Polymer-modified Cement Research Articles

Mechanistic Properties of Hot-Mix Asphalt Mixtures Containing Hydrated Lime

Permanent deformation and moisture damage are common distresses found in pavements today. The use of hydrated lime is known to decrease moisture susceptibility, and as a mineral filler it increases the stiffness of the mixture. The objectives of this study were (a) to evaluate the fundamental engineering properties of hot-mix asphalt (HMA) mixtures containing hydrated lime compared with conventional mixtures designed to meet the current Louisiana Superpave® specifications and (b) to evaluate the influence of hydrated lime on the mechanical properties of the resulting HMA mixtures. Nine 19.0-mm Level 2 HMA mixtures were designed and examined. Siliceous limestone aggregates that are commonly used in Louisiana were included in this study. The nine mixtures were divided into three sets; each set contained three mixtures. The first set included three mixtures that are conventional, as control mixtures, containing no hydrated lime and an SB polymer-modified asphalt cement meeting Louisiana specifications for PG 76-22M, PG 70-22M, and a neat PG 64-22. The second set included three mixtures that contained hydrated lime that was incorporated into the aggregate and asphalt cement mixture as slurry. The asphalt cements used were identical to the ones used in the first set, namely PG 76-22M, PG 70-22M, and conventional PG 64-22. The third set included three mixtures that contained hydrated lime that was blended dry with the asphalt cements used in the first and second sets, that is, PG 76-22M, PG 70-22M, and PG 64-22. Mechanistic tests were conducted to define the permanent deformation and endurance life of HMA mixtures with and without hydrated lime. The results indicated that the addition of hydrated lime as a mineral filler improved the permanent deformation characteristics of the asphaltic concrete mixtures. This improvement was particularly apparent at higher testing temperatures with mixes containing polymer-modified asphalt and limestone aggregate.

속경형시멘트의 수화거동에서 폴리머의 영향

The properties of the polymer-modified mortars are influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases. Also, this quality of polymer modified cement strongly depend on weather condition. To overcome this problem, polymer-modified cement based on rapid setting cement mortars were prepared by varying polymer/cement mass ratio (P/C) with a constant water/cement mass ratio of 0.5. The effect of polymer on the hydration of this polymer cement is studied on different curing temperature. The results showed that the polymer mortar which is modified with rapid setting cement have superior physical strength properties on independent curing temperature. In addition the P/C ratio, the compressive strength, flexural strength, tensile strength and adhesion strength of mortar is enhances and polymer-modified cement based on rapid setting cement is more beneficial to the improvement of the mortar properties in jobsite.

Immobilization of Borate Waste Simulate in Cement-Water Extended Polyester Composite Based on Poly(Ethylene Terephthalate) Waste: 2-Frost Resistance of the Polymer Modified Cement Composite

Modified composite from water extended polyester (WEP); based on the recycled poly(ethylene terephthalate), (PET), and ordinary Portland cement (OPC) is a candidate matrix for processing borate waste solutions originating from the primary coolant circuit of pressurized water reactors (PWRs). This part of the work discusses the frost resistance of this polymer-modified cement composite (PCC) during the disposal course. Frost resistance is assessed for the candidate PCC after 115 cycles of freezing and thawing treatment (FTC) by evaluating their durability index, compressive strength, apparent porosity, volume of open pores, water absorption, and bulk density. Infrared (IR) and X-ray diffraction (XRD) as non-destructive analyses were performed for the candidate PCC before and after the freezing/thawing treatment to follow the changes that may take place during the hydration regime. The results obtained indicate that the candidate-modified cement composite exhibits acceptable resistance to freezing and thawing treatment even at very exaggerating conditions (−19°C and +60°C).

