Direct Bonding of Sand and Gravel
The world is running short of sand, gravel, and limestone, which are the raw materials of concrete. We are developing a new technique to direct bind sand and gravel through a catalytic reaction, without the addition of any cement paste. This technique is expected to be suitable for application in lunar bases.
(clockwise from top left: silica sand, sand from Namib desert, simulated moon sand, and glass beads)
Media release: http://www.iis.u-tokyo.ac.jp/en/news/3531/
Materials created from vegetable and fruit waste
During harvesting, processing, and cooking of fruits and vegetables, plenty of inedible parts are produced. Occasionally, a large quantity of the edible part is not consumed because the size or the shape may be out of specification. Using these parts as raw materials and through the process of hot pressing, various materials have been developed that possess strength equivalent to construction materials. Furthermore, these materials have the added advantage of being edible, and can be seasoned with salt, sugar, and so on.
(From left to right: outer leaves of cabbage, and peels of orange and onion)
Media release: https://www.iis.u-tokyo.ac.jp/en/news/3567/
A former undergraduate student found a company: https://fabulajp.com/
Development of Botanical Concrete
A new construction material was developed by crushing concrete and wood wastes and heat-pressing the obtained powder. This material is expected to show biodegradability for the crushed concrete waste is bonded by wood. Its bending strength is much higher than that of general concrete. Wood can be replaced with various plants and vegetables. This technology even enables us to produce a construction material from sand/gravel and grass.
Media release: https://www.iis.u-tokyo.ac.jp/en/news/3241/
Construction Links Network: https://constructionlinks.ca/news/wood-you-like-to-recycle-concrete/
EurekAlert: https://eurekalert.org/pub_releases/2020-02/iois-yl022020.php
Complete Recycling of Concrete Waste
To realize the complete recycling of waste concrete, we are developing a new recycling
technique that produces zero by-products and does not require new materials to recycle
concrete waste.
Development of Plastic–Concrete Composite
We developed a novel construction material by crushing concrete and plastic wastes
and heat-pressing the resulting powder. During mechanical recycling, it is difficult to
separate plastics owing to the assortment of plastics in the waste. With our technique,
separation is unnecessary if a certain amount of thermoplastics is present.
The water absorption of the material can be nearly zero by optimizing the mix proportion
of concrete and plastic; the resultant material is potentially more durable compared to
conventional plastics. The long-term durability of the composite is currently under evaluation.
Related paper: Experimental Investigation on Bending Strength of Compacted Plastic-Concrete
Concrete Inspection Causing Extremely Minor Damage
Concrete inspection generally requires core samples with a diameter of 10 cm,
and this can cause damage to the associated concrete structures and reinforcing
bars. Various semi-destructive tests and non-destructive tests have been
proposed. However, the former induces concrete damage ranging in the size
of a few centimeters and the latter has low accuracy. We are therefore developing
novel methods for evaluating the mechanical and durability properties of concrete
by drilling holes that have a diameter smaller than 1 mm.
SCMT5.pdf (3.9MB)
Evaluation of Air and Water Permeation in Concrete
Concrete structures become deteriorated owing to the penetration of air, water, and ions.
We are therefore developing methods for evaluating such permeation behaviors based on
the pore structure of concrete by conducting analysis through mercury intrusion porosimetry.
The obtained results can be incorporated in design codes for concrete structures.
Related paper (How to calculate air transport in concrete)
Related paper (Relationship between concrete pore size and mass transport)
Related paper (How to estimate water permeation into concrete using W/B and curing condition)
Understanding of Deterioration Mechanisms of Concrete Structures
We are trying to understand the deterioration mechanisms of concrete structures due to
freezing and thawing, chloride attack, etc. Model channels in the nano/microscale are utilized
to observe the deterioration process in concrete.
Related paper#1 (Freezing and thawing simulation using micro channels)
Related paper#2 (Chloride ion monitoring in nano channels using MQAE)
Observation and Analysis of Concrete using Special Devices
To understand and evaluate concrete properties, we used various special devices, such as
Focused Ion beam-Scanning Electron Microscopy (FIB-SEM) to observe the three-dimensional
pore structure of concrete; Scanning Probe Microscopy (SPM) to measure microscopic surface
property; and Magnetic Resonance Imaging (MRI) to observe water permeation into concrete
in a non-destructive way.
Related paper (Scanning probe microscopy on cement paste)
Related paper (3D pore network in concrete observed with FIB-SEM)
Related paper (Observation of water permeation in concrete using MRI)
Deformation Mechanism of Concrete
Hardened cement paste is generally very brittle. However, we observed that it shows large
deformation without macroscopic damage under confining pressure, and we are trying to
understand this mechanism. We are working on this topic with the cooperation of geoscience
laboratories.
Related paper#1: Deformation Mechanism of Hardened Cement Paste and Effect of Water
High-speed Impact Test
Accidents caused by explosions and terrorism may lead to high-speed impacts
on concrete. Although macroscopic fracture mechanisms such as crack propagation
have been studied, the microscopic effect of impact on the cement paste matrix
is not well known. Our primary objective is to employ a gas gun for conducting
high-speed impacts on concrete and thereby analyze the impact points for studying
the changes in the cement paste matrix. We are currently collaborating with
an impact engineering laboratory for the same.
Related paper #1: Microscopic Change in Hardened Cement Paste Due to High-Speed Impact
Water Evaporation Reduction Mechanism by Curing Agents
Curing agents are employed for retaining moisture in concrete, but moisture
retention can vary according to prevalent conditions. Since the evaporation
reduction mechanism of curing agents is not well known, we are studying
it for effective usage. We are currently collaborating with several organic chemistry
laboratories for the same.