Buffer Value Research Articles

Pilot scale cellulose recovery from sewage sludge and reuse in building and construction material

The recovery of cellulose in toilet paper from municipal wastewater is one of the most innovative actions in the circular economy context. In fact, fibres could address possible new uses in the building sector as reinforcing components in binder-based materials. In this paper, rotating belt filters were tested to enhance the recovery of sludge rich in cellulose fibres for possible valorisation in construction applications. Recovered cellulosic material reached value up to 26.6 gm−3 with maximum solids removal of 74%. Content of cellulose, hemicellulose and lignin was found averagely equal to 87% of the total composition. Predictive equation of cellulosic material was further obtained. The addition of recovered cellulose fibres in mortars bring benefits in terms of lightness, microstructure and moisture buffering value (0.17 g/m2%UR). Concerning mechanical properties, flexural strength was improved with the addition of 20% of recovered cellulose fibres. In addition, a simplified economic assessment was reported for two possible pre-mixed blends with 5% and 20% of recovered fibres content.

Moisture Buffering of Multilayer Internal Wall Assemblies at the Micro Scale: Experimental Study and Numerical Modelling

In this paper, a series of experiments assessing the moisture buffer value (MBV) of four internal wall assembly samples made from hygroscopic materials was performed. A modified Nordtest protocol was used. Moisture buffer values of all the investigated wall assemblies, with varying moisture loads in the range of 50% to 80%, showed a moderate moisture buffer value (MBV: 0.5–1.0 (g·m−2·%RH−1)). The results showed that in a wall assembly where the MBV of the whole assembly is lower than the MBV of the outer layers, the moisture-buffering capacity of the inner layer is untapped. Outer layers affect inner layers by changing their moisture-buffering capacity, which in turn changes the overall performance of the whole assembly. In addition, it was observed that if the penetration depth value of the outer layer is greater than its thickness, vapour reaches into the deeper layer and wall assemblies made of layers with materials characterized by a lower value of penetration depth reach steady state more slowly. The WUFI Pro tool was used to compare the simulated and experimental results. Despite the discrepancies between these results, it offers a simplified method, helping designers make decisions about which materials to choose to improve the moisture-buffering effect.

Influence of types of binder and plant aggregates on hygrothermal and mechanical properties of vegetal concretes

Bio-aggregate based building materials offer promising perspectives thanks to their low environmental impact and interesting hygrothermal behaviour. In this paper, different formulations of bio-aggregate concrete are proposed and analysed. We focus on two types of locally available bio-aggregates, namely maize and sunflower bark chips, and two types of binder matrices, based on respectively metakaolin and lime. The study specifically focuses on the pore structure of the composite material, as this quantity has a decisive impact on the insulating properties (thermal conductivity), the hygric behaviour (sorption isotherms, water vapour permeability and moisture buffer value) as well as on the mechanical performance (compressive strength). The results underline the impact of the constituents’ porosity on the complex porous structure of the bio-concrete and the influence of porosity on its performance. The findings demonstrate that metakaolin and sunflower are high-potential raw materials for the design of a bio-aggregate based concrete.

Experimental investigation of thermal properties and moisture buffering performance of composite interior finishing materials under different airflow conditions

The thermal and humidity environment of indoor air affects the health and comfort of building occupants and the durability of building structures. One potential solution for moderating the thermal and humidity environment is provided by functional materials used for interior finishing, if it can passively buffer heat and moisture. Considering that airflow occurs at all times and locations in buildings, this study focused on the moisture buffering performance under different airflow conditions. A gypsum board was used as a hygroscopic material for interior finishing and was mixed with a microencapsulated phase change material (MPCM) to prepare composite hygroscopic MPCMs. The biomass painting material was another functional material for interior finishing and was prepared by blending scallop shell powder and a PCM slurry. Their thermal properties, such as the thermal conductivity and enthalpy, were tested, along with the hygroscopic properties, such as the pore-size distribution, equilibrium moisture content curve, and water vapor permeability. Scanning electron microscopy indicated that the MPCMs adhered well to and were retained on the laminated structure of the gypsum board. The moisture buffering performance of each sample was tested, and the results indicated that the maximum moisture absorption/desorption of each sample increased with the airflow rate. The ideal moisture buffering value (MBVideal) and practical moisture buffering value (MBVpractical) of each sample were determined and compared in different cases. Additionally, a simple linear model for MBVpractical and the airflow rate was established to predict the influence of the airflow rate on MBVpractical.

