Showing papers on "Lime published in 2017"

Improvement of Problematic Soils with Biopolymer—An Environmentally Friendly Soil Stabilizer

Abstract: Problematic soils with high compressibility and low shear strength are often treated with traditional chemical stabilizing additives such as cement and lime to improve their engineering pro...

Accelerated carbonation and performance of concrete made with steel slag as binding materials and aggregates

Abstract: Steel slag has been used as supplementary cementitious materials or aggregates in concrete. However, the substitution levels of steel slag for Portland cement or natural aggregates were limited due to its low hydraulic property or latent volume instability. In this study, 60% of steel slag powders containing high free-CaO content, 20% of Portland cement and up to 20% of reactive magnesia and lime were mixed to prepare the binding blends. The binding blends were then used to cast concrete, in which up to 100% of natural aggregates (limestone and river sands) were replaced with steel slag aggregates. The concrete was exposed to carbonation curing with a concentration of 99.9% CO2 and a pressure of 0.10 MPa for different durations (1d, 3d, and 14d). The carbonation front, carbonate products, compressive strength, microstructure, and volume stability of the concrete were investigated. Results show that the compressive strength of the steel slag concrete after CO2 curing was significantly increased. The compressive strengths of concrete subjected to CO2 curing for 14d were up to five-fold greater than that of the corresponding concrete under conventional moist curing for 28d. This is attributed to the formation of calcium carbonates, leading to a microstructure densification of the concrete. Replacement of limestone and sand aggregates with steel slag aggregates also increased the compressive strengths of the concrete subjected to CO2 curing. In addition, the concrete pre-exposed to CO2 curing produced less expansion than the concrete pre-exposed to moist curing during the subsequent accelerated curing in 60 °C water. This study provides a potential approach to prepare concrete with low-carbon emissions via the accelerated carbonation of steel slag.

Phillipsite and Al-tobermorite mineral cements produced through low-temperature water-rock reactions in Roman marine concrete

Abstract: Author(s): Jackson, MD; Mulcahy, SR; Chen, H; Li, Y; Li, Q; Cappelletti, P; Wenk, HR | Abstract: Pozzolanic reaction of volcanic ash with hydrated lime is thought to dominate the cementing fabric and durability of 2000-year-old Roman harbor concrete. Pliny the Elder, however, in first century CE emphasized rock-like cementitious processes involving volcanic ash (pulvis) "that as soon as it comes into contact with the waves of the sea and is submerged becomes a single stone mass (fierem unum lapidem), impregnable to the waves and every day stronger" (Naturalis Historia 35.166). Pozzolanic crystallization of Al-tobermorite, a rare, hydrothermal, calcium-silicate-hydrate mineral with cation exchange capabilities, has been previously recognized in relict lime clasts of the concrete. Synchrotron-based X-ray microdiffraction maps of cementitious microstructures in Baianus Sinus and Portus Neronis submarine breakwaters and a Portus Cosanus subaerial pier now reveal that Al-tobermorite also occurs in the leached perimeters of feldspar fragments, zeolitized pumice vesicles, and in situ phillipsite fabrics in relict pores. Production of alkaline pore fluids through dissolution-precipitation, cation-exchange and/or carbonation reactions with Campi Flegrei ash components, similar to processes in altered trachytic and basaltic tuffs, created multiple pathways to post-pozzolanic phillipsite and Al-tobermorite crystallization at ambient seawater and surface temperatures. Long-term chemical resilience of the concrete evidently relied on water-rock interactions, as Pliny the Elder inferred. Raman spectroscopic analyses of Baianus Sinus Al-tobermorite in diverse microstructural environments indicate a cross-linked structure with Al3+ substitution for Si4+ in Q3 tetrahedral sites, and suggest coupled [Al3++Na+] substitution and potential for cation exchange. The mineral fabrics provide a geoarchaeological prototype for developing cementitious processes through low-temperature rock-fluid interactions, subsequent to an initial phase of reaction with lime that defines the activity of natural pozzolans. These processes have relevance to carbonation reactions in storage reservoirs for CO2 in pyroclastic rocks, production of alkali-activated mineral cements in maritime concretes, and regenerative cementitious resilience in waste encapsulations using natural volcanic pozzolans.

