Assessment of lime-cement mortar microstructure and properties by P- and S- ultrasonic waves

Lime-cement mortars are used for repairing building walls, improving thermal and acoustic performance through the modification of their composition and, consequently, their microstructure and properties. In order to evaluate the applicability of ultrasonic (US) waves to better understand the relationships among composition-microstructure-properties, an experimental program using transmission P- and S- waves was carried out. The properties of ten mortars were assessed by US parameters as velocity, moduli and attenuation coefficient. Water to binder ratio, porosity and thermal conductivity showed good correlation to US modulus while S-wave attenuation was linked to sound absorption and the incorporation of fibres. Flexural strength correlated to P-wave attenuation, while a combination of S-wave attenuation and moduli was needed to adjust compressive strength. These correlations can be useful tools for predictive models development, composition optimization and US on-site evaluation.The authors wish to acknowledge the financial support for this Research, provided by the Grant for training of Lecturers (FPU-UAH 2013), funded by University of Alcalá. Some of the components were supplied by BASF Construction Chemicals España S.L., Omya Clariana S.L. and Readymix-Asland S.A

A multiscale model for pervious lime-cement mortar with perlite and cellulose fibers

A pervious lime-cement mortar (PLCM) with perlite (P) and cellulose fibers (FC) was studied for better understanding the relationships among mortar composition, microstructure and properties, especially thermal and acoustic performance. Mortar microstructure was studied by optical and scanning electron microscopy, water absorption and nitrogen adsorption/desorption tests. A multiscale model for PLCM with and without P and/or FC was proposed: a three-phase macrostructural model consisting on a gap-graded aggregate, a paste shell and a continuous void network; paste phase was described as a multiphase microstructure. Paste thickness and active void size were identified as PLCM macrostructural parameters. The use of P and FC widened the paste shell, reducing the active void size. While the effect of P depends on particle size rather than the proportion used, the effect of FC depended on fiber amount. The model could be useful for optimizing the design of PLCM and predicting thermal and acoustic performance.Financial support for this research was provided by the Grant for training of Lecturers (FPU-UAH 2013), funded by University of Alcalá. Some of the components were supplied by Omya Clariana S.L. and Cementos Portland Valderrivas S.A

Acoustic Assessment of Multiscale Porous Lime-Cement Mortars

Noise pollution is an issue of high concern in urban environments and current standards and regulations trend to increase acoustic insulation requirements concerning airborne noise control. The design and development of novel building materials with enhanced acoustic performance is an efficient solution to mitigate this problem. Their application as renders and plasters can improve the acoustic conditions of existing and brand-new buildings. This paper reports the acoustic performance of eleven multiscale porous lime-cement mortars (MP-LCM) with two types of fibers (cellulose and polypropylene), gap-graded sand, and three lightweight aggregates (expanded clay, perlite, and vermiculite). Gap-graded sand was replaced by 25 and 50% of lightweight aggregates. A volume of 1.5% and 3% of cellulose fibers were added. The experimental study involved a physical characterization of properties related to mortar porous microstructure, such as apparent density, open porosity accessible to water, capillarity absorption, and water vapor permeability. Mechanical properties, such as Young?s modulus, compressibility modulus, and Poisson?s ratio were evaluated with ultrasonic pulse transmission tests. Acoustic properties, such as acoustic absorption coefficient and global index of airborne noise transmission, were measured using reduced-scale laboratory tests. The influence of mortar composition and the effects of mass, homogeneity, and stiffness on acoustic properties was assessed. Mortars with lower density, lower vapor permeability, larger open porosity, and higher Young?s and compressibility modulus showed an increase in sound insulation. The incorporation of lightweight aggregates increased sound insulation by up to 38% compared to the gap-graded sand reference mixture. Fibers slightly improved sound insulation, although a small fraction of cellulose fibers can quadruplicate noise absorption. The roughness of the exposed surface also affected sound transmission loss. A semi-quantitative multiscale model for acoustic performance, considering paste thickness, active void size, and connectivity of paste pores as key parameters, was proposed. It was observed that MP-LCM with enhanced sound insulation, slightly reduced sound absorption.Financial support for this research was provided by Comunidad de Madrid and the Universidad de Alcalá (Spain), as part of the project IndoorComfort (CM/JIN/2019-46) under the Research Program for the Promotion of Young Researcher

Control de Gestión. Cuadro de Mando Integral para la Bodega Protos.

