VegeBlocks are composed entirely of recycled aggregates and used vegetable oil, and are manufactured in a similar way to conventional concrete blocks, except that they are cured at higher temperatures for longer periods. They are suitable for use as non-load bearing blocks.
TRL (what used to be the UK's Transport Research Laboratory) and Qatar's Ministry of Municipalities & Environment (MME) have developed the block to help increase sustainability in construction.
The launch of VegeBlock, also described as ‘Smart Block’, represents the latest stage in a programme of collaborative work between MME and TRL to improve the sustainability and adoption of green construction. Previous projects have focused on the use of locally available recycled and secondary aggregates in place of imported primary aggregate.
The project was funded by the Qatar National Research Fund (QNRF) at the Qatar Foundation, National Priorities Research Programme (NPRP 6-1472-2-600). At a launch event, attendees were briefed on how VegeBlock has been developed from small scale samples produced in laboratories to full-size building blocks using materials and techniques specifically suited to Qatari conditions and the Gulf region. The properties of VegeBlock were described, including the announced plans to take their production forward to full scale and the release of a Best Practice Guide for its reproduction.
By using recycled materials and avoiding the use of cement, the cost of production and the carbon footprint of VegeBlock are significantly lower than that of conventional concrete blocks being used today, say the developers.
The aim of the project was focused on the development of innovative precast blocks for the construction industry without the use of cement or primary aggregates.
The project enabled the VegeBlock concept to be adapted to the specific conditions and materials available in Qatar - particularly to maximize the use of recycled and waste materials. The initiative falls in line with the Qatar National Vision 2030 objective of balancing economic development with the protection of the environment.
VegeBlock is produced from excavation waste material (limestone) and used vegetable oil. The components are mixed and compacted in a mould and cured in an oven at 170°C for up to two days. The heat treatment results in oxidation and polymerisation of the oil to act as a binder for the aggregate resulting in cured blocks with adequate strength and durability for use as construction blocks. The blocks have strength and durability properties similar to non-load bearing concrete blocks (M4 and M6 in the Qatar Construction Specifications QCS 2014) but do not require the use of cement, water or imported aggregates.
Laboratory testing programmes were carried out to optimize the process and determine which materials to take forward for the full-size production of VegeBlock. The optimisation process included different types of recycled aggregates and oils, oil content, compaction level, temperature and duration of curing. The laboratory trials demonstrated the diversity of using various types of waste material, including unwashed sand, Incinerated Bottom Ash (IBA) and excavation waste (limestone). Various types of used vegetable oils were also used including, palm oil, soybean oil and canola oil. For each combination of aggregate and vegetable oil, the optimum oil content was established and the optimum compaction level, curing temperature and curing duration determined. Optimised mixtures were developed to produced VegeBlocks meeting and complying with Qatar Construction Specification (QCS 2014) requirements for compressive strength and water absorption for non-load bearing concrete blocks. Durability tests indicated that VegeBlock was resistant to damage from water, salts and fuel.
Full scale production trials were then carried out at the Khalid Cement Industries factory in the Industrial Area in Doha. The aggregate used was limestone derived from excavation waste, screened to be finer than 8mm. Used vegetable oil was selected as the binder, thus using only recycled materials as well as avoiding the use of cement and imported aggregate. The production was carried out using the same facilities available for producing conventional concrete blocks in Doha. The process resulted in the production of large sized blocks (400mm by 200mm by 200mm).
A trial wall of full size VegeBlocks was constructed outdoors at the Qatar Standards offices in April 2016 with a wall of conventional concrete blocks for comparison. The condition of the wall has been monitored through the heat of summer and heavy rains in winter. To date, it is still intact after 10 months in service. Monitoring and testing of the trial wall will continue.
A preliminary economic analysis indicated that the production could be significantly lower than concrete blocks. The material and operational cost for manufacturing is estimated to be two thirds the cost of conventional concrete blocks. However, there is a need to develop a bespoke system for full-scale production of VegeBlock, which may impact on the capital cost. A more detailed economic analysis should be carried out when a specific plant is under consideration.
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