Durability of masonry systems: A laboratory study

We deal with the textural aspects, porometry and hydric behaviour of combinations of building materials and their durability under attack by salt crystallisation and freezing. We selected 4 types of lime mortar (pure lime mortar, lime mortar + air-entraining agent, lime mortar + pozzolana and lime mortar + air-entraining agent + pozzolana) which were used in combination with either brick or calcarenite stone. Lime mortars were chosen because they are compatible with traditional building materials, including the bricks and calcarenites that were widely used in the historical buildings that make up our architectural heritage. There are more similarities between the pore size ranges in calcarenites and mortars than there are between those in bricks and mortars. In all cases, a fine layer of calcite microcrystals develops at the contact surface between the mortar and the stone or brick. This is produced by the transformation of the portlandite, which concentrates in this area due to capillary moisture migration. This surface may on the one hand represent an obstacle to the flow of water between the different parts of the system formed by these materials, but on the other it may also favour greater adherence between the components, especially in the calcarenite + mortar combination, which proved to be the most resistant to deterioration in the freeze–thaw tests.     

The physical,chemical,and microscopic properties of masonry mortars from Alhambra Palace (Spain) in reference to their earthquake resistance

Al-Andalus mortar is an ancient binding material (lime mortar) that was used for centuries in numerous historical buildings in Al-Andalus,Granada (Spain).The physico-chemical and microscopic properties of Al-Andalusmortars in Granada were studied as part of an investiga-tion into the mineral raw materials present in the territory of Spain.Scanning electron microscope and X-ray diffraction analyses of eight main types of mortars were performed to show the presence of calcite, gypsum, quartz, and muscovite minerals with organic fibers. Chemical analyses of the specimens showed that high SiO2+Al2O3+Fe2O3 contents yielded high values of hydraulicity and cementation indices. A significant result of this study was that mortars with high hydraulicity and cementation indices have high mechanical strengths.This characteristic may be the main reason for the earthquake resistance of the historical Alhambra Palace.     

Influence of fine tailings on polyester mortar properties

The purpose of this study is to examine the basic properties of polyester mortars using a fine tailings (FT) from an abandoned mine as a filler. FT with sizes of 10–69 μm is obtained through the centrifugal separation of tailing (TA), and tested for such basic properties, as particle shape, fineness of size distribution, liquid resin absorption, and heavy metal leaching. Polyester mortars with FT and ground calcium carbonate (GC) are prepared with various filler-(filler + binder) ratios and replacements of GC with FT, and tested for working life, flexural and compressive strengths, and chemical corrosion resistance. As a result, FT has almost the same properties as GC in terms of particle shape, fineness of size and liquid resin absorption. The working life of polyester mortars is prolonged with an increased filler-(filler + binder) ratio and replacement of GC with FT. From the vantagepoint of the strength development of the polyester mortars with FT, it is recommended that the filler-(filler + binder) ratio and replacement of GC with FT should be controlled at 50% or less. Mass and strength changes are generally lower in mortars containing FT than in those containing GC in all chemical solutions.     

Improving hydraulic properties of lime–rice husk ash (RHA) binders with metakaolin (MK)

To improve long-term hydraulic properties of binders from RHA and lime, 25–75% MK was added to RHA. Binders were formulated and properties were compared to that containing RHA or MK as only pozzolans. The lime–pozzolan ratio was 1:3. The properties tested after 7, 28 and 56 days were: absolute density and fineness of the binders, initial setting time, chemical and mineralogical composition of hydrated binders, flexural and compressive strengths and water absorption of mortars. The micrographs of the hardened binder pastes at 56 days permitted to evaluate the densification of different matrixes and the development of pores. From the results obtained, it was concluded that, MK increased the density of mixtures and decreased their grindability. The presence of MK decreased the SiO₂ content of binders and increases their Al₂O₃ and Fe₂O₃ contents. Calcium-silicate hydrates (CSH) gel and gehlenite (C₂ASH₈) were the main phases formed during the pozzolanic reaction in the presence of MK. No reduction in flexural and compressive strengths was observed after 28 days for binders containing MK. The mixture of 25% MK and 75% RHA which is recommended gave flexural and compressive strengths higher than binder with RHA or MK as the only pozzolan. Water absorption of mortars was less than 20%.     

