Early Neoproterozoic limestones from the Gwna Group, Anglesey

Limestone megaclasts up to hundreds of metres in size are present within the Gwna Group mélange, North Wales, UK. The mélange has been interpreted as part of a Peri-Gondwanan fore-arc accretionary complex although the age of deposition remains contentious, proposals ranging from Neoproterozoic to Early Ordovician. This paper uses strontium isotope chemostratigraphy to establish the age of the limestone blocks and thus provide a maximum age constraint on mélange formation. Results show that, although the carbonates are locally dolomitized, primary 87Sr/86Sr ratios can be identified and indicate deposition sometime between the late Tonian and earliest Cryogenian. This age is older than that suggested by stromatolites within the limestone and indicates that the limestone did not form as cap carbonate deposits

Oolitic limestone and marine sandstone gravel aggregate Early life concrete and aggregate freeze/thaw test for durability

Oolitic limestone is one type of limestone which formed during the Jurassic period and can be found in large deposits in many areas of England. It can be used as coarse aggregate for concrete construction, however due to its porosity, it requires additional cement to maintain compressive strength, when compared to marine gravel (sandstone) concrete. Since freeze/thaw durability is one of the most common problems in temperate countries, this paper investigates the freeze/thaw resistance of Oolitic limestone itself and when used as a coarse aggregate in concrete. The washed oolitic limestone was freeze/thaw tested to BS EN 1367 -1 :2007 and conclusions were drawn. Sixteen concrete cubes (100 mm3) were made, 8 using Oolitic limestone as a coarse aggregate and another 8 using marine gravel. Two cubes (1 Oolitic limestone, 1 marine gravel aggregate concrete) were used in a compressive strength test after 3 days of curing, to establish the strength at which the concrete was subjected to freeze/thaw action and the remaining 14 cubes were subject to freeze/thaw cycles, to a maximum of 56 cycles as informed by BS CEN/TR 15177:2006. Compressive strength, percentage mass lost and pulse velocity were compared and the results showed an equal ability to resist freeze/thaw damage when comparing the marine aggregate and oolitic limestone. Normally, the main role of coarse aggregate in concrete is just to act as a filler which determines strength. However in the case of Oolitic limestone, which is composed mainly of calcite (calcium carbonate), further studies should be made both to determine the mineralogy and its behaviour chemically when exposed to cement paste

A study of nano-particle based silane consolidants for Globigerina limestone

This STEPS funded study focuses on the application of hybrid and nanoparticle loaded hybrid silane consolidants for the treatment of 'Franka' type Globigerina Limestone. Consolidants act by gluing the deteriorated stone material to the underlying healthy stone (Dukes, 1972; Gutt, 1973; Alessandrini et al., 1975; Garrod, 2001). The consolidants evaluated in this work were a laboratory prepared hybrid silane based on a mixture of tetraethylorthosilicate (TEOS) and 3-(glycidoxypropyl) trimethoxysilane (GPTMS), the same hybrid consolidant loaded with silica nanoparticles and GPTMS-modified silica nanoparticles. In addition, a consolidant based on the hydrolysis product of TEOS was also tested. Prepared consolidants were applied to Globigerina Limestone test blocks by complete immersion. Untreated stone block were used as benchmarks. Following application of the consolidants, half of the treated limestone blocks were subjected to accelerated weathering. Non-weathered and weathered limestone blocks were then characterised by optical and electron microscopy and the stone colour before and after treatment with consolidants was assessed by a colorimetric technique. The pore size distribution before and after application of the different consolidant treatments was assessed by Mercury Intrusion Porosimetry. A water absorption by capillarity technique was also carried out to assess how the water uptake rate into the limestone alters with the different treatments. The mechanical properties of the consolidated limestone blocks were assessed by resistance to sodium sulfate crystallisation. Microscopy observations showed that the consolidants penetrated the stone to different extents depending on the consolidant and the method of application. The hybrid consolidant on its own led to yellowing of the limestone but the addition of nanoparticles to the hybrid (modified or not) appeared to help restore the original colour of the stone. The porosity of the limestone was only marginally affected by the different treatments but the somewhat hydrophobic nature of the consolidants led to a disruption in the capillary flow of water into the limestone.peer-reviewe

Mechanism of microstructural modification of the interfacial transition zone by using blended materials

Applying blended materials with finer particle size or high reactivity could be an effective and economic way for improving the microsturcture of interfacial transition zone (ITZ). In this study, the porosity characteristics of ITZ in concrete made with OPC and blended binders were determined quantitatively by using backscattered electron microscopy (BSE) image analysis and mercury intrusion porosimetry (MIP) measurements. This paper especially focused on the effects of slag and limestone filler on the thickness and pore structure of the ITZ. Results indicated that the porosity at each distance reduces with increasing limestone filler from 0 to 5%, and a significant increase is observed in the sample with 10% of limestone filler. The addition of 5% of limestone filler is able to densify the pore structure of both ITZ and bulk matrix. The reduction in pore volume in the range coarser than 100 nm contributed to the largest decrease in the total pores. Increasing the incorporation level of limestone filler to 10% resulted in an increase in the total porosity. The influences of slag on the porosity characteristics were highly dependent on the replacement level and the determined pore size regions. The addition of 35% of slag reduces the porosity at all distances and produces a denser microstructure both in the ITZ and bulk cement matrix. However, this improvement disappears when the substitution amount reaches to 70%. The incorporation of slag as a partial substitute for Portland cement tends to refine the pore structure

