Organo-modified reservoir sludge as fine aggregates in cement mortars

In Taiwan, a considerable amount of reservoir sludge is being increasingly difficult to dispose of in landfills and creates serious disposal problems. Attempts have been made to study the feasibility of using reservoir sludge as a substitute for a portion of fine aggregates in cement mortars. Reservoir sludge in Taiwan mainly composed of smectite clay is first organo-modified by a cationic-exchange reaction. The compressive strengths and permeability ratios of cement mortars with various percentages of organo-modified reservoir sludge (OMRS) particles were measured and then compared to those of plain cement mortars. The experimental results indicate that it could be possible to replace up to 30% by weight of fine aggregates by OMRS particles in a cement mortar for normal practice. Meanwhile, OMRS particles can be used in controlled low-strength materials (CLSM) if their replacement percentage for fine aggregates is higher than 80%. Also, excellent waterproof of cement mortars is achieved when the percentage of OMRS particles is within the range of 5–50%.     

Cement paste–epoxy adhesive interactions

In the field of civil engineering, the durability of concrete assemblies using adhesives is widely conditioned by the properties of the interface between the resin and the mineral support (concrete). In this context we studied first the molecular interactions at the interface between an epoxy resin and cement pastes by several approaches based on XPS and IR spectroscopies, DSC, and inverse gas chromatography (IGC). XPS showed evidence of crosslinking of the polymer at the surface of hardened cement pastes. XPS chemical shifts of the N1s peak from the adsorbed hardener testified for the existence of interfacial donor–acceptor interactions between the cement and hardener. Such a specific interaction is probably responsible for the increase in the of glass transition temperature (T_g) of the adhesive near the cement substrate surface. FTIR study of the interactions of the epoxy adhesive with the main hydrates taken separately (namely C–S–H, ettringite and portlandite) permitted to better understand the complex cement paste–adhesive interfacial system. The IGC-determined dispersive and acid–base components of the surface energy of the cement pastes were found to be depressed after coating, a result that correlates with surface chemical composition data. Small area XPS analysis of cement paste/adhesive interphase revealed, on a prototype of cement paste–adhesive joint, modifications of the Ca2p and N1s regions, which suggests that this zone is the locus of chemical reactions that favour mineral substrate–resin adhesion. Small area XPS firmly showed the existence of a diffuse interphase rather than a sharp cement paste–adhesive interface.     

Feasibility study of asphalt-modified mortars using asphalt emulsion

Asphalt emulsion is manufactured by emulsification of asphalt, and it is an energy-saving, ecologically safe material because it does not need any heating processes creating gas emission and fire hazard in its use. The purpose of this study is to evaluate the feasibility on the use of an asphalt emulsion as a polymeric admixture. Asphalt-modified mortars using an experimentally manufactured asphalt emulsion are prepared with various polymer–cement ratios, and tested for strengths, adhesion, water absorption, water permeation, carbonation and chloride ion penetration. As a result, it is found that waterproofness, carbonation resistance and chloride-ion penetration resistance of the asphalt-modified mortars are markedly improved with the increase in the polymer–cement ratio, while their compressive strength and adhesion to mortar substrates are reduced with the increase in polymer–cement ratio. Therefore, it is recommended to control their polymer–cement ratios to be less than 10% in practical applications. Further study to improve their compressive strength and adhesion is suggested.     

Effect of a polypropylene fibre on the behaviour of aerial lime-based mortars

A polypropylene fibre was added to lime-based mortars in order to check whether they were improved by this admixture. Different properties of lime-based mortars were evaluated: fresh state behaviour through water retention, air content and setting time; hardened state properties such as density, shrinkage, water absorption through capillarity, water vapour permeability, long-term flexural and compressive strengths, pore structure through mercury intrusion porosimetry, and durability assessed by means of freezing–thawing cycles. An improvement in some properties of aerial lime-based mortars – such as permeability, mechanical strengths, reduction in macroscopic cracks or durability in the face of freezing–thawing cycles – was achieved when fibre was added at a low dosage. When a larger amount of additive was used, only the reduction in cracks and the durability of the material were improved.     