Effects of limestone replacement ratio on the sulfate resistance of Portland limestone cement mortars exposed to extraordinary high sulfate concentrations

A comparative study has been performed on the sulfate resistance of Portland limestone cement (PLC) mortars exposed to extraordinary high sulfate concentrations (200 g/l). PLCs have been prepared by using two types of clinkers having different C₃S/C₂S ratios and interstitial phase morphologies. Blended cements have been prepared by replacing 5%, 10%, 20% and 40% of clinker with limestone. Cubic (50 × 50 × 50 mm) and prismatic (25 × 25 × 285 mm) cement mortars were prepared. After two months initial water curing, these samples were exposed to three different sulfate solutions (Na₂SO₄ at 20 °C and 5 °C, MgSO₄ at 5 °C). Solutions were not refreshed and pH values of solutions were monitored during the testing stage. The compressive strength and length changes of samples have been monitored for a period of 1 year. Additional microstructural analyses have been conducted by XRD and SEM/EDS studies. Results indicated that in general, limestone replacement ratio and low temperature negatively affect the sulfate resistance of cement mortars. Additionally, clinkers of high C₃S/C₂S ratios with dendritic interstitial phase structure were found to be more prone to sulfate attack in the presence of high amounts of limestone.From the results, it is postulated that in the absence of solution change, extraordinary high sulfate content modified the mechanism of sulfate reactions and formation of related products. At high limestone replacement ratios, XRD and SEM/EDS studies revealed that while ettringite is the main deterioration product for the samples exposed to Na₂SO₄, gypsum and thaumasite formation were dominant products of deterioration in the case of MgSO₄ attack. It can be concluded that, the difference between reaction mechanisms of Na₂SO₄ and MgSO₄ attack to limestone cement mortars strongly depends on the pH change of sulfate solutions.     

Performance of limestone cement mortars in a high sulfates environment

With the aim of studying the influence of cement composition on resistance in high sulfates environment, standard mortars have been produced using ordinary Portland cement (CEM I – 32.5) and limestone cement with 35% limestone (CEM II/B-LL – 32.5). The pore size distribution of the cement pastes was measured. The mortars were immersed in a 5% Na₂SO₄ solution at 20 °C for 1.5 years and the caused deterioration was been visually observed at a regular basis. Furthermore, the mortars expansion was being estimated by measuring the change of length. At the end of the experiment the compressive strength of the mortars was measured. The deterioration products of the mortars have been identified by means of X-ray diffraction, optical microscopy and environmental scanning electron microscopy. The limestone cement based mortar presented cracking that started at the age of 6 months and continued throughout the experiment. It also displayed high expansion after 250 days of immersion in a 5% Na₂SO₄ caused, as proved using the analytical techniques, by the formation of gypsum and ettringite. Concluding, the cement with 35% limestone did not perform as well as ordinary Portland cement under the most aggressive laboratory conditions. Hence, it is obvious that the addition of limestone in the cement leads to a totally different behaviour than Portland cement with respect to the resistance in high sulfates environment.     

Evaluation of sulfate resistance of Portland and high alumina cement mortars using hardness test

Portland cement and high alumina cement mortar specimens were exposed to cycles of drying at 40 °C, cooling at 20 °C and immersion in Na₂SO₄ and MgSO₄ solutions at 20 °C. The resistance of mortars was evaluated by visual inspection and by measuring the change in surface hardness and weight of the specimens. The decrease and increase in surface hardness were observed in both mortars by treating with Na₂SO₄ and MgSO₄ solutions, respectively. The combined effect of the chemical and physical attack by Na₂SO₄ was attributed to the complete failure of Portland cement mortar, whereas only marginal damage of high alumina cement mortar was believed owing to physical salt crystallization. No damage was observed in both mortars treated with MgSO₄ solution.     

