Engineering and construction have significantly improved in the new millennium that the researcher has proved several cement concrete replacements adequately met construction standards. These researchers are driven by the purpose of using less raw materials (cost control) and make something out of waste materials and convert them into a matter of use without harming the environment (eco-friendly).
Cement replacements nowadays are greatly used for a better purpose and quality of concrete output. It helps a lot to the durability of concrete and promotes strength. So, here are the most common cement replacements globally accepted to be legitimate and you could use on your construction site.
Pulverized Fuel Ash (PFA or Fly Ash)
Fly ash is a by-product of burning pulverized coal in electric power generating plants. During combustion, mineral impurities in the coal (clay, feldspar, quartz, and shale) fuse in suspension and float out of the combustion chamber with the exhaust gases. Some use fine moisture sprinklers to recover the apparent 75% flue gas that is being suspended on air. These ashes are then collected into containment to be used as a cement substitute. Several studies have proved the efficiency of fly ash as a concrete replacement. But, some are suggesting the proving that fly ash cannot be used as a complete cement substitute due to its dependency on the cement’ lime to as part of the cement’ chemical reaction.
Soon enough, with several movements internationally by the environmentalists, fly ash may be inadequate or minimal due to lesser and lesser coal-based power plants.
Ground Granulated Blast-Furnace Slag (GGBS)
Again, a waste product of plant industry, Ground granulated blast-furnace slag (GGBS) slags are the by-product of steel and iron manufacturers.
These slags are produced by placing the molten or liquefied iron or steel slag from a blazing furnace into the water to produce a granular material that is then ground to create a pulverized powder. Chemically it is similar to but less reactive than, Portland cement (Pc).
As these slags are waste from this chemical reaction forming calcium, aluminium and magnesium particles (a common component of cement), these ground granulated blast-furnace slags are one of the best cement replacements discovered by researchers.
The blast-furnace slags characteristic is said to be similar to Portland cement, even gaining higher ultimate strength compared to Portland cement. Furthermore, very tiny and fine in nature, GGBS produces a smoother surface compared with Portland cement. Meaning, less susceptible to dirt, thus, minimizing the maintenance cost.
Others proved that ground granulated blast-furnace blast to be efficient in the construction of piers and docks as it gives protection to chloride and sulphate attacks. Some research also suggests that GGBS would effectively replace sulphate resisting Portland cement or SRPC due to its considerably lower cost and immense performance.
Rice Husk Ash
Rice husk (or Rice hulls are the hard protecting coverings of grains of rice) is wastes abundantly present in Asian countries and the pursuit to make something out of it (aside from converting it to soil fertilizers) has not ended yet. Other than that, the demand to provide a sustainable housing project has prompted engineers to study rice husk ash as a possible cement replacement.
Several studies were conducted and most suggest that rice husk ash may replace concrete partially. Other researchers also suggest that the optimum usage of rice hush ash is promising in nature as these would greatly decrease the emission of harming gases, thus, lesser carbon footprints.
Researchers suggest that limestone fines accelerate the hydration of cement. Meaning, lesser time is needed for structure to settle compared to pure cement. Limestone fines studies show that it is efficient in replacing concrete especially for the scope that needs a lesser time to be realized such as tiling works. Being calcium-based in nature, limestone fines also helps in the early settlement of the concrete.
Similar to limestone fines, silica fumes also manifested to accelerate the hydration of cement but is observed to be slower than limestone fines. On the other hand, the study shows that its yield strength and consistency factor were over the limestone fine. Due to the pozzolanic characteristic of silica fumes, a study shows that a certain percentage added to cement, silica fume would increase concrete strengths. Silica fumes characteristic is similar to the concrete cement mainly because of the silica which is one active ingredient of concrete cement.
These are some of the materials researches considered to be promising as a concrete replacement. These may not totally replace concrete cement, but these materials proved to be helpful in reducing cost and of top-notched quality especially in terms of strength and impermeability of concrete construction. Truly helpful for the environment decreasing our carbon footprint even just a pinch is basically waste from plants or manufacturers.
Several materials are also considered and studied by various researches and my list could go on. Even replacing reinforcing bars with a bamboo is considered by most engineers studying master and doctorate degrees. The need to reduce carbon footprint as we are nearly doomed should be already realized by the politicians and the people in authority.
The studies that have objectives on replacing raw materials with waste by-products should be backed up and encouraged by the government and universities. These greatly affects us in a subtly good way though we may not feel it and see it right away.