The influence of different curing conditions onthe pore structure and related properties of fly-ash cement pastes and mortars

The influence of two different curing conditions (in water at 27°C, and in air at 15°C and 60% relative humidity) on the mechanical and durability properties of fly-ash cement pastes and mortars are studied. Cement pastes and mortars at two water/cement or binder ratios were prepared in the laboratory and tested for compressive strength, chloride and water penetration. The mercury intrusion porosity of the samples is monitored to provide mechanistic explanations for the measured results. The results show that fly ash has significantly different influence on the strength, porosity and durability parameters of cement pastes and mortars when the cementitious materials are subjected to different curing conditions.     

Properties of cement mortars containing clinoptilolite as a supplementary cementitious material

This paper presents a study of the properties and behavior of cement mortar with clinoptilolite which is one of the most common zeolite minerals found in nature. Six mortar mixtures were prepared by replacing the Portland cement with 0%, 5%, 10%, 15%, 20% and 30% clinoptilolite by weight. Test results showed that water demand, soundness and setting times of the cement pastes increased with the increase of clinoptilolite content. Compressive and flexural strength of the mortars containing clinoptilolite were higher than the control mixture. Dry unit weight of the mortars with clinoptilolite was lower than the control mortar. Clinoptilolite replacement decreased water absorption and porosity of the mortars. The control mortar showed less durability to carbonation compared to the mortars made with clinoptilolite at the end of carbonation tests. Freeze–thaw resistance of the mortars containing 5% clinoptilolite was higher than control mortar. The effect of clinoptilolite incorporation on high-temperature resistance seemed to be dependent on amount of clinoptilolite, temperature level, and the cooling method.     

Effect of Granulated Blast Furnace Slag and fly ash addition on the strength properties of lightweight mortars containing waste PET aggregates

In this work, the effect of Granulated Blast Furnace Slag (GBFS) and fly ash (FA) addition on the strength properties of lightweight mortars containing waste Poly-ethylene Terephthalate (PET) bottle aggregates was investigated. Investigation was carried out on three groups of mortar specimens. One made with only Normal Portland cement (NPC) as binder, second made with NPC and GBFS together and, third made with NPC and FA together. The industrial wastes mentioned above were used as the replacement of cement on mass basis at the replacement ratio of 50%. The size of shredded PET granules used as aggregate for the preparation of mortar mixtures were between 0 and 4 mm. The waste lightweight PET aggregate (WPLA)–binder ratio (WPLA/b) was 0.60; the water–binder (w/b) ratios were determined as 0.45 and 0.50. The dry unit weight, compressive and flexural–tensile strengths, carbonation depths and drying shrinkage values were measured and presented. The results have shown that modifying GBFS had positive effects on the compressive strength and drying shrinkage values (after 90 days) of the WPLA mortars. However, FA substitution decreased compressive and flexural–tensile strengths and increased carbonation depths. Nevertheless a visible reduction occurred on the drying shrinkage values of FA modifying specimens more than cement specimens and GBFS modified specimens. The test results indicated that, GBFS has a potential of using as the replacement of cement on the WPLA mortars by taking into consideration the characteristics. But using FA as a binder at the replacement ratio of 50% did not improve the overall strength properties. Although it was thought that, using FA as binder at the replacement ratio of 50% for the aim of production WPLA concrete which has a specific strength, would provide advantages of economical and ecological aspects.     

PB-g-PS胶乳改性水泥砂浆的性能

利用氧化还原引发体系,采用半连续乳液接枝共聚的方法合成了聚丁二烯接枝聚苯乙烯(PB-g-PS)接枝共聚胶乳,其中聚丁二烯(PB)与聚苯乙烯(PS)的质量比为70/30,50/50和30/70.在固定流动度为(175±5)mm,且在20℃水中养护6 d,然后在20℃,相对湿度为65%的空气中养护21 d的混合养护条件下,考察了聚灰比、聚丁二烯与聚苯乙烯的质量比对PB-g-PS胶乳改性水泥砂浆的水灰比、流动度、保水率、抗压和抗折强度以及吸水量的影响,并与羧基丁苯胶乳改性水泥砂浆进行了性能对比试验.结果表明:在一定掺量范围内,胶乳都具有良好的减水作用,能有效提高砂浆的保水性能,显著降低聚合物改性砂浆的毛细孔吸水率;加入聚合物对砂浆力学性能有重要影响,使其抗压强度总体降低,抗折强度部分提高,因此,PB-g-PS胶乳可以作为水泥改性剂使用.     

