脱硫石膏/粉煤灰抹面材料的制备与研究

以脱硫石膏和粉煤灰作为基料,添加适宜的缓凝剂、保水剂及其他助剂,制备出脱硫石膏/粉煤灰抹面材料。通过研究不同粉煤灰掺量、缓凝剂和保水剂对脱硫石膏/粉煤灰抹面材料性能的影响,确定出脱硫石膏/粉煤灰抹面材料的配比组成,基料中脱硫石膏:粉煤灰=4:1,复合缓凝剂A和保水剂甲基纤维素的掺量分别为0.2%和0.2%。     

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.     

Deposition of particles on gypsum-rich coatings of historic buildings in urban and rural environments

Deposition of gaseous and particulate atmospheric pollutants causes decay of historic mortars to give gypsum-rich coatings by sulphation of lime mortars and blackening of gypsum mortar, resulting in gypsum coatings. Particulate pollution emitted by industrial sources and vehicular traffic is responsible for the deterioration. XRF and SEM analyses of these coatings and their comparison with both the composition of dust coatings formed by the deposition of gaseous and particulate matter in an urban and a rural locality allows assessing which pollution sources are the most damaging for these materials, knowing the elemental composition of these emissions.     

The use of brick–lime plasters and their relevance to climatic conditions of historic bath buildings

Brick–lime mortars and plasters have been widely used as water-proof materials in aqueducts, bridges and cisterns since early Hellenistic time. In this study, the characteristics of brick–lime plasters used in some Ottoman bath buildings were investigated in order to understand their relevance as plasters in hot and humid environmental conditions of the baths. For this purpose, basic physical properties, raw material compositions, mineralogical, microstructural and hydraulic properties of brick–lime plasters of some historic bath buildings in ?zmir (Turkey) were determined by XRD, SEM-EDX, AFM and chemical analyses. The results indicated that their survival without loosing their strength and adhesion in hot and humid conditions of the baths was explained by their hydraulic characters due to the consciously use of porous and pozzolanic crushed bricks as aggregate in the manufacturing of plasters.     

Waste gypsum from intermediate dye industries for production of building materials

Paper presents the studies on characterization, beneficiation and utilization of H-acid gypsum, a waste material produced by the neutralization of free sulphuric acid collected during the formation of intermediate dyes. The waste gypsum contains impurity of organic matter like nitro compounds, naphthalene etc. The removal of impurities and improvement in colour was carried out by scrubbing with water, centrifuging and drying. The beneficiated H-acid gypsum was calcined to form β-hemihydrate plaster. The plaster was tested and evaluated for engineering properties such as compressive strength, bulk density, water absorption and porosity. These properties suggest the use of beneficiated H-acid gypsum for making building and ceramic grade plasters and for casting building blocks, board and cementitious binder. Data showed that cementitious binder of low water absorption (9.5%) and adequate compressive strength (19.6 MPa at 28 days) can be produced for use as construction material. The use of waste gypsum will definitely benefit environment and sustainable development.     

Mineralogical study of salt crusts formed on historic building stones

A historic building stone, Baumberger sandstone, was exposed to gaseous SO(2) under dry and wet surface conditions in an atmospheric test chamber. The extent of salt formation resulting from the exposure to pollutant gases as well as the variations in mineralogical composition were studied based on petrological thin sections. Results reveal that the salts are formed only over the surface of the sample. The thickness of the formed salt crusts is determined. Calcite dissolution as well as porosity decreases are due to gypsum formation.     

