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Abstract: This paper presents results of an investigation into the potential use of recycling paper mill waste-water to replace mixing water in cement mortar systems for manufacturing concrete masonry products. The physical and mechanical properties of mortar containing various amounts of de-inking waste-water were consequently investigated. A key finding of this study was that replacing mortar mixing water with waste-water significantly improved workability and consistency of cement mortar mixtures. In particular the flow of mortar mixtures increased with increase of waste-water content up to 50% and then levelled off when waste-water content exceeded 50%. Correspondingly, the flow of mortar mix with 100% waste-water replacement at water/cement ratio of 0.50 was found to be equivalent to that of the reference mortar mix with 100% potable water at water/cement ratio of 0.60, indicating potential use of de-inking waste-water as water reducing admixture. The enhanced workability arising from waste-water addition however induced changes in mechanical properties of the hardened material. Compared to reference mortar, replacing 10% and 100% potable water respectively resulted in 19% and 60% reduction of compressive strength, with a corresponding 5% and 16% drop in bulk density, and up to 19% increase in drying shrinkage. Also, water absorption and volume of permeable voids increased with increasing waste-water dosage, albeit marginally. The benefits derived from rheology improvements compared to compromises in mechanical properties due to de-inking waste-water addition strongly indicate clear potential of using de-inking waste-water in production of lightweight cementitious building and masonry elements. [Copyright &y& Elsevier]

Utilizing nano-SiO 2 (NS) to reinforce the old mortar and the weak interfacial transition zone (ITZ) in recycled coarse aggregate (RCA) is a productive approach to enhance the quality of RCA. Throughout this paper, RCA was immersed in NS solutions with different concentrations (2, 5, 10 and 30 wt%). Subsequently, a systematic evaluation of the crushing index and water absorption of the treated NS modified recycled coarse aggregate (SRCA) was conducted. In addition, the calcium hydroxide (CH) content of RCA before and after modification was analyzed by Thermogravimetric and Differential Thermal Analysis (TG-DTA) curves. This study finds that the performance of SRCA modified with 2% concentration achieves comparable modification effects to other concentrations. Additionally, this paper delves into the impact of NS powder on the slump characteristics and compressive strength of concrete. Considering the above research and economic costs, this study adopts 2% concentration of NS for RCA modification and further investigates the stress-strain relationship of NS modified recycled aggregate concrete (SRAC) with various SRCA replacement ratios. Moreover, this paper establishes mesoscopic models of SRAC for various replacement rates and proposes constitutive models corresponding to these rates. The results indicate that when the SRCA replacement rate is within 60%, the stress-strain curve shape of SRAC closely resembles that of natural aggregate concrete (NAC); when the replacement rate exceeds 60%, the descending segment of the SRAC stress-strain curve becomes more precipitous, showing a higher tendency towards fragility in the concrete. ● Nano-SiO 2 can be used to improve the properties of recycled coarse aggregates. ● NS powder affects the slump and compressive strength of recycled concrete. ● As the concentration of NS solution increases, the compressive strength of concrete increases. ● Mesoscopic models of modified recycled concrete were established and constitutive models were proposed. [ABSTRACT FROM AUTHOR]

As building solid waste, the replacement of brick powder for cement is conducive to reducing energy consumption and costs of building material. However, the low reactivity of BP cannot be ignored, as it negatively impacts the performance of mortar. To address this issue, this study incorporates a mixture of plant-based TA (Tannic) with BP into a pre-mixed paste and adds it to cement mortar. The porous structure of the BP facilitates the adhesion and complexation of polyphenol hydroxyl groups, enhancing the dispersion of BP in the cement paste. Moreover, the in-situ formation of nano-sized calcium-based complexes, as evidenced by AFM, XRD, TGA and SEM tests, provide excellent nucleation sites, which regulate cement hydration and enhance the mechanical properties of BP-cement mortar, significantly reducing the proportion of capillary pores and large pores in the mortar. By substituting 15% of cement with TA-modified BP, the compressive strength and flexural strength increased by 49.19% and 5.72%, respectively, and the shrinkage rate was reduced by 73.15%. Thus, this simple and green modification method will provide more inspiration for the efficient utilization of BP in cement-based materials. • The paper will provide more inspiration for the efficient utilization of BP in cement mortar. • The plant-based TA is attached to the surface of BP through complexation-adsorption. • TA-modification improve the dispersibility of BP-cement paste. • TA-modified BP mortar obtained higher strength and lower shrinkage, compared to untreated BP mortar. NOTE: BP mean brick powder. TA mean Tannin acid. [ABSTRACT FROM AUTHOR]

The paper presents an experimental program on the characterisation of the mechanical behaviour of perforated brick masonry (PBM) under uniaxial compression. The study is aimed to provide a better understanding on the compressive strength and elastic behaviour of a kind of masonry hardly dealt with in the literature. The mechanical response of the investigated masonry shows actually two complexities, linked respectively to the perforated nature of the bricks and the asymmetric cross-section of the units. The latter feature is particularly recurrent in exposed brickwork composed of perforated bricks, whenever one of the face shells has a larger thickness than the other one. For this purpose, an experimental campaign was carried out on units and PBM subjected to uniaxial compressive loading. The mechanical response of PBM is investigated to accurately determine the masonry Young's modulus and the compressive strength. Measurements obtained with conventional sensors are compared with those derived from the Digital Image Correlation (DIC) technique. Lastly, the experimental findings in terms of compressive strength and Young's modulus are cross-referenced with the estimations derived from empirical criteria available in Eurocode 6 and ACI 530.1–02. • Characterisation of the compressive response of Perforated Brick Masonry (PBM). • Derivation of compressive strength and Young's Modulus of asymmetric brick PBM. • Novel concept of co-barycentric area to calculate the compressive strength of PBM. •.DIC technique for the computation of Young's Modulus and Poisson's ratio of PBM • Comparison between experimental results and available empirical formulation. [ABSTRACT FROM AUTHOR]

Silica fume (SF) is widely used in the developing of high-performance geopolymer systems. Previous studies have shown that using different types of SF may have different influences on the performance of geopolymers. What are the key factors (affecting the properties of geopolymers) still need to be clarified? This paper investigated the effects of three types of silica fume (SF1− SF3) with various silica contents (98.0%, 94.7% and 53.1%) and particle sizes (D 50 : 3.3 μm, 3.1 μm and 11.8 μm) on the rheology and compressive strength of alkali-activated calcium alumina cement (CAC)/fly ash mortar. The incorporation of SF can significantly increase the plastic viscosity. The increase in plastic viscosity was due to the ball-bearing action of the spherical SF particles, which reduced the friction between the particles under shearing. Replacing 20% of the fly ash with SF1 and SF2 improved the compressive strength of geopolymer mortars while the incorporation of SF3 decreased the compressive strength at the same replacement ratio. Inductively coupled plasma (ICP) spectrometry results indicated that the amorphous silica in the SFs was dissolved in an alkali solution. Activators with high concentrations of monomer and dimmer silicon groups may promote the reaction between precursors and activators. The formation of additional aluminosilicate gels reduced the amount of large capillary pores (500 nm to 1000 nm), leading to improved strength. The incorporation of coarse SF3 introduced extra voids in the mixture, as suggested by calculations of packing density, leading to reduced strength. • From a chemical perspective, SF effect is governed by Si dissolution rate. • From a physical perspective, SF effect is governed by its PSD. • Low SiO 2 content SF increases strength of geopolymers at low dosage. • CPM can optimize mix composition of SF-geopolymer systems. [ABSTRACT FROM AUTHOR]

The porous hydrophilic nature of cement-based material is susceptible to water and corrosive media, severely reducing the durability. In this paper, methyl siloxane-based hydrophobic powder was prepared, and its effect on the physicochemical and anti-corrosion properties of mortar with different water-cement ratios were investigated. The results show that the addition of hydrophobic powder significantly improved the hydrophobic properties of mortars. Especially for the mortars with w/c ratios of 0.2 and 0.4, it showed superhydrophobicity with a water contact angle up to 156.5 ° and 152.3 ° respectively. Lower w/c ratio mortar has a denser microstructure, which reduces the water absorption rate of the mortar, and the hydrophobic powder enhances the hydrophobic effect of low w/c ratio mortar more significantly. The methyl siloxane groups in the hydrophobic powders will bind to the C-S-H gel in the mortar through Si-O bonding, preventing the C-S-H gel connections from forming a continuous network structure. This increased the pore volume and reduced the compressive strength by 14.6%-22.7%, but the total hydration degree was increased, and significant corrosion protection of the steel rebar was demonstrated. [Display omitted] • Super hydrophobicity of mortar was achieved by modification of hydrophobic powder. • Hydrophobic mortar with lower w/c ratio exhibits better anti-corrosion performance. • Methylsiloxane groups combine with C-S-H gel by Si-O enhancing hydrophobic properties of mortar. [ABSTRACT FROM AUTHOR]

