Research on the Application of Slipform Concrete of Well Tower in winter

2012 ◽  
Vol 204-208 ◽  
pp. 3703-3706
Author(s):  
Xiang Zong
Keyword(s):  
Mechanical Performance ◽  
Setting Time ◽  
Reducing Agents ◽  
Reducing Agent ◽  
Mix Proportion ◽  
Time Test ◽  
Early Strength ◽  
Blend Ratios

To meet the demand of performance of slipform concrete in a well tower in winter, different blend ratios of early strength water reducing agents were added to the concrete. Compared with reference concrete, their setting time test analyses, workability analyses and tests of mechanical performance and removal of forms were conducted in the laboratory. The results show that concrete with FS-A early strength water reducing agent can greatly improve early strength of concrete and meet the demand of relevant performance of slipform. This research may provide reference for design of mix proportion and construction in similar slipform project.

scholarly journals The Influence of Water Reducing Agents on Early Hydration Property of Ferrite Aluminate Cement Paste

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 731
Author(s):  
Chunlong Huang ◽  
Zirui Cheng ◽  
Jihui Zhao ◽  
Yiren Wang ◽  
Jie Pang
Keyword(s):  
Setting Time ◽  
Critical Role ◽  
Hydration Product ◽  
Reducing Agents ◽  
Reducing Agent ◽  
Hydration Process ◽  
Early Hydration ◽  
Cement Pastes ◽  
Hydration Rate ◽  
Aluminate Cement

The ferrite aluminate cement (FAC) could rapidly lose fluidity or workability due to its excessive hydration rate, and greatly reduce the construction performance. Chemical admixtures are commonly used to provide the workability of cement-based materials. In this study, to ensure required fluidity of FAC, chemically different water reducing agents are incorporated into the FAC pastes. The experiments are performed with aliphatic water reducing agent (AP), polycarboxylic acid water reducing agent (PC) and melamine water reducing agent (MA), respectively. Influence of the water reducing agents on fluidity, setting time, hydration process, hydration product and zeta potential of the fresh cement pastes is investigated. The results show that PC has a better dispersion capacity compared to AP and MA. Besides decreasing water dosage, PC also acts as a retarder, significantly increasing the setting times, delaying the hydration rate and leading to less ettringite in the hydration process of FAC particles. The water reducing agents molecules are adsorbed on the surface of positively charged minerals and hydration products, however, for PC, steric hindrance from the long side chain of PC plays a critical role in dispersing cement particles, whereas AP and MA acting through an electrostatic repulsion force.

Research on Thermodynamical Performance of Concrete with Excessive Fly Ash Added in the Pile Cap of Well Tower

2011 ◽  
Vol 243-249 ◽  
pp. 6087-6092
Author(s):  
Xiang Zong ◽  
Xiang Wang
Keyword(s):  
Fly Ash ◽  
High Performance ◽  
Setting Time ◽  
Hydration Heat ◽  
Favorable Effect ◽  
Mass Concrete ◽  
Mix Proportion ◽  
Pile Cap ◽  
Time Test ◽  
Simulated Test

To meet the demand of high performance of mass concrete in a pile cap of well tower, excessive replacement of fly ash was applied to the mass concrete. Based on the theory of hydration heat of cement, several thermal parameters of mix proportion were analyzed and simulated test analyses and setting time test analyses were conducted in the laboratory. The results and data collected in the project locale both show that applying excessive replacement of fly ash reduces hydration heat of mass concrete in the pile cap of well tower, which extends setting time in mass concrete and avoids the cracks caused by temperature stress. The results achieve favorable effect and provide reference for design and construction of mix proportion in the project of mass concrete.

scholarly journals Effects of Shrinkage Reducing Agent and Expanded Cement on UHPC Fluidity, Mechanical Properties, and Shrinkage Performance

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Tingyu Wang ◽  
Jianqing Gong ◽  
Bo Chen ◽  
Xiao Gong ◽  
Hongkui Luo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Setting Time ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Reducing Agent ◽  
Strength Development ◽  
Study Results ◽  
Binder Ratio ◽  
Early Strength ◽  
Shrinkage Reducing Agent

