Akihiro Moriyoshi

A study of longitudinal cracking in asphalt pavement using CT scanner

ABSTRACT Longitudinal cracking has been increasingly observed on asphalt concrete pavement in the world. Although over 20 years have passed since the longitudinal cracking was observed on asphalt concrete pavement in Europe and Japan, it has been believed that it was developed from the top of pavement (top down cracking) for highway and pavement on orthotropic steel deck bridge. In this study, sample cores were extracted using a diamond cutter from pavement on an expressway and orthotropic steel deck bridge, which had been in service for five years or thirteen years, and showed no longitudinal cracking on the surface. The cores were analyzed for longitudinal cracking in each layer using a newly developed micro-focus CT scanner and a three-dimensional void analysis program in order to examine where it comes from. This paper showed longitudinal cracking on asphalt pavement develops not from the surface or the bottom of pavement but from within the asphalt pavement.

Evaluation of Damage to Asphalt Pavements using a Micro-focus CT Scanner and Three-dimensional Crack Analysis

ABSTRACT Longitudinal cracking has become increasingly common in asphalt concrete pavements worldwide since the introduction of modified bituminous binder to reduce rutting. This study extracted sample cores from two road sections (A and B, using a diamond cutter) from a motorway pavement which had been in service for five years and was showing no cracks (A) or longitudinal cracking on the surface (B). Further, cores for each layer of new and damaged sections were analyzed for the types of cracks using a newly developed micro-focus CT scanner (CT) and a three-dimensional (3D) crack analysis program and the study obtained failure limits (new concept) for each layer. The study found that the results can be applied to the pavement of both sections (A and B) in service, and that it is effective for a direct evaluation of pavement damage and can be applied to diagnose the degree of 3D damage in asphalt pavements.

Thermal properties of polymer concrete using glycerol methacrylate/styrene system at low temperature

This paper describes the results of thermal fracture test and flexural test of polymer concrete using glycerol methacrylate/styrene system (GM/St) as binder. This concrete can harden at low temperatures. The test also includes polymer concrete using unsaturated polyester resin(UP) and cement concrete. The thermal fracture test was carried out at a constant rate of cooling in order to record stress-temperature curves. It was concluded that the thermal stresses of GM/St mixtures cured at a low temperature were smaller than those in the same mixtures and UP mixtures cured at a normal temperature. Those polymer concretes could resist the thermal stress at low temperatures until -40°C and did not fracture. The flexural strengths of those are found constant regardless of temperatures. On the other hand, cement concrete was fractured by a smaller thermal change from the initial temperature than that of polymer mixtures.

Analysis of Contribution to SPM by Organic Matters Using High-Performance Liquid Chromatography (HPLC)

Most countries consider it is harmful for humans to inhale SPM of fine organic particles and elemental carbon less than 2.5 ~ in diameter,2). It is generally believed that organic matters in SPM are mainly composed of diesel exhaust particulate and soot from residential chimneys or industrial smokestacks.4). To determine the contribution ratios of several organic substances to SPM, we characterized SPM, diesel exhaust particulate (DEP), powdered summer radial tire, and bitumen, using high performance liquid chromatography, field desorption mass spectrometry and linear theory.

Damage analysis for flexible pavements at high and low temperatures using visco-elastic hybrid finite element method (FEM)

This paper describes different aspects of a stress and deformation damage analysis on field samples taken from Swiss and Japanese flexible pavements. Longitudinal cracking in the wheel path at high temperatures and thermal stresses at low temperatures were analyzed using visco-elastic hybrid Finite Element Method (FEM) together with relaxation moduli from relaxation tension tests at different temperatures. These relaxation moduli were determined with a modified test apparatus. It was concluded that in the case of these particular pavements, surface cracking was promoted by large horizontal shear forces due to tires of heavy trucks at high temperature and that thermal stresses due to thermal loading are small and almost the same for both Swiss flexible pavement sections. For the covering abstract see ITRD E117423.

EVALUATIONS OF COUNTERMEASURES AGAINST FLUCTUATING IMPACT NOISE EMANATING CONSTRUCTION MACHINE

土木工事用機械が発生する衝撃騒音は, 近隣住民などから多くの苦情が寄せられている. そのためこれら機械の騒音低減対策は, メーカ側が行う基礎研究に基づいた対策以外に, ユーザー側でも対策を行う必要に迫られている. しかし土木工事用機械の騒音は, 衝撃の加え方・被破砕物硬度などにより変動するため, ユーザーが騒音低減対策の有効性を評価するのは困難なことが多い. 本研究は, まず機械が発生する騒音の変動状態を明らかにすることにより, ユーザーでも可能な騒音低減対策評価法を考案した. 次に低減対策の効果を, 耳で聴き比べることが出来る「騒音低減対策評価用聴感シミュレーション法」を考案し, ユーザー自らが施した騒音低減対策の評価を容易にした.