Mortars,pigments and saline efflorescence from Canarian pre-Hispanic constructions (Galdar,Grand Canary Island)

Construction elements of the ancient caves of Galdar (Grand Canary Island) give details of the life of isolated, prehistoric island inhabitants (pre-Hispanic Canarians) and their adaptation to a dry volcanic environment. Mineralogical study samples of host rocks, mortars, pigments and saline efflorescence by X-ray diffraction and electron microscopy allow us to explain their local origin, development grade and environmental factors of degradation. Regional tephra pyroclasts are composed of volcanic glass and euhedral phenocrysts of pyroxene and olivine, with traces of biotite and apatite. Cream mortars are calcite, apatite and feldspars; white are calcite-halloysite; grey calcite with iron oxides and the argillaceous plasters are mixtures of illite, montmorillonite, kaolinite and chlorites. Red-ochre pigments are oxo-hydroxides of iron-manganese, whites are halloysite, and blacks are silica mixtures of Mg, Fe, Mn, Ti, K and Ca, collected from the host-tephra (pyroxene, biotite, spinel, pyrolusite and iron oxides). The main saline efflorescences consist of thenardite and trona (sodium salts) from the watering of modern crops fields and gypsum from the restoration works (concrete) of the archaeological park in 1997. The ancient population used numerous combinations of local minerals to prepare beautiful paintings, which were protected underground below pyroclastic deposits until modern times, when they were dug out and flooded with saline waters, which produced serious alterations. Additional care must be taken to protect these prehistoric constructions.     

Study on anhydrite plaster from waste phosphogypsum for use in polymerised flooring composition

The paper deals with an investigation about the production of high strength plaster from the waste phosphogypsum and its use in making flooring tiles. To achieve this objective, phosphogypsum was calcined at 900–1000 °C to anhydrite which was mixed with suitable chemical activators (alkali/alkaline earth hydroxides, sulphates, carbonates) and finely ground (>400 m²/kg Blaine's) to achieve high compressive strength (36–37 MPa). The anhydrite plaster was blended with 2–3% of predetermined quantity of a monomer methyl methacrylate (MMA) with a compatible catalyst, metalic oxide pigments, fly ash or red mud, chopped glass fibres (E-type, 12 mm long) and quartz sand to form flooring tiles by vibration moulding technique followed by high humidity curing, drying, grinding and polishing. The addition of chemical activators increase the rate of dissolution of anhydrite for rapid transformation into hard strong gypsum matrix while the MMA gets polymerised during hydration of anhydrite into polymethyl methacrylate which fills up voids and pores of hydrating anhydrite and thus improves density, strength and durability of the anhydrite plaster against water. The durability of anhydrite plaster by alternate wetting and drying and heating and cooling cycles is reported along with hydration mechanism. The use of phosphogypsum anhydrite for making high strength plaster and flooring tiles is recommended.     

Plasters and renders for salt laden substrates

The EU project COMPASS, Compatibility of Plasters and renders with Salt loaded Substrates in historic buildings, aimed at improving the maintenance of monuments by means of a better understanding of the working principles of the plasters and the damage mechanisms induced by salt crystallisation. Salt damage was effectively studied modelling the moisture and salt transport and degradation (irreversible dilation) and a fast and efficacious salt crystallisation test developed. Practical results were the assessment of the requirements for plasters to be used on salt loaded substrates and guidelines for selecting plasters suitable for different situations. The dissemination of the results was also entrusted to the expert system MDDS.     

Atmospheric contamination of archaeological monuments in the Agra region (India)

An analysis of water-soluble samples collected from marble and sandstone of monuments for different ions have been done. The combustion, manufacturing and other polluting operations existing within Agra area have been investigated. The measurements of flue gases amounting to 3.63 × 10⁹ S.C.F. indicate atmospheric contamination and deterioration of archaeological monuments of Agra. It has been found that the principal sources of air contamination are the 325 iron foundries and 3 railway shunting yards located within 0.3 to 3.0 Km. of the main monuments. The topographical and micrometeorological conditions of the city have tended to favour and aggravate the concentration of effluents in the surrounding air of the monuments. The annual average existing level of SO₂ ranges from 16 to 20 micrograms/m³. The seasonal distribution of SO₂ and suspended particulate matter in the air at Taj Mahal, Red Fort and Sikandra have been discussed and illustrated. It has been observed that there is substantial sulphur dioxide contamination existing at Agra. The maximum concentration of SO₄^2? and NO₃^? amounting 0.46 and 0.38 respectively by weight percentage found existing at Red Fort cause efflorescences of sandstone.     

