Research on Fresh Concrete Water-Cement Ratio Based on Resistivity Method

2016 ◽  
Vol 847 ◽  
pp. 469-475 ◽  
Author(s):  
Hai Bo Ren ◽  
Jian Yin ◽  
Zheng Hui Sang ◽  
Ting Gao
Keyword(s):  
Fresh Concrete ◽  
Mineral Admixture ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Resistivity Method ◽  
Concrete Quality ◽  
Resistivity Variation ◽  
The Law ◽  
Concrete Resistivity ◽  
The Impact

Water-cement ratio is an important parameter of concrete quality. Rapid measurement of fresh concrete water-cement ratio can effectively monitor the on-site concrete quality management and play a great role in quality control. We study the variation of fresh concrete resistivity with the aid of electrodeless cement concrete resistivity meter, and discuss the impact of water-cement ratio under different varieties of cement, mineral admixture, chemical admixtures conditions on fresh concrete resistivity. We establish the relationships between fresh concrete resistivity and water-cement ratio based on the law of Portland cement initial hydration resistivity. The studies show that: fresh concrete resistivity is most vulnerable to the changes of water-cement ratio; there is a correlation between the law of fresh concrete resistivity and water-cement ratio; according to the fresh concrete resistivity variation, we can quickly identify water-cement ratio, cement and other parameters.

Microscopic Mechanism of the Diffusivity of Concrete Chloride Ion

2013 ◽  
Vol 773 ◽  
pp. 687-692 ◽  
Author(s):  
Jun Liu ◽  
Feng Xing ◽  
Bi Qing Dong
Keyword(s):  
Fly Ash ◽  
Early Stage ◽  
Great Influence ◽  
Chloride Ion ◽  
Test Method ◽  
Mineral Admixture ◽  
Microscopic Mechanism ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
The Impact

Use concrete specimens with different mix proportions to conserve them for 90d taking into account the influence of mineral admixture material---fly ash. Then adopts the RCM test method to measure the rapid diffusivity of chloride ion of concrete and observes the microstructure of the cement paste using the SEM (scanning electron microscopy), aiming to study the impact of fly ash on its hydration process. The results show that the micro-pore structure of the concrete has a great influence on the rapid diffusivity of chloride ion, while its diffusivity is closely related with the water-cement ratio of concrete; after the fly ash is added, the ettringite generation of the concrete in the early stage decreases, and the interspace of the transition zone between the hydrated particles and hydration slurry is enlarged, coupled with the increase in the intercommunicating pore; after curing for 90d, the chloride ion diffusivity decreases significantly with the increase in the dosage of fly ash. For the concrete with the fly ash dosage of 15%, its chloride ion diffusivity is only 75.4% of that with the same water-cement ratio; when its fly ash content is 30%, its chloride ion diffusivity is only 32.3% of the ordinary concrete.

scholarly journals Effect of Water Cement Ratios on Compressive Strength of Palm Kernel Shell Concrete

2019 ◽  
Vol 2 (Issue 1) ◽  
Author(s):  
A.O Adeyemi ◽  
M.A Anifowose ◽  
I.O Amototo ◽  
S.A Adebara ◽  
M.Y Olawuyi
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Fresh Concrete ◽  
Palm Kernel ◽  
Hardened Concrete ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Palm Kernel Shell ◽  
Compressive Strength Of Concrete ◽  
Palm Kernel Shells

This study examined the effect of varying water cement ratio on the compressive strength of concrete produced using palm kernel shell (PKS) as coarse aggregate at different replacement levels. The replacement levels of coarse aggregate with palm kernel shells (PKS) were 0%, 25%, 50%, and 100% respectively. PKS concrete cubes (144 specimens) of sizes 150mm x 150mm x 150mm were cast and cured in water for 7, 14, 21 and 28 days respectively. A mix ratio of 1:2:4 was adopted with water-cement ratio of 0.45, 0.5, and 0.6 respectively while the batching was done by weight. Slump test was conducted on fresh concrete while compressive strength test was carried out on the hardened concrete cubes using a compression testing machine of 2000kN capacity. The result of tests on fresh concrete shows that the slump height of 0.45 water cement ratio (w/c) increases with an increase in PKS%. This trend was similar to 0.50 and 0.60 w/c. However, the compressive strength of concrete cube decreases with an increase in w/c (from 0.45 to 0.60) but increases with respect to curing age and also decreases with increase in PKS%. Concrete with 0.45 water-cement ratio possess the highest compressive strength. It was observed that PKS is not a good substitute for coarse aggregate in mix ratio 1:2:4 for concrete productions. Hence, the study suggest the use of chemical admixture such as superplasticizer or calcium chloride in order to improve the strength of palm kernel shells-concrete.

scholarly journals The Influence of Finely Ground Mineral Admixture (FGMA) on Efflorescence

