Compressed earth blocks, their thermal delay and environmental impact

Proceedings of the II International and IV National Congress on Sustainable Construction and Eco- Efficient Solutions 871 COMPRESSED EARTH BLOCKS, THEIR THERMAL DELAY AND ENVIRONMENTAL IMPACT 1 Roux Gutiérrez Rubén Salvador; 1 Velazquez Lozano Jesús, 1 Rodríguez Deytz Homero 1 Facultad de Arquitectura Unidad Saltillo, Universidad Autónoma de Coahuila Blvd. Fundadores Km 13, Ciudad Universitaria UAdeC, Arteaga, Coahuila México. CP 25354 e-mail: rubenrouxgutie[email protected].mx, rroux3[email protected]; jv[email protected], [email protected]; homero[email protected]m ABSTRACT This communication is the result of research that addresses the issue of blocks of compressed earth (CEB – Compressed Earth Blocks) thermal properties, to corroborate the advantages of this alternative construction material, conventional materials, to check that these materials can meet the needs of the population in their decent housing construction, improving the quality of life of the user and producing less environmental impact. Thermal tests were simulating the effect of the Sun on a wall, registering the temperature during the tests determining the thermal delay on the walls depending on the material. It is as well as with the results of the tests determined which the optimal material for use as housing enclosure is. On the other hand is the study of the CEB, stabilized with hydroxide of lime and cement, seeking to comply with the Mexican standards, in the section relating to materials for use in masonry buildings and thus verify that these materials comply with quality requirements, as well as conventional materials, coupled with the analysis of the life cycle (LCA) in two populations of BCE's stabilized with cementations seeking to determine their environmental impact and finally to be able to compare them with existing databases of conventional materials. Keywords: CEB, Thermal delay, construction with land, stabilization, environmental impact Chapter III – Energy Efficiency 872 1.- Introduction The commentary on how much the use of alternate and regional materials in construction is practicable, however, when a reference is made to some of these, they are associated with materials used in a satisfactory manner by some civilizations for the edification of their habitat, nevertheless, nowadays, commentary on these traditional materials exists, where they are considered “low quality” or are just reviled regarding their quality as they are used by people with scarce resources for the self-edification of their housing. Building with earth is a millenary technique in mankind’s history, where man employed it to protect himself from the outdoors. According to Neves (2007) passing the construction with earth by the proper technical and cultural adaptations of each region. Past ages inhabitants knew how to explore the good properties of the earth and use it in beautiful constructions. (Neves, 2007). However according to McHenry (2004) radical changes produced by the Industrial Revolution, low cost energy, a fast expansion of transport systems, distribution and preference for more “modern” materials such as Portland cement which had an important paper on World War II for the reconstruction of European cities, virtually ended the use of earth as construction material. (McHenry, 2004). Currently in Mexico, construction with earth is a technique practiced in a handcrafted manner, without official norms to regulate its use, which is why its diffusion on the construction market is minimal. Neither do studies about the material’s physical aspects exist as is the case of the material’s thermal capacity particularly of the Compressed Earth Blocks (CEB) technique, which allows to make a comparison about conventional materials and to corroborate their energy efficiency and the grade of their sustainability. The CEB is a construction material manufactured with a mixture of raw earth and a stabilizer, like lime, cement, asphalt or gypsum, which is molded and compressed using a mechanical or manual press. It’s been used as a substitute for the fired clay brick in construction activities; using it in the construction of walls manually piling it on and using a mixture of the same materials as a base mortar. The manual press of Colombian patent “Cinva–Ram” has been used in its manufactory in the present study, looking to homogenize them and achieve a quality in accordance with the Mexican Norms (NMX-C-404-ONNCCE-2005; NMX-C-036- ONNCCE-2004; NMX-C-037-ONNCCE-2005) described by the Construction Industry, as well as determine and stabilize those CEB’s with CPO-20 cement and for the case of the use of Calcium Hydroxide. Two objectives are stablished for the present research under these premises: 2.