The effect of coal and diesel particulates on the weathering loss of Portland Limestone in an urban environment

Due to reductions in domestic usage, legislation and changes in fuel use, coal derived particulates in the UK urban atmosphere have been significantly reduced. However, a large increase in road usage and an expansion in the use of diesel engines, has meant that the majority of particulates, now present in the urban atmosphere, originate from vehicle exhausts. Particulate matter, resulting from coal combustion, has been recorded as being present in black patinas observed on some historic stone buildings and monuments and has been associated with accelerated weathering of stone surfaces as a result of enhanced gypsum formation. In contrast, the effects of particulates resulting from vehicle exhaust on stone are much less understood. To investigate this, a comparative study was undertaken using the technique of microcatchments under ambient atmospheric conditions. This compared the elemental composition and volume of precipitation runoff from Portland Limestone coated with three different particulate treatments. Treatments consisted of coal and diesel particulates, both separately and in combination. Combining these treatments attempts to investigate any synergistic effects that may occur when coal derived particulates are overlain by layers formed by particulates from more contemporary sources. It was found that diesel-coated samples were much darker in appearance and showed a significant reduction (P<0.05) in the overall rate of weathering loss when compared to untreated samples. Microcatchment runoff volume was reduced from diesel-coated Portland Limestone compared to untreated stone. Enhanced surface temperatures may be increasing the rate of moisture loss from the pore network between rainfall events. Since, generally, the pores must be full before runoff can occur, the reduction may be due to the differential volume of empty pore space between diesel-coated and untreated Portland Limestone.     

Evidence of pre-industrial air pollution from the Heads of the Kings of Juda statues from Notre Dame Cathedral in Paris.

Pollution originating from wood combustion characterised the urban atmospheres of the past and led to the formation of thin grey crusts on the surface of the stone of monuments. The grey crusts discovered on the Heads of the Kings of Juda statues, which adorned the facade of Notre Dame in Paris from the 13th century until 1792, constitute a material record of the effects of this ancient air pollution. The height at which the statues stood suggests that the effect was not the result of a point phenomenon, but was caused by a generalised pollution of the Paris atmosphere at the time.     

Detection of deteriorations in cultural structures created by carving into low-strength rocks by the non-destructive test (NDT) method

In the cultural stone heritage, progressive deteriorations develop over time with the effect of atmospheric processes. These deteriorations can reach to a significant degree that threaten the integrity of the monuments built from weak-strength rocks. In this study, it is aimed to determine the deteriorations caused by atmospheric processes on the monument surface in cultural heritage works built by carving into low-strength pyroclastic rocks by non-destructive tests (NDTs). To this end, two historic structures in the Kilistra Ancient City of Konya (Turkey) were selected. The index, strength, mineralogical and petrographic properties of the rocks, in which the monuments were carved, were first investigated. Then, contour scaling, crack, efflorescence and biodeterioration types were determined on the facades of the monuments. Later, NDT deterioration change maps were prepared based on the data obtained by performing the relative humidity, Schmidt hammer rebound (SHR), and P-wave velocity (Vp) measurements on the facades of the monuments. In the deterioration maps, it was determined that the SHR and Vp values of the rock were low in the capillary, infiltration, and crack zones with water penetration in the monuments built on low-strength pyroclastic rocks. However, deterioration was less in the regions with more limited water access according to zones.     

