Ratio Of Lime Research Articles

The Effect of Hydrated Lime Mixing Forms and Ratios on Performance in Asphalt Pavements

In this study; the water damage problem and indirect tensile strengths (ITS) were investigated for different hydrated lime (HL) additive ratios and adding methods. In this regard, identical briquettes modified with hydrated lime have been produced. HL was used both in the bituminous binder (wet method) and as part of the filler aggregate. The hydrated lime was added in two different ways to form the defined equivalent ratios. By producing nine identical briquettes in each option, the values of water damage and ITS in both unconditioned and modified mixtures were compared, and the level of significance differences between the identical briquettes and mixtures was questioned. Increasing the HL content increases the standard deviation between identical samples in terms of ITS. The workability of the mixture is adversely affected by the increase in the hydrated lime ratio. When HL is mixed into the asphalt cement (AC), the standard deviations of ITS values among identical samples remain lower due to the increase in mixing rates. Increasing the ratio of adding HL to the asphalt cement reduces the ITS ratios compared to the option of adding filler to aggregate. If HL is added to the mixture in low HL content, the water damage ratios show, on average, higher water damage resistance (15% higher) than the HL being added to the AC. However, if the HL content is increased to medium and high levels, mixing HL to AC creates higher water damage resistance than adding it as filler.

Utilization and Remediation of Heavily Cadmium-Contaminated Agricultural Soils by Two Crop Rotation Patterns After Lime and Sepiolite Passivation

In order to safely utilize and remediate the heavily cadmium-contaminated farmland in a mining area and ensure that the crops meet the feed safety standards, two rotation patterns (maize-alfalfa and maize-ryegrass) were tested after passivation with different ratios of lime and sepiolite as passivating agents, and the best ratio of passivating agent and matching crop rotation patterns were selected through comprehensive analysis and comparison. The field test was conducted to determine the physical and chemical properties of the soil, the content of the effective state of the heavy metal Cd, and the content and biomass of Cd in crops. We also studied the changes in heavy metal morphology before and after soil passivation using the BCR morphology classification test and comprehensively analyzed and evaluated its remediation effect. ① The results showed that the soil pH, organic matter, and CEC could be increased to different degrees by the application of lime and sepiolite. ② The recommended application amount of LS1 (lime 6.6 t·hm-2+sepiolite 9.9 t·hm-2) significantly reduced the content of heavy metal Cd in maize roots, stems, leaves, and seeds by 70.27%, 61.54%, 46.51%, and 44.23%, respectively, compared with those of CK. The Cd above ground in alfalfa was significantly reduced by 78.47%, whereas the Cd above ground in ryegrass was significantly reduced by 65.79%. The effective state Cd passivation rate of the soil was 51.37%, 69.58%, and 77.83% in the corn season, alfalfa growing area, and ryegrass growing area, respectively. The heavy metals in the soil were converted from the weak acid extracted state with high activity to the residual state with low activity. ③ The recommended crop rotation pattern of supporting maize-alfalfa under the applied amount of LS1 can significantly increase alfalfa yield while slightly increasing maize yield compared with those of CK, and the forageable parts can meet the feed standard[GB 13078-2017, ω(Cd) ≤ 1 mg·kg-1], achieving safe cultivation with the lowest restoration cost.

Study on the Material Properties of Microconcrete by Dynamic Model Test.

As an important water conveying structure, the seismic safety of the hydraulic aqueduct has attracted considerable interest. Different from the general bridge structure, the seismic analysis of the aqueduct structure needs to consider its fluid–structure interaction. The existing numerical simulation methods cannot truly reflect the fluid–solid coupling mechanism. Therefore, scholars began to use shaking table tests to study the fluid–structure interaction mechanism. However, the research is immature, and it is mostly focused on the seismic response analysis, and there are few studies on the model test similarity ratio and model material properties. Based on this, in this paper, according to the requirements of the test similarity ratio, the orthogonal experiment was used to explore the influence of barite sand content, water–cement ratio, fine sand ratio, and lime ratio on the mechanical properties of microconcrete. The performance indicators of microconcrete under different mix ratios vary widely, with a minimum variation of 19% and a maximum of 102%. Barite sand has the most significant control effect on the density, and the water–cement ratio has the most significant control effect on the compressive strength and elastic modulus. The density variation range is 2.37–2.81 g/cm3, the cube compressive strength variation range is 18.37–36.94 MPa, and the elastic modulus variation range is 2.11 × 104–3.28 × 104 MPa. This study will provide certain evidence for the similarity ratio design and material selection of the scaled model test of the fluid–solid coupling structure.