Morphological, chemical and mineralogical characterization of some soils developed on hard carbonate rocks in Sardinia

This preliminary note considers 19 profiles of Sardinian soils developed on hard limestone, dolomitic limestone and dolomite of different age and territorial condition, reporting on the description of the profiles and their physical, chemical and mineralogical characteristics. The results indicate that the soils examined belong to xeric subgroups of three orders: Entisols, Inceptisols and Alfisols. All the profiles show a clay texture and the clayey constituents are related to the degree of soil evolution

Ca-looping for postcombustion CO2 capture: A comparative analysis on the performances of dolomite and limestone

The low cost and wide availability of natural limestone (CaCO3) is at the basis of the industrial competitiveness of the Ca-looping (CaL) technology for postcombustion CO2 capture as already demonstrated by ~1Mwt scale pilot projects. A major focus of studies oriented towards further improving the efficiency of the CaL technology is how to prevent the gradual loss of capture capacity of limestone derived CaO as the number of carbonation/calcination cycles is increased. Natural dolomite (MgCa(CO3)2) has been proposed as an alternative sorbent precursor to limestone. Yet, carbonation of MgO is not thermodynamically favorable at CaL conditions, which may hinder the capture performance of dolomite. In the work described in this paper we carried out a thermogravimetric analysis on the multicyclic capture performance of natural dolomite under realistic regeneration conditions necessarily implying high calcination temperature, high CO2 concentration and fast transitions between the carbonation and calcination stages. Our study demonstrates that the sorbent derived from dolomite has a greater capture capacity as compared to limestone. SEM analysis shows that MgO grains in the decomposed dolomite are resistant to sintering under severe calcination conditions and segregate from CaO acting as a thermally stable support which mitigates the multicyclic loss of CaO conversion. Moreover, full decomposition of dolomite is achieved at significantly lower calcination temperatures as compared to limestone, which would help improving further the industrial competitiveness of the technology.Junta de Andalucía FQM-5735, TEP-7858, TEP-1900Ministerio de Economía y Competitividad FIS2011-25161, CTQ2011- 2762

Contrasting carbonate depositional systems for Pliocene cool-water limestones cropping out in central Hawke's Bay, New Zealand

Pliocene limestone formations in central Hawke's Bay (eastern North Island, New Zealand) accumulated on and near the margins of a narrow forearc basin seaway within the convergent Australia/Pacific plate boundary zone. The active tectonic setting and varied paleogeographic features of the limestone units investigated, in association with probable glacioeustatic sea-level fluctuations, resulted in complex stratigraphic architectures and contrasting types of carbonate accumulation on either side of the seaway. Here, we recognise recurring patterns of sedimentary facies, and sequences and systems tracts bounded by key physical surfaces within the limestone sheets. The facies types range from Bioclastic (B) to Siliciclastic (S) end-members via Mixed (M) carbonate-siliciclastic deposits. Skeletal components are typical cool-water associations dominated by epifaunal calcitic bivalves, bryozoans, and especially barnacles. Siliciclastic contents vary from one formation to another, and highlight siliciclastic-rich limestone units in the western ranges versus siliciclastic-poor limestone units in the eastern coastal hills. Heterogeneities in facies types, stratal patterns, and also in diagenetic pathways between eastern and western limestone units are considered to originate in the coeval occurrence in different parts of the forearc basin of two main morphodynamic carbonate systems over time

Biopigment Tracing of Mangrove Rhizophora mucronate Leaf an Bark Waste and Its Application for Batik Dyeing by Multiple Fixations

The purpose of this research is to determine the pigments in the bark and leaves of mangrove (Rhizophora mucronata), to analyze rate of color fastness in batik, level of consumer interest, and most effective pricing for the resulting batik products. The research was conducted between June 2015 and February 2016, and took place in Mangunharjo village, Tugu district, Semarang city, Indonesia. The pigment identification tests were performed in Laboratorium Terpadu Universitas Diponegoro, Indonesia. This research focused on the leaves and barks of mangrove plants. The leaves and barks were extracted to be used as dyeing agents, after which the batik fabrics were fixated using alum, limestone and lotus. This descriptive research employed UV-Vis spectrophotometry to identify pigment and Adobe Photoshop computer program to perform color fastness analysis. The result showed that chlorophyll is a pigment which contributes to the color green in leaves. Photochemical test results also show that the pigment associated to the blackish-green hue was tannin, andthat which was associated with red was flavonoid and quinone. The various colors were applied in batik dyeing process, which resulted in a range of color from yellow to dark brown. Color fastness test of batik dyed with mangrove-derived pigments on wash air dry, wash press dry, and wash sun dry using calico as fabric showed that alum and limestone fixated fabric had the least color fastness, while conversely, lotus-fixated fabric displayed good color retention. Levels of consumer interest naturally-dyed batik fabric by alum fixation was 20%. Of all the respondents, 46.67% showed interest in limestone-fixated batik, whereas 40% responded well with the lotus-fixated batik. Consumer acceptance levels for the mangrove-dyed batik fixated by alum, limestone, and lotus were 6.67%, 16.66% and 13.33% respectively. High consumer interest in fabric fixated by limestone and lotus was attributed to darker and stronger hues. The most effective price point suggested per 2.1 x 1 m of fabric was between IDR 200,000 to IDR 350,000