2013 ◽  
Vol 4 (1) ◽  
pp. 50-55 ◽  
Author(s):  
Ong Ming Wei ◽  
Norsuzailina Mohamed Sutan
Keyword(s):  
Calcium Carbonate ◽  
Chemical Analysis ◽  
Mineral Admixture ◽  
Partial Replacement ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Cement Replacement ◽  
Carbonate Formation

Efflorescence phenomenon on concrete is not new and found in the form of white deposits on surfaces of concrete. Incorporation of Finely Ground Mineral Admixture (FGMA) in concrete to prevent occurrence of efflorescence is based on reduction of portlandite, densified microstructure and thus enhanced watertightness. The magnitude of efflorescence in term of percentage of calcium carbonate formation of FGMA modified mortar were evaluated at water-cement ratio of 0.3, 0.4 and 0.5 with 10%, 20%, and 30% of cement replacement by weight. The samples were tested with chemical analysis at 7, 14, 21, 28, 60 and 90 days. The FGMA additions into mortar were comparing with ordinary mortar to evaluate enhanced performance of FGMA modified mortar toward efflorescence. The results of this experiment showed that addition of FGMA into mortar caused less formation of calcium carbonate as partial replacement of cement with certain w/c ratio and percentage of cement replacement.

Revised Method for Rapid Determination of On-Site Water–Cement Ratio using Microwave Oven

2019 ◽  
Vol 2673 (8) ◽  
pp. 1-10
Author(s):  
Seyednavid Mardmomen ◽  
Hung-Liang (Roger) Chen ◽  
Guadalupe Leon
Keyword(s):  
Coarse Aggregate ◽  
Fresh Concrete ◽  
Rapid Determination ◽  
Microwave Oven ◽  
Cementitious Material ◽  
Percentage Error ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Average Percentage ◽  
Site Water

The water–cement ratio (w/c) of delivered concrete is one of the most important parameters of the material’s quality. In this study, the AASHTO T318-15 guideline was adopted to estimate the water content of fresh concrete mixes and was revised for better precision. The additional step required sieving out the coarse aggregate after drying the sample in a microwave oven, and using it in the calculation of the absorbed water and cementitious material content. The cementitious content was assumed to be proportional to the mix design ratios. Several laboratory batches, as well as on-site water–cementitious material (w/cm) ratio tests, were performed on concrete mixes containing ordinary Portland cement, ground-granulated blast furnace slag, and Class F fly ash. The results of the experiments indicated the accuracy of the revised method was increased to have an average percentage error of about 2.16% from the actual w/cm ratio whereas the method based on AASHTO calculations was 6.2%. For cases with high chemical admixture dosages, washing vinegar was used to wash out the particles around the dried sieved coarse aggregate to calculate the w/cm ratio with a more precise mass for each sample. The correlation between the measured and calculated compressive strength using the measured amount of w/cm ratios provides evidence for the method’s accuracy. Therefore, the revised method can be used as an accurate and practical process of measuring the on-site w/cm ratios of fresh concrete mixes.

Kansas Water-Cement Ratio Meter: Preliminary Results

1996 ◽  
Vol 1532 (1) ◽  
pp. 73-79
Author(s):  
Mustaque Hossain ◽  
James Koelliker ◽  
Hisham Ibrahim ◽  
John Wojakowski
Keyword(s):  
Fresh Concrete ◽  
Accurate Determination ◽  
Hardened Concrete ◽  
Cement Slurry ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Concrete Mix ◽  
Predominant Factor ◽  
The One ◽  
Strength And Durability

The water-cement ratio of fresh concrete is recognized as the one factor that affects the strength and durability of an adequately compacted concrete mix. Although water-cement ratio is the predominant factor affecting strength of hardened concrete, currently no widely used, reliable method is available for measuring water-cement ratio in the field. A prototype device has been developed to measure the water-cement ratio of a plastic concrete mix. The method is based on the measurement of turbidity of water-cement slurry separated out of a concrete mixture by pressure sieving. Consistent results were obtained for air-entrained and non-air-entrained concrete. Statistical analyses of the test results have shown that this meter can measure the water-cement ratio of fresh concrete with an accuracy of ±0.01 on the water-cement ratio scale for a single test at a 90 percent confidence interval. The equipment will cost less than $10,000. If the method works as well in the field as it does in the laboratory, accurate determination of water-cement ratio could dramatically improve the ability of the concrete industry to ensure the quality of concrete construction.