Effect of pozzolanic admixtures on mechanical,thermal and hygric properties of lime plasters

Compressive and bending strength, thermal conductivity, specific heat capacity, water sorptivity, moisture diffusivity, water vapor diffusion coefficient, sorption isotherms, and linear thermal and hygric expansion coefficients of three lime plasters with pozzolanic admixtures are determined in the paper. Comparative measurements with common lime plaster are done as well. On the basis of the experiments performed, it can be concluded that all the three analyzed lime-pozzolana plasters are suitable for an application in reconstruction of historical buildings. While their mechanical properties are significantly better compared to the reference lime plaster, their thermal and hygric properties are mostly similar or slightly improved. The only parameter that is found to be worse than for the common lime plaster is the linear hygric expansion coefficient but its worsening can be matched by the improved mechanical properties.     

Physico-chemical adhesion and cohesion bonds in joint mortars imparting durability to the historic structures

It is well known that even though historic mortars present low strength and elastic moduli they confer durability to the structures surviving today. The present work investigates the durability of historic mortars in relation to the production technologies employed. Thermal analysis allows for classification of historic mortars in both lime and hydraulic types. Mineralogical data, concerning fabrication and texture, along with thermal analysis provide criteria on specific classification, for: typical lime, crushed brick–lime, cementitious, rubble masonry, hot lime technology and gypsum mortars. The correlation of the measured tensile strength (fmt,k) with the estimated CO₂/structurally bound water ratio, indicates direct proportionality to the levels of the hydraulicity. Physico-chemical adhesion and cohesion bonds, studied by SEM-TEM/EDX, developed at the matrix and at the binder/aggregate interface, respectively, becomes the key factor in interpreting the considerable durability that the historic mortars confer to the structures as bearing elements.     

Carbon air pollution reflected in deposits on chosen building materials of Prague Castle

Thin black surface layers or black coloured gypsum crusts can be observed on stones of many buildings and sculptures around the world. The black weathered stone and mortar surface from selected sections of the Prague Castle were studied by microscopic methods, GC/MS and pyrolysis-GC/MS analysis. Microscopically, we found an authigenic gypsum formation with an outer layer of an admixture of fine grains of quartz, clay minerals, thermally altered clay minerals, fly ash, and carbonaceous particles of natural and anthropogenic origin particularly chars, cokes, soots. Noncarbonate C content ranged between 0.8% and 4.3%. Phtalates dominated in extracts from the samples and benzonitrile had the greatest abundance in the pyrolysis products. The identified organic particles and compounds are known to result from human activities.     

Influence of paints on drying and salt distribution processes in porous building materials

Paints are widely used as finishing coats on all kinds of buildings. Aiming at a better understanding of how paints influence salt decay processes, experiments were performed on painted and unpainted specimens: (a) crystallization tests on specimens composed of a plaster on brick substrate; (b) drying experiments on stone specimens, monitored by means of a two-dimensional magnetic resonance imaging technique. The results of these experiments suggest that: (i) paints tend to increase the presence of moisture and salt deposition on or close to the surface of walls; (ii) the salt-accumulation behaviour and related features of different plasters/renders may be differently affected by paint layers.     

The humidity buffer capacity of clay–sand plaster filled with phytomass from treatment wetlands

The aim of our study was to measure the amount of moisture absorption and desorption in clay–sand plaster mixed with “fibre-wool” from Typha spadixes and chips of Typha and Phragmites. Common cattail (Typha latifolia) and common reed (Phragmites australis) are the most common plants in constructed and semi-natural wetlands for wastewater treatment, as they are highly valued in ecologically oriented construction. The cattail and reed for the experiment were harvested in a wastewater treatment subsurface flow semi-natural wetland and in two free water surface constructed wetlands which showed reliable aboveground phytomass production over a 5 years period (for Typha, 0.37–1.76 kg DW m⁻² in autumn and 0.33–1.38 kg DW m⁻², and for Phragmites, 0.61–1.32 and 0.61–1.02 kg DW m⁻², respectively). The quantity of moisture absorption and desorption was measured in a climatic chamber where the humidity of ambient air was suddenly raised from 50% to 80% (absorption) and reduced from 80% to 50% (desorption). Over 12 h, all of the samples released the same amount of water as they absorbed. The clay–sand plaster samples absorbed slower than they desorbed, whereas the gypsum wallboard required significantly more time for desorption. Added phytomass gave positive effects by reducing the weight of the clay–sand plaster, accelerating and increasing moisture absorption.     