The paper presents the results of studies on based the universal morphology of recycled coarse aggregates in reality, an idealized model of recycled coarse aggregates was prepared using stones. Axial compressive strength tests were conducted on prism-shaped specimens of Modeled Recycled Coarse Aggregate Concrete (MRCAC), which were prepared with different old cement mortar coverages and aggregate arrangements. Through comparison with experimental data, the reliability of the finite element analysis model was determined. It was found that the arrangement of MRCA had a significant impact on the failure characteristics and elastic modulus of MRCAC. Thus, different arrangement modes affected the stress distribution within the specimens, resulting in significantly different axial compressive strength. • Studied the influence of aggregate arrangement on the stress characteristics of MRCAC. • Studied the influence of old cement mortar on the mechanical properties of MRCAC under different internal force transmissions. • Revealed the influence characteristics of old mortar on the stress-strain relationship in recycled concrete. [ABSTRACT FROM AUTHOR]

Applying conductive cement-based anode is one of the commonly used methods to achieve uniform electrochemical protection for concrete structures. However, anodic acidification is a critical challenge limiting the effectiveness of electrochemical protection in concrete. Therefore, carbon fiber (CF) and expanded graphite (EG) were used in the current study as conductive materials to reduce the resistivity of cement-based anode by creating a "multi-scale" conductive grid within the anode, while slag powder was employed to enhance the anode resistance to chloride intrusion. This paper investigated the influence of slag powder on the mechanical properties, resistivity, and hydration products of carbon fiber-expanded-graphite conductive mortar (CECM) anodes. The results indicated an inverse relation between the slag powder content and the mechanical properties and resistivity of cement-based anodes. In general, the optimal dosage of slag powder is 20%, at which the compressive strength and resistivity of CECM decrease by 14.8% and 2.75%, respectively. Furthermore, a cubic function relation could be applied to correlate the slag powder content to the mechanical properties and electrical conductivity of the anodes. CF, EG, and slag powder created a composite structure within the hardened cement paste, and formed a multi-scale conductive grid that reduced the cement mortar's resistivity. Through XRD and FT-IR tests, it was found that during the testing period, the pozzolanic effect of slag powder was insufficient to compensate for the loss of strength resulted from the reduced amount of cement clinker. In addition, TGA-DTG results showed that the total amount of C-S-H in Group A increased from 14.31% to 22.86%, while in the Group B this amount increased from 20.74% to 25.94%. The optimal group had an increase from 20.21% to 24.59% in C-S-H content. These results confirm the similar hydration effect of slag powder on EG cement slurry compared to that on ordinary cement. It also indicates that the chloride ion resistance of cement-based anodes can be enhanced through the pozzolanic effect of slag powder, ultimately achieving long-term stable operation of cathodic protection system. • Slag powder is used to modify CECM. • Slag powder particles distributed in multi-scale conductive grids interlaced with EG and CF. • Quadratic surface can reflect the relation of Slag powder content and CECM's compressive strength and resistivity. • Slag powder's "secondary hydration" does not compensate for the strength loss caused by its "dilution effect". [ABSTRACT FROM AUTHOR]

To facilitate the use of geopolymer materials in shotcrete applications, this study presents the development of a geopolymer mortar and explores its flowability and early-stage mechanical properties. Firstly, 15 groups of geopolymer mortar specimens with 3 liquid-binder ratios (0.70, 0.75 and 0.80) and 5 binder-aggregate ratios (0.225, 0.250, 0.275, 0.300 and 0.325) were developed. Secondly, the P-wave velocity, slump, early-age compressive strength and compressive strength were obtained by ultrasonic pulse velocity test, slump test and uniaxial compressive test. Thirdly, discussion on the effect of liquid-binder ratio and binder-aggregate ratio on P-wave velocity, flowability, compressive strength and early-age compressive strength of geopolymer mortar were carried out. Finally, an optimal mix proportions rang of geopolymer mortar materials that meet the requirements of wet shotcrete technology were proposed. The results show that P-wave velocity, slump, early-age compressive strength and compressive strength increase as the increasing of liquid-binder ratio. The slump, compressive strength and P-wave increase as the increasing of binder-aggregate ratio. Moreover, the optimal binder-aggregate ratios were proposed as 0.244 - 0.321, 0.228 - 0.298, and 0.209 - 0.241 for geopolymer mortar with a liquid-binder ratio of 0.70, 0.75 and 0.80, respectively. Geopolymer mortar in these mix proportions achieves compressive strengths ranging from 28.4 MPa to 41.1 MPa after curing for 1 day and 44.2 MPa to 55.4 MPa after curing for 28 days. The mix proportion of geopolymer mortar proposed in this paper can simultaneously meet the standard requirements for mechanical properties and flowability, demonstrating potential for wet shotcrete applications. • A mortar for shotcrete application has been developed using geopolymer as the primary material. • The effects of liquid-binder and binder-aggregate ratios on mortar properties were investigated. • Flowability and early-age mechanical properties of the developed mortar were comprehensively analyzed. • An optimal mix proportion range was proposed for effective use in geopolymer shotcrete applications. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to design a stone filled with cement stabilized macadam (SFCSM) considering shrinkage resistance and easy construction. The corresponding mix proportion design method for SFCSM was proposed. The skeletal coarse aggregates in SFCSM adopt the particle size frequently applied in engineering practice to facilitate construction. In the mix proportion design, the compressive strength test and compaction test were employed to progressively ascertain the optimal blend ratio of coarse aggregates, cement binder, and cement mortar. The vibratory mixing technology (VMT) was introduced to optimize the production of SFCSM. Further, the strength, modulus and shrinkage properties of SFCSM were also evaluated and validated in comparison with the common CSM. The results of the study illustrate that the skeletal coarse aggregates generate the skeletal structure and the role of the filling fine aggregates enhances the stability of the skeletal structure, thus improving the integrity of the mixer. The bonding effect and hydration level of cement in SFCSM is lower than that of the common CSM. The compressive and tensile strength of SFCSM is lower than that of the common CSM. However, the SFCSM has better resistance to dry shrinkage than CSM. The SFCSM as the base is located between the flexible base and the semi-rigid base in the pavement structure design. In addition, the VMT can improve the mixing uniformity of SFCSM and increase its strength. In summary, this study provides inspiration for the shrinkage resistance and practical engineering application of SFCSM. • The mix design method of SFCSM was proposed considering shrinkage resistance and easy construction. • The vibratory mixing technology (VMT) was introduced to optimize the production of SFCSM. • The material properties of SFCSM were evaluated and validated in comparison with ordinary CSM. • The SFCSM has high compressive strength, excellent shrinkage resistance and easy construction. [ABSTRACT FROM AUTHOR]

Cement-based materials with addition of superabsorbent polymer have attracted widespread attention due to their excellent shrinkage resistance and durability. This paper investigated the effects of three internal curing materials with different swelling behavior on mortar related shrinkage, corresponding durability at 50% humidity. The composite microgel with high water retention and controllable water release kept the relative humidity inside the mortar at a high level, and the total shrinkage in the low humidity condition decreased by 126.22 µm/m compared with the reference sample. The correlation analysis showed that the composite microgel reduced the autogenous shrinkage of mortar at the early hydration stage, and significantly alleviated the drying shrinkage with the reduction of internal relative humidity. Composite microgel compacted the microstructure of mortar, and compressive strength is higher than that of microgel modified mortar. At the same time, the role of composite microgel in refining microstructure prevented the water penetration of mortar, and the freeze-thaw resistance of mortar can be better improved by entrained air void of composite microgels. • The influence of SAP with different water absorption behaviors and chemical structures on the shrinkage of mortar has been studied. • The correlation between IRH and shrinkage of mortar was analyzed. • The freeze-thaw resistance, impermeability property of cement mortar at 50% RH can be promoted by composite microgel. [ABSTRACT FROM AUTHOR]

