Compressive Strength of OPS based Self-compacting Concrete Incorporated with Fly Ash under Elevated Temperature

The application of organic lightweight aggregates (LWA) such as rice husk, coconut shell and oil palm shell in concrete are gaining popularity. However, organic substances are generally flammable under elevated temperature. As such, it is important to understand the strength performance of concrete with organic LWA under elevated temperature. To this end, this paper presents the compressive strength and mass loss of lightweight self-compacting concrete (LWSCC) when exposed to elevated temperature. In the research, comparison was made between the LWSCC samples of the control mix and mix with 40% of fly ash replacement. The compressive strengths of these mixes at 28-day were 31.35 MPa and 22.77 MPa respectively while at 90-day age, they were 33.27 MPa and 25.04 MPa respectively. Compressive strength of LWSCC samples were studied experimentally under different temperature of 26°C (room temperature), 100°C, 200°C and 300°C respectively. The experimental results showed that there is significant reduction in concrete compressive strength within the temperature range of 100°C- 200°C. When temperature was increased to 300°C, the concrete experienced strength reduction of nearly 84% and 79% at 28-day and 90-day age respectively for control mix. When 40% fly ash is incorporated, the concrete experienced strength reduction of nearly 72% and 66% at 28-day and 90-day age respectively

Lightweight Self-compacting Concrete Incorporating Oil Palm Shell

This paper presents the results of an experimental research on the fresh concrete properties, density, compressive and tensile strength of lightweight self-compacting concrete (LWSCC) incorporating oil palm shell (OPS) as coarse aggregates. Three aspects of fresh concrete properties including passing ability, filling ability and segregation resistance of the mixtures have been investigated experimentally and tests were carried out in accordance with the procedures stated in European Federation of National Associations Representing for Concrete (EFNARC) guidelines. LWSCC with OPS as aggregates fulfils the fresh concrete properties requirements of the EFNARC guidelines. In this study, the compressive and tensile strengths have also been compared with granite based self-compacting concrete (SCC). It is observed that OPS based SCC achieved comparable compressive strength with granite based SCC. This research provides basic framework to develop mix design of lightweight self-compacting concrete by using OPS as aggregates. Other properties such as durability and fire resistance of the developed concrete are not considered in the present study and are recommended for future research. The experimental studies show that LWSCC, with the use of OPS as full replacement to normal weight aggregates (NWA), is potentially a sustainable alternative construction material. Its use also provides a cleaner and more beneficial solution in OPS disposal for oil palm industry. This research demonstrated that OPS can be successfully used to develop lightweight self-compacting concrete. This research will benefit the oil palm industry and the environment as a whole

The behavior of cold-formed steel and Belian hardwood self-tapping screw connections

Cold-formed steel has been widely used to retrofit and restore buildings, especially timber buildings. This is because the material is readily available, flexible, and lightweight. However, limited research is available with little assessment concerning cold-formed steel and hardwood connection performance. This paper experimentally studies the behavior of connections composed of self-tapping screws, cold-formed steel, and Belian hardwood. Five connection configurations were investigated, where the ultimate load-carrying capacity of the connection was determined through a sequence of shear and tension tests. The results showed that the connection failed by screw withdrawal under tension load. However, when loaded in shear, the failure mode of the connection changed from screw failure when the screw head was at the Belian side to screw rotation when the screw head was at the cold-formed steel side. The performance of current design guidance in Eurocode 5 was assessed by comparing the strengths obtained from the experiments. The comparison results showed that Eurocode 5 is conservative in predicting the performance of self-tapping screw connection composed of cold-formed steel and Belian hardwood in tension. However, it was overly conservative in predicting the shear strength of the connection as the design strengths are overestimated by around 60%

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Measurement of D*+/- meson production in jets from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

This paper reports a measurement of D*+/- meson production in jets from proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb^-1 for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range |eta| < 2.5. D*+/- mesons found in jets are fully reconstructed in the decay chain: D*+ -> D0pi+, D0 -> K-pi+, and its charge conjugate. The production rate is found to be N(D*+/-)/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*+/- mesons that carry a fraction z of the jet momentum in the range 0.3 < z < 1. Monte Carlo predictions fail to describe the data at small values of z, and this is most marked at low jet transverse momentum.Comment: 10 pages plus author list (22 pages total), 5 figures, 1 table, matches published version in Physical Review

Search for scalar top quark pair production in natural gauge mediated supersymmetry models with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV

The results of a search for pair production of the lighter scalar partners of top quarks in 2.05 fb-1 of pp collisions at sqrt(s) =7 TeV using the ATLAS experiment at the LHC are reported. Scalar top quarks are searched for in events with two same flavour opposite-sign leptons (electrons or muons) with invariant mass consistent with the Z boson mass, large missing transverse momentum and jets in the final state. At least one of the jets is identified as originating from a b-quark. No excess over Standard Model expectations is found. The results are interpreted in the framework of R-parity conserving, gauge mediated Supersymmetry breaking `natural' scenarios, where the neutralino is the next-to-lightest supersymmetric particle. Scalar top quark masses up to 310 GeV are excluded for the lightest neutralino mass between 115 GeV and 230 GeV at 95% confidence level, reaching an exclusion of the scalar top quark mass of 330 GeV for the lightest neutralino mass of 190 GeV. Scalar top quark masses below 240 GeV are excluded for all values of the lightest neutralino mass above the Z boson mass.Comment: 7 pages plus author list (20 pages total), 4 figures, 1 table, matches published PLB versio

Measurement of the production cross section of prompt j/psi mesons in association with a W (+/-) boson in pp collisions root s=7 TeV with the ATLAS detector

The process pp → W±J/ψ provides a powerful probe of the production mechanism of charmonium in hadronic collisions, and is also sensitive to multiple parton interactions in the colliding protons. Using the 2011 ATLAS dataset of 4.5 fb-1 of p s = 7TeV pp collisions at the LHC, the first observation is made of the production of W± + prompt J/ events in hadronic collisions, using W± → μ and J/ψ → μ+μ-. A yield of 27.4±7.5 -6.5 W± + prompt J/ψ events is observed, with a statistical significance of 5.1. The production rate as a ratio to the inclusive W± boson production rate is measured, and the double parton scattering contribution to the cross section is estimated. Copyright CERN, for the benefit of the ATLAS Collaboration