressive Strength (UCS) of soilcrete decreases with increasing the (W/C) ratio of the grout, where the soilcrete strength of W/C ratio of 0.7 is higher about 237% of W/C ratio of 1.4 at 28-day; the evolution of the (UCS) is proportional to the logarithm of the curing time; the ratio between the modulus of elasticity (Etg50) to the maximum UCS varies from 113 to 175; when the water-cement ratio increases, the dry density of soilcrete decreases, as a result, the (USC) of soilcrete decreases.

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.

Effect of concrete mixing parameters on propagation of ultrasonic waves

The neutralization model of concrete corroded by CO₂ and SO₂ coupling was established. The model considered the dissolution process of solid calcium in concrete and the expansion damage caused by sulfation products. The influence of different water-cement ratios (0.37, 0.47, 0.57) on the neutralization process of concrete was studied. The changes of neutralization degree, gas diffusion coefficient, porosity, CaCO₃ content and CaSO₄ content of corroded concrete were analyzed. The results showed that with the increase of water-cement ratio, the diffusion range of CO₂ gas in concrete gradually increased, while the diffusion range of SO₂ was almost the same. After 28 days of corrosion, with the decrease of the water-cement ratio of concrete, the decrease in porosity of concrete increased gradually, and the expansion damage in concrete with different water-cement ratios was almost the same. In the area of increasing porosity, the change trends of concrete porosity were similar. With the increase of the water-cement ratio, the length of the complete sulfation area of concrete increased, the length of the partial sulfation area decreased, and the length of the partial carbonation area of concrete gradually increased.

Improving latent heat storage capacity of polyethylene glycol/cement composite prepared via solution blending method

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.

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.

A water tank is used to store water to surge over the daily requirement. In the construction of concrete structure for the storage of water and other liquids the imperviousness of concrete is most essential. The permeability of any uniform and thoroughly compacted concrete of given mix proportions is mainly dependent on water cement ratio. The increase in water cement ratio results in increase in the permeability. The decrease in water cement ratio will therefore be desirable to decrease the permeability, but very much reduced water cement ratio may cause compact ion difficulties and prove to be harmful also. Design of liquid holding structure has to be based on the anticipation of cracking in the concrete having regard to its tensile strength. Cracks can be prevented by avoiding the use of thick timber shuttering which prevent the easy escape of heat of hydrate ion from the concrete mass the risk of cracking can also be minimized by reducing the restraints on free expansion or contraction of the structure.

Recently, the use of recycled plastic waste in civil engineering applications has been increased. This paper aims to investigate the effect of water-cement ratio on the compressive strength of concrete that contents 2.5 % polypropylene (PP) as plastic waste. Two references concrete mixes were prepared. The first mix had a water-cement ratio of 0.45 with 2.5% plastic waste, the second mix with 0.45 water cement ratio but without plastic waste. Three concrete mixes with water cement ratios of (0.5, 0.4, and 0.3) were also used as parametric study cases. The results indicated that decreasing the water-cement ratio from 0.45 to 0.4 increases the compressive strength by 20.2%. Also, the compressive strength increases by 36.2% with decreasing of water cement ratio from 0.45 to 0.3. While the compressive strength decreases by 12% with the increase of water-cement ratio from 0.45 to 0.5.