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

2013 ◽  
Vol 771 ◽  
pp. 29-33
Author(s):  
Jin Xi Zhang ◽  
Chao Wang ◽  
Ming Yang Guo ◽  
Mao Cheng Ma
Keyword(s):  
Experimental Investigation ◽  
Hardened Concrete ◽  
Cement Concrete ◽  
Marked Rise ◽  
Air Voids ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Influence Of Water ◽  
Air Void ◽  
The Impact

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.

scholarly journals The Assessment of Strength of Cementitious Materials Impregnated Using Hydrophobic Agents Based on Near-Surface Hardness Measurements

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4583
Author(s):  
Martyna Nieświec ◽  
Łukasz Sadowski
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Concrete Structures ◽  
Surface Hardness ◽  
Cementitious Materials ◽  
Schmidt Hammer ◽  
Near Surface ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
The Impact

Recently, the surfaces of concrete structures are impregnated to protect them against the environment in order to increase their durability. It is still not known how the use of these agents affects the near-surface hardness of concrete. This is especially important for experts who use the near-surface hardness of concrete for estimating its compressive strength. The impregnation agents are colorless and, thus, without knowledge of their use, mistakes can be made when testing the surface hardness of concrete. This paper presents the results of investigations concerning the impact of impregnation on the subsurface hardness concrete measured using a Schmidt hammer. For this research, samples of cement paste with a water–cement ratio of 0.4 and 0.5 were used. The samples were impregnated with one, two, and three layers of two different agents. The first agent has been made based on silanes and siloxanes and the second agent has been made based on based on polymers. The obtained research results allow for the conclusion that impregnation affects the near-surface hardness of concrete. This research highlights the fact that a lack of knowledge about the applied impregnation of concrete when testing its near-surface hardness, which is then translated into its compressive strength, can lead to serious mistakes.

Preliminary Study on Reaction of Fresh Concrete with Carbon Dioxide

2018 ◽  
Vol 382 ◽  
pp. 230-234
Author(s):  
Ming Ju Lee ◽  
Ming Gin Lee ◽  
Yung Chih Wang ◽  
Yu Min Su ◽  
Jia Lun Deng
Keyword(s):  
Carbon Dioxide ◽  
Compressive Strength ◽  
Fresh Concrete ◽  
Setting Time ◽  
Cement Matrix ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Short Time

In order to let fresh concrete react with carbon dioxide sufficiently, the carbon dioxide was added to mixing concrete. The study used three water cement ratio (0.55, 0.65, 0.75), three CO2 pressures (0.2, 0.4, 0.6 MPa), and two CO2 concentration (50% and 100%) to make concrete samples, and observed the effect of carbon dioxide adsorption in the above parameters. Finally, the compressive strength and carbonation degree of concretes were tested after three curing time (7, 14 and 28 days). The research showed that concrete could be more efficient to absorb carbon dioxide by using this pressure method. The results found that the mixing concrete react with carbon dioxide in a short time, and shorten the initial setting time of concrete. But this method would greatly reduce the workability of concrete after mixing with carbon dioxide and it might be enhanced by water or superplasticizer. The bond of cement matrix might cut down after reacting with carbon dioxide. Based on the above, the compressive strength of concrete which was mixed with carbon dioxide would be impaired. The proposed CO2-mixing method has the capacity to uptake 9.5% carbon dioxide based on water cement ratio and CO2 pressure.

Effect of Admixed Recycled Aggregate on Properties of Recycled Concrete

2012 ◽  
Vol 174-177 ◽  
pp. 743-746
Author(s):  
Ya Jun Zhao ◽  
Ying Gao ◽  
Li Li He
Keyword(s):  
Compressive Strength ◽  
Design Method ◽  
Orthogonal Design ◽  
Plain Concrete ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Influence Of Water ◽  
The Impact

The mixture proportion of recycled concrete was discussed by orthogonal design method. The influence of water-cement ratio, recycled aggregate quantity on workability, cube compressive strength of recycled concrete was analyzed. The experimental results indicated that，Recycled concrete mix proportion design should consider the impact of the water absorption of recycled aggregate. Unit water amount of recycled concrete should be plain concrete unit water consumption and recycled aggregate additional amount of water. Sand ratio should increase in the corresponding ordinary aggregate concrete sand ratio on the basis of 1 to 3 percent. When the water-cement ratio is 0.36 and construction waste content of 40% slag content of 20%, 28d compressive strength of concrete is 48.1MPa, slightly higher than the reference concrete (48.0MPa).

The Study of the Factors Effecting Bond Strength of Masonry

2014 ◽  
Vol 1065-1069 ◽  
pp. 2011-2016
Author(s):  
Tao Zhang ◽  
Qian Wang
Keyword(s):  
Bond Strength ◽  
Compression Strength ◽  
Hydration Products ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Air Content ◽  
The Impact ◽  
The Relationship

The results of this paper are being summarized in a series of articles categorized into the principal properties of the mortars, for example compression strength, admixtures, air-content and water cement ratio, and the impact of those properties on bond strength were analyzed. The second purpose of this article deals with the relationship between brick’s properties with bond strength. The results shown that those effecting factors mainly through make an influence on the amount of hydration products and the bonded area to determine bond strength.

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