SBR-modified

Table 6.12 Effect of particle size on the properties of SBR-modified concrete...

Table 6.13 Effect of wet and dry curing of SBR-modified mortar E (Kuhimann)...

Setting time of an SBR modified cement composition is delayed. However, in actual use, such mortar toppings may often be walked on in 12 to 18 hours, and may take light rubber tire traffic in 48 hours. These times will vary, depending upon the temperature, humidity and the percentage of latex in the mix. Table 2 shows the setting time for SBR latex/cement compositions. ... 

Therefore, the required mix proportions by weight of the SBR-modified concrete for trial mixing in this example would be as follows ... 

Table 3.9 AQ Guidelines for Mix Proportions of SBR-Modified ConCTete Overlays. ( 1992, American Concrete Institute, Reprintedwith permission.)...

Figure 4.2 Effects of unit water content (water-cement ratio) and polymer-cement ratio on slump of SBR-modified concrete.

Figure 4.4 Relation between polymer-cement ratio and water-cement ratio of SBR-modified concretes.

Ohamal ll l studied the effect of monomer ratio in EVA, SBR, and poly (styrene-butyl acrylate, SAE) latexes on the strengths of latex-modified mortars (Fig. 4.10). The monomer ratio affects the strengths of the latex-modified mortars to the same extent as the polymer-cement ratio. The maximum strengths of EVA- and poly(styrene-butyl acrylate)-modified mortars are obtained at a bound ethylene content of 13% and a bound styrene content of 55% respectively. The strengths of SBR-modified mortar increase with a rise in the bound styrene content. These results are similar to those obtained by Cherkinskii, et al.f i The tensile strength of the dry films made from SBR latexes increases sharply when the bound styrene content is raised, and there is a positive correlation between the strength of the films and the flexural strength of SBR-modified mortars with polymer-cement ratios above 10% as shown in Fig. 4.11.li l... 

The effect of plasticizer (i.e., dibutyl phthalate) content in PVAC latexes on the strengths of PVAC-modified mortars is represented in Fig. 4.12.i i Like SBR-modified mortars, the strengths are governed by the nature of polyvinyl acetate (with variation of the plasticizer content), and is reduced with an increase in the plasticizer content. 

Figure 4.11 Relationship between tensile strength of SBR latex films and flexural strength of SBR-modified mortars.

Table 4.3 Effect of Latex Particle Size on Chloride Ion Permeability of SBR-Modified Mortars with a Polymer-Cement Ratio of 15% by ASTM C 1202.

Figures 4.31 and 4.321 1 represent the tensile stress-strain curves and the polymer-cement ratio-elon tion (i.e., maximum tensile strain at failure) relationships of SBR-modified concretes respectively. As seen in these figures, as the polymer-cement ratio is raised, die modulus of elasticity in tension decreases, and the elongation increases and is 2 to 3 times greater than that of unmodified concrete. This is explained by considering that the polymer films formed in the concrete may effectively halt propagating microcracks through their high tensile strength and elongation.

The modulus of elasticity in compression and Poisson s ratio of latex-modified concretes are listed in Table 4.5. [ 1 The modulus of elasticity generally tends to decrease with a rise in the polymer-cement ratio. The Poisson s ratio of PAE- and SBR-modified concretes is nearly equal to that of unmodified concrete regardless of the polymer-cement ratio, but that of PVAC-modified concretes increases with rising polymer-cement ratio. 

WATER IMMERSION PERIOD, hours SBR-MODIFIED MORTAR... 

Figure 4.45 Effect of polymer-cement ratio on water vapor transmission of SBR-modified mortars.

Ohamat l found a nearly ten-fold increase in adhesion to ordinary cement mortar of SBR-modified mortar with a polymer-cement ratio of 20%, compared to unmodified mortar. In this case, the monomer ratio of the copolymer was important, and the high adhesion was attained at a bound styrene content of 70%. 

Ohama, Y., Miyake, T., and Nishimura, M., Properties of SBR-Modified Concrete (in Japanese), Nihon-Kenchiku-Gakkai Kanto-Shibu Kenkyu-Hokokushu, pp. 289-292 (July 1980)... 

Similar to latex-modified systems, the properties of redispersible polymer powder-modified systems are improved in comparison with ordinary cement mortar and concrete, and these depend on the nature of polymer and polymer-cement ratio. Figs. 5.3 to 5.5i l represent the strengths, adhesion to cement mortar, water resistance, and water absorption of the redispersible polymer powder-modified mortars. The properties are improved with an increase in the polymer-cement ratio. This tendency is very similar to that of the latex-modified systems. In general, the redispersible polymer powder-modified mortars are inferior to SBR-modified mortar (control) in certain properties. VAA eoVa powder-modified mortars show tetter properties than EVA powder-modified mortars as seen in Fig. 5.5. The film formation characteristics of recent redispersible polymer powders for cement modifiers are improved, and continuous polymer films can be found in the redispersible polymer powder-modified systems as seen in Fig. 5.6. This contributes greatly to improvements in their properties. 

SFRPCM, Steel fiber reinforced SBR-modified mortar CFRC, Carbon fiber reinforced cement... 

Table 9.2 Bridge Deck Overlay Projects Using SBR-Modified Concretes inU.S.

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