• Mechanical characterization of lime mortars by means of the Drilling Resistance Measuring System (DRMS). • Influence of penetration and rotational speed on drilling results. • Influence of penetration and rotational speed on correlations between UCS and drilling results. • Correlations between the mean of the drilling forces and the depth of cut per revolution. • Comparison between regression models developed using DRMS at a constant and variable depth of cut. The paper investigates the influence of the user-controlled variables on the results of the drilling test (DRMS) performed on lime mortars used for ancient buildings restoration. In particular, the ratio of the penetration and rotational speed (δ), namely the depth of cut per revolution, is considered. The experimental results show a relevant variation in the shapes of the drilling profiles with δ, especially in mortars with lower strengths. The efficacy of the regression models between the uniaxial compressive strength (UCS) and the drilling results changes with the depth of cut. An optimal range of δ to perform the DRMS test is identified for the analyzed mortars. The paper also investigates the possibility of performing the DRMS test according to another procedure poorly studied in the literature to evaluate the UCS of materials. It consists of making more holes in the same material at different values of δ. This method is based on the analytical and experimental results obtained with another scratching technique, the scratch test. The statistical analysis of results shows that the correlation between the mean of the drilling forces and δ can be described by linear regression in a limited range of δ. The slope of the linear regression has a high correlation with UCS. The obtained positive results move to deepen the experimental research on this topic. [ABSTRACT FROM AUTHOR]

The safeguard of existing masonry buildings requires a meticulous characterisation of the component materials (units and mortar) by using in-situ minimally intrusive techniques. This need is especially prominent in the case of heritage buildings in order to minimize their damage and alteration. This paper presents a research on some minor destructive techniques (MDT) for the in-situ evaluation of the mechanical properties of masonry components. In the research, the results derived from MDT were empirically correlated with the compressive strength obtained by using well-known destructive testing (DT) techniques executed in the laboratory. The experimental campaign focused on two different MDT techniques, namely the Pin Penetration Test (PPT) and the Helix screw Pull-out Test (HPT). The PPT is based on the measurement of the depth of penetration of a steel pin. The HPT is based on the measurement of the pull-out load necessary to extract a steel tie inserted into a hole drilled in a brick or in a mortar joint. The experimental campaign also included an evaluation of the Double Punch Test (DPT) by comparison with strength values obtained from mortar specimens prepared and tested following the standard EN 1015–11. The experimental results show a satisfactory agreement between the MDT measurements and the compressive strength obtained with DT. Although both the PPT and HPT are useful for the evaluation of the compressive strength of masonry components, the former exhibits a lower scattering in the experimental measurements. • 541 destructive tests on modern and historical solid clay bricks and mortar joints. • 741 minor destructive tests on solid fired clay bricks and mortar joints. • Compressive strength in mortar using Double Punch Test and EN 1015–11 procedure. • Compressive strength evaluation of specimens using the Pin Penetration Technique. • Compressive strength evaluation of specimens using the Helix screw Pull-out Test. [ABSTRACT FROM AUTHOR]

Graphene has been considerably studied as a reinforcing nanomaterial in cementitious composites to improve their mechanical properties under quasi-static loading. However, there is still lack of knowledge in graphene cementitious composites under high strain rate loadings. This paper reports the reinforcing effect of graphene on the mechanical behaviour of mortar at high strain rates. Different graphene contents were incorporated into the mortar to study their effect on the behaviour of mortar quasi-statically and dynamically. Compressive and split tensile strengths were measured under low and high strain rates using a universal testing machine and split-Hopkinson pressure bar (SHPB), respectively. It was found that adding 0.05% and 0.01% of graphene to the mortar enhanced the dynamic compressive and split tensile strengths up to 30% and 9.5% at 175 s-1 and 2–5 s-1 strain rates, respectively. Moreover, to understand the macroscale mechanical behaviour of the graphene mortar, Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometer (EDS) and Mercury Intrusion Porosimeter (MIP) were employed to explore the morphology, porosity and hydration products of graphene mortar. The results indicated that graphene acted to fill the voids as well as to impede the crack path. • Mechanical properties of graphene mortar were evaluated at high strain rates. • Graphene can enhance the strengths of mortar quasi-statically and dynamically. • Dynamic increase factors were determined for both compression and tension. • Microscopic analysis proved graphene fills the voids and impedes the crack path. [ABSTRACT FROM AUTHOR]

• Crumb rubber was bio-functionalized using polydopamine. • The wettability of crumb rubber was improved by the deposition of polydopamine film. • By using polydopamine-functionalized crumb rubber, the 28d compressive strength of rubberized mortars was improved by 37–68%. • The interface transition zone of rubberized mortars was densified owing to the chelation of polydopamine with Ca2+. This paper explores a biomolecule, dopamine, to functionalize crumb rubber (CR) to enhance the performance of cement mortars made with the CR. This is inspired by marine mussels, which can attach to various substrates underwater using the adhesive protein L-3,4-dihydroxyphenylalanine in its byssus. Dopamine is a mimic of the adhesive protein of mussel. At pH = 8.5, dopamine can spontaneously self-polymerize on the CR surface through the oxidation and the subsequent cross-linking of the catechol structure to form uniform polydopamine (PDA) film. This can enhance the wettability of the CR, leading to higher fluidities of the produced mortar. More importantly, the PDA film can chelate with Ca2+, promoting the formation of a denser interface transition zone between the CR and the cement paste and accelerating the hydration of the cement. As a result, the compressive strengths of the produced mortars were improved by 1–24 % at 3d, 13–52 % at 7d, and 37–68 % at 28d. The capillary water absorptions of mortars were also reduced by 28.6–41.8 %, significantly enhancing the durability of the mortar. [ABSTRACT FROM AUTHOR]

[Display omitted] • The heat welding method can be used as a green, easily available, and economical way to modify the polypropylene (PP) surface. • The fly ash fixed on the surface of PP by heat welding can effectively improve its wettability and pozzolanic activity. • With the addition of F@PP, the microscopic pore structure of the mortar is more compact, and the mechanical properties are greatly enhanced. • The hydration products of the F@PP interface play the role of "micro-pile" in connecting the paste and PP. The weak bonding of plastic/paste caused by the hydrophobicity of plastic surface is a significant bottleneck for the large-scale application of plastics in concrete, which seriously affects the macro and micro structure of plastic concrete. To address this issue, a heat welding modification method was proposed in this paper, which utilized the thermoplastic of the plastic, fly ash was welded to the polypropylene (PP) surface to form a composite aggregate with fly ash properties (F@PP). Experimental results revealed that F@PP exhibited better wettability (contact angle = 75°) and pozzolanic activity compared to unmodified PP. Moreover, compared to PP mortar or F/PP mortar (simply add fly ash to PP mortar), the microscopic interface of F@PP/paste was more compact and its Ca/Si was mostly reduced to less than 2.0. The porosity of F@PP mortar was significantly reduced by 50–57% at 28d and the compressive strength was increased by 11–28% at 3d, 7d, and 28d. These findings highlight the effectiveness of the proposed heat weld method in enhancing the plastic/paste interface and the performance of plastic mortars. [ABSTRACT FROM AUTHOR]

• Including SF into the AAFA mixture decreased workability, whilst STPP increased it. • Including 5–15% SF or/and 4% STPP in AAFA increased compressive strength. • Exposing specimens to outdoor natural weathering showed an adverse effect on their strength. • The adverse effect of weathering could be decreased with including up to 15% SF and 4% STPP. As known, exposure of any material to outdoor natural weathering, which has varied changes in temperature, relative humidity, percentage of sunny/cloudy, precipitation, CO 2 and polluted air may adversely affect its properties compared to its unexposed counterpart cured at the lab. This paper aims to evaluate the effect of one year of outdoor natural weathering exposure on the properties of neat alkali-activated fly ash (AAFA) mortars and those modified with silica fume (SF) and sodium tripolyphosphate (STPP). To increase the resistivity of AAFA mortars to weathering exposure, the FA was partially substituted with 5–20 wt% SF. To further improvement, a fixed ratio of 4% STPP was added to the neat FA mortar specimens and those containing SF. After initial curing, half of the specimens were cured inside the lab for one year (unexposed specimens), whilst the other half were exposed to outdoor natural weathering conditions for the same period. The variations in the compressive strength, mineral composition, hydration products and microstructure were compared. The results showed that exposing specimens to natural weathering has a negative effect on their compressive strength. This negative effect can be mitigated by introducing SF up to 15%. To further reduce this negative effect, 4% STPP can be added. [ABSTRACT FROM AUTHOR]

