Binder Mortar Research Articles

Evaluating the alkali-silica reaction in alkali-activated copper slag mortars

Alkali-Silica Reaction (ASR) in Alkali-Activated Copper Slag (AACS) mortar binder was investigated with reference to Ordinary Portland Cement (OPC) mortar using the accelerated mortar bar method as per ASTM C1260. The ASR expansion in AACS mortar bars were determined with varying alkali content (4, 6, 8 and 10%) and silicate modulus (1.0, 1.25, 1.5) of activator solution. The test results indicated that ASR expansion in OPC mortars was higher than all AACS mortar mixes. The ASR expansion in AACS mortar for alkali content of 4 and 6% was within the threshold value of 0.1% as suggested by ASTM C1260. However, for alkali content of 8 and 10% content, it was higher than threshold value. Higher silicate modulus was marginally effective to lower the ASR formation in AACS mortar mixes. It has been suggested to use alkali content of 6% and silicate modulus of 1.5 for the synthesis of AACS binder with acceptable ASR expansion.

Bond strength performance of ceramic, fly ash and GBFS ternary wastes combined alkali-activated mortars exposed to aggressive environments

• Mortars with high WCP level showed excellent performance against acidic environment. • The bond performance of GBFS replaced mortars at elevated temperatures was enhanced. • Freeze-thawing resistance of mortars revealed inverse relation to the WCP and FA contents. The structural stability, safety and durability performance of the novel repair materials are decided by their interfacial bond strengths in the deteriorated concrete textures. In this view, the bond strength between the alkali activated mortars (AAMs) as the repair materials and normal concrete was studied following the standard ASTM C882 slant shear test. Three types of materials including the tile waste ceramic powder (WCP), fly ash (FA) and ground blast furnace slag (GBFS) were combined to produce these AAM binders. The prepared mortar binders were exposed to the acid attack, elevated temperatures, wet-dry and freeze-thaw cycles to evaluate their bond performance (as repair materials) against such aggressive environments. Various tests were performed to assess the bond strength loss after the exposure to different aggressive environments. The AAM mixes prepared with the high contents of WCP and FA revealed superior performance against the acid attack and elevated temperatures compared to the one contained high amount of GBFS. Meanwhile, the mortars designed with high the amount of GBFS displayed excellent bond strength performance when exposed to the wet-dry and freeze-thaw cycles. It is established that the proposed AAMs with outstanding bond strength performance and durability under aggressive environments are the suitable binders for various civil engineering construction applications.

Pengaruh Penambahan Abu Sekam Padi Terhadap Sifat Fisis dan Mekanis pada Mortar

The research was carried out about the effect of adding rice husk ash to physical and mechanical properties of mortar. Mortar was moulded with three composition comparisons between ordinary portland cement, rice husk ash, and rice stalk fiber. Rice husk ash was burned at temperature of 700 OC for 2 hours, rice stalk fiber was mechanically sliced up to 0.8 mm in size, then mortar molding and maintenance was processed for 28 days. The mortars that had reached the age of 28 days were tested according to the Indonesia National Standard (SNI) including physical properties (water absorption, density), and mechanical properties (compressive strength, modulus of elasticity, modulus of rupture). Characterization of microstructure, morphology and counting all elements on the surface of mortar were processed by using Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopy (SEM-EDS). The results of research that had been carried out, mortar with the most optimum physical and mechanical properties was mortar B with a composition of 65%: 10%: 25%. The results of the characterization using SEM-EDS showed that the surface of mortar B was better with grain diameter (1.4 ± 0.9) µm and the most dominant element in the mortar was element of Ca and Si which functioned as mortar binder and hardener.

