• Title/Summary/Keyword: pumice

Search Result 95, Processing Time 0.027 seconds

The effects of different cement dosages, slumps and pumice aggregate ratios on the freezing and thawing of concrete

  • Turkmen, Ibrahim;Demirboga, Ramazan;Gul, Rustem
    • Computers and Concrete
    • /
    • v.3 no.2_3
    • /
    • pp.163-175
    • /
    • 2006
  • This research was conducted to determine effect of pumice aggregate ratio, cement dosage and slumps on freeze-thaw resistance, density, water absorption and elasticity of concrete. In the first batch, $300kg/m^3$ cement dosage were kept constant and pumice ratios were changed as 25%, 50%, 75% and 100% of replacement for normal aggregate by volume for $3{\pm}1cm$, $5{\pm}1cm$ and $7{\pm}1cm$ slumps. Other batches were prepared with $200kg/m^3$, $250kg/m^3$, $350kg/m^3$, $400kg/m^3$ and $500kg/m^3$ cement dosages and 25% pumice aggregate +75% normal aggregate at a constant slump. Test results showed that when pumice-aggregate ratio decreased the density and freeze-thaw resistance of concretes increased. With increasing of cement dosage in the mixtures, density of the concretes increased, however, freeze-thaw resistance of concretes decreased. Water absorption of the concrete decreased with increasing cement dosage but increased with the pumice ratio. Water absorption of the concrete also decreased after freeze-thaw cycles. Freeze-thaw resistance of concretes was decreased with increasing the slumps.

Synthesis of magnetite iron pumice composite for heterogeneous Fenton-like oxidation of dyes

  • Cifci, Deniz Izlen;Meric, Sureyya
    • Advances in environmental research
    • /
    • v.9 no.3
    • /
    • pp.161-173
    • /
    • 2020
  • The removal of two dyes, namely Methylene Blue (MB) and Reactive Brillant Red (RR) from aqueous solution was investigated using magnetite iron coated pumice (MIP) composite in the Fenton-like oxidation process. A weight ratio of 2.5 g (with the molar ratio of Fe3+ to Fe2+ to be 2) (5%) of iron to the total pumice (50 g) was enabled during synthesis of catalyst. Surface composition and characteristics of the catalyst were assessed by SEM-EDX, FT-IR, Raman spectral analysis. The effect of the amount of pumice solely used or MIP, H2O2 concentration, pH and initial concentration of MB or RR dyes on Fenton-like process efficiency was investigated. EDAX spectrums of pumice and MIP showed that oxygen and silisium are the major elements. The Fe content of MIP increased to 2.24%. SEM, FT-IR and Raman spectrums confirmed the impregnation of Fe on pumice surface. The experimental results revealed that high removal rates of dyes could be obtained using MIP that demonstrated a higher stability for removal of MB dye. pH affected the removal efficiency of both dyes and the degradation of both dyes was sharply dropped when pH was increased above 4. The removal of dyes did not significantly change with increasing H2O2 concentration. Degradation rates of both MB and RR dyes increased 3.3 and 2.8 times with the use of MIP compared to pumice alone, respectively. Furthermore, MIP enabled a good removal efficiency at higher dye concentrations. It can be emphasized that MIP composite can be used in the heterogeneous Fenton-like systems considering the economic and easily separation aspects.

Bond behavior of lightweight concretes containing coated pumice aggregate: hinged beam approach

  • Beycioglu, Ahmet;Arslan, Mehmet E.;Bideci, Ozlem S.;Bideci, Alper;Emiroglu, Mehmet
    • Computers and Concrete
    • /
    • v.16 no.6
    • /
    • pp.909-918
    • /
    • 2015
  • This paper presents an experimental study for determining the bond performance of lightweight concretes produced using pumice aggregate coated with colemanite-cement paste. For this purpose, eight hinged beam specimens were produced with four different concrete mixtures. 14 mm deformed bars with $10{\Phi}$ development lengths were selected constant for all test specimens. All the specimens were tested in bending and load-slip values were measured experimentally to determine the effect of colemanite-cement coated pumice aggregate on bond performances of lightweight concretes. Test results showed that, colemanite-cement coated pumice aggregate increases compressive strength and bond performance of the lightweight concretes, considerably.

Optimization of methylene blue adsorption by pumice powder

  • Cifci, Deniz Izlen;Meric, Sureyya
    • Advances in environmental research
    • /
    • v.5 no.1
    • /
    • pp.37-50
    • /
    • 2016
  • The main objective of this study is to evaluate adsorptive removal of Methylene Blue (MB) dye from aqueous solution using pumice powder. The effects of pH, adsorption time, agitation speed, adsorbent dose, and dye concentrations on dye adsorption were investigated. Process kinetics and isotherm model constants were determined accordingly. The results showed that adsorbent dose, dye concentration and agitation speed are the important parameters on dye adsorption and the removal of MB did not significantly change by varying pH. A total adsorption process time of 60 min was observed to be sufficient to effectively remove 50 mg/L MB concentration. The MB adsorption data obeyed both pseudo first order and second order kinetic models. Adsorption of MB by pumice fitted well both Langmiur and Freundlich isotherms ($R^2{\geq}0.9700$), except for 150 rpm agitation speed that system fitted only Langmiur isotherm. The results of this study emphasize that pumice powder can be used as a low cost and effective adsorbent for dye removal.