- Objectives - The analysis of the thermal properties in the compressed earth blocks, to determine the thermal delay they present upon applying a heat source in a controlled environment, in this case the laboratory. This way the thermal transmission through self-elaborated walls with compressed earth blocks (CEB), conventional concrete blocks and fired clay brick is compared. - Develop, identify and evaluate the environmental impacts and saturated energy associated with the production, management, implementation, use and disposal of CEB, with the purpose of comparing the results obtained of the populations of CEB stabilized with calcium hydroxide. The tests of thermal conductivity will be limited to applying a constant heat source, to take measurements of the temperature presented by the tested walls, and thus compare their behavior. Proceedings of the II International and IV National Congress on Sustainable Construction and Eco- Efficient Solutions 873 In the earth materials’ case it’s very important since it can be achieved to have a house inside its thermal comfort area, unlike the conventional construction materials, making the use of mechanical air conditioning equipment unnecessary, to achieve this comfort, mostly in zones with rainy tropical climates. The thermal delay tests will allow to determine the time it takes for the wall’s outer side’s temperature to pass into the wall’s inner side, the thermal inertia or the ability to store a material’s heat depends on the specific mass, density and heat, this characteristic is what determines the use of mechanical air conditioning in a building in a major or minor degree. With that carried away and obtaining the results, a Life Cycle Analysis (LCA) will be realized, in agreement with the norm: NMX-SSA-14040-IMNC-2008, which indicates the particularities about the life cycle analysis, principles and frame of reference. To realize the LCA, the SimaPro 7.3 version software was used, a program that allows to determine the materials’ impacts when carrying out the LCA from the cradle to the grave. 3. Methodology 3.1. Thermal delay Walls were produced using: concrete blocks (15x20x40cm), the fired clay brick (6x12x24cm) and the CEB (10x14x29cm). It has been built: two single CEB walls without plaster, two single CEB walls with lime plaster, a double wall with lime plaster and 4:1 sand, a wall without plaster, a fired clay brick wall and a conventional block wall; for a total of eight walls to test, with approximate measurements of 40x40 cm. The mortar used was of 1:1/2:3 cement, lime and sand. The test consisted in the analysis of the registered temperatures on both sides of the walls where thermocouples were placed, a constant heat source was created which consisted of a wooded board with 6 Osram brand lightbulbs of 150 W. The walls were placed one by one at a 34.5 cm. stablished distance from the wooden board and the temperatures on both sides of the wall were registered. For the results’ recollection the HOBO ware U-12 software was used, which was programed to take the temperature every 15 min interval for each side through eight hours, then the data was charted to appreciate the thermal delay and this way confirm or reject the hypothesis, see pictures 1 and 2. In chart 1: a synopsis of the maximum temperatures the different materials of the walls reached is shown, in addition showing the delay, that is to say, how much time went by since the moment in which the maximum temperatures on each side of the wall were registered, which is the thermal delay. Chapter III – Energy Efficiency 874 Type of wall Maximum temperature Thermal delay time Reduction Factor Side of the wall Exposed °C Rear °C Single CEB without plaster 1 57.786 33.183 1 h 1.741 Single CEB without plaster 2 54.602 32.407 1 h 1.685 CEB plaster 1 55.832 30.343 1:15 h 1.840 CEB plaster 2 55.021 30.444 1:30 h 1.807 Double CEB with plaster 55.56 25.695 4:15 h 2.162 Double CEB without plaster 60.918 26.671 4:15 h 2.28 Fired clay brick 58.776 37.645 0:30 h 1.561 Block 64.838 34.387 0:30 h 1.886 Chart 1 “Delay time and reduction factor. Source: Self-elaboration. 2014 Fig. 1 “Photograph previous to the beginning of the test”. Source: Self-elaboration. 2014 Fig. 2 “Photograph during the test”. Source: Self-elaboration. 2014 After testing the eight walls and analyzing the data, the next charts were developed with which in the thermal delay of each wall is observed graphically. To be able to calculate the thermal delay the temperatures of each of the walls were registered during eight (8) hours, taking record each 15 minutes and afterwards the wall was left to cool down through eight (8) hours, which were also registered in the charts. This way, the temperature variations and the time it takes to pass the energy from one side to the other are shown. The charts belong to the eight (8) tested walls and the eight (8) hours of cool down, two curves that represent the side exposed to the heat source are shown, which is the lightbulbs plaque and the opposite side are shown. The point where the maximum temperature is reached on each side of the wall is shown, see picture 3. Proceedings of the II International and IV National Congress on Sustainable Construction and Eco- Efficient Solutions 875 Fig. 3 “Inner and outer temperatures differences on the test walls”. Source: Selfelaboration. 2014 3.2. Environmental impact analysis The evaluation methodology stablishes the characterization factors through which the environmental impacts will be quantified. For most impacts described on Chart 3, the characterization will be carried by the TRACI 2 (Tool for the Reduction and Chapter III – Energy Efficiency 876 Assessment of Chemical and other environmental Impact) V4.00 2012 method developed by the United States’ Environmental Protection Agency. Nevertheless, there exist some impacts that the TRACI 2 method doesn’t have implemented in its system and that will also be evaluated. This is the case of the soil and the depletion of mineral resources, for which the ReCiPe Midpoint (I) V1.06 / World ReCiPe I method will be used, one of the most updated and harmonized methods to date and that has been developed by Pré Consultants. The energy resources will be evaluated with the CED (Cumulative Energy Demand V1.8) method. The selected impact categories