Compressive Strength Development of Geopolymer Mortar by Utilization Slag and Fly Ash Mixtures

The paper displays the use of two base solid wastes materials to produce the alkaline-activated binder mortar to reduce the CO2 emission on climate change. The solid materials used in this research were slag and fly-ash to improve the compressive strength (CS) of alkaline activated mortar (AAM). The output AAM of 7 trial mixes were designed with different combinations of slag and fly ash. The mixes combinations were made in ratios of (100:0), (90:10), (80:20), (70:30), (50:50), (25:75), and (0:100), respectively. The combination of 10 M NaOH and Na2SiO3 was used as alkaline activator (AA). The wt. ratio of Na2SiO3 to NaOH = 2.5, and wt. ratio of AA to solid material = 0.52. The samples of AAM were cured at 75°C for 24 h. Among all the 7 trial mixtures, it was found that mixture with a combined ratio of slag:fly ash of 25:75 produce the maximum CS at 28 days of 88.87 MPa. Therefore, the alteration percentage of SiO2 and Al2O3 derived from fly ash in combination with CaO derived from slag contributed to significant CS improvement due to the formation of (N-A-S-H), (C-S-H) and (C-(A)-S-H) gels. The result observed of gel binder formation was confirmed by XRD and FESEM analyses.

Evaluation of Workability and Mechanical Properties of Stone Matrix Asphalt Mixtures Made With and Without Stabilizing Additives

Stone matrix asphalt (SMA) is a gap-graded mixture which is the combination of higher concentration of coarse aggregate and binder mortar. The coarse aggregate skeleton provides the mixture with stone-on-stone contact, giving it strength, while the high binder content mortar adds durability. The mortar is typically composed of fine aggregate, mineral filler, binder, and a stabilizing additive. A stabilizing additive such as cellulose fibers, mineral fibers, or polymers is added to SMA mixtures to prevent draindown of the mastics. In addition, it has the potential of reinforcing and improving the tensile strength of SMA mixtures. This paper presents the findings of performance of SMA mixtures with and without stabilizing additive. Superpave mix design, draindown, fatigue, rutting, workability, and moisture-induced damage properties of the SMA mixtures was evaluated. Three types of stabilizing additives (B, S, and V), one nominal maximum aggregate size (NMAS) 13.0 mm, and an unmodified asphalt binder (VG-30) were used in the study. Results indicate that the addition of stabilizing additive controls binder draindown and mix design properties of SMA mixtures satisfies the IRC SP 79 requirements. Resistance to rutting, fatigue, and moisture-induced damage of SMA with stabilizing additives were higher than SMA mixture without stabilizing additive. Further, SMA mixture without stabilizing additive takes less energy for densification compared with SMA mixture with stabilizing additives.

Mortar analysis of historic buildings damaged by recent earthquakes in Italy

The paper presents an experimental study on mortar samples taken from historic and monumental buildings damaged or collapsed following the seismic events in Central Italy (2016-2017). Sixty-one samples were analysed via a set of diagnostic investigations to characterize the mortar and correlate it with the performance of the masonry. The techniques used were: X-ray diffraction, scanning electron microscopy and microanalysis, differential scanning calorimetry, calcimetry, Fourier-transform infrared spectroscopy, soluble salt analysis by conductimetry and dosage of anionic species by ion chromatography, particle-size analysis, direct shear. Microstructural characterization of the mortars revealed differences in mortar composition depending on their provenance. In particular the samples from Norcia contained large quantities of calcite while in the mortars from Pretare, dolomite was identified. In the case of Amatrice, only a few samples showed crystalline phases and compounds ascribable to binders. These results were largely confirmed by the other chemical and physical analysis performed, and mechanical tests also demonstrated low cohesion. The tests showed that in almost all the samples, poor quality mortars were used, and, in some cases, underachieving binder mortar.

