Flexural strength accelerators

Taking into account the properties of fly ash cements, as well as the acceleration of pozzolanic reaction at higher temperature, maity authors recommend to apply this cement in the production heat treated precast elements,. For example Dalziel [138] found that the thermal treatment of cement with 20 % of fly ash at temperatme of 65 and 85 °C result in higher strength of mortar already after three days and this trend is continued during all smdied period. The flexural strength increase was particularly evident (Fig. 7.22). This behaviour was proved by the other authors [113]. 

Panthapulakkal et at [65] studied the effects of accelerated LTV radiation exposure on the flexural properties of rice husk/HDPE composites for 745 hours. Although the surface of the composites showed considerable discoloration, their flexural strength and modulus were not significantly different from those of the xmexposed composite samples. It was suggested that the exposure time was not sufficient to cause any significant deterioration in flexural properties. On the other hand, water immersion for 1600 hours had a significant effect of flexural properties, particularly the flexural stiffness. 

Figure 4.681 1 illusteates the wcatberability of five types of latex-modified mortars with a polymer-cement ratio of 15%, assessed by measuring a flexural strength retention after 336 accelerated weafliering (4-hour-60°C-ultraviolct lightplus 4-hour-50 C-100% R.H. exposure) cycles. 

The effects of curing time and some other formulation variables are summarized in Table 2, along with initial flexural strength, and tensile strength and modulus before and after 1,000 hours weatherometer accelerated aging. It is readily apparent... 

Table 5.1 Retention of flexural strength after accelerated ageing of commercial fibre cements composites made of different types of fibres (after Baum and Bentur [33])...

Figure 8.24 Flexural strength retention of AR-GRC in UK weather ( ) compared with predictions from accelerated ageing tests at S0°C(O), 60°C(+) and 80 C(x) (after Aindow et o/. [78]).

Figure 8.41 Effect of accelerated ageing on the flexural strength (a) and ultimate strain, (b) of GRC composites (E and AR glass) with Portland cement or CGC...

The data available on the effect of accelerators on the flexural and tensile strengths and the modulus of elasticity are limited [22, 30, 31] and are relevant only to calcium chloride and triethanolamine. The data generally point to either no effect or a slight reduction in all three properties. Also, in view of the increase in compressive strength, it is reasonable to assume that for a given compressive strength, the presence of calcium chloride or triethanolamine will reduce the flexural and tensile strengths and the modulus of elasticity. 

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