Separation of deamidated peptides with mixed-mode chromatography using phospholipid-functionalized monolithic stationary phases

Deamidation of asparagine (Asn) residues of monoclonal antibodies (mAbs) plays a pivotal role in the in vivo/vitro degradation or efficacy loss of biopharmaceuticals. However, a major challenge for MS analysis of deamidation of Asn-containing peptides in mAbs, is due to the fact that there is only a 1 Da mass shift between the native form (Asn residues) and deamidated forms (n-aspartyl (n-Asp) and isoaspartyl (isoAsp) residues with identical mass). Therefore, a chromatographic separation of the deamidated proteins and/or the peptides derived therefrom is needed prior to MS analysis. In this study, the monolithic column with various stationary phases, including reverse phase (RP), single phospholipid-functionalized and mixed phospholipid-functionalized monoliths, were prepared for the separation of the deamidation-sensitive signature peptide (IYPTNGYTR) of trastuzumab and its two deamidated products, n-Asp55 residue IYPTDGYTR and isoAsp55 residue IYPTisoDGYTR. Compared to the RP monolith, the phospholipid-functionalized monoliths provided mixed-mode interactions and exhibited better peak shape and separation selectivity. The effect of the parameters, including the type and concentration of buffer, temperature and pH value on the separation performance were investigated. Under the optimal conditions, the three peptides were fully separated on a mixed phosphocholine (PC) / phosphatidic acid (PA) functionalized monolith (poly (MDPC60PA40-co-EDMA)) due to the joint contribution of hydrophobic and electrostatic interactions. Therefore, the novel method based on the mixed phospholipids-functionalized monolithic column exhibited good potential for the analysis of deamidated peptides, which will be useful for the in-depth study of post-translational modifications of mAbs.

Properties of multifunctional lightweight mortars containing zeolite and natural fibers

The article focuses on the development of innovative and multifunctional mortars with low environmental impact for indoor applications acting as passive systems to moderate extremes of humidity and to lower the concentration of pollutants. Mortars are manufactured by keeping constant the water/binder ratio, using sand as reference aggregate, and by replacing the total volume of sand with zeolite. In some mixes the aggregate, is also at 25vol% by wool natural fibers. Regardless lightness, zeolite thanks to its pozzolanic activity, helps to improve the compressive strength of mortars manufactured with wool fibers. In addition, the combination of zeolite and wool increases the hygro-thermal performance of mortars: water vapor resistance factor (22% lower than the reference), moisture buffering value (100% higher than the reference), and thermal conductivity (66% lower than the reference), respectively. Depolluting properties of zeolite-based mortars, in terms of adsorption capacity, are 65% lower than that of reference mortar.

Dynamic behaviour of bio-based and recycled materials for indoor environmental comfort

Abstract UK construction industry contributes 120 Mt of waste every year. Bio-based building materials may be a solution for this problem, as they combine re-use and recycling abilities together with hygroscopic characteristics, leading to buildings energy savings. For the first time, the dynamic response to hygrothermal changes of bio-based materials is examined in terms of Moisture Buffering Value (MBV), dry/wet thermal conductivity, microstructure, density and latent heat through daily cycles. It is shown that MBV is a useful tool for characterisation but needs to be combined with the shape of the change in mass of the final hygrothermal cycle. Mastering this is required to obtain significant improved indoor environment quality in buildings. Ten samples of bio-based insulation materials and one thermoplastic recycled polymer were analysed (wool, hemp, saw mill residue, wood, straw, cork and polyethylene terephthalate). Saw and wool are the most promising, as materials exhibit dynamic response to hygrothermal changes. Only half the amount of samples revealed equivalent efficient moisture transfer to be able to desorb the adsorbed quantity of water. Latent heat of vaporisation and condensation tests led to the conclusion that samples of wool and saw mill residue can qualify as bio-based materials for ‘green’ panels.

