Effect of cement and geopolymer stabilization on the thermal comfort: case study of an earthen building in Burkina Faso

Abstract

PurposeThe stabilization of earthen blocks improves their mechanical strength and avoids adobe construction erosion due to rainwater. However, the stabilization affects the thermal properties of the earthen blocks, and thus their capacity to provide adequate thermal comfort to occupants. This article examines the influence of cement and geopolymer binders on thermal comfort in compressed earthen buildings in hot and arid climates.Design/methodology/approachThe test cell is on the building platform in Burkina Faso. The building is made of compressed earth blocks (CEB) consisting of laterite, water and binder. The thermal models of the building were implemented in EnergyPlus v9.0.1 software. Empirical validation is used to check whether the model used for the thermal dynamic simulation can reproduce with accuracy the thermal behavior in a real situation. The adaptive thermal comfort model of ASHRAE 55–2010 was used to assess thermal comfort in long-term hot and dry tropical conditions.FindingsThe results show that the CEB buildings remain hot despite the use of cement or geopolymer binder. Indeed, with both cement and geopolymer binders, on a daily basis, 19 h and 15 h are uncomfortable during, respectively, the hot and cold seasons. An increase of 1% in cement content raises the comfort hours by 9.2 h during the hot season and 11.7 h during the cold season. Hence, the comfort time varies linearly with the cement content in the building material. Moreover, there is no linear relationship between comfort time and geopolymer rate.Research limitations/implicationsComplementary work should also assess the influence of stabilization on building humidity levels. In fact, earthen materials are very sensitive to outdoor humidity and indoor humidity affects thermal comfort even if it is not taken into account in the ASHRAE adaptive thermal comfort model.Practical implicationsThe present study will certainly contribute to a better valorization of clay potential in countries with similar climatic conditions.Social implicationsThe use of geopolymer binder is a suitable ecological option to replace the cement binder. It is important to mention that nighttime comfort can be increased through passive strategies such as natural ventilation.Originality/valueMost CEB material stabilization analyses including cement and geopolymer ones were mostly investigated at the laboratory scale and less at the building scale. Also, the influence of the binder rate on the thermal performance of buildings made of cement and geopolymer has not yet been assessed. This paper fills this gap of knowledge by assessing the impact of cement and geopolymer binder rates on the thermal comfort of CEB dwellings.

Optimisation of Thermal Comfort of Building in a Hot and Dry Tropical Climate: A Comparative Approach between Compressed Earth/Concrete Block Envelopes

“…However, the country faces a hot and dry climate with maximum temperatures of nearly 40˚C in 2015 [2] and remains constantly growing [3]. It then becomes essential to be able to offer local residents affordable, healthy and thermally comfortable housing, and adapted to increasingly severe climatic conditions [4] [5].…”

“…However, the energy and ecological issues linked to this material are pushing the search for new alternatives. In fact, 4 billion tons of cement are produced worldwide with an annual growth of 4% [4]. This intensive production would be responsible for emissions of 45.45 billion tons of CO 2 globally in scenario 3 of shared socio-economic pathways [6].…”

“…Earthen materials such as compressed earth blocks (CEB) have been the subject of many studies in recent decades as a suitable alternative to cementitious materials. These studies focused on the social perception of these materials [7], their potential to meet construction standards [8], their thermo-physical properties [9] and their durability [4] [10]. Despite the various advantages of the CEB compared to cementitious materials and the current improvement in the manufacturing, the conditions for improving the thermal comfort of CEB housing, based on the architectural effects of buildings and natural ventilation systems, are still to be assessed.…”

“…In addition, Burkina Faso has abundant resources of laterite [4] which can be used for the production of CEB. Therefore, this would contribute not only to making the economy prosper through job creation; but also, to mitigating the climate variability.…”

Comparative Assessment of The Thermal Comfort in Naturally Evolving Buildings in Hot and Dry Sahelian Climate: Case of The City of Ouagadougou in Burkina Faso

“…Modern construction uses materials such as cement and steel which are not always adapted to the hot and dry climatic conditions of many regions such as Burkina Faso. This increases the thermal discomfort of non-air-conditioned buildings and the electricity consumption due to the use of mechanical air conditioning systems for thermal comfort [2,[8][9][10]. Studies have shown that the analytical model for calculating the PMV index predicts a good thermal sensation in mechanically conditioned buildings; but it unfortunately predicts a warmer thermal sensation than that of felt by the occupants in buildings with natural ventilation [11].…”