Conventional Lime Research Articles

Utilization of accelerated weathering of limestone captured carbon dioxide (CO2) with cement kiln dust to produce building material

The accelerated weathering of limestone (AWL) process is an inexpensive and eco-friendly carbon dioxide (CO2) capture process with comparable performance to amine-based systems. However, the generated calcium bicarbonate (Ca(HCO3)2) solution lacks an effective utilization alternative. Aside from that, the current solid waste utilization alternatives (i.e., carbon mineralization and partial replacement of conventional binders) lack the capability to effectively curb the tremendous production rate of solid waste (i.e., cement kiln dust (CKD)). To address both gaps, this study developed a novel Ca(HCO3)2 solution utilization alternative with CKD as the sole binder to produce a building material termed CKD-bicarbonate lime mortar (BLM). This work aims to identify the optimal mix ratio for CKD-BLM to achieve maximum compressive strength via a series of studies; (i) liquid medium, (ii) Ca(HCO3)2 solution volume, and (iii) sand:CKD mix ratio. From the findings, it was found that CKD-BLM at the optimal CKD:sand:Ca(HCO3)2 mix ratio of 1:0.45:0.29 exhibits the highest compressive strength of 2.09 MPa, surpassing the compressive strength standard of 1.70 MPa set by the ASTM C141 while having acceptable workability of 118 % which is within the standard workability range of 105–155 % set by ASTM C270. However, the CKD-BLM sample exhibits high leaching of Ca, Si, Na and Cl which does not meet the environmental regulation. This was resolved by applying a waterproof coating that effectively curbed the leaching by 28.84–99 %. Overall, this study successfully developed a building material with industrial wastes (i.e., Ca(HCO3)2 solution and CKD) that surpasses the performance of conventional lime mortar while utilizing up to 0.22 kg CO2.kg CKD-BLM_1:0.45:0.29−1.

Advancing Sustainability and Performance with Crushed Bottom Ash as Filler in Polymer-Modified Asphalt Concrete Mixtures.

Amid the growing demand for sustainable pavement solutions and the need to incorporate recycled materials into construction practices, this study explored the viability of using crushed thermal power plant bottom ash as a filler in polymer-modified asphalt concrete mixtures. Conventional lime filler was replaced with bottom ash at varying levels (0%, 25%, 50%, and 75%), and the resulting mixtures were evaluated using several performance tests. The optimal replacement level was determined to be 25%, based on the results of the indirect tensile strength (ITS) test. Comparisons between the control mixture and the 25% bottom ash-modified mixture were conducted using the dynamic modulus test, Cantabro test, Hamburg wheel tracking (HWT) test, and tensile strength ratio (TSR) test. The findings indicate that the 25% bottom ash-modified mixture demonstrated improved performance across multiple parameters. The HWT test showed enhanced rut durability, with a recorded depth of 7.56 mm compared to 8.9 mm for the control mixture. The Cantabro test results revealed lower weight loss percentages for the modified mixture, indicating better abrasion resistance. The dynamic modulus test indicated higher resilience and stiffness in both high- and low-frequency stages. The TSR test highlighted improved moisture resistance, with higher TSR values after 10 wet-drying cycles. These improvements are attributed to the fine particle size and beneficial chemical composition of bottom ash, which enhance the asphalt mixture's density, binder-aggregate adhesion, and overall durability. The results suggest that incorporating 25% crushed bottom ash as a filler in polymer-modified asphalt concrete mixtures is a viable and sustainable approach to improving pavement performance and longevity.

Simultaneous Environmental Waste Management through Deep Dewatering of Alum Sludge Using Waste-Derived Cellulose