• The potential of brick waste recycling and its use in aerial lime-based mortars is investigated. • The incorporation of brick dust in lime mortars generated a pozzolanic reaction. • Brick dust improved the compressive strength. • Brick dust increased the hygric and hydric expansion of lime-based mortars. To preserve architectural heritage for future generations, restoration materials such as mortars should be compatible with the historic substrate. Pozzolanic mortars are a compromise solution between Portland cement-based mortars and aerial lime-based mortars. This paper investigates the recycling of brick waste in the Meknes region of Morocco to formulate pozzolanic mortars. Nine different mortars were made using aerial lime, sand and brick dust. They were characterized in terms of shrinkage, color, mechanical and hydric properties. The study revealed that Meknes brick dust exhibits a pozzolanic activity and reduces shrinkage. Moreover, it increases hydric and hygric expansion, enhances mechanical strength and affects the color of mortars. An appropriate recipe for restoration mortars could then be proposed to restore regional architectural heritages, depending on the properties of their historic substrates. [ABSTRACT FROM AUTHOR]

• Cement mortars were cured in frozen sands to mimic the influence of permafrost. • Temperature profiles in calcium sulfoaluminate (CSA) cement mortar were recorded. • Hydration reaction of CSA cement cured at cold temperatures was investigated. • Hydration reaction of CSA cement was fast regardless of cold curing temperatures. • CSA-based mortar achieved fast strength development even at −5 °C and −10 °C. The objective of this paper is to investigate the hydration reaction and strength development of calcium sulfoaluminate (CSA) cement mortar cured in various cold temperatures (i.e., 5 °C, 0 °C, −5 °C and −10 °C). In this study, both CSA cement-based and GU (General Use) cement-based mortar samples were cured in wet sands at temperatures of 5 °C, 0 °C, −5 °C and −10 °C. During the investigation, the temperature profiles in both sands and the centers of mortar samples were recorded. In addition, thermogravimetric analysis (TGA) and unconfined compressive strength (UCS) tests were conducted on the samples at 1, 3, 7 and 28 days. The TGA results showed that the hydration reaction rate of GU cement was slow at cold temperatures and decreased with a drop in the curing temperature. However, the hydration reaction of CSA cement was very fast—it was mostly completed within the first 24 h—regardless of the curing temperatures. The UCS test results indicated that the strength development of CSA-based mortar was much faster than that of GU-based mortar. The CSA-based mortar achieved rapid strength development even cured in frozen sands with temperatures at −5 °C and −10 °C. In conclusion, CSA cement can be substituted for GU cement to accelerate the strength development of cement-based materials constructed in cold temperatures. [ABSTRACT FROM AUTHOR]

• The effects of bentonite on the pore structure of cement mortar were given. • The permeability of mortar could be reduced significantly by bentonite. • The waterproofing process and mechanism of bentonite particles were proposed. The pore structure and permeability of cement-based materials have great influence on the durability of application of this materials. The effects of bentonite on the pore structure and permeability of cement mortar were investigated in this paper. Bentonite, as a swelling potential clay, was added to mortar at content 0, 4 and 8% by weight of cement. The compressive strength, flexural strength, and impermeability pressure were determined for cement mortar with bentonite and compared with plain cement mortar specimens. Test results showed that the addition of 8% bentonite could cause a significant increase of 61.48%, 42.09% and 76.47% for compressive strength, flexural strength, and impermeability pressure, respectively. The enhancement of impermeability is mainly due to the pore structure refinement by the bentonite, which is validated by test results of the Mercury intrusion porosimetry (MIP). Moreover, needle-like and amorphous hydration products grow on the surface or edge of bentonite resulting in more tortuous penetration path to improve the barrier performance of cement mortar. [ABSTRACT FROM AUTHOR]

• This paper first reports the influence of nano-silica on high strength mortar. • Pore system was refined and more disconnected. • Compressive strength and transport properties were improved. • Drying shrinkage was reduced due to the refined microstructure. • The enhancing efficiency was compared in high strength and normal strength mortar. Recent studies have demonstrated the advantages of using nano-silica in building materials such as concrete due to its nano-filler effect as well as the pozzolanic reaction. However, most of the previous findings are based on normal strength cement composites. In this study, a wide range of properties of high performance cement composites are investigated with addition of colloidal nano-silica (CNS) at dosage of 0.5%, 1.0%, 1.5% and 2.0%. Attributed to the pozzolanic reaction of CNS, the microstructures are denser and more homogenous. SEM observation, accelerated hydration rate and reduced Portlandite content verify this beneficial reaction. Hence, the CNS can help produce cement composites with higher mechanical strength and better durability regards to the impermeability to water and chloride ions. Also, it is found that the influence of CNS is more pronounced for composites with lower water-cement ratio at 0.30, in comparison with those at 0.50. [ABSTRACT FROM AUTHOR]

• Rheological and hardened properties, and heat of hydration with nCL, FA and SP are modeled. • Mortar flowability is affected by nCL content, SP dosage, and FA content. • Higher nCL required higher SP for a similar flowability and increased the yield stress and viscosity. • Increasing nCL content affected the compressive strength depending the age. • The optimum nCL content appears to be 1.7% over cement weight. The objective of this research was to optimise the fresh mix properties, rheological parameters, heat of hydration and development of the compressive strength of cement mortars containing nano-clay (nCL) and fly ash (FA). All mixtures were made with water-to-binder ratio (W/B) of 0.40. The replacement of cement by FA was varied from 5% to 20% (by mass of cement), and dosages of superplasticiser (SP) and nCL were varied from 0.6% to 3% (by mass of binder), and 0.5% and 2.5% (by mass of cement), respectively. The fresh mix properties were evaluated by using mini-slump flow, Marsh cone flow time and Lombardi plate cohesion meter, and induced bleeding. Yield stress and viscosity were determined to analyse the effects on rheology. Variations in hydration kinetics were examined through calorimetry tests. Compressive strength was measured and evaluated at different ages up to 28 days. Dosages of nano-clay, fly ash and superplasticiser were the investigated key parameters. Statistical models and isoresponse curves were used to identify significant trends. Prediction models were developed for mini-slump, Marsh cone, Lombardi plate cohesion meter, heat of hydration, induced bleeding, static and dynamic yield stress, plastic viscosity, and compressive strengths at 1 d, 3 d, 7 d, and 28 d as function of nCL, FA, and SP. Optimization of mortar proportioning to fulfil required performance levels in fresh and hardened states was possible by using the predicted models presented in this paper. [ABSTRACT FROM AUTHOR]

• Soils clay content is related with both linear shrinkage and compressive strength. • CEC quantifies the type of clay apart of the amount of clay. • CEC provides strong correlation with compressive strength and linear shrinkage. • Compressive strength and linear shrinkage of earth mortars are linearly correlated. • Flexural to compressive strength ratio is independent of the water content. • Soils with high organic matter content are unsuitable for earth mortars. There is a rapid development of earth construction the last few decades followed by an increased interest in scientific research in this field. One of the issues that have arisen is which soils are suitable for construction and can be designated as construction soils and which are not. Thus, the main objective of this paper is to investigate the relation between physical soil properties and mechanical properties of the dried building material. In this context, the Cation Exchange Capacity (CEC) of the soil is investigated in this research as an innovative tool in soil assessment for earth building. The distinct advantage of CEC is its dependence on clay type and organic matter apart from clay content, which is the soil property most frequently used in soil assessment for building purposes. This study focuses on earth mortars, on which little experimental research has been carried out despite their widespread use. In order to overcome the issues often mentioned in literature of using a certain soil and then generalizing the results, it was decided to use a wide range of soils with different textures from various regions of Greece. So, 26 soils were collected and a total of 49 earth mortar mixes were fabricated in two phases. The soil properties assessed were texture, Atterberg limits, CEC, mineralogy and organic matter content, while the hardened mortar properties assessed were compressive strength, flexural strength, dry density and linear shrinkage. It was found that CEC provides stronger correlation with compressive strength and linear shrinkage than clay content and Plasticity Index. A linear correlation between linear shrinkage and compressive strength was also established. Finally, it is shown that the soils with high organic matter content used in this research, are unsuitable for earth building despite having sufficient compressive strength. [ABSTRACT FROM AUTHOR]

• Characterization of the early age behavior of three NHL mortars. • Continuous elastic-modulus measurement since casting through EMM-ARM. • Comparison of EMM-ARM results with cyclic compression tests on elastic-modulus. • Study of the effect of compaction/sealing methods on mechanical properties. • Relationships among mechanical and physical properties of NHL mortars at early ages. This paper focuses on the mechanical characterization of the early age behavior of three NHL mortars with different water/lime ratios. A vibration-based technique with continuous data recording (Elastic Modulus Measurement through Ambient Response Method - EMM-ARM) was used to measure stiffness of the different mortars that were found to range between 2.5 and 4.1 GPa on day 7. Other physical and mechanical properties such as strength and density were measured as a function of sample preparation protocols –vibrated, compacted, sealed and unsealed. After 7 days, sealed specimens led to 50% lower compressive strength and 25% lower flexural strength compared to unsealed specimens. [ABSTRACT FROM AUTHOR]