The purpose of this study was to evaluate the effects of a shrinkage reducing agent (SRA) and Portland expanded cement (PEC) on the fluidity, mechanical properties, and shrinkage performance of ultrahigh-performance concrete (UHPC). The results indicated that the fluidity of the fresh UHPC mortar initially decreased and then increases along as a function of SRA dosage. When the dosage of SRA was 1%, the UHPC mortar fluidity was at its minimum. For dosages exceeding 1%, the additional water-binder ratio of the mortar increased, which in turn increased the UHPC fluidity. That is, the SRA delayed the cement hydration and increased the setting time, which is not conducive for early strength development of UHPC. As the SRA dosage was increased (i.e., 0%–2%), the autogenous shrinkage of UHPC decreased significantly such that even a small dosage of about 0.5% SRA was able to effectively reduce drying shrinkage. From the study results, it was also observed that PEC accelerated the loss of fluidity in the fresh UHPC and concurrently promoted the early strength development of UHPC. At 75% PEC content, the strength enhancement effects tended to be stable. This means that although the addition of PEC will potentially increase the autogenous shrinkage of UHPC, it has the positive effect of inhibiting drying shrinkage provided that the PEC dosage is controlled within the 25%–50% range. Furthermore, morphological analyses using a scanning electron microscope (SEM) indicated that an increase in the SRA dosage loosens the UHPC microstructure, with the formation of the hydration products remaining incomplete, thus ultimately causing the UHPC strength to decrease. Overall, the study findings indicated that 2% SRA and 25%–50% PEC can effectively reduce the shrinkage of UHPC and are, therefore, recommended as the optimum dosages.

scholarly journals Effect of Calcium Nitrate on the Properties of Portland–Limestone Cement-Based Concrete Cured at Low Temperature

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1611
Author(s):  
Gintautas Skripkiūnas ◽  
Asta Kičaitė ◽  
Harald Justnes ◽  
Ina Pundienė
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Setting Time ◽  
Calcium Nitrate ◽  
Curing Temperature ◽  
Hardened Concrete ◽  
Cement Pastes ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Early Strength

The effect of calcium nitrate (CN) dosages from 0 to 3% (of cement mass) on the properties of fresh cement paste rheology and hardening processes and on the strength of hardened concrete with two types of limestone-blended composite cements (CEM II A-LL 42.5 R and 42.5 N) at different initial (two-day) curing temperatures (−10 °C to +20 °C) is presented. The rheology results showed that a CN dosage up to 1.5% works as a plasticizing admixture, while higher amounts demonstrate the effect of increasing viscosity. At higher CN content, the viscosity growth in normal early strength (N type) cement pastes is much slower than in high early strength (R type) cement pastes. For both cement-type pastes, shortening the initial and final setting times is more effective when using 3% at +5 °C and 0 °C. At these temperatures, the use of 3% CN reduces the initial setting time for high early strength paste by 7.4 and 5.4 times and for normal early strength cement paste by 3.5 and 3.4 times when compared to a CN-free cement paste. The most efficient use of CN is achieved at −5 °C for compressive strength enlargement; a 1% CN dosage ensures the compressive strength of samples at a −5 °C initial curing temperature, with high early strength cement exceeding 3.5 MPa but being less than the required 3.5 MPa in samples with normal early strength cement.

C80 Early Strength Micro Expansion of Steel Tube Reinforced Concrete Research

2015 ◽  
Vol 1119 ◽  
pp. 752-755
Author(s):  
Chang Zheng Sun ◽  
Zheng Wang
Keyword(s):  
High Performance ◽  
Raw Materials ◽  
Influence Factors ◽  
High Strength ◽  
Steel Tube ◽  
Strength Analysis ◽  
Self Compacting Concrete ◽  
Mix Proportion ◽  
Early Strength ◽  
Working Performance

Optimization of mix proportion parameter ，Using ordinary raw materials makes a C80 high performance self-compacting concrete;By joining a homemade perceptual expansion agent, significantly improve the early strength of concrete and effective to solve the high strength of self-compacting concrete caused by gelled material consumption big contraction;Further study on the working performance of high-strength self-compacting concrete, age strength, analysis the influence factors of concrete are discussed.