To simultaneously solve problems in an eco-friendly manner, introducing a waste residual as a sustainable conditioner to aid alum sludge dewatering is suggested as a cradle-to-cradle form of waste management. In this regard, the superiority of deep dewatering alum sludge with a powdered wood chip composite residual as a novel conditioner was explored, whereby traditional conventional conditioners, i.e., polyelectrolytes and lime, were substituted with powdered wood chips. Initially, Fe3O4 was prepared at the nanoscale using a simple co-precipitation route. Next, wooden waste was chemically and thermally treated to attain cellulosic fine powder. Subsequently, the resultant wood powder and Fe3O4 nanoparticles were mixed at 50 wt % to attain a wood powder augmented with iron, and this conditioner was labeled nano-iron-cellulose (nIC-Conditioner). This material (nIC-Conditioner) was mixed with hydrogen peroxide to represent a dual oxidation and skeleton builder conditioning substance. Characterization of the resultant conditioner was carried out using transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) transmittance spectrum analysis. The feasibility of the experimental results revealed that the moisture content in the sludge cake was lower after conditioning, and the capillary suction time (CST) was reduced to 78% compared to that of raw alum sludge after 5 min of dewatering time. Moreover, the optimal system parameters, including nIC-Conditioner and H2O2 concentrations, as well as the working pH, were optimized, and optimal values were recorded at 1 g/L and 200 mg/L for nIC-Conditioner and H2O2, respectively, with a pH of 6.5. Additionally, scanning electron microscope (SEM) analyses of the sludge prior to and after conditioning were conducted to verify the change in sludge molecules due to this conditioning technique. The results of this study confirm the sustainability of an alum sludge and waste management facility.

Ceramic-added lime and cement mortars: A review of applications in building products.

Ceramic-added air lime mortars have been used since ancient times owing to the pozzolanic effect provided by crushed ceramic particles that impart hydraulic properties. This work reviews the historical use, composition, reaction mechanisms, characterization techniques, and performance properties of ceramic-added air lime mortars. The fine ceramic powder composed of silica and alumina phases reacts with calcium hydroxide released during lime hydration to form calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH) via pozzolanic reaction. This provides hydraulicity and reduces setting time compared to pure air lime mortars. The coarser ceramic particles also serve as aggregate and refine the microstructure as filler. The reactivity depends on the ceramic composition, amorphous phase content, particle size distribution, and firing temperature. Optimal proportioning of the fine ceramic powder and coarse ceramic aggregate is necessary to achieve desired properties. Ceramic addition enhances the durability of air lime mortars against weathering while maintaining compatibility with lime-based masonry structures. Key novelties of this review include: (i) in-depth analysis of the influence of ceramic characteristics (mineralogy, particle size, pozzolanicity) and processing on reaction kinetics and phase evolution; (ii) systematic assessment of mechanical, physical and durability properties in comparison to conventional air lime mortars and cement-based grouts; (iii) elucidation of microstructural mechanisms governing performance using advanced characterization techniques; (iv) critical appraisal of test methods and standards for evaluation; and (v) rigorous discussion on potential applications in construction, conservation and repair, with case studies.

Calcination of eggshell could be a lime source for leather processing in tannery

In leather processing, a significant amount of lime is required for leather processing. In this study, the effectiveness of calcined eggshell lime was compared with commercial lime for leather production. Commercial lime and eggshell lime are applied in liming operations for goatskin processing to produce shoe-upper leather. The calcined eggshells lime and conventional were characterized by X-ray Fluorescence (XRF) Spectrophotometer. The physicochemical properties of the manufactured leathers belonging to tensile strength and elongation percentage were evaluated and compared. Eggshells contain comparatively more lime (97.6%) than conventional lime (94.5%). The strength properties of the produced crust leather fulfilled the requirement of the shoe upper leather. The Scanning Electron Microscope (SEM) images of the limed pelts and final leathers showed similar fibre open-up. Lime produced from waste eggshells can be an effective alternative source of lime for leather processing.

A simple, cheap and effective glass coating for selective solar transmittance and radiative cooling applications

A cheap, simple, and scalable method for producing transparent radiative coolers (TRC) is introduced in this paper. A prototype of the TRC is fabricated that transmits the visible band of sunlight, highly reflects the near infrared spectrum, and selectively emit/absorb mid-IR in the atmospheric transparency window (AW). An outdoor experimental test for comparison is conducted. The experimental setup consists of two boxes with an illuminometer and a thermometer. One of the boxes has conventional soda lime, and the other has modified glass. The results show that the fabricated structure can reduce temperature as much as 21.97°C and also control the visible intensity of the sunlight by a factor of 4 to prevent glaring in daylighting of buildings, especially in hot climate regions. In the end, a comparison of the present work and similar experiments is provided.

