【正文】 easing day by day. Polymers are either incorporated in a cement–aggregate mix or used as a single binder. The posites made by using polymer along with cement and aggregates are called polymermodified mortars (PMM) or polymermodified concrete (PMC), while posites made with polymer and aggre gates are called polymer mortar (PM) or polymer concrete (PC). Since polymers are costly the former type of application is preferred over the latter in most of the situations. The incorporation of polymers greatly improves strength, adhesion, resilience, impermeability, chemical resistance and durability properties of mortars and concrete [1–3]. These properties make PMM a suitable material for making various structural and nonstructural precast products, repair of structural members, waterproofing, anticorrosive and decorative finishes, overlay of pavements, bridges and industrial floors [1,4]. A number of thermoplastic or thermosetting polymers are used in modifying mortars and concrete. These are used in various forms like: liquid resins, latexes, redispersible powders and watersoluble homopolymers or copolymers [5]. The choice of the polymer depends upon the intended use, and requirement of performances like strength, durability and chemical , the polymer systems can also be modified by use of additives like surfactants, stabilisers, antifoaming agents and colouring pigments [1]. Polymer latexes are dispersion of polymer particles of size – lm in water [5]. For making PMM, most of the researchers use latexes of a single or binations of polymers like polyvinyl acetate, copolymers of vinyl acetate–ethylene, styrene–butadiene, styrene–acrylic, and acrylic [1,5,6]. Latex can also be made by using epoxy resin, which es under the non reemulsifiable category. The non reemulsifiable latexes are expected to have greater resistant to chemical, alkaline and humid environment. However, very little information is available on the use of epoxy emulsion in making PMM. In view of this, an experimental study was conducted to develop PMM based on epoxy emulsion. The outes of this study are reported in this paper. The properties of epoxymodified mortar are pared with those of unmodified cement mortar and acrylicmodified mortar.2. Materials and methodsEpoxy emulsion was prepared by emulsifying epoxy resin, based on diglycidyl ether of bisphenolA, and aminoamide based hardener in water by using a nonionic surfactant. Additives like defoaming, wetting and anticatering agents, and fillers were also used. For both, epoxy emulsion and acrylic emulsion, similar dosages of additives were used. The prepared epoxy emulsion had density of – g/cm3, epoxide equivalent value of 200–300 g eqand total solids of 60 177。 2%。 while acrylic emulsion had density of – g/cm3 and total solids 38 177。 2%.Ordinary Portland cement, grade 43, and quartz sand No. 10 were used for making the PMM test specimens. Properties of the cement and sieve analysis of the sand used in this study are reported in Tables 1 and 2, study the effect of polymer–cement ratio on various properties specimens were prepared by varying the polymer–cement ratio from 0% to 30% by mass of cement. A cement–sand ratio of 1:3 by mass was kept constant for all the specimens. For all the mixes the water–cement ratio (w/c) was adjusted to maintain a constant flow between 110 and 120 mm. Five specimens of 40 mm 40 mm 160 mm size were prepared for threepoint flexure test. After flexural test the specimens were cut from the ends, ., from the uncracked portion of the specimens to obtain cubes of size 40 mm 40 mm 40 mm for determining pressive strength and water absorption. For carbonation and chloride ion penetration tests three prisms of 40 mm 40 mm 80 mm size for each test were moulded. After moulding, the specimens were allowed to cure in the mould for first 24 h. During this period the moulds were covered with wet cloth and polyethylene sheet. The specimens were then kept in the laboratory conditions, 20 177。 2 C and 50 177。 5% relative humidity (RH) for the next 27 d. It is known that the water curing degrades the mechanical strength of polymer modified cementitious mortars [2,7]. Hence, water curing was eliminated for PMM specimens, while one set of control specimens, ., specimens without polymer was water cured and another was air cured. Water absorption, flexural and pressive strength tests were carried out according to JIS A 1171–2000 and JIS A 6203–2000 [8,9]. In the carbonation test, the finished and bottom surfaces and two ends of the cured mortar samples were coated with epoxy resin based paint. The specimens were then placed in a test chamber for 14 d at a CO2 gas concentration of 5%, temperature 30 C and 60% RH. The carbonated samples were then split into two pieces by using a splittingtensile device. Immediately after splitting a 2% alcoholic solution of phenolphthalein was sprayed on the newly exposed inner surfaces of the specimens. The depth of each crosssection without colour change was measured as carbonation the chlorideion penetration test, the cured samples were immersed in a % sodium chloride solution at 25 C for 7 d. The samples were split after the test and the split crosssections were sprayed with % sodium fluorescein and N silver nitrate solution. The depth of the rim of each crosssection changed to white was measured as chloride ion penetration depth.3. Results and discussionThe effect of polymer addition on water–cement ratio required to maintain the desired flow (110–120 mm) is shown in Fig. 1. The required quantity of water decreases with the addition of both polymers. However, the decrease is relatively more in case of acrylic emulsion. A reduction in water requirement was expected not only due to the presence of surfactants in the polymers but also due to the lower surface tension of polymer molecules, which facilitates better flow of the mix at the same water content. The result