El Cuadro de Mando Integral es un instrumento que ayuda a la obtención de las estrategias formuladas por la empresa mediante cuatro perspectivas claves: financiara, del cliente, del proceso interno y, de aprendizaje y crecimiento. Para ello cada una de dichas perspectivas presenta una serie de objetivos estratégicos a alcanzar, cuyos resultados son medidos a través de indicadores, los cuales presentan unas metas a alcanzar por la empresa. Todo ello se determina mediante el análisis del Balance de Situación y de la Cuenta de Pérdidas y Ganancias, junto con sus respectivos ratios para la obtención del presupuesto previsional para el año 2014. La empresa elegida para la realización del Cuadro de Mando es la Bodega Protos.Departamento de Economía Financiera y ContabilidadGrado en Administración y Dirección de Empresa

Early age monitoring and hardened properties of SCC with limestone filler and active mineral additions

An experimental program on SCC with limestone filler and three active mineral additions (AMA), microsilica (MS), nanosilica (NS) and Metakaolin (MC), was carried out to evaluate their influence during early ages and in the hardened state. The aim was to characterize SCC further than the usual workability and mechanical parameters, in the understanding that the main microstructural changes in the material occur during the first hours and that early age cracking, porosity, pore size and permeability can compromise SCC durability. In-situ temperature, ultrasonic pulse velocity, mass loss and free drying shrinkage of samples subjected to a wind flow were simultaneously monitored for 24 hours. Profiles of the reaction process, the microstructural evolution and the physical effects of water evaporation were obtained. The early age measured parameters were related to a reaction index (Ir,24), defined as the fraction of heat produced (accumulated plus released) with regard to the total heat at 24 hours. The simultaneous monitoring of those parameters allowed a better understanding of the mechanisms involved during early ages. These parameters were compared to the early age cracking due to drying shrinkage. In the hardened state, a mechanical characterization was conducted and porosity and vapor permeability were measured on paste samples (without aggregates) under two environmental conditions during setting process: subjected to 3 m/s air flow and covered with a plastic film. The use of AMA increased mechanical strength. Although, the early age cracking risks also increased, especially in the case of AMA with smaller particle size (NS and MC). The external conditions applying on the samples during early ages also modify porosity, pore size and permeability of the hardened SCC

Early age and hardened performance of cement pastes combining mineral additions

To asses the influence of mineral additions (MA) at early age and on hardened performance of fluid cement based pastes, an experimental program was carried out. The design of the mixtures correspond to paste compositions used in self compacting concretes of moderated strength, as those employed for architectural applications. Two types of fillers (limestone and quartzite) have been used to substitute 50 % of cement in a reference paste, with and without a high range water reducing admixture (HRWRA). Then, three active MA (microsilica, nanosilica and metakaolin) were combined. A physical and mechanical characterization in the hardened state showed that the inclusion of MA to a cement-filler mixture can moderately improve the hardened performance of the pastes. Air and water cured samples were tested in order to evaluate the influence of curing conditions.\ud At early ages (24 hours), in-situ temperature and ultrasonic pulse velocity (UPV) were monitored on samples with limestone filler, combined with the three active MA, to study the reaction process and microstructure development, respectively. The reaction degree of the samples under study during the first 24 hours was related to the microstructure development. Evaporation, drying shrinkage and cracking at early age were also monitored, considering an air flow of 3 m/s on the exposed sample surface. Some relations were described linking cracking risks at early ages with the chemical and physical phenomena involved at early age microstructure evolutio

Influence of nanoclays on flowability and rheology of SCC pastes

SCC rheology is the key factor of fresh performance and its control is required to overcome cast in place issues regarding pumping and formwork lateral pressure that still limits its widespread use. Nanoclays are good candidates to improve rheological properties of cement pastes as yield stress, viscosity and thixotropy, controlling paste flow behavior. However, some interactions between nanoclays and admixtures can limit their efficiency. In this study, a comparative analysis on rheology and flowability of SCC cement pastes blended with limestone filler and 2 % by cement weight of four types of nanoclays, attapulgite, bentonite, and sepiolite in powder form and dispersed in water, is presented. Two water to binder ratios (w/b), 0.35 and 0.45, were considered and a high range water reducing admixture (HRWRA) was used to reach the required flowability. Water adsorption of nanoclays, flowability and rheological properties of SCC cement pastes with nanoclays were evaluated. It was found that HRWRA was less effective on pastes with nanoclays and low w/b, particularly bentonite. Sepiolite showed larger water adsorption and higher enhancing of rheological properties. It was observed that, the relation of nanoclays and HRWRA was decisive to produce flowability on pastes with low w/b. Besides, flowability was deeply affected by w/b, as water saturation of nanoclays increased HRWRA efficiency. All nanoclays modified rheological properties due to its different particles morphology characteristics, however sepiolite showed the largest effects and reached the higher values of yield stress, viscosity and thixotropy ratios used

