Hiroyuki Miyauchi

Water Penetration of Cladding Components—Results from Laboratory Tests on Simulated Sealed Vertical and Horizontal Joints of Wall Cladding

Considerable work has focused on the deterioration of jointing compounds used to seal building joints; less emphasis has been placed on understanding the consequences of seal failure, particularly in respect to watertightness. Jointing products are subjected to different climate effects; some induce aging in the sealant that in time leads to deficiencies. Deficiencies may also come about from design faults or improper installation. Water entry at deficiencies may lead to a number of different deteriorating effects on the building fabric that may induce failure of other envelope components or premature failure of the joint sealant. Joints are also subjected to substantial wind driven rain loads, in particular atop multi-story buildings. The approach taken in this study focuses on determining the fault tolerance of joint systems of a simulated wall panel when subjected to watertightness tests that emulate heightened wind-driven rain loads. Vertical and horizontal joints of 20 mm width and sealed with a one-component polyurethane product were subjected to water spray rates ranging between 1.6 and 6 L/(min-m2) and pressures of up to 2 kPa. Faults introduced to the sealed joint and representative of deficiencies through which water could penetrate consisted of cracks of 2 to 16 mm long introduced along the sealant to substrate interface. For specific crack lengths, the crack size related to the degree of joint extension, the extension reaching a maximum of 10 % of joint width. Rates of water entry across the joint were determined for cracks of different lengths and size and the nature of water entry at deficient joints in which cracks were introduced was also examined. Results on vertical joints indicated that water readily enters open cracks in relation to the crack size, quantity of water present at the crack, and pressure across the opening. Water may also penetrate cracks of nonextended “closed” joints.

Evaluation on the Impact Resistant Performance of Fiber Reinforced Concrete by High-Velocity Projectile and Contacted Explosion

In this study we experimentally evaluated an impact resistant performance of fiber reinforced concrete in the moment of explosion by high-velocity projectile with emulsion explosive. To assess the impact resistance, we conducted the impact test of high-velocity projectile which reaches an impact speed of 350 m/s and the experiment of contact exploding emulsion explosive. As a result, bending and tensile performance depending on type of PVA, PE fiber (polyvinyl alcohol fiber, polyethylene fiber) and steel fiber affects destruction of rear side in the form of spalling. Destroying the backside of the concrete compressive strength compared to suppress the bending and tensile performance is affected. In addition, the experiment shows that the destruction patterns of concrete specimen producted by high velocity impact and contact explosion are significantly similar. Therefore, it is possible to predict the destruction patterns of specimens in the situation of contact explosion by high-velocity projectile.

Effect of Cross-Sectional Shapes of Polysulfide Sealant on Shear Fatigue Resistance to Sliding Joint Movement

The effect of cross-sectional shapes of polysulfide sealing beads on shear fatigue resistance to sliding joint movement was studied experimentally and analytically. Six kinds of sealing beads that were different in the depth of their concavity were repeatedly deformed by shear joint movement. Cracks appeared in surface near substrates or in the middle of surfaces in some specimens, and developed in parallel to substrates or in X-shape. The time to cracking became shorter for the specimen with deeper concave shape. To learn the reason for these results, the surface stresses of the beads were studied using a finite element method. It was concluded from both experimental and analytical results that a durable cross-section of a sealing bead to shear joint movement in rectangular or slightly concave shapes.

Evaluation of Sealed Joint Performance for the Selection of Sealants Suitable for Use in Autoclaved Lightweight Concrete Panels

The strength of autoclaved lightweight concrete (ALC) is evidently lower than that of normal concrete. Therefore, when movement occurs at a sealed joint between ALC panels, the sealant is required to deform and remain intact without damaging the ALC substrate. However, there is currently not sufficient information to permit evaluation of the expected performance of sealants applied to ALC substrates. In this study, static and dynamic tests were carried out in order to obtain an index that could be used to select the modulus of a sealant that can be expected to provide long-term performance when applied to an ALC substrate. To develop this index, an initial study was carried out in order to clarify actual joint movement between ALC panels of buildings; the expansion and contraction at the joint were measured, and shear joint movement was calculated based on the expected story-to-story drift of an external wall due to earthquake loads. Thereafter, in a subsequent stage of the study, five types of two-component polyurethane sealant products, of different elastic modulus, were subjected to tensile and shear tests from which the relationship between stress and the type of joint fracture was determined. The results from these tests revealed that when the stress is greater than 0.6 to 0.7 N/mm2, the ALC substrate is more easily fractured than the sealant. In a final stage of the study, the cyclic fatigue resistance of the same two-component sealants was evaluated using tensile and shear fatigue tests. Results from the fatigue tests indicated that the high modulus sealants lost adhesion from the ALC substrate at an early stage in the test. As well, the fatigue resistance of test specimens with joints having three-sided adhesion was lower than that of specimens having normally configured joints with adhesion on two sides of the sealant. Therefore, on the basis of results derived from all the studies, it was determined that a suitable sealant for use on ALC substrates is a sealant having a low modulus that is applied in the normal fashion as a two-sided joint.

