Estimating adaptive setpoint temperatures using weather stations

Reducing both the energy consumption and CO 2 emissions of buildings is nowadays one of the main objectives of society. The use of heating and cooling equipment is among the main causes of energy consumption. Therefore, reducing their consumption guarantees such a goal. In this context, the use of adaptive setpoint temperatures allows such energy consumption to be significantly decreased. However, having reliable data from an external temperature probe is not always possible due to various factors. This research studies the estimation of such temperatures without using external temperature probes. For this purpose, a methodology which consists of collecting data from 10 weather stations of Galicia is carried out, and prediction models (multivariable linear regression (MLR) and multilayer perceptron (MLP)) are applied based on two approaches: (1) using both the setpoint temperature and the mean daily external temperature from the previous day; and (2) using the mean daily external temperature from the previous 7 days. Both prediction models provide adequate performances for approach 1, obtaining accurate results between 1 month (MLR) and 5 months (MLP). However, for approach 2, only the MLP obtained accurate results from the 6th month. This research ensures the continuity of using adaptive setpoint temperatures even in case of possible measurement errors or failures of the external temperature probes.Spanish Ministry of Science, Innovation and Universities 00064742/ITC-20133094Spanish Ministry of Economy, Industry and Competitiveness BIA 2017-85657-

Mussel shell mortars durability: Study of aggregate replacement limit

[Abstract]: The knowledge acquired through previous experimental phases with coating mortars with mussel shell aggregates led to conclude that irregular, flaky and hydrophobic particles of the mussel shell and the organic matter content introduce entrapped air and entrained air in the mixes. This phenomenon causes different and opposite effects on the main properties of mortars, which are in some way positive and negative (for durability), consequently, their durability cannot be easily predicted. The present work pretends to analyse the results of different durability tests, such as water vapour permeability, adhesive strength, and weathering cycles to recommend the maximum percentage of mussel shell sand used in coating mortars that guarantee the required lifespan. After an in-depth literature review, it can be said that it is not easy to predict the durability of mortars using mussel shell aggregates. This question has been hardly analysed in the existing literature and the maximum substitution percentage of conventional aggregate that can be replaced is not clear. This work aims to answer this issue by analysing different properties: water vapour permeability, adhesive strength, and weathering cycles. Mussel shell content improves the water vapour permeability of both air lime and cement mortars but worsens the adhesive strength and weathering cycle behaviour. For most applications, 25 % of mussel shell aggregate can be employed, but for some applications, 50 % or even 75 % of mussel shell aggregate is feasible and will avoid the undesirable landfilling of this waste.This work has been developed within the framework of the project "Valorización de las conchas de bivalvos gallegos en el ámbito de la construcción" (Valorisation of Galician bivalve shell in the construction sector; Code 00064742/ITC-20133094), funded by CDTI (Centro para el Desarrollo Tecnológico e Industrial) under the FEDER-Innterconecta Program, and co-financed with European Union ERDF funds

Genetic programming to improvement FIB model: bond and anchorage of reinforcing steel in structural concrete

[Abstract] Starting from the FIB database, this work is aimed to analyze the current equations which predict the main datum that can be provided by bond tests: the ultimate bar stress when the failure is reached. Furthermore, Genetic Programming (GP) techniques are also applied in order to enhance the expression of the FIB, which achieves the best adjustment so far, giving rise to the new Model Code 2010. The final result shown is a highly predictive equation. The results are compared with those included in the Model Code and it is showed the influence of the main variables on the phenomenon (concrete strength, yield strength of steel, concrete cover, transverse reinforcement and diameter of the bar).Ministerio de Ciencia e Innovación; BIA2010-21551Galicia. Consellería de Economía e Industria; 10MDS014CTGalicia. Consellería de Economía e Industria; 10TMT042EGalicia. Consellería de Economía e Industria; 10TMT118004PRGalicia. Consellería de Economía e Industria; 10TMT034

Optimization of existing equations using a new genetic programming algorithm: application to the shear strength of reinforced concrete beams

[Abstract] A method based on Genetic Programming (GP) to improve previously known empirical equations is presented. From a set of experimental data, the GP may improve the adjustment of such formulas through the symbolic regression technique. Through a set of restrictions, and the indication of the terms of the expression to be improved, GP creates new individuals. The methodology allows us to study the need of including new variables in the expression. The proposed method is applied to the shear strength of concrete beams. The results show a marked improvement using this methodology in relation to the classic GP and international code procedures.Ministerio de Ciencia e Innovación; BIA2007-60197Ministerio de Ciencia e Innovación; BIA2010-21551Xunta de Galicia; 08TMT005CTXunta de Galicia; 10TMT034

Rheology, Durability, and Mechanical Performance of Sustainable Self-Compacting Concrete With Metakaolin and Limestone Filler