• Compressive strength and permeability were compared under low-vacuum and oven drying. • Low-vacuum drying enhances compressive strength more significantly than oven drying. • Oven drying has more obvious deterioration effects on permeability than low-vacuum drying. • Low-vacuum drying process brings a microstructural damage to cement-based materials. The exposure of cement-based materials to low-vacuum environments will result in fast moisture loss, which will cause phase transformation and pore structure changes, as well as variations in mechanical and permeability performances. In this study, a series of experiments were conducted to investigate the effects of various drying conditions (i.e., standard drying, low-vacuum drying, and oven drying conditions) on the properties of cement-based materials, including paste, mortar, and concrete. The tested properties included the mass loss during the exposure to drying conditions, as well as the compressive strength and permeability after the exposure. Results show that the drying rate of cement-based materials was higher under low-vacuum conditions than oven drying for the first two hours, but slower thereafter. Vacuum drying led to a greater enhancement in compressive strength than oven drying, with the most significant effect identified in cement paste. Additionally, oven drying showed more significant deterioration effects on permeability of cement-based materials compared to vacuum drying. The presence of aggregates in concrete has two contrasting effects on the medium permeability: intricated pathways would decrease permeability, but the microcrack formation at the interface during drying would increase permeability. Conventional two-phase material models based on the results of cement paste permeability tests cannot accurately predict the permeability of mortar or concrete after exposure to drying conditions in this study. The paper is expected to provide a basis for the investigation of the mechanical properties and durability evolution of cement-based materials under a low-vacuum environment. [ABSTRACT FROM AUTHOR]

• Different percentages of red mud were added in UHPC. • 20% replacement of red mud was preferable with respect to pumpability and buildability. • Upcycling the red mud in UHPC is an energy-saving and low-cost strategy to address disposal of solid waste. This paper introduces a new application of industrial solid waste red mud to use as a cementitious material in the development of ultra-high performance concrete (UHPC) performances. In addition, utilization of red mud can reduce the environmental impact of red mud landfill. For gaining this aims, UHPC specimens were prepared with different contents of red mud and analyzed the effects of different RM contents on the fluidity, setting time, mechanical properties, durability, drying shrinkage and microstructure of the red mud-based UHPC. The results indicated that fluidity was reduced to 310 mm at 20% red mud level, but it still belongs to enormous fluidity, which is convenient for construction. In addition, it is worth noting that using red mud instead of cement can significantly shorten the setting time, providing a new method for applying the UHPC rapid-repairing process. Red mud-based UHPC mortar prepared with appropriate red mud instead of cement exhibits higher mechanical properties, better durability and reduced drying shrinkage of UHPC during curing. After curing for 28d, the highest compressive strength of UHPC samples containing 20% red mud was 129.5 MPa, the compressive strength of the UHPC samples' sulfate resistance was 136.6 MPa, and the drying shrinkage value was around 414 µm. Moreover, observed information from scanning electron microscopy (SEM) noted that red mud can fill the micro-cracks between particles of cementitious materials, make the structure more compact and form new hydrates. Finally, the two characteristics of low cost and energy consumption further promote the sustainable application of red mud-based UHPC. Therefore, replacing OPC with 20% RM is meaningful to produce a sustainable UHPC mixture and field applications. [ABSTRACT FROM AUTHOR]

• A method to mitigate frost damage of cement mortar at early stage. • Properties of early frozen mortar with different SAP types and dosing. • Mechanism of SAP for improving the performance of early frozen cement mortar. In cold regions, air-entraining agents (AEA) have commonly been utilized to prevent concrete from frost damage. However, the robustness of applying AEA is significantly affected due to the fluctuations in concrete mix proportion, supplementary cementitious material quality, and curing temperature. This paper proposes superabsorbent polymer (SAP) as a promising substitute for AEA, especially for early-age frozen cement mortar. Two types of SAP, acrylic acid and acrylamide (S1) and polyacrylic acid (S2), were incorporated into mortars cured at −10 °C within 7d and 28d, and the mechanical properties, resistivity, pore structure, and microstructure of the mortar were evaluated. The results demonstrated that the incorporation of SAP can improve the mechanical properties of mortar at low temperature. After being cured at −10 °C for 7d, the strength of mortar containing 0.4% SAP was increased by approximately 30% compared to that of reference. The low resistivity exhibited by SAP mortar demonstrated lower free water content during freezing. Additionally, the air content and the spacing factor of the hardened SAP mortar can meet the requirements of frost resistance like AEA. Moreover, adding SAP also promotes the degree of hydration in the later stage. Finally, the present study elucidates the mechanisms through which SAP improves the performance of early frozen cement mortar by reducing the amount of freezable water, introducing air voids, and providing internal curing. [ABSTRACT FROM AUTHOR]

• The materials of stone filled with cement stabilized macadam were reasonably selected and analyzed. • The mix proportion optimization design method of crack-resistance stone filled with cement stabilized macadam was proposed. • The road performance of stone filled with cement stabilized macadam was compared and investigated. • The structural characteristics of stone filled with cement stabilized macadam in pavement structure combination were analyzed. Semi-rigid base asphalt pavement is widely used in China for asphalt pavement construction. However, the presence of reflection cracks remains a significant issue associated with semi-rigid bases. Large Stone Filled with Cement Stabilized Macadam (LSFC) has been identified as an effective solution for inhibiting reflection cracks. However, the construction of LSFC using large particle size coarse aggregates can be challenging. Additionally, the existing mix design process lacks clarity and results in low strength. This paper aims to optimize the design method for anti-cracking Stone Filled with Cement Stabilized Macadam (SFC) by selecting appropriate materials and improving design process. Initially, a mix proportion for SFC is designed using coarse aggregates with common particle sizes employed in engineering applications. The filling proportion of the coarse aggregates, cement dosage, and mass proportion of the cement mortar are gradually determined through compaction and 7-day unconfined compressive strength tests, resulting in the complete mix proportion for SFC. Subsequently, the strength performance, fatigue performance, dry shrinkage performance, and temperature shrinkage performance of SFC are evaluated and compared with common Cement Stabilized Macadam (CSM). The results indicate that while the strength and fatigue properties of SFC are slightly inferior to those of common CSM, it exhibits superior dry shrinkage performance. Moreover, SFC demonstrates better overall crack resistance compared to common CSM, despite having slightly inferior temperature shrinkage performance. [ABSTRACT FROM AUTHOR]

• Non-destructive tests are used to characterise earthen mortars in masonry joints. • Durability and mechanical properties of earth-based mortars are assessed on-site. • Penetrometer, Schmidt hammer, pendulum hammer and scratch tests are evaluated. • Reliability and limitations of NDTs for characterising earth-based mortars are identified. • Six qualitative indicators to compare the performance and feasibility of NDTs are defined. In this paper, the use of non-destructive tests for the mechanical characterisation of earth-based mortars in masonry joints is discussed. Four testing methods, namely the penetrometer, Schmidt hammer, pendulum hammer and scratch test, originally developed for other types of mortar, are reviewed. The methods are applied to the earth-based mortars at the Wupatki Pueblo archaeological site, in Arizona, US. The outcomes of the experimental programme allowed to assess the reliability of the methods and to identify their limitations. Finally, the methods are compared in terms of six qualitative indicators, namely easy-of-use, consistency of results, range and granularity of results, respect towards cultural value, depth of investigation under the visible surface and versatility in application. Overall, the penetrometer test is recommended as the preferable method to characterise the mechanical performance of earth-based mortars. [ABSTRACT FROM AUTHOR]