Stabilization of black cotton soil with lime and iron ore tailings admixture

Abstract: A laboratory study on the stabilization of black cotton soil (BCS) with up to 8% lime admixed with up to 10% iron ore tailing (IOT) by dry weight of soil compacted with British Standard light, BSL energy (relative compaction – 100%) was carried out to establish the soil improving potential of the lime – IOT blend. Tests carried out include index, compaction, strength and durability. Unconfined compressive strength (UCS), CBR (soaked and unsoaked condition) and resistance to loss in strength of specimen yielded peak values at 8% lime/8% IOT treatment. Microanalysis using scanning electron microscope (SEM) revealed that crystalline hydration products present in the optimally treated black cotton soil majorly contributed to the gain in strength. The batch equilibrium test results on the leaching potential of iron (Fe2+) from the BCS–lime–IOT mixture into the environment show that the desorbed value 0.272 mg/l of iron (Fe2+) concentration for 8% lime/8% IOT content falls within the permissible value of not more than 0.3 mg/l iron (Fe2+) concentration for drinking water recommended by the World Health Organisation (WHO) and Nigerian Industrial Standard (NIS). Based on strength criterion, an optimal 8% lime/8% IOT is recommended for treatment of black cotton soil for use as sub base material in the construction of low volume roads. The benefits of the application include reduction in the environmental impact of the disposal of iron ore tailings.

A green solar photo-Fenton process for the elimination of bacteria and micropollutants in municipal wastewater treatment using mineral iron and natural organic acids

Abstract: In this investigation, a new, green photo-Fenton process for wastewater treatment is proposed, involving the use of a natural iron source and natural additives, deriving from wastes, acting as iron chelators. The use of mineral iron as precursor in the photo-Fenton process, instead of iron salts, was still able to promote E. coli inactivation. Furthermore, the addition of four low weight organic acids (citric, tartaric, ascorbic and caffeic) showed a significant enhancement of the process, reaching total inactivation except for caffeic acid, which showed no significant effects. Two natural products, rich in the promising organic acids were tested as additives, lime and orange juice, plus their infusion. Lime-based additives showed better results compared to orange-based ones, which could be attributed to the excessive addition of organic matter in the orange systems. The formation of photoactive complexes with the mineral iron and the organic acids from the natural products induced the production of reactive species and ferrous ion, sustaining a homogeneous Fenton reaction. Finally, the proposed modified process was tested against different secondary effluents from a municipal wastewater treatment plant. Total bacterial inactivation was reached in the lime-based system, with no visible microorganism regrowth after 48 h. Additionally, the process was able to eliminate 40% of the total identified micropollutants of the secondary effluent reaching almost 50% of removal of the total effluent organic matter.

The effects of combinations of biochar, lime, and organic fertilizer on nitrification and nitrifiers

Abstract: Here, we report results from a field experiment investigating the application of biochars, lime, organic fertilizer, and their combinations Soil pH was increased by ameliorants Wheat biochar produced the largest increase, of approximately 2 pH units, and mixed treatment (one third rice husk biochar, one third lime, and one third organic fertilizer) also caused large increases, of almost 1 pH unit There was strong evidence that the ratio of ammonia-oxidizing archaea to ammonia-oxidizing bacteria (AOB) abundance greatly increased with decreased soil pH, indicating that soil pH was an important factor affecting the abundance of AOB High-throughput MiSeq sequencing showed that the soil ameliorants significantly increased the relative abundances of Nitrosomonas and Nitrospira Soil pH was an important determinant of the bacterial community composition and diversity Our study suggests that the ameliorants (biochar, lime, organic fertilizer, and their combinations) change soil nitrification by altering nitrifying bacteria abundance, diversity, and composition, caused by the changed soil pH

