Variation in Concrete Strength Due to Water and Air Content Variation

2014 ◽  
pp. 17-22
Keyword(s):  
Concrete Strength ◽  
Air Content ◽  
Content Variation

scholarly journals THE INFLUENCE OF COARSE AGGREGATE CONCENTRATION ON THE STRENGTH OF CONCRETE AND ON THE POROSITY OF CONCRETE MORTAR/STAMBIOJO UŽPILDO KONCENTRACIJOS ĮTAKA BETONO STIPRUMUI IR SKIEDININĖS DALIES PORINGUMUI

2001 ◽  
Vol 7 (6) ◽  
pp. 446-452
Author(s):  
Gintautas Skripkiūnas ◽  
Vitoldas Vaitkevičius
Keyword(s):  
Stress Concentration ◽  
Water Absorption ◽  
Water Content ◽  
Coarse Aggregate ◽  
Concrete Strength ◽  
Structural Defects ◽  
Capillary Porosity ◽  
Air Content ◽  
Aggregate Concentration ◽  
Entrained Air

The results of experiments dealing with coarse aggregate concentration influence on the concrete strength and the structure of hardened cement paste and mortar of concrete are presented in the paper. Experiments were performed on concrete with dense coarse aggregate (crushed granite) which strength is more than strength of mortar and lightweight porous aggregate (expanded clay aggregate) with strength less than that of mortar. Physical and mechanical properties of concrete with dense coarse aggregate are presented in Table 1 and the concretes with the porous coarse aggregate in Table 2. The decrease of entrained air content with the increase of coarse aggregate concentration ϕσt were determined both for concretes with dense and porous coarse aggregate. The entrained air has a significant effect on concrete strength—1% of entrained air decreases the strength of concrete about 5% [11]. The influence of the coarse aggregate concentration on the compressive strength of concrete with the constant air content is presented in Figs 3 and 4. With the increase of coarse aggregate concentration the concrete strength decreases when the entrained air content in concrete is constant. The main reasons of the concrete strength reduction are the stress concentration and structural defects near the coarse aggregate. Coarse aggregate affects the structure of mortar. Dense coarse aggregate has negligible water absorption and does not change water content in mortar of concrete, and capillary porosity of mortar remains constant when the concentration of dense coarse aggregate ϕ st increases (Fig 5). Porous coarse aggregate (expanded clay aggregate) has large water absorption (more than 16%), therefore water content in mortar of concrete is reduced and capillary porosity of mortar is significantly reduced when the concentration of porous coarse aggregate ϕ st increases (Fig 5). The entrained air content in mortar with both dense and porous coarse aggregate decreases inverse proportionally to coarse aggregate concentration ϕ st (Fig 6). The investigations have shown that suitable selection of properties and volumetric concentration of coarse aggregate can reduce stress concentration in concrete and increase the concrete strength.

scholarly journals Maleic Rosin-based Gemini Surfactant as Air Entraining Agent for Concrete under Low Air Pressure

2021 ◽  
Vol 72 (2) ◽  
pp. 27-37
Author(s):  
Yang Li ◽  
Zhendi Wang ◽  
Ling Wang
Keyword(s):  
Dynamic Modulus ◽  
Gemini Surfactant ◽  
Fresh Concrete ◽  
Concrete Strength ◽  
Air Pressure ◽  
Test Results ◽  
Bubble Liquid ◽  
Air Content ◽  
Spacing Factor ◽  
Plateau Area

The effectiveness of Air entraining agent (AEA) in concrete under low air pressure in the plateau area decreased. A type of new AEA, named MRE was synthesized to increase bubbles` stability in fresh concrete under low air pressure. The performance of MRE solution and concrete with MRE were tested under 60 kPa and 100 kPa compared with commercially gemini AEA (DCC). The test results showed that the foam volume of MRE and DCC solution under 60 kPa was reduced by 3% and 9% than under 100 kPa. The bubble liquid film strength of MRE is 63% higher than that of DCC. For concrete with MRE and DCC under 60 kPa, the air content was 2% and 16% lower, the relative dynamic modulus of concrete reduced by 6% and 15%, and the bubble spacing factor under 60 kPa increased by 17% and 39% respectively compared with that under 100 kPa. MRE can increase the freeze-thaw resistance of concrete under low air pressure without affecting concrete strength and is suitable for high altitude concrete.