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] This study analyzed the performance of self-compacting concrete with a paste composition that includes limestone filler and metakaolin replacing cement to design binary (75% cement and 25% limestone filler) and ternary binders (60% cement, 25% limestone filler and 15% metakaolin). Furthermore, to analyze the effect of the solid volume fraction (volume of sand and coarse aggregate) on concrete rheology, the concretes were designed using four volumes of paste (350 l, 400 l, 450 l and 500 l). Rheological tests were performed at three resting times to measure the viscosity and yield stress over time. The results indicated that the viscosity decreased by 43.3% when the cement was replaced by limestone filler and increased by 73.1% when the cement was replaced by 15% metakaolin while maintaining the limestone filler. These values were obtained as 27.6% and 62.2%, respectively, when the yield stress was analyzed. In addition, the hardened properties (mechanical behavior and durability) were studied by measuring the strengths at 28 days, as well as the electrical resistivity and ultrasonic pulse velocity over time. In this case, at 28 days the use of binary binder reduces the strength and resistivity (about 20%) and the employment of ternary binder reduces strength (15%) while increases the resistivity up to the double (when compared to the 100 C concrete). Moreover, to measure the efficiency of the concrete, a material index was designed that considers the fresh behavior, mechanical performance, durability, cost, and environmental impact. Self-compacting concretes with ternary binders provided the highest indices. The use of alternative materials, particularly metakaolin has been proven to be a good option to enhance concrete sustainable performance.The study is part of two projects entitled: “Robust self-compacting recycled concretes: rheology in fresh state and mechanical properties (Ref: BIA2014-58063-R)” and “Sustainable High Performance Self-Compacting Concrete using low clinker cement, and integral curing and self-healing agents (HACCURACEM) (BIA2017-85657-R)” funded by MINECO. Moreover, this work was also made possible by the financial support of a pre-doctoral grant of MINECO (FPI 2015- ref BES-2015-071919) and two grants for international pre-doctoral stays: (a) FPI 2015 and (b) IACOBUS program for “Galicia–North of Portugal Euroregion

Influence of the Mixing Procedure on the Fresh State Behaviour of Recycled Mortars

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] The effect of two different mixing protocols on the fresh-state behaviour of self-compacting mortars with and without recycled sand was compared. For this purpose, the mortar mixes were designed considering three solid volume fractions, while maintaining the water to cement ratio and superplasticiser dosage constant. The results conclude that the inclusion of recycled sand harmfully affects the rheological behaviour of the mortars and this effect can be mitigated using mixing protocols with longer mixing times and delayed admixture addition times. Finally, a rheograph was developed to explain the expectable changes in a conventional mix when recycled sand is incorporated, the solid volume fraction is varied and changes are applied to the mixing procedure

Deformation recovery of reinforced concrete beams made with recycled coarse aggregates

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract:] The purpose of this research is to analyse the long-term deformations of reinforced concrete beams made of recycled coarse aggregates (RCA), using four different replacement ratios, 0%, 20%, 50% and 100%. For said purpose, three different loading stages were carried out: firstly, loading and sustained load for 1300 days, secondly, unloading and recovery where the deformations were registered over a one year period, and lastly, testing the concrete beams up to failure in order to analyse the effect of recycled aggregates on pre-cracked concrete members. The results led to the analysis of deformations under sustained load, as well as those produced after removing the load and the performance of pre-cracked members, while identifying the effect of recycled coarse aggregates on concrete performance in terms of plastic deformation, recoverability and concrete stiffness, and also on structural design.Ministerio de Industria, Economía y Competitividad; BIA2017-85657-

Estimating Adaptive Setpoint Temperatures Using Weather Stations

[Abstract] Reducing both the energy consumption and CO2 emissions of buildings is nowadays one of the main objectives of society. The use of heating and cooling equipment is among the main causes of energy consumption. Therefore, reducing their consumption guarantees such a goal. In this context, the use of adaptive setpoint temperatures allows such energy consumption to be significantly decreased. However, having reliable data from an external temperature probe is not always possible due to various factors. This research studies the estimation of such temperatures without using external temperature probes. For this purpose, a methodology which consists of collecting data from 10 weather stations of Galicia is carried out, and prediction models (multivariable linear regression (MLR) and multilayer perceptron (MLP)) are applied based on two approaches: (1) using both the setpoint temperature and the mean daily external temperature from the previous day; and (2) using the mean daily external temperature from the previous 7 days. Both prediction models provide adequate performances for approach 1, obtaining accurate results between 1 month (MLR) and 5 months (MLP). However, for approach 2, only the MLP obtained accurate results from the 6th month. This research ensures the continuity of using adaptive setpoint temperatures even in case of possible measurement errors or failures of the external temperature probe

Generation of recycled aggregates and technical requirements for some applications

In the present framework of sustainable construction, management of construction and demolition (C and amp;D) waste or debris is stressed and its correct implementation requires a previous estimation of the precise quantities and detailed composition of C and amp;D waste.This allows us to make an estimate of the production of recycled aggregate and to analyze the impact of its use in relation to the use of natural aggregate. Research of existing bibliography, the results obtained from both experimental testing and previous experience at construction works where C and amp;D debris is used, enabled us to develop technical specifications for each application of the recycled aggregates. This includes recommendations for use, quality control specifications, and the maximum percentage of recycled aggregate that ought to substitute natural aggregate in concrete mixes in order to get admissible performances