Super adsorbent bio-polymer additive to improve hygroscopic and acoustic properties of a conventional lime plaster

The paper introduces a new lime plaster composition, with a Super Bio-Polymeric Adsorbent (SABP), for interior applications to improve hygrothermal and acoustic comfort. Alginate SABP is added to a conventional lime plaster to improve hygroscopic and acoustic performance. The hygrothermal and acoustic properties of the modified plaster are compared with the ones of the original plaster with a preliminary moisture uptake test, the evaluation of the sorption isotherm, the moisture buffering value (MBV), and the acoustic absorption. The results show a significant increase in the equilibrium moisture contents and the MBV (from 0.7 to 6.2 g/(m2⋅%RH)). At the same time, the sound absorption coefficient is slightly improved, increasing 0.1-0.2 at frequencies higher than 500 Hz compared to the reference conventional lime plaster. The paper describes the material characterization: the sorption isotherm and the MBV are obtained using a dynamic vapor sorption (DVS) analyzer. The acoustic absorption is measured using the impedance tube method.

Evaluation of Coffee Plants Transplanted to an Area with Surface and Deep Liming Based on Multispectral Indices Acquired Using Unmanned Aerial Vehicles

The use of new technologies to monitor and evaluate the management of coffee crops allowed for a significant increase in productivity. Precision coffee farming has leveraged the development of this commodity by using remote sensing and Unmanned Aerial Vehicles (UAVs). However, the success of coffee farming in the country also resulted from management practices, including liming management in the soils. This study aimed to evaluate the response of coffee seedlings transplanted to areas subjected to deep liming in comparison to conventional (surface) liming, using vegetation indices (VIs) generated by multispectral images acquired using UAVs. The study area was overflown bimonthly by UAVs to measure the plant height, crown diameter, and chlorophyll content in the field. The VIs were generated and compared with the data measured in the field using linear time graphs and a correlation analysis. Linear regression was performed to predict the biophysical parameters as a function of the VIs. A significant difference was found only in the chlorophyll content. Most indices were correlated with the biophysical parameters, particularly the green chlorophyll index (GCI) and the canopy area calculated via vectorization. Therefore, UAVs proved to be effective coffee monitoring tools and can be recommended for coffee producers.

Effective utilisation of waste cement concrete dust in bituminous concrete

The suitability of waste cement concrete dust (CD) and conventional hydrated lime (HL) as fillers in bituminous concrete was investigated. Bituminous mixes containing CD or HL in different proportions were designed. Their performance was studied using the Marshall quotient, indirect tensile strength, tensile strength ratio (TSR), passive and active adhesion and Cantabro tests. The cost of the various mixes and their greenhouse gas (GHG) emissions were also compared. Finally, the optimum filler content for both mixes was determined. The mixes containing CD displayed rutting, cracking and ravelling resistance similar to those of conventional mixes. CD offered improved affinity towards bitumen and ensured excellent moisture resistance (TSR > 80%). Compared with a traditional mix (4% HL), the use of CD marginally lowered the cost by around 3–8% and reduced the GHG emissions by more than 50%. Overall, the addition of CD ensured satisfactory engineering performance at a relatively lower cost and significantly lower GHG emissions.

Optimal treatment technology selection for acid mine drainage via spherical fuzzy analytic hierarchy process

The Philippines is endowed with large deposits of mineral resources, but mining operations have the potential to negatively impact the environment. For example, acid mine drainage (AMD) is a problem that occurs when sulfide minerals are exposed to air, water, and microbial activity, releasing hazardous elements. Many treatment options have been proposed to date to address these negative impacts of AMD. However, little effort has been made over the years to develop a generalized framework for the selection of the optimum technology for AMD treatment. This study thus proposes the spherical fuzzy analytic hierarchy process (SFAHP) as a multi-criteria decision analysis tool to select the best treatment technology for the treatment of AMD. The use of SFAHP is novel in this context as it addresses uncertainty due to indeterminacy by incorporating a “hesitancy parameter” in the decision-making process. Three treatment options were evaluated using a set of criteria such as technical, economical, and environmental aspects. The results showed that the combination of the two-step neutralization ferrite formation and sulfidogenic bioreactor (TSNFF + SB) was considered the most sustainable, with the environmental aspect being the most important factor. The second most preferred option is the high-density sludge (HDS) process while the least preferred is the combination of the conventional lime neutralization and sulfidogenic bioreactor (CLN + SB). A sensitivity analysis was also done, and a comparison with traditional AHP was conducted, which also found TSNFF + SB to be the best option. This illustrative case study demonstrates the robust framework built from SFAHP for selecting the best technology to manage AMD and addresses uncertainty in the decision-making process.

