Unmodified Mortar Research Articles

Initial Surface Absorption of Pozzolan and Polymer Modified Mortar

This study involves the investigation of water absoption of mortar modified with combinations of polymer and pozzolan by using initial surface water absorption test (ISAT). Since surface of mortar or concrete serves as medium that will be most easily penetrated by moisture that can cause corrosion of reinforcement bars that leads to durability problem, it is imperative to make it durable.Polymer additive and pozzolanic cement replacement used in this study was Styrene Butadiene Rubber (SBR) and Fly Ash (FA) respectively. Mixes were prepared with two water to cement ratios (w/c) of 0.3 and 0.4 with different combinations of 5%, 7% & 10% SBR additive and 10%, 20% and 30% FA cement replacement. Results showed that modified mortar with combination of higher percentages of polymer additive and lower percentages of pozzolonic cement replacement have the lowest initial surface absorption rate compare to unmodified mortar. It can be concluded based on this study that high percentage of polymer addition and low percentage of pozzolanic cement replacement in mortar can enhance its resistance to water absorption.

Preparation and Properties of Cement Mortar Modified by VAE Latex

The effect of VAE latex modification on the physical properties of cement mortar is investigated. The porosity problem in cement mortar modified by vinyl acetate ester-ethylene (VAE) copolymer emulsion was successfully resolved by reasonable defoaming technique. It is shown that the bond strength and water resistance properties of modified cement mortar are better than unmodified cement mortar. When polymer-cement ratios ranged from 0 to 0.25, the bond strength and anti-permeability increased first and then decreased. The best value appeared at 0.1(polymer-cement ratio). SEM shows that the modified sample has compacted structure, polymeric films wrap the cement body and fill in the gap between cement and sand to improve the interfacial bond.

Resistance of Polymer (PET) - Mortar Composites to Aggressive Solutions

This paper describes an innovative use of plastic bottle waste as cement-substitution within composite materials for preventing chemical attacks or repairing various reinforced concrete structures. Various weight fractions of cement varying from 2.5% to 7.5% were substituted by the same weight of polyethylene terephthalate (PET). The specimens were tested in flexure and compressive strength and for chemical resistance to acid, basic solutions at 5% and for chloride ion permeability. From this study, it was found that the PET-modified mortars exposed to aggressive environments showed better resistance to chemical attack and higher resistance to chloride ion penetration than unmodified one without substantially affecting the mechanical strength in tap water. The addition of PET to the modified mortars, means reducing the penetration of aggressive agents. So, the mass loss of composites exposed to hydrochloric and acetic acid solutions is lower than those of unmodified mortar. The basic solutions are harmless for composite materials. The formations which appear such as different calcium salts were determined by X-ray diffraction and FT-IR.

Physical and Chemical Influence of Polyacrylate Latex on Cement Mortars

In this research, the physical and chemical influence of polyacrylate (PA) latex on cement-based materials were studied using polymer modified mortars with polymer/cement (P/C) ratios of 0%, 5% and 10%. Physically, the mechanical performance of PA latex modified mortars was investigated with compression toughness energy and bending strength. Further more, a comparison of the pore structure and porosity between PA latex modified and unmodified mortars was conducted. The chemical reactions between PA polymer and cement hydrates were clarified with thermogravimetric (TG) analysis. It can be concluded from this research that PA polymer can refine the pore structure of cement mortars and link the cement hydration products together chemically. While, at the same time, PA latex addition can cause air entrainment which will weaken the physical behavior of cement mortars. So there is an optimum P/C ratio to achieve the best mechanical properties. And in this research, the optimum P/C ratio is 5%.