Several Common Retarders on Performance of Ultra-Early-Strength Grouting Material

2013 ◽  
Vol 477-478 ◽  
pp. 931-935
Author(s):  
Chang Zheng Sun ◽  
Xiao Ping Zhang ◽  
Hai Nan Zhao ◽  
Qiang Gao
Keyword(s):  
Mechanical Strength ◽  
Setting Time ◽  
Strength Properties ◽  
Preliminary Screening ◽  
Final Setting Time ◽  
Grouting Material ◽  
Early Strength

To explore retarders on performance of ultra-early strength grouting material, Retarder, which are commonly used in the market after a preliminary screening, are further tested and analyzed for initial fluidity, setting time and mechanical strength properties of super early strength grouting material. The results show that: When borax content is 0.4%, the initial fluidity, final setting time, workability, mechanical strength are the best.

scholarly journals Effect of TiO2 Nanoparticles on Physical and Mechanical Properties of Cement at Low Temperatures

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Li Wang ◽  
Hongliang Zhang ◽  
Yang Gao
Keyword(s):  
Mechanical Properties ◽  
Low Temperatures ◽  
Cement Hydration ◽  
Setting Time ◽  
Physical And Mechanical Properties ◽  
Xrd Analysis ◽  
Cementitious Materials ◽  
Strength Test ◽  
Hydration Degree ◽  
Time Test

Low temperature negatively affects the engineering performance of cementitious materials and hinders the construction productivity. Previous studies have already demonstrated that TiO2 nanoparticles can accelerate cement hydration and enhance the strength development of cementitious materials at room temperature. However, the performance of cementitious materials containing TiO2 nanoparticles at low temperatures is still unknown. In this study, specimens were prepared through the replacement of cement with 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, and 5 wt.% TiO2 nanoparticles and cured under temperatures of 0°C, 5°C, 10°C, and 20°C for specific ages. Physical and mechanical properties of the specimens were evaluated through the setting time test, compressive strength test, flexural strength test, hydration degree test, mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) analysis, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) in order to examine the performance of cementitious materials with and without TiO2 nanoparticles at various curing temperatures. It was found that low temperature delayed the process of cement hydration while TiO2 nanoparticles had a positive effect on accelerating the cement hydration and reducing the setting time in terms of the results of the setting time test, hydration degree test, and strength test, and the specimen with the addition of 2 wt.% TiO2 nanoparticles showed the superior performance. Refined pore structure in the MIP tests, more mass loss of CH in TGA, intense peak appearance associated with the hydration products in XRD analysis, and denser microstructure in SEM demonstrated that the specimen with 2 wt.% TiO2 nanoparticles exhibited preferable physical and mechanical properties compared with that without TiO2 nanoparticles under various curing temperatures.

scholarly journals Synthesis of Gold Nanoparticles Using p-Aminobenzoic Acid and p-Aminosalicylic Acid as Reducing Agent

2019 ◽  
Vol 19 (1) ◽  
pp. 68
Author(s):  
Abdul Aji ◽  
Eko Sri Kunarti ◽  
Sri Juari Santosa
Keyword(s):  
Gold Nanoparticles ◽  
Optimum Condition ◽  
Reducing Agents ◽  
Reducing Agent ◽  
Hydroxyl Group ◽  
Synthesis Process ◽  
Aminobenzoic Acid ◽  
Aminosalicylic Acid ◽  
Amino Groups ◽  
Transmission Electron

Synthesis of gold nanoparticles (AuNPs) by reduction of HAuCl4 with p-aminobenzoic acid and p-aminosalicylic acid as a reducing agent was investigated. This work was conducted in order to determine the optimum condition of AuNPs synthesis and examine the effect of the hydroxyl group in p-aminosalicylic acid towards the size, shape, and stability of the synthesized gold nanoparticles (AuNPs). The optimum condition of the gold nanoparticles synthesis was determined by UV/Vis spectrophotometer, the shape and size of gold nanoparticles were measured by Transmission Electron Microscope (TEM). The synthesis process was started by reacting HAuCl4 and the reducing agents in an aqueous solution at 86 ºC. The initial gold concentration, reducing agents concentration and pH were varied in order to obtain the optimum condition. In the optimum condition, the results showed that p-aminosalicylic acid containing both hydroxyl and amino groups performed higher reduction ability compared to p-aminobenzoic acid that only containing an amino group. Reducing agents which have a hydroxyl group (p-aminosalicylic acid) could produce AuNPs with a smaller concentration of HAuCl4 than p-aminobenzoic acid. Gold nanoparticles that were synthesized with p-aminosalicylic acid were more stable and had a smaller particle size compared to its counterpart that is synthesized with p-aminobenzoic acid.

Sign in / Sign up

Export Citation Format

Share Document