Construction materials are the most widely used materials for civil infrastructure in our daily lives. However, from an environmental point of view, they consume a huge amount of natural resources ...and generate the majority of greenhouse gasses. Therefore, many new and novel technologies for designing environmentally friendly construction materials have been developed recently. This Special Issue, “Environment-Friendly Construction Materials”, has been proposed and organized as a means to present recent developments in the field of construction materials. It covers a wide range of selected topics on construction materials.
Construction materials are the most widely used materials for civil infrastructure in our daily lives. However, from an environmental point of view, they consume a huge amount of natural resources ...and generate the majority of greenhouse gasses. Therefore, many new and novel technologies for designing environmentally friendly construction materials have been developed recently. This Special Issue, “Environment-Friendly Construction Materials”, has been proposed and organized as a means to present recent developments in the field of construction materials. It covers a wide range of selected topics on construction materials.
Construction materials are the most widely used materials for civil infrastructure in our daily lives. However, from an environmental point of view, they consume a huge amount of natural resources ...and generate the majority of greenhouse gasses. Therefore, many new and novel technologies for designing environmentally friendly construction materials have been developed recently. This Special Issue, “Environment-Friendly Construction Materials”, has been proposed and organized as a means to present recent developments in the field of construction materials. It covers a wide range of selected topics on construction materials.
A model system consisting of sodium caseinate (SC) + xanthan A- a low volume fraction of oil-in-water emulsion droplets was studied. The phase separation behaviour of xanthan + sodium caseinate was ...investigated as function of these two variables, followed by experiments on the same systems where oil droplets were introduced. More than 20 mM Ca2+ was needed to induce phase separation at pH 6.4 and 5.9, but at pH 5.4, phase separation occurred at as low as 5 mM Ca2+ and a lower concentration of SC or xanthan was required to induce phase separation. An increase in size of sodium caseinate aggregates is proposed as the main factor promoting phase separation. When oil droplets stabilized by sodium caseinate were added to systems containing 0.05a0.1 wt.% xanthan at pH 6.4 this appeared to inhibit significantly the phase separation of the mixtures at Ca2+ = 22 mM. Simple calculations showed that this effect cannot reasonably be due to excessive accumulation of protein at the droplet surfaces, which is then carried away by the droplets due to creaming. Consequently, a possible mechanism of the inhibition is accumulation of droplets at and strengthening of, the waterawater interface of the caseinateaxanthan phase separating entities.
The tunability feature of short-cavity vertical-cavity surface-emitting lasers in the C-minus band to provide low-power, cost-efficient, colourless, and legacy system compliant transmitters for ...future time and wavelength division multiplexed passive optical networks is investigated. For the first time, a report is presented on error-free performances across a 800 GHz tuning range with a potential aggregate upstream capacity of 80 Gbit/s over a system reach of at least 40 km and with a 1:64 split ratio. PUBLICATION ABSTRACT
•Physical and mechanical properties of recycled concrete aggregates.•The frost resistance of aggregates subjected to freezing/thawing cycles in water.•Prediction of the properties of aggregates ...whatever their origins by Voigt’s model.•Establishment of relationship between the properties of concrete and those of gravels.
This research aims to analyze the quality and suitability of recycled concrete aggregates (RCA) produced by crushing concrete blocks provided from building demolition waste by comparison to natural ones in providing concretes for building structures. For each granular type, sieving, water absorption, porosity, Los Angeles and Micro-Deval tests were conducted before and after their exposure to freezing/thawing. Results show that the rules of mixtures (Voigt’s model) can be used to predict all the studied properties of granular mixes (natural gravels+recycled gravels) except for the prediction of Micro-Deval index. Relationships are established between physical and mechanical characteristics of aggregates. The analysis of the frost resistance performance show that recycled concrete gravels are less resistant to freeze/thaw than natural one but their degradation, estimated through water absorption, porosity and Micro-Deval index, is not significant. Furthermore, the influence of RCA on mechanical properties of recycled aggregates concretes (RAC) is investigated. It appears that porosity and young’s modulus of RAC are significantly affected by the porosity of the granular mixture and consequently of RCA. The compressive strength of RAC is dependent on the Los Angeles coefficient of gravels while tensile splitting strength depends on the porosity of concretes related to that of the granular mixture.