STRENGTH DEVELOPMENT THROUGH LONG-TERM DRY CURING OF INITIALLY COMBINED WET/DRY-CURED AND STEAM-CURED HARDENER-FREE EPOXY-MODIFIED MORTARS

It is clarified by the previous studies that even without any hardener epoxy resin can harden in the presence of hydroxide ions from calcium hydroxide in the cement mortars and concretes at ambient temperature. The strength development through the long-term curing of hardener-free epoxy-modified mortars and concretes has hardly been examined till now. Hardener-free epoxy-modified mortars using an epoxy resin(diglycidyl ether of bisphenol A) without any hardener are prepared with various polymer-cement ratios, subjected to (1)initial combined wet/dry curing plus long-term dry curing and (2)initial steam curing plus long-term dry curing, and tested for hardening degree of epoxy resin and strength development. As a result, the application of the initial steam curing rather than the initial combined wet/dry curing causes a marked strength development with increasing polymer-cement ratio and additional dry curing period. The flexural and compressive strengths of the initially steam-cured plus 336-d dry-cured hardener-free epoxy-modified mortars with polymer-cement ratios of 10% or more are about 1.5 to 2.0 times higher than those of the initially steam-cured unmodified mortar. This is proved by a marked increase in the degree of hardening of the hardener-free epoxy resin in the epoxy-modified mortars with additional dry curing period.

폴리머 시멘트 복합체의 투수성 및 건조수축에 관한 연구

In a range of forms, such as latex, water-soluble polymer, liquid resin, and monomer, polymer dispersions have been widely used in the construction industry as cement modifiers because of their excellent properties, such as acid-resistance, water-proofness, and good ductility in mortar and concrete. Polymer cement slurry (polymer-modified slurry) is made of cement and polymer dispersions, with a high polymer-cement ratio of 50% or more. The purpose of this study is to evaluate the water permeability and drying shrinkage of polymer cement mortar (polymer-modified mortar) and cement concrete coated by polymer cement slurry. The polymer cement mortar and cement concrete are prepared with various polymer types, polymer-cement ratios and curing methods, and are tested for water permeability, drying shrinkage and strength. The test results showed thatthe weight of permeable water of polymer cement mortar decreases with an increase in the polymer-cement ratio, reaching a minimum at the polymer-cement ratio of 20%. In particular, the weight of permeable water of St/BA-modified mortar with a polymer-cement ratio of 20% coated with St/BA-modified slurry is about 1/55 that of unmodified mortar. The EVA- and St/BA-modified slurries coated on cement concrete have about 4 or 5 times higher drying shrinkage compared to cement concrete. The strength of polymer cement mortars tends to increase with a higher polymer-cement ratio, and is considerably higher than that of unmodified mortar. It is thus concluded that polymer cement mortars coated by polymer cement slurry are effective for industrial application, and have superior properties such as waterproofness and strengths, compared with conventional cement mortar.

Preparation and properties of a new composite of epoxy emulsion (EEM) modified cement

High performance cement based composite materials was prepared by adding epoxy emulsion. The epoxy emulsion was synthesized with epoxy phosphoric acid ester and poly-glycol in laboratory. This epoxy emulsion has advantages over other emulsion, such as dehydrated slightly, and, well film formation abilities. The mechanical properties corruptness resistance and structure of epoxy emulsion modified cement mortars were studied. Experimental results show that the mechanical properties of modified cement mortars are slightly increased with increasing epoxy emulsion content, especially the flexure strength. The corruptness resistance of all modified mortars is better than the unmodified mortar. The polymer film forms the bridge phases between the matrix and the aggregate regions, and forms a three-dimension structure in the cement hydration system, which improves the mechanical properties of modified mortars.

Physico-chemical characterization of EVA-modified mortar and porcelain tiles interfaces

EVA (poly(ethylene-co-vinyl acetate)) redispersable powders with different contents of copolymers were tested in order to evaluate their effects on the complex interactions developed at mortar/tile interface. EVA addition has increased the bond strength almost 40% when compared with unmodified mortar. Based on EVA hydrolysis, a novel method named as ‘Extension of Hydrolysis (EH)’ was suggested to monitor the reaction mechanism which occurred during the interface layer formation. Thus, higher EH values were related to a significant improvement of adhesion at interface observed as a changing on the failure mode from mostly cohesion to adhesion. Calculated EH parameter of 2.64 was associated with a cohesive component of rupture in the mortar of 50% while for an EH of 0.92, the rupture in the mortar was only 7%. The enhancement on adhesion was attributed to the hybrid ceramic–polymer interface formed based on hydrogen-bonds between silanol groups from tile surface and hydroxyl groups from hydrolyzed EVA.