In the first stage of the paper, the effect of binder content, curing temperature and curing time on the compressive strength of light-weight geopolymer mortar (LWGM) was investigated. The base materials used for LWGM are ground granulated blast furnace slag (GGBFS) and fly ash (FA). The main components of LWGM are lightweight pumice aggregate and alkali activated FA or GGBFS binder. Effectiveness of aforementioned parameters was examined in terms of variation of the compressive strengths of LWGMs. The experiments were performed on LWGM cubes under curing temperatures of 60, 80, 100 and 120 °C with curing period of 2, 6, 8, 24, 48 and 72 h. The alkaline activator is a mix of 12 M NaOH solution with sodium silicate in ratio of 1:2.5. The ratio of alkaline solution to binder was taken as 0.50. 7 binder contents were taken between 650 to 1250 kg/m 3 with 100 kg/m 3 increment. Full factorial experimental program was adopted to observe compressive strength development of LWGMs. Therefore, 336 data samples were obtained. The second stage of the paper is to optimize those experimental parameters through response surface method. Test results indicate that the increment in the binder content increases the compressive strength of LWGM. The strength increases with the increase of curing temperature and curing period of LWGM. The experimental verification indicated a good agreement with optimized results. [ABSTRACT FROM AUTHOR]

• Setting time and engineering properties of BCSA concrete are studied. • Citric acid delays initial set from 15 min to as long as 3.5 h. • Retarding hydration does not affect the mechanical strength. • Design codes accurately predict the modulus of elasticity and tensile strength. This paper discusses the setting time and engineering properties (compressive strength, tensile strength, and modulus of elasticity) of belitic calcium sulfoaluminate (BCSA) cement and concrete. BCSA is an emerging alternative cement known for, among other things, its rapid setting behavior. This has long supported its use as a concrete repair material, but BCSA is also attractive for structural applications. Nevertheless, little information is available on the engineering properties of BCSA concrete. This paper quantifies the influence of mixture parameters on BCSA cement setting times, showing that they can be tightly controlled by altering the dosage of a citric acid retarder. It also quantifies the influence of mixture parameters and curing age on compressive strength, proposing predictive models and showing that retarding the hydration of BCSA does not affect its long-term strength. Finally, this paper measures the modulus of elasticity and tensile strength of BCSA concrete and attempts to predict these properties based on the compressive strength. Results suggest that predictive equations from ACI 318, CSA A23, and Eurocode-2 tend to predict the engineering properties of BCSA cement rather well. Together, these results support the feasibility of integrating BCSA cement into practical concrete construction. [ABSTRACT FROM AUTHOR]

Highlights • Expansion of concrete is enhanced by using an ettringite-based expansive agent. • Expansive concrete shows more significant effects with fly ash than without fly ash. • A high CaO, SO 3 , and free lime fly ash most significantly improves the expansion. • Mechanism of fly ash on the expansion enhancement is described by three hypotheses. • Compressive strength and pore structure of expansive concrete under confinement are enhanced. Abstract This paper evaluates the performances of expansive concrete containing fly ashes. In this study, both standard fly ashes and substandard fly ash are used as a cement replacing material in expansive mortar and concrete. A substandard fly ash which contains high CaO, free lime, and SO 3 contents is used in this study to compare it with high CaO and low CaO fly ashes which are standard fly ashes. Flow, water requirement, and setting times of the expansive mortars are studied together with unconfined and confined compressive strength, length changes, and Young's modulus of expansive concretes. Test results indicate that both free expansion and restrained expansion of the expansive concrete are enhanced by using fly ash, especially by the substandard fly ash. Three hypotheses supporting the mechanism of fly ash on the expansion enhancement of the mixtures are described. The first hypothesis is that expansive mixtures containing fly ash produce more ettringite than that without fly ash. The second hypothesis is that a smaller stiffness leads to a higher expansion of the expansive concrete containing fly ash when compared to that of the expansive concrete without fly ash. The third hypothesis is that fly ash delays the hydration of the expansive additive in the expansive mixtures. These hypotheses are clarified by the test results of XRD-Rietveld analysis, DTG, and Young's modulus. The use of fly ash in the expansive concrete enhances the expansion, the compressive strength, and the pore structure, especially for the expansive concrete under confinement. A mercury intrusion porosimetry (MIP) test of mortar is used to verify the enhanced compressive strength and the pore structure of the expansive concretes. [ABSTRACT FROM AUTHOR]

Highlights • Mortar was made from fresh and aged CAC and its mixtures with additives. • Mortar flowability worsens with cement ageing. • Ageing influences hydration in mortar during its hardening. • Ageing decrease density and compression strength of hardened mortar. • Additives influence the hydration processes and values of technical characteristics of mortar. Abstract This paper presents an on-going study of the influence of the ageing of calcium aluminate cement (CAC) and its mixtures with additives on the properties of fresh and hardened mortar without any deflocculants. DTA, TG, XRD, and SEM methods for hardening products and structure analysis and as well methods for evaluation technical characteristics of mortar, such as the flowability, compressive strength, density, and ultrasonic wave propagation velocity, were used in the work. The results revealed that the ageing of the raw materials in a climatic chamber at 95% relative humidity (RH) and 20 ± 1 °C for 7 days caused a decrease in the flowability of fresh mortar. This characteristic was also influenced by the properties of the additives. The mortar prepared from 14-days-aged raw materials was not flowable. The overall weight loss upon heating and the XRD data indicated a significant increase in the hydration products formed during mortar hardening when the ageing time of the raw materials was extended from 7 to 14 days compared to the amount of hydration products in the hardened mortar prepared from 7-days-aged raw materials. This increase is probably due to the peeling of the carbonated hydration products of cement particles, formed during ageing for 7 days, from the surface when the ageing time is prolonged beyond 7 days, leading to an increased hydration of the cement particles. The ageing of the raw materials has a negative effect on the compressive strength and density of hardened mortar. The formation of hydration products during mortar hardening and the compressive strength and density are affected by the properties of the additives. [ABSTRACT FROM AUTHOR]

Highlights • A mixture of Na 2 CO 3 and NaOH was used as alkaline activator for AAS mortars. • Properties and microstructural characteristics of AAS mortars were investigated. • Characteristics of AAS mortar depend on Na 2 CO 3 -to-NaOH ratios and Na 2 O contents. • Na 2 CO 3 can prolong the setting time and improve compressive strength of AAS mortar. • Both Na 2 CO 3 -to-NaOH ratio and Na 2 O content obviously affected drying shrinkage. Abstract Recently, alkali-activated slag mortars have attracted considerable attention as environmentally friendly materials. The objective of this paper was to explore the influence of an alkaline activator (NaOH or NaOH/Na 2 CO 3 solutions) on the performance of alkali-activated slag (AAS) mortars with pottery sand as fine aggregate. Five Na 2 CO 3 -to-NaOH ratios of 0/100, 20/80, 40/60, 60/40, and 80/20, and three Na 2 O contents of 4%, 6%, and 8%, were used to prepare AAS mortars. The water-to-slag ratio and slag-to-aggregate ratio were kept constant, at 0.38 and 0.8, respectively. The setting time, fluidity, compressive strength, and drying shrinkage were measured. The reaction hydrates were analyzed using microscopy and elemental analysis, while the pore structures were characterized using mercury intrusion porosimetry. The experimental results showed that both the Na 2 CO 3 -to-NaOH ratio and Na 2 O content had a significant effect on the fresh and hardened properties of AAS mortars. A high Na 2 CO 3 -to-NaOH ratio and low Na 2 O content resulted in AAS mortars with longer initial and final setting times. The higher Na 2 CO 3 -to-NaOH ratios led to a higher late compressive strength of AAS mortars, where the 6% Na 2 O samples showed the best performance with Na 2 O contents of 4–8%. In addition, the drying shrinkage behavior of AAS mortars as a function of Na 2 CO 3 -to-NaOH ratio was dependent on the Na 2 O content. Moreover, the compressive strength and drying shrinkage have a direct relationship with the microstructure of AAS mortars. [ABSTRACT FROM AUTHOR]

Highlights • An optimum dosage of MWCNTs could be 0.1 wt% of Portland cement. • The residual strength of all samples containing MWCNT was higher than control samples. • ITZ in the 7-day cured samples displayed more deterioration at elevated temperatures. Abstract In this paper, the effect of curing period on the residual strength of Portland cement mortars containing multi-walled carbon nanotubes (MWCNTs) after 7 and 28 days of wet curing at target temperatures of 20, 200, 400, 600, and 800 °C was investigated. For this purpose, MWCNTs were added at ratios of 0.05, 0.1, and 0.15 wt% of Portland cement. After exposure to elevated temperatures the compressive strength and mass loss were determined and petrographic analysis and X-ray diffraction (XRD) were conducted to analysis the microstructures of the specimens. The results showed that 28-day cured mortar specimens containing MWCNTs had better performance and higher residual strength than that of the ordinary mortars at ambient and high temperatures. The residual strength of 28-day cured mortar specimens containing 0.1 wt% MWCNTs (optimum dosage of MWCNTs) were 9.4, 12.5, 8.5, and 1.5% more than 7-day cured mortar specimens at temperatures of 200, 400, 600, and 800 °C, respectively. Petrography image analysis also indicated that the interfacial transition zone in 7-day cured mortar specimens displayed more deterioration (wider and irregular shape) than 28-day cured mortar specimens at elevated temperature. [ABSTRACT FROM AUTHOR]