Soil properties, foundation stability, groundwater conditions, characteristics of building stones and mortar used in construction and proposed measures for restoration at the site of ancient Ayla in a Qaba, Jordan

Ancient Ayla in Aqaba, Jordan was destroyed during a major earthquake incident that occurred in Aqaba in 1067 AD. The Gulf of Aqaba is a seismically active region. The latest strong earthquake incident occurred on November 22, 1995 when an earthquake of local magnitude 6.2 rocked the Gulf of Aqaba region. The main shock was followed by thousands of aftershocks. The Gulf of Aqaba-convering the geologic coordinates 28.0–29.6 N; 34.5–35..2 E is one of two natural bays surrounding the Sinai Peninsula which itself is located at the northernmost end of the Red Sea. The soil profile underlying Aqaba city consists of interlayering of various sedimentory Holocene Alluvium deposits. This study is aimed at investigating the soil and foundation condition at the site of the ancient Ayla. This includes groundwater conditions, bearing capacity of the strata supporting the walls of ancient Ayla, and structural stability of these walls. The study included an investigation of the characteristics of building stones used in the earlier construction as well as those proposed for use in the restoration of Ancient Ayla. Furthermore, the physical and chemical properties of existing mortars were evaluated. Gradation analyses were conducted to select a proper sand for use in the mortar mix. Mortar mix tests were conducted for the purpose of recommending a mortar mix for use in restoration works. Trends in the results of various mix tests were analyzed. Sample borings were made at the site to obtain soi profile and extract soil and water samples. Standard Penetration test was conducted at different depths. Laboratory tests were performed on these samples to determine pertinent physical properties of the soil and salinity of the water. Soils at the site were found to be predominantly granular with archaeological fill overlying beach sand which in turn overlies the coarser sand and gravel of the natural deposits. Except for the wadi area, groundwater was encountered at about 3 m below existing ground levels. Bearing capacity of the foundation was evaluated to be 3.5 kg/cm² for the dense granular materials (that represent the probable founding layer of the existing walls), and 2.0 kg/cm² for the weaker silty/clayed zone. Back analysis yields a safe wall height of at least 6.0 m. Therefore, no stability problems are present. Tilting and sinking were noted in some portions of the exterior walls as a result of dynamic lateral earth pressures exerted during the major earthquake incident of 1067 AD. Measures for wall foundation support during archaelogical excavations are suggested. Permanent excavations for exposing the walls should be limited to a free height of about 3 m at the location of western wall, and about 2.5 m at the location of the eastern wall. Stones used in the construction of ancient Ayla were found to consist of precut sandstone, siltstone, mudstone and granite. Weathering effects were clearly noted on the exposed stones in the walls. It is proposed to use a replacement stone consisting of sandstone group located at a source 35 km North of Aqaba. Measures suggested for the restoration of the walls addressed the lack of mortar in the inner walls and the replacement of disintegrated stone pieces in the external walls. Existing mortars were found to consist primarily of three types, namely a brown silty mixture, a gray mixture, but predominantly a mixture of fine gravel and a lime/gypsum binder. The major chemical constituents of the original mortar are 18 % SiO₂, 23 % CaO, and 34 % SO₃. X-ray diffraction peaks indicate the presence of gypsum, calcite and quartz. Comparative analysis data gave 7 % CaCO₃, 53 % Sand, and 40 % Solubles as average values of the constituents. Following the selection of two sand sources for use in the mortar mix, recommended mortar for restoration was a mix of lime, sand, ash, with ratios of 1:3:1.5.