Showing papers on "Lime published in 2012"

Supplementary Cementitious Materials

Abstract: The current widespread use of calcium silicate or aluminate hydrate binder systems in the construction industry finds its roots in the Antique world where mixtures of calcined lime and finely ground reactive (alumino-)silicate materials were pioneered and developed as competent inorganic binders. Architectural remains of the Minoan civilization (2000-1500 BC) on Crete have shown evidence of the combined use of slaked lime and additions of finely ground potsherds to produce stronger and more durable lime mortars suitable for water-proof renderings in baths, cisterns and aqueducts (Spence and Cook 1983). It is not clear when and where mortar technology evolved to incorporate volcanic pumice and ashes as a functional supplement. A plausible site would be the Akrotiri settlement at Santorin (Greece), where archeological indications of strong ties with the Minoan culture were found and large quantities of suitable highly siliceous volcanic ash were present. This so-called Santorin earth has been used as a pozzolan in the Eastern Mediterranean until recently (Kitsopoulos and Dunham 1996). Evidence of the deliberate use of this and other volcanic materials by the ancient Greeks dates back to at least 500-400 BC, as uncovered at the ancient city of Kamiros, Rhodes (Efstathiadis 1978; Idorn 1997). In the subsequent centuries the technological knowledge was spread to the mainland (Papayianni and Stefanidou 2007) and was eventually adopted and improved by the Romans (Mehta 1987). The Roman alternatives for Santorin earth were volcanic pumices or tuff found in neighboring territories, the most famous ones found in Pozzuoli (Naples), hence the name pozzolan, and in Segni (Latium). Preference was given to natural pozzolan sources, but crushed ceramic waste was frequently used when natural deposits were not locally available. The exceptional lifetime and preservation condition of some of the most famous Roman buildings such as the Pantheon or the Pont du …

Lime Stabilization of Soils: Reappraisal

Abstract: Lime generally improves the performance of soils. However, some cases reported an adverse effect. To develop an understanding of the underlying mechanisms, a systematic study covering a wide range of plasticity and mineralogy of soils was carried out. Six different soil samples were reconstituted using two extreme types of soils, in other words, a montmorillonite rich expansive soil and a silica-rich non-expansive soil. The influence of lime stabilization on these soils was evaluated through determination of geotechnical properties such as liquid limit, plastic limit, swell, compressive strength, mineralogy, and microstructure. An optimum lime content beyond which the strength improvement decreased was found. This phenomenon is more prominently observed with silica-rich soils that form silica gel. As the silica gel is highly porous, when formed in large scale the strength gain from cementation is substantially countered by the strength loss from gel pores, giving rise to a visible reduction in ove...

Stabilization of a Clayey Soil with Fly Ash and Lime: A Micro Level Investigation

Abstract: Pavement structures on poor soil sub grades show early distresses causing the premature failure of the pavement. Clayey soils usually have the potential to demonstrate undesirable engineering behavior, such as low bearing capacity, high shrinkage and swell characteristics and high moisture susceptibility. Stabilization of these soils is a usual practice for improving the strength. This study reports the improvement in the strength of a locally available cohesive soil by addition of both fly ash and lime. Analysis using X-ray diffraction, scanning electron microscopy, coupled with energy dispersive spectroscopy, thermal gravimetric analysis, zeta potential and pH value test was carried out in order to elucidate the stabilization mechanism. The micro level analysis confirmed the breaking of montmorrillonite structure present in the untreated clay after stabilization. In the analysis, it was also confirmed that in the stabilization process, pozzolanic reaction dominated over the cation exchange capacity.

Design of green concrete made of plant-derived aggregates and a pumice-lime binder

Abstract: The use of particles from agricultural lignocellulosic resources in concrete gives it desirable environmental and multiphysics qualities. In this study, parallels are drawn between particles derived from hemp and sunflower stems, in terms of their morphological and physical properties. A pumice–lime binder is proposed as an alternative to the traditional cement or lime based solutions for both environmentally friendly and mechanical qualities. Compaction is applied during casting and its effects on mechanical properties are analysed. A principal finding of this study is that the hemp and sunflower materials show large similarities in terms of morphology and mechanical performance of the resulting concrete. The pumice–lime binder provides desirable properties even with raw pumice sand, which represent 90% of the binder mass proportion. Compaction level during casting induces an orthotropy, even with low plant content, and increases the compressive strength. A simple analytical model using Powers’ equation is proposed to predict plant concrete compressive strength with low plant quantities.

Effect of Calcium on Geopolymerization of Aluminosilicate Wastes

Abstract: The effect of calcium hydroxide on the mechanical and microstructural characteristics of geopolymer produced from alkaline activation of aluminosilicate wastes produced from demolition works were investigated. Demolition wastes are coarse aggregates, including waste concrete and demolished walls with cementing binder, both passing a sieve of 90 µm. A trial was carried out by making a mix containing demolished walls/waste concrete in the ratio of 60/40 % by weight and other mixes having a hydrated lime content of 0–25% of the dry weight as a partial replacement for demolished walls. Half of the waste concrete was substituted with metakaolin, produced by firing kaolin at 800°C for 3 h. The alkaline activators used were sodium hydroxide and sodium silicate in the ratio of 3∶3 % by weight of the dry weight. Curing of the geopolymer mixes was performed at ambient temperature (23°C) in tap water and under a mild temperature of 40°C [100% relative humidity (RH)]. Drying treatment at 80°C for 24 h was carried ou...