Investigation of mechanical and mineralogical properties of mortars subjected to sulfate

The durability can be described as concrete’s resistance to the destructive influences of a medium containing acid, sulfate and/or various chemicals and mechanical effects. The main objective of this study is investigation of mechanical and mineralogical properties of cement mortar with different pozzolanic compositions and subjected to sulfated medium. In the study, the mortars produced with cement samples having seven different compositions and varied with an air-entraining agent were subjected to the influence of sulfate. This study is supported by thin section and X-ray powder diffraction (XRPD) investigations, in addition to being subjected to the basic tests, such as compression and flexure. The most important findings obtained from the study are that the compact structure has more effective properties against sulfate effects for cement mortars than pozzolanic materials’ effects and the highest pozzolanic material ratio is restricted about 25–30% by mass because this ratio is a boundary of mechanical properties.     

Properties of polymer-modified mortars using epoxy and acrylic emulsions

Water based polymer systems are often used for improvement in the properties of plain cement mortar or concrete. Presently, latexes of a single or combinations of polymers like polyvinyl acetate, copolymers of vinyl acetate–ethylene, styrene–butadiene, styrene–acrylic, and acrylic and styrene butadiene rubber emulsions are generally used. One of the limitations of these polymer systems is that they may re-emulsify in humid alkaline conditions. To overcome this problem, an epoxy emulsion based polymer system has been developed. In this paper the properties of the cement mortar modified with this newly developed epoxy emulsion are compared with those of the acrylic-modified mortar. The results showed that the mortars with the newly developed system have superior strength properties and better resistance to the penetration of chloride ions and carbon dioxide.     

Evaluation of coatings,mortars and mix design for protection of concrete against sulphur oxidising bacteria

Deterioration of concrete in cooling tower basins by microbiologically influenced corrosion (MIC) is a concern in geothermal power plants. The effect of supplementary cementitious materials, epoxy coatings, latex-modified mortars and calcium aluminate cement mortar for protecting concrete from MIC was investigated. Laboratory exposure tests to a particular type of sulphur and iron oxidising bacteria, Thiobacillus ferrooxidans, were performed to rank candidate materials and these were followed by field exposure tests of the best materials in a cooling tower basin. It was determined that partial replacement of cement with 40% blast furnace slag or 5% to 10% silica fume improved resistance to MIC. A replacement level of 60% slag resulted in similar performance to concrete made with ordinary Portland or sulphate resistant cement. Epoxy- and styrene butadiene latex-modified mortars offered protection to concrete but still underwent a degree of attack. Epoxy coatings were found to be effective in protecting concrete. Calcium aluminate cement mortar showed excellent durability in laboratory and field tests.     

Effect of copper slag as a fine aggregate on the properties of cement mortars and concrete

An experimental investigation was conducted to study the effect of using copper slag as a fine aggregate on the properties of cement mortars and concrete. Various mortar and concrete mixtures were prepared with different proportions of copper slag ranging from 0% (for the control mixture) to 100% as fine aggregates replacement. Cement mortar mixtures were evaluated for compressive strength, whereas concrete mixtures were evaluated for workability, density, compressive strength, tensile strength, flexural strength and durability. The results obtained for cement mortars revealed that all mixtures with different copper slag proportions yielded comparable or higher compressive strength than that of the control mixture. Also, there was more than 70% improvement in the compressive strength of mortars with 50% copper slag substitution in comparison with the control mixture. The results obtained for concrete indicated that there is a slight increase in density of nearly 5% as copper slag content increases, whereas the workability increased significantly as copper slag percentage increased compared with the control mixture. A substitution of up to 40–50% copper slag as a sand replacement yielded comparable strength to that of the control mixture. However, addition of more copper slag resulted in strength reduction due to the increase in the free water content in the mix. Also, the results demonstrated that surface water absorption decreased as copper slag content increases up to 50% replacement. Beyond that, the absorption rate increased rapidly and the percentage volume of the permeable voids was comparable to the control mixture. Therefore, it is recommended that up to 40–50% (by weight of sand) of copper slag can be used as a replacement for fine aggregates in order to obtain a concrete with good strength and durability requirements.     