Evaluation on the Blast Resistance of Fiber Reinforced Concrete

Recently, the damaged building and loss of life have been increasing by man-made disasters. In this study, the blast resistance performance of fiber reinforced concrete against explosion was evaluated by the emulsion explosive and AUTODYN. The concrete without fiber was penetrated by emulsion explosive of 4605 kJ/kg and its back side was fractured heavily. The concretes with PVA, PE and Steel fiber have a higher blast resistance than that of concrete without fiber. Consequentially, the blast resistance of concrete was analyzed from viewpoint of fracture mode by AUTODYN and it was concluded that the fiber content is a beneficial for the blast resistance performance of concrete.

Thermal Insulation Performance of Waterproofing Membrane System with a Multi-Layer Thermal Insulation Sheet

Thermal insulation performance of a multi-layered waterproofing membrane system with sandwich type of polyethylene foam and aluminum film was evaluated by using small specimen in the indoor environmental test chamber, and was compared with the effect of insulation sheet layers, the heat load on concrete substrate or the correlation with outdoor test results. The test specimens were 6 types; only concrete, single urethane system and some multi-layered systems with thermal insulation sheet. The indoor test was carried out with temperature cycles of to and to . The temperature of specimens were calculated by using the simplified calculation equation about the effect of season and specimen size, and the thermal insulation behavior between measurement value and the predicted value of had a good correlation. Also, the waterproofing system with multi-layered insulation sheets had a high insulation performance than that of existing systems, and can contribute to the reduction of heat load on concrete substrate and the saving energy.

Effect of Crack Width and Waterproof Membrane Coatings on the Chloride Ion Penetration of Mortar Substrate

The purpose of this study was to evaluate the salt damage resistance of waterproofing membrane in order to protect the mortar or concrete substrate. Polyurethane and acrylic coating membrane were used, and the salt water immersion test and the chloride ion concentration test were carried out experimentally. Also, the salt damage in mortar was analyzed by comparing with the permeability of each specimens. Waterproofing membrane have a high salt damage resistance more than only non-coated substrate, and prevented the penetration of chloride ion from non-crack to 0.3mm-crack specimens in 13 weeks-accelerating test. Finally, the membrane thickness for suppressing salt damage was estimated from viewpoint of its permeability.

Compressive Strength Properties of Geopolymer Using Power Plant Bottom Ash and NaOH Activator

When a new bonding agent using coal ash is utilized as a substitute for cement, it has the advantages of offering a reduction in the generation of carbon dioxide and securing the initial mechanical strength such that the agent has attracted strong interest from recycling and eco-friendly construction industries. This study aims to establish the production conditions of new hardening materials using clean bottom ash and an alkali activation process to evaluate the characteristics of newly manufactured hardening materials. The alkali activator for the compression process uses a NaOH solution. This study concentrated on strength development according to the concentration of the NaOH solution, the curing temperature, and the curing time. The highest compressive strength of a compressed body appeared at 61.24MPa after curing at for 28 days. This result indicates that a higher curing temperature is required to obtain a higher strength body. Also, the degree of geopolymerization was examined using a scanning electron microscope, revealing a micro-structure consisting of a glass-like matrix and crystalized grains. The microstructures generated from the activation reaction of sodium hydroxide were widely distributed in terms of the factors that exercise an effect on the compressive strength of the geopolymer hardening bodies. The Si/Al ratio of the geopolymer having the maximum strength was about 2.41.

Properties of Autogenous Shrinkage in High-Strength Mass Concrete According to Hydration Heat Velocity

The early-age properties and relationships between hydration heat and autogenous shrinkage in high-strength mass concrete are investigated through analysis of the history curves of hydration heat and autogenous shrinkage. To reduce the hydration heat velocity, micro encapsulated retarder (MR) that could retard cement reaction was applied. In the result of research, the hydration temperature and hydration heat velocity of high-strength mass concrete can be decreased with the reduction of size specimen and use of the retarder. A close relationship could be found between the hydration temperature and autogenous shrinkage; the higher the hydration heat velocity, the higher the autogenous shrinkage velocity and the greater the ultimate autogenous shrinkage.

EFFECT OF REINFORCING FABRICS TO FATIGUE RESISTANCE OF FLUID-APPLIED POLYURETHANE MEMBRANES AT JOINT OF SUBSTRATE

The effect of reinforcing fabrics to fatigue resistance of fluid-applied polyurethane membranes is described in the study. The membranes reinforced by the two kinds of reinforcing fabrics such as grass fiber and polyester fiber at various height in cross section were prepared. They were moved at three levels of movements of 0.5-1.0mm, 1.0-2.0mm, 2.5-5.0mm by the fatigue machine. It was made clear that the reinforcing fabrics improve the fatigue resistance of the membranes and the effect of them is noticeable for the membranes inserted at the lower position in cross section. It was also found out that fatigue resistance of the membranes is related to the property of reinforcing fabrics.