The effect of phosphate on the constitution and hardening of portland cement

Abstract

The effect of phosphorus pentoxide on the burning of Portland‐cement clinker and the setting and hardening of the resultant cement has been investigated, using both synthetic mixtures and the raw materials which it is proposed to use for cement manufacture in Uganda. It is shown that the P2O5 forms a solid solution with the 2CaO,SiO2 of the cement clinker and reduces the content of 3CaO,SiO2. Consequently the early strength falls as the P2O5 increases until, when the P2O5 reaches 2·25% of the clinker, the cement fails to meet British Standard requirements. Formulae are given from which the percentage of compounds present in the clinker can be calculated, and the procedure for determining the proportion of clay in the raw mix is described.Test data on concrete are given; cement high in P2O5 is affected more markedly than normal cement by an increase in water: cement ratio.

Influence of P(V) on the characteristics of calcium silicates and the hydration of clinkers

“…The partial replacement of fossil fuel by using MBM as an alternative represents a source of an additional amount of P 2 O 5: This is due to the ability of clinker to incorporate various levels of ash and the phosphorus inorganic compounds present in these materials would combine mainly with the silicates (alite and belite) formed during clinkering. 6,7 It has been shown that a high level of phosphorus inhibits the formation of alite. Halicz and Nathan 8 obtained synthetic clinkers that were prepared from oil shale containing up to 5 wt% P 2 O 5 as a secondary component.…”

On the phase chemistry of Portland cement clinker

“…The use of waste-derived fuels (agricultural crops, animal meat, bone meal) results in increased phosphorus content in cement. It has been shown that phosphorus decomposes or inhibits the formation of alite while stabilising belite and generating free lime (Halicz et al, 1984;Nastac et al, 2007;Nurse, 1952;Stanek and Sulovsky, 2009 On the phase chemistry of Portland cement clinker Hö kfors, Boströ m, Viggh and Backman (Nastac et al, 2007). At concentrations of 0 .…”

“…With increasing amounts of phosphorus pentoxide in the raw material of clinker, phosphorus was shown to primarily enter the belite phase and to a lesser extent the alite phase (Gutt, 1963;Nastac et al, 2007;Stanek and Sulovsky, 2009). At concentrations above 1% phosphorus pentoxide, a solid solution of phosphorus and belite forms (Nurse, 1952). By examining anhydrous cement (Poulsen et al, 2010) with low concentrations of phosphorus, the element was incorporated in alite and belite phases.…”

“…The use of wastederived fuels from agricultural crops, animal meat or bone meal, for example, leads to increased phosphorus content in cement. It has been shown that phosphorus decomposes or inhibits the formation of alite while stabilising belite and generating free lime (Halicz et al, 1984;Nastac et al, 2007;Nurse, 1952;Stanek and Sulovsky, 2009). The amount of alite in cement is of great importance because it is the most important contributor to the development of strength in concrete in the first 28 d. Because phosphorus is expected to increase when traditional fossil fuels are replaced with alternative biomass-based fuels, both theoretical and practical studies on how an increased phosphorous content influences clinker minerals have been performed.…”

Meat and Bone Meal as a Renewable Energy Source in Cement Kilns: Investigation of Optimum Feeding Rate

“…Therefore, there must be other phenomena as well, along with above mentioned reason, which cause the 138% increase in free lime content at 7 t/hr MBM feeding. It has been shown [7], [23]- [27] that a high level of phosphorous stabilizes belite and hence inhibits the reaction between CaO and belite to form alite. Due to this reason the free lime content can be increased.…”