Effects of Aging on the Dry Shrinkage Cracking of Lime Soils with Different Proportions

In this study, the reasonable aging time of lime soils with different ratios was determined to investigate the effect of aging on the internal mechanism of the dry shrinkage cracking of lime soil. To this end, the effects of aging time, lime content, and particle size on the volume crack rate, expansion and shrinkage rate, particle size distribution, and pH were analyzed using a dry–wet cycle, screening, and pH tests. In addition, the changes in the particle structure of the samples and the formation of new substances were analyzed. The results revealed that the volume crack and expansion shrinkage rates of the sample initially decreased, and then stabilized with increasing aging time. In addition, the aging time of the sample increased with increasing lime content and particle size. Further, at the initial aging stage, the volume crack and expansion/shrinkage rates of the sample increased with increasing lime content and particle size. With an increase in the aging time, the pH increased and then decreased significantly to 0.57–1.1% at the reasonable aging time. These indicate that the pH exhibited a significant effect on the reasonable aging time, and this will provide useful insights for the restoration of lime soil sites.

Unfired Clay-Cork Granules Bricks Reinforced with Natural Stabilizers: Thermomechanical Characteristics Assessment

Cork is an ecological, natural, and renewable additive, an excellent thermal and acoustic insulator. All these attributes encourage its use in the building sector. Adding this additive to the Earth leads to a more lightweight composite with better thermal performance than the Earth alone. Unfortunately, the mechanical performance of this composite is degraded significantly, limiting its use in construction applications. The authors propose in this study to stabilize the clay-cork composite using natural stabilizers. A chemical stabilization was tested using local quick-lime, in addition to a physical stabilization using natural sheep-wool fibers. The primary purpose is to propose eco-friendly construction material with enhanced thermal and mechanical properties and the lowest environmental impact based on local and ecological raw materials to encourage more sustainable and low-energy constructions. First, physicochemical and mineralogical characterization of used clay was investigated. Then, an experimental investigation was conducted to identify the lime content that allows the optimal stabilization for the used clay. In this context, many different specimens of Bensmim soil stabilized with lime at six many contents 0, 10, 20, 30, 40, 50, and 70% were prepared and tested. The obtained results showed that the optimal lime content for the better stabilization of the used soil is about 30%. Next, an experimental study of thermomechanical properties was conducted on unfired clay bricks mixed with expended cork granules and stabilized by the addition of variable proportions of quick-lime 0, 10 and 30% and sheep-wool fibers 0, 1, and 2%. The mechanical performance of the specimens was investigated in terms of compressive and flexural strengths. At the same time, thermal quality was qualified through evaluating thermal conductivity using the steady-state Asymmetrical Hot Plate test method. The very encouraging experimental findings showed that using lime and sheep-wool fibers at the studied addition content resulted in lightweight composites with lower thermal conductivity and higher compressive and flexural strength than reference samples. The highest thermomechanical performances are obtained with clay-cork blocks reinforced with 30% lime content and 2% sheep-wool fibers. This block recorded values of 583 kg/m3, 0.155 W/m/K, 1.55 MPa, and 3.91 MPa, for bulk density, thermal conductivity, flexural and compressive strength respectively, compared to 765 kg/m3, 0.238 W/m/K, 0.96 MPa and 2.29 MPa for control samples. New material presents lightweight material for both improved thermal and mechanical qualities encouraging its use in building applications. Doi: 10.28991/cej-2021-03091778 Full Text: PDF

The Effects of Geocell Height and Lime Stabilization on Unpaved Road Settlements at Different Water Contents

In this study, lime stabilization and geocell reinforcement methods were investigated for a clayey subgrade of unpaved road at different water contents. This study is especially important in terms of determining the soil improvement method for road construction on wet lands. The effects of the geocell height (50, 100, 150, and 200 mm) and lime content (3, 6, and 12%) on the settlement of the subgrade soil at different water contents (25, 28, 30, 32, and 35%) were analyzed. Accordingly, a large scale plate loading test was designed, and it is utilized to achieve loading-settlement curves. The bearing capacity and modulus of subgrade (k) of soil were determined. It was detected that the geocell height and lime content have different effects at different water contents, and the modulus of subgrade reaction became stable beyond a constant height of the geocell. It was understood that none of these two improvements did not meet the Highways Technical Specifications. It is detected that at least these two improvement techniques are needed to be applied together to meet the specifications for the soil examined in this study.

Effect of hydrated lime on efflorescence formation

PurposeEfflorescence formation is very common in cement-based materials. In the case of mortar, efflorescence is more studied when only Portland cement is used as a binder. However, the repair of historical heritage, as well as the construction system of some countries, usually uses mortars composed of hydrated lime and Portland cement. This study aims to determine the influence of the hydrated lime content on the incidence of efflorescence in mortars.Design/methodology/approachMortars with 0%, 50%, and 100% lime/cement ratio were studied, using three different methods to accelerate efflorescence formation. The surface area of mortars affected by efflorescence was quantified by analysis using image software. Also, analysis of mercury intrusion porosity test, flexural tensile, compressive strength, absorption of water by capillarity, porosity, XRD and TGA was performed.FindingsMore efflorescence in mortars with a higher amount of lime in their composition was observed. The results show that the increase in the lime content reduces the flexural tensile and the compressive strength and increased the absorption of water by capillarity and the porosity of the mortars. The material formed by the efflorescence was calcium carbonate, proven by microstructural tests.Originality/valueThe results of greater efflorescence formation in mortars with lime are important to alert users who apply this type of material. Some type of protection must be done more rigorously for lime-cement mortars, especially concerning contact with water, since efflorescence tends to be faster for this type of material.