Highlights • Gadolinium oxide generates a slight retardation of cement hydration. • Gadolinium oxide increases hydration intensity by aluminate activity acceleration. • Gadolinium oxide optimum content is 5% in relation to the mass of cement. • A substantial content of ulexite hinders almost completely the cement hydration. • Good long term performance were obtained also for specimens with 3% of ulexite. Abstract Gadolinium oxide (Gd 2 O 3) is a potentially effective mineral additive that improves neutron shielding properties of cement based composites. The paper presents the influence of Gd 2 O 3 and ulexite (a boron compound) on Portland cement hydration evaluated by isothermal calorimetry measurements and strength. The progress of hydration was investigated on mortar specimens at water to cement ratio w/c = 0.5 and sand/cement ratio 0.75. The addition of Gd 2 O 3 generates a slight retardation of cement hydration, however it accelerates aluminate activity at the same time. The hydration of cement was completely hindered for mortars containing a substantial content of ulexite. The strength test results show that addition of Gd 2 O 3 to Portland cement mortar mix caused a decrease of early age (3 days) flexural and compressive strength. The optimum content of Gd 2 O 3 in respect to the long term compressive strength and the hydration kinetics was 5% in relation to the mass of cement. Good long term strength was also obtained for specimens with 3% of ulexite. [ABSTRACT FROM AUTHOR]

Highlights • Compression tests on two different standard masonry specimens yielded similar results. • Tests provided new data on clay brick and lime mortar masonry under cyclic loading. • Cyclic tests allowed characterizing the stiffness degradation for increasing strains. • Available analytical and empirical models fit the experimental results satisfactorily. Abstract This research presents an experimental programme on the mechanical characterization of masonry under monotonic and cyclic uniaxial compression. Two different types of standard specimens, running bond walls and stack bond prisms, were built using handmade clay bricks and hydraulic lime mortar. The experimental results are compared and discussed in terms of strength, stiffness and deformability. It was observed that the two specimen types provided very similar results on both strength and stiffness. Cyclic loading tests carried out on a set of samples provided new experimental evidence on the stiffness degradation, loss of load carrying capacity for increasing irreversible compressive strains and energy dissipation. The paper presents eventually a thorough discussion about the comparison between the obtained experimental results with available predictive models for strength, stiffness and fracture energy of masonry under monotonic and cyclic compression loading. [ABSTRACT FROM AUTHOR]

Highlights • Studied fly ash-based geopolymer mortar incorporated with nano-metakaolin. • The mixture of sodium hydroxide and sodium silicate was used as alkaline activator. • Significant increase in compressive strength at 4% replacement of NMK was observed. • SEM (EDS) analysis of fly ash and fly ash-based geopolymer mortar was also observed. Abstract Geopolymer mortar is a novel binder material that exhibits the same properties as of cement. However, being a waste material geopolymer binder has an edge over cement binder because of environmental safety. This paper elucidates the fluctuations in compressive strength and microstructure of fly ash based geopolymer mortar using 14 M molar concentrations of alkali activator solution along with different replacement levels of nano-metakaolin (0%, 2%, 4%, 6%, 8% and 10% of fly ash). The mixture of sodium hydroxide (NaOH) and sodium silicate (Na 2 SiO 3) in the ratio of 1:2.5 was used as an alkaline activator solution. All the specimens were cured for 24 h temperature curing and tested after 3,7,14 and 28 days of ambient curing followed to temperature curing. Geopolymer mortar with 4% nano-metakaolin shows appreciable improvement in compressive strength at all curing ages. The phase composition and microstructure of fly ash based geopolymer incorporated with nano-metakaolin were investigated using scanning electron microscope (SEM) technique. [ABSTRACT FROM AUTHOR]

In this study, a 3D DEM model containing a mortar-bolt interface subjected to shearing was established in the context of the simplified rock bolt model (SRBM) proposed in a companion paper. The DEM model was calibrated against a series of laboratory experiments to reproduce the mechanical characteristics of a cement mortar with a uniaxial compressive strength of 30 MPa. The DEM simulation has led to a detailed observation and an in-depth understanding of the mode II progressive debonding of the mortar-bolt interface and subsequent mortar rupture (due to mechanical interlocking). In addition, the effects of particle size of mortar and profile configurations of rebar bolts (i.e., different rib spacings and rib heights) on simulation results were discussed. The numerical findings in the study were validated against laboratory measurements and a broad agreement was observed. [ABSTRACT FROM AUTHOR]

Depending on its hydraulic activity, the use of Granulated Blast Furnace Slag (GBFS) in cementitious materials contributes to improve their durability performances. In this paper, a low reactive Granulated Blast Furnace Slag with is used in modifying mortar composition. Some durability properties of mixes containing 0, 30 and 50% of slag as substitution to OPC are studied. Diffusion and conduction of chlorides at long term are analyzed with different initial wet curing periods. Microstructure of mortars after 360 days of diffusion is observed by means of Mercury Intrusion Porosimetry. The oxygen permeability is analysed at 90 and 360 days of wet curing. The results indicate good performances to chloride diffusion of the mortars with GBFS, especially for a prolonged wet curing. Moreover, the GBFS are inefficient for oxygen permeability at 90 days but they however allow a decreasing over long term. [ABSTRACT FROM AUTHOR]

In this paper, an empirical study aimed at preventing the coalescence of fine entrained air bubbles in the fresh mortar of self-compacting concrete (SCC) containing fly ash is reported. The time of addition of the air-entraining agent (AEA) during mixing is also investigated. Various types of AEA are also studied. In implementing the experiment, mortar flowability is assumed to affect the coalescence of fine air bubbles. The air size distribution of the air-entrained SCC mortar in the fresh state is determined by an Air Void Analyser (AVA). Changes in the air size distribution over a 120 min period are analysed to evaluate bubble coalescence. The results suggest that the use of fly ash in the SCC can result in a higher degree of coalescence of the fine air bubbles. The various types of AEA resulted in air bubbles with different degrees of coalescence. Further, adding the AEA to the mix after the superplasticiser (SP) inhibits the coalescence of air bubbles. Evidently, the degree of coalescence of air bubbles can be reduced by careful selection of the AEA and the mixing procedure. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel PCM was prepared by encapsulating fatty acids in polyurethane foam. • Geopolymer mortars based on phosphate by-products with incorporated PU@PCM were studied experimentally. • New potential composite materials were developed to improve the energy efficiency of buildings. • The incorporation of PU@PCM resulted in a slight decrease in the compressive strength of the geopolymer mortars. • The compressive strength of the rich PU@PCM-geopolymer mortar is still sufficiently high for building applications. The development of eco-innovative building materials has become increasingly important due to their unique characteristics and environmental benefits. One such technology, the inclusion of phase change materials (PCMs), is highly effective in reducing energy consumption and increasing the thermal inertia of buildings. This study focuses on a novel PCM that encapsulates fatty acids in polyurethane foam and is incorporated into a geopolymer mortar matrix developed from phosphate industry by-products. The paper first outlines the structural and thermal properties of the developed geopolymer mortar (GP) and the form-stable phase change material (PU@PCM). It then investigates the influence of PU@PCM on the mechanical performance of the geopolymer mortar by conducting compressive tests, and the thermal performance by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and thermal conductivity (LFA) measurements. Results indicate that the prepared geopolymer mortar consists of a continuous three-dimensional network and that the developed PU@PCM provides a suitable operating temperature range (10–22 °C) for designing energy-efficient buildings, with good energy storage capacity (ΔH f = 164 J/g). Although the addition of PU@PCM resulted in a loss of compressive strength, the developed composites still meet the mechanical requirements for concrete applications, with the PU@PCM-rich composite reaching 29.5 MPa. Furthermore, the study of thermal performance shows that the inclusion of PU@PCM significantly improves the heat capacity and slightly reduces the thermal conductivity of the composites, with the PU@PCM-rich composite exhibiting 1.1 J/g.°C and 0.84 W/m.°C, respectively. Finally, cyclic DSC tests demonstrate that the composites are thermally stable even after 20 heating/cooling cycles. Overall, the geopolymer mortar with the highest PU@PCM content shows promise as a potential candidate for developing sustainable and energy-efficient buildings in the future. The developed material offers a combination of good thermal performance and acceptable mechanical strength, which are essential features for practical applications in construction. [ABSTRACT FROM AUTHOR]

