Influence of Ultra Fine Glass Powder on the Properties and Microstructure of Mortars

This study focuses on the effect of ultrafine waste glass powder on cement strength,gas permeability and pore structure.Varying contents were considered,with particle sizes ranging from 2 to 20μm.Moreover,alkali activation was considered to ameliorate the reactivity and cementitious properties,which were assessed by using scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS),and specific surface area pore size distribution analysis.According to the results,without the addition of alkali activators,the performance of glass powder mortar decreases as the amount of glass powder increases,affecting various aspects such as strength and resistance to gas permeability.Only 5%glass powder mortar demonstrated a compressive strength at 60 days higher than that of the control group.However,adding alkali activator(CaO)during hydration ameliorated the hydration environment,increased the alkalinity of the composite system,activated the reactivity of glass powder,and enhanced the interaction of glass powder and pozzolanic reaction.In general,compared to ordinary cement mortar,alkali-activated glass powder mortar produces more hydration products,showcases elevated density,and exhibits improved gas resistance.Furthermore,alkali-activated glass powder mortar demonstrates an improvement in performance across various aspects as the content increases.At a substitution rate of 15%,the glass powder mortar reaches its optimal levels of strength and resistance to gas permeability,with a compressive strength increase ranging from 28.4%to 34%,and a gas permeation rate reduction between 51.8%and 66.7%.

Influence of the Steel-making Dust on High Temperature and Fatigue Performance of Asphalt Mortars

To research the possibility of steel-making dust as a kind of mineral filler in asphalt mixture, two steel-making dusts and one ordinary mineral filler were adopted. The specific density, specific surface area, fineness modulus and mineralogy component of the dusts were tested. Scanning electron microscopy(SEM) was carried out to research the microstructure of the dusts; dynamic shear rheological(DSR) test and time sweep test were used to research the high temperature and fatigue performance of asphalt mortars containing steel-making dust. The experimental results indicate that, compared with ordinary mineral filler, steel-making dusts have more active ingredients, difference surface characteristics and micro-structure. Furthermore, the high temperature and fatigue performance of steel-making dusts corresponding asphalt mortars are superior to those of reference group. Therefore, the steel-making dust would be an alternative to the ordinary mineral filler to improve the performance of asphalt mortars and reduce the harm of the dusts to the environment at the same time.

The Properties of Cement Mortars Modified by Emulsified Epoxy and Micro-fine Slag

The epoxy resin polymer cement mortars with excellent performances were made up through modifying ordinary Portland cement with emulsified epoxy and micro fine slag.The microstructure of the epoxy resin polymer cement materials was studied and their hydration and hardening characteristics were discussed by means of modern analysis measures such as SEM,XRD and Hg intrusion micromeritics.The experimental results indicate that the series effects of water reducing,density,pozzolanicity,filling and solidification crosslinking through the action together with epoxy organism and micro fine slag endowed cement based materials with perfect performances.The main hydration products in the system are C S H gel and hydrated calcium aluminate.At later age,AFt can be in existence,and no Ca(OH) 2 is found.When epoxy resin is solidified,the organism is in a network structure.In the micro pore structure of hydrated cement with modified epoxy and fine slag,big harmful pores were fewer,more harmless abundant micro pores were and the possible pore radius was smaller than that of ordinary Portland cement.

Effect of graphene on mechanical properties of cement mortars

Functionalized graphene nano-sheets(FGN) of 0.01%-0.05%(mass fraction) were added to produce FGN-cement composites in the form of mortars. Flow properties, mechanical properties and microstructure of the cementitious material were then investigated. The results indicate that the addition of FGN decreases the fluidity slightly and improves mechanical properties of cement-based composites significantly. The highest strength is obtained with FGN content of 0.02% where the flexural strength and compressive strength at 28 days are 12.917 MPa and 52.42 MPa, respectively. Besides, scanning electron micrographs show that FGN can regulate formation of massive compact cross-linking structures and thermo gravimetric analysis indicates that FGN can accelerate the hydration reaction to increase the function of the composite effectively.

Synthesis and Application of Sodium-carboxymethylcellulose Type Superplasticizer in Cement Mortars

The polymeric admixture, the sodium-carboxymethylcellulose(CMC)/poly sodium p-styrene sulfonate(PSS)/poly vinyl acetate(PVAc) was synthesized and applied in cement mortars. The polymer was tested by FTIR and SEM, and the results indicate that the ideal molecular structure is synthesized. The effect of addition amount of polymeric admixture and water-to-cement ratio on mechanical properties of cement mortars was studied. The polymer-modified mortars under the optimum water cement ratio and optimum polymer cement ratio, the flexural strength of polymer-modified mortars are 1.45, 1.21, and 1.17 times higher than the plain cement mortar at age of 3, 7, and 28 d, respectively.The compressive strength of polymer-modified mortars at age of 3, 7, and 28 d are 1.55, 1.40, and 1.2941 times higher than that of the plain cement mortar,respectively. Scanning electron microscope(SEM), FTIR and TG were used to analyze the effect of polymer emulsion on cement hydration reaction. The results show that the polymer emulsion can promote the hydration reaction of cement.