Guaruman fiber: A promising reinforcement for cement-based mortars

Guaruman fiber is a natural lignocellulosic fiber (NFL) extracted from the stalk of an Amazon plant (Ishinosiphon Koern), in the northern region of Brazil. The present work investigates the addition of 2.5, 5.0 and 7.5 wt% of guaruman fiber, into cement for a reference mortar. The fibers were mercerized in NaOH solution for improved adhesion to a mortar matrix made with 1:1:6 ratio of ordinary Portland cement, lime and natural sand. Technical properties of mass density, consistency, incorporated air content and water retention were for the first time evaluated for the as-processed fresh state of the mortar reinforced with this NFL. All methodologies used were adapted to the Brazilian technical standards. Relevant data were obtained from the international literature on the subject. It was found that the addition of NaOH-treated guaruman fiber practically does not affect the workability properties of the mortar. The results showed that the fiber surface treatment process promoted a mass density increase of ≈ 3% in the fresh state for the mortar with 7.5% of guaruman fibers. Meanwhile, this same trend was observed in water retention, which for the 7.5% mortar changed from 92.7%, with its fibers in the natural condition, to 94.24% in the treated condition. The incorporated air content increased in relation to the reference mixture, reducing comparatively in the treated conditions. These preliminary results in association with the relatively low mass density of the mortars incorporated with NaOH-treated guaruman fibers reveal a promising material to be applied as mortar for wall covering in civil construction, in a proportion of 7.5 wt%, which shows a great potential for the use of this fiber.

Dissolution behavior of partially calcined limestone with residual CO2 in converter slag

Accelerating the dissolution rate of lime in converter slag at the initial stage of steelmaking is conducive to the rapid slagging. In this work, partially calcined limestone with a core–shell structure was prepared, and the dissolution behaviors of lime, partially calcined limestone bearing ∼28 wt% CO2, and limestone in converter slag were studied. The results showed that the formation of 2CaO·SiO2 layer slows down the dissolution of lime. Different from lime, the CO2 bubbles produced by the limestone decomposition could destroy the 2CaO·SiO2 layer and accelerate the dissolutions of limestone and partially calcined limestone. Compared with limestone, the slag temperature drop near the surface is less, and no stagnation stage occurs during the dissolution of partially calcined limestone due to the existence of decomposed lime surface layer. The most rapid dissolution rate and the higher substitution ratio of lime imply that the partially calcined limestone slagging mode would be more promising than limestone and lime.

Rapid preparation of a composite insulating block comprising waste expanded polystyrene (EPS) foam and rice straw

Due to the world’s decreasing energy supply, reducing the energy consumption of building envelopes has become an urgent issue with economic benefits. Rice straw is a generally available agricultural residue. The purpose of this study was to estimate the effects of rapid pretreatment methods and slaked lime on the molding of rice straw insulation blocks and to evaluate the effectiveness of integrating expanded polystyrene (EPS) particle waste with rice straw as building materials to reduce the energy loss in buildings. The pretreatment time was shortened from 6 h to 3 h by mechanical stirring combined with lye soaking. The molding of the insulation block could be improved by the hardening of slaked lime through contrast experiments and electron microscope scanning. Moreover, the influences of the mass ratio of slaked lime to rice straw (RSR) and the dosage of the EPS particles (ωEPS) on the dry apparent density and the thermal conductivity of the insulation blocks were studied. The results showed that the slaked lime would increase the dry apparent density and weight of the insulation block, but the EPS can effectively reduce this negative effect and keep the thermal conductivity of the insulation block below 0.049 W·m-1·K-1. Ultimately, the rapid pretreatment technology was determined to include lye soaking for 3 h and mechanical stirring for 5 min. The material matching ratio scheme was determined to have a ωEPS value of less than 3% and an RSR value equal to 1/7.5.

