Hydraulic cement is used in concrete and most mortars. The main use of hydraulic cement is to bind sand and gravel (aggregate) together. Concrete is formed when portland cement creates a paste with water that binds with sand and rock to harden. Cement is seldom used on its own, but rather to bind sand and gravel together. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete. A small amount of gypsum is often added during the final grinding process to control the “setting” of the cement.
Benefits of High-Strength, Low-Emission Cement
High-strength, low-emission (HSLE) cement has many benefits including:
• Reduced energy consumption – by up to 30% per tonne of cementitious material
• Reduced global warming potential – by up to 50% per tonne of cementitious material
• Reduced production cost and increased profits
• Improved concrete performance – Increased durability due to reduced carbonation and improved resistance to chloride ingress; Increased strength due to improved particle packing; Reduction in heat development during hydration; Improved workability; Reduced permeability
• Sustainable – Reduces the
High-strength, low-emission (HSLE) cement is a new kind of cement that has been developed for use in concrete. It is not just a conventional blend of portland cement and fly ash. Instead, it’s an entirely new type of hydraulic cement that provides many benefits over conventional portland cement.
Hydraulic cements are different from nonhydraulic cements in that they harden by chemical reactions with water rather than by drying out. They owe their name to the fact that they can be set under water.
Concrete is the most widely used material in the world. Yet the production of its key ingredient, portland cement, has a large environmental impact. It produces carbon dioxide emissions at twice the rate of steel manufacturing and uses up a lot of energy too. The production process also generates toxic waste products such as arsenic and lead compounds, ammonia, cadmium, chromium compounds and mercury, which can be harmful if not properly disposed of.
Although there are many ways to reduce these emissions and negative impacts, one simple way is to replace some or all of the portland cement with fly ash in making HSLE cement concrete mixes. In addition to being more environmentally friendly than conventional concrete, HSLE cements also have other
High-strength, low-emission cement (HSLE) is an innovative new product that combines higher strength with a lower carbon footprint. This exciting new technology has the potential to transform the construction industry, paving the way for faster, safer and more sustainable development.
BENEFITS OF FASTER CONSTRUCTION
Concrete structures are put into place at the end of a multi-stage process that involves several different trades, each working in series. The slower you can make each of these stages, the longer it takes for the whole building to be completed.
With traditional concrete, one of the slowest stages is curing; because concrete cures slowly, it takes days or even weeks for many structures to reach their full strength and stability.[1]
But HSLE enables you to pour and cure concrete much faster than ever before; these high-strength concretes can reach their final strength in as little as 24 hours.[2] This means that more elements of the construction process can happen in parallel – speeding up your build time considerably.
FASTER CONSTRUCTION SAVES TIME AND COSTS
Faster construction also means that you can get your building finished on time and on budget – without sacrificing safety or quality.
The gains from
When the PCA published its first report on high-strength, low-emission (HSLE) cement in 2008, we suggested that one of the key reasons that HSLE had not caught on previously was the fact that there was little or no data on its performance and durability in concrete. To support industry acceptance, we recommended that the cement manufacturing industry develop and publish supporting data on the performance of HSLE concrete.
Over the past decade, concrete producers have embraced HSLE cements. The first generation of this product was marketed as an economical solution for a variety of applications where performance requirements were being met by traditional Type I/II cements. The market quickly recognized that these new materials could also help reduce environmental impacts without impacting strength and performance. As a result, several projects were designed with higher-strength cements to reduce carbon emissions and energy consumption associated with production.
Today’s new generation of HSLE cements offer good strength gain and durability, which allows them to have a significant impact on reducing carbon emissions while improving long-term performance.
The Portland Cement Association has been working with cement manufacturers over the past several years to collect additional data from around the world to demonstrate how these products perform in real-world applications. In addition to collecting more data on
Cement has been used in construction for thousands of years. In fact, it is the second most widely used commodity after water. Today, nearly 90 percent of all cement produced is Portland cement. The low cost and widespread availability of the material has made it a key building block for society since its invention.
But production of this essential material can be expensive and harmful to the environment. The process to produce Portland cement emits CO2, which contributes to climate change and global warming, and releases other pollutants into the air that cause respiratory illnesses and acid rain.
The Portland Cement Association recently introduced a new standard for high-strength, low-emission (HSLE) cement that is designed to reduce CO2 emissions and address urgent sustainability issues in the construction industry.
Benefits of HSLE Cement
Hydraulic cement (HPC) is a high-strength, low-emission concrete that reduces greenhouse gas emissions by up to 25%. The use of HPC means that the current infrastructure needs less frequent repairs and upgrades because it is more durable than other types of cement.
Hydraulic cement is made by burning limestone and then grinding it into a powder, which is then mixed with water and sand. This mixture can be applied to any surface where concrete is needed. HPC is used in the construction of roads, bridges, buildings, dams, and other structures.
In addition to being stronger than non-hydraulic cement, HPC is also more resistant to damage from cracking or spalling due to freezing temperatures. This makes HPC ideal for use in climates where temperatures can dip below freezing during the winter months.
The most common type of HPC used today is Portland Cement (PC). This kind of concrete was first developed by Joseph Aspdin in 1824 and patented in 1828 as “Portland Cement.”
Older Portland cement is comprised of three primary components: clinker, gypsum and limestone. The tiny percentage (2%) of clinker in the mix is the active ingredient that binds everything together. Limestone is a filler that provides bulk to the mix and gypsum regulates set time. These components create an inherent flaw in Portland cement when they come into contact with water, emitting CO2 into the atmosphere.
Hydraulic cements, like Portland cement, release CO2 when they react with water. Hydraulic cements were first created by limestone containing clay that would harden in the presence of water – hence their name “hydraulics.”
The massive amount of energy needed to produce clinker is a major source of carbon emissions in Portland cement. Clinker is made by roasting limestone with clay at extremely high temperatures (1,500 degrees Celsius). This process produces CO2 as a byproduct.