Development of an unfired clay masonry system

Abstract

An unfired clay masonry system complete with renders and fixings was required for the mainstream construction of thin non-load bearing inner leaf or interior walls in domestic dwellings. A determined movement to reduce the impact the building sector has on the environment aims to incorporate natural materials such as earth, animal products and vegetable matter into the development of building products for the construction of domestic dwellings to produce sustainable modern buildings with minimal impact on the environment. An unfired clay masonry system is the most desirable system for the construction of earth walls in modern buildings. Masonry units are extruded quickly and consistently to satisfy the demands of mainstream construction. Walls are built in a manner similar to that of concrete block-work and fired-clay brickwork used in modern construction. Specifications and standards to satisfy modern building procedures and regulations can be more readily developed for the unfired clay masonry. An investigation into the industrial extrusion of clay brick units showed that the unfired clay or green brick units were of strengths comparable to low strength materials used in the construction of thin non-load bearing walls. Suitable mortars for the unfired clay brick units were developed directly from the respective brick clays. The unfired clay mortars gave strengths and bond strengths required for the construction of thin walls with the addition of sodium silicate and the use of thin mortar joints. Unfired clay blocks extruded using brick clay representative of that most commonly used for the manufacture of fired-clay brick units gave good strengths. Masonry constructed using the unfired clay blocks and the respective sodium silicate unfired clay mortar gave good mortar strengths, mortar bond strengths, compressive strengths and flexural strengths. Compressive strengths and flexural strengths of the masonry were comparable to that of industrialised low strength buildings materials such as aerated concrete block masonry suitable for the construction of thin non-load bearing walls. The unfired clay masonry with un-mortared perpendiculars were however not suitable for the construction of thin non-load bearing walls. Compressive strengths and flexural strengths of masonry constructed with a perforated unfired clay block format were substantially lower than those of masonry constructed with a solid unfired clay block format. Compressive strengths were suitable for the construction of thin non-load bearing walls but flexural strengths were not in particular the flexural strengths measured when loading perpendicular to the bed joints. Wood-fibre significantly improved the strength and toughness of the unfired clay masonry and a similar perforated wood-fibre block significantly improved the flexural strength perpendicular to the bed joints giving masonry of the desired flexural strengths. Adding wood-fibre into the extrusion process was problematic but a successful procedure was developed to incorporate the wood-fibre into the brick clay mixture prior to extrusion. Moisture significantly influenced the strength of the unfired clay masonry. At ambient conditions the strength of the unfired clay masonry is adequate but at higher moisture contents the strength decreases and exposure to water or constant exposure to very high levels of relative humidity could significantly lower the strengths of the unfired clay masonry.

Date of Award	30 Jun 2012
Original language	English
Awarding Institution	University of Bath
Supervisor	Pete Walker (Supervisor)