Effect of curing, capillary action, and groundwater level increment on geotechnical properties of lime concrete: Experimental and prediction studies

Abstract: Lime concrete and lime treatment are two attractive techniques for geotechnical engineers. However, researches have rarely been carried out to study the effects of moisture and capillary action due to increasing groundwater level on geotechnical properties of lime concrete. The aim of this study is to investigate the effects of curing time and degree of saturation on some of geotechnical properties of lime concrete such as unconfined compressive strength (UCS), secant modulus (Es), failure strain, brittleness index (IB), and deformability index (ID) using unconfined compression tests. First of all, geotechnical and chemical properties of used materials were determined. After curing times of 14 d, 28 d, 45 d, and 60 d in laboratory condition, the specimens were exposed to saturation levels ranging from 0 to 100%. The results showed that the moisture and curing time have significant effects on the properties of lime concrete. Based on the results of scanning electron micrograph (SEM) test, it was observed that the specimen was characterized by a rather well-structured matrix since both the filling of a large proportion of the coarse-grained soil voids by clay and the pozzolanic activity of lime led to retaining less pore water in the specimen, increasing the UCS and Es, and consequently resisting against swelling and shrinkage of the clay soil. Moreover, due to the pozzolanic reactions and reduction of water, by increasing the curing time and decreasing the degrees of saturation, UCS, Es, and IB increased, and ID decreased. Based on the experimental results, a phenomenological model was used to develop equations for predicting the properties in relation to the ratio of degree of saturation/curing time. The results showed that there was a good correlation (almost R2 > 90%) between the measured parameters and the estimated ones given by the predicted equations.

Effects of lime addition on geotechnical properties of sedimentary soil in Curitiba, Brazil

Abstract: The soil of the Guabirotuba geological formation (Parana Basin, Brazil) has physico-mechanical properties which are not suitable for its utilization in pavement construction, in protection of hillsides and slopes, or as shallow foundation support. Treatment of this soil by lime addition would improve its usability. The present context intends to determine the ratio between the splitting tensile strength (qt) and the unconfined compressive strength (qu) of clayey soil in the metropolitan region of Curitiba City, which has been treated with different lime contents and curing times. The control parameters evaluated include lime content (L), curing time (t), moisture content (w), and ratio of porosity to volumetric lime content (η/Lv). It was observed that the qt/qu ratio is between 0.17 and 0.2 in relation to the curing time, and an exponential relation exists between them. Meanwhile, the unconfined compressive strength of lime-treated soil was found to be approximately four times the initial value.

Use of quick and hydrated lime in stabilization of lateritic soil: comparative analysis of laboratory data

Abstract: A laboratory study was undertaken to evaluate and compare the stabilization effectiveness of different percentages (0, 2.5, 5, 7.5, 10%) of quick and hydrated lime when applied separately to locally available lateritic soil, a major soil group in the tropical and sub tropical regions. Performance evaluation experiments included: Atterberg limits, compaction, unconfined compression tests, California bearing ratio (CBR), swelling potential using CBR instrument and hydraulic conductivity. The soil mixtures used for unconfined compressive strength (UCS), CBR, swelling potential and hydraulic conductivity tests were compacted at optimum moisture content using the British standard light compactive effort and cured for 28 days. It was found that the quicklime caused the soil to have lower plasticity while hydrated lime yielded higher dry unit weight. Also, higher UCS especially at higher dosages (7.5 and 10%) was produced when soil sample was treated with quicklime. Similarly, the CBR values for quicklime sample clearly indicate that quicklime-stabilized soil have superior load bearing capacity. Finally, quicklime treated specimens reached slightly lower swelling values than the hydrated lime while no appreciable distinction in hydraulic conductivity values of specimens treated with the two types of lime was observed. From the foregoing results, quicklime is adjudged to have exhibited somewhat superior engineering properties and therefore creates a more effective stabilization alternative for the soil.

Stability of lime essential oil emulsion prepared using biopolymers and ultrasound treatment

Abstract: The objective of this study was to investigate the kinetic stability of lime essential oil emulsion using gum arabic (GA) and whey protein isolate (WPI) biopolymers as emulsifiers and stabilizers. ...