Enhancement of the hygroscopic and acoustic properties of indoor plasters with a Super Adsorbent Calcium Alginate BioPolymer

The present study introduces a novel-composition lime plaster that contains a Super Adsorbent BioPolymer (SABP) based on Calcium Alginate (CaAlg) for indoor applications, to improve hygrothermal and acoustic comfort. The sorption isotherm of the plaster, the moisture buffering value (MBV), the acoustic absorption, and the thermal conductivity have been assessed. The hygrothermal and acoustic properties of the modified plaster have been compared with those of the original composition to evaluate its performance under different concentrations of CaAlg (between 10 and 30% wt). Adding the CaAlg SABP to a conventional lime plaster consistently enhanced its hygroscopic properties. The results show a substantial increase in the equilibrium moisture uptake (between 10 and 23 fold) and MBV, from 0.9 to 9.3 g/(m2⋅%RH). The sound absorption coefficient improved by 0.1–0.2 at higher frequencies than 500 Hz. This paper provides detailed information on the characterization of the material. It includes details about using a dynamic vapor sorption (DVS) analyzer to evaluate the sorption isotherm and MBV. It also contains information on the impedance tube method used to measure the acoustic absorption of the material.

Forest Road Subgrade Improvement by Lime and Sodium Nanoalginate Used as Stabilizers for Clay Soils

Fine-grained soils cause problems for forest road construction and often require improvements of their mechanical properties. One of the methods of improving mechanical properties of clay soils is soil stabilization. In this study, the effect of a conventional (lime) and a non-conventional (sodium nanoalginate) stabilizer on improving the characteristics of a high plasticity forest soil was compared. Atterberg limits including liquid limit, plastic limit and plasticity index, standard Proctor, UCS (Unconfined Compression Strength) and CBR (California Bearing Ratio) tests were performed on control (untreated) and soil samples treated with different doses (3%, 5% and 7%) of lime and sodium nanoalginate, according to the standard procedures. Moreover, to evaluate the effect of curing time, additional tests were performed on the soil samples treated with 3% lime and 3% sodium nanoalginate at 7, 14 and 28 days after the treatment. The results indicated that adding sodium nanoalginate and lime to the forest soil improves the Atterberg limits. Additionally, adding sodium nanoalginate to the forest soil increases the maximum dry density (γdmax) and decreases the optimum moisture content (OMC), whereas adding lime to the forest soil reduces the maximum dry density and increases the optimum moisture content. Adding sodium nanoalginate and lime in different doses (3%, 5% and 7%) increased UCS and CBR as the main indices of soil strength. The increment range of UCS for the soil stabilized with sodium nanoalginate and lime was 42.59%–160.14% and 31.34%–56.65%, respectively, and the range of CBR improvement for soil stabilized with sodium nanoalginate and lime was 28.72%–122.97% and 13.83%–45.59%, respectively. Increasing the curing time improved the mechanical properties of the forest soil in the samples treated with both stabilizers, but sodium nanoalginate performed better in soil stabilization.

Evaluation of the Effect of Binary Fly Ash-Lime Mixture on the Bearing Capacity of Natural Soils: A Comparison with Two Conventional Stabilizers Lime and Portland Cement.