Mechanism of a vegetable waste composite with polymer-modified cement (VWCPMC)

Abstract In search for improved construction materials and techniques, two main factors must be taken into account: ecological impact and production costs. The incorporation of recycled materials originating from renewable sources into cementitious cores is a feasible alternative that has gained ground in civil construction. This study investigated the matrix of a vegetable waste composite with polymer-modified cement. Several mixtures composed of Slag-Modified Portland cement, treated vegetable residue, wood from the Pinus caribaea species, latex type polymer, styrene–butadiene rubber (SBR) and an adequate water ratio for the mixtures were studied. The composite was characterized based on mortar tests carried out according to ABNT norms to determine its mechanical behavior, workability and water absorption by capillarity. Some of the essential properties of mortars, such as workability, mechanical strength and durability were substantially altered by the addition of polymers when compared to mortars without this addition. The effect of reduced capillary pores resulting from the action of the polymer contributed to decrease in the permeability of the material, preventing the penetration of aggressive agents due to the phenomenon of water transport. The composite containing vegetable residues and SBR-modified core presented the best mechanical behavior, and an increase of the polymer content resulted in greater water retention in the fresh mixture and a significant reduction in porosity.

Ｓｐｒｉｎｇ‐８放射光Ｘ線回折法によるＥＶＡエマルション中のアルミナセメントの水和過程

Polymer-modified mortars which consist of a polymer emulsion and cement materials have been widely developed in the construction materials fields. Forming process of the polymer-modified cement membrane simultaneously involves evaporation of water within the polymer emulsion and hydration of cement. It is important for the polymer-modified cement paste that the hydrate crystal of cement is generating by the hydration during the setting process under existence of the polymer emulsion. In this study, hydration process for calcium-aluminate cement under existence of poly (ethylene-vinyl acetate) (EVA) emulsion (polymer-cement ratio = 100%) was investigated by X-ray diffraction method using synchrotron radiation (SPring-8). The diffraction peaks of calcium aluminate (CA) disappeared after the hardening, on the other hand, the peaks of hydrate crystals of calcium-aluminate cement (C2AH8 and C3AH6) could be observed. This polymer-modified cement paste hydrated using the water within the polymer emulsion. The hydration of C2AH8 from CA started at around 300min, and then C3AH6 hydrate crystal increased after 700min at ambient temperature. This implies that the conversion from C2AH8 to C3AH6 occurred to be more stable phase. The setting temperature affected the reaction rate. In case of hydration at 35°C, the start time of the hydration for calcium-aluminate cement was quicker than that in the ambient temperature four or more times.

Physical and mechanical properties of styrene–butadiene rubber emulsion modified cement mortars

Polymer-modified cement mortars were prepared by varying polymer/cement mass ratio (P/C) with a constant water/cement mass ratio of 0.4. The effect of styrene–butadiene rubber (SBR) emulsion on the physical and mechanical properties of cement mortars is studied. With P/C below 10%, the toughness of the modified mortars enhances with the increase of P/C. A relationship between the physical and mechanical properties of the modified cement mortars at P/C below 10% is found; that is, the compressive strength and flexural strength of the modified mortars are directly proportional to the apparent bulk density. But when P/C is above 10%, the mechanical properties are not highly dependent on the apparent bulk density, and the flexural and compressive strength of the mortars are not improved further with more polymer. Two curing methods [wet cure: 2, 6 or 27 days immersed in 20 °C water; mixed cure: 6 days immersed in 20 °C water followed by 21 days at 20 °C and 70% relative humidity (RH)] were also evaluated in this paper. The results have shown that the mixed cure is more beneficial to the improvement of the mortar properties. A possible mechanism for polymer modification and the relationship between the physical and mechanical properties is proposed based on SEM and IR analyses. The interpenetrating structure between the polymeric phase and cement hydrates forms at a P/C of 8%, and fully develops at a P/C of 10%. The properties of the polymer-modified mortars are influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases.

