Wood Waste Condition of Hong Kong

In the introduction session, he introduces the wood waste condition of Hong Kong. inert waste non-inert waste and valuable materials. Then he moved towards traditional waste treatment methods and their negative impacts. landfill disposal of wood waste(North America, Hong Kong): negative impacts of this method of wood waste disposal are making scarce of space for landfill disposal, leachate treatment problems, GHG emission.

In this session he also included the another method called incineration method of wood waste treatment (popular in New Zealand Europe and Korea etc.): negative impacts of this method of wood waste disposal are air pollution, co2 emission, ash treatment problems etc. according to him these were the reason for his motivation towards research After stating the major limitations of conventional opc particleboards such sa Low wood cement compatibility, high carbon footprint etc. he talked about Innovative Timber Recycling into Cement-bonded.

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• Then he talked about methodology they used in their experiment
• Particleboard Production Using Green Cement and CO2 Curing and
• Mechanical Properties, Fire Resistance, and Spectroscopic/Microscopic Analyses
• In the result and discussion part speaker talked about result of the experiments and their relevancy

In this session speaker talked briefly about products such as cement, wood particles, water, and chemical additives and their characteristics . The use of concrete-contaminated timber formwork requires the least pre-treatment and minimizes the secondary pollution as the concrete attached will not impair cement hydration. In view of low thermal conductivity and beneficial sound insulation property of timber, the final products could be utilized as thermal-insulating and sound-insulating materials.

However, the soluble organic constituents of timber would retard the setting hardening processes and reduce the mechanical strength of cement-bonded particleboards. The adhesives, paints and preservatives in timber formwork would also complex with calcium and hinder the pH increase, resulting in undermined strength development via calcium silicate hydrate (C-S-H) and calcium hydroxide (CH) generation by cement hydration). Although the addition of accelerators (CaCl2, MgCl2, FeCl3, AlCl3 and Al2(SO4)3) may enhance the early strength, it results in inadequate strength of the cementitious matrix in the long, which compromises the application of cement-bonded particleboards.

In order to address the above barriers, this study evaluates and optimizes the mixture designs and process conditions for advancing the recycling of waste formwork into new marketable products for construction industry. Ordinary Portland cement (OPC) is the most common binder that upon hydration produces C-S-H gel and monosulphate, filling in pores of the matrix and binding the interfaces for mechanical strength development.

It calls for research and development of alternative cementitious binders to lower energy consumption associated with OPC production Magnesia cement (MgO) is a relatively new cementitious substitute for OPC, which is transformed from calcining magnesite (MgCO3) at a markedly lower temperature than Portland cement clinker sintering required. Besides, MgO cement demonstrates beneficial properties in utilisation, such as higher durability, lower sensitivity to impurities, stronger fire resistance, and aesthetically pleasant appearance. However, high water absorption and relatively low availability of the raw materials are the major limitations.

Now he after showing the some limitation of conventional method now he talked about the use of MgO cement as a promising alternative material for OPC and introduces various types of water repellent materials to address the problems above .

In addition, MgO cement could produce a significant proportion of brucite (Mg(OH)2) that may enable remarkable CO2 sequestration during the particleboard production process. Accelerated carbonation using compressed carbon dioxide gas. The conversion of brucite into magnesium carbonates or hydrated magnesium carbonates in a short period of CO2 curing contributes to changes in the microstructure.

During accelerated carbonation, the pore size and total volume are reduced while the density and mechanical strength are enhanced accordingly. Furthermore, in view of abundant amount of brucite available in MgO cement, the addition of incinerator sewage sludge and ground granulated blast slag may initiate pozzolanic reaction to further improve the strength and reduce water absorption.

The addition of selected food waste such as blue mussel shell containing nearly 95% CaCO3 may provide excess nucleation sites to accelerate carbonate formation and strength establishment. Hence, this study 3 further explores the viability of a simple approach to enhance mechanical properties and economic feasibility by blending the three different types of green materials as cement supplement.

From this seminar speaker summarized following points about Timber Recycling into Cement-bonded Particleboard and its benefits as follows.

• (a) determine the optimal binder formulation and process conditions to produce cement-bonded particleboard with high mechanical strength and dimensional stability
• (b) examine the properties of thermal insulation and noise reduction as a building material
• (c) compare the performance of OPC and MgO cement for recycling waste formwork
• (d) assess the potential use of CO2 curing for strength enhancement
• (e) validate cost and augment the applicability of wood waste recycling through integration of green materials into the mixture. The acceptability for reuse is justified in terms of mechanical strength, dimensional stability, thermal conductivity and sound absorption capacity.

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