Research into Unfired Clay Soil Materials

The cost and environmental benefits of the utilisation of soil in infrastructure development far outweighs those of hauled stone or concrete. Soils have relatively low load bearing capacities and often require stabilisation.

For use in buildings higher strength thresholds necessitate intensive firing of clay soils into bricks. This is expensive and environmentally undesirable. Avoiding firing requires use of materials such as lime and/or Portland cement (PC), whose manufacture depletes global energy resources and exacerbates atmospheric pollution. 

The situation is exacerbated in low or middle-income countries (LMICs), where affordability is a major obstacle, as many do not manufacture Portland cement locally. 

By combining environmental as well as cost considerations, researchers at AMTeC have made significant impact by aiming to address the realisation of the UN Sustainable Development Goals (SDGs) by way of sustainable unfired clay material systems. 

The aim is to utilise marginal, waste and by-product materials from nature, industry or from agricultural activities. In this endeavour, some formulations have been very successful as to obviate the need to use Portland cement at all. 

Novel cement

In one such case, we have developed a novel cement that utilises ground slag, a by-product from the manufacture of steel. This novel eco-cement was trialled in the soil stabilisation for the A420 Tingewick Bypass in Buckinghamshire. This was very successful, and besides high strength, the cement was able to suppress sulphate-induced swelling that has traditionally challenged civil engineers and has caused major road failures worldwide, including on the M40. The M40 failed within 2 year of initial construction because of this problem. 

The team’s publications on swelling of sulphate-bearing soils became very popular and have many citations. Other roads in UK, including the A130 near London, adopted the lime-slag technology.

Pioneering materials

From the pioneering work on lime-slag formulations, other industrial waste materials were trialled with great success. In another successful novel cement, utilisation wastepaper sludge ash was so successful because of combining two waste streams in a synergistic manner. This warranted consideration of a patent, and the technology is encapsulated in a USW-Registered Patent No. PCT/GB2002/000708. 

The reputation from the performance on strength and volume stability of slag-based novel cements was phenomenal and did not escape notice in UK Industry. 


Prof John Kinuthia was a national awardee of the prestigious Royal Society Brian Mercer Award for Innovation on unfired scaly systems. This was a national award, and it boosted research in team’s morale to greater heights. 

The proceeds from the RS award transformed testing of souls at AMTeC, from use of analogue proving rings and dial gauges to load transducers and Linear Variable Displacement Transformers (LVDTs) for swelling measurements. 

Support and recognition continued to increase via additional UK and Welsh Government funding (from Royal Academy of Engineering (RAE), Collaborative Industrial Programme (CIRP), Knowledge Exploitation Funding (KEF), Academia for Business (A4B), Knowledge Education Economy Skills Scholarships (KESS) and ScoRE CYMRU), all for the development of eco-(unfired) materials.

From this robust background, recognition was meteoric and culminated with that by the UN UNESCO Committee. UNESCO provided global recognition, by supporting scoping of eco-materials in Africa, with case studies in Kenya and Cameroon. In Cameroon for example, the UNESCO-funded research work enabled policy changes on the use of unfired bricks. 

International impact

Researchers at AMTeC assisted in the development of Cameroonian standards on bricks (MIPROSPECS) by working with a local materials promotion authority - Mission de Promotion des Materiaux Locaux (MIPROMALO). 

A pilot project to inform the standards comprised of a housing estate for the Baka forest tribe (sometimes referred to as Pygmies) at Bertou, Cameroon. The tribe faces challenges of deforestation where forests have traditionally provided shelter. 

In Kenya, impact is ongoing, where AMTeC staff are involved in a project dealing with interlocking bricks, thus not requiring jointing mortar and hence making immense savings. 

A PhD researcher has completed a PhD on this in Kenya in 2019 and in Zambia, impact involved curriculum development and during tenure as extremal examiner/advisor during 2010-12. 

In Rwanda, AMTeC is currently informing ongoing work on low-cost housing by multi-national NGOs - MASS Group, Greenpact Africa and Earth Enable.

The holistic impact from this work reported here has led to invitations in panels and grant evaluations activities at the global level.

Ongoing activities include: 

  • Four years of service as Academic Reading Member in the Chevening and Commonwealth Scholarships
  • Three-year participation in British Council Newton Funding evaluations
  • Three years with The National Centre of Science and Technology Evaluation (NCSTE), Government of the Republic of Kazakhstan
  • Three years with the Cyprus Research Promotion Foundation (RPF)
  • Two years with the charity group - Cara Syria Programme
  • One off engagements with Ministry of Business, Innovation & Employment (MBIE), Government of New Zealand; The Research Council, Sultanate of Oman; The Research Council of Norway; and research councils for the governments, South Africa, Slovakia and with the Volkswagen Foundation (VolkswagenStiftung) of Germany among others.


Professor John Kinuthia

Professor John Kinuthia, Engineering Research