• CWP was used as a binder replacement in cement and lime mortars. • Results were compared in terms of mechanical, durability and microscale properties. • For cement mortars, the optimal substitution rate was 10–20%. • In cement mortars, the mechanical properties were unaffected up to 50% replacement. • In lime mortars, the mechanical properties increased up to 70% replacement. Ordinary Portland cement (OPC) is responsible for 8% of worldwide carbon emissions and the construction industry is in need of alternatives to minimise its impact. Waste products from foundries and furnaces are prime candidates as they can be high in reactive properties. This paper reports on the results of an experimental investigation into the effect of ceramic waste powder (CWP) as a binder substitute in cement and lime-based masonry mortars. As part of a comprehensive experimental investigation, standard cement and lime specimens were made with replacement rates of 0–60% and 0–80%, respectively, and moist cured for up to 90 days. The examined properties include compressive strength, tensile strength, dry bulk density and permeable voids, drying shrinkage, and pH. Based on the obtained results, the compressive and tensile strengths of cement mortars containing CWP not only experienced no significant adverse effect up to 50% replacement, but also increased at the substitution percentages of 10–20%. For the hydrated lime mortars, the compressive and tensile strengths were continuously enhanced up to 70% replacement of lime with CWP. These results were supported by the outcomes of the scanning electron microscopy (SEM) images and X-ray diffraction (XRD) analyses. These findings can introduce a useful application of CWP as a sustainable binder replacement in construction leading to reducing the carbon footprint of construction materials and the adverse environmental impact of CWP disposal in landfills. [ABSTRACT FROM AUTHOR]

This paper is aimed to study a ground granulated blast furnace slag activated with alkali powder to manufacture Portland-free mortars for conservation, restoration and retrofitting of existing masonry buildings and concrete structures. Activator/precursor represents the key parameter – not only for elasto-mechanical performances – influencing the rheological properties and the shrinkage: the higher the activator dosage, the higher the consistency class and shrinkage. Moreover, elastic modulus of slag-based mortars is lower than that of OPC-mortars at the same strength class. AAMs seem to be more promising for a sustainable future in construction since the GER and GWP are reduced by about 80% compared with traditional Portland cement mortars with the same compressive strength. [ABSTRACT FROM AUTHOR]

In order to solve the problem existing in the utilization of fine recycled aggregates from crushed bricks (RCBA), the replacement of natural fine aggregate (NA) by RCBA to produce a new green recycled mortar is an important technology to develop renewable resource products and realize waste resources recycling. In this paper, in order to deeply understand the mechanism of RCBA, macroscopic and microscopic tests are carried out to study the influence of RCBA with different replacement ratios, particle sizes and additional water contents on the flowability, compressive strength and flexural strength of mortar. And the physical properties, chemical composition, mineral composition and microscopic morphology of RCBA are analyzed. The results show that the porous structure of the waste clay bricks together with the secondary mechanical crushing treatment result in the decline of the physical properties of RCBA. The fully additional water content in RCBA is beneficial to improve the flowability of mortar, but the partially additional water content in RCBA has an adverse impact. In addition, the RCBA with partially additional water content and particle size of 0–5 mm is beneficial to the improvement of mortar strength. However, the RCBA with fully additional water content and particle size of 0.15–5 mm is detrimental to the development of mortar strength. The microscopic test indicates the rough surface and pozzolanic activity of RCBA produce relatively stable and dense interfacial transition zone between the RCBA and cement paste. [ABSTRACT FROM AUTHOR]

This paper reports an experimental study that aimed to define the parameters for the mix design of structural lightweight self-compacting concrete (LWSCC) incorporating coarse lightweight expanded clay aggregates and natural sand. The starting point was the methodology proposed by Nepomuceno et al. (2014) for normal density self-compacting concrete (SCC). The necessary modifications were evaluated and new correlations obtained to support the definition of the mix design parameters. It was concluded that the coarse aggregates reference curve, as well as the mortar phase flow properties proposed by Nepomuceno et al. (2012) for the SCC, are adequate to produce LWSCC. Correlations to quantify the volume of coarse lightweight aggregates (Vg) are presented. It was shown that Vg depends on the mortar phase proportions, concrete workability properties, concrete compressive strength and concrete oven-dry density. The analysis of dynamic and static segregation shows a satisfatory performance with a uniform distribution of lightweight aggregates. [ABSTRACT FROM AUTHOR]

This paper presents a study on alkali activated cement (AAC) mortar produced with waste soda-lime-silica glass. The waste glass was used simultaneously as a precursor and fine aggregates in the alkali activated fly ash-slag mortar. The influences of waste glass in cullet and powder forms on workability, compressive and flexural strengths, fire resistance of the AAC mortar were investigated. The experimental results showed that the workability was gradually increased as the replacement level of natural sand by glass cullet was increased, and it was significantly improved with decreasing aggregates-to-binder ratios. The mechanical properties data indicated that the compressive strength was reduced as the glass cullet content increased. However, for the flexural strength, the optimum percentage of glass cullet replacement was 50%. Due to the low reactivity, a reduction in strength was observed when the glass powder was used to replace the fly ash and slag. Nevertheless, in terms of fire resistance, the incorporation of glass cullet could improve the resistance of the AAC to high temperature exposures (800 °C). In particular, the AAC mortar prepared with the glass powder as a precursor exhibited remarkable resistance to high temperature. The use of waste glass in AAC material was feasible from the mechanical properties and fire resistance points of view. [ABSTRACT FROM AUTHOR]

Nowadays, since thermal insulation, enhanced mechanical properties and durability have become extremely important in construction elements. The concept of developing new economical and eco-friendly mortars that incorporate various types of wastes as a partial replacement of cement and sand has gained a great interest. In this paper, sand was partially substituted (20, 40 and 60% by weight) with either glass powder or mussel shells powder with water to cement ratio of 0.6. Mortar’s thermal conductivity, volumetric heat capacity, compressive strength and resistance to chloride ingress were evaluated and compared with those of ordinary mortar. Glass powder and mussel shells can improve thermal insulation by reducing their thermal conductivity. An optimum ratio 40% by weight of glass powder improves compressive strength of mortars. Besides, High glass powder content can significantly improve mortars resistance to chloride penetration. [ABSTRACT FROM AUTHOR]

This paper reports a study of the colour, compressive strength and workability of mortar when cement is partly replaced by sewage sludge ash (SSA). In the study, an iron rich SSA was dry milled into six different fractions. The results showed that the colour, compressive strength and workability parallel to one another gradually changed when the particle sizes of the SSA decreased. The milling of the SSA altered the performance of mortars to the extent that the compressive strength and workability were comparable to the performance of ordinary mortar. At the same time, the colour also changed from grey to a reddish colour. As the change in colour may be of importance for application, it is suggested to include colour as experimental parameter in future work. [ABSTRACT FROM AUTHOR]

As well known the confinement is an effective intervention for increasing the compressive strength of an axially loaded column. During the decades, different materials have been adopted in order to provide confining action, such as steel, reinforced concrete and latest high-performance fibers. Fibers application resulted a powerful solution mainly because of the high ratio between mechanical properties and weight and the absence of electrochemical corrosion. On the other hand, fiber needs to be impregnated with a matrix in order to be applied around the column and to exert an effective confining pressure. Polymers manifest excellent performance in this role, but unfavorable result if breathability of the structural element is a key-issue as well as reversibility and compatibility of the new materials with the existing substrates (e.g. in historical masonry construction). In this scenario, the interest in non-polymeric matrix has been increased in the last years, as the use of a cement/lime based mortar. In the present paper, a state-of-art regarding experimental programs on concrete and masonry samples confined by Fiber Reinforced Mortar (FRM) and subjected to pure compressive test is preliminary reported. Therefore, a multiple linear regression analysis was implemented in order to identify the possible influence of the interaction between the properties of the matrix and those of the fibers on the effectiveness of the confining pressure. Two new analytical formulations were assessed and discussed in the present study (the first related to concrete and the second related to masonry columns), evidencing the importance of taking into account the characteristics of the confining mortar besides those of fibers. A deep comparison (experimental vs. predicted) of the proposed formulae with Design-Oriented-Models (DOM) from the literature was also provided in terms of accuracy, precision and correlation. Finally, simplified relationships are also furnished and addressed to a possible contribution for design guidelines on the topic. [ABSTRACT FROM AUTHOR]