scholarly journals Influence of Air Temperature on the Performance of Different Water-Reducing Admixtures with Respect to the Properties of Fresh and Hardened Mortar

2010 ◽  
Vol 2010 ◽  
pp. 1-10 ◽  
Author(s):  
Wilson Ricardo Leal Silva ◽  
Luiz Roberto Prudêncio ◽  
Alexandre Lima Oliveira ◽  
Gabriela Damo ◽  
Eduardo Tochetto
Keyword(s):  
Compressive Strength ◽  
Air Temperature ◽  
Cement Hydration ◽  
Weather Conditions ◽  
Concrete Mixture ◽  
Test Mixture ◽  
Air Content ◽  
Retarding Effect ◽  
Flow Table ◽  
Different Temperatures

The performance of water-reducing admixtures used in concrete is affected by the weather conditions to which the concrete mixture is exposed. The most used WRAs are lignosulfonate, naphthalene, and polycarboxylate. However, they react differently to weather conditions, especially to air temperature. Therefore, it can be useful to evaluate how temperature affects admixture performance. In this study, the performance of three admixtures (naphthalene, lignosulfonate, and polycarboxylate) was evaluated at 15, 25, and 35°C by means of the flow table test, mixture air content, and compressive strength. Moreover, mixture temperature was monitored and time-temperature curves were plotted in order to assess whether the admixtures affected cement hydration reactions at different temperatures. The final results indicate that an increase in temperature leads to an increase in saturation dosage; lignosulfonate had the most pronounced retarding effect, followed by polycarboxylate, and finally, naphthalene, and considering the weather conditions in the area where the study was carried, the final finding would be that the naphthalene-based admixture had the best performance.

scholarly journals The Influence of Ambient Temperature on High Performance Concrete Properties

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4646
Author(s):  
Alina Kaleta-Jurowska ◽  
Krystian Jurowski
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
Curing Temperature ◽  
Hardened Concrete ◽  
Water Penetration ◽  
Ambient Temperatures ◽  
Freeze Thaw ◽  
Air Content ◽  
Flow Table

This paper presents the results of tests on high performance concrete (HPC) prepared and cured at various ambient temperatures, ranging from 12 °C to 30 °C (the compressive strength and concrete mix density were also tested at 40 °C). Special attention was paid to maintaining the assumed temperature of the mixture components during its preparation and maintaining the assumed curing temperature. The properties of a fresh concrete mixture (consistency, air content, density) and properties of hardened concrete (density, water absorption, depth of water penetration under pressure, compressive strength, and freeze–thaw durability of hardened concrete) were studied. It has been shown that increased temperature (30 °C) has a significant effect on loss of workability. The studies used the concrete slump test, the flow table test, and the Vebe test. A decrease in the slump and flow diameter and an increase in the Vebe time were observed. It has been shown that an increase in concrete curing temperature causes an increase in early compressive strength. After 3 days of curing, compared with concrete curing at 20 °C, an 18% increase in compressive strength was observed at 40 °C, while concrete curing at 12 °C had a compressive strength which was 11% lower. An increase in temperature lowers the compressive strength after a period longer than 28 days. After two years of curing, concrete curing at 12 °C achieved a compressive strength 13% higher than that of concrete curing at 40 °C. Freeze–thaw performance tests of HPC in the presence of NaCl demonstrated that this concrete showed high freeze–thaw resistance and de-icing materials (surface scaling of this concrete is minimal) regardless of the temperature of the curing process, from 12 °C to 30 °C.

