Developing climate-responsive passive strategies for residential envelopes in the warm humid climate of South India

PurposeEnergy codes for residential buildings in India prescribe design guidelines for each climate zone. However, these guidelines are broad and similar for different cities under the same zone overlooking climatic variations due to altitude, location and other geographical factors.Design/methodology/approachTo develop strategies addressing the city-specific requirements, a stepwise simulation approach was used. Integrated Environmental Solutions–Virtual Environment (IES-VE) was used to create a prototype of a singly detached residence. The applicability of strategies is studied during the day and night times. Optimum orientation, the thickness of insulation, Window–Wall Ratio, the impact of cross-ventilation and shading depth are determined for two cities – Tiruchirappalli and Coimbatore under the warm-humid climate zone of India.FindingsResults indicate that optimum insulation thickness and WWR vary between both cities during daytime and night time. In Tiruchirappalli, roof and wall insulation using polyurethane board (100 mm) and foam concrete (25 mm) offers a maximum reduction of 2.2°C indoors. Foam concrete (25 mm) insulation for roof and expanded polystyrene (25 mm) for walls reduce a maximum of 2.6°C during daytime in Coimbatore. Further, night ventilation with 20% WWR allows an average decrease of 0.5–0.6°C in triply exposed spaces facing the South. The use of a 2'0" depth shading device shows a maximum reduction of 0.1–0.3°C.Originality/valueThe contribution of this work lies in developing city-specific inputs presenting the advantage of easy replicability for other cities in the Indian context.

Water Sensitivity of Hemp-Foam Concrete

The necessity to build energy-efficient and low environmental impact buildings favors the development of biobased light-weight materials as hemp-foam concretes. In this context, experimental protocols were developed to study the effects of hemp shiv and the production methods on the water sensitivity of bio-based foamed concrete (BBFC). Foam concrete incorporates several materials and compounds: cement, protein-based foaming agent, ground granulated blast–furnace slag, metakaolin as a binder, and hemp shiv as bio-based aggregates. The study investigated first the effect of the incorporation of hemp shiv (from 0 to 15 vol%) and then the elaboration method, comparing direct method versus preformed method on the resulting physical properties, the isotherms sorption-desorption and the capillary water absorption of hemp-foam concretes. We observe an increasing porosity of the concrete with hemp shives content. Additionally, hemp shives increase the adsorption and the capillary absorption of water. Moreover, the preformed method produces concretes more sensitive to water than the direct methods since it increases its porosities.

KINETICS OF RHEOLOGICAL CHARACTERISTICS OF FOAM CONCRETE MIXTURE

The results of experimental studies are presented, the purpose of which was to study the influence of variable formulation and technological factors on the rheological characteristics of the foam concrete mixture, in particular, the structural strength. This is preceded by an analysis of the process of structure formation of cellular concrete. As a result, it is shown that the properties of cellular concrete are determined by the nature of the distribution of the solid component. The structure of the solid phase is formed at the earliest stages of the formation of cellular products and depends on the rheological characteristics of the mortar and cellular mixture. In the technology of cellular concrete, it is important to synchronize the processes of pore formation and the growth of plastic (structural) strength, which is also associated with a change in the rheological properties of the mixture. Using the methods of mathematical statistics, the influence of the content of the filler in the mixture with cement, the content of the complex additive, and the effect of mechanical chemical activation on the kinetics of the plastic strength of the foam concrete mixture were studied. The kinetic dependences of the plastic strength of the foam concrete mixture in the range of 6 ... 24 hours from the moment of manufacture have been constructed. Each of the 15 curves is maximized by a 3rd-degree polynomial. Based on the obtained dependences, they are differentiated between the first and second derivatives. As a result, the equations of the speed and intensity (acceleration) of the plastic strength of the foam concrete mixture were obtained. According to the results of the previous experiment, carried out according to a three-factor plan, a 4-factor plan was synthesized, in which the aging period of the foam concrete mixture was taken as the fourth factor. The calculated theoretical values of the characteristics of the structural strength of the foam concrete mixture were entered into the matrix. As a result, mathematical models of plastic strength, speed, and intensity of plastic strength of the foam concrete mixture were calculated and the influence of variable factors studied on the isosurfaces of these properties was visualized. The analysis of these dependencies made it possible to determine the characteristic recipe and technological conditions for obtaining a foam concrete mixture with the required values of plastic strength.

Rheological characteristics of the binder for foam concrete with a complex of mineral modifiers

The paper considers the effect of mineral additives on the rheological characteristics of a binder for foam concrete. The compositions in the study were divided into two groups: based on nanostructured binder (NB) and based on cement. For the compositions of the first group portland cement is proposed as a modifying additive,for the compositions of the second group NB and anhydrite were used as modifying additives. It has been shown that the introduction of cement into NB increases the viscosity due to an increase in the concentration of large-sized particles, while the combined use of nanostructured binder and anhydrite as modifiers of the cement system helps to reduce the viscosity of the cement mortar and increase its mobility, which reduces the amount of mixing water. From a technological point of view, this will make it possible to obtain materials with a rational pore structure by optimizing porosity processes.

Research of the mineral additives influence on aggregative stability of foam concrete mixture

An effective method for increasing the aggregate stability of non-autoclave heat-insulating foam concrete is proposed. This material is prepared using a two-stage technology on a turbulent-type installation. An increase in the stability of the foam in the mortar mixture by 9.5-23% has been established. An increase in the viscosity of the foam concrete mixture by 13.5% was revealed. Wollastonite and diopside are actively involved in the formation of a stable structure of foam concrete and are structurally modifying centers. The introduction of mineral additives contributes to the formation of a homogeneous stable structure of non-autoclave foam concrete. Thus, an increase in the stability of the cellular system in the technology of non-autoclave cement-ash foam concrete is possible due to the control of the processes of structure formation when using dispersed mineral additives of wollastonite and diopside. Due to the structural-modifying effect of additives as crystallization centers for neoplasms, a more complete hydration of the cement and a strong contact of the additives with the cement stone should be ensured