Evaluation of the energy storage capacity of Phase Change Material cement-lime mortars by using heat flux meters and ultrasonic pulse transmission

Materials with high energy storage capacity can enhance energy efficiency of buildings further than thermal insulation alone. The use of microencapsulated paraffin wax Phase Change Materials (PCM) in cement-lime mortars with cellulose fibres and lightweight aggregates (LWA) is a promising solution for this purpose. In this study, experimental techniques as flux heat meters and ultrasonic pulse transmission are used to evaluate the thermal performance and energy storage capacity of five cement-lime mortars with 20% of PCM, cellulose fibres and LWA (perlite) under different thermal conditions. A climatic chamber was used to simulate heating and cooling on one side of a sample plate of each mortar type, while the other side remained at lab conditions. Sample plates were instrumented with temperature-humidity sensors, heat flux meter plates and Ultrasonic (US) pulse transducers. US attenuation coefficient was used to identify the phase change PCM from solid to liquid and vice versa, during heating and cooling. The Heat flux difference between both sides of the plates was also measured during heating and cooling cycles. The specific enthalpy (energy storage capacity) of the mortars was calculated for heating and cooling cycles. Mixtures with LWA and PCM showed the best thermal performance achieving larger heat storage capacity than mortars with fibres or the combination of both LWA and fibres.Financial support for this research was provided by the Research Program for the Promotion of Young Researchers, co-funded by Comunidad de Madrid and the University of Alcala (Spain), as part of the project IndoorComfort (CM/JIN/2019-46

Early age behaviour of Self Compacting Concrete with Polypropylene fibers and carbon nanofibers

An experimental study on the performance of a self compacting concrete (SCC) with fibers, during the cement hydration process and the evolution in to a rigid material, was carried out. The aim of this study was to investigate the improvement of the hardened performance due to the use of fibers and the early age cracking control ability of fibers at two different scales: on a nano-structural level with the addition of carbon nano-fibers (CNF) and on a micro-structural level with the addition of polypropylene micro-fibers. The inclusion of nanofibers increased the flexural strength of cement based pastes although some problems concerning early age cracking emerged. As any other concrete, SCC can exhibit problems during the very early ages after mixing, when cement hydration occurs, as shrinkage and early cracking. Although these problems arise during early ages, their effect can seriously compromise the long term performance and durability of the material. SCC samples with and without fibers were monitored through its hardening process using several experimental techniques and considering the effect of water evaporation due to wind exposition during the setting process. The effect of the fibers and different SCC components, as nanosilica, and a high range water reducing admixture (HRWRA), was analysed. Besides, the ability of the applied components to avoid the stress development during the early ages was also evaluated. The influence of the fibers and additional components on the early age shrinkage was assessed, identifying the relationship between shrinkage and early age cracking

Early age monitoring and hardened properties of SCC with limestone filler and active mineral additions

An experimental program on SCC with limestone filler and three active mineral additions (AMA), microsilica (MS), nanosilica (NS) and Metakaolin (MC), was carried out to evaluate their influence during early ages and in the hardened state. The aim was to characterize SCC further than the usual workability and mechanical parameters, in the understanding that the main microstructural changes in the material occur during the first hours and that early age cracking, porosity, pore size and permeability can compromise SCC durability. In-situ temperature, ultrasonic pulse velocity, mass loss and free drying shrinkage of samples subjected to a wind flow were simultaneously monitored for 24 hours. Profiles of the reaction process, the microstructural evolution and the physical effects of water evaporation were obtained. The early age measured parameters were related to a reaction index (Ir,24), defined as the fraction of heat produced (accumulated plus released) with regard to the total heat at 24 hours. The simultaneous monitoring of those parameters allowed a better understanding of the mechanisms involved during early ages. These parameters were compared to the early age cracking due to drying shrinkage. In the hardened state, a mechanical characterization was conducted and porosity and vapor permeability were measured on paste samples (without aggregates) under two environmental conditions during setting process: subjected to 3 m/s air flow and covered with a plastic film. The use of AMA increased mechanical strength. Although, the early age cracking risks also increased, especially in the case of AMA with smaller particle size (NS and MC). The external conditions applying on the samples during early ages also modify porosity, pore size and permeability of the hardened SCC