Chemical composition and in vitro rumen fermentation of ensiled sugar industry coproducts

he current study aims to compare sugar beet leaves (SBLs) ensiled with sugar beet pulp (SBP), sugarcane molasses (SM), or rock candy juice (RCJ) using an in vitro gas production technique. Treatments in the first group included 10% SBP (control 1) and control 1 plus 5% SM or RCJ. In the second group, there were 3 treatments, including 20% SBP (control 2) and control 2 plus 10% SM or RCJ. The silages with no added soluble carbohydrate (SC) sources had significantly higher (P < 0.001) pH, buffer value index, and ammonia nitrogen values than the other treatments. However, there was no significant difference between RCJ and SM in their effect on these variables. Adding both levels of SC sources caused an increase in dry matter digestibility compared to those that only included SBL and SBP (P < 0.001). Maximal and rate of gas production from slowly fermentable fraction (a$_{2}$) were significantly greater when the substrate contained 85%, 10%, and 5% SBL, SBP, and SC sources, respectively. Using dried SBP and SC sources for the preservation of fresh SBL is recommended; however, with higher levels of SC, the silage may be at risk of spoilage, and it must be less exposed to air.

Characterization of beet-pulp fiber reinforced potato starch biopolymer composites for building applications

This work deals with the making of a new renewable green material for building insulation from sugar beet pulp and potato starch. The material is both lightweight and ecofriendly. The influence of starch/extruded sugar beet pulp mass ratio (S/EBP) is studied. Four mass ratios are considered, 10, 20, 30 and 40% (relative to the starch). Samples are characterized in terms of absolute and bulk density, sound absorption coefficient, compressive and flexural strength, as well as and hygrothermal properties (the moisture buffering value and thermal conductivity). The sound absorption coefficient shows that this material is a good sound absorber, especially in medium and high frequencies. The sound absorption capacity depends on the fiber content and the humidity content. The best values are between 0.6 and 0.8. The compressive strength increases linearly with the S/EBP weight ratio to reach 0.52 MPa and the compressive strain is 30%. The elasticity modulus and the Poisson’s ratios were also studied. The transversal and vertical strain were measured using ARAMIS optical system. The moisture buffering value was measured according to Nordtest Protocol. The recorded moisture buffering value was between 2.6 and 2.8 g/(%RH.m2) and shows that the sugar beet pulp-starch composite is an excellent hygric regulator. The thermal conductivity is to around 0.070 W/(m·K). The results obtained shows that increasing starch amount tends to decrease composite porosity but increases thermal conductivity and mechanical properties. Depending on the starch content, beet pulp composites have a good thermal and acoustical performance and can be used as building materials.

Research on the Comprehensive Performance of Hygroscopic Materials in an Office Building Based on EnergyPlus

This paper presents the research status of hygroscopic materials, points out the weak links as targets for major breakthroughs, and introduces humidifying mechanisms and their categories. In this paper, we simulated a single-monomer Shenyang office building with different envelopes of inner-surface hygroscopic materials for indoor humidity conditions, energy consumption, and economy, which are three aspects of energy consumption analysis in EnergyPlus software. To obtain the best moisture buffering performance from hygroscopic materials, we also simulated different cases including the laying area, ventilation strategy, thickness, and initial moisture content of different hygroscopic materials. The humidity fluctuation, with changes in the style of hygroscopic materials and usage conditions, of a room in a building can be analyzed by numerical simulation. This allows the determination of the best moisture buffering performance of the building structure. The results show that hygroscopic materials have great advantages in three energy saving aspects of building assessment. Hygroscopic materials can regulate indoor air humidity and reduce energy consumption. In addition, the entire life-cycle cost can be minimized. Lower rates of air exchange and larger usable areas can help enhance the level of performance of hygroscopic materials. The thickness and initial moisture content of hygroscopic materials have little impact on the moisture buffering value. This study strived to provide a theoretical basis and technical guidance for the production and installation of hygroscopic materials. It also promoted the passive materials market and the building’s energy savings. The best moisture buffering performance, evaluated at room level in this paper, can be obtained through real-world environmental simulation.