Physical and Mechanical Properties of Expanded Polystyrene Bead Concrete (팽창 폴리스틸렌 비드 콘크리트의 물리.역학적 특성)

  • 민정기;김성완;성찬용
    • Magazine of the Korean Society of Agricultural Engineers
    • /
    • v.38 no.6
    • /
    • pp.83-95
    • /
    • 1996
  • The normal cement concrete is widely used material to build the construction recently, but it has a fault to increase the dead load on account of its unit weight is large compared with strength. So, main purpose of this study was to establish the physical and mechanical properties of lightweight concrete using expanded polystyrene bead on fine aggregate and natural gravel, expanded clay and pumice stone on coarse aggregate. The test rusults of this study are summarized as follows; 1. The water-cement ratio of concrete using pumice stone was larger than that of the concrete using natural gravel and expanded clay. 2. The unit weights of concrete using pumice stone and expanded caly were shown less than 1,000g/$m^3$. 3. The compressive strengths of all types were shown less than 60kg/$cm^2$, tensile and bending strengths were shown less than l3kg/$cm^2$ and 3lkg/$cm^2$$^2$, respectively. 4. The pulse velocity of concrete was shown similar with using natural gravel and pumice stone, and shown the lowest using pumice stone. 5. The dynamic modulus of elasticity of concrete was shown considerably smaller, and shown the lowest using pumice stone. 6. The static modulus of elasticity of concrete using expanded clay and pumice stone were shown considerably smaller, and shown 22% ~29% as compared with the dynamic modulus of elasticity. 7. The stress-strain curves of concrete were shown similar, generally. And the curves were repeated at short intervals increase and decreased irregularly.

  • PDF

Effects of various CLEAN-UP techniques on enamel surface roughness (수종의 CLEAN-UP technique이 법랑질 표면거칠기에 미치는 영향)

  • CHO, Sang-Wan;KWON, Oh-Won
    • The korean journal of orthodontics
    • /
    • v.27 no.5 s.64
    • /
    • pp.791-800
    • /
    • 1997
  • Sixty premolars extracted for orthodontic treatment were divided into four groups, and the residual resin was removed with four different rotary finishing instruments at a fixed speed of $18,500{\pm}300 rpm$ on the low speed handpiece. The instruments were G1; No.169L carbide fissure bur, G2: No.2 round bur, G3; No.4 round bur, G4: No.8 round bur. Then, the enamel received a S-second polishing with a rubber cup and a pumice. To find the extent of loss on the enamel at this point, prophylaxis was done with the rubber cup and pumice prior to bonding of the bracket(P1) and removal of residual resin by means of appropriate procedure applicable to each respective group(P2) followed. The final polishing was done with the rubber cup and pumice(P3), and the enamel surface roughness was measured each by the surface measuring instrument. The whole process was observed under a scanning electron microscope to gain the following results: At P2, the enamel surface roughness in G1 showed most smoothly with $2.60{\pm}0.55{\mu}m;\;in\;G2,\;3.24{\pm}0.80{\mu}m;\;in\;G3,\;3.44{\pm}0.94{\mu}m;\;in\;G4,\;3.89{\pm}0.54{\mu}m$, the roughest. G2 and G3 showed no statistical significance(P>0.05). At P3, the enamel surface roughness in G1 showed most smoothly with $2.29{\pm}0.47{\mu}m;\;in\;G2,\;2.44{\pm}0.56{\mu}m;\;in\;G3,\;2.44{\pm}0.56{\mu}m;\;in\;G4,\;2.92{\pm}0.43{\mu}m$, the roughest. G1 vs G2, G3, and G2 vs G3 had no statistical significances(p>0.05). In all groups, P2 and P3 showed rougher in surface roughness than P1, and P2 rougher than P3(p<0.01). In a case of 5-second prophylaxis with the rubber cup and the pumice on a virgin, normal enamel, fine scratches were found under the scanning electron microscope. In all four groups, unremovable gouges remained even after polishing with the ubber and pumice; residual resin was not observed with naked eye when finished with the rubber and pumice, but the resin debris was observed under the scanning electron microscope.

  • PDF

Adaptive method for the purification of zinc and arsenic ions contaminated groundwater using in-situ permeable reactive barrier mixture

  • Njaramba, Lewis Kamande;Nzioka, Antony Mutua;Kim, Young-Ju
    • International Journal of Advanced Culture Technology
    • /
    • v.8 no.2
    • /
    • pp.283-288
    • /
    • 2020
  • This study investigated the purification process of groundwater contaminated with zinc and arsenic using a permeable reactive barrier with a zero-valent iron/pumice mixture. We determined the removal rates of the contaminants for 30 days. In this study, column reactor filled with the zero-valent iron/pumice reactive mixture was used. Experimental results showed that the mixture exhibited an almost complete removal of the zinc and arsenic ions. Arsenic was removed via co-precipitation and adsorption processes while zinc ions were asorbed in active sites.The purification process of water from the metal ionscontinued for 30 days with constant hydraulic conductivity because of the enhanced porosity of the pumice and interparticle distance between the zero-valent iron and pumice. Contaminants removal rates and the remediation mechanism for each reactive system are described in this paper.

