Water Absorption Research Articles

The role of wheat flour minor components in predicting water absorption

Water absorption in wheat flour is a crucial parameter for optimizing bread-making processes. The determinants of wheat flour water absorption were investigated through the analysis of 28 compositional and technological properties of 150 wheats grown in France. A multiple linear regression approach was used to predict the water absorption, selecting the best model through successive examination of Bayesian Information Criterion, Variance Inflation Factor and minimizing the total number of variables.A model with protein content, soluble starch, damaged starch and specific viscosity from water extractable arabinoxylans was identified as the best trade-off between the number of variables and the predictive performances among all possible models. Soluble Starch, varying between 1.11 and 6.21 g/100 g flour a new criterion measured alongside water-extractable arabinoxylans content, varying between 0.26 and 0.86 g/100 g flour, shows significant potential to predict water absorption compared to damaged starch.

Preparation and flame retardant properties of new mining fireproof gel

Coal spontaneous combustion (CSC) brings great danger to mine safety. Although traditional colloidal fire-fighting materials can reside at high fire source points, their permeability and fluidity are poor, and such materials focus on their water absorption, but pay less attention to water retention and resistance, which makes their fire-fighting effect not good. This paper proposed a new type of mining fire prevention colloid material (CPS-α), which had good solid water gel formation, viscosity, fluidity, and blocking properties to compensate for traditional colloids' shortcomings. According to the single-factor experiment, polymeric polyacrylamide (PAM) as the base material, sodium carboxymethyl cellulose (CMC) as the coagulant, modified starch (SS) as the flame retardant and reduced ascorbic acid were determined. After gel treatment, compared with raw coal, the critical temperature point of spontaneous combustion of coal was increased by about 28 °C, the time to reach the critical temperature point was delayed by 190s, and the characteristic temperature points were significantly increased; the overlap area of coal and water increases by about 20 % after adding gel, and the change slope of the diffusion coefficient of water decreases, which indicated that CPS-α had good flame retardant effect.

Effect and mechanisms of surface treatment using nano titanium dioxide on the permeability of cementitious materials

Corrosive media typically penetrate the interior of cementitious materials through porous structures, causing corrosive damage. Strengthening the surface structure of the substrate is an effective method for enhancing the durability performance of such a material. This study investigates the effects of different concentrations of a nano titanium dioxide suspension (NTS) used for the surface treatment of cement specimens after 24 h of molding and the influence of this treatment on the impermeability of the substrate surface. The results indicate that at 28 d of hydration, water absorption by the 1% NTS-treated specimens decreases by 45%, and the resistance to chloride-ion penetration increases by 32.7% with respect to that of the control group. Furthermore, results of the microscopic tests indicate that when NTS surface treatment is conducted on hardened cementitious materials, NTS provides nucleation sites to enhance the degree of cement hydration, fill minuscule voids, promote the dispersed growth of hydration products, optimize the surface pore structure, and increase the density of the microstructure, thereby improving the impermeability of the substrate surface. This study is expected to provide innovative ideas for the future utilization of nanomaterials for strengthening surface structures and enhancing the durability performances of cementitious materials.

Production of high-strength eco-conscious ceramics exclusively from municipal solid waste

This research investigated the application of municipal solid waste incineration fly ash (MSWIFA), municipal solid waste incineration bottom ash (MSWIBA), and construction waste residue (CWR) as raw materials for the comprehensive conversion into municipal solid waste ceramics employing the SiO2-Al2O3-CaO-MgO (8wt.%) phase diagram. This study aimed to evaluate the influence of the addition of MSWIFA and sintering temperature on important ceramics properties, including linear shrinkage, water absorption, sintering range, and flexural strength. Additionally, relationships were established among these physical parameters using Pearson's correlation coefficient. The thermal behavior of the mixture was analyzed through automatic slag melting point tester and TG-DSC techniques. Furthermore, characterization of the crystalline phase transition and microstructure of sintered samples was performed by XRD, Factsage, and SEM. The results showed that both the addition of MSWIFA and the sintering temperature significantly influenced the crystal phase composition of the sintered ceramics. Moreover, the addition of MSWIFA and the sintering temperature had a significant influence on the pore structure of the ceramics. These ceramics exhibited exceptional properties, such as the extremely low water absorption rate of 0.08% and the remarkable flexural strength of 124.78 MPa. Ceramics performance indicators were far higher than the requirements of China's national standard GB/T4100-2015. The sintering range had the capability to attain 30 °C, guaranteeing the feasibility of practical manufacturing processes. Furthermore, leaching concentration tests conducted on additive-free ceramic samples reveal a low risk of heavy metal contamination, as the heavy metals were effectively solidified within the crystalline and amorphous phases of the ceramics. The comprehensive utilization of MSWIFA, MSWIBA, and CWR for the production of fully solid waste ceramics not only yields cost reduction benefits but also promotes efficient utilization, presenting a feasible and highly promising approach to sustainable waste management.

Solar water evaporation-induced long-term locomotion of self-propelled soft robots

Self-propelled soft robots have attracted extensive attention because of their unique application in exploring dangerous and complex environments that are unsuitable for human beings. However, these soft robots require cyclical chemical stimulation or external power and have short locomotion times, which limits their practical applications. It remains challenging to create self-propelled soft robots exhibiting long-term locomotion. Here, we couple an active hydrogel with a solar absorbing coating to realize self-propelled soft robots with long-term locomotion. The active hydrogel can move freely on the water surface by continuously establishing asymmetric surface tension through dynamic wetting. The sunlight absorbers promote water evaporation inside the self-propelled soft robot to delay or even disrupt the swelling equilibrium of the hydrogel, thus establishing dynamic balance between water absorption and evaporation. In this way, the locomotion time of this self-propelled soft robot under constant light irradiation equivalent to 1 sun (1kW/m2) is 6.5 times higher than that of active hydrogel reported previously. Owing to the enhanced locomotion time through solar water evaporation water, this self-propelled soft robot is expected to be applied to oil pollution exploration, cargo transportation, and debris cleaning in small water areas.

Sustainable and Cleaner Production of a Porous Geopolymer Support Based on Metakaolin and Natural Calcium Oxide

The field of engineering today, mainly civil engineering, given population growth and urbanization, is experiencing permanent changes, thereby implying the use of a sustainable and, above all, less polluting alternative. The present work deals with the study of the effects of the calcium-phosphate network in the geopolymeric matrix in an acidic environment (P2O5/H2O = 0.06 and 0.12) using metakaolin (MK) and calcined oyster shells (COs). Kaolin (K) and oyster shells (respectively heat treated at 700 and 900 °C), metakaolins and geopolymers (produced at room temperature according to the molar ratios P2O5/H2O = 0.06 and 0.12) have were characterized using chemical, thermal (TGA/DSC), mineralogical (XRD) analyzes and Fourier Transform Infrared Spectroscopic Analysis (FTIR). In addition, the physical and mechanical properties of the geopolymers (specimen appearance, setting time, linear shrinkage, water absorption and compressive strength) were determined. It was found that kaolin and oyster shells contain mostly kaolinite and calcium oxide respectively. However, the mineralogical analysis of MK shows a dome reflecting the presence of an amorphous phase favourable to geopolymerisation. From these results, we note that: the appearance of the geopolymer specimens is accentuated by the efflorescence and the presence of pores. The setting times of the pastes for the two solutions decreased with the addition of COs powder, due to the presence of calcium phosphate crystalline phases within the materials such as monetite and brushite which tend to accelerate network consolidation. Linear shrinkage also decreased with the addition of COs powder. On the other hand, with the addition of COs, the water absorption increase at the ratio 0.06 while they decrease at 0.12, due to the presence of pore within the geopolymers. As for the compressive strengths, they decrease with the addition of the COs powder, due to the weakening of the geopolymeric network by monetite and brushite. In conclusion, at high concentrations (P2O5/H2O = 0.12), COs (responsible for the formation of monetite and brushite in acidic environments) powder acts as a porogen. Given the presence of pores in the materials and their relatively high resistance compared to other studies, these materials could be used in engineering as sensors, insulators (thermal, electrical and acoustic).