This study evaluates a binary mixture of fly ash and lime as a stabilizer for natural soils. A comparative analysis was performed on the effect on the bearing capacity of silty, sandy and clayey soils after the addition of lime and ordinary Portland cement as conventional stabilizers, and a non-conventional product of a binary mixture of fly ash and Ca(OH)2 called FLM. Laboratory tests were carried out to evaluate the effect of additions on the bearing capacity of stabilized soils by unconfined compressive strength (UCS). In addition, a mineralogical analysis to validate the presence of cementitious phases due to chemical reactions with FLM was performed. The highest UCS values were found in the soils that required the highest water demand for compaction. Thus, the silty soil added with FLM reached 10 MPa after 28 days of curing, which was in agreement with the analysis of the FLM pastes, where soil moistures higher than 20% showed the best mechanical characteristics. Furthermore, a 120 m long track was built with stabilized soil to evaluate its structural behavior for 10 months. An increase of 200% in the resilient modulus of the FLM-stabilized soils was identified, and a decrease of up to 50% in the roughness index of the FLM, lime (L) and Ordinary Portland Cement (OPC)-stabilized soils compared to the soil without addition, resulting in more functional surfaces.

Ameliorative effect of calcium poly(aspartic acid) (PASP-Ca) and calcium poly-γ-glutamic acid (γ-PGA-Ca) on soil acidity in different horizons.

Soil acidification is a worldwide eco-environmental problem detrimental to plant growth and threatening food security. In this study, calcium poly(aspartic acid) (PASP-Ca) and calcium poly-γ-glutamic acid (γ-PGA-Ca) were obtained through cation exchange and used to mitigate soil acidity owing to high solubility and complexing capability. Three rates at 6.7, 13.4, and 20.1gkg-1, denoted as PASP-Ca1, PASP-Ca2, and PASP-Ca3, and γ-PGA-Ca (7.4gkg-1) were surface-applied and compared with conventional lime (CaCO3, 2.5gkg-1) along with control in two soil layers (top soil 0-10cm, subsoil 10-20cm). After leaching, various soil properties and aluminum fractions were measured to assess their ameliorative performance and mechanisms. Although lime achieved the highest soil pH (6.91) in the topsoil followed by PASP-Ca and γ-PGA-Ca (pH: 5.57-6.33), it had less effect on subsoil increase (5.3) vs. PASP-Ca and γ-PGA-Ca (pH: 5.44-5.74). Surface-applied PASP-Ca demonstrated efficiency in elevating soil pH and reducing exchangeable acidity, mainly as exchangeable Al3+, whereas γ-PGA-Ca addition superiorly improved soil pH buffering capacity (pHBC). Moreover, PASP-Ca and γ-PGA-Ca addition improved organic carbon by 34.4-44.9%, available P by 4.80-20.71%, and cation exchange capacity (CEC) by 6.19-29.2%, thus greatly enhanced soil fertility. Ca2+ from polyAA-Ca promoted the displacement of exchangeable Al3+ or H+ from soil colloid, which were subsequently complexed or protonated and facilitated leaching. Additionally, the transformation into stable organo-aluminum fractions via complexation inhibited further hydrolysis. Under PASP-Ca or γ-PGA-Ca addition, the saturation of aluminum in cation exchange complex was reduced 2.91-7.81% compared to the control without addition amendments. Thus, PASP-Ca and γ-PGA-Ca can serve as potent ameliorants to alleviate soil acidity and aluminum toxicity for sustainable agricultural development.

Feasibility of Pellet Material Incorporating Anti-Stripping Emulsifier and Slaked Lime for Pothole Restoration

Climate change has caused a surge in abnormal weather patterns, leading to a rise in cracks, plastic deformation, and pothole damage on road surfaces. In order to fabricate a ready-mix admixture of warm asphalt mixture (WMA) for pothole restoration, this study aimed to develop a neutralized anti-stripping material in pellet form by extruding a combination of slaked lime and a liquid emulsifier additive. Slaked lime (1% by weight of aggregate) was chosen for its ability to enhance moisture resistance, while a liquid emulsifier (wax + vegetable oil + surfactant + water) was added to create a pellet-type stripping inhibitor for WMA. After successfully fabricating the pellet admixture, this study evaluated the performance of two asphalt mixtures: conventional Slaked Lime Hot Mix Asphalt (LHMA) and the Pellet-Type Anti-Stripping Warm Mix Asphalt (PWMA). Several compatibility tests were conducted to evaluate the quality of the developed material. The results showed that the fatigue resistance of the developed material (PWMA) improved by over 20%, indicating an extended fatigue life for the pavement. The LHMA and PWMA met the quality standard for asphalt mixtures, with a TSR value of approximately 83%. Both mixtures demonstrated improved rutting resistance compared to HMA. The PWMA required 16,500 cycles, while the LHMA required 19,650 cycles to reach a settlement of 20 mm, indicating better moisture resistance than the control mix (13,481 cycles). The modified mixture performed properly in the Cantabro test, with loss rates below 20%, indicating their ability to retain their aggregate structure. The PWMA also showed superior resistance to plastic deformation, with a 12.5% lower phase angle (35°) at a reduced frequency of 10−3. In general, the application of PWMA not only prolongs the pavement lifespan but also reduces the production temperature by over 20 °C, leading to lower emissions and energy consumption. This makes it an environmentally friendly option for pavement applications and contributes to sustainable road construction practices.

