Identification of crystals forming on porcine articular cartilage: a new method for the estimation of the postmortem interval

Articular cartilage was examined to determine its decomposition sequence and its potential for assessing the postmortem interval. Scanning electron microscopy of articular cartilage from buried porcine trotters showed the presence of microcrystals on the synovial surface. These orthorhombic pyramidal or “coffin”-shaped crystals, appeared at 3 weeks (22 days) after interment and disappeared after 6 weeks. The disappearance of these crystals was linked to decompositional changes to the integrity of the synovial joint. The formation and disappearance of these crystals was associated with a pH change at the cartilage surface. Scanning electron microscopy–energy-dispersive X-ray (SEM-EDX) analysis showed that the five main elements contained within these crystals were carbon, nitrogen, oxygen, magnesium, and phosphorous. Such elemental analysis suggested the crystals may be struvite (MgNH4PO46(H2O)). Bacteria cultured from the cartilage synovial surface produced struvite crystals when grown in suitable media and were identified by DNA analysis to be Comamonas sp

Value added utilization of by-product electric furnace ferronickel slag as construction materials: A review

This paper reviews the potential use of electric furnace ferronickel slag (FNS) as a fine aggregate and binder in Portland cement and geopolymer concretes. It has been reported that the use of FNS as a fine aggregate can improve the strength and durability properties of concrete. Use of some FNS aggregates containing reactive silica may potentially cause alkali-silica reaction (ASR) in Portland cement concrete. However, the inclusion of supplementary cementitious materials (SCM) such as fly ash and blast furnace slag as partial cement replacement can effectively mitigate the ASR expansion. When finely ground FNS is used with cement, it shows pozzolanic reaction, which is similar to that of other common SCMs such as fly ash. Furthermore, 20% FNS powder blended geopolymer showed greater strength and durability properties as compared to 100% fly ash based geopolymers. The utilization of raw FNS in pavement construction is reported as a useful alternative to natural aggregate. Therefore, the use of by-product FNS in the construction industry will be a valuable step to help conservation of natural resources and add sustainability to infrastructures development. This paper presents a comprehensive review of the available results on the effects of FNS in concrete as aggregate and binder, and provides some recommendations for future research in this field

A Critical review of ultra-accelerated tests for alkali- silica reactivity

Peer reviewed: YesNRC publication: Ye

Evaluation of miniature rock prism test for determining the potential alkali-expansivity of aggregates

Expansion of miniature rock prisms sawn normal to the layering of the rock and stored in 2N NaOH was monitored with a Huggenberger gauge or a linear voltage differential transformer (LVDT). Owing to their thinness (3 mm) the samples become saturated quickly and expansion usually commences within the first week, compared with the long initiation period typical of the rock cylinder method ASTM C586. The miniature rock prism test was evaluated for alkali-carbonate, slowly expanding siliceous aggregates and classical alkali-silica reactive rocks. Rates of expansion generally correlated well with those of corresponding concrete prisms tested according to CSA A23.2 - 14A.L'expansion de prismes de roches miniatures pr\ue9lev\ue9s \ue0 angle droit des couches dans des sp\ue9cimens de roche et d\ue9pos\ue9s dans une concentration 2N de NaOH a \ue9t\ue9 observ\ue9e avec une jauge Huggenberger ou avec un capteur de d\ue9placement. En raison de leur minceur (3 mm), les \ue9chantillons ont \ue9t\ue9 satur\ue9s rapidement. L'expansion de l'alcali commence habituellement au cours de la premi\ue8re semaine, contrairement \ue0 la m\ue9thode d'essai ASTM C586 o\uf9 il faut attendre souvent une longue p\ue9riode d'initiation. La capacit\ue9 de d\ue9terminer l'expansion caus\ue9e par l'alkali-carbonate, les granulats siliceux \ue0 expansion lente et la r\ue9action classique alcali-silice de l'essai sur une prisme de roche miniature a \ue9t\ue9 \ue9valu\ue9e. Les taux d'expansion des prismes de roches miniatures plac\ue9s dans une solution de NaOH entre habituellement bien en corr\ue9lation avec les taux correspondants d'expansion des prismes de b\ue9ton NNC A23.2 - 14A.Peer reviewed: YesNRC publication: Ye

Microstructural investigation of deteriorated Portland cement concretes

Peer reviewed: YesNRC publication: Ye

Re-evaluation of standard mortar bar and concrete prism tests for alkali-aggregate reactivity

The effectiveness of the mortar bar ASTM C227 and concrete prism CSA A23.2-14A tests for evaluating the potential alkali-aggregate reactivity of classical alkali-silica, late expansive siliceous and alkali-carbonate aggregates is discussed. It is emphasized that petrographic examination is an essential preliminary step in the evaluation of potential alkali reactivity of all aggregates. The expansion limits set to differentiate between deleteriously expansive and innocuous cement-aggregate combinations by ASTM, CSA, U.S. Corps of Engineers, U.S. Bureau of Reclamation and by the author are evaluated for use with classical alkali-silica, late-expanding siliceous and alkali- carbonate reactive aggregates.On examine l'efficacit\ue9 de l'essai ASTM C227 sur des \ue9prouvettes cylindriques de mortier et de l'essai ACNOR A23.2- 14A sur des \ue9prouvettes prismatiques de b\ue9ton en vue de d\ue9terminer la r\ue9activit\ue9 aux alcalis de granulats classiques alcali-silice, de granulats siliceux \ue0 expansion tardive et de granulats alcali-carbonate. On souligne l'importance d'effectuer un examen p\ue9trographique avant d'entreprendre l'\ue9valuation de la r\ue9activit\ue9 aux alcalis de tous les types de granulats. On examine les limites d'expansion \ue9tablies par l'ASTM, l'ACNOR, le U.S. Corps of Engineers et le U.S. Bureau of Reclamation ainsi que l'auteur, pour diff\ue9rencier les combinaisons b\ue9ton-granulats dangereusement expansibles et celles qui ne pr\ue9sentent aucun danger, en vue de d\ue9terminer dans quelle mesure elles peuvent s'appliquer aux granulats classiques alcali-silice, aux granulats siliceux \ue0 expansion tardive et aux granulats alcali-carbonate r\ue9actifs.Peer reviewed: YesNRC publication: Ye