Study on early-age cracking of cement-based materials with superplasticizers

The addition of superplasticizers is an important approach to prepare high performance cement-based materials. The effect of polynaphthalene series superplasticizer (PNS) and polycarboxylate type superplasticizer (PC) on early-age cracking and volume stability of cement-based materials was investigated by means of multi-channel ellipse ring shrinkage cracking test, free shrinkage and strength test. The general effect of PNS and PC is to increase initial cracking time of mortars, and decrease cracking sensitivity of mortars. As for decreasing cracking sensitivity of mortars, PC > H-UNF (high-thickness-type PNS) > C-UNF (common-thickness-type PNS). To incorporate superplasticizers is apparently to increases free shrinkage of mortars when keeping the constant W/B ratio and the content of cement pastes. As for the effect of controlling volume stability of mortars, PC > C-UNF > H-UNF. Maximum crack width of mortars with PC is lower, but the development rate of maximum crack width of mortars with H-UNF is faster in comparison with control mortars. Flexural and compressive strength of mortars and concretes at 28 days increased with increasing superplasticizer dosages under drying conditions. C-UNF was approximate to H-UNF, but PC was superior to PNS in the aspect of increasing strength of cement-based materials.     

Comparison of fibrous insulations – Cellulose and stone wool in terms of moisture properties resulting from condensation and ice formation

Cellulose fibres are often used as thermal insulation in buildings. The organic nature of cellulose fibres, however, makes the insulation sensitive to high moisture content. This study investigates the moisture performance of cellulose insulation when exposed to a subzero environment. The paper is focused on the condensation and freezing in the material and includes comparison with the authors previous studies on stone-wool insulation. While the used stone-wool samples were water-repellent due to resin binders, cellulose is a typical representative for hydrophilic thermal insulation to which any contact with water condensate can be crucial.Test specimens of loose-fill cellulose were placed in a special laboratory device providing high moisture load. During a period of 100 h the specimens were subjected to a continuous load of moisture at atmospheric conditions on one side while the other side of the specimen faced a surrounding temperature of 0, −10 and −20 °C and the laboratory tests were repeated three times for each set of the specific thermal conditions (T_i = +20 °C, T_e = 0, −10 and −20 °C). The results indicate that there are minor changes in the water vapour permeability of the specimens. The experimental data from the investigation is compared with a mathematical model that simulates moisture diffusivity of cellulose together with accumulation due to sorption and freezing, using the actual climatic data.     

Key protection techniques adopted and analysis of influence on adjacent buildings due to the Bund Tunnel construction

The Bund Tunnel is 14.27 m in diameter. It is the first application of super diameter earth pressure balanced shield (EPBS) in China. There are many historical buildings along the construction line, and the minimum horizontal distance from the building to the tunnel side varies from 1.7 m to 30 m. Considering the importance of these historical buildings and the complicated construction processes, it is essential to adopt effective protection techniques to ensure safety during the tunnel construction. Three kinds of protection techniques are presented in this paper. Firstly, underground cut-off wall built by bored piles is used to separate the buildings and tunnel when the minimum horizontal distance from the building to the tunnel side is less than 5 m. Secondly, the grouting reinforcement technique is adopted when the minimum clear distance is between 5 m and 10 m. Finally, if the minimum clear distance is larger than 10 m, the optimized construction parameters are selected to reduce the influence induced by the EPBS excavation. The deformations of some typical buildings are monitored. The results of this project will be a useful reference for similar future projects.     

Treating wastewater from a pharmaceutical formulation facility by biological process and ozone

Wastewater from a pharmaceutical formulation facility (TevaKS, Israel) was treated with a biological activated-sludge system followed by ozonation. The goal was to reduce the concentrations of the drugs carbamazepine (CBZ) and venlafaxine (VLX) before discharging the wastewater to the municipal wastewater treatment plant (WWTP). Both drugs were detected at extremely high concentrations in TevaKS raw wastewater ([VLX] = 11.72 ± 2.2 mg/L, [CBZ] = 0.84 ± 0.19 mg/L), and resisted the biological treatment. Ozone efficiently degraded CBZ: at an O₃ dose-to-dissolved organic carbon ratio of 0.55 (O₃/DOC), the concentration of CBZ was reduced by >99%. A lower removal rate was observed for VLX, which was decreased by ～98% at the higher O₃/DOC ratio of 0.87. Decreasing the pH of the biologically treated effluent from 7 to 5 significantly increased the ozone degradation rate of CBZ, while decreasing the degradation rate of VLX. Ozone treatment did not alter the concentration of the effluent's DOC and filtered chemical oxygen demand (COD_f). However, a significant increase was recorded (following ozonation) in the effluent's biological oxygen demand (BOD₅) and the BOD₅/COD_f ratio. This implies an increase in the effluent's biodegradability, which is highly desirable if ozonation is followed by a domestic biological treatment. Different organic byproducts were formed following ozone reaction with the target pharmaceuticals and with the effluent organic matter; however, these byproducts are expected to be removed during biological treatment in the municipal WWTP.     