Formation of Friedel’s salt using steel slag and potash mine brine water

The increasing depth and widening scale of potash mines are suggestive of the use of mortars with greater homogeneity and fluidity properties for mine backfills. Results of the experimental investigations discussed herein indicated that the flow property and the later strength of mortars can both be satisfied through the utilization of steel slag (SS) as a binder in potash mines. Paste samples were evaluated in terms of the hydration mechanism for the mixture of brine water (liquid waste from potash mines) and SS, and were found to achieve a compressive strength of 10 and 15 MPa after 28 and 60 curing days, respectively. An analysis carried out for the microstructure of the pastes revealed C–S–H gels and Friedel’s salt being the main hydration products in the system, in which active interpenetration between the substances contributes to the enhancement of the paste’s strength. Impure ions in the system can be fixed to improve the stability of the filler through the formation of Friedel’s salt. Overall, the findings of the present study confirmed that SS exhibits a latent hydraulic behavior and can be used as a binder in mortars for long-distance transportation in potash mines.

Diagonal compression tests on masonry wallets coated with mortars reinforced with glass fibers

Low shear strength of historical masonry constructions is a matter of great concern, especially when these buildings are located in areas of high seismic risk. In recent years this issue has led to many investigations on the development of innovative reinforcement techniques. The application of cement mortar, commonly used in this type of reinforcements, involves a number of material incompatibility problems that could be overcome with the use of lime-based binder mortars. The present article presents the results of an experimental study on solid mock brick wallets reinforced with thin layers of mortar mixed with glass fibers; Diagonal compression tests have been carried out to determine the behaviour of the reinforced masonries, evaluated both in terms of shear strength and deformation capacity. Test results verify that the coating of mortar mixed with fibers is practically as effective as cement mortar regarding shear strength, while they improve deformation capacity.

Effect of nano-SiO2 on early hydration of natural hydraulic lime

Abstract Natural hydraulic lime (NHL) containing both hydraulic and air-hardening contents is of an ideal alternative binder for mortars used in interior decoration, cultural relics repair and historic buildings maintenance. In this study, early hydration and hardening properties of NHL2 with nano-SiO2 (NS) were researched. Hydration exothermic rate firstly decreased within 5 h of hydration and then increased after 5 h of hydration with the increase of NS, which could be attributed to the C2S hydration and the additional pozzolanic reaction between Ca(OH)2 and NS. It is noted that the initial hydration of C2S would be restrained by the increase content of NS in NHL2 due to the delayed exothermic peak occurring time within 5 h of hydration. A decreased porosity of hardened NHL pastes with the increase of NS at each curing age were observed, which might be also caused by the pozzolanic reaction between Ca(OH)2 and NS. Meanwhile, an increased capacity for the pores about 50 nm and decreased capacity for the pores about 1 μm with the increase of NS were also observed. In addition, mechanical level of NHL could be improved from NHL2 to NHL3.5 when more than 2% NS were added.

Ladle Furnace Slag as a Sustainable Binder for Masonry Mortars

Nowadays, the environmental aspect of industrial waste management has got urgent. The reusing of these residues in the civil building is increasing, since all industries have developed a growing concern for the emptying of natural resources. The ladle furnace slag (LDF-slag), a by-product of the secondary refining of steel, is mainly composed of calcium and calcium magnesium silicates. It has the potential to be a sustainable binder for mortars because the composition of LDF-slag is fairly similar to Portland cement (PC) clinker. Thus, this paper aims to improve the cementitious properties of LDF slag. The properties of cement mortars with LDF-slag were investigated including water demand of normal consistency, setting time and compressive strength. The experimental results show that the suitable specific surface area of LDF-slag is 1200 cm2/g (cement replacement amount is 20 wt%) and addition of LDF-slag with different fineness has retarding effect on cement.