H2 and CO purification by CO2 removal from syngas coupling membrane module and water-absorption unit: An economic analysis

Hydrogen represents today a necessary alternative to fossil fuels to limit the greenhouse gas effect due to the CO2 emissions. In this work, a plant configuration able to get pure H2 and concentrated CO (about 94%) from a syngas mixture is proposed and simulated by coupling a selective membrane unit and a water absorption column. In addition, an economic assessment on the simulated plant is carried out to estimate the feasibility of this process in terms of economic potential, studying its dependence on several parameters, such as raw material price, membrane cost, membrane feed pressure, column temperature and feed flow rate.Separation performance is improved by the higher feed membrane pressure (greater H2 recovery and CO purity), whereas the increment of the column temperature especially affects the CO recovery. Hence, the economic potential presents a maximum with pressure and temperature (e.g., about 246ꞏ103 $/y at 40 bar of feed membrane pressure and about 282ꞏ103 $/y at 50 °C of column temperature), due to the balance between the higher compression/solvent cost and the increment of H2 or CO recovery. In addition, the simulated plant shows a positive economic potential in a wide range of syngas price (e.g., from 0.126 to 0.25 $/Nm3), being also not affected significantly by the cost of the palladium-based membrane module. A bigger plant size (i.e., feed flow rate from 10 to 100 kmol/h) can lead to a twelve times greater economic potential (from about 242ꞏ103 to about 2954ꞏ103 $/y at 30 bar), reducing the H2 purification cost and making the net present value positive.

A comparison of physical, morphological, and mechanical properties of bio‐polyester hybrid nanocomposites

AbstractIt is imperative to improve the physical, morphological, and mechanical properties of biodegradable polymers like polylactic acid (PLA), poly (butylene adipate‐co‐terephthalate) (PBAT), and polycaprolactone (PCL) in order to employ them on a larger scale. The development of hybrid nanocomposite materials using nano inclusions can improve desired qualities. Here we introduced an interactive nano reinforcement approach to improve the properties by combining graphene oxide (GO) and carboxyl functionalized MWCNT (f‐MWCNT), to provide for their chemical bonding for synergic reinforcement. A constant filler 2 wt.% was added to the biopolyesters by melt blending process and examined the different physical properties like water absorption, intrinsic viscosity, and hardness. To completely evaluate the functionalization of the nanofillers, wide‐angle X‐ray diffraction (WAXD), Raman spectroscopy and Fourier transform infrared radiation (FTIR) analyses were used. The paired nanoparticles and polymer matrix appear to mix well together, as shown by electron microscopy, which also reveals good dispersion and the creation of a reinforcing network microstructure across the matrix layer. A thorough analysis of the results showed that effective stress transmission, delaying the start of faults and generating microcracks, and dissipating additional mechanical energy all contributed to efficient hybrid network formation, which improved the mechanical properties of hybrid filler nanocomposites except some nanocomposites. These findings offer a viable technique for chemically altering biodegradable polymers, like PLA, PBAT, and PCL for use in biomedical, wastewater management, and agricultural applications.

Tasar silk fiber waste reinforced polylactic acid composite: physical, mechanical, and sliding wear characterization

Incorporating natural industrial waste as a reinforcement for the development of sustainable composite is now being extensively practiced to eliminate harmful synthetic fiber. This study exhaustively evaluated the potential of tasar silk fiber waste (TSFW) as a reinforcing agent in a polylactic acid (PLA) matrix to optimize the physical, mechanical, and wear properties. Therefore, PLA-based biocomposites with varying TSFW proportions (0, 2, 4, 6, 8, and 10 by weight) are manufactured and then evaluated for physical (density, voids, water absorption), mechanical (tensile, flexural, impact, and hardness), and sliding wear properties. Results suggested that water uptake of PLA composites increases with the addition of TSFW and becomes saturated after nine days of immersion. The TSFW reinforcement at 8 wt.% in PLA yields 32% and 22% improvement in tensile strength (66.2 MPa) and flexural strength (103.2 MPa), respectively. A remarkable improvement was observed in the impact strength at similar reinforcement (8 wt.%) of TSFW with the observed value of 27.90 kJ/m2. A continuous increase in hardness was obtained by including TSFW in PLA, with the highest value of 86 Shore D recorded for 10 wt.% TSFW added biocomposite. The specific wear rate of all samples increased, but the incorporation of TSFW significantly reduced the same. Microscopic examination suggests that microploughing, microcutting and groove formations were the main mechanism of material removal. After examining the results, it is recommended that TSFW be used in bidirectional mat form for further enhancement of mechanical properties and improved bonding between fiber and matrix.

Enhancing mechanical performance and water resistance of Careya-Banana fiber epoxy hybrid composites through PLA coating and alkali treatment

The ongoing research focuses on exploring the potential of Careya arborea (CA) fiber, banana fiber (BF), and epoxy composites as sustainable alternatives to petroleum-based products and synthetic fibers. The aim is to enhance the interfacial bonding and overall performance of these composites while reducing reliance on traditional materials. The study investigates the adhesion between CA fiber, BF (both chemically treated), and epoxy with polylactic acid (PLA) coating. Specifically, it examined how the PLA coating affects the mechanical properties, including tensile strength, flexural strength, impact resistance, and water absorption behavior, of the fabricated composites. Mechanical characterizations of the composite specimens are conducted following ASTM standards. The PLA-coated and NaOH-treated specimens significantly improved their tensile strength (20.56%) and flexural strength (16.7%), and significantly reduced their water absorption capacity (by 47.6%) compared to the untreated ones. These findings highlight the promise of using treated natural fibers and PLA coatings to create more sustainable and high-performance composite materials.

Improvement of the mechanical properties of the cement mortar by the incorporation of silica particles with low and high surface area

In recent years, nanoaprticules with different sizes have been incorporated in the cement mortar in order to improve their mechanical characteristics. The present work focuses onto the influence of the silica nanoparticles (SiO2) with low and high surface area over the stability and mechanical properties of the cement mortar. The quantities of nanosilica added into the cement mortar to ameliorate their mechanical characteristics vary from 0.5 % to 1.5 %wt. The obtained material after the incorporation of the SiO2 nanoparticles have been characterized by several techniques such as TG, DTG, DSC and their morphologies were determined by using SEM analysis. The workability, water absorption, compressive and flexural strengths of these materials have also been evaluated. The results obtained show that the introduction of the SiO2 nanoparticles into the cement mortar has been greatly improved their compressive and flexural strengths, and the specimens incorporated by nanosilica with high surface area are found more effective than those containing the silica nanoparticles with low surface area, suggesting that the specific surface play a crucial role in the improvement of their mechanical properties. The results show also that the appropriate dosage of silica nanoparticles in the cement mortar to have a maximum enhancement of their mechanical properties was found around 1.5 wt% by weight of cement for the nanosilica with high surface area.