Macrodefect-Free Materials: Modification of Interfaces in Cement Composites by Polymer Grafting

MDF materials are chemically bonded ceramic materials free of the macrodefects typical of hydraulic cement-based materials. MDF materials arising through reactions of sulfo-aluminate-ferrite belitic (SAFB) clinkers and/or Portland cements (PC) with two types of water-soluble polymer (hydroxy-propylmethyl cellulose {HPMC}, polyphosphate glass {poly-P}) are discussed. Mixes of low energy SAFB clinkers with Portland cement, HPMC and, especially poly-P comprise promising cross-linked compositions additional to the better known MDF materials formed from high alumina cement with polyvinylalcohol/acetate. The principles of co-ordination of P and C atoms (of the polymer) with Al and Fe atoms (originating from the cement) are highlighted from spectroscopic information on next-nearest-neighbour interactions, along with the effects of second co-ordination spheres. Polymers modify the interface through functional bonding/grafting of polymer chains onto the surfaces of cement grains. Both the cross-linked atomic structure and the interface coincide well with the model of functional polymers and represent a new type of atomic-level structure in polymer-modified cements. Interpretation is based on previous magnetic resonance and thermal analysis studies. The compactness of Al(Fe)-O-P cross-links reduces transport through the interfaces, increasing the interfacial interactions and resisting the unfavourable uptake of moisture and carbonation.

Polymer Effects on the Vibration Damping Behavior of Cement

In this paper, the vibration damping properties of polymer-modified-cement (PMC) have been studied. The storage modulus (E′) and loss tangent (tan δ ) of PMC were studied by using a free vibration method. The propagation velocity of stress wave V and the scattered damping of stress wave in PMC were studied by using an ultrasonic testing method. When a suitable polymer is added in the cement, the storage modulus, the velocity of stress waves are decreased with an increase of the polymer/cement ratio (P/C), and the loss tangent is increased with an increase of P/C, thus the ability to vibration damping of PMC is improved. As the P/C is between 15 and 20%, the PMC demonstrates the best vibration damping within the adopted range of testing.

Study of the performance of four repairing material systems for hydraulic structures of concrete dams

Four types of repairing materials are studied as function of either a conventional concrete or a reference-concrete (RefC), these are: polymer-modified cement mortar (PMor), steel fiber concrete (SFco), epoxy mortar (EMor) and silica fume mortar (SFmo), to be applied in hydraulic structures surfaces subjected to a high velocity water flow. Besides the mechanical requests and wearing resistance of hydraulic concrete dam structures, especially the spillway surfaces, the high solar radiation, the environmental temperature and wet and dry cycles, contribute significantly to the reduction of their lifespan. RefC and the SFco were developed based on a usual concrete mixture used in slabs of spillways. The average RefC mixture used was 1: 1.61: 2.99: 0.376, with Pozzolan-modified Portland cement consumption of 425 kg/m³. EMor and PMor mixtures followed the information given by the manufacturers and lab experience. Tests on concrete samples were carried out in laboratory simulating normally found environmental situations in order to control the mechanical resistance and the aging imposed conditions, such as solar radiation and humidity. Also, physicochemical characterizing tests were made for all used materials. From the analyzed results, two of them presented a higher performance: the EMor and SFmo. SFco presented good adherence to the RefC and good mechanical performance. However, it also presented apparent metal corrosion in humidity tests, being indicated for use, with caution, as an intermediate layer in underwater repairs. In a general classification, considering all tests, including their field applications, the better performance material systems were EMor- SFmo> SFco> PMor.

防錆剤混入ポリマーセメントモルタルによる塩害劣化コンクリート中の鉄筋の防食効果

In Japan, the polymer-modified cement mortar (PCM) with the corrosion inhibitor has often been used as repair materials for deteriorated reinforced concrete structures due to the chloride-induced steel corrosion. In this study, the reinforced concrete specimens with two levels of chloride content were prepared and exposed to wet and dry cycles in the chamber for a long period to clarify the macro-cell corrosion of steel bar in the concrete. The effectiveness of the type and dosage of corrosion inhibitor, LiNO2 or Ca(NO2)2, in PCM and the degree of chipping around steel bars in repair work in preventing the steel corrosion in concrete were comparatively investigated by means of electro-chemical measurements such as linear polarization resistance and AC impedance methods.From the experimental results, it was found that PCM with both corrosion inhibitors of LiNO2 and Ca(NO2)2 had almost the same effect in preventing the steel corrosion when their NO2- molecular ratio to Cl- was constant, and that the chipping and patching work beyond steel bars was more effective in restoring the passive state of steel bars. Furthermore, both the linear polarization resistance and the AC impedance methods were very useful as a nondestructive inspection method for estimating the corrosion behavior of steel bars in repaired and unrepaired concrete with PCM.