Properties of Polyacrylic Ester Latex Modified Cement Mortar

2013 ◽  
Vol 687 ◽  
pp. 166-174 ◽  
Author(s):  
Zhen Ping Sun ◽  
Dan Mei Ye ◽  
Le Feng Fu ◽  
Bo Cun Zheng ◽  
Zhong Jun Feng ◽  
...  
Keyword(s):  
Adverse Effect ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Cement Mortar ◽  
Air Entrainment ◽  
Hydration Process ◽  
Air Content ◽  
Retarding Effect ◽  
Polyacrylic Ester

The water reducing performance, retarding effect, air entrainment, flexural and compressive strength of polyacrylic ester (PAE) latex modified cement mortar were investigated with fixed flow values. The research shows that PAE latex has water-reducing performance. The amount of water used in modified cement mortar decreases with increasing dosage of PAE latex. Because of the retarding effect, PAE latex delays the hydration process of cement. PAE latex has a strong effect of air entraining, and the air content of fresh mortar can be controlled by suitable dosage of defoamer. With the same air content of fresh mortar, PAE latex can obviously improve the flexural strength of cement mortar, and has no adverse effect on its compressive strength.

Influence of Triethanolamine on the Properties of Cement-Based Materials

2017 ◽  
Vol 898 ◽  
pp. 2010-2017 ◽  
Author(s):  
Xiao Ying Wang ◽  
Ming Zhang Lan ◽  
Wei Fang Hou ◽  
Bin Feng Xiang ◽  
Xu Dong Zhao
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Cement Hydration ◽  
Setting Time ◽  
Cementitious Materials ◽  
Hydration Products ◽  
Initial Setting Time ◽  
Final Setting Time ◽  
Retarding Effect ◽  
Initial Setting

The effects of triethanolamine on the compressive strength and setting time of fly ash cementitious materials, slag cementitious materials, and limestone cementitious materials were investigated. The results show that the dosage of 0.04% of triethanolamine can significantly improve the 3d, 7d and 28d compressive strength of fly ash cementitious materials. It possesses less impact on the setting time. The dosage of 0.04% of triethanolamine can significantly improve the 3d and 7d compressive strength of slag cementitious materials while the effect of late strength is not obvious. It extends the initial setting time and the final setting time is not changed, which has retarding effect. The results of hydration heat and XRD show that triethanolamine extends the induction period of cement hydration, and gypsum is exhausted in advance during the hydration process. Triethanolamine promotes the transformation of AFt to AFm and there is no effect on the type of hydration products.

A Rule-Breaking Approach to a Better Understanding of the Method of Tests for Slump, Air Content and Compressive Strength

2019 ◽  
Vol 57 (6) ◽  
pp. 433-440
Author(s):  
S. Komatsu ◽  
Y. Kondo ◽  
N. Ikawa ◽  
C. Hashimoto
Keyword(s):  
Compressive Strength ◽  
Air Content ◽  
Rule Breaking

scholarly journals Effect of Morphologically Controlled Hematite Nanoparticles on the Properties of Fly Ash Blended Cement

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1003
Author(s):  
Pantharee Kongsat ◽  
Sakprayut Sinthupinyo ◽  
Edgar A. O’Rear ◽  
Thirawudh Pongprayoon
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Size Distribution ◽  
Cement Hydration ◽  
Blended Cement ◽  
Spherical Shape ◽  
Particle Sizes ◽  
Fe2o3 Nanoparticles ◽  
Structure And Properties ◽  
Hematite Nanoparticles

Several types of hematite nanoparticles (α-Fe2O3) have been investigated for their effects on the structure and properties of fly ash (FA) blended cement. All synthesized nanoparticles were found to be of spherical shape, but of different particle sizes ranging from 10 to 195 nm depending on the surfactant used in their preparation. The cement hydration with time showed 1.0% α-Fe2O3 nanoparticles are effective accelerators for FA blended cement. Moreover, adding α-Fe2O3 nanoparticles in FA blended cement enhanced the compressive strength and workability of cement. Nanoparticle size and size distribution were important for optimal filling of various size of pores within the cement structure.