Design, fabrication, and characterization of distinguished lightweight and sustainable building materials

As one of the eco-friendly building materials, autoclaved aerated concrete (AAC) has received considerable attention in industrial and academic research groups over the last few years. Herein, new AAC composites with different ratios of fine sand, lime, cement, and gypsum plaster were prepared in an autoclave at a pressure of 10 bar for 8 h. The effects of adding a polymelamine sulfonate (PMS) superplasticizer to the prepared AAC composites on workability were investigated according to their physical and mechanical properties. The binding phase of calcium silicate hydrate was fully characterized via Fourier transform infrared (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The effect of AAC slurry foaming agent and water to solid ratio (W/S) was reported in detail. Furthermore, we studied the effect of ultrafine sand (<63 μm) reinforcement on the properties of AAC products.Under the specified curing conditions, the results showed that a strength value of 3.8 MPa with a low bulk density of 0.60 g/cm3 (600 kg/m3) was obtained from an AAC composite with 65 wt% fine sand, 15 wt% lime, 15 wt% cement, and 5 wt% gypsum plasters, containing 0.12 wt% Al powder and 45% water to solid ratio (W/S) mixtures. The strength value of the AAC composite can increase to 4.8 MPa, maintaining a low bulk density of 0.60 g/cm3 when the AAC slurry composite included 1% PMS at a W/S of 56% and 0.08% Al powder. In particular, the production of ultra low-density building materials can be efficiently controlled by mixing superplasticized AAC slurries with 0.16 wt% Al powder (at W/S = 56%), reaching a low bulk density of 0.39 g/cm3 (390 kg/m3) with a reasonable strength of 1.70 MPa for AAC samples. Interestingly, 50 wt% of fine sand with a particle size of about 90 μm is sufficient for tobermorite formation from the sand-lime reaction at designated hydrothermal conditions. However, replacing the large particles with ultrafine sand (<63μ) reduced the AAC strength characteristics. Besides, the compressive strength was improved by forming long tobermorite needles, lath structures, or both. In contrast, the gel-like material (poorly crystallized tobermorite) provides the lowest strength properties for AAC (about 3 MPa).

Hydration behavior of circulating fluidized bed fly ash (CFBFA) as a cementitious binder

In this study, the hydration behavior of circulating fluidized bed fly ash (CFBFA) as a cementitious binder was investigated in a CFBFA-lime system. Binary mixtures of CFBFA and lime were prepared with different weight ratios, and a series of experiments were performed to evaluate the hydration behavior of the mixtures. When the mixing weight ratio of CFBFA and lime was 5:1, the prepared mixtures could reach 17 MPa at 28 days. Hydration heat curves revealed that the release heat peak related to the hydration of CFBFA appeared earlier as the content of lime increased. This likely stemmed from the release of heat by the hydration of lime. Analysis of Ca(OH)2 consumption and chemically bound water revealed that the hydration reaction of mixtures can continue for a long time after Ca(OH)2 was depleted. In addition, the main hydration products of the CFBFA-lime system were C-S-H, C-A-S-H, AFm and AFt. The micro-morphology of the hydration products changed from needles to mesh-like and then to foil-like as the lime content in mixtures increased.

Experimental Study on the Comprehensive Identification and Improvement of Dispersive Soil in Western Jilin Province, China

In this study, physical experiments, clay mineral determination, and pH testing were performed to examine the basic properties of soil samples from a soil material yard selected for dam construction at Hua’ao Lake, Qian’an County, Jilin Province, China. The results show that the soil in the study area is cohesive, the mineral content of illite in the illite/montmorillonite mixed layer is approximately 50%, and the pH value of the environment from which the soil samples were taken is 8.43-8.91. These factors enable the soil in this area to be dispersed. The dispersibility of the soil sampled from this area was evaluated by a double hydrometer test, a pinhole test, a fragmentation test, a sodium adsorption ratio test, and determination of the percentage of exchangeable sodium ions. Because these test methods had inconsistent results, the test methods in combination with the typical geomorphic conditions of the sampling points were ultimately used to comprehensively evaluate the soil dispersion. The results demonstrate that the cohesive soil sampled from the soil material yard is dispersible and must be treated with improvement measures before it can be used as a filling material for the dam. To improve the dispersive and transitional soil, 2%, 3%, 4%, 5%, and 6% L1Fa2 (a 1 : 2 ratio of lime and fly ash) and C1L1Fa4 (a 1 : 1 : 4 ratio of cement, lime, and fly ash) were used to perform improvement tests on 10 groups of dispersive soil samples and 10 groups of transitional soil samples. The results reveal that the addition of 4% L1Fa2 best improves the dispersive soil in this area. Therefore, the soil intended for this project should be used as a dam-building material after improvement with the 4% addition of L1Fa2.

