Researchs

 

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.

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(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.

プレスリリースを行いました(「廃棄食材から完全植物性の新素材開発に成功~」) Press Release

(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.

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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

 

Paper #1: Improving the properties of botanical concrete based on waste concrete, wood, and kraft lignin powder

 

 

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. 

 

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Related paper: Recycling of Hardened Cementitious Material by Pressure and Control of Volumetric Change 

  

 

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.

 

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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.

 

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pdf SCMT5.pdf (3.9MB)

Related paper #1: Study on the correlation between the compressive strength of hardened cement paste and the physical properties of drilling powder

Related paper #2: Fundamental Study on the Correlation between Scaling Resistance and Pore Structure Evaluated using Drilling Powder

Related paper #3: Minimal Drilling Technique to Measure Chloride Penetration Depth and Carbonation Depth in Concrete

 

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.

 

 water_e.jpg

 

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.

 

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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.

 

FIBSEM_SPM_e.jpg

 

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.

 

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Related paper#1: Deformation Mechanism of Hardened Cement Paste and Effect of Water

Related paper#2: Mechanical Behavior of Cement Paste and Alterations of Hydrates under High-Pressure Triaxial Testing

Related paper#3: Deformation mechanism of hardened cement paste under high stress and application of flow law

 

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.

 

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Related paper #1: Microscopic Change in Hardened Cement Paste Due to High-Speed Impact

Related paper #2:  Moisture dependency of variation of pore structure and property of cementitious materials 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.

 

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Paper: Direct Causality between Film Formation and Water-Retaining Effect of Surfactant-Based Film-Forming Curing Compound for Concrete

 

 

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2024.03.28 Thursday