Evaluation of indoor environmental quality conditions in elementary schools׳ classrooms in the United Arab Emirates

This study presents findings of indoor environmental quality (IEQ) investigations conducted in elementary schools׳ classrooms in the United Arab Emirates (UAE). Average TVOC, CO₂, O₃, CO, and particle concentrations measured in the classrooms were 815 µg/m³, 1605 ppm, 0.05 ppm, 1.16 ppm, and 1730 µg/m³, respectively. Whereas, local authority known as Dubai Municipality recommended 300 µg/m³, 800 ppm, 0.06 ppm, 9 ppm, and 150–300 µg/m³ for TVOC, CO₂, O₃, CO, and particle, respectively. Dubai Municipality recommended temperature and relative humidity (RH) levels of 22.5 °C to 25.5 °C and 30%–60%, respectively. Average temperature and RH levels measured in the classrooms were 24.5 °C and 40.4%, respectively. Average sound level in the classrooms was 24 dB greater than recommended sound level limit of 35 dB. Six (6) classrooms had average lux levels in the range of 400–800 lux. Two (2) classrooms had average lux levels in the range of 100–200 lux. The remaining classrooms had lux levels around the recommended 300 lux. High occupancy density was observed in majority of the studied classrooms. Observations during walkthrough investigations could be used to explain measured IEQ data. Poor IEQ conditions in the studied classrooms highlight the need for further research investigation to understand how poor classrooms׳ IEQ condition could influence students׳ health, comfort, attendance rate, and academic performance.     

The effect of thiosemicarbazide on corrosion resistance of steel reinforcement in concrete

This study describes a laboratory investigation of the influence of thiosemicarbazide (TSC) on the corrosion of reinforcing steel and the compressive strength of concrete. The effect of TSC on the corrosion resistance of steel reinforced concrete was evaluated by carrying out electrochemical tests in NaCl and NaCl + TSC solutions for 60 days. Polarisation resistance (R_p) values of TSC added reinforced concrete were much higher than those without TSC. Similarly, AC impedance spectra revealed that the resistance of TSC mixed electrodes were also quite higher than those without. The compressive strength of concrete specimens containing TSC was measured and an increase of 20–25% was observed.     

Deterioration of dolostone by magnesium sulphate salt: An example of incompatible building materials at Bonaval Monastery,Spain

Since its abandonment 185 years ago, the XII century Santa Maria de Bonaval Monastery located in Guadalajara (Spain) has suffered significant deterioration: first the roof was lost, followed by partial collapse of the walls, moisture infiltration and extensive loss of stone surfaces due to salt weathering. This case study is a clear example of the incompatibility of some building materials: in this case, the combination of sulphate-bearing mortars and magnesium-rich stone and mortars leading to extensive weathering by magnesium sulphate crystallization. Samples of plaster, bedding and core mortars, stone fragments and flakes, salt crust and powders were collected, as well stone samples from the historic quarries located close to the Monastery. Characterization by XRD (X-ray diffraction), ESEM-EDS (environmental scanning electron microscopy with energy dispersive X-ray spectroscopy) shows that the most important stone-type used in the structure, dolostone, is mainly affected by magnesium sulphate salts (epsomite, MgSO₄ · 7H₂O), although other salts as kalicinite (KHCO₃) and mercallite (KHSO₄) were also detected. The connected porosity and pore size distribution determined by mercury intrusion porosimetry and capillarity behaviour suggest that the core mortar could easily be dissolved and the stone, plaster and bedding mortars are able to transport infiltrating solutions, giving rise to the precipitation of magnesium sulphate in the mortar joints and over the surface of the stone. Due to their chemical incompatibility, the combination of sulphate and magnesium-bearing mortars and stone with high magnesium content appears to be problematic and should be avoided in future restoration work.     