Selecting the Most Reliable 14C Dating Material Inside Mortars: the Origin of the Padua Cathedral

ABSTRACTIn order to radiocarbon (14C) date a building, several components of the mortar could be used, such as the mortar binder, the lime lumps, the charcoal particles and shell fragments eventually present among the aggregates. In particular, the mortar binder requires a purification treatment in order to separate it from other sources of carbon, which could change the 14C signature of the binder invalidating the dating process. Here, we present the application of the Cryo2Sonic method to 14C dating of the ancient building structures unearthed during excavation at the Padua Cathedral complex. The dated samples were pretreated by using Cryo2Sonic method and the improved Cryo2Sonic version 2.0, recently developed by introducing additional steps such as centrifugation of the mortar suspension and gravimetric sedimentation of the binder fractions. The Cryo2Sonic version 2.0 relies heavily on the characterization of the mortar and of the purified binder fractions, allowing the isolation of a reliable 14C datable mortar fraction. Through this new method, the 14C dating of different ancient structures excavated next to the Padua Cathedral allow to identify the first religious complex of the city of Padua (3rd–4th centuries AD).

Phase composition and burning history of high-fired medieval gypsum mortars studied by Raman microspectroscopy

The use of high-fired gypsum as binder for masonry and joint mortars or stuccowork in Central Europe in the Early and High Middle Ages was a regional specific as it depended on local gypsum deposits. The calcination technology possible at the time resulted in an assemblage of calcium sulphate phases dehydrated to different degrees and partly thermally damaged accessory minerals of the raw gypsum. Not hydrated clusters of firing products preserved in the binder matrix are a typical feature of such mortars. A novel Raman microspectroscopic approach, providing access to the burning history of individual anhydrite grains, was applied to samples from medieval South Tyrolean stucco decorations and sculptures. Beyond that, Raman microspectroscopy was employed for tracing and visualising pyrometamorphic reactions in natural impurities of the kiln run. In the discussed examples mineral thermometry indicates process temperatures above 800°C: the breakdown of magnesium-rich chlorite led to the formation of forsterite Mg2SiO4, while the thermal decomposition of dolomite CaMg(CO3)2 to periclase MgO and lime CaO yielded – after hydration and carbonation – magnesite MgCO3, CaCO3 polymorphs and magnesian calcite. Hydration of periclase in the mixed gypsum paste containing sulphate ions also resulted in magnesium sulphate hydrates, here identified in the form of hexahydrite MgSO4·6H2O. Lower burning temperatures left the accessory minerals in their pristine form, but can be traced by measuring the spectra of individual anhydrite crystals in grains of firing products and evaluating Raman band widths. Throughout the present study, calcination temperatures ranging from approx. 600°C to 900°C were determined.

Avoiding lime failures

Lime mortar has been used in the construction of traditional buildings in Scotland for centuries. Its use began to diminish from the mid-19th century as mass-produced Portland cements became more widely available. A century later its use as the primary binder in mortar had all but ceased and, within a generation or two, most of the skills and knowledge needed to use lime successfully were lost. Since the lime revival of the late 20th century, and following much research, the benefits of using lime in traditional masonry are becoming increasingly understood. Lime, compared with modern materials such as cement, is much more compatible with the surrounding fabric, especially its ability to allow buildings to ‘breathe’. Despite this revival, however, there is still a belief held by many that lime mortars are difficult to use and susceptible to failure. This paper explains that ‘lime failures’ are much more likely to be caused by failures of workmanship, specification, building detailing and maintenance than the actual material itself, and argues that, provided these largely avoidable factors are considered, there is no reason why any appropriately specified and well-applied lime work should fail on a well-detailed and regularly maintained building.

An Investigation on Mechanical Properties and Damping Behaviour of Hardened Mortar with Rubber Tire Crumbs (RTC)

Masonry wall has been used for ages as a part of non-engineered building structures, due to its ease of manufacture, strength, and stiffness to support gravity loads, but brittle enough to resist earthquake shake. One solution to increase its ductility when the earthquake shake stroked, ductile materials at bed joints that binding the masonries may apply. Mortar is a composite material consisting of sands, cement, and water that is generally used for masonry construction as a binder at bed joints. On the other hand, rubber has been used to isolate vibration of machinery because of its good damping behaviours. Those materials will be mixed and be elaborated to provide a ductile mortar binder at bed joints. This research aims to investigate the mechanical properties and the damping behaviour of hardened mortar with rubber tire crumbs at proportions of 0%, 40%, and 60%. Three types of specimens in forms of mortar cubes of 50x50x50 mm3, tensile specimens and mortar beams of 100x100x500 mm3 were tested to provide strength and damping behaviour. The addition of rubber tire crumbs in the mortar decreased the compressive strength, tensile strength, flexural strength and unit weight. Despite its weakness in the mechanical strengths, the addition of rubber tire crumbs could increase the damping behaviour significantly. This research recommended that mortar containing RTC is still appropriate use for non-structural component although it has low mechanical properties.

