Setting time effect

Cement and sodium silicate are mutual catalysts. The combination has been used with other admixtures to give a high strength grout with very short setting times, effective in shutting off fast flowing water. 

In concrete, triethanolamine accelerates set time and increases early set strength (41—43). These ate often formulated as admixtures (44), for later addition to the concrete mixtures. Compared to calcium chloride, another common set accelerator, triethanolamine is less corrosive to steel-reinforcing materials, and gives a concrete that is more resistant to creep under stress (45). Triethanolamine can also neutralize any acid in the concrete and forms a salt with chlorides. Improvement of mechanical properties, whiteness, and more even distribution of iron impurities in the mixture of portland cements, can be effected by addition of 2% triethanolamine (46). Triethanolamine bottoms and alkanolamine soaps can also be used in these type appUcations. Waterproofing or sealing concrete can be accompUshed by using formulations containing triethanolamine (47,48). 

Attempts have been made to improve the mechanical properties of these cements by adding reinforcing fillers (Lawrence Smith, 1973 Brown Combe, 1973 Barton et al, 1975). Lawrence Smith (1973) examined alumina, stainless steel fibre, zinc silicate and zinc phosphate. The most effective filler was found to be alumina powder. When added to zinc oxide powder in a 3 2 ratio, compressive strength was increased by 80 % and tensile strength by 100 % (cements were mixed at a powder/liquid ratio of 2 1). Because of the dilution of the zinc oxide, setting time (at 37 °C) was increased by about 100%. As far as is known, this invention has not been exploited commercially. 

Figure 5.9 The effect of SiOj/AljOj mass ratio on setting time, compressive strength and opacity (Hill Wilson, 1988a).

Figure 6.14 Effect of liquid composition on the setting time and strength of dental silicate cements (Wilson et al, 1970a).

Most of the properties of a dental silicate cement are affected by preparative variables, particularly the powder/liquid ratio (Jorgensen, 1963 Wilson Batchelor, 1967b). Increase in the powder/liquid ratio accelerates set and increases strength and resistance to erosion (Figure 6.21). Temperature and, to a lesser extent, humidity during mixing have some effect, but chiefly they affect setting time. 

Figure 6.21 The effect of powder/liquid ratio on setting time and compressive strength of a dental silicate cement (Wilson Batchelor, 1967b).

Figure 8.4 The effect of Si/Al ratio in the glass on the setting time of glass polyphosphonate and glass polyalkenoate cements (Ellis, 1989).

Table 9.1. Effect of zinc oxide type on setting time of ZOE cements Prosser <6 Wilson, 1982)...

Hydrates quickly, responsible for strength of cement in early stage setting time can be controlled by addition of gypsum Responsible for strength in all stages Responsible for final strength Little effect on physical properties... 

V. E. Akhrimenko, E. A. Aleksandrova, Z. N. Tkachenko, E. A. Dmitriev, F. N. Derevenets, and S. A. Abramov. Effect of aluminum compounds on setting time of cement slurry and strength of set cement. Stroit Neft Gaz Skvazhin Sushe More, 10-11 30-32, October-November 1997. 

A.K. Minocha, Pankaj Kumar, Jaswinder Singh, L.K. Aggarwal, C.L. Verma, Effect of molybdate (II), chromium (III) and (VI) metal ions on the setting time of ordinary Portland cement. Indian J. Env. Prot., 24, 771-774, 2004. 

C. Gervais, and S. K. Ouki, Performance study of cementitious systems containing zeolite and silica fume Effects of 4 metal nitrates on the setting time, strength and leaching characteristics. J. Hazard. Mater., 93,187-200, 2002. 

FIGURE 4.4 Effects of Viscozyme L treatment on gelling properties of psyllium. 4.8,19.2, and 36 represent the final Viscozyme concentrations of 4.8,19.2, and 36 units/g psyllium in the solid-state reaction mixtures, respectively, and Psy represents the original psyllium sample. The setting time was 3 h for all gel samples (redrawn from Yu et ai, 2003). 

In the classical statistical literature, one of the two qualitative factors is referred to as the treatments and the other qualitative factor is referred to as the blocks . Hence, the term block designs . In some studies, one of the qualitative factors might be correlated with time, or might even be the factor time itself by carrying out the complete set of experiments in groups (or blocks ) based on this factor, estimated time effects can be removed and the treatment effects can be revealed... 

Two bioassays are employed to evaluate the effect of samples on terrestrial life forms. For gas samples, the plant stress ethylene test is presently recommended. This test is based on the well-known plant response to environmental stress release of elevated levels of ethylene (under normal conditions plants produce low levels of ethylene). The test is designed to expose plants to various levels of gaseous effluents under controlled conditions. The ethylene released during a set time period is then measured by gas chromatography to determine toxicity of the effluent. For liquid and solid samples, a soil microcosm test is employed. The sample is introduced on the surface of a 5 cm diameter by 5 cm deep plug of soil obtained from a representative ecosystem. Evolution of carbon dioxide, transport of calcium, and dissolved oxygen content of the leachate are the primary quantifying parameters. 

---