Use of nano-silica to reduce setting time and increase early strength of concretes with high volumes of fly ash or slag

2012 ◽  
Vol 29 ◽  
pp. 573-580 ◽  
Author(s):  
Min-Hong Zhang ◽  
Jahidul Islam
Keyword(s):  
Fly Ash ◽  
Setting Time ◽  
Nano Silica ◽  
Early Strength

Research on Mining Water-Rich Fly-Ash-Based Filling Material

2014 ◽  
Vol 988 ◽  
pp. 201-206 ◽  
Author(s):  
Wei Xin Chen ◽  
Feng Yi Li ◽  
Xian Hua Guan ◽  
Lei Chen ◽  
Wen Bo Nie
Keyword(s):  
Fly Ash ◽  
Industrial Waste ◽  
Setting Time ◽  
Physical And Mechanical Properties ◽  
Filling Material ◽  
Metal Mine ◽  
Early Strength ◽  
The Cost ◽  
Cementing Material ◽  
Early Activity

It had decades of history that cementing material was used for filling in coal mine or metal mine goaf, which was a common filling material in recently filling mining. Paste and high water material have excellent performance, but the price was too high, which restricted the development of cemented filling technology severely. Later, fly ash and other industrial waste were mixed into the cementing material in order to reduce the cost, but because of which early activity was low, the early strength was reduced by mixing too much fly ash and other industrial waste, the setting time was extended, which affected the filling effect seriously. Therefore, it becomes a key problem that how to excite the early activity of fly ash. It was a breakthrough to select the appropriate activator and activation method, because of the difference mechanism of action and effects for different activators of fly ash, the complexity composition of filling material mixed with large number of fly ash, and the early and late physical and mechanical properties [1,2].Four salts are used for activators in this paper, which are mixed with fly ash and water, and a display method was selected to maximum activate the activity of fly ash, increase the early strength of the material, and reduce the cost of the material.

scholarly journals Development of Coal Mine Filling Paste with Certain Early Strength and Its Flow Characteristics

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Feng Zhang ◽  
Jinxiao Liu ◽  
Haiming Ni ◽  
Wenxin Li ◽  
Yongle Liu
Keyword(s):  
Fly Ash ◽  
Coal Mine ◽  
Setting Time ◽  
Flow Characteristics ◽  
Coal Gangue ◽  
Practical Significance ◽  
Range Analysis ◽  
Factors Affecting ◽  
Early Strength ◽  
Backfill Strength

In coal mine paste filling technology, geomaterials like coal gangue and fly ash are used as the main component, and cement is applied as the cementing material. In the mining production, mining-and-filling is a cyclic work, where the filling immediately after mining and mining immediately after filling. Long solidification time after filling will affect mining; consequently, the paste should have early strength. In addition, the prepared paste will be conveyed to goaf through the pipeline. The paste flow characteristics will change to some extent in the conveying process, and there is uncertainty about whether the paste can meet the requirements of pumpability and strength. Therefore, the influence of pipeline conveying on flow characteristics of paste before filling the goaf should be taken into consideration. Based on the above two points, this paper studies the paste strength, backfill strength, and pumpability parameters in coal mine paste filling and determines the early and later strength of coal mine paste, as well as the pumpability parameters such as slump degree, segregation degree, setting time, and paste gradation. With the determined mass proportion of coal gangue, fly ash, and silicate cement, the orthogonal test was carried out with three factors including gypsum content, the content of early strength agent (Na2SO4), and the mass concentration, and at three levels. The factors affecting paste flow characteristics were determined by range analysis, and the factors affecting the paste’s early strength were determined by the XRD test and SEM test on its microstructure. With paste proportioning and pipeline conveying simulation system, taking slump, segregation degree, backfill strength, and other parameters as indicators, we obtain the influence law of pipeline conveying on the flow characteristics of paste. The research has great theoretical and practical significance for developing coal paste with early strength and its flow characteristics.