Investigation of Critical Quality Assurance Parameter Variations for Concrete

1997 ◽  
Vol 1575 (1) ◽  
pp. 92-101
Author(s):  
Richard K. Smutzer ◽  
Sedat Gulen ◽  
Youlanda K. Belew ◽  
Virgil L. Anderson
Keyword(s):  
High Pressure ◽  
Quality Assurance ◽  
Flexural Strength ◽  
Concrete Strength ◽  
Pulse Velocity ◽  
Hardened Concrete ◽  
Army Corps ◽  
Split Tensile Strength ◽  
Air Content ◽  
Concrete Mix

The Indiana Department of Transportation is involved in preparing statistically sound specifications for strong and durable concrete used in quality assurance programs. Previous laboratory studies relating concrete strength to air content and concrete mix designs dealt with variation in compressive strength. This study searched for a statistically sound relationship between air content, concrete mix designs, and flexural strength. This study also developed a high-pressure method of hardened concrete air content determination. Sixty-four independent batches (combinations) of concrete were produced, each batch was subjected to a total of 24 tests—4 plastic and 20 hardened. The design factors were aggregate type and gradation, plastic air content, cement, and pozzolanic content and testing operator. After plastic testing, three flexural strength beams were cast from each batch of concrete. The experimental design response variables consisted of flexural, compressive, and split tensile strength along with pulse velocity. Analysis of variances, indicated that the optimum flexural strength could be obtained using as-received stone course aggregate and an air content of between 6 percent and 7.9 percent, with no fly ash. A high-pressure air meter, similar to the meter developed by the Army Corps of Engineers, was used. A strong statistical correlation of determination, r2 = 0.94, was obtained between plastic and the hardened concrete air content using this meter.

scholarly journals Durability Evaluation of Concrete with Multiadmixtures under Salt Freeze-Thaw Cycles Based on Surface Resistivity

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Shibin Luo ◽  
Wei Liang ◽  
Hua Wang ◽  
Wensheng Wang ◽  
Rongjun Zou
Keyword(s):  
Flexural Strength ◽  
Concrete Strength ◽  
Air Entrainment ◽  
Surface Resistivity ◽  
Mineral Admixtures ◽  
Chloride Permeability ◽  
Freeze Thaw ◽  
Air Content ◽  
Rapid Chloride Permeability ◽  
Function Relationship

According to the climatic characteristics of seasonal frozen area in northeast China, the concrete strength tests, surface resistivity, rapid chloride permeability, and freeze-thaw test under salt solution were carried out to study the influences of mineral admixtures and air content on the conventional properties and salt freeze-thaw resistance of concretes. Then, the correlation analysis of surface resistivity with strength and rapid chloride permeability were further investigated. Subsequently, the changes of cumulative mass loss and relative dynamic elastic modulus varying with salt freeze-thaw cycles were analyzed to study the influences of mineral admixtures and air content on salt freeze-thaw resistance of concrete. The test results showed that fly ash (FA) was not conducive to improve the strength and salt freeze-thaw resistance of concrete. However, blast furnace slag (BFS) and silica fume (SF) could improve the compressive and flexural strength of concrete, in which SF can improve its strength more significantly. Increasing the air content of concrete will lead to the reduction of its compressive strength, and the flexural strength first increased and then decreased. Nevertheless, the addition of air-entrainment agent (AEA) has the best effect on improving the salt freeze-thaw resistance of concrete. Moreover, surface resistivity of concrete has a good exponential function relationship with strength and a good power function relationship with rapid chloride permeability. Therefore, it is of great significance for engineering quality control and quickly and nondestructive testing.

scholarly journals INFLUENCE OF VISCOSITY MODIFYING AGENT ON SOME RHEOLOGICAL PROPERTIES, SEGREGATION RESISTANCE AND COMPRESSIVE STRENGTH OF SELF-COMPACTING CONCRETE

2013 ◽  
Vol 19 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Anna M. Grabiec
Keyword(s):  
Compressive Strength ◽  
Rheological Properties ◽  
Concrete Strength ◽  
Vertical Direction ◽  
Reference Level ◽  
Hardened Concrete ◽  
Self Compacting Concrete ◽  
Modifying Agent ◽  
Air Content ◽  
Concrete Mix

Rheological properties of self-compacting concrete mixes containing a viscosity modifying agent (VMA) in their composition were studied. After preliminary studies self-compacting concrete mixes and, particularly, a fluid concrete mix prone to segregation of its ingredients were chosen. VMA was added in various amounts to that concrete mix to check how it performed in fresh and hardened concrete. Main studies focused on the influence of VMA on the following properties of concrete mixes: the slump flow, the flow time into the diameter of 500 mm and the resistance to segregation in the vertical direction. Moreover, the air content of concrete mixes and the 28-day compressive strength of concrete were measured. Test results showed that VMA significantly influenced the rheological properties of concrete mix, stabilised it and reduced the segregation. It was proved, that the concrete mix modified by VMA used in the optimal amount, featured the smallest scatter of concrete strength results. Besides, the Tukey's test showed that a reduction of the concrete compressive strength is possible to be statistically insignificant when compared to the reference level.