Effects of Loading Percentage of Polyurethane in Lightweight Concrete

2013 ◽  
Vol 357-360 ◽  
pp. 1082-1085 ◽  
Author(s):  
Kamarul Aini Mohd Sari ◽  
Sohif Mat ◽  
Khairiah Haji Badri ◽  
Muhammad Fauzi Mohd Zain
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Lightweight Concrete ◽  
Palm Kernel ◽  
Physical And Mechanical Properties ◽  
Concrete Mixture ◽  
Experimental Program ◽  
Polymer Concrete ◽  
Optimum Level ◽  
Methylene Diphenyl Diisocyanate

An experimental program was performed to obtain the density, compressive strength, and thermal conductivity of palm-based lightweight concrete. Palm-based polyurethane (PU) particles were used as lightweight aggregates in creating concrete systems. Concrete systems contain palm kernel oil-based polyol (PKO-p) reacted with 2,4-methylene diphenyl diisocyanate (MDI). In this study, polymer concrete was improved to achieve the optimum level of PU with the lowest possible density. The PU particles in the concrete mixture comprised of 1% to 5% w/w with density of less than 1800 kg/m3. The PU particles were 5 mm in size. The ratio of PKO-p to MDI was set at 1:1 and the loading of the concrete mixture was set at 3% w/w to produce lightweight concrete. The resulting concrete has excellent compressive strength (17.5 MPa) and thermal conductivity (0.24 W/mK). Results show that the PU particle dosage has the most significant effect on the physical and mechanical properties of concrete.

Modelling pavement temperature for winter maintenance operations

2004 ◽  
Vol 31 (2) ◽  
pp. 369-378 ◽  
Author(s):  
Aly Sherif ◽  
Yasser Hassan
Keyword(s):  
Surface Temperature ◽  
Air Temperature ◽  
Negative Impact ◽  
Weather Conditions ◽  
Statistical Modelling ◽  
Dew Point ◽  
Road Maintenance ◽  
Winter Maintenance ◽  
Pavement Surface ◽  
Pavement Temperature

Road and highway maintenance is vital for the safety of citizens and for enabling emergency and security services to perform their essential functions. Accumulation of snow and (or) ice on the pavement surface during the wintertime substantially increases the risk of road crashes and can have negative impact on the economy of the region. Recently, road maintenance engineers have used pavement surface temperature as a guide to the application of deicers. Stations for road weather information systems (RWIS) have been installed across Europe and North America to collect data that can be used to predict weather conditions such as air temperature. Modelling pavement surface temperature as a function of such weather conditions (air temperature, dew point, relative humidity, and wind speed) can provide an additional component that is essential for winter maintenance operations. This paper uses data collected by RWIS stations at the City of Ottawa to device a procedure that maximizes the use of a data batch containing complete, partially complete, and unusable data and to study the relationship between the pavement surface temperature and weather variables. Statistical models were developed, where stepwise regression was first applied to eliminate those variables whose estimated coefficients are not statistically significant. The remaining variables were further examined according to their contribution to the criterion of best fit and their physical relationships to each other to eliminate multicollinearities. The models were further corrected for the autocorrelation in their error structures. The final version of the developed models may then be used as a part of the decision-making process for winter maintenance operations.Key words: winter maintenance, pavement temperature, statistical modelling, RWIS.

Self-Toughness Porous Sodium Titanate Bioceramics Prepared via In Situ Grown Na2Ti6O13 Rods

2017 ◽  
Vol 727 ◽  
pp. 806-814 ◽  
Author(s):  
Xiao Wei Ma ◽  
Jian Xing Shen ◽  
Ke Chang Zhang ◽  
Ling Kai Kong ◽  
Jia Le Sun ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Compressive Strength ◽  
Sodium Titanate ◽  
The Novel ◽  
Ceramic Samples ◽  
Porous Bioceramic ◽  
Different Temperatures ◽  
Growth Method ◽  
Titanate Ceramics

Here in, we report the porous bioceramic with Na2Ti6O13 rods prepared by in‒situ growth method. The samples were prepared using cold uniaxial pressing (40 MPa) technique and further sintered at different temperatures. The structure and morphology were characterized by XRD and SEM. The porosity, compressive strength and fracture toughness were also investigated. The bone-like apatite deposition ability of the fabricated ceramic samples was evaluated by Kokubo simulated body fluid (SBF) soaking method. The results indicated that the Na2Ti6O13 rods with about 1‒3 μm in diameter are uniformly distributed in the self‒toughness porous sodium titanate ceramics (SPSTC). The SPSTC with a porosity of 61.10±1.12 % exhibits good compressive strength (43.36±2.43 MPa) and fracture toughness (3.47±0.21 MPa·m1/2). The results indicate that the novel SPSTC scaffolds are promising for bone tissue engineering applications.