Durability of blast-furnace slag mortars subjected to sodium monofluorophosphate application

The aim of this study is to investigate the effect of sodium monofluorophosphate (Na-MFP) on frost scaling durability and transport properties of carbonated blast-furnace slag cement (BFSC) mortar. The application of Na-MFP solution as curing solution and also surface treatment compound for BFSC mortar was evaluated. Three different Na-MFP solutions with concentrations of 10%, 20% and 30% by weight. in water were used as curing solution and surface treatment compound. The experimental results reveal that both techniques significantly improve the frost salt scaling durability and microstructure of carbonated blast-furnace slag mortar. Moreover, the carbonation rate and capillary water uptake of the treated mortars were substantially decreased compared with the untreated specimen. The mortars cured in Na-MFP solution show higher compressive strength than the untreated control after carbonation exposure. In general, the durability performances were improved when increasing the concentration of the Na-MFP solution applied.     

Effect of fineness of ash on pozzolanic properties and acid resistance of sugarcane bagasse ash replaced cement mortars

This paper addresses the potential use of Sugar Cane Bagasse Ash (SCBA) as a pozzolanic material for partial cement replacement in concrete mixtures. Cement mortars containing SCBA having five different particle size distributions at a replacement rate of 20% by weight were used to study the chemical and physical pozzolanic properties of SCBA. The durability of SCBA replaced mortars was also evaluated. SCBA with 0% retained on sieve No. 325 was used to replace 20% by weight of cement and create mortar specimens that were subjected to sulfuric acid attack of varying concentrations (1%−3% by weight of water). The tested samples were observed to check visual distortion, mass loss, and compressive strength loss at 1, 7, 14, 28, and 56 d of acidic exposure, and the results were compared to those for the control sample, that was lime water cured, at the same ages. The SCBA sets were found to meet the requirements for pozzolan class N specified by ASTM C 618. Mortars containing SCBA with 0% or 15% retention produced better compressive strength than the control mortars after 28 d. Additionally, X-ray fluorescence and X-ray diffraction analysis showed that the SCBA had favorable chemical properties for a pozzolanic material. Furthermore, SCBA replaced samples at all ages showed improved resistance against acidic attack relative to that of the control mortars. Maximum deterioration was seen for 3% concentrated solution. This study’s findings demonstrated that SCBA with an appropriate fineness could be used as a pozzolanic material, consistently with ASTM C 618.     

Mechanical characterization of polymer mortars exposed to degradation solutions

A comparative study of the influence of chemical degradation effects on flexural and compressive strength of polymer mortars was performed. For this purpose, epoxy polymer mortars specimens were exposed to eight different degradation agents represent those that often account for corrosive processes in industrial environments. After exposure and mechanical tests a decrease in flexural and compressive strength of the samples exposed to corrosive agents was observed. However, even in those samples, the remaining strength values were far higher than those found in mortars prepared with portland cement concrete and an inorganic binder.     

Properties of zeolitic tuff (clinoptilolite) blended portland cement

The aim of this study is to examine physical, chemical, mechanical and microstructural properties of mortars produced by blending clinoptilolite, which is a zeolite mineral abundantly found in nature, into Portland cement with increasing ratios. It was observed that plasticity times extend depending on the blend ratios of clinoptilolite blended cements and that early strengths change according to Blaine values. It was also determined that the final strengths develop in proportion to reactive SiO₂ and ion exchange capacity of clinoptilolite depending on the CH level in the medium.     