Study of the reactivity of cement/metakaolin binders at early age for specific use in steam cured precast concrete

The paper presents the results of a hydration study performed in order to explain the significant increase in compressive strength at one day of age observed on steam cured mortars when 25% by mass of cement was replaced with a metakaolin. Two CEM I 52.5R cements, differing in reactivity, and a metakaolin (MK) were used. By means of XRD and thermal analysis carried out on cement pastes, blended or not with MK, the main results showed that the improvement in strength at one day of age could be explained by the occurrence of a pozzolanic reaction due to MK, thermo-activated by the high curing temperature (55 °C). The pozzolanic reaction was observed through the consumption of calcium hydroxide and an increase in the amount of C–S–H and C–S–A–H hydrated phases. This change in the hydration product nature and amount was more pronounced when MK was combined with the less reactive cement, in agreement with the mechanical results on mortars. These results are of great importance for the concrete industry where the current trend is to decrease the clinker content in cements (1 ton of clinker = 1 ton of CO₂ released). In particular, the interesting mechanical performance at early ages can be helpful for precast concrete manufacturing.     

Impacts of impregnation chemicals on combustion properties of the laminated wood materials produced combination of beech and poplar veneers

The aim of this study was to investigate the effects of impregnation with boron compounds Borax (B_X), Boric acid (B_A), B_X + B_A, Imersol-Aqua (I_AQUA) and Timbercare-Aqua (T_AQUA) on combustion properties of the laminated wood materials produced combination of Oriental beech and poplar veneers bonded with Desmodur-VTKA (D_V) and Poly(vinyl acetate) (P_VAc) adhesives. The test samples, prepared from beech (Fagus orientalis Lipsky) and poplar (Populus nigra Lipsky) woods, were impregnated boron compounds by vacuum, I_AQUA by dipping and T_AQUA by brushing methods according to ASTM D 1413-76-99 and directions of the manufacturer. The laminated wood materials were prepared in the form of five layers, 4 mm thickness from the impregnated beech and poplar veneers according to TS EN 386. Combustion properties of samples after laminated and impregnated process were determined according to ASTM E 160-50. Considering the interaction of combustion type and impregnation materials, combustion temperature was found the highest in flame source combustion (F_SC) + T_AQUA (528.150 °C) but the lowest in without flame source combustion (WF_SC) + B_A (391.333 °C). Consequently, boron compounds and I_AQUA showed a decreasing impact on combustion properties of the laminated wood materials, produced combination of beech and poplar veneers, bonded with D_V. In consequence, impregnation with boron compounds and Imersol-Aqua of the laminated wood materials, bonded with Desmodur-VTKA, provides security for the usage of having high risk of fire.     

Effects of impregnation with Imersol-aqua on the modulus of elasticity in bending of laminated wood materials

The aim of this study was to investigate the impacts of impregnation with Imersol-aqua on the modulus of elasticity in bending (MOE) of some laminated wood materials. For this aim, oriental beech (Fagus orientalis Lipsky), oak (Quercus petrea Liebl.), Scotch pine (Pinus sylvestris Lipsky), oriental spruce (Picea orientalis Lipsky) and Uludağ fir (Abies bornmülleriana Lipsky) wood materials impregnated with Imersol-aqua according to ASTM D 1413-99 and producers’ definition. Laminated wood samples were produced from impregnated wood materials according to TS EN 386 in the five ply form (4 mm each) from oriental beech, oak, Scotch pine, Uludağ fir and oriental spruce wood by using Desmodur-VTKA adhesive. The MOE values were measured according to TS EN 408. Consequently, the MOE of impregnated + laminated (I + L_W) softwoods, pine, spruce and fir increased, respectively by 8.07%, 2.62% and 2.45% whereas the MOE of laminated + laminated hardwoods, beech and oak decreased, respectively by 5.06% and 4.37% with respect to laminated control samples (L_W). Considering the interaction of wood type and process, the MOE was obtained from laminated oriental beech, whereas the lowest was found for impregnated Uludağ fir. In consequence, in the massive construction and furniture elements that the MOE after the impregnation and lamination (I + L_W) is of great concern, oriental beech and Scotch pine materials could be recommended.     