Properties of polymer-modified cement mortar using pre-enveloping method

A new method, pre-enveloping sand with polymer, was adopted to make polymer-modified cement mortar (PCM). In the research, two kinds of latex, i.e., styrene acrylate rubber and styrene butadiene rubber, were used. The experimental results of physical and mechanical tests showed that, at the same level of polymer cement ratio, pre-enveloping method was better than normal method regarding the performance of the resulted composite. Moreover, in the condition of relatively low addition of polymer, the improvement of physical and mechanical properties, especially the resistance to cycling of freezing–thawing, by the pre-enveloping method was more significant. Additionally, it was found that styrene butadiene rubber can improve the fluidity of the mortar, and mortar with styrene acrylate rubber can maintain the same fluidity as the control sample by adding small quantities of a superplasticizer. Styrene acrylate rubber had no water-reducing ability by itself.

Effect of rebar cleanliness and repair materials on reinforcement corrosion and flexural strength of repaired concrete beams

This paper presents result of a study conducted to evaluate the effect of two rebar cleaning procedures and repair materials on reinforcement corrosion and flexural strength of repaired concrete beams. The steel bars in the reinforced concrete beams were corroded to varying degrees to simulate field situations and then repaired utilizing two different cleaning techniques and two repair materials. The repaired beams were then tested in flexure to evaluate the effect of cleaning method and repair materials on the corrosion-resistance and flexural capacity of repaired beams. The electrochemical behavior of cleaned and corroded steel bars was evaluated by conducting a DC potentiodynamic scan. The data indicated an insignificant change in the flexural strength of repaired beams regardless of the cleaning techniques or the repair materials. The accelerated corrosion data indicated lowest corrosion rate in the concrete specimens repaired with polymer-modified cement mortar after cleaning the bars by sand blasting (SB). The DC polarization data indicated the formation of a stable passive film on the steel bars cleaned by SB compared to uncleaned bars and those cleaned by wire brush.

Experimental study on properties of polymer-modified cement mortars with silica fume

This paper discussed the flexural and the compressive strengths of polyacrylic ester (PAE) emulsion and silica fume (SF)-modified mortar. The chloride ion permeability in cement mortar and the interfacial microhardness between aggregates and matrix were measured. The chemical reactions between polymer and cement-hydrated product were investigated by the infrared spectral technology. The results show that the decrease of porosity and increase of density of cement mortars can be achieved by the pozzolanic effect of SF, the water-reducing and -filling effect of polymer. Lower porosity and higher density can give cement mortars such properties as higher flexural and compressive strength, higher microhardness value in interfacial zone and lower effective diffusion coefficient of chloride ion in matrix.

Pore size distribution of hydrated cement pastes modified with polymers

Mercury intrusion porosimetry (MIP) tests were performed on pure and polymer-modified cement pastes in order to evaluate the influence of hydroxyethyl cellulose (HEC polymer) and vinyl acetate/ethylene copolymer (EVA) on the pore size distribution. Cement pastes containing 0%, 10%, and 20% of EVA and 0%, 0.5%, and 1.0% of HEC of the weight of cement were prepared and the water/cement ratio was kept constant (0.4). The effects of two curing methods (dry cure: 27 days at 23°C and 75% relative humidity (RH); mixed cure: 7 days at 23°C under sealed conditions and 20 days at 23°C and 75% RH) were also evaluated. Analysis of variances (ANOVA) showed that the most important factors affecting pore size distribution are the curing method and EVA content.

