operation oaxaca: only one can remain.

portland cement selection. (034)

Carlos Manuel Jarquín Sánchez
7 min readApr 2, 2024

this is carlos.

proved myself wrong.

and yes, i’ll do a research investigation on filtering metal ions and monetizing them.

…so that all the doubters realize why economics says no.

maybe, the only exception is rare earth elements (REE).

it would be useful to have domestic supply of those instead of relying on china.

REEs is what is in ur phones, laptops, EVs, renewable energies, batteries, everything.

so, kinda a big deal.

but for now, imma proceed with the cement route.

thx to tyler cowen for that initial questioning that led me to this point.

scaling up will be the challenge, along with the technical barriers within the market i choose.

and the first one i need to decide is the market.

and within that market, there exist other options.

let’s go.


who will triumph?

acid mine drainage (AMD) sludge will be dried and ground up to make this raw material suitable for cement.

but which type?

well… what we are attempting to do is a substitution of raw material, or an alternative.

so what cement allow/permit OR already do raw material alternatives for their cement production?

remember, there are rules/regulations by each state on materials, so other constraints exist.

the only ones that allow this are ones where the raw iron material/feedstock is so high and economical that it makes sense for cement plants to utilize it.


to save money.

and these can include:

  • sulfoaluminate cement: ferrite-rich waste materials.
  • calcium aluminosulfate cement: bauxite ore residue or fly ash.
  • blended cement: mix with ferric iron-rich alternatives.

ferrite → iron(Fe³⁺) oxide mixed with other elements like magnesium, zinc, manganese, calcium, etc… and these materials were fired together.

firing → supply of heat to a kiln by burning fuel. the fuel can be either oil, natural gas, or propane.

bauxite ore → aluminum + gallium.

fly ash → a byproduct from burning pulverized coal in electric power generating plants or coal plants.

standard cement kiln.

and those types of cements (where raw alternatives work) are these three:

  • ordinary portland cement (OPC)
  • portland slag cement (PSC)
  • portland pozzolana cement (PPC)

and this is what they all do:


OPC is manufactured by heating limestone minerals with a mixture of clay & sufficient reactivity.

clinker nodule is formed as an intermediate product due to partial fusion of material at high temperatures.

nodule → sizes of 5–25 millimeters.

the clinker is mixed with <5% gypsum & finely grounded to make OPC.

OPC is used in freeway walls, high-rise buildings, bridges, roads, industrial chimneys, and more.

the average composition of the material is made out of silicates of alumina (clay) & calcium carbonate (limestone or chalk) components.


PSC is made by substituting a percentage of OPC with finely ground granulated blast furnace slag (GGBFS) and adding a calcium sulfate activator.

calcium sulfate is a component of gypsum, the cement-hardening material.

but why do people do this?

it prevents the leaching of lime as an efflorescence in water seepage-affected areas by forming stable compounds.

it is resistant to acidic as well as alkaline environments.

typical industry standards require PSC to have:

  • 45% — 50% GGBFS.
  • 45% — 50% clinker.
  • 03% — 05% gypsum.

the clinker is the cement material.

GGBFS is typically obtained at a steel manufacturing plant, as its components have >20% ferric iron content.

PSC is used in the construction of bridges & sea ports where saline water comes into constant contact with the pillars of the bridge.

and PSC is used where the washings of acids, salts, sulfur, etc. flow… so also municipal sewage tubing and marine infrastructure.

from previous research, C3A binds chloride, acids, etc.

so ferric iron in calcium aluminoferrite, for GGBFS, is necessary for PSC to do the following:

  • lower the production temperature of cement clinker & improve the burnability & reaction through melt/flux formation.
  • to meet valorization and landfill diversion targets to use iron-bearing by-products.
  • to limit the tricalcium aluminate content (C3A)… so we can increase the sulfate resistance of the cement.

the four main materials in clinker are:

  • C3S, tricalcium silicate
  • C2S, dicalcium silicate
  • C3A, tricalcium aluminate
  • C4AF, tetracalcium aluminoferrite


it’s OPC with another ingredient.

the addition is fly ash & gypsum.

fly ash → a byproduct from burning pulverized coal in electric power generating plants or coal plants.

and this is what the word “pozzolana” means:

pozzolan → a siliceous or aluminosiliceous material [aka, OPC] that chemically reacts with the calcium hydroxide released by the hydration of portland cement.

this creates calcium silicate hydrate & other compounds possessing cementitious properties.

the condition is that the material must be finely divided form & in presence of moisture.

volcanic ashes & pumices are naturally occurring pozzolanic materials.

man-made ones include fly ash, silica fume, and rice husk.

if we use man-made materials in cement production, they will be called “raw alternative materials”.

PPC can be used anywhere that OPC is used.

it can be used also in dams, dykes, hydraulic structures, marine structures, seashore construction (in case of tsunami), etc.

and because of PPC utilizing fly ash, high aluminum & iron oxides … and it’s also waste.

so it’s cheaper to procure, if the source is near to the cement plant. but because PPC has iron… and iron can limit the tricalcium aluminate content (C3A)… we can increase the sulfate resistance of the cement…

PPC usually sells at a premium to OPC in the market.


it can resist moisture or chemicals like sulfate or chloride.

and OPC cannot.


out of all these options,

it is obvious.

portland slag cement (PSC) it is.

but there are some criteria to cover.

also from the american society for testing & materials:

we have ASTM C595: standard specification for blended hydraulic cement.

from its documents:

requirements blended hydraulic cements for both general & special applications.

it could be done using slag or pozzolan or both…

with portland cement or portland cement clinker or slag with lime.

cements are classified into two types:

#1) type IS which is portland blast-furnace slag cement.

#2) type IP which is portland-pozzolan cement.

the values are either SI units or inch-pound units.

the other ASTM requirement is:

ASTM C989: standard specification for slag cement for use in concrete and mortars.

from its documents:

this specification covers slag cement as a cementitious material in concrete and mortar.

it covers the three strength grades of finely ground granulated blast-furnace slag (grades 80, 100, and 120) for use as a cementitious material in concrete and mortars.

the slag shall contain no additions & conform to the sulfide, sulfur, & sulfate chemical composition requirement.

the values are either SI units or inch-pound units.

these slag grades are determined by the following slag activity index:

slag activity index:

SAI % = (SP / P) x 100

SAI = slag-activity index, in a percentage.

SP = average compressive strength of slag-reference cement mortar cubes at designated ages, MPa (psi)

P = average compressive strength of reference cement mortar cubes at designated ages, MPa (psi).

the cost of each cement comes down to factors, and not necessarily at an exact price:

OPC might be costlier than PPC due to the higher energy consumption & production cost associated with clinker manufacturing.

PPC is more cost-effective because supplementary materials include fly ash or slag… which reduces the amount of raw material needed.

PSC also uses GGBFS, and depending on a certain percentage, it’s also cost-effective because of the slag reduction from C3A in home constructions in coastal areas as it can resist sulfate & chloride in the seawater.

the next steps will be of who this competition will be.

it will be:

  • sell iron-rich dry AMD sludge to cement plants.
  • sell my own cement with AMD sludge <> cement.

once i choose, there will be a territory field to analyze.

and companies to notice.

but before, i must show you that AMD mineral filtration doesn’t win on the economical turf.


what is fly ash?

high-volume ground granulated blast furnace slag (GGBFS) concrete.

fly ash chemical composition.

GGBFS slag and its activity index.

© 2024–2100 by Carlos Manuel Jarquín Sánchez. All Rights Reserved.