Experimental Investigation of Traditional Clay Brick and Lime Mortar Intended for Restoration of Cultural Heritage Sites

To properly restore masonry cultural heritage sites, the materials used for retrofitting can have a critical effect, and this requires standards for traditional Korean brick and lime mortar to be examined. This study experimentally investigated the material characteristics of Korean traditional bricks and two types of lime mortar (quicklime lumps and powdered hydrated lime) and the strength of masonry specimens made from those materials. Four different mixing ratios of lime, sand and white cement were considered as material parameters in this study. The experiment included uniaxial compressive testing and flexural testing to examine the mortars’ mechanical properties, and compression tests, triplet shear tests and diagonal compression tests for the masonry specimens. The results found that the strength of the masonry specimens was not necessarily associated with the mortar’s strength, but rather the cohesion between brick and mortar. In the material test, adding white cement had no noticeable effect on mortar strength. Meanwhile, in the masonry specimen, the effect of the added white cement was significant in terms of compressive and shear strength. This suggests that the bonding ratio between mortar and brick, which is an important factor influencing the behavior of bricks, was stronger with the addition of white cement. Furthermore, it was found that quicklime lumps had a lower strength than powdered hydrated lime. The test specimen with white cement added to powdered hydrated lime exhibited the greatest strength.

Effect of amendments (lime–zeolite–biochar) on the immobilization of Cd and Pb in a contaminated acidic soil

An incubation experiment was carried out to study the remediation effect of lime, zeolite and biochar under different ratios on cadmium (Cd) and lead (Pb) contaminated soil. Soil pH, organic carbon (SOC), bioavailability and mobility of Cd and Pb were investigated. The results indicated that combined application of lime, zeolite and biochar can significantly increase soil pH, the increment was from 0.15 to 0.76. Compared to the control treatment, the concentrations of CaCl2-, TCLP-Cd and Pb significantly decreased in all amended treatments. Considering the soil environmental quality and immobilization efficiency, the ratio of lime, zeolite and biochar was determined to be 1:2:2. The application rate of combined amendment (lime:zeolite:biochar=1:2:2) had obvious effect on soil pH, SOC and removal efficiency of Cd and Pb, promoting the acid soluble fractions of Cd and Pb to residual fractions, especially in higher application rate (5.0% and 10.0%). However, there was no significant difference when the application rate exceeded 5.0%. Therefore, it was suggested that the application rate of combined amendment (lime:zeolite:biochar=1:2:2) could be 5.0% in short-term soil remediation.

Water Resistance Properties of Lime Soil Ground under Long-Term Soaking Environment

To explore the water resistance properties of lime soil ground, the physical and mechanical properties of lime soil with 5%, 10%, 15% and 20% lime content after long-term water immersion were studied by conducting unconfined compressive tests, density tests and water absorption tests. The results show that the stress–strain relationship curves of the lime soil during immersion are of the strain-softening type. The curves are multistage and nonlinear with evident peak values, and the lime soil achieves ductility and toughness with an increase in immersion time. The failure modes of the lime soil samples mainly include single slope shear failures, brittle splitting failures and conjugate shear failures, which are mainly affected by the lime content and immersion time. The strength of the lime soil decreases sharply in a short time while interacting with water. The strength slowly increases to 50.07–69.15% of the initial strength after immersion for a long time, i.e., still far less than the initial strength without immersion. Under long-term immersion, the water absorption of the lime soil increases gradually at the initial stage of immersion and then increases to a stable value of 16.76–21.67%. The change law of the wet density is essentially controlled by the water absorption. The strength of lime soil decreases significantly, and the water resistance capacity is poor after soaking; lime soil with 15% lime content has better engineering properties. It is recommended to apply lime soil with 15% lime content in practical engineering with a volume ratio of lime to soil of 3:7 and to avoid using lime soil materials in immersed or other dry-humid environments.