Concrete is classified as a multi-composite material comprising three phases: coarse aggregate, mortar, and interfacial transition zone (ITZ). Fine and coarse aggregates occupy approximately 70-85% ...by volume, of which coarse aggregate typically constitutes more than two-thirds of the total quantity of aggregate by volume. The current study investigates the concrete performance produced using various recycled construction and by-product industrial waste coarse aggregates. Six types of coarse aggregates: manufactured limestone, quartzite, natural scoria, by-product industrial waste aggregate, and two sources of recycled concrete aggregates with densities ranging from 860 to 2300 kg/m
and with different strength properties were studied. To determine the coarse aggregate contribution to the overall concrete performance, lean and rich concrete mixtures (Mix 1 and Mix 2) were used. Mix 1 (lean mixture) consisted of a ratio of water to cement (w/c) of 0.5 and cement content of 300 kg/m
, whereas a higher quantity of cement of 500 kg/m
and a lower w/c ratio of 0.3 were used for Mix 2 (rich mixture). The results showed that while the compressive strength for different aggregate types in Mix 1 was comparable, the contribution of aggregate to concrete performance was very significant for Mix 2. Heavyweight aggregate produced the highest strength, while the lightweight and recycled aggregates resulted in lower mechanical properties compared to normal weight aggregates. The modulus of elasticity was also substantially affected by the coarse aggregate characteristics and even for Mix 1. The ACI 363R-92 and CSA A23.3-04 appeared to have the best model for predicting the modulus of elasticity, followed by the ACI-318-19 (density-based formula) and AS-3600-09. The density of coarse aggregate, and hence concrete, greatly influenced the mechanical properties of concrete. The water absorption percentage for the concrete produced from various types of aggregates was found to be higher for the aggregates of higher absorption capacity.
It is necessary to ensure the properties of recycled aggregate concrete (RAC) can meet the requirements of those for the corresponding natural aggregate concrete (NAC), since only in such cases ...recycled aggregates (RA) may be accepted for structural use. This study aims to propose a modified design method of RAC based on aggregate gradation readjustment (AGR). It tries to maintain the effective amounts of both the coarse and fine aggregates of RAC similar to that of the NAC after concrete mixing as it is well known that due to the weakness of the old attached mortar to RA, the gradation of the aggregates would be undesirably changed. Two series of concrete mixtures were conducted. One was to examine the variations of the compressive strength and porosity along with the aggregate adjustment ratio using a single RA source; while the other one was used to verify the effect of the proposed AGR method through the investigation of concrete properties made with RAs obtained from different sources. The results show that the proposed method was beneficial to improving all the properties of RAC investigated.
•The stress–strain behavior of steel spiral confined NAC, RAC and TRAC is studied.•General stress–strain model of steel spiral confined NAC, RAC and TRAC is developed.•A relationship is provided to ...calculate the permissible content of any source of RCA.
Utilizing the confinement from transverse reinforcement of compression members to offset the inferior recycled aggregate concrete (RAC) performance is considered a sustainable and adaptable way to solve the problems related to the application of recycled coarse aggregates (RCA). Prediction of the axial stress–strain behavior of RAC is a challenging task due to variation in the physical properties of RCA from different sources. Currently, limited work is available in the literature to predict the axial stress–strain behavior of steel spiral confined RAC applicable to RCA from different sources. In this study, a general axial stress–strain model of steel spiral confined normal aggregate concrete (NAC), RAC and treated recycled aggregate concrete (TRAC) is developed considering the material characteristics of RCA. For this purpose, the axial stress–strain behavior of steel spiral confined NAC, RAC, and TRAC having different target strengths and confinement levels is studied. The results of this study show that confinement has a more prominent effect on peak and ultimate strains of RAC and TRAC than NAC. The axial stress–strain model developed in this study, considering a large test database, can be used to predict the performance of steel spiral confined NAC, RAC, and TRAC for any source/type of RCA leading towards the development of design guidelines for sustainable RAC members. Moreover, a relationship is also provided to calculate the permissible content of RCA having any type/source to achieve the compressive strength of steel spiral confined RAC or TRAC similar to NAC for any confinement pressure and concrete strength.
The title compound, 3C6H4N4O2S2.2C3H7NO.4H2O, comprises three 2,2'-disulfanylidene-5,5'-biimidazoli dinylidene-4,4'-dione molecules, two dimethylformamide molecules and four water molecules arranged ...around a crystallographic inversion centre. The non-H atoms within the 5,5'-biimidazolidinylidene molecule are coplanar and these molecules aggregate through N-H...S hydrogen-bonding interactions with cyclic motifs graph set R22(8), giving two-dimensional ribbon structures which are close to being parallel. The two independent water molecules associate to form centrosymmetric cyclic hydrogen-bonded (H2O)4 tetrameric units graph set R44(8). The ribbon structures extend along the a axis and are linked through the water tetramers and the dimethylformamide molecules by a combination of two- and three-centre hydrogen bonds, giving an overall three-dimensional structure.