Synthetic fertilizers and vermicompost in juvenile Persian lime (Citrus x latifolia Tanaka ex Q. Jiménez) trees

Objective: To evaluate fertilization with vermicompost and NPK mineral fertilizer in young Persian lime (Citrus x latifolia Tanaka ex Q. Jiménez) trees. Design/Methodology/Approach: A randomized block design was established with eight treatments and four repetitions: T1, 0 kg tree-1; T2, 90-22.5-22.5 N-P-K kg ha-1; T3, 2 kg tree-1 of vermicompost; T4, 3 kg tree-1 of vermicompost; T5, 4 kg tree-1 of vermicompost; T6, 90-22.5-22.5 N-P-K kg ha-1 + 2 kg tree-1 of vermicompost; T7, 90-22.5-22.5 N-P-K kg ha-1 + 3 kg tree-1 of vermicompost; and T8, 90-22.5-22.5 N-P-K kg ha-1 + 4 kg tree-1 of vermicompost. The study variables were tree height, stem thickness, crown diameter from North to South (N-S) and East to West (E-W), soil pH, and soil moisture (%). The data were statistically analyzed applying the MINITAB V.17 statistic through an ANOVA (P≤0.05), while a multivariate analysis was used for the means comparison. Results: The tree height and crown diameter variables had different results in the Persian lime trees treated with 4 kg tree-1 of vermicompost (T5). The tree canopy had a similar development than T5 with vermicompost treatments combined with NPK mineral fertilizer. Study Limitations/Implications: Conventional lime production indiscriminately uses synthetic fertilizers, polluting natural resources. Organic fertilizers are a nutritional alternative for the trees. Findings/Conclusions: The vermicompost treatment efficiently maintains adequate soil moisture during the dry season, improving the growth and development of Persian lime trees.

Replacing Lime with Rice Husk Ash to Reduce Carbon Footprint of Bituminous Mixtures

There have been several emphasized pathways toward a reduction in carbon footprint in the built environment such as recycling, technologies with lower energy consumption, and alternative materials. Among alternative materials, bio-based materials and nature inspired solutions have been well-received. This study examines the merits of using rice husk ash as a replacement for lime; lime has a high carbon footprint mainly associated with the decomposition of calcium carbonate to calcium oxide to form lime. Lime is commonly used in bituminous composites for roadway construction to mitigate their susceptibility to moisture damage. Replacing lime with a low-carbon alternative could allow a reduction in CO2 equivalent of bituminous composites. This paper studies the merits of using rice husk ash (RHA) as a substitute for conventional hydrated lime (HL) in bituminous composites. It should be noted that rice industries burn rice husks in a boiler as fuel, generating a substantial volume of RHA. The disposal of this ash has major environmental impacts associated with the contamination of air and water. Here, we study physical and chemical characteristics of both HL and RHA for use in bitumen mixtures. This was followed by examining the extent of dispersion of each filler in bitumen via optical microscopy to ensure their uniform dispersion. The properties of the mixtures were further studied using the Marshall mix design method. It was found that a 25.67% increase in Marshall stability and a 5.95% decrease in optimum binder content were achieved when HL was replaced by RHA at 4% filler concentration. In addition, mixtures containing RHA exhibited higher resistance to cracking and permanent deformation compared to mixtures containing HL. Additionally, 4% RHA in the mix showed stripping resistance similar to the conventional mix with HL. The mixture with 4% RHA had a lower carbon footprint with enhanced economic and environmental impacts compared to the conventional mix with HL. The study results provide insights pertaining to the merits of bio-based materials to reduce the carbon footprint of pavements.

