Dr Alalea Kia

The overarching research challenge that I address is urban flooding. The annual global cost of flooding was £60bn in 2019 and is projected to increase to £500bn by 2030, with climate change increasing the likelihood of major storm events by 59%. Permeable concrete pavements are one of the most promising flood mitigation strategies to prevent surface flooding, they rapidly drain stormwater through otherwise impermeable infrastructure. Conventional permeable pavements are, however, prone to clogging, blocking the pavement and reducing its drainage capacity. The frequent maintenance required due to clogging degrades performance and service life and is difficult to perform on active infrastructure. Most importantly, conventional permeable pavements have insufficient strength and durability, making them unsuited for heavy load bearing infrastructure use. 

I have developed a next generation clogging resistant permeable pavement alternative, with a uniform pore structure, to address urban flooding. This clogging resistant permeable pavement (CRP, also known as Kiacrete) has improved strength and higher permeability than conventional systems of equal porosity, yet does not clog despite extensive exposure to stormwater sediments. 

My research spans across a number of fundamental research challenges including structural, material, thermal and hydrological. I combine state-of-the-art experiments and multi-scale multi-physics numerical modelling with large-scale field testing to deliver a built environment resilient to future climate uncertainties and urbanisation.

Permeable concrete (also known as pervious concrete) is used to reduce local flooding in urban areas and is an important Sustainable Drainage System (SuDS). However, permeable concrete exhibits reduction in permeability due to clogging by particulates, which severely limits its service life. My research in this field started by reviewing the clogging mechanism and current mitigating strategies in order to inform the future research needs [Kia et al., 2017].

I then developed new methods to study clogging and define the clogging potential for conventional permeable concrete pavements. The tests involved applying flowing water containing sand and/or clay in cycles, and measuring the change in permeability. Substantial permeability reductions were observed in all samples, particularly when exposed to sand and clay simultaneously.

In addition, I have characterised, for the first time, clogging potential in three different ways to enable service-life predictions based on measuring the initial permeability decay, half-life cycle and number of cycles to full clogging [Kia et al., 2018].

In my group, we are currently studying this clogging and its effect on the pore characteristics using laboratory testing, image analysis, numerical modelling and large-scale field testing.

I have developed a next generation clogging resistant permeable pavement alternative, with a uniform pore structure of low tortuosity, to address urban flooding and the challenges associated with conventional permeable pavements. This clogging resistant permeable pavement (CRP, also known as Kiacrete) has improved strength (twice as strong, >50 MPa) and higher permeability (ten times more) than conventional systems of equal porosity, yet does not clog despite extensive exposure to stormwater sediments [Kia et al., 2019]. CRP also is highly resistant to degradation caused by freeze-thaw compared to conventional permeable concrete, reducing maintenance requirements and improving service-life [Kia et al., 2022]. 

Furthermore, I have developed a patented interlocking tile (Figure below) delivery system (PCT/GB2019/053217), to deploy cast in-situ CRP at commercial scale, addressing the challenges of applying this technology outside of the laboratory.

CRP Interlocking tile delivery system.

In addition, I have developed a new design methodology for CRP that takes into account both structural and hydrological considerations. I then applied this to 12 case studies which compare CRP with conventional permeable pavements [Kia et al., 2021b]. 

In my group, we are currently studying the material, structural, durability, thermal and hydrological performance of CRP using novel experimental and field test setups, along with multi-scale multi-physics numerical modelling.

CRP was deployed at Imperial College’s White City Campus (Figures below) in August 2020 and long-term monitoring is currently underway. This trial site enabled testing of the newly developed delivery method whilst providing a real world test site for CRP.

Our work has substantial economic, environmental and societal benefits, particularly to the construction and transportation sectors, and is supported by local government, transport infrastructure operators, product manufacturers, engineering consultancies and contractors. We will be delivering CRP at a number of different field sites in due course to monitor its performance when it is exposed to real-world conditions.

Large-scale delivery of CRP at Imperial College's White City Campus

CRP is exposed to extreme weather

New materials technologies need to be tested outside of the laboratory and exposed to real-world conditions. We undertake long-term performance monitoring of concrete infrastructure using state-of-the-art test rigs, sensor networks and drones. The collected data is then analysed using image analysis and computational methods to determine long-term behaviour.

For example, the long-term permeability and durability performance of CRP has been monitored since August 2020, using our developed novel permeability test rigs and drones, respectively (Figures below).

Long-term permeability measurements of the CRP trial site using a novel test rig

Long-term durability measurements of the CRP trial site using a drone

Green infrastructure offers significant benefits to the urban environment through improved stormwater management and a reduced urban heat island effect, however current technologies have practical limitations. In our group, we investigate and quantify the interactions between plants and the built environment using laboratory testing, computational methods and statistical procedures.