Study on the Effects of Extraction and Purification Conditions on the Activity of Peroxidase and Polyphenol Oxidase from Chestnut Kernel and on Their Substrates

Chestnut kernel is a woody grain with high nutritional value and utilized value, but it is susceptible to Browning. Previous studies have shown that phenol is the substrate of enzymes that lead to browning. In order to investigate the substrates that that leads to browning of peroxidase (POD) and polyphenol oxidase (PPO) of chestnut kernel. The extraction and purification methods and the main substrates of POD and PPO from chestnut kernel were investigated. First, the effects on enzyme activity of different kinds of buffer, temperature, time and pH value were studied; second, the salting out purification of different concentrations and the main substrates of POD and PPO from chestnut were studied. The results were shown that POD enzyme in chestnut could be obtained by extracting with sodium dihydrogen phosphate-dibasic sodium phosphate buffer (pH 6.8) at 4°C for 5 h. PPO enzyme in chestnut could be obtained by extracting with disodium hydrogen phosphate-citric acid buffer (pH 5.4) at 4°C for 5 h. The two enzymes could be purified best by 80% ammonium sulfate, and the activity of POD and PPO enzyme had been enhanced for 60% and 190% respectively. Gallic acid might be the main substrate of POD and PPO in browning of chestnut kernel.

Hygric behaviour of a clay-Typha bio-based material for building

This study deals with the impact of the amount and granulates type of Typha Australis on the hygric performance of building material based on clay. Three compositions are tested: Two of them have the same proportion of granulate but differ by their morphology (transversal or longitudinal cut of the plant). The third composition contains less Typha granulates resulting from the transversal cut. Hygric properties are experimentally, such as permeability, sorption isotherms, and moisture buffering value. Results show an influence of the Typha granulate and its volume content on the hygrothermal properties of the material due to the porosity.

The effect of air velocity on moisture buffering

Hygoscopic finishing materials improve the indoor hygrothermal comfort and air quality, as they reduce the extremes of variation in relative humidity. This property, known as moisture buffering, is related to the capacity of hygroscopic materials to adsorb and desorb moisture from the air. Air velocity plays an important role on the sorption performances of materials: increasing the air speed leads to increased moisture buffering capacity. In order to obtain comparable results, several moisture buffering protocols require the air speed to be constant and around 0.1 m/s during tests. However, those tests are usually performed in climatic chambers, where air speed cannot be controlled and the flow may not be homogenous. The aim of this study is to demonstrate, that positioning test specimens in different locations within the same chamber gives different moisture buffering value results, due to the non-homogenous air speed distribution. For this reason, air velocity has been monitored, measuring the differential pressure and air speed in different locations in a climatic chamber. Moisture buffering tests have been performed in six locations of the chamber and a correlation between the two analyses has been evaluated. The significance of this paper is to understand the relationship between air speed and moisture buffering performances, in order to determine an air velocity correction factor, which enables the moisture buffering value to be evaluated when existing protocols cannot be adhered.

Hygrothermal characterization of a new bio-based construction material: Concrete reinforced with date palm fibers

Hygrothermal behavior of a new building material, composed of cement, sand and date palm fibers was investigated in the present work. In a first part, the sorption-desorption isotherms and the hysteresis effect were characterized under static conditions, and collected results revealed a high hydric capacity of this Date Palm Cement (DPC) mortar. In addition, the GAB model (Guggenheim-Anderson-de Boer) was successfully applied to describe the experimental sorption isotherm curve. In a second step, the moisture buffer value and the effect of temperature on successive adsorption/desorption cycles were assessed under dynamical conditions. It was found that the sorption process is highly affected by temperature. Finally, this bio-based mortar was classified as hygroscopic and breathable material with excellent moisture buffering capacity.

