Abstract
Due to their porous nature, lightweight aggregates have been shown to exhibit thermal properties that are advantageous when used in building materials such as lightweight concrete, grout, mortar, and concrete masonry units. Limited data exist on the thermal properties of materials that incorporate lightweight aggregate where the pore system has not been altered, and very few studies have been performed to quantify the building energy performance of structures constructed using lightweight building materials in commonly utilized structural and building envelope components. In this study, several lightweight concrete and masonry building materials were tested to determine the thermal properties of the bulk materials, providing more accurate inputs to building energy simulation than have previously been used. These properties were used in EnergyPlus building energy simulation models for several types of commercial structures for which materials containing lightweight aggregates are an alternative commonly considered for economic and aesthetic reasons. In a simple model, use of sand lightweight concrete resulted in prediction of 15–17% heating energy savings and 10% cooling energy savings, while use of all lightweight concrete resulted in prediction of approximately 35–40% heating energy savings and 30% cooling energy savings. In more complex EnergyPlus reference models, results indicated superior thermal performance of lightweight aggregate building materials in 48 of 50 building energy simulations. Predicted energy savings for the five models ranged from 0.2% to 6.4%.
Highlights
Thermal properties obtained for the normalweight concrete (NWC), sand lightweight concrete (SLC), and all lightweight concrete (ALC) concrete mixtures were used in an EnergyPlus building energy simulation model to analyze the heating and cooling energy requirements of a simple structure subjected to temperatures typical of summer and winter days in selected locations
Laboratory testing of concrete, grout, and masonry concrete masonry units (CMUs) building components provided thermal property test results that are material specific and could be used in a number of applications for design and analysis of structures to assist with weighing of alternatives for building materials and quantification of benefits over the life cycle
Of significance in this study, heat capacity and thermal conductivity tests were performed on bulk specimens, without crushing the concrete and compromising air void structure of lightweight fine and coarse aggregate
Summary
Manufactured lightweight aggregates are a building product produced by heating certain shales, clays, slates, fly ashes, or blast-furnace slags in a high-energy pyroprocessing facility [1]. Several publications provide suggested ranges of values for thermal properties of lightweight concrete and masonry materials. Laboratory, Golden, CO, USA), with input material properties measured using a new test method that preserves the void space within the building materials containing the lightweight aggregates, which provides a more accurate indication of the potential energy saving resulting from the use of lightweight concrete, grout, and masonry units in typical building construction. One study showed that lightweight aggregate concrete can reduce heat losses due to thermal bridging effects, when compared to normalweight concrete [21], in this study thermal properties were determined using a surface measurement probe rather than measurement of bulk samples, and only one type of residential building (single-story apartment model) was included in this study. Control models using lightweight concrete masonry exhibited energy efficiency greater than that of normalweight masonry materials, in warmer climates [25]
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