Experimental investigation on the effect of cementitious materials on fresh and mechanical properties of self-consolidating concrete

  • Shariati, Mahdi;Rafie, Shervin;Zandi, Yousef;Fooladvand, Rouhollah;Gharehaghaj, Behnam;Mehrabi, Peyman;Shariat, Ali;Trung, Nguyen Thoi;Salih, Musab N.A.;Poi-Ngian, Shek
    • Advances in concrete construction
    • /
    • v.8 no.3
    • /
    • pp.225-237
    • /
    • 2019
  • Although applying self-consolidating concrete (SCC) in many modern structures is an inevitable fact, the high consumption of cement in its mixing designs has led to increased production costs and adverse environmental effects. In order to find economically viable sources with environmentally friendly features, natural pozzolan pumice and blast furnace slag in 10-50% of replacement binary designs have been investigated for experiments on the properties of fresh concrete, mechanical properties, and durability. As a natural pozzolan, pumice does not require advanced equipment to prepare for consumption and only needs to be powdered. Pumice has been the main focus of this research because of simple preparation. Also to validate the results, in addition to the control specimens of each design, fly ash as a known powder has been evaluated. Moreover, ternary mixes of pumice and silica fume were investigated to enhance the obtained results of binary mixes. It was concluded that pumice and slag powders indicated favorable performance in the high percentage of replacement.

Effect of pumice powder and artificial lightweight fine aggregate on self-compacting mortar

  • Etli, Serkan;Cemalgil, Selim;Onat, Onur
    • Computers and Concrete
    • /
    • v.27 no.3
    • /
    • pp.241-252
    • /
    • 2021
  • An experimental program was conducted to investigate the fresh properties, mechanical properties and durability characteristics of the self-compacting mortars (SCM) produced with pumice powder and Artificial Lightweight Fine Aggregate (aLWFA). aLWFA was produced by using fly ash. A total of 16 different mixtures were designed with a constant water-binder ratio of 0.37, in which natural sands were partially replaced with aLWFA and pumice powder at different volume fractions of 5%, 10% and 15%. The artificial lightweight aggregates used in this study were manufactured through cold bonding pelletisation of 90% of class-F fly ash and 10% of Portland cement in a tilted pan with an ambient temperature and moisture content. Flowability tests were conducted on the fresh mortar mixtures beforehand, to determine the self-compacting characteristics on the basis of EFNARC. To determine the conformity of the fresh mortar characteristics with the standards, mini-slump and mini-V-funnel tests were carried out. Hardened state tests were conducted after 7, 28 and 56 days to determine the flexural strength and axial compressive strength respectively. Durability, sorptivity, permeability and density tests were conducted at the end of 28 days of curing time. The test results showed that the pumice powder replacement improved both the fresh state and the hardened state characteristics of the mortar and the optimum mixture ratio was determined as 15%, considering other studies in the literature. In the aLWFA mixtures used, the mechanical and durability characteristics of the modified compositions were very close to the control mixture. It is concluded in this study that mixtures with pumice powder replacement eliminated the negative effects of the aLWFA in the mortars and made a positive contribution.

Petrological and Mineralogical Characteristics of Matrix of Pumice in Ulleung Island (울릉도 부석 기질의 암석.광물학적 특성)

  • Im, Ji-Hyeon;Choo, Chang-Oh;Jang, Yun-Deuk
    • Journal of the Mineralogical Society of Korea
    • /
    • v.24 no.3
    • /
    • pp.151-164
    • /
    • 2011
  • Mineralogical and petrological characteristics were investigated on matrix of dense gray, vesiculate gray, brown and black pumice in Ulleung Island by using XRD, FT-IR, XRF, SEM and thermal analysis. According to the analysis, most of pumice matrix are amorphous and include very small amount of sanidine and anorthoclase. Since the adsorption moistures, which commonly observed as O-H peak in FT-IR spectrum, are not identified in thermal analysis, it seems reasonable to conclude that content of the adsorption moisture has very low level. Although pumice has a large specific surface area, with long time elapsed after eruption, pumice matrix shows very low degree of hydration alteration due to the low level of water content. In SEM images, most surfaces of pumice show morphological characteristics such as various shapes of vesicle with wrinkled and thin walls resulted from ductile coalescence. Dense gray pumice formed in the initial stage includes small vesicles less than $15{\mu}m$ in size with subangular to angular shapes, free of ovoid vesicle. These characteristics are interpreted to have related to the hydrous environment derived from phreato-plinian eruption. Submicron particles observed as amorphous alumina silicate assemblages in vesicle surface are considered as particles sticked to the matrix surface through rapidly cooling process during ascent of alkali phonolitic magma. It indicates that these particles coexisted partly with crystallized alkali feldspar.