Applicability of Alkaline Waste and By-products as Low Cost Alternative Neutralizers for Acidic Soils

Acidic soils can induce several negative impacts, especially in agricultural fields. To address these problems, lime is often applied to increase the pH value of acidic soils. Calcium carbonate is the most common and conventional agricultural lime; however, it is a natural and scarce resource. To promote a recycling-based society, alternative neutralizers with lower costs that use alkaline waste and by-products are essential. Therefore, we investigated the effectiveness and applicability of three types of autoclaved lightweight aerated concrete, recycled concrete, steel slag as basic oxygen furnace slag, and fly ash (mainly particles less than 0.106 mm and 0.106–2 mm in size), as alternative neutralizers for three representative acidic soils through laboratory neutralization experiments. The neutralization performance was evaluated by measuring the additive weight percentage of each neutralizer required to convert each acidic soil to neutral soil (pH 7). For neutralizers with two particle sizes, the finer fraction clearly showed lower additive weight percentages indicating higher neutralization performance. Among the six tested alkaline waste and by-products, the steel slag exhibited the highest neutralization performance. In particular, finer fraction steel slag exhibited a high neutralization performance, similar to that of the conventionally used calcium carbonate. This result suggests that fine steel slag (particle size < 0.106 mm) is the most promising and suitable alternative neutralizer.

Assessment of Natural Additives Modified Lime Mortars for Repair of Historic Structures with Strength, Durability and Microstructural Parameters

The contemporary building material despite the significance of cement in construction industry is the lime mortars because of its usage as a structural repair material around the ancient heritage structures. Though the significance of lime mortars lies in the fact of compatibility towards the existing ancient lime-based structures, the method of construction and material preparations are still undisclosed. In such a case, it is necessary for the researchers to analyze scientifically, the influences of various additives towards the performance of lime mortars. This paper tries to attempt two natural additives viz., gallnut (Terminalia chebula) and palm jaggery (Saccharam officinarum) as modifiers of mixing water in the preparation of class B hydraulic lime-based mortars through the process of fermentation. Based upon the trials, 39 mixes were considered with varying water to lime ratios and dosages of additives. Experimental tests such as workability, compressive strength, water absorption, acid resistance and NaCl cyclic tests were conducted along with SEM and XRD microstructural assessments. The maximum compressive strength achieved was about 4.3 MPa which is 200% that of conventional lime mortars. Jaggery and gallnut-based additives were efficient in various durability studies however the performance of jaggery is superior to gallnut in various aspects.

Production of the Traditional Organic Mortars of Padmanabhapuram Palace—A Characterization Study on the Simulated Mortars for Their Compatibility

The scientific investigation performed on the different mortar typologies of the Padmanabhapuram Palace mortars in a previous study led to the formulation of a similar traditional mortar. The outcome of the study was an increase in the carbonation action and mechanical strength of the mortar compared to conventional lime mortar, primarily due to the fermented organics such as aloe vera, cactus, kadukkai, hibiscus, jaggery, and neelamari. The transformation of portlandite crystals to calcite, along with the early developed C-S-H and C-A-S-H hydrated products reported by the XRD analysis. The bio-organic spectral peaks for compounds such as carbohydrates, polysaccharides, and fatty acids were observed in the FT-IR investigation, which corroborates the XRD mineralogical results. The calcite decomposition is detected in the TGA analysis in the temperature range of 700–750 °C, with a maximum weight loss of approximately 35–37% for the aloe vera lime mortar. The addition of fermented organic extracts to the extent of 5% was found to increase the internal and external carbon absorption of the aloe vera and cactus mortars compared to conventional lime mortars. The mechanical strength of the organic lime mortar reported as 2.5 MPa, and 1.5 MPa for the reference mortar. The carbonation and hydraulic reactions due to the presence of polysaccharides, fatty acids, carbohydrates, and proteins in the formulation enhanced the compressive strength of the compatible mortar. The prepared compatible mortar will support the revival of the 400-year-old practice of the application of Palace mortars.