Poly(ethylene oxide)bis-carbonate - based hydrophilic non-isocyanate polyhydroxyurethanes: Polymer-water interactions and glass transition behavior

Hydrogen bonding, glass transition, water absorption, and plasticization are studied as a function of hydrogen bond donor concentration in the chain of a non-isocyanate polyhydroxyurethane system synthesized by solvent-free aminolysis of a poly(ethylene oxide) (PEO) based cyclic carbonate. The concentration of hydrogen bond donors is controlled by varying the ratio of diaminobutane (DAB) and triethylenetetramine (TETA) in the amine component. Introduction of secondary amino groups enhances hydrogen bonding and as a result slows down dynamics, as evidenced by an increase in glass transition temperature. Hydroxyurethane groups are the primary hydration sites despite the hydrophilicity of the polyether. Secondary amino groups act as secondary hydration sites which further increases water sorption capacity. The Couchman-Karasz model describes excellently the dependence of glass transition temperature on composition in both dry and hydrated systems.

Biocomposite Materials from Natural Rubber/Polylactic Acid Blends Reinforced Rubberwood Sawdust for Producing Children's Toys

Biocomposite materials are prepared by blending natural rubber (NR) and polylactic acid (PLA) reinforced with rubberwood sawdust (RWS). This study aimed to investigate the effects of PLA grade, NR/PLA blend ratio, and RWS content on flexure, tension, hardness, and water absorption characteristics, including thermal stability. The RWS content significantly affected the physical and mechanical properties of the biocomposite materials. The increasing additions of RWS from 30 to 50 wt% increased the mechanical modulus, hardness, and water absorption but decreased the thermal stability of the biocomposites. Polymer blended with an NR/PLA ratio of 30/70 reinforced with 30 wt% RWS exhibited the highest mechanical strength, whereas a blend ratio of 40/60 was found to be reinforced with 40 wt% RWS. The polymer matrix blended with a higher PLA content resulted in superior biocomposite properties. Thus, the biocomposites with an NR/PLA ratio of 30/70 had better properties than those with a ratio of 40/60. Further, biocomposites with PLA grade of low melt flow rate (6 g/10 min) improved their properties more than that of a high melt flow rate (80 g/10 min). Therefore, the appropriate formulation of biocomposites for producing children's toys is a blend ratio of 30/70 with 2003D PLA grade of low melt flow rate and reinforcement with 30 wt% RWS. The tensile, flexural, and compressive forces of a toy boat prototype were 70.08, 104.9, and 124.8 N, respectively, while the specified standard is 69.0, 69.0, and 113.5 N, respectively, thus meeting the requirements of the American Society for Testing and Materials F963.

Towards Sustainable Construction: Strength and Microstructural Assessment of Dillenia Suffruticosa and Acacia Auriculiformis Leaf Ash as Novel Supplementary Cementitious Materials

Researchers are exploring local, recycled, and waste materials for construction to address environmental concerns. Concrete heavily depends on cement, contributing to energy consumption and greenhouse gas emissions. Substituting cement with alternatives like recycled materials can cut energy use and minimize the environmental impact on concrete production. This research represents the first investigation into using Dillenia Suffruticosa (DS) and Acacia Auriculiformis (AA) leaf ash as sustainable alternatives to cement in producing eco-friendly mortar, an area that other researchers have not previously explored. The study aims to investigate using DS and AA leaf ash as sustainable alternatives to cement in mortar production. In this study, the incorporation of DS and AA leaf ash as a partial replacement for cement was systematically varied in increments of 5%, ranging from 5% to 40% of the total mortar volume. The ash was systematically incorporated into the mortar in increments of 5%, ranging from 5% to 40% of the total mortar volume. The study further conducted a comprehensive investigation into the physical properties of the mortar, including consistency, bulk density, dry density, water absorption, and flow characteristics, alongside an analysis of its compressive strength. Microstructural behaviour was assessed using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and thermogravimetric analysis to provide a comprehensive analysis. Results indicate that the enhancement in compressive strength of DS ash specimens, relative to AA ash, ranged from 1.32% to 24.49% at 7 days, 5.81% to 16.86% at 14 days, and 1.87% to 11.91% at 28 days. Furthermore, the highest enhancement in compressive strength is observed with a composition containing 10% DS ash and 5% AA ash content, underscoring the superior performance of DS ash compared to AA ash. The mineralogical characteristics of DS and AA leaf ashes illustrate their effectiveness as supplementary cementitious materials in sustainable construction. The significant advantages of using DS and AA leaf ash as a cement substitute are environmental sustainability, innovative materials use, and contribution to sustainable construction.