Waste-based geopolymeric mortars with very high moisture buffering capacity

In this study, lightweight waste-based geopolymeric mortars were evaluated for the first time regarding their potential to passively adjust indoor relative humidity (RH) levels. Geopolymer mortars were prepared using a mixture of fly ash (FA) and metakaolin (MK) as a binder, in a proportion of 75:25 wt% (FA:MK), construction and demolition waste as the fine aggregate and a pore forming agent in varying amounts. The results showed that the addition of a pore-forming agent to the compositions considerably increased the moisture buffer value (MBV) of the mortars, that is, from 0.80 (reference mortar) to 5.61 g/m2 Δ%RH (mortar with highest porosity). The moisture buffering capacity shown by these eco-friendly mortars is higher than values reported for other binder materials and can be classified as excellent (MBV > 2 g/m2 Δ%RH). The porous FA-based mortars also presented low thermal conductivity (as low as 0.19 W/m∙K), which suggests that these innovative binders could be simultaneously used for indoor moisture buffering and as low thermal conductivity materials.

Metal-organic framework MIL-100(Fe) as a novel moisture buffer material for energy-efficient indoor humidity control

Metal-organic frameworks (MOFs) are a new class of porous materials composed of a three-dimensional network of metal ions held in place by multidentate organic molecules. MIL-100(Fe) (molecular formula: Fe3O(H2O)2OH(BTC)2), as one kind of MOFs, has an excellent performance of water sorption due to the large specific surface areas and high porosity. The paper proposes an innovative application of MIL-100(Fe) as a new kind of moisture buffer material to control the indoor humidity passively. MOFs can moderate indoor moisture fluctuation, which will greatly reduce the energy consumption of HVAC systems and improve the building energy efficiency. In the paper, microstructure and moisture characterizations of MIL-100(Fe) have been carried out. The moisture buffer value (MBV) of MIL-100(Fe) has been measured and compared to the typical building materials. The results show that MIL-100(Fe) can absorb up to 15 g m−2·RH−1 at 8 h, which is 33 times higher than the laminated wood. A novel lumped model for building latent load simulation has been developed. The energy saving potential by using MOFs in a typical office in different climates was calculated. The results show that a 5 m2 MOF wall panel can remove most of the latent load in dry and moderate climates without any energy input; MOFs can be regenerated by night ventilation. In the hot and humid climate, the MOF materials can remove 73.4% of the latent load, and can be easily regenerated by using low-grade energy.

Building bio-insulation materials based on bamboo powder and bio-binders

Bio-insulating materials are well known to reduce the environmental impact of constructions and are able to regulate the indoor temperature and humidity of buildings. This study investigates the influence of high-absorbing bio-glues based on a protein and lignin compound on moisture transfer and storage as well as on thermal performance of bamboo particleboards. The investigations are based on the moisture buffer value, vapor permeability, isothermal vapor sorption and thermal conductivity. Simultaneously, the mechanical properties and mold growth of these materials, manufactured for the study, are also investigated. The results demonstrate excellent moisture buffer capacity, from 2.13 to 3.26 g/(m2·%RH). The vapor sorption isotherm results exhibit the materials’ high moisture storage, and the vapor permeability behaves like commercial bio-insulating materials. The thermal conductivity of particleboards shows a low value, in accordance with their density and variation in moisture content. In addition, the results indicate mold appearance on the surfaces of specimens after 14 days exposure to 84% relative humidity. Moreover, a comparison of the hygrothermal characterizations between bamboo particleboards and fiberboards (Nguyen et al., 2017) is carefully made to highlight the exceptional features of those bio-boards.