Lime –Metakaolin Interaction

The standard mix ratio of lime: pozzolana specified by all standards is 1:2 by weight to produce lime pozzolan cement (LPC) with the minimum required strength of 4 MPa. This ratio may be affected by many factors such as the quality of lime and pozzolana, in adition to the quantity of amorphous silica in pozzolana. In this paper a local kaolin and lime were investigated for their chemical, physical, mineralogical, and thermal properties, using various techniques such as XRF, DTG/DSC, and XRD. The produced metakaolin (MK) and hydrated lime (CH) were first tested for their reactivity, then different ratios of 1:2, 1:3, and 1:4 (lime: metakaolin) were tested to determine the optimum mix ratio of (LPC). The chemical, physical, and mineralogical analysis of samples showed their congruent with standard specifications adopted. The chemical analysis results showed that the local kaolin has composition with a SiO2+Al2O3+Fe2O3 content of 79.96%. The reactivity of MK toward CH is found to be within the limitation of standards. The mortar samples, made with a binder of ground MK and CH, developed a 28 days compressive strengths of 4.9, 14, and 16 MPa, for 1:2, 1:3, and 1:4 (CH: MK ) respectively. These findings suggest that LPC can be produced with high compressive strength if an optimum lime to pozzolana ratio is achieved.

Cd bioavailability and nitrogen cycling microbes interaction affected by mixed amendments under paddy-pak choi continued planting.

Cadmium (Cd) is the most concerning soil pollutant, and a threat to human health, especially in China. The in-situ immobilization of Cadmium by amendments is one of the most widely adopted methods to remedy soil contamination. The study was designed to evaluate the effect of organo-chemical amendments on soil Cd bioavailability and nitrogen cycling microbes under continuous planting of rice (Oryza sativa) and pak choi (Brassica chinensis L.). The experiment was carried out using four amendments, Lime, Zeolite, Superphosphate, and Biochar, at two different ratios; M1: at the ratio of 47:47:5:1, and M2 at the ratio of 71:23:5:1, respectively. Moreover, both M1 and M2 were enriched at four levels (T1: 0.5%; T2: 1%; T3: 2%; T4: 4%). Results showed that compared with CK (Cd enriched soils), the yield of rice under treatments of M1T1 and M2T1 increased by 8.93% and 8.36%, respectively. While the biomass (fresh weight) of pak choi under M1 and M2 amendments increased by 2.52-2.98 times and 0.76-2.89 times respectively, under enrichment treatments T1, T2, and T3. The total Cd concentrations in rice grains treated with M1T3 and M2T3 decreased by 89.25% and 93.16%, respectively, compared with CK. On the other hand, the total Cd concentrations in pak choi under M1T3 and M2T2 decreased by 92.86% and 90.23%, respectively. The results showed that soil pH was the main factor affecting Cd bioavailability in rice and pak choi. The Variance partitioning analysis (VPA) of rice and pak choi showed that soil pH was the most significant contributing factor. In the rice season, the contribution of soil pH (P) on Cd bioavailability was 10.14% (P=0.102), and in the pak choi season, the contribution of soil pH was 8.38% (P=0.133). Furthermore, the abundance of ammonia oxidation and denitrifying microorganisms had significantly correlation with soil pH and exchange Cd. In rice season, when the enrichment level of amendments increased from 0.5% (T1) to 2% (T3), the gene abundance of AOA, AOB, nirK, nirS and nosZ (І) tended to decrease. While in pak choi season, when the enrichment level increased at the level of 0.5% (T1), 1% (T2), and 2% (T3), the gene abundance of AOB, nirS, and nosZ (І) increased. Additionally, the gene abundance of AOA and nirK showed a reduction in the pak choi season contrasting to rice. And the mixed amendment M2 performed better at reducing Cd uptake than M1, which may have correlation with the ratio of lime and zeolite in them. Finally, we conclude that between these two amendments, when applied at a moderate level M2 type performed better than M1 in reducing Cd uptake, and also showed positive effects on both gene abundance and increase soil pH.