Study of new formations of C-S-H in manufactured with glass powder as binder mortar

Mortar and paste with different composition were analyzed with X-ray diffraction and dispersive energy spectrometry (EDS) with coupled Electronic Scanning Microscope (SEM) to study the formation that appear after the setting reaction in the mortar made by using glass powder, with a size of 16μ, as binder. Such analysis shows the occurrence of formations similar to C-S-H gels, but in which, the Ca/Si ratio is lower than for typical C-S-H gels. In addition it was observed that the shape of the gels is slightly different when the samples are preserved in water. These more filamentous formations and the presence of a larger number of Si molecules causes the setting reaction to be maintained for a longer period of time and provide a certain capacity for self-regeneration without external intervention, which makes it suitable for soil stabilization.

Hydrotalcite and Hydrocalumite in Mortar Binders from the Medieval Castle of Portilla (Álava, North Spain): Accurate Mineralogical Control to Achieve More Reliable Chronological Ages

Mortars from different stratigraphic units at Portilla Castle (Alava, North Spain) have been analyzed for mineralogical characterization before radiocarbon dating. The mortar binder at Portilla Castle is composed not only of neoformation calcite but also of double-layered hydroxide (LDH) minerals such as hydrotalcite and hydrocalumite. The mineralogy of several fractions of the binder has been analyzed to determine the granulometric distribution of minerals in the binder. The continuous monitoring of mineralogy during the extraction of different grain size fractions has been performed by using a scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analyses (TGA). Hydrotalcite and hydrocalumite-bearing mortar binders give older ages than expected since they introduce dead carbon into the system.

The effect of alternations in mineral additives (zeolite, bentonite, fly ash) on physico-chemical behavior of Portland cement based binders

Instrumental analyses accompanied by analytical modeling tools were employed to assess physico-chemical changes induced by variations in chemical composition of cementitious composites, i.e. mortar binders. Coal combustion ash was utilized as pozzolanic mineral additive. The binders’ mix-design was supplemented with sorptive clays to prevent migration of toxic elements from fly ash. The experiment was established on the premise of clay’s ion-exchanging ability. Ten binders comprising cement CEM I 42.5 and fly ash, zeolite and/or bentonite additions were prepared in accordance with chemometric experimental design rules. Chemical composition was determined via XRF method. The changes in mineral phases and crystallinity were traced by X-ray diffraction. Hydration mechanisms and thermal behavior were investigated via DTA/TGA. The chemical bonds were identified by FTIR. Morphology of hardened samples was detected by SEM. Mathematical tools employed data sets of instrumental analyses to form a clear differentiation between binders and to assess changes caused by adoption of mineral additives in the mix designs. Sorptive clays showed pozzolanic behavior, thereby causing no incapacitation to the cement hydration mechanism, and classifying as a possible economical resources which can be used in production technology of construction materials to redeem environmental pollution issues of building industry.