Diffusion of chloride ions in polymer‐mortar composites

AbstractIn recent years, the rapid deterioration of various reinforced concrete structures has been a widely recognized problem in the world. Penetration of chloride ions into the concrete structures was found to be the major cause of premature corrosion of reinforcing steel and to promote their deterioration. The present articles deals with the resistance to chloride penetration of polymer‐mortar, which are often used as low‐cost promising materials for preventing or repairing various reinforced concrete structures. To gain more knowledge on the efficiency of polymer‐mortar, four mortar mixtures: one specimen with Portland cement (control sample) and three mixtures with 2.5, 5, and 7.5 wt % of the replacement of cement by polyethylene terephthalate (PET) were tested for chloride ion permeability under immersion in 5% sodium chloride solution. Their chloride ion penetration behavior is discussed by applying Fick's second law. In conclusion, the chloride ion penetration depth and apparent chloride ion diffusion coefficient of the polymer‐mortar composites are smaller than those of unmodified mortar. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

양생조건 및 보수방법에 따른 폴리머시멘트모르타르의 강도 성상

In this paper, polymer-modified repair materials using polymer dispersions with six repair methods are prepared with various polymer-cement ratios, and tested for compressive and flexural strengths through each curing condition such as dry cure, water cure, and freezing and thawing cyclic action. And, the adhesive interface between the polymer-modified mortar and mortar substrate is observed by a scanning electron microscope. From the test results, the compressive and flexural strengths of cement mortar repaired by polymer-modified mortar are improved with a rise in the polymer-cement ratio regardless of the type of polymer and curing conditions. Such an improvement in the strengths of polymer-modified repair materials to ordinary cement mortar is explained by the high adhesion of polymer-modified mortar. Strength reduction of polymer-modified repair materials after freezing and thawing cyclic actions is recognized, but it is lower than that of unmodified mortar. Especially, cement mortar repaired by polymer-modified mortar with a St/BA emulsion has good strength properties compared with those of SBR latex and PA emulsion. Accordingly, it is judged that polymer-modified mortars with a St/BA emulsion are possible to use as repair materials to ordinary cement mortar and concrete.

St/BA의 모노머 비에 따른 폴리머 시멘트 모르타르 개발에 관한 연구

The purpose of this study is to clarify the effect of the monomer ratio on properties of the polymer-modified mortars based on styrene and butyl acrylate latexes, and to obtain basic data necessary to develop appropriate latexes for cement modifiers. This paper deals with the effects of monomer ratio on the typical properties of the polymer-modified mortars with styrene and butyl acrylate latexes. The polymer-modified mortars using the styrene and butyl acrylate latexes polymerized with various monomer ratios are prepared with different polymer-cement ratios, and tested for the particle size of polymer latexes, air contents, water-cement ratios, flexural and compressive strengths, water absorption, and chloride-ion penetration. From the test results, the polymer-modified mortars using styrene and butyl acrylate latexes with the mix proportions of synthesis having monomer ratios of 50:50 to 60:40 for the appropriate mix proportions can be recommended for practical applications. Their basic properties are greatly affected by the polymer-cement ratio rather than the monomer ratio, and are improved over un-modified mortar.

Properties of polymer‐modified mortars based on methyl methacrylic latexes with emulsifier contents and various monomer ratios

AbstractThis study investigates the effects of the emulsifier content and monomer ratio on the typical properties of the polymer‐modified mortars with methyl‐methacrylate–butyl‐acrylate (MMA/BA) and methyl‐methacrylate–ethyl‐acrylate (MMA/EA) latexes and obtains basic data necessary to develop appropriate latexes for cement modifiers. The polymer‐modified mortars using the MMA/BA and MMA/EA latexes polymerized with emulsifier contents and at various monomer ratios are prepared for different polymer–cement ratios, and tested to obtain the particle size of the polymer latexes, the glass transition temperature of the polymer film, air contents, water–cement ratios, flexural and compressive strengths, water absorption, and chloride ion penetration. From the test results, the polymer‐modified mortars using MMA/BA and MMA/EA latexes with the mix proportions of synthesis having emulsifier contents of 5–6% and monomer ratios of 50 : 50 to 60 : 40 for the appropriate mix proportions can be recommended for practical applications. The basic properties of the polymer‐modified mortars are more affected by the polymer–cement ratio rather than the monomer ratio and emulsifier content, and are improved over unmodified mortar. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3010–3018, 2007