Wood bioash effect as lime replacement in the stabilisation of different clay subgrades

ABSTRACT The possibility of applying wood ash (WA), as a partial replacement of lime in subgrade stabilisation of clay soil of eastern Croatia, was explored in this study. The optimal ratios of lime substitution by WA were determined for the stabilisation of local clays of different plasticity. The results show that WA, a local available alternative material, can be used as a partial replacement of lime in the stabilisation of researched local clays for use in embankments and subgrades. The substitution of lime by WA resulted in similar changes in soil plasticity, granulometry and compaction properties. The optimal substitution ratio of lime with WA in the stabilised mixtures depends on the degree of plasticity of the base soil. The lowest optimal substitution ratio was recorded (25–50%) for high-plasticity soil. For medium- and low-plasticity soil, 50–75% of lime can be replaced by WA, resulting in the same or better California Bearing Ratio (CBR) values than the reference mixture. The CBR values for all mixtures were 18.82–107.34%. With the addition of all binder compositions, linear swelling was reduced to less than 1%. However, some aspects of chemical composition of WA can present limitations to WA use.

What factors contribute to high mechanical strength of tabia? Case study of the tabia from coastal forts sites at Zhejiang, China

Tabia is one of the most widely used construction materials in ancient China. In this work, the tabia samples from three coastal defense fort sites at Zhejiang Province, China, we analyzed to determine their component composition and physiochemical properties. The results show that these tabia samples exhibited high compressive strength, which could be as high as 4–9 MPa. Furthermore, the systematic analysis demonstrated that the high compressive strength was related to the following factors: (1) a suitable mass ratio of sand, lime, and clay; (2) an appropriate sand particle size ratio; and (3) the formation of hydrated calcium silicate (C-S-H). Moreover, sticky rice was also detected in the tabia samples. These findings are fundamentally important, which could be beneficial to further study of the craftsmanship of the coastal defense forts and could further provide essential guidance for the protection and restoration of the tabia relics.

Experimental Reinforcement Agent for Damaged Walls of Payathonzu Temple Murals in Bagan, Myanmar

This study focuses on reinforcement agents for wall damage, such as cracks, breakage, or delamination, for mural paintings from the Payathonzu temple. Experiments were conducted with filling and grouting agents based on the reinforcing method. In the filling reinforcement experiment, different mixing ratios of lime to sand, and additives (jaggery, seaweed glue, and Primal SF-016) were used. In the grouting reinforcement experiment, the mixing ratio of lime and pozzolan was the same, and the additive types were identical to the filling reinforcement experiment. The filling reinforcement experiment showed that there were fewer physical changes such as contraction, with a greater mixing ratio of lime to sand, however, the compressive strength decreased as the mixing ratio increased. With additives, the change in volume of agent decreased and the compressive strength increased, which was especially prominent for jaggery and Primal SF-016. The grouting reinforcement experiment showed that there was a remarkable contraction with an increased amount of moisture that originates from the characteristic of grouting agents that requires flowability. With additives, the water content of the agent decreased, whereas the compressive strength and adhesion increased. Among the additives, Primal SF-016 exhibited the highest compressive strength, and seaweed glue exhibited the most considerable viscosity and adhesion. The study results showed that the characteristics of reinforcement agents vary according to the mixing ratio and additives of the filling and grouting agents. Therefore, it is necessary to selectively apply the mixing ratio and additives for different reinforcement agents considering the wall damage for conservation treatments.