Evaluation of baffle-plate bioreactor coupling with adsorption column for the remediation of aquaculture wastewater

In this study, a baffle-plate bioreactor was designed and coupled with an adsorption column for the remediation of aquaculture wastewater. Specifically, baffle-plate was installed in the bioreactor to improve the removal of carbon (C) and nitrogen (N), while the ceramsite prepared from steel slag and river sediment was filled into the column for the adsorptive removal of phosphorus (P). To evaluate the performance of the bioreactor, the operation conditions (e.g., hydraulic retention time (HRT) and C/N ratio) were tentatively optimized. Under the optimal operation conditions, the effects of sulfamethoxazole (SMX) on the performance of the bioreactor and the microbial community were comprehensively investigated. Satisfactorily, the removal rates of NH4+-N, NO3−-N and permanganate index (IMn) were all above 88 % before adding SMX. Moreover, neither IMn nor NH4+-N was influenced by the SMX shock, whereas the NO3−-N removal was significantly deteriorated owing to the inhibitory effect of SMX on denitrifying bacteria. As revealed by the analysis of microbial communities, the microbial abundance obviously increased in the aerobic (e.g., Azohydromonas and Chitinophagaceae) and anaerobic (e.g., Alkaliflexus) zone as compared to the initially inoculated sludge. Nevertheless, the abundance of most denitrifying genera decreased after adding SMX, leading to the inefficient denitrification. In addition, the ceramsite prepared under the optimum conditions had great void fraction (55.2 %) and water absorbency (29.5 %). The average removal rate of phosphorus by the adsorption column was 71.6 %. Overall, these findings may shed new lights into the coupling of bioreactor and adsorption column for the remediation of aquaculture wastewater.

Experimental and numerical study on single ice crystal growth of deionized water and 0.9% NaCl solution under static magnetic field

Ice crystal growth of water and its aqueous solution is the key phenomenon in food freezing. In this research, the effect of static magnetic field (SMF) on single ice crystal growth was investigated combing experiment and simulation. The ice crystal growth of water and NaCl-water solution under 0 - 15 mT SMF intensities were studied. The UV absorbance of water after SMF treatment was measured. Phase field model was adopted to simulate the ice crystal growth. The results show that SMF significantly inhibited the growth rate, while had little effect on the morphology and growth direction of ice crystals. SMF had a certain enhancement effect on the UV absorbance of deionized water. The proposed model could well simulate the ice crystal growth under different SMF intensities. Combining experimental and simulation results, it can be inferred that SMF inhibits ice crystal growth by enhancing original hydrogen bonds and reducing free energy.

Characterisation of a novel sustainable wood-geopolymer masonry units

Masonry units have been fundamental to building construction for over 6,000 years, making them one of the oldest and most widely used materials in the industry. However, their production using ordinary Portland cement has significant environmental impacts, including high carbon dioxide emissions and depletion of natural resources. This highlights the need for more sustainable alternatives. One promising option is the use of recycled aggregates from construction and demolition waste in masonry unit manufacturing. This paper investigates the use of chipped waste timber as aggregates, bound together with geopolymer cement made from industrial by-products such as fly ash and slag. The result is a new type of masonry units, referred to as wood geopolymer masonry units (WGMUs), which were evaluated against established standards and compared with conventional masonry units (CMUs). The innovative WGMUs demonstrated improved ductility and reduced density compared to CMUs, making them easier to handle and lighter in construction. They also have a distinctive, rustic texture and consistent dimensions that meet Australian standards. Although WGMUs exhibited higher water absorption and drying contraction due to their wood content, these characteristics generally remain within acceptable limits, supporting their potential as eco-friendly construction materials.