When, where and why do people encounter Australian brownsnakes (Pseudonaja textilis : Elapidae)?

1999 ◽  
Vol 26 (5) ◽  
pp. 675 ◽  
Author(s):  
P. B. Whitaker ◽  
R. Shine
Keyword(s):  
Air Temperature ◽  
Agricultural Land ◽  
New South ◽  
Habitat Type ◽  
Weather Conditions ◽  
Time Of Day ◽  
South Wales ◽  
Experienced Observer ◽  
Close Proximity ◽  
Species Ecology

Encounters between humans and dangerously venomous snakes put both participants at serious risk, so the determinants of such encounters warrant attention. Pseudonaja textilis is a large fast-moving elapid snake responsible for most snakebite fatalities in Australia. As part of a broad ecological study of this species in agricultural land near Leeton, New South Wales, we set out to identify factors influencing the probability that a human walking in farmland would come into close proximity to a brownsnake. Over a three-year period, we walked regular transects to quantify the number and rate of snake encounters, and the proportion of snakes above ground that could be seen. The rate of encounters depended upon a series of factors, including season, time of day, habitat type, weather conditions (wind and air temperature) and shade (light v. dark) of the observers’ clothing. Interactions between factors were also important: for example, the effect of air temperature on encounter probability differed with season and snake gender, and the effect of the observers’ shade of clothing differed with cloud cover. Remarkably, even a highly-experienced observer actually saw <25% of the telemetrically monitored snakes that were known to be active (i.e. above ground) nearby. This result reflects the snakes’ ability to evade people and to escape detection, even in the flat and sparsely vegetated study area. The proportion of snakes that were visible was influenced by the same kinds of factors as described above. Most of the factors biasing encounter rates are readily interpretable from information on other facets of the species’ ecology, and knowledge of these factors may facilitate safer coexistence between snakes and people.

scholarly journals Cars as next generation mobile weather stations: an initial investigation

2021 ◽  
Author(s):  
Giuliano Andrea Pagani ◽  
Marcel Molendijk ◽  
Jan Willem Noteboom
Keyword(s):  
Air Temperature ◽  
Weather Conditions ◽  
Ground Temperature ◽  
Warning Systems ◽  
Traction Control ◽  
The Future ◽  
Weather Stations ◽  
Temporal And Spatial ◽  
Positive Correlation Coefficient ◽  
Digital Equipment

&lt;p&gt;Modern automobiles are becoming more and more &amp;#8220;computers on the wheels&amp;#8221; having lots of digital equipment on board. Such equipment is both for the comfort and entertainment of the passengers and for their safety. Sensors play a key role in measuring several parameters of the car performance (e.g., traction control, anti-lock breaking system) and also environmental &amp;#160;parameters are observed directly (e.g., air temperature) or can be somehow inferred (e.g., precipitation via windscreen wipers activity/speed).&lt;/p&gt;&lt;p&gt;KNMI has been provided air temperature recorded every 10 minutes by thousands of vehicles driving in the Netherlands for the period January-October 2020. We have performed an initial exploratory temporal and spatial analysis to understand the most promising periods of the day and areas where sufficient data is available to perform a more thorough data analysis in the future. Furthermore, we have performed a correlation analysis between the outside temperature measured by cars and air and ground temperature observed by official weather station sensors placed at one location on the Dutch highways. The correlation results for three randomly selected days (with different weather conditions) show a good positive correlation coefficient ranging from 0.93 to 0.76 for car and station air temperature and from 0.91 to 0.67 for car temperature and station ground temperature.&lt;/p&gt;&lt;p&gt;This initial exploration paves the way to the use of (OEM) car data as (mobile) weather stations. We foresee in the future to use a combination of sensed variables from cars such as air temperature, traction control, windscreen wipers activity for example to improve observations of road slipperiness and related warning systems that are not restricted to Dutch highways only.&lt;/p&gt;

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