Effect of enzymes on plasticity and strength characteristics of an earthen construction material

Abstract In this study, a commercially available enzyme which is used popularly to improve sub-grade material for pavements was used as a potential stabilizer to improve soil properties used for earthen construction. As a preliminary study, the interaction of this enzyme with the soil was assessed by evaluating the plasticity and strength characteristics of enzyme treated soil with ageing. From the research findings, it was observed that with ageing, the liquid limit of soil decreased, while plastic and shrinkage limits increased, leading to reduced plasticity and shrinkage indices. The reduced plasticity and shrinkage indices indicate that soil has become relatively more volumetrically stable and less susceptible to crack formation. Further, strength characteristics under two different curing conditions were evaluated, and it was found that under sealed curing conditions, the treated soil had better compressive strength. The improvement of plasticity, shrinkage and strength characteristics due to the addition of enzymes can be advantageously used for development of lightly stabilized durable earthen construction material, and thus, eliminating the necessity of using conventional energy-intensive stabilizers. The findings from this study bring the immense potential of eco-friendly enzymatic stabilization in the development of modern sustainable earthen materials

A review of factors affecting undrained strength of fine-grained soils at consistency limits.

Estimation of remoulded undrained shear strength of fine-grained soils over a wide range of water content encountered in civil engineering practice is very essential for geotechnical design. Engineers predict the strength through simple index properties, namely consistency limits, rather than using strength evaluated using poor quality soil samples. Though shear strength at two characteristic water contents of practical significance, namely, liquid and plastic limit has found to vary quite significantly, for convenience, strength at these limits has been assumed to be unique. Since, liquid and plastic limit of any soil are nothing but water holding capacity at different states of consistency, undrained strength for different soils having varying liquid limit or plastic limit cannot be expected to have a unique value. In addition to this, recent findings have also brought out the fact that mobilization of strength of soils depends on clay mineralogy and particle gradation. Hence, considering un-drained strength of soils to be unique at any consistency limits of soil is not correct. A critical re-examination of factors contributing to the strength and reasons for its non-uniqueness is presented in this paper based on review of data from various well cited articles reported in the literature

Influence of soil gradation, proportion and combination of admixtures on the properties and durability of CSEBs

As it is well known that grading of soil influences the properties of compressed stabilized earth blocks (CSEBs), a need was felt to explore the possibility of using soils as found in nature for their production without physical modification or increasing the stabilizer content of 8% needed for their preparation as suggested in literature. This was made possible by the use of lime in combination with cement. Findings from this study would give flexibility in choosing soils of wider gradation as available in nature, thereby eliminating the need for blending with sand. This has a lot of practical significance and also application for the construction industry

Factors influencing undrained strength of fine-grained soils at high water contents

Understanding the undrained strength of fine-grained soils has been of interest to geotechnical researchers from many practical considerations. In several civil engineering applications, water content of soil is quite high being near or above the liquid limit of soils, and understanding the factors responsible for imparting the strength of soil at high water contents is of great significance. Recently, it has been reported in the literature that the shear strength of soils at these limiting water contents has significant variation. However, the reasons and the factors that probably influence for this variation have not been reported in the literature. This experimental investigation is an attempt in the direction of understanding the reasons for the variation in the undrained strength at higher limiting water content, namely liquid limit considering the various influencing factors like clay mineralogy and fine-sand content present in soil used for determining liquid limit. The results from this study are quite revealing and have been explained based on the mechanisms controlling the undrained strength at liquid limit

Correlation of compaction characteristics of natural soils with modified plastic limit.