Development of Key Components for 5 kW Ammonia–Water Absorption Chiller with Air-Cooled Absorber and Condenser

An absorption chiller is an alternative cooling system that operates using heat from renewable energy sources and employs environmentally friendly working fluids, such as ammonia–water or lithium bromide–water. Given Indonesia’s high solar energy potential, solar cooling systems using absorption chillers are particularly promising. Solar thermal energy has been demonstrated to effectively power absorption chiller systems through both simulations and experiments. In Indonesia, there is significant potential to utilize small-capacity solar absorption chillers for buildings, particularly those employing air-cooled condensers and absorbers, which can reduce operational and maintenance costs. This research aimed to design a prototype of a 5 kW solar-assisted ammonia–water absorption chiller system specifically for residential applications. The system will be air-cooled to minimize space requirements compared to traditional water-cooled systems. The study addressed the design and specifications of the system’s components, dimensional considerations, and an analysis of the impact of the measurement instrument on the research outcomes. The results provide precise dimensions and specifications for the system components, offering a reference for the development of more advanced systems in the future.

Impact of biological environment on bending fatigue lifetime in additive-manufactured polylactic acid fabricated by 3D-printing

Polylactic acid (PLA) has become desirable for biomedical applications, particularly implantable devices. However, the degradation of PLA in biological environments under mechanical stress remains incompletely understood and requires further investigation. This study compared the plain fatigue (PF) and the biodegraded fatigue (BDF) behavior of 3D-printed PLA. For this purpose, two sets of standard fatigue specimens were additively manufactured by the fused filament fabrication (FFF) method. One set was used for plain fatigue testing, and the other was immersed for 330 days in simulated body fluid (SBF). After immersion, the samples were dried and weighed before fatigue testing. The fully reversed rotary bending fatigue tests were conducted on both sets of specimens, and the stress-lifetime (S-N) curves were obtained. Additionally, the fatigue properties of PF and BDF specimens were evaluated. Moreover, the fracture behaviors of the materials were studied using field emission scanning electron microscopy (FESEM). The outcomes implied that the weight of the samples extended during the immersion period, primarily due to water absorption by the PLA. However, after drying, the final weights did not change compared to the weights before immersion. The SBF immersion significantly reduced the fatigue performance of the biodegraded samples comparing the PF result.

Study on modification of natural hydraulic lime historical building repair mortar

Qingdao boasts a wealth of historical buildings, yet they have sustained varying degrees of damage due to environmental erosion over decades. Traditional cement-based repair materials can exacerbate the damage to these structures and often fall short of the stringent requirements for historical building restoration projects. Natural Hydraulic Lime (NHL) offers excellent compatibility and breathability, making it suitable for restorative work on historical buildings. However, its low early strength and durability pose limitations in Qingdao's complex environment. Consequently, this study investigates the enhancement of NHL mortar using Ground Granulated Blast Furnace Slag (GGBFS/BFS) powder. Nine mix formulations were developed to investigate the impact of varying BFS contents on the physical properties and microstructure of the repair mortar. The results indicate that, compared to the reference sample, the modified mortar exhibits reduced water requirement for normal consistency, shorter setting time, lower water absorption, and decreased shrinkage. Regarding mechanical properties, the incorporation of BFS significantly enhances the mechanical strength of the repair mortar. When the proportion of BFS is 60 %, the flexural and compressive strength of the mortar samples increase by 304% and 611% at 28 days, respectively. Upon incorporating BFS, a pozzolanic reaction occurs in the alkaline environment, leading to the formation of calcium silicate hydrate (C-S-H) gel. This gel fills the pores within the mortar, enhancing the densification of the system, which in turn improves the mechanical properties and microstructure of the repair mortar. SEM analysis corroborates these findings. XRD analysis confirms that BFS does not introduce harmful substances.