Synchrotron Microtomography and Neutron Radiography Characterization of the Microstruture and Water Absorption of Concrete from Pompeii

There is renewed interest in using advanced techniques to characterize ancient Roman concrete. In the present work, samples were drilled from the "Hospitium" in Pompeii and were analyzed by synchrotron microtomography (uCT) and neutron radiography to study how the microstructure, including the presence of induced cracks, affects their water adsorption. The water distribution and absorptivity were quantified by neutron radiography. The 3D crack propagation, pore size distribution and orientation, tortuosity, and connectivity were analyzed from uCT results using advanced imaging methods. The concrete characterization also included classical methods (e.g., differential thermal-thermogravimetric, X-ray diffractometry, and scanning electron microscopy). Ductile fracture patterns were observed once cracks were introduced. When compared to Portland cement mortar/concrete, Pompeii samples had relatively high porosity, low connectivity, and similar coefficient of capillary penetration. In addition, the permeability was predicted from models based on percolation theory and the pore structure data to evaluate the fluid transport properties

Reactivity tests for supplementary cementitious materials: RILEM TC 267-TRM phase 1

A primary aim of RILEM TC 267-TRM: “Tests for Reactivity of Supplementary Cementitious Materials (SCMs)” is to compare and evaluate the performance of conventional and novel SCM reactivity test methods across a wide range of SCMs. To this purpose, a round robin campaign was organized to investigate 10 different tests for reactivity and 11 SCMs covering the main classes of materials in use, such as granulated blast furnace slag, fly ash, natural pozzolan and calcined clays. The methods were evaluated based on the correlation to the 28 days relative compressive strength of standard mortar bars containing 30% of SCM as cement replacement and the interlaboratory reproducibility of the test results. It was found that only a few test methods showed acceptable correlation to the 28 days relative strength over the whole range of SCMs. The methods that showed the best reproducibility and gave good correlations used the R3 model system of the SCM and Ca(OH)2, supplemented with alkali sulfate/carbonate. The use of this simplified model system isolates the reaction of the SCM and the reactivity can be easily quantified from the heat release or bound water content. Later age (90 days) strength results also correlated well with the results of the IS 1727 (Indian standard) reactivity test, an accelerated strength test using an SCM/Ca(OH)2-based model system. The current standardized tests did not show acceptable correlations across all SCMs, although they performed better when latently hydraulic materials (blast furnace slag) were excluded. However, the Frattini test, Chapelle and modified Chapelle test showed poor interlaboratory reproducibility, demonstrating experimental difficulties. The TC 267-TRM will pursue the development of test protocols based on the R3 model systems. Acceleration and improvement of the reproducibility of the IS 1727 test will be attempted as well

Effect of calcined clay reservoir sediments on the behaviour of sustainable calcium sulfoaluminate-blended cements

Total world cement manufacture is estimated at 4.65 billion tons in 2016 and the annual CO2 emissions from cement plants reach almost 2.8 billion metric tons, representing about 7% of the global anthropogenic emissions. The use of alternative cements and supplementary cementitious materials (SCMs) represents a powerful tool for both reducing the CO2 footprint related to cement industry and producing more durable environmentally friendly materials. Calcium sulfoaluminate (CSA) cements are special hydraulic binders obtained from non-Portland clinkers; they are very interesting under both technical and environmental point of view. Pulverized coal fly ashes and blast-furnace slag are the major sources of SCMs which also include natural pozzolans, silica fume, rice husk ash and metakaolin. The efficiency of SCMs depends on their chemical composition, fineness and amount of amorphous phases. In this paper, it is investigated the possibility of using clay reservoir sediments (CCRS), calcined at 750°C, as SCMs in blended CSA cements; these binders were subjected to physico-mechanical and hydration tests for curing times ranging from 4 hours to 56 days. X-ray fluorescence and diffraction, differential thermal–thermogravimetric analyses and scanning electron microscopy were employed as characterization techniques. It has been found that CCRS are very interesting since their utilization as SCMs allows a clinker dilution, thus implying both a decrease of CO2 emissions and a reduction of costs related to CSA cement production; moreover the hydration behaviour and the physical- mechanical properties of CSA blended cements were positively affected by the addition of CCRS

Fabrication and Properties of Blended Calcium Sulfoaluminate Cements Based on Thermally Treated Reservoir Sediments

In 2021, approximately 4.1 billion tonnes of cement were globally produced and the annual CO2 emissions from cement plants reached almost 2.8 billion metric tonnes. In recent years, many efforts have been made to manufacture low-CO2 cements. In this regard, great consideration has been given towards calcium sulfoaluminate (CSA) binders for both their technical features and sustainable properties, principally connected to their industrial process. The use of blended cements composed by CSA binders and supplementary cementitious materials (SCMS) can be an effective way to (a) reduce the CO2 footprint and (b) produce greener binders. This scientific work studied the utilization of different amounts (15–35 wt%) of calcined reservoir sediments (RS) as SCMS in blended CSA binders, where the binders were cured for up to 56 days and characterised by various analytical techniques. It was found that thermally treated RS were particularly noteworthy as their utilization allowed for a dilution of the CSA clinker, thus implying a decrease in CO2 emissions and a reduction in costs related to their production. However, compared to a plain CSA cement, the blended systems showed rather similar volume stability levels, whilst their compressive strength and porosity values were, respectively, lower and higher at all the investigated aging periods