Enhancement of microalgae anaerobic digestion by thermo-alkaline pretreatment with lime (CaO)

Abstract: The aim of this study was to evaluate for the first time the effect of a thermo-alkaline pretreatment with lime (CaO) on microalgae anaerobic digestion. The pretreatment was carried out by adding different CaO doses (4 and 10%) at different temperatures (room temperature (25 °C), 55 and 72 °C). The exposure time was 4 days for pretreatments at 25 °C, and 24 h for pretreatments at 55 and 72 °C. Following, a biochemical methane potential test was conducted with pretreated and untreated microalgae. According to the results, the pretreatment enhanced proteins solubilisation by 32.4% and carbohydrates solubilisation by 31.4% with the highest lime dose and temperature (10% CaO and 72 °C). Furthermore, anaerobic digestion kinetics were improved in all cases (from 0.08 to 0.14 day- 1 for untreated and pretreated microalgae, respectively). The maximum biochemical methane potential increase (25%) was achieved with 10% CaO at 72 °C, in accordance with the highest biomass solubilisation. Thus, lime pretreatment appears as a potential strategy to improve microalgae anaerobic digestion.

Stabilization of Soft Kaolin Clay with Silica Fume and Lime

Abstract: Studies on chemically stabilised soils have shown that the effectiveness of treatment is largely dependent on the soil’s natural environment. This type of soil can be categorised as problematic due to its weak properties. At the preliminary stage, soft clay soil does not meet the requirements necessary for construction purposes because the entire load from the top of the building will be transferred to the underlying soil. This research considers the soil stabilisation of a soft clay soil (Kaolin S300) stabilised with various percentages of lime and 4% silica fume. The percentages of lime vary at 3, 5, 7 and 9%, while the percentage of silica fume is fixed at 4%. The main objective in this research is to improve the undrained shear strength of soft clay soil mixed with various percentages of lime (L) and 4% silica fume (SF). The properties of the soils were compared for kaolin only and for different percentages of lime mixed with 4% silica fume. The results showed that the optimum percentages of lime and ...

The short-term effects of liming on organic carbon mineralisation in two acidic soils as affected by different rates and application depths of lime

Abstract: Two acidic soils (initial pH, 4.6) with contrasting soil organic C (SOC) contents (11.5 and 40 g C kg−1) were incubated with 13C-labelled lime (Ca13CO3) at four different rates (nil, target pH 5, 5.8 and 6.5) and three application depths (0–10, 20–30 and 0–30 cm). We hypothesised that liming would stimulate SOC mineralisation by removing pH constraints on soil microbes and that the increase in mineralisation in limed soil would be greatest in the high-C soil and lowest when the lime was applied in the subsoil. While greater SOC mineralisation was observed during the first 3 days, likely due to lime-induced increases in SOC solubility, this effect was transient. In contrast, SOC mineralisation was lower in limed than in non-limed soils over the 87-day study, although only significant in the Tenosol (70 μg C g−1 soil, 9.15%). We propose that the decrease in SOC mineralisation following liming in the low-C soil was due to increased microbial C-use efficiency, as soil microbial communities used less energy maintaining intracellular pH or community composition changed. A greater reduction in SOC mineralisation in the Tenosol for low rates of lime (0.3 and 0.5 g column−1) or when the high lime rate (0.8 g column−1) was mixed through the entire soil column without changes in microbial biomass C (MBC) could indicate a more pronounced stabilising effect of Ca2+ in the Tenosol than the Chromosol with higher clay content and pH buffer capacity. Our study suggests that liming to ameliorate soil acidity constraints on crop productivity may also help to reduce soil C mineralisation in some soils.

Temperature-Accelerated Strength Development in Stabilized Marine Soils as Road Construction Materials

Abstract: Few studies have been reported about the effect of high curing temperature on the engineering properties of lime/cement-treated marine soils as alternative materials in road construction. L...