Study of Productivity Improvement on Precast Concrete by Calcium Silicate Hydrate Type Accelerator

2018 ◽  
Vol 936 ◽  
pp. 214-218
Author(s):  
Hiromitsu Koyama ◽  
Toshimi Matsumoto ◽  
Jing Cui ◽  
Shigeyuki Date
Keyword(s):  
Precast Concrete ◽  
Curing Temperature ◽  
Estimation Accuracy ◽  
Efficient Production ◽  
Curing Time ◽  
Steam Curing ◽  
Productivity Improvement ◽  
Maturity Method ◽  
Test Result ◽  
Strength Improvement

The effect of early strength improvement of concrete with C-S-H type accelerator was studied for precast concrete efficient production under the steam curing condition. From the mortar test result, the effect of this improvement was confirmed to tend lager as the W/C is lower. This accelerator could short the curing time for 0.5-2.0 hours under the same temperature condition, and could reduce the curing temperature under the same curing time. Then the compressive strength was considered to be predicted by some formula, and it showed higher estimation accuracy of the Arrhenius’s Law than that of the Maturity Method.

Effect of Type of Cement and Expansive Agent on the Hardening of Steam-Cured Concrete

2017 ◽  
Vol 744 ◽  
pp. 105-113 ◽  
Author(s):  
Takayoshi Maruyama ◽  
Hideaki Karasawa ◽  
Shigeyuki Date
Keyword(s):  
Early Stage ◽  
Precast Concrete ◽  
Curing Temperature ◽  
Steam Curing ◽  
Slag Powder ◽  
Expansive Agent ◽  
Cast Concrete ◽  
Increase Productivity ◽  
Early Strength ◽  
Furnace Slag

Pre-cast concrete products are sometimes manufactured in two cycles daily. It is ensured that they have the required strength at an early stage of demolding by increasing the steam curing temperature to reduce cost or increase productivity. However, the reduction in durability because of cracking due to thermal stress is a topic of concern. On the other hand, it has been known that fine blast-furnace-slag powder and expansive agents show high temperature dependence. Although they are used even in precast concrete products, the effect of steam curing on these materials is not known. Thus, in this study, the expression of compressive strength and expansion that are critical in improving the quality and productivity of precast concrete products was investigated, using high early-strength cement and two types of expansive agents, namely, ettringite-based and lime-based agents. Consequently, the strength expression was accelerated by the addition of expansive agent to ordinary cement and high early-strength cement. The extent of restrained expansion is greater for the lime-based expansive agent than for the ettringite-based expansive agent, and when an expansive agent is added to high early-strength cement, the extent of restrained expansion falls to a level lower than that in the case of ordinary cement.

scholarly journals Application of the High Early Strength Type Expansive Agent to the Blast Furnace Slag Combination Concrete with GGBFS under Steam Curing

2019 ◽  
Vol 278 ◽  
pp. 01005
Author(s):  
Erica Enzaki ◽  
Takashi Sakuma ◽  
Eizou Takeshita ◽  
Shigeyuki Date
Keyword(s):  
Blast Furnace ◽  
Blast Furnace Slag ◽  
Early Stage ◽  
Precast Concrete ◽  
Curing Temperature ◽  
Strength Development ◽  
Steam Curing ◽  
Expansive Agent ◽  
Early Strength ◽  
Furnace Slag

In recent years, the use of blast furnace slag material is being focused as environmental loading reduction and sustainable construction. However, in general, autogeneours shrinkage of the concrete using much amount of GGBFS is large in compared to normal concrete, therefore risk of cracking should be cared. On the other hand, strength development speed of concrete at early stage will be decreasing as the dosage of GGBFS increases, even under steam curing condition. It can be considered these points will be significant disadvantage in both productivity and quality of precast concrete. So in this study, early strength type expansive agent and setting accelerator were used in combination. As a result, it was confirmed that compressive strength at early stage is obviously increased. And steam curing temperature can be reduced about 10 degrees, and also, 600×10-6 of restraint expansion was obtained.

Effets des cendres volantes sur le développement des résistances mécaniques des bétons préfabriqués

1996 ◽  
Vol 23 (4) ◽  
pp. 940-949
Author(s):  
Y. Maltais ◽  
J. Marchand ◽  
R. Gagné ◽  
A. Tagnit-Hamou
Keyword(s):  
Compressive Strength ◽  
Precast Concrete ◽  
Curing Temperature ◽  
Initial Increase ◽  
Thermal Curing ◽  
Portland Cement Concrete ◽  
Concrete Compressive Strength ◽  
Fly Ashes ◽  
Steam Curing ◽  
Curing Regime

The results of an investigation of the influence of fly ashes on the development of mechanical properties of concretes subjected to 24-h thermal curing are presented in this paper. In addition to the curing temperature (23 and 60 °C), the variables studied in this investigation were the type of cement (types 10 and 30) and the source of fly ashes (four different North-American class F fly ashes). Overall, 10 different concrete mixtures were tested. Test results indicate that thermal curing tends to increase significantly the concrete compressive strength in the first 24 h. Data also demonstrate that the thermal curing regime does not have any detrimental effect on the long-term compressive strength of ordinary portland cement concrete. Compressive strength of fly ash concretes was significantly reduced by thermal curing in the 1- to 28-day period, despite an initial increase. The influence of thermal curing on the development of concrete compressive strength is discussed. Key words: compressive strength, steam curing, fly ashes, precast concrete.

scholarly journals Compressive Strength Gain Behavior and Prediction of Cement-Stabilized Macadam at Low Temperature Curing

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yongli Xu ◽  
Guang Yang ◽  
Hongyuan Zhao
Keyword(s):  
Compressive Strength ◽  
Low Temperature ◽  
Curing Temperature ◽  
Strength Development ◽  
Construction Process ◽  
Strength Gain ◽  
Estimation Model ◽  
Maturity Method ◽  
Temperature Ranges ◽  
Natural Temperature

For cement-based materials, the curing temperature determines the strength gain rate and the value of compressive strength. In this paper, the 5% cement-stabilized macadam mixture is used. Three indoor controlled temperature curing and one outdoor natural curing scenarios are designed and implemented to study the strength development scenario law of compressive strength, and they are standard temperature curing (20°C), constant low temperature curing (10°C), day interaction temperature curing (varying from 6°C to 16°C), and one outdoor natural temperature curing (in which the air temperature ranges from 4°C to 20°C). Finally, based on the maturity method, the maturity-strength estimation model is obtained by using and analyzing the data collected from the indoor tests. The model is proved with high accuracy based on the validated results obtained from the data of outdoor tests. This research provides technical support for the construction of cement-stabilized macadam in regions with low temperature, which is beneficial in the construction process and quality control.

Effect of chemical admixtures on the sulfate requirement of cement

1980 ◽  
Vol 7 (2) ◽  
pp. 256-263 ◽  
Author(s):  
M. A. Ward ◽  
S. M. Khalil ◽  
B. W. Langan
Keyword(s):  
Portland Cement ◽  
Initial Temperature ◽  
Precast Concrete ◽  
Steam Curing ◽  
Sulfate Content ◽  
Chemical Admixtures ◽  
Cost Of Energy ◽  
Hot Weather ◽  
The Cost ◽  
Ready Mixed Concrete

As the cost of energy and hence the cost of producing Portland cement increase, the question arises as to whether we are obtaining optimum performance from the admixtures we use. As an example, data are presented indicating that a significant improvement in strength and shrinkage can be achieved by optimizing the sulfate content of the cement for given cement–admixture combinations. It is shown that the optimum SO3 is clearly a function of the initial temperature of the concrete, particularly during the first 24 h after casting, a characteristic of considerable importance in hot weather concreting and steam curing of concrete products. It is recommended that more attention be directed towards optimizing the effectiveness of chemical admixtures in both the ready-mixed concrete and precast concrete industries.

scholarly journals Synthesis of Geopolymer from Inorganic Construction Waste

2013 ◽  
Vol 30 ◽  
pp. 45-51 ◽  
Author(s):  
Arbind Pathak ◽  
Vinay Kumar Jha
Keyword(s):  
Compressive Strength ◽  
Coal Fly Ash ◽  
Chemical Society ◽  
Raw Material ◽  
Curing Temperature ◽  
Alkali Concentration ◽  
Curing Time ◽  
Mass Ratio ◽  
Construction Waste ◽  
Alumino Silicate

Recently, the demolition of old houses and the construction of new buildings in Kathmandu valley are in the peak which in turn generates a huge amount of construction waste. There are two major types of construction wastes which are burden for disposal namely cement-sand-waste (CSW) and the coal fly ash (CFA). These construction wastes are rich source of alumino-silicate and thus used as raw material for the synthesis of geopolymer in this study. Geopolymers have been synthesized from CSW and CFA using NaOH-KOH and Na2SiO3 as activators. Some parameters like alkali concentration, amount of Na2SiO3 and curing time have been varied in order to improve the quality of geopolymeric product. The geopolymerization process has been carried out using 3-8M KOH/NaOH solutions, Na2SiO3 to CFA and CSW mass ratio of 0.25-2.00 and curing time variation from 5-28 days. The curing temperature was fixed at 40ºC in all the cases. 6M NaOH and 7M KOH solutions were found appropriate alkali concentrations while the ratio of sodium silicate to CSW and CFA of 0.5 and 1.75 respectively were found suitable mass ratio for the process of geopolymer synthesis. The maximum compressive strength of only 7.3 MPa after 15 days curing time with CSW raw material was achieved while with CFA, the compressive strength was found to be 41.9 MPa with increasing the curing time up to 28 days.DOI: http://dx.doi.org/10.3126/jncs.v30i0.9334Journal of Nepal Chemical Society Vol. 30, 2012 Page:  45-51 Uploaded date: 12/16/2013    