Influence of Alkaline Activator on the Strength of Fly Ash-Cement Gel Sand Material

2014 ◽  
Vol 937 ◽  
pp. 472-475 ◽  
Author(s):  
Hai Yan Huang ◽  
Ai Min Gong ◽  
Kun Yuan
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Test Specimen ◽  
Rupture Strength ◽  
Setting Time ◽  
Alkaline Activator ◽  
Early Strength ◽  
Sand Material ◽  
Early Activity ◽  
Better Than

Influence of different kinds and mixing amount of the alkaline activators on the strength of fly ash-cement gel sand materials is discussed through experiment wit 29 group test specimen. The rupture strength and the compressive strength with the age of 3 and 28 days of test blocks mixed with NaOH or CaO are compared each other. The early activity of fly ash can be activated by mixing the alkaline activator. The early activity of fly ash can be activated by mixing with the alkaline activators. The setting time of fly ash-cement binders becomes better. And the early strength can be improved. The activated effect of fly ash-cement binders by different type of the alkaline activators is affected by the age of test blocks. The activated effect mixed with CaO is better than the effect mixed with NaOH.

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.

Experimental Study on Mechanical Property of Concrete Based on Seawater and Sea Sand

2013 ◽  
Vol 641-642 ◽  
pp. 574-577 ◽  
Author(s):  
Ying Tao Li ◽  
Ling Zhou ◽  
Mao Jiang ◽  
Yu Zhang ◽  
Jun Shao
Keyword(s):  
Mechanical Property ◽  
Experimental Study ◽  
Fly Ash ◽  
Raw Materials ◽  
Growth Trend ◽  
Sea Sand ◽  
Significant Strength ◽  
Dry Conditions ◽  
Early Strength ◽  
Better Than

In this paper, the mechanical property experiments of concrete based on the seawater and sea sand have been carried in different raw materials preparation and different conservation environments. The results show that the early strength and late strength of concrete based on seawater and sea sand are better than concrete based on freshwater and sand. There is no significant strength decreased for concrete based on seawater and sea sand under accelerated alternating wet and dry conditions. For concrete based on seawater and sea sand mixed with admixture, the downward trend of late strength is significantly delayed, the late strength of concrete based on the seawater and sea sand mixed with slag gets the most obvious growth trend, while the late strength of seawater and sea sand concrete mixed with fly ash gets the largest increment.

The Effect on Cement Mortar and Concrete by Admixture of Spray Drying Absorption Products

1989 ◽  
Vol 178 ◽  
Author(s):  
Kirsten G. Jeppesen
Keyword(s):  
Grain Size ◽  
Fly Ash ◽  
Cement Mortar ◽  
Setting Time ◽  
Mineralogical Composition ◽  
Cement Clinker ◽  
Strength Development ◽  
Fall Meeting ◽  
Freeze Thaw ◽  
Spray Dried

AbstractSpray dried absorption products (SDA) having special characteristics are used as substitutes for cement in the preparation of mortars; the qualities of the resulting mixed mortars are described. Conditions are described for mortar mixes, data for which were presented at the MRS Fall Meeting 1987.The influence of the composition of the SDA on water requirement and setting time has been studied. A full scale project involving 3 precast, reinforced concrete front-elements containing 20 and 30 wt.% SDA is described. Strength development, mineralogical composition and corrosion were monitored for two years.A non-standard freeze-thaw experiment was performed which compares mortars containing SDA and fly ash (FA) and also shows the effect of superplasticizer.The possibility of improving the SDA by grinding has been tested and a limited improvement has been found. The strength of the mixed mortars seems slightly influenced by the grain size of SDAGypsum (CaSO4·2H2O), synthetic calcium-sulphite (CaSO3·½H2O) and 2 SDAs have been used as retarders for cement clinker. Mortar test prisms have been cast and comparative strengths after curing for 3 years are reported

Early strength behaviour of fly ash concretes

1994 ◽  
Vol 24 (2) ◽  
pp. 277-284 ◽  
Author(s):  
K. Ganesh Babu ◽  
G. Siva Nageswara Rao
Keyword(s):  
Fly Ash ◽  
Early Strength
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