Performance analysis of a solar-assisted ground-source heat pump system for greenhouse heating: an experimental study

This study investigates the performance characteristics of a solar-assisted ground-source (geothermal) heat pump system (SAGSHPS) for greenhouse heating with a 50 m vertical 32 mm nominal diameter U-bend ground heat-exchanger. This system was designed and installed in the Solar Energy Institute, Ege University, Izmir (568 degree days cooling, base: 22 °C, 1226 degree days heating, base: 18 °C), Turkey. Based upon the measurements made in the heating mode from the 20th of January till 31st of March 2004, the heat extraction rate from the soil is found to be, on average, 57.78 W/m of bore depth, while the required borehole length in metre per kW of capacity is obtained as 11.92. Design practices in Turkey normally call for U-bend depths between 11 and 13 m/kW of heating. The entering water temperature to the unit ranges from 8.2 to 16.2 °C, with an average value of 14 °C. The greenhouse air has a maximum day temperature of 31.05 °C and night temperature of 14.54 °C with a relative humidity of 40.35%. The heating coefficient of performance of the heat pump (COP_HP) is about 2.00 at the end of a cloudy day, while it is about 3.13 at the end of sunny day and fluctuates between these values in other times. The COP values for the whole system are also obtained to be 5–20% lower than COP_HP. The clearness index during experimental period is computed as average 0.56. At the same period, Cucumus sativus cv. pandora F₁ was raised, and product quality was improved with the climatic conditions in the designed SAGSHPS. However, experimental results show that monovalent central heating operation (independent of any other heating system) cannot meet the overall heat loss of the greenhouse if the ambient temperature is very low. The bivalent operation (combined with other heating system) can be suggested as the best solution in Mediterranean and Aegean regions of Turkey.     

Improved parameterization of dust emission (PM10) fluxes by the gradient method using the Naiman tower data at the Horqin desert in China

Dust emission/deposition flux has been estimated using the gradient method with the two-level (3 and 15 m high) measured PM₁₀ concentrations and the sonic anemometer measured momentum and kinematic heat fluxes at 8 m high from a 20-m monitoring tower located at Naiman (Horqin desert) in the Asian dust source region in China for the winter of November 2007 to March 2008. The time series of measured PM₁₀ concentration at 3 m high is used to identify the dust event and the non-dust event periods. It is found that the dust emission/deposition flux (F_C) shows a significant diurnal variation with the maximum emission flux of 5.8 kg km^? 2 h^? 1 at noon and the minimum of ? 1.6 kg km^? 2 h^? 1 in the afternoon for the non-dust event cases. Whereas for the dust event cases, the dust emission flux is found to occur when the prevailing winds are westerlies to northerlies with the maximum flux of 1275 kg km^? 2 d^? 1, while the maximum dust deposition flux of 148 kg km^? 2 d^? 1 occurs with the prevailing winds of southerlies to easterlies without any diurnal variation. The optimal regression equation between F_C and the friction velocity (u_*) for the dust emission cases is found to be F_C = 9.55 u_*^3.13 with the R² value of 0.73. However, this regression equation can be improved by taking into account the convective velocity (w_*). The resulting optimal regression equation is found to be F_C = 9.3(u_* ? 0.1w_*)^3.19 for the stable stratification (w_* < 0) with the R² value of 0.77 and F_C = 10.5(u_* + 0.34w_*)^4.11 for the unstable stratification (w_* > 0) with the R² value of 0.78, suggesting the importance of the convective velocity on the dust emission flux.     

Effects of curing regimes and cement fineness on the compressive strength of ordinary Portland cement mortars

Curing techniques and curing duration have crucial effects on the strength and other mechanical properties of mortars. Proper curing can protect against moisture loss from fresh mixes. The objective of this experimental work is to examine the compressive strength of ordinary Portland cement mortars (OMs) under various curing regimes and cement fineness. Six different curing methods including water, air, water heated, oven heated, air–water, and water–air were applied to the specimens and also six groups of mortars were used. The results showed that the highest and lowest compressive strengths are attributed to the specimens of OPC mortar water cured using grounded OPC for duration of 6 h (OM–G6–wc) and OPC mortar air cured under room temperature with oven heated after demoulding of the specimens at 60 °C for duration of 20 h (OM–OH–ac), respectively. The maximum levels obtained of compressive strengths at 7, 28, and 90 days are 57.5, 70.3, and 76.0 MPa, respectively.