Study of cement mortars modified by emulsifier-free latexes

Abstract Cationic copolymer latex of vinyl acetate (VA) with methacryloxyethyl trimethylammonium chloride (MTC) and anionic copolymer latex of VA with sodium acrylate (SA) were prepared via emulsifier-free emulsion copolymerization. Modifications of cement mortars by these copolymer latexes were studied, and the results were compared with mortars modified by homopolymer of VA (PVA) as well as with blank mortars. The experimental results showed that flow of the mortars modified by PVA homopolymer and P(VA–MTC) copolymer latexes were increased compared with the blank, whereas a decrease was observed for that modified by P(VA–SA) anionic copolymer latex; a volume expansion was detected in polymer modified mortars by PVA and P(VA–MTC), while no volume expansion was observed in the anionic P(VA–SA) modified mortars; the flexural strength of mortars modified by P(VA–MTC) increased by 79.5% compared to unmodified mortars after 5 day water curing plus 21 day air curing. This value reached 95% when the curing process was followed by a supplementary 24 h vacuum curing. These polymer modified mortars were then subjected to hydration analysis through X-Ray diffraction (XRD). Mechanisms of the mortar modification are discussed based on the characterization results.

ＳＢＲラテックスと硬化剤無添加エポキシ樹脂を併用したポリマーセメントモルタルの強さ性状に及ぼす促進養生の効果

For the purpose of developing the early strength of concrete, accelerated curings such as steam and autoclave curings are widely applied to the manufacture of precast concrete products. The uses of polymer-modified mortar and concrete are also expected for precast products. The objective of the present study is to examine the application of effective accelerated curings to styrene-butadiene (SBR)-modified mortars with hardener-free epoxy resin. SBR-modified mortars with a hardener-free epoxy resin are prepared with various polymer-cement ratios, subjected to a 1-d steam curing after a 1-d moist curing, followed by a 1-d heat curing, and tested for flexural and compressive strengths. As a result, (steam + heat)-cured SBR-modified mortars with the hardener-free epoxy resin at polymer-cement ratios of 15% or more develop about three times higher flexural and compressive strengths than unmodified mortar. Such high strength development is attributed to the improved microstructures of interfacial transition zone by SBR-epoxy resin modification in the mortars. The optimal accelerated curing for the SBR-modified mortars with the hardener-free epoxy resin is recommended as follows: 1-d moist [20°C, 90% (RH)] +1-d steam (90°C) +1-d heat (100 or 120°C) curing.

Behavior of water glass–polymer hybrid-modified mortars under flowing sulfuric acid solution environment

As the second part of a research program, a comparison test research on the flowing sulfuric acid resistance of four kinds of mortars (namely water glass–polyvinyl acetate hybrid-modified mortar, water-glass-modified mortar, polyvinyl-acetate-modified mortar and unmodified mortar) was performed so that laboratory simulation matched site condition better. The test results show that the flowing sulfuric acid attack is much more severe than the static one. Both microscopic and macroscopic test results indicate that the behavior of the hybrid-modified mortars under the flowing sulfuric acid solution is significantly better than that of the control mortars.

Development of polymer films by the coalescence of polymer particles in powdered and aqueous polymer-modified mortars

This paper evaluates and compares the coalescence of polymer particles (continuous polymer films formation) in powdered polymer-modified mortars (PPMMs) and aqueous polymer-modified mortars (APMMs). Polymer-modified mortars (PMMs) using various redispersible polymer powders (powdered cement modifiers) and polymer dispersions (aqueous cement modifiers) were prepared by varying the polymer–cement ratio (P/C) and were tested for the characterization of polymer films using a scanning electron microscope (SEM) after curing for 28 days. It is concluded from the test results that mortar constituents of unmodified mortar (UMM) are loosely joined with each other due to the absence of polymer films, thus having a structure with comparatively lower mechanical and durability characteristics. By contrast, mortar constituents in PPMMs and APMMs are compactly joined with each other due to the presence of interweaving polymer films, thereby forming a monolithic structure with improved mechanical and durability characteristics. However, the results make obvious the poor coalescence of polymer particles or development of inferior quality polymers films in PPMMs as compared to that observed in APMMs. Moreover, PPMMs show less uniform distribution of polymer films as compared to that in APMMs. Different powdered cement modifiers have different film-forming capabilities. However, such difference is hardly recognized in aqueous cement modifiers. The polymer films in PPMMs and APMMs may acquire different structures. They may appear as mesh-like, thread-like, rugged, dense or fibrous with fine or rough surfaces. Development of coherent polymer films is not well pronounced at a P/C of 5% in PPMMs, whereas sometimes coherent polymer films are observed at a P/C of 5% in APMMs. At a P/C of 10% or more, fully developed, coherent polymer films are observed in both PPMMs and APMMs.