Effects of Fillers on Properties of Asphalt-Concrete Mixture

Abstract: The role of filler on the mechanical performance of asphalt-concrete mixture was investigated. Three wearing course (W3B) mixtures incorporating granite, hydrated lime, and kaolin as filler fractions were evaluated by the Marshall mix design method to determine their optimum asphalt content. The use of hydrated lime or kaolin as a filler requires more asphalt because of their relatively higher specific surface area. The highest stiffness performance was found for W3B-hydrated lime, followed by W3B-granite, and W3B-kaolin mixtures. W3B-hydrated lime and W3B-kaolin mixtures exhibited higher deformation resistance than that of W3B-granite mixture. The results showed that the presence of filler in an asphalt-concrete mixture affects the mixture’s performance in three ways: filler influences the amount of asphalt content, filler affects the workability during mixing and compaction, and the resultant properties of asphalt-filler mastic contribute to the mixture’s performance. The results show that the properties of the filler determine its interaction with asphalt and its contribution to the mixture’s performance.

Solidification/stabilization of dredged marine sediments for road construction

Abstract: Cement/lime-based solidification is an environmentally sound solution for the management of dredged marine sediments, instead of traditional solutions such as immersion. Based on the mineralogical composition and physical characteristics of Dunkirk sediments, the effects of cement and lime are assessed through Atterberg limits, modified Proctor compaction, unconfined compressive strength and indirect tensile strength tests. The variation of Atterberg limits and the improvement in strength are discussed at different binder contents. The potential of sediments solidified with cement or lime for road construction is evaluated through a proposed methodology from two aspects: I-CBR value and material classification. The test results show the feasibility of solidified dredged sediments for beneficial use as a material in road construction. Cement is superior to lime in terms of strength improvement, and adding 6% cement is an economic and reasonable method to stabilize fine sediments.

Ultrasound Assisted Lime Pretreatment of Lignocellulosic Biomass toward Bioethanol Production

Abstract: The present study acquaints optimization of ultrasound assisted lime pretreatment to reduce the time of lime pretreatment. The study was conducted on three lignocellulosic biomass materials, Areca nut husk (Areca catechu), bon bogori (Ziziphus rugosa), and moj (Albizia lucida) available in Northeast India, exploiting ultrasound for the pretreatment of lignocellulosic biomass along with lime augments the delignification ratio. The present study reports removal of 68% (bon bogori), 65% (Areca nut husk), and 64% (moj) of the lignin present in the naive lignocellulosic fiber with good recovery of total solid and fermentable sugars, respectively. The simultaneous saccharification and fermentation (SSF) process for the production of bioethanol was also carried out using baker’s yeast. The yield of ethanol was found to be in the range from 0.32 to 0.43 for all the ultrasound assisted lime pretreated biomasses.

Microwave pretreatment for enzymatic saccharification of sweet sorghum bagasse

Abstract: Pretreatment of sweet sorghum bagasse (SSB) through microwave radiation was evaluated at four lime doses (0, 0.1, 0.15, and 0.2 g/g SSB), two water content of 10 or 20 ml/g SSB, and three exposure times as 2, 4, and 6 min. Optimal pretreatment condition was identified as 0.1 g lime and 10 ml water per g SSB in 4 min. Under this condition, sugar yield of 32.2 g/100 g SSB (equivalent to 52.6% of maximal potential sugars) was achieved. With the same water content and exposure time, but without lime, sugar yield of 39.8 g/100 g SSB (equivalent to 65.1% of maximal total sugars) was observed. The higher sugar recovery without lime was mainly due to high sugar release during pretreatment. But with lime, sugar degradation took place, which resulted in less sugar yield though lime did make cellulose more accessible to enzymes as evidenced by higher percentage of increase of total reducing sugars during enzymatic hydrolysis. Results from this study were strongly supported by FTIR and SEM images. Overall, in a very short time and simple setup, microwave radiation shows great promise to be a leading pretreatment technique for SSB.

Effect of the combination of lime and natural pozzolana on the compaction and strength of soft clayey soils: a preliminary study

Abstract: Soft soil stabilization has been practised for quite some time by mixing additives, such as cement, lime and fly ash to the soil to increase its strength. However, there is a lack of investigations on the use of natural pozzolana alone or combined with lime for ground improvement applications. An experimental programme was undertaken to study the effect of using lime, natural pozzolana or a combination of both on the geotechnical characteristics of soft soils. Lime or natural pozzolana was added to soft soils at ranges of 0–10% and 0–20%, respectively. In addition, combinations of lime–natural pozzolana were added to soft soils at the same ranges. Test specimens were subjected to compaction tests, shear tests and unconfined compression tests. Specimens were cured for 1, 7, 28 and 90 days, after which they were tested for unconfined compression tests. Based on the favourable results obtained, it can be concluded that the soft soils can be successfully stabilized by the combined action of lime and natural pozzolana. Since natural pozzolana is much cheaper than lime, the addition of natural pozzolana in lime–soil mix may particularly become attractive and can result in cost reduction of construction.

Microstructural and Mineralogical Characterization of Clay Stabilized Using Calcium-Based Stabilizers

Abstract: The properties of clays can be significantly improved by treating with calcium-based stabilizers (or additives) such as hydrated lime (or lime), Portland cement, cement kiln dust (CKD), and class C fly ash (CFA). In the presence of water, the calcium ions released from these stabilizers reduce the thickness of double diffused layer through cation-exchange and flocculation-agglomeration reactions. This is primarily responsible for improvement in workability through reduction of adsorbed water and decrease in plasticity index. In longterm, pozzolanic reactions occur between the calcium ions of the stabilizer and the silica and alumina of the clay minerals resulting in the formation of cementitious products such as calcium-silicate-hydrates (C-S-H), calcium-aluminate-hydrates (C-A-H), and calciumaluminum-silicate-hydrates (C-A-S-H). The reaction may be written as: