Contents POLYMER CONCRETES

Polymer concretes based on carbamide resins have a low toxicity and are favorable in manufacturing. However, the content of the polymer matrix in these PCs is high (up to 30%) and their physical and mechanical properties are low in comparison to other types of polymer concretes. 

C, P, W, S, G Weight of cement, polymer, water, sand, and gravel per unit volume of latex-modified concrete, respectively (kg/m ), i.e., unit cement content, unit polymer content, imit water content, unit sand content, and unit gravel content Polymer-cement ratio (by weight)... 

Polymer concrete production uses equipment and methods that are being used for producing Portland cement concrete. In the design of polymer concrete mixes, the main objective is to obtain a suitable particle size distribution of the aggregate so that a good workability will be attained with a minimum amount of monomer or resin [9]. Aggregates should be dried to at least 3% moisture [11] but moisture contents less than 1% are preferred as moisture reduces the bond between the binder and the aggregate [14]. 

A preaccelerated, low styrene content, orthophthalic resin for polymer concrete and marble. ... 

The application of fillers greatly improves not only the workability of the fresh polymer concrete mix, which boasts superior lubricating properties, but also its plasticity and cohesive ability to ensure a good bond between the polymer matrix and inorganic aggregate. The filler content varied from 0 to 30 wt% of the polymer concrete. 

The author is most grateful to Professor A.M.Brandt for many valuable remarks with regard to the content of this paper. Preparation of the polymer concrete specimens by Professor L.Czarnecki, Warsaw Technical University, is gratefully acknowledged. 

The specific electrical resistance of concrete can be measured by the method described in Section 3.5. Its value depends on the water/cement value, the type of cement (blast furnace, portland cement), the cement content, additives (flue ash), additional materials (polymers), the moisture content, salt content (chloride), the temperature and the age of the concrete. Comparisons are only meaningful for the... 

Surfactants enable the polymer particles to disperse effectively without coagulation in the mortar and concrete. Thus, mechanical and chemical stabilities of latexes are improved with an increase in the content of the surfactants selected as stabilizers. An excess of surfactant, however, may have an adverse effect on the strength because of the reduced latex film strength, the delayed cement hydration and excess air entrainment. Consequently, the latexes used as cement modifiers should have an optimum surfactant content (from 5 to 30% of the weight of total solids) to provide adequate strength. Suitable antifoamers are usually added to the latexes to prevent excess air entrainment increased dosages causes a drastic reduction in the air content and a concurrent increase in compressive strength [87, 92-94]. 

Such effects increase with an increase in the polymer content or the polymer-cement ratio (the weight ratio of total solids in a polymer latex to the amount of cement in a latex-modified mortar or concrete mixture). However, at levels exceeding 20% by weight of the cement in the mixture, excessive air entrainment and discontinuities form in the monolithic network structure, resulting in a reduction of compressive strength and modulus [87, 94, 95]. 

The presence of the cement hydrate/polymer comatrix in LMM and LMC confers superior properties, such as high tensile and flexural strengths, excellent adhesion, high waterproofhess, high abrasion resistance and good chemical resistance, when compared to ordinary cement mortar and concrete. The degree of these improvements however depends on polymer type, polymer-cement ratio, water-cement ratio, air content and curing conditions. Some of the properties affected by these factors are discussed below [87, 88, 93-95]. 

In general, at low latex dosage levels, the creep strain and creep coefficient of latex modified concrete and mortar are considerably smaller than those of ordinary cement cement, mortar and concrete [94, 98]. The low creep is probably due to the low polymer content which may not affect the elasticity, but increases the strength by improving the binding capacity of the matrix as well as providing better hydration through water retention in the mortar and concrete. The coefficient of thermal expansion at about 9-10 x 10 is very similar to that of concrete, which is 10 x 10 6 [87, 94, 99]. 

The large pores (ranging from 0.01 pm to 0.1 pm) are sealed by the continuous polymer film formed in the comatrix of LMM and LMC. Consequently, they show reduced water absorption, water permeability and water vapor transmission over ordinary cement mortar and concrete and this effect increases with an increase in polymer content and polymer-cement ratio (Fig. 6.15). The improved water permeability also improves the resistance to chloride ion entry and hence corrosion mitigation [87]. 

The reduction in porosity, decreased water content, and air entrainment that results when latexes are used in mortar and concrete mixes make them much more resistant to freezing and thawing conditions than conventional mortar and concrete. Figure 6.17 presents the freeze-thaw durability in water (-18 to 4°C) of combined water-and dry-cured SBR-, PAE- and EVA-modified mortars [98], The frost resistance of mortars made with these latexes is markedly improved even at polymer-cement ratios of 5%. However, an increase in the polymer-cement ratio does not necessarily produce further improvement in freeze-thaw resistance. EMM and EMC, when exposed to outdoor conditions involving freeze-thaw, UV radiation and carbonation show better weatherability when compared with conventional mortar and concrete. 

PET is useful polymer used for fiber, film, and plastic containers such as carbonated beverage bottles. Recently, the recycling of polymers such as PET after use is attracting the attention of many researchers aware of environmental problems and wishing to find ways to save earth resources. Previous studies showed that unsaturated polyester resins can be economically prepared from recycled PET and the resins may be useful for resin concretes (1 4). However, there is little information on the molecular features of the UPE resins. Thus, we synthesized various UPE resins from PET. Especially, the PET content, chain flexibility and degree of unsaturation of the resins were systematically varied and the effects of those variables on the mechanical properties of the cured resins and polymer mortars made therefrom were studied. 

Preparation and Test Methods In the preparation of cement mortar or concrete, content of ash was varied with or without polymer latex. In order to compare the properties of the cement mortar or concrete at a same flow property, flow values were maintained 120 5 mm. Mix formulations studied are given in Table 5, Table 6, and Table 7. Test methods of the specimens prepared are given in Table 8. 

Fig. 4. W/C ratios depending on ash content of cement concrete with and without polymer latex.

In Fig. 4, water/cement ratios of the cement concrete for interlocking block into which ashes were incorporated with and without polymer latex are shown. It is observed that water/cement ratios of the cement concrete increased as the ash contents were increased. It is worthwhile to note that the increase of water/cement ratios for cement concrete with polymer latex was less than that for cement mortar without polymer latex and almost constant. 

In Fig. 5, moisture absorptions (%) of the cement concrete for interlocking block into which ashes were incorporated with and without polymer latex are shown. In case of cement concrete without polymer latex, moisture absorption increased as the ash content is increased. The cement concrete with polymer latex showed less moisture absorption compared with the cement mortar without polymer latex. Furthermore, moisture absorption decreased as the ash content was increased in the cement concrete with polymer latex. It is believed that the decreased moisture absorption of the cement concrete with polymer latex are due to film formation of the latex polymer in the capillary and voids of the cured cement concrete. According to KS F 4419, moisture absorption of the interlocking block should be less than 7%. It seems that addition of polymer latex at least 5% of cement to the cement concrete with ashes is necessary to meet the KS F 4419. 

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