are described on Chart 2. Impact category Description Thinning of the ozone layer The ozone layer is a filter of ultraviolet radiation towards the Earth. The chlorofluorocarbon compounds (CFCs) destroy this layer. Climate change An increase on the Earth’s temperature as a consequence of gas emission of greenhouse effect such as CO2, CH4, NOx, O3, etc. (fuel burning, industrial emissions, etc.). Photochemical oxidation (smog) It’s a photochemical oxidant that along the COV and NOx (fuel burning, industrial emissions, etc.) forms the photochemical smog. Acidification Decrease on the soil and water’s pH as a consequence of the emissions of NOx, SO2, NO2, NH3, HCl, HF, etc. Eutrophication Increase of inorganic nutrients SO-4 and NO- 3 in the water (feces, fertilizers, etc.). Carcinogenic compounds Chemical compounds that generate cancer in the human being. Non-carcinogenic pollutants Chemical compounds that generate diseases different to cancer. Respiratory effects Pollutants that cause respiratory diseases. Ecotoxicity Pollutants that cause toxicity to the ecosystems (plants and animals). Use of agricultural and urban soil. The use of the soil generates environmental impacts. Agricultural or urban area of soil used and/or occupied derivative of an industrial activity Depletion of mineral resources For example: minerals such as bauxite, limestone, iron, etc. Depletion of fossil resources For example: petroleum, natural gas, coal, etc. Saturated energy Energy required along the life cycle of a product. Includes energy of non-renewable fossil origin, nuc lear, biomass or renewable of solar origin, geothermal, wind, and water. Chart 2 “Environmental impact description”. Source: AIDICO. 2011 In relation to the Life Cycle Analysis’ results, the data about the entrances and exits of the CEB fabrication’s unitary processes were developed from the production practice realized by Dr. Roux especially on year 2011, enclosed in the region of Tamaulipas, at the northeast of the Mexican Republic. The compilation technique of this data was realized from the academic self-experience. The same can be said about the type and quantity of raw materials, just like the transport distances from its supply area. Proceedings of the II International and IV National Congress on Sustainable Construction and Eco- Efficient Solutions 877 Nevertheless, the raw materials’ supply stage qualitative data, which include the materials’ extraction and processing, like for example cement, or the kind of transport, have been taken from the US LCI database, which shows average data from the United States through a mixture of technologies. When it has not been possible to gather information, the Ecoinvent database was used. The life cycle model designed on the SimaPro software has been realized using the processes indicated on Chart 3. Process Database process Database Portland cement Portland cement, at plant/US US LCI Truck transport Transport, single unit truck, diesel powered/US Demolition machinery Loader operation, large, INW/RNA Gasoline mixer Gasoline, combusted in equipment/US Clay Clay, at mine/CH U Ecoinvent Sand Sand, at mine/CH U Hydraulic lime Lime, hydraulic, at plant/CH U Hydraulic lime packing Kraft paper, unbleached, at plant/RER U Water Tap water, at user/RER U Glue Vinyl acetate, at plant/RER U Table salt Sodium hydroxide, 50% in H2O, diaphragm cell, at plant/RER U CEB dump Disposal, limestone residue, 5% water, to inert material landfill/CH U Chart 3 “Selected processes in the model”. Source: AIDICO, 2011. The LCA results of the wall built with CEB stabilized with calcium hydroxide are shown on Chart 4 and picture 4 by Functional Unit, i.e. 1 m 2 of wall. As it can be observed, the raw materials and the manufacturing present the largest environmental impact with a value between 22% - 92% of each category’s total impact as seen in picture 4. The wall’s construction stage contributes importantly on the categories of water resources’ depletion and to a lesser degree the ones related to the thinning of the ozone layer and the mineral resources’ depletion. Chapter III – Energy Efficiency 878 Impact category MP and manufacturing Construction and maintenance End purpose TOTAL Thinning of the ozone layer (kg CFC-11 eq) 1.08E-06 1.04E-07 1.32E-08 1.20E-06 Climate change (kg CO 2 eq) 35.74 2.04 3.40 41.18 Photochemical oxidants - smog (kg O 3 eq) 6.34 0.07 1.01 7.42 Acidification (mol H+ eq) 12.24 0.18 1.86 14.28 Eutrophication (kg N eq) 1.50E-02 2.47E-04 1.97E-03 1.72E-02 Human health: carcinogens (HTU) 2.88E-07 1.41E-09 4.73E-08 3.37E-07 SH: non-carcinogens (HTU) 3.49E-06 7.37E-08 4.56E-07 4.02E-06 SH: respiratory effects (kg MP10 eq) 1.83E-02 6.62E-04 2.57E-03 2.15E-02 Ecotoxicity (ETU) 50.89 0.04 8.73 59.66 Use of agricultural and urban soil (m 2 a) 11.21 0.00 0.02 11.24 Water resources’ depletion (m 3 ) 0.41 1.43 0.00 1.84 Mineral resources’ depletion (kg Fe eq) 3.51E-02 3.07E-03 4.70E-06 3.82E-02 Fossil resources’ depletion (kg Petroleum eq) 8.85 0.23 1.14 10.22 Saturated energy (MJ) 451.14 11.85 48.11 511.10 HTU: Human Toxicity Unit (Toxicity cases/kg emission ). ETU: Ecosystems’ Toxicity Unit (PAF m 3 day /kg emitted ). PAF: Potentially Affected Fraction of species. Chart 4 “LCA global results of the CEB wall stabilized with Calcium Hydroxide”. Source: AIDICO, 2011 Proceedings of the II International and IV National Congress on Sustainable Construction and Eco- Efficient Solutions 879 Fig . 4. “ Square meter impacts of CEB manufactured walls stabiliz ed with Calcium Hydroxide”. Source : AIDICO, 2011