Compaction characteristics of soils being very important from field application point of view, any attempt to develop correlation equation to predict the same should be rational and universally applicable. It has been reported in the literature that the plastic limit of soils bear a good correlation with their compaction characteristics. In this study, attempts have been made to use modified plastic limit to account for the proportion of fraction less than 425 μm as a parameter to correlate with the compaction characteristics of natural soils. The proposed correlation between the compaction characteristics of natural soils with their modified plastic are going to be handy tool for construction engineers in quickly assessing their suitability for compaction related purposes

Role of lime with cement in long-term strength of Compressed Stabilized Earth Blocks

Compressed Stabilized Earth Blocks (CSEBs) are manufactured using stabilizers to provide adequate compressive strength and durability, so, as to make them suitable as building blocks. Though cement is a popular stabilizer used in manufacture of CSEBs, no study has been reported utilizing lime in combination of cement. This experimental study on CSEBs prepared using lime as a replacement to cement in certain proportions has clearly brought out the effectiveness of lime with cement in improving the long-term build-up of strength better than using cement alone. It was observed that blocks prepared with optimum quantity of lime along with cement has led to continuous buildup of strength even beyond 2 years, whereas blocks prepared with cement alone and lesser quantity of lime than optimum quantity have not gained much strength after 6 months from the time of preparation of the blocks. The research findings show a need to relook at the grading of ingredients and quantity of stabilizers for achieving good building blocks. This would be an added benefit not only in reducing the cost of the blocks, but also has serious implications in terms of the reduction of energy consumed in the manufacture of blocks when done in large scale

Influence of soil gradation, proportion and combination of admixtures on the properties and durability of CSEBs

As it is well known that grading of soil influences the properties of compressed stabilized earth blocks (CSEBs), a need was felt to explore the possibility of using soils as found in nature for their production without physical modification or increasing the stabilizer content of 8% needed for their preparation as suggested in literature. This was made possible by the use of lime in combination with cement. Findings from this study would give flexibility in choosing soils of wider gradation as available in nature, thereby eliminating the need for blending with sand. This has a lot of practical significance and also application for the construction industry

Effect of Laser-Exposed Volume and Irradiation Position on Nonphotochemical Laser-Induced Nucleation of Potassium Chloride Solutions

Herein, we study the influences of the laser-exposed volume and the irradiation position on the nonphotochemical laser-induced nucleation (NPLIN) of supersaturated potassium chloride solutions in water. The effect of the exposed volume on the NPLIN probability was studied by exposing distinct milliliter-scale volumes of aqueous potassium chloride solutions stored in vials at two different supersaturations (1.034 and 1.050) and laser intensities (10 and 23 MW/cm2). Higher NPLIN probabilities were observed with increasing laser-exposed volume as well as with increasing supersaturation and laser intensity. The measured NPLIN probabilities at different exposed volumes are questioned in the context of the dielectric polarization mechanism and classical nucleation theory. No significant change in the NPLIN probability was observed when samples were irradiated at the bottom, top, or middle of the vial. However, a significant increase in the nucleation probability was observed upon irradiation through the solution meniscus. We discuss these results in terms of mechanisms proposed for NPLIN.Complex Fluid Processin

Design and Validation of a Droplet-based Microfluidic System To Study Non-Photochemical Laser-Induced Nucleation of Potassium Chloride Solutions

Non-photochemical laser-induced nucleation (NPLIN) has emerged as a promising primary nucleation control technique offering spatiotemporal control over crystallization with potential for polymorph control. So far, NPLIN was mostly investigated in milliliter vials, through laborious manual counting of the crystallized vials by visual inspection. Microfluidics represents an alternative to acquiring automated and statistically reliable data. Thus we designed a droplet-based microfluidic platform capable of identifying the droplets with crystals emerging upon Nd:YAG laser irradiation using the deep learning method. In our experiments, we used supersaturated solutions of KCl in water, and the effect of laser intensity, wavelength (1064, 532, and 355 nm), solution supersaturation (S), solution filtration, and intentional doping with nanoparticles on the nucleation probability is quantified and compared to control cooling crystallization experiments. Ability of dielectric polarization and the nanoparticle heating mechanisms proposed for NPLIN to explain the acquired results is tested. Solutions with lower supersaturation (S = 1.05) exhibit significantly higher NPLIN probabilities than those in the control experiments for all laser wavelengths above a threshold intensity (50 MW/cm2). At higher supersaturation studied (S = 1.10), irradiation was already effective at lower laser intensities (10 MW/cm2). No significant wavelength effect was observed besides irradiation with 355 nm light at higher laser intensities (≥50 MW/cm2). Solution filtration and intentional doping experiments showed that nanoimpurities might play a significant role in explaining NPLIN phenomena.Complex Fluid Processin