A note on the comparison of crack resistance of Ca(OH)2 crystals of unmodified and polymer-modified mortars in carbonated atmosphere

Abstract The purpose of this paper is to study morphologically the effects of carbonation on Ca(OH)2 crystals in unmodified mortar and polymer-modified mortars (PMMs). For this purpose, unmodified mortar and PMMs with 25 mix proportions were prepared with various polymer–cement ratios (P/C) and subjected to a nonpressurizing accelerated carbonation test (NPACT). It was concluded that Ca(OH)2 crystals formed in unmodified mortar were weak, unable to withstand stresses generated due to carbonation-related shrinkage and therefore cracked on exposure to CO2. By contrast, Ca(OH)2 crystals formed in PMMs were strong, withstood stresses generated due to carbonation-related shrinkage and did not crack on CO2 exposure.

Sulphuric acid resistance of soluble soda glass–polyvinyl acetate latex–modified cement mortar

In order to develop a sulphuric-acid-resistant mortar at a low cost a new idea to modify cement mortar by using soluble soda glass (sodium silicate) and polymer latex as main and supplementary modifying materials, respectively was proposed. In light of an exploratory test including five kinds of polymer latexes, the polyvinyl acetate latex was chosen as the supplementary modifier. Four different mortars, namely soluble glass–polyvinyl acetate modified mortar, polyvinyl acetate modified mortar, soluble glass modified mortar and unmodified mortar were then made for a detailed contratest research. The contratest results showed that the sulphuric acid resistance of the soluble glass–polyvinyl acetate modified mortar was significantly higher than that of the other kinds of mortars.

Influence of water-cement ratio and cement content on the properties of polymer-modified mortars

The compressive strength of modified and unmodified mortars depends on water-cement ratio and, to a lesser extent, on the cement content of the mortars. The flexural strength of unmodified mortars responds only slightly to modification of water-cement ratio or cement content. With polymer modification of the mortars, the influence of the variation is increased. There is only a minor influence of water-cement ratio and cement content on the adhesion strength of the modified mortars on concrete slabs. Only in wet conditions is there an additional effect at high cement contents and lower water-cement ratios. Shrinkage and water absorption are a function of water-cement ratio and cement content.

潜在硬化型エポキシ樹脂混入ポリマーセメントモルタルの性質

Conventional epoxy-modified mortars and concretes have an inferior balance between applicability and cost performance due to the necessity of two-component mixing of epoxy resin and hardener and high polymer-cement ratio of 50% or higher. In addition, the pot life of the mixture of the epoxy resin and hardener is limited after mixing them. In this study, the latent-curing epoxy resin containing microcapsuled curing agent which does not react with the epoxy resin at normal temperature and starts a chain reaction at 80°C or more is used as a one-component epoxy resin for cement modifier. Epoxy-modified mortars using the one-component epoxy resins and conventional two-component epoxy resins are prepared with polymer-cement rations of 5 to 20%, and subjected to flexural, compression, water absorption, drying shrinkage tests at the curing periods of 28 days. In the preparation of the polymer-modified mortars using the latent-curing epoxy resin, the specimens of the mortars are heat cured under 80°C for polymerization at 2 days after casting. From the test results, the one-component latent-curing epoxy-modified mortars have good workability, high flexural and compressive strengths, ductility and resistance to water absorption compared to those of the conventional two-component epoxy-modified and unmodified mortars. The one-component latent curing epoxy-modified mortar can successfully be used for preparing thin precast products because of such superior properties and smaller drying shrinkage after heat cure.