Design and properties of a new sustainable construction material based on date palm fibers and lime

Every year, huge quantities of date palm fibers (DPF) are produced and wasted all over the world. Using this natural fiber as raw material would contribute to the valorization of natural sustainable resources. This paper presents an experimental investigation of a new eco-material based on date palm fiber and lime. The experiments on the elaborated material investigate some mechanical, thermal, acoustic properties and moisture buffering capacity. The influence of the fiber/lime ratio on the behavior of the lightweight aggregate was studied systematically. The results of compressive strength testing indicated that PDF incorporation led to a reduction in resistance limit, however, the recorded average values are still acceptable. Also, it was observed that the thermal conductivity is sensitive to the variation of the fiber/lime composition ratio. The measured thermal conductivity reached a minimum of 0.091 W/m.K for samples of 50% fiber, which indicates that it can be used as a good thermal insulator. With regard to the sound absorption, the new material reveals good absorption capacity based on the measured sound absorption coefficient which is for 50% of fiber: for medium and high frequencies 0.65 and 0.55 respectively. Due to its porous morphology, the proposed material has the ability to absorb water vapor in a high relative humidity environment and to restore it in a dry one. Hence, it could therefore act as a hygric regulator. Measurements of moisture buffer value revealed that the material is classified as good or excellent depending on the percentage of fiber.

Rammed Earth incorporating Recycled Concrete Aggregate: a sustainable, resistant and breathable construction solution

Construction and demolition debris, mainly concrete and masonry rubble, represent a significant share of municipal waste. Recycling crushed concrete aggregates and using them as substitutes for natural ones might therefore be determinant in reducing landfilling and mineral resource depletion. An innovative way to give new value to Recycled Concrete Aggregates (RCAs) is to ram them in layers to form load-bearing walls for stabilised Rammed Earth (RE) applications. However, the success of those few existing RE projects using RCA is mainly due to the knowledge and experience of the contractors rather than official standards or guidelines or scientific literature. The objective of this study was to further the knowledge of this building technique by determining the effect of different RCA replacements on the material’s mechanical resistance, sustainability and hygroscopic properties: indicative of the structure’s structural, environmental and hygrothermal performance. Mechanical resistance was assessed by means of the Unconfined Compressive Strength (UCS, commonly used for rammed earth-like materials), hygroscopic properties via Moisture Buffer Value (MBV) and sorption isotherms while the sustainability was assessed via consequential Life Cycle Assessment (LCA). Microstructural investigations via mercury intrusion porosimetry, nitrogen adsorption-desorption isotherms, scanning electron microscopy and X-ray diffraction were performed to understand and explain material mechanical and hygroscopic behaviour. The building technique, already proven to be durable, was demonstrated to be resistant (from 4 to 12 MPa at 28 days depending on the RCA replacement and cement content), sustainable (down to 25 kg CO2-eq. of embodied carbon per square meter of load-bearing wall) and to have good moisture buffering abilities (0.88 g/(m2%RH) for mixtures containing only RCA). Strength appeared to be more related to the particle size distribution of the mix rather than to the percentage of RCA added. The amount and type of stabiliser added to the mix and the distance covered by the RCA during its lifetime strongly affected the environmental sustainability of the mixture; to maximise the potential of this building technique, reducing the amount of cement in the mixture by using alternative stabilisers should be the main priority.

Chemical and multi-physical characterization of agro-resources’ by-product as a possible raw building material

The aim of this paper is to find out the best valuation of agro-resources’ by-products as new alternative raw building materials that meet to sustainable development requirement. Five agro-resources are considered: flax, hemp, corn, rape and wheat. In the present work, the chemical characteristics of bio-aggregates are studied by FTIR, Van soest method and Phenol sulfuric method to identify their composition. The investigated physical properties are particle size distribution, density, porosity, water absorption, thermal conductivity and moisture buffer value. The studied materials differ on a chemical and a thermal point of view while they all are excellent hygric regulators. These results suggest that agro-resources can be used as a raw building materials for several types of use: as lightweight aggregates or as binder.