Alkali-activated cement-based binder mortars containing phase change materials (PCMs): mechanical properties and cost analysis

Energy efficiency is not only the most cost-effective way to reduce carbon dioxide emissions but also a way to improve competitiveness and create employment. EU aims to achieve nearly zero-energy (public) building (NZEB) by the end of 2018 (2020 for private buildings). This very ambitious target would be more easily fulfilled if high-performance thermal materials like phase change materials-PCMs are to be used. This paper reports experimental results on the properties of fly ash-based alkali-activated binder-AACB mortars in which a minor percentage of aggregates were replaced by PCMs. These include compression strength, at normal temperature and also at high temperatures, flexural strength, density, water absorption, unrestrained shrinkage as well as cost analysis. Several AACB mixtures showed an increase in compressive strength after being exposed to high temperatures. Since PCMs are made of flammable materials and AACB mortars show a much higher stability at high temperature than Portland cement-based mortars this means that AACB mortars are more suitable for PCM incorporation. This is a very important feature because flammable insulation materials were reported to be the cause of the recent Grenfell Tower fire tragedy that made 71 victims.

Comparison Study of Dynamic Elastic Moduli of Cement Mortar and No-cement Slag Based Cementitious Mortar Activated with Calcined Dolomite with Impulse Excitation Technique

This paper presents the comparison of an experimental investigation on compressive strength and dynamic elastic moduli of mortars made of Ordinary Portland Cement (OPC) and ground granulated blast furnace slag (GGBFS) incorporating with calcined dolomite. Dolomite powder calcined at temperature 900°C emerged as a GGBFS activator for producing cementitious mortar binder. In this study, no-cement mortar is made by activating GGBFS with calcined dolomite by a fixed amount of 20 wt%. The compressive strengths and dynamic elastic moduli were measured at 7 and 28 days. Comparing with cement mortar, the compressive strength of no-cement mortar was found about 54.4 and 46.9% lower at ages of 7 and 28 days, respectively. Non-destructive evaluation of the dynamic elastic moduli was investigated by impulse excitation technique (IET). It measures the resonant frequencies of induced vibration signal in the flexural and torsional mode for determining the dynamic Young's modulus and the dynamic shear modulus. The Poisson's ratio was calculated by the dynamic Young's modulus and the dynamic shear modulus relationship. The results showed that the 28-day dynamic Young's and shear moduli of cement mortar were 31.91 and 14.43 GPa, respectively. The dynamic Young's and shear moduli of no-cement mortar were lower by 23.3 and 15.2% than that of cement mortar at the age of 28 days. The obtained results showed that the 28-day Poisson's ratio of no-cement mortar had a wider range between 0.177 and 0.209 than that of cement mortar which ranged from 0.180 to 0.185.

An overview and experimental study on hybrid binders containing date palm ash, fly ash, OPC and activator composites

Global warming due to high greenhouse gasses emission coupled with excessive energy involved in concrete manufacturing process is indeed an alarming threat. To overcome the problem, numerous researches have been carried out to partially replace ordinary Portland cement (OPC) with supplementary cementitious materials (SCMs) that includes agricultural or industrial solid wastes, development of alternative binder known as geopolymer concrete made of one or more pure SCMs using alkaline activators and elevated temperature curing or by development of hybrid cement system that incorporates alkaline activation of OPC-based SCMs. This study aims to: (1) carry out an overview on: CO2 emission by construction industry; alternate cement systems such as partial replacement, geopolymers and most importantly hybrid binders; as well as identification of date palm ash (DPA) as a potential waste material and (2) develop novel hybrid alkali activated binders with a combination of agro-industrial waste to form binary and ternary mortar binders cured under water up to 28-days. The utilized SCMs include fly ash (FA), ground date palm ash (GDPA) i.e. alkali activated or raw DPA i.e. non-activated. These hybrid and non-hybrid binders were compared through physical properties such as strength and workability along with microstructural properties by hydration products and pore volume. X-ray diffraction (XRD) technique was employed to get the mineral composition; phase decomposition of unreacted water, C-S-H/C-A-S-H gel and Ca(OH)2 had been studied by Thermogravimetric analysis (TGA) while nitrogen adsorption test determined surface area of particles as well as pore volume of the paste. The results revealed potential use of DPA as a strong and sustainable material in ternary blend with FA and OPC in conventional non-hybrid binder that can efficiently maximize clinker replacement without energy utilization in alkaline activation.