scholarly journals Towards Better Understanding of Concrete Containing Recycled Concrete Aggregate

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Hisham Qasrawi ◽  
Iqbal Marie
Keyword(s):  
Concrete Strength ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
Normal Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Air Content ◽  
Significant Difference

The effect of using recycled concrete aggregates (RCA) on the basic properties of normal concrete is studied. First, recycled aggregate properties have been determined and compared to those of normal aggregates. Except for absorption, there was not a significant difference between the two. Later, recycled aggregates were introduced in concrete mixes. In these mixes, natural coarse aggregate was partly or totally replaced by recycled aggregates. Results show that the use of recycled aggregates has an adverse effect on the workability and air content of fresh concrete. Depending on the water/cement ratio and on the percent of the normal aggregate replaced by RCA, the concrete strength is reduced by 5% to 25%, while the tensile strength is reduced by 4% to 14%. All results are compared with previous research. As new in this research, the paper introduces a simple formula for the prediction of the modulus of elasticity of RCA concrete. Furthermore, the paper shows the variation of the air content of RAC.

Influence of Air Content on the Compressive Strength of Concrete

2012 ◽  
Vol 535-537 ◽  
pp. 1790-1793
Author(s):  
Rui Ying Bai ◽  
Ji Wei Cai ◽  
Ji Xu Wu ◽  
Gong Lei Wei
Keyword(s):  
Compressive Strength ◽  
Concrete Strength ◽  
The Other ◽  
Strength Grade ◽  
Air Content ◽  
Other Hand ◽  
Compressive Strength Of Concrete

The influence of air content on compressive strength of C20，C30，C40 and C50 concrete was investigated in this paper. The result shows that this relationship varied with concrete strength grade. For C20~C40 concrete, the air content increases with addition of air entraining agent, while a maximum air content value appears for C50 concrete. The compressive strength of C20 decrease slightly with the air content, on the other hand, that of C40 significantly decreases relatively.

Vibrating Mixing and the Improvement of Concrete Performance

2013 ◽  
Vol 652-654 ◽  
pp. 1260-1264
Author(s):  
Liang Qi Zhang ◽  
Zhong Xu Feng ◽  
Li Ping Zhao
Keyword(s):  
Uniform Distribution ◽  
Velocity Gradient ◽  
Mixing Time ◽  
Concrete Strength ◽  
Connection Strength ◽  
Material Particle ◽  
Air Content ◽  
The Common ◽  
Low Efficiency ◽  
Forced Mixing

Velocity gradient and low efficiency zone exist in the common forced mixing. The linear velocity of mixing is low, and the mixing time is long. The concrete has poor micro uniformity. The interface bonded strength and the durability are low. Based on the deficiency of common forced mixing, we put forward vibrating mixing technology and have successfully developed a device. The device adopts the method of forced mixing and vibrating mixing combined, which makes the material particle own certain vibrating frequency and present in vibrating status not only to destroy the sticky connection of mixture, but also reduce friction in materials to promote materials from clusters into uniform distribution. Meanwhile, the device improves micro uniformity and interface connection strength of concrete, and air content of concrete can reach above 3%. The mixing time is shorter and the cement dosage is fewer under the condition of invariable concrete strength.

Examination of moisture content variation within an operational wet deck

TAPPI Journal ◽  
2013 ◽  
Vol 12 (1) ◽  
pp. 45-50 ◽  
Author(s):  
LAURENCE SCHIMLECK ◽  
KIM LOVE-MYERS ◽  
JOE SANDERS ◽  
HEATH RAYBON ◽  
RICHARD DANIELS ◽  
...  
Keyword(s):  
Moisture Content ◽  
Southeastern United States ◽  
Forest Products ◽  
Time Domain Reflectometry ◽  
Water Application ◽  
Wood Moisture ◽  
International Paper ◽  
Content Variation ◽  
Moisture Variation

Many forest products companies in the southeastern United States store large volumes of roundwood under wet storage. Log quality depends on maintaining a high and constant wood moisture content; however, limited knowledge exists regarding moisture variation within individual logs, and within wet decks as a whole, making it impossible to recommend appropriate water application strategies. To better understand moisture variation within a wet deck, time domain reflectometry (TDR) was used to monitor the moisture variation of 30 southern pine logs over an 11-week period for a wet deck at the International Paper McBean woodyard. Three 125 mm long TDR probes were inserted into each log (before the deck was built) at 3, 4.5, and 7.5 m from the butt. The position of each log within the stack was also recorded. Mixed-effects analysis of variance (ANOVA) was used to examine moisture variation over the study period. Moisture content varied within the log, while position within the stack was generally not significant. The performance of the TDR probes was consistent throughout the study, indicating that they would be suitable for long term (e.g., 12 months) monitoring.

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