Effects of curing regimes and cement fineness on the compressive strength of ordinary Portland cement mortars

Curing techniques and curing duration have crucial effects on the strength and other mechanical properties of mortars. Proper curing can protect against moisture loss from fresh mixes. The objective of this experimental work is to examine the compressive strength of ordinary Portland cement mortars (OMs) under various curing regimes and cement fineness. Six different curing methods including water, air, water heated, oven heated, air–water, and water–air were applied to the specimens and also six groups of mortars were used. The results showed that the highest and lowest compressive strengths are attributed to the specimens of OPC mortar water cured using grounded OPC for duration of 6 h (OM–G6–wc) and OPC mortar air cured under room temperature with oven heated after demoulding of the specimens at 60 °C for duration of 20 h (OM–OH–ac), respectively. The maximum levels obtained of compressive strengths at 7, 28, and 90 days are 57.5, 70.3, and 76.0 MPa, respectively.     

Property evaluation of magnesium phosphate cement mortar as patch repair material

The properties of magnesium phosphate cement (MPC) mortars with different magnesium to phosphate (M/P) molar ratios and sand to binder (S/B) weight ratios have been investigated. The experimental results show that both M/P and S/B ratios have large influence on the setting time and mechanical properties of MPC mortars. Therefore, the formulation has to be optimized in terms of the workability, performance, as well as cost consideration. Besides, the bond strength is an important performance index for a patch repair material and hence received particular attention in this study. The test results demonstrate that MPC mortars have superior bond strength to ordinary Portland cement (OPC) mortar/concrete substrate. Finally, the volume stability measurements illustrate that the drying shrinkage of MPC based repair mortars is much less than that of OPC mortar. It is demonstrated that MPC mortar is promising to be utilized in patch repair and maintenance works of concrete.     

Sulfate resistance of blended cements containing fly ash and rice husk ash

In this paper, the sulfate resistance of mortars made from ordinary Portland cement containing available pozzolans viz., fly ash and ground rice husk ash (RHA) was studied. Class F lignite fly ash and RHA were used at replacement dosages of 20 and 40% by weight of cement. Expansion of mortar prisms immersed in 5% sodium sulfate solution and the change in the pH values of the solution were monitored. The incorporation of fly ash and RHA reduced the expansion of the mortar bars and the pH values of the solutions. RHA was found to be more effective than fly ash. Examination of the fractured surface of mortar prisms, after a period of immersion, by scanning electron microscopy confirmed that sulfate attack of blended cement mortars was restricted owing to the reductions in calcium hydroxide and C/S ratio of the C–S–H gel in the blended cement mortar. In comparison to Portland cement mortar, less calcium sulfate and much less ettringite formations were found in the mortars made from blended cement containing RHA. The amounts of calcium sulfate and ettringite found in the blended cement mortar containing fly ash were also small but were slightly more than those of RHA mortar. Up to 40% of Portland cement could be replaced with these pozzolans in making blended cement with good sulfate resistance.     

Investigation of abrasion resistance of cement mortar with different pozzolanic compositions and subjected to sulfated medium

The durability phenomenon for concrete, or cement mortar, has gained attention recently as one of the important mechanical properties. It can be described as concrete’s resistance to the destructive influences of a medium containing acid, sulfate and/or various chemicals and mechanical effects, like abrasion. Most of the studies attempted to improve these individual properties in concrete. However, concrete can be subjected to two or more of these effects simultaneously. In this study, the mortars produced with cement samples having seven different compositions and varied with an air-entraining agent were subjected to the influence of sulfate and abrasive effects simultaneously. In this study, several examples were evaluated using samples cured for six different periods throughout one year. This study is supported by thin section and XRPD investigations, in addition to being subjected to the basic tests, such as compression, flexure and abrasion. If the most important findings obtained from the study are summarized, it is seen that a compact cement matrix is more effective against both sulfate and abrasive effects than mineral additives. The mortars subjected to coupled (sulfate and abrasive) effects show less durability if compared to ones cured in water and later abraded.