Engineering properties evaluation of unfired sludge bricks solidified by cement-fly ash-lime admixed nano-SiO2 under compaction forming technology

This paper investigated the engineering properties of unfired sludge bricks (USB) made from dredged sludge and cement-fly ash-lime admixed nano-SiO2 binders under compaction forming technology. A series of laboratory tests were conducted to evaluate the effects of cement content, mass ratio of lime to fly ash (L/FA) and nano-SiO2 (NS) content on the physical, mechanical and thermal insulation performance of USB. Furthermore, scanning electron microscopy (SEM) and X-ray diffraction (XRD) tests were also performed to explore the microstructural properties of USB. The results indicated that the binder composed of 15% cement, 1% lime, 9% fly ash and 1.5% NS was recommended to replace 25% cement for preparing USB, which can increase 7-, 28- and 60-day compressive strength by 1.37, 12.94 and 23.30%, respectively. The bulk density of USB increased with the increase of cement and NS content, but decreased with the L/FA. The water absorption of USB decreased with increasing cement and NS content, but increased with the L/FA. The lime content used in USB should be less than 3%. The pH of USB decreased with increasing NS content, and tended to be stable as the NS content increased to more than 1.5%. The increase of cement and NS content had adverse effect on the thermal insulation performance, but this can be effectively improved by the inclusion of lime and fly ash. A positive linear relationship was achieved between thermal conductivity and bulk density. The microstructure analysis confirmed that the CSH and CAH gels were the main cementitious products inside the USB, and the calcite (CaCO3) may be responsible for the micro-cracks appeared in USB.

Feasibility and Carbon Footprint Analysis of Lime-Dried Sludge for Cement Production

Cement manufacturing and the treatment of sludge are considered both energy-intensive industries and major greenhouse gas (GHG) emitters. However, there are still few studies on comprehensive carbon footprint analysis for adding municipal sludge in the cement production. In this study, the lime-dried sludge blended with calcium oxide at the mass mixing ratio of 10% was utilized as raw material for the preparation of Portland cement. The chemical and physical properties of sludge were analyzed. A set of carbon footprint calculation methods of lime-drying treatment of sludge and reuse in cement kilns was then established to explore the feasibility of coprocessing lime-dried sludge in cement kilns. The results showed lime-dried sludge containing CaO, SiO2, Al2O3, and Fe2O3 was ideal for cement production as raw material. However, the water content of lime-dried sludge should be strictly limited. The lime-drying process presented the biggest carbon emission (962.1 kg CO2-eq/t sludge), accounting for 89.0% of total emissions. In the clinker-production phase, the lime-dried sludge as raw material substitute and energy source gained carbon credit of 578.8 and 214.2 kg CO2-eq/t sludge, respectively. The sludge used for producing cement clinker could reduce carbon emissions by 38.5% to 51.7%. The addition ratio of lime and stacking time in the sludge lime-drying process could greatly affect the carbon footprint of coprocessing lime-dried sludge in cement kiln.

Experimental study on improving the engineering properties of coarse grain sulphate saline soils with inorganic materials

Coarse grain soils are a good kind of embankment fill material. However, when they contain a high-level soluble salt, the engineering consequences can include salt expansion and collapsibility. The main objective of this study was to improve the salt expansion, collapsibility, and strength characteristics of coarse grain sulphate saline soils using inorganic binders and to provide an optimal proportion for the improvements. Coarse grain sulphate saline soils with 2% soluble salt contents were improved using different ratios of slaked lime, slaked lime-fly ash, and slaked lime-volcanic ash. Meanwhile, salt expansion tests, collapsibility tests, saturated unconfined compressive strength (SUCS) tests, and SEM tests were performed for the improved soils using different proportions. The results demonstrated that adding slaked lime, slaked lime-volcanic ash, or slaked lime-fly ash could not only effectively reduce the salt expansion amount, but also reduce the sensitive temperature range of the salt expansion. The deformation rate of salt expansion and collapsibility were <1% after adding >11% slaked lime or 15% slaked lime-volcanic ash (or fly ash). The 7 curing day SUCS of the improved soil was not <0.35 MPa. Compared with the strength of the slaked lime improved soil and the slaked lime-fly ash improved soil, the strength of the slaked lime-volcanic ash modified coarse grain sulphate saline soil was stronger. Also, the addition of volcanic ash could increase the strength gain rate in these improved saline soils. Furthermore, the feasibility and rationality of using inorganic binder to improve coarse grain sulphate saline soil were clarified by discussing the microstructure and improvement mechanism of coarse grain sulphate saline soil before and after improvement.