Effect of Adhesive Thickness on the Impact Toughness of Butt-Joints

2011 ◽  
Vol 230-232 ◽  
pp. 1350-1354 ◽  
Author(s):  
Min You ◽  
Jing Rong Hu ◽  
Xiao Ling Zheng ◽  
Ai Ping He ◽  
Cun Jun Chen
Keyword(s):  
Impact Toughness ◽  
Adhesive Layer ◽  
Curing Temperature ◽  
Curing Time ◽  
Optimum Thickness ◽  
Adhesively Bonded ◽  
Butt Joints ◽  
Notched Specimen ◽  
Adhesive Thickness ◽  
The Impact

The effect of the adhesive thickness on the impact toughness of the adhesively bonded steel joint under impact loading is studied using the experimental method. The results obtained show that the impact toughness increases when the adhesive thickness increased then it decrease as the adhesive thickness increase. When the curing time is set as a constant, the higher the curing temperature is, the lower the impact toughness of the joint. The optimum thickness of the adhesive layer for the specimen of impact toughness test cured at 60 C for 1 h is 0.6 mm and it is 0.4 mm to 0.6 mm for the specimen cured 1 h at temperature of 90 C or higher than it. It is recommended using the notched specimen to decrease the testing deviation.

Effects of Cure State on the Ultrasonic Nonlinear Parameter in Adhesive Joints

2000 ◽  
Author(s):  
Guoli Liu ◽  
Jianmin Qu ◽  
Laurence J. Jacobs
Keyword(s):  
Narrow Band ◽  
Harmonic Signal ◽  
Adhesive Joints ◽  
Nonlinear Parameter ◽  
Curing Temperature ◽  
Curing Time ◽  
Curing Conditions ◽  
Polymer Adhesive ◽  
Ultrasonic Techniques ◽  
Transmitted Signal

Abstract The objective of this paper is to characterize the cure state of polymer adhesive joints using nonlinear ultrasonic techniques. To this end, through transmission tests were carried out on joint samples that had been subjected to various curing conditions. In these tests, a 40-cycle harmonic signal was generated by a 2MHz narrow-band PZT transducer as the incident wave. The wave transmitted through the adhesive joint was received with a 4MHz narrow-band PZT transducer. The magnitude of the second order harmonics in the transmitted signal was measured and the corresponding nonlinear parameter β was calculated. A fairly good correlation was observed between the nonlinear parameter and the cure state. It was found that under-curing (lower curing temperature or short curing time) tends to increase the nonlinear parameter.

Effect of Curing Regimes on Metakaolin Geopolymer Pastes Produced from Geopolymer Powder

2012 ◽  
Vol 626 ◽  
pp. 931-936 ◽  
Author(s):  
Liew Yun Ming ◽  
Kamarudin Hussin ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Mohammed Binhussain ◽  
Luqman Musa ◽  
...  
Keyword(s):  
Room Temperature ◽  
Raw Materials ◽  
Solidification Process ◽  
Curing Temperature ◽  
Alkali Concentration ◽  
Strength Development ◽  
Curing Time ◽  
Curing Conditions ◽  
Metakaolin Geopolymer ◽  
Geopolymer Paste

The properties of metakaolin geopolymer paste are affected by the alkali concentration, the initial raw materials, solidification process, and amount of mixing water as well as the curing conditions. This study aimed to investigate the effect of curing temperature (room temperature, 40°C, 60°C, 80°C and 100°C) and curing time (6h, 12h, 24h, 48h and 72h) on the geopolymer pastes produced from geopolymer powder. The results showed that curing at room temperature was unfeasible. Heat was required for the geopolymerization process, where strength increased as the curing temperature was increased. Moderate elevated curing temperature favored the strength development of geopolymer pastes in comparison with those treated with extreme elevated curing temperature. When geopolymer paste was subjected to extreme elevated curing temperature, shorter curing time should be used to avoid deterioration in strength gain. Similarly, longer curing time was recommended for moderate elevated curing temperature. The microstructure of geopolymer paste cured at moderate curing temperature showed obvious densification of structure. In contrast, the structure formed was weak and less compact at very high elevated curing temperature.

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