Appropriate Use of Lime in the Study of the Physicochemical Behaviour of Stabilised Lateritic Soil under Continuous Water Ingress

Lime stabilisation is one of the traditional methods of improving the engineering properties of lateritic soils for use as subgrade and foundation materials for the construction of road pavements and highway embankments. Understanding the mechanical performance of lime-stabilised lateritic subgrades in terms of their durability under continuous water ingress will improve environmental sustainability by conserving scarce natural resources and reducing the environmental impacts of repair and replacement of pavements. However, there are several conflicting reports on the durability of lime-stabilised soils subjected to continuous water ingress and harsh environmental conditions. Therefore, this paper evaluates the influence of leaching on the physicochemical behaviour and durability of lime-stabilised lateritic soil under continuous water ingress, simulating the typical experience in a tropical environment. Variations in the strength and durability of the lateritic soil at various lime contents (0, 2.5, 5, 7.5, 10, 15, and 20 wt.%) and soaking periods (3, 7, 14 and 28 days) were evaluated by performing the California bearing ratio tests before and after subjecting the lime-lateritic soil (LLS) samples to continuous leaching using two modified leaching cells. Furthermore, physicochemical analysis was performed to assess the variation of cation concentrations and changes in the physical properties of the pore fluid as the leaching time progressed from 3 to 28 days. The results show that the minimum strength reduction index of the soil corresponds to its lime stabilisation optimum (LSO). Electrical conductivity decreased monotonically and almost uniformly with an increase in leaching time, irrespective of lime content. So, too, was calcium concentration and to a lesser degree for pH and potassium concentration. Adverse changes in the physicochemical behaviour of the LLS samples occurred at lime contents below and slightly above the optimum lime content of the soil. Whereas permanent pozzolanic reactions occurred at lime contents above the LSO and thus resulted in a 45-fold increase in strength and durability. The results are significant for reducing the detrimental effect of the leaching-induced deterioration of flexible pavements founded on tropical floodplains.

Evaluation of Lime-Treated Lateritic Soil for Reservoir Shoreline Stabilization

Sedimentation is one of the major problems addressed by reservoir management, and requires extensive effort to control it. This paper aims to evaluate the efficiency of the soil–lime stabilization technique for reservoir shores. The treatment consisted of spraying hydrated lime in slurry form over the surface of a lateritic clay sample with 1, 2, and 4% lime solution and curing times of 1, 7, 28, and 56 days with air-drying and moist-room storage. In addition, a single test with less than 1% lime solution by weight percentage was carried out. The post-cured specimens were mapped with SEM and X-ray analyses. A wave flume test was performed in samples subjected to diverse conditions of lime content, type, and curing time. The results showed that the present technique produces a Ca-rich crust by carbonation rather than stabilizing it and that the lime content and type of curing generate improvements in soil loss reduction, but the curing time does not. The technique gave relative protection against water level variation and wave impacts, but it is necessary to consider a frequent application of lime on the lateritic soil.

Effect of Hydrated Lime on Indirect Tensile Stiffness Modulus of Asphalt Concrete Produced in Half-Warm Mix Technology

Half-warm mix asphalt (HWMA) mixtures can be produced at temperatures ranging from 100 °C to 130 °C, depending on the production methods used. The lowest mixing temperature can be achieved by using water-foamed bitumen. The mixture should be characterized by a long service life, defined by the resistance to permanent deformation and high stiffness modulus at temperatures above zero. It is therefore important to ensure the adequately high quality of the bitumen binder. Bitumen 50/70 was provided with appropriate quality foaming characteristics (expansion ratio, ER, half-life, t1/2) by adding a surface-active agent (SAA) at 0.6 wt % before foaming. Then asphalt concrete (AC) 8 S was designed and produced with the recommended water-foamed binder. Hydrated lime, an additive substantially affecting asphalt concrete mechanical parameters, was used at 0, 15, 30, and 45 wt % as a partial replacement for the limestone filler. The influence of the amount of hydrated lime on the content of voids, indirect tensile stiffness modulus at −10 °C, 0 °C, +10 °C, +20 °C, and +30 °C, and the resistance to permanent deformation was investigated. Statistical analysis of the test results showed the quantity of 30% to be the optimum hydrated lime content. The AC 8 S resistance to permanent deformation was determined at the optimum hydrated lime content. The comprehensive evaluation revealed a synergistic effect between bitumen 50/70, modified before foaming with 0.6 wt % SAA and 30 wt % hydrated lime as the limestone filler replacement, and the half warm mixture AC 8 S, in terms of the standard requirements and durability of the HWMA concrete in pavement applications.

Study on Restoration Materials for Historical Silty Earthen Sites Based on Lime and Starch Ether

The relics built with soil are called earthen archaeological sites. Many silt earthen sites exposed to natural environment get seriously damaged and thus require urgent restoration with suitable materials. Previously, lime and glutinous rice slurry were used in the construction of earthen sites. However, lime is usually used in clay, and glutinous rice pulp is difficult to prepare and use on a large scale. Therefore, in this study, starch ether was selected to replace glutinous rice pulp. Lime and starch ether were added to silt as single or double additives, respectively, to prepare the corresponding single-mixed and multiple-mixed modified soil samples. Furthermore, the direct shear test and compression test were carried out and the optimum content was determined. The strength and durability of optimum modified materials were compared with those of the original site soil. When the lime content was 9% or the concentration of starch ether solution was 5%, the shear strength and compression resistance ability of single-mixed modified soil were improved significantly. When lime content was 6% and starch ether solution was 5%, the strength of multiple-mixed modified soil was the best, and the maximum cohesion and internal friction angle were 51.1 and 3.37% higher than those of single-mixed soil, respectively. The strength and durability of the optimum modified soil were similar to or higher than those of the site soil. Thus, it is feasible and effective to use lime together with starch ether as restoration material for silty earthen sites.