Flexural behaviour of reinforced concrete beams repaired with styrene—butadiene rubber latex, silica fume and methylcellulose repair formulations

The use of plain cement mortar in repair works is limited to unimportant works because of its poor adhesive bond to the substrate and its performance from the point of view of durability. Polymer-modified cement mortar has replaced plain mortar for these reasons. Also, the incorporation of silica fume and methylcellulose in repair systems has been found to provide a better durability and overall performance. This paper presents the results of an experimental investigation of the flexural behaviour of six reinforced concrete beams. Five beams were repaired using five different repair systems, namely plain cement mortar and mortars modified with latex (L), latex and silica fume (L—S), latex silica fume and methylcellulose (L—S—M), and silica fume and methylcellulose (S—M). The sixth beam was an unrepaired control beam. The repair procedure was carried out while loading the beams, to match the on-site practice. The size of the beams was 100 X 150 X 1200 mm and they were reinforced with two 10 mm diameter steel rods with a yield strength of 551 MPa. The test results showed that beams repaired with L, L—S and L—S—M mortars successfully restored the structural capacity of the unrepaired beam, besides improving the durability, crack pattern and toughness characteristics of these beams. The use of plain or S—M mortars showed a poor structural performance since they exhibited early separation along the contact interface with the substrate, as well as reduced ductility and toughness.

Microstructural aspects in a polymer-modified cement

Scanning electron microscopic observations of polymer-free and polymer-modified cements have shown that the polymer particles are partitioned between the inside of hydrates and the surface of anhydrous cement grains. Differential thermal analysis, thermogravimetric analysis, and porosimetry experiments show the retardant effect of the polymer and provide information on changes in porosity.

Network morphology of straight and polymer modified asphalt cements.

Asphalt cements are often regarded as a colloidal system containing several hydrocarbon constituents: asphaltenes, resins, and oils. The high molecular weight asphaltene particles are considered to be covered in a sheath of resins and dispersed in the lower molecular weight oily medium [Whiteoak (1990) The Shell Bitumen Handbook (Shell Bitumen UK, Riversdell House, Surrey, UK)]. However, the exact arrangement of the asphaltene particles within the oily phase will vary depending on the relative amounts of resin, asphaltene, and oils. It is this arrangement and the degree of association between asphaltene particles that govern the rheological properties of the cement [Simpson et al. (1961) J. Chem. Eng. Data 6:426-429; Whiteoak (1990)]. Here we report for the first time the observation of a three-dimensional network of asphaltene strands within straight, polymer-modified, and aged asphalt cements. While the existence of a asphaltene/resin micelle network has been proposed in previous studies [Whiteoak (1990)], direct observation has not been reported. The network is expected to greatly influence the rheological properties of the asphalt binder and ultimately the properties of asphalt concretes. In situ fracture studies of asphalt cement/aggregate composites indicate a possible correlation between the network structure and adhesion between the cement binder and aggregate.

The effect of polymer addition on the electrical behavior of ordinary and pulverized fly ash modified cement mortars

The electricla behavior of polymer-modified cement mortars has been evaluated as a function of the polymer and the evaporable water contents. The effects have been correlated to microstructural changes induced by the addition of an acrylic polymer and an epoxy resin purposely formulated for cement-based composites. Moreover, the effect of the addition of pulverized fly ash, which has proved to be beneficial on many of the cement composite properties, has also been studied. Polymer modified cement mortar composites exhibit a tendency towards insulating behavior which is greatly enhanced by water losses: the electrical properties must thus be carefully evaluated when static charge accumulation is not desired. The addition of pulverized fly ash to ordinary Portland mortars slightly influences the electrical behaviour, but strongly enhances the insulating behaviour of polymer modified cement mortars.

Prevention of air void formation in polymer-modified cement mortar by pre-wetting

The air voids that form when cement and aggregates are mixed with an aqueous polymer solution are not easily removed because they tend to be stabilized by the polymer. Antifoaming agents can be used to prevent air void formation, but they often cause problems of poor adhesion. An alternative approach is suggested for reducing air void formation in polymer-modified mortar, which is to pre-wet the cement and sand with water, and then add a concentrated polymer solution. The air content of a PVA-modified cement mortar prepared in this way was as low as 6%, which was lower than the 13% air content of the PVA-modified mortar with an antifoaming agent, and it was much lower than the 32% air content when a PVA solution was mixed with dry cement and sand.

The Evolution of the Microstructure in Styrene Acrylate Polymer-Modified Cement Pastes at the Early Stage of Cement Hydration

The Evolution of the Microstructure in Styrene Acrylate Polymer-Modified Cement Pastes at the Early Stage of Cement Hydration