The Influence of Chemical Activators on the Hydration Behavior and Technical Properties of Calcium Sulfoaluminate Cements Blended with Ground Granulated Blast Furnace Slags

The manufacture of Ordinary Portland cement (OPC) generates around 8% of the global CO2 emissions related to human activities. The last 20 years have seen considerable efforts in the research and development of methods to lower the carbon footprint associated with cement production. Specific focus has been on limiting the use of OPC and employing alternative binders, such as calcium sulfoaluminate (CSA) cements, namely special hydraulic binders obtained from non-Portland clinkers. CSA cements could be considered a valuable OPC alternative thanks to their distinctive composition and technical performance and the reduced environmental impact of their manufacturing process. To additionally reduce CO2 emissions, CSA cements can also be blended with supplementary cementitious materials. This paper investigates the influence of two separately added chemical activators (NaOH or Na2CO3) on the technical properties and hydration behavior of four CSA blended cements obtained by adding to a plain CSA cement two different ground granulated blast furnace slags. Differential thermal-thermogravimetric, X-ray diffraction and mercury intrusion porosimetry analyses were done, along with shrinkage/expansion and compressive strength measurements

Il riutilizzo di rifiuti solidi industriali nel processo di produzione dei comuni leganti idraulici

The utilization of industrial solid wastes in civil works and in industries of building materials has been examined, particularly with reference to the residues generated in the OCSE area suitable for the most relevant uses under the qualitative and quantitative point of view. A special emphasis has been put on the utilization of wastes in the national cement industry, taking into account the introduction of the Italian recent legislation and the European standards regulating the uses of common cements

Use of Potabilized Water Sludge in the Production of Low-Energy Blended Calcium Sulfoaluminate Cements

Ordinary Portland cement (OPC) manufacture determines about 8% of the global anthropogenic CO2 emissions. This has led to both the cement producers and the scientific community to develop new cementitious materials with a reduced carbon footprint. Calcium sulfoaluminate (CSA) cements are special hydraulic binders from non-Portland clinkers; they represent an important alternative to OPC due to their peculiar composition and significantly lower impact on the environment. CSA cements contain less limestone and require lower synthesis temperatures, which means a reduced kiln thermal energy demand and lower CO2 emissions. CSA cements can also be mixed with supplementary cementitious materials (SCMs) which further reduce the carbon footprint. This article was aimed at evaluating the possibility of using different amounts (20 and 35% by mass) of water potabilization sludges (WPSs) as SCM in CSA-blended cements. WPSs were treated thermally (TT) at 700° in order to obtain an industrial pozzolanic material. The hydration properties and the technical behavior of two different CSA-blended cements were investigated using differential thermal–thermogravimetric and X-ray diffraction analyses, mercury intrusion porosimetry, shrinkage/expansion and compressive strength measurements. The results showed that CSA binders containing 20% by mass of TTWPSs exhibited technological properties similar to those relating to plain CSA cement and were characterized by more pronounced ecofriendly features

Synthesis and characterisation of calcium sulfoaluminate cements produced by different chemical gypsums

Calcium sulfoaluminate (CSA) cements show some desirable environmentally friendly features which include the possibility of using several industrial by-products as raw materials in their manufacturing process. Four chemical gypsums (flue-gas desulfurisation gypsum, fluorogypsum, phosphogypsum and titanogypsum) have proved to be suitable as total substitutes for natural gypsum (NG) in the raw meal. Mixtures based on limestone, bauxite, NG or one of the CS-rich ¯ by-products were heated in a laboratory electric oven from 1150 to 1300°C. The reactivity of raw mixtures to form clinker products was evaluated using X-ray diffraction (XRD) analysis. The raw mixtures containing industrial gypsum displayed better reactivity towards C 4 A 3 S ¯ than the one made with NG. Moreover, conduction calorimetric measurements associated with XRD and differential thermal-thermogravimetric analyses showed that all CSA cements, obtained by adding commercial anhydrite to clinkers produced at the optimum synthesis temperatures, have similar hydration products but with different hydration kinetics

Enhancement of the environmentally friendly features of belite-calcium sulfoaluminate cements through the use of industrial by-products

In this work, the possibility of using titanogypsum (T) and water potabilization sludges (WPS) as a source of material in the production of belite calcium sulfoaluminate (BCSA) cements has been investigated. Four BCSA clinker-generating raw mixes were heated in a laboratory electric furnace in the temperatures range 1200°-1350°C: one included only natural materials (limestone, clay, bauxite and gypsum); the others contained T and/or WPS as total substitute for natural gypsum and clay, respectively. Quantitative X-ray diffraction analysis on the burning products showed high conversion of reactants toward the main BCSA hydraulically active clinker components (C2S and C4A3$), especially at 1300° or 1350°C. Moreover, isothermal calorimetric measurements associated with differential thermal-thermogravimetric analyses showed that all BCSA cements, obtained by adding commercial anhydrite to the clinkers produced at the optimum synthesis temperatures, generally displayed a similar hydration behaviou