LowEmissionAsphalt-136pg-WhitePaper-May2023

P a g e | 50 PLCs can decrease the embodied CO 2 for the cement by up to 10%. 104 PLCs can be used as a one-to-one replacement for conventional Portland cement and have been used in concrete paving for over 10 years. Reduced Clinker Another option for reducing concrete CO 2 is to reduce the absolute amount of “clinker” used in production. Clinker is the backbone in cement production and is created by heating limestone and the other minerals in powerful kilns at high temperatures. Reducing the absolute amount of clinker needed is achieved by incorporating supplementary cementitious materials (SCMs) into other types of blended cements beyond PLCs to lower the amount of energy and heating, hence carbon required. Types of SCMs: ▪ Fly Ash – a byproduct of thermal power generating stations. ▪ Slag Cement – which is a byproduct from blast furnaces. ▪ Silica Fume – is a fine micro-silica residue byproduct of silicon production. It is a key ingredient in high-strength concrete (HSC). Most PCC mixes have a clinker-to-cement ratio of 90%. 105 The remaining material, gypsum, limestone, and processing additions can be partially replaced with SCMs. SCMs can proportionally reduce the CO 2 that comes with clinker production. So, replacing the clinker loading by 5% reduces the amount of CO 2 by 5%. 106 Performance Engineered Mixtures (PEM) PEM originally was developed to design concrete mixtures to achieve better durability or to