Optimization of Blended Mortars Using Steel Slag Sand

A new kind of mortar made of ground granulated blast-furnace slag （GGBFS）, gypsum, clinker and steel slag sand （〈4.75 mm） was developed. The ratio of steel slag sand to GGBFS was 1 ： 1 and the amount of gypsum was 4% by weight while the dosage of clinker ranged from 0% to 24%. The optimization formulation of such mortar was studied. The content of steel slag sand should be less than 50% according to the volume stability of blended mortar, and the dosage of clinker is about 10% based on the strength development. Besides strength, the hydration heat, pore structure and micro pattern of blended mortar were also determined. The experimental results show the application of steel slag sand may reduce the dosage of cement clinker and increase the content of industrial waste product such as GGBFS, and the clinker is also a better admixture for blended mortar using steel slag sand.

Dynamic Mechanical Characterizations and Road Performances of Flame Retardant Asphalt Mortars and Concretes

To research the dynamic mechanical properties and road performances of flame retardant asphalt mortars and mixtures, four different asphalt mortars/mixtures were prepared: a reference group and three asphalt mortars/mixtures containing composite flame retardant materials(M-FRs) of different proportions. Temperature sweep, frequency sweep, repeated creep test, force ductility test and bending beam rheological test were carried out to research the dynamic mechanical properties of asphalt mortars containing M-FRs; wheeltracking test, low-temperature bending test and freeze-thaw split test were used to study the road performances of asphalt mixtures containing M-FRs. The results show that high-temperature performances of the three flame retardant asphalt mortars improve greatly, while low-temperature cracking resistances decline. Both hightemperature performances and water stabilities of asphalt mixtures containing M-FRs are quite good and exceed the specification requirements. However, their low-temperature performances decline in different degrees. In summary, besides their good flame retardancy, the flame retardant asphalt mortars and mixtures also exhibit acceptable road performance.

Study of the Mechanical Behaviour of Mortars Modified with Rice Husk Ash

The purpose of this work is to study the influence of Rice Husk Ash (RHA) on the mechanical strength of mortars. For this purpose, ash was produced by calcining rice husk at 680°C for 5 hours to produce reactive pozzolan. The chemical and mineralogical composition studied by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and X-Ray Diffraction (XRD) showed that this ash is rich in amorphous silica. The ash presents a good pozzolanic activity with a lime fixation rate of 100% after only 7 days of treatment. The addition of RHA to cement contributes to the formation of calcium silicate hydrate (CSH) and calcium aluminate hydrate of C3ASH6 type. The presence of RHA in the mortars improves their mechanical strength. This improvement is due to the filler effect of RHA and to formation of the CSH resulting from the pozzolanic reactivity between the amorphous silica of the RHA and the portlandite released by hydration of the cement.

Study of Durability of Siliceous Sand Based Mortars in Togo, and of Binder of Plastic Bags of the Kind “Voltic”: Hydrocarbons’ Effect

The present study aims at environmental protection through the use of plastic wastes in the production of mortar. The behavior of siliceous sand-based mortars from Togo and binders of plastic bags of the kind “voltic” is analyzed. Mortar samples from a mixture of siliceous sand and binder of plastic bags are prepared and subjected to physical and mechanical tests after immersion in the hydrocarbon from 0 hour to 504 hours. The result demonstrates that hydrocarbons have no influence on mechanical properties of mortars for an immersion time below 3 hours. Between 3 hours and 24 hours the presence of hydrocarbon increases their physical and mechanical properties. After 24 hours mortars generally lose the mechanical properties of around 8% to 24% due to the loss of viscosity and cohesiveness of the binder caused by the fuel. The behavior in the face of hydrocarbons shows that the material can be used in the surface of roads by carefully avoiding that hydrocarbons remain on the roads for a period of time beyond 24 hours.

Variables Affecting the pH Measurement of Cement Mortars

A quantitative pH measuring method has been used to measure the pH of pure and blended cement mortars.The blended cement mortars incorporating supplementary cementitious materials(SCMs)such as fly ash(FA),ground granulated ballast furnace slag(GGBFS)and palm oil fuel ash(POFA)were used.Moreover,different variables affecting the pH values of CBMs such as temperature of sample solution,quantity of sample powder,dilution ratio and temporary storage of sample during pH measuring process have been studied for all cement mortars.

Chloride-binding capacity of mortars composed of marine sand subjected to external chloride penetration

In order to explore the interactional relations of internal chloride and external chloride-binding amongst the cementitious materials,the chloride-binding capacity of mortars composed of marine sand(MS)or washed marine sand(WMS)were investigated.Results indicate that more external chloride can penetrate and diff use more deeply into the WMS mortar than that in the MS mortar.This phenomenon suggests that the external chloride migration resistance due to WMS is lower than that caused by MS.The distribution trends of the bound chloride content in the two types of mortars are the same at diff erent immersion times.However,a signifi cantly decreased area of the bound chloride content exists at the border of the external penetration area(EPA)and the external unaff ected area(EUA)at the immersion ages of 3 and 7 d,and then it disappears gradually with immersion time.The WMS mortar can bind more external chloride,whereas the MS mortar can bind more internal chloride,at diff erent immersion times.The distributions of bound chloride conversion rate in the EPAs of the two types of mortars diff er across immersion times.The distribution fi rstly decreases,and then it increases at the immersion ages of 3 and 7 d.The distribution was from increase,then decreases,and increase again at the immersion ages of 28 and 56 d.The bound chloride conversion rate in the WMS mortar is aff ected more greatly by external chloride penetration than that in the MS mortar.The amounts of the Friedel’s salt tend to increase with prolonged immersion time.Finally,the penetration of external chloride can increase the amount of fi ne capillary pores smaller than 100 nm in the WMSmortar exposed for 56 d in the chloride salt solution(WMS-E)specimen.

Using Colloidal Nano Silica to Enhance the Performance of Cementitious Mortars

Nanomaterials have been widely used in the past few decades due to their proven capacity to enhance the mechanical properties of materials. While many studies have sought to improve the understanding of how nanomaterials affect the behavior of concrete, additional research is needed in order to achieve the full potential of the material, especially in the presence of supplementary cementitious materials. This study aims to investigate the mechanical properties of cement mortars incorporating both nano-silica (NS) and class F fly ash (FA). Furthermore, mercury intrusion porosimetry (MIP) was performed to study its effect on pore characteristics, and thermogravimetric analysis (TGA) was performed to measure the calcium hydroxide Ca(OH)2 content in the mixtures. It was found that using nano-silica enhances the compressive strength, reduces the total porosity and accelerates the pozzolanic reaction.

Mathematical models for properties of mortars with admixtures and recycled fine aggregates from demolished concretes

In order to expand the engineering application of recycle aggregate mortars （RAM） with aggregates from demolished concretes, the models for the properties of RAM and the replacement rate of these recycled fine aggregates were proposed. First, different kinds of mathematical models for the basic properties （compressive strength, water retention rate, and consistency loss） of RAM with two kinds of admixtures, thickening powders （TP） and self-made powdery admixtures （SSCT） designed for RAM, and the replacement rates were established, while the average relative errors and relative standard errors of these models were calculated. Additionally, the models and their error analyses for the curves of drying shrinkage and curing time of RAM ＋ SSCT at different replacement rates were put forward. The results show that polynomial functions should be used to calculate the basic properties of RAM ＋ TP and RAM ＋ SSCT at different replacement rates. In addition, polynonfial functions are the most optimal models for the sharp shrinkage sections in the curves of drying shrinkage-curing time of RAM ＋ SSCT, while exponential functions should be used as the models for the slow shrinkage sections and steady shrinkage sections.

Corrosion Behavior of Reinforcement Steel Embedded in Cement Mortars Using Different Protection Systems

Although reinforced concrete structures are able to withstand towards a variety of adverse environmental conditions, reinforcement corrosion could lead to concrete structure deterioration. The present study examines four different ways of using corrosion inhibitors against pitting corrosion. In particular, it was investigated the chloride penetration resistance of reinforced cement mortars using corrosion inhibitor applied in three different ways. The corrosion behavior of the specimens was evaluated by electrochemical methods such as Linear Polarization Resistance and Halfcell Potential Resistance. In addition, the mass loss of steel rebars against time of partially immersion in sodium chloride (NaCl) solution was carried out in the lab. The experimental results showed that the corrosion systems examined in the study provide anticorrosion protection on steel rebars against chlorides comparing with the reference group.

Optimization of the Traction Resistance of Hydraulic Mortars Based on Togo Sands

The purpose of this study is to analyze the behavior of mortars from the sands of Togo in order to optimize their traction resistance. 3660 4 cm × 4 cm × 16 cm test tubes of mortars are prepared from the sands of 20 extraction sites in Togo with variations in water and cement while keeping the water-cement ratio constant (E/C = 0.5). It emerges a quadratically increasing evolution of resistance in flexural at 28 days of age (σf) for cement-sand (C/S) and water-sand (E/S) ratios varying respectively by the interval [0.0370, 0.3580] to [0.1977, 0.5120] and [0.0185, 0.1792] to [0.0988, 0.2605]. The resistances become stationary beyond these values (σf ≈ 3.4750 MPa to 7.9010 MPa). For structures whose resistance in traction is desired, three formulas of sand mortars from Togo are therefore defined: rich mortars (C/S > 0.5120 and E/S > 0.2605), lean (C/S < 0.0370 and E/S < 0.0185) and normal (0.0370 < C/S < 0.5120 and 0.0185 < E/S < 0.2605).

Optimum Level of Replacement Slag in OPC-Slag Mortars

The present paper reports the testing of 14 OPC-slag mortars and 2 controls OPC and slag mortars. The main aim is to determine the optimum level of replacement slag for achievement to the highest early strength with reasonable flow. Variable was the level of GGBFS in the binder. In this experimental work, two types of sands were used that are： silica and mining sands. It is determined that the optimum level of replacement slag is 40% and use of silica sand in OPC is preferable to mining sand and reversely, use of mining sand is preferred in GG100 to silica sand. All mortars had W/B and S/B 0.33 and 2.25, respectively.

Mechanism and Preventive Technology of the Thaumasite Form of Sulfate Attack on Cement Mortars

The deterioration mechanism of thaumasite towards cement or concrete structure and the deterioration pattern of in-situ construction caused by the formation of thaumasite were studied in this paper. To improve the TSA (the thaumasite form of sulfate attack) resistance, the cement type, water to cement ratios, the mineral admixture and the circumstance factors should be taken into consideration.

Mechanism of Expansion of Mortars with Limestone Filler due to External Sulfate Attack

The mechanism of expansion of mortars and pastes with limestone filler due to external sulfate attack was studied.Mortars and pastes made at water to solid ratios of 0.45, 0.5, 0.6 from Portland Cement (OPC) with 0%, 20% or 30% (w/w) limestone filler (LF) were cured in a 95±1% RH moist room at 20±1℃for 14 or 28 days. They subsequently were immersed in 5% Na2SO4(0.35 M) solution at ambient temperature (1-35℃). The expansion of the specimens was measured every month, and selected samples were examined by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicate that mortars with 20% LF show larger expansion than that of OPC mortars at up to 9 months of exposure, and the amount of gypsum in both mortars and pastes with LF is much more than that in mortars and pastes without LF. Therefore, it is reasonable to conclude that the formation of massive gypsum leads to the lager expansion of the mortars and pastes containing 20% LF. These behaviors may be explained by the changes in hydration products due to the addition of LF.

Strength Development of Cement-Slag Mortars

In this experimental work, three groups of cement-slag mortars namely OPC, OPC-slag, and slag mortars were made. All were cured in both water and air under room temperature. Strength development was studied up to 90 days. The mortars were prepared using 0%, 50%, and 100% replacement with slag. The sensitivity for all groups was obtained against the curing regime with the highest being attributed to the slag mortars. The highest and lowest strengths at early ages were attributed to OPC and slag mortars when both were cured in water. The highest and lowest strengths were attributed to OPC-slag and slag mortars at later ages, respectively. The highest strengths for OPC-slag, OPC, and slag mortars were as 72.0, 64.0, and 21.5 MPa at 90 days when the specimens cured in water, respectively. Strength loss was observed for all groups at later ages when cured in air under room temperature. The maximum and minimum, of about 8.0% and 1.3%, occurred at 56 and 90 days for slag and OPC-slag mortars, respectively.

Corrosion Protection of CNTs/CNFs Modified Cement Mortars

The aim of this study is to examine the performance of nano additives in two different sets of mortar specimens armed with reinforcing steel rebars. In particular, three sets of reinforced concrete cylinders with additives of 0.1% wt of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have been exposed to a solution of 3.5% NaCl, and further examined for the impact of nano-modification on corrosion performance. The anti-corrosive performance of these additives was investigated through linear polarization technique (LPR), mass loss and mercury porosimetry technique (MIP). From the investigation results, it is found that the addition of CNTs/CNFs causes lower steel corrosion, whereas the pore structure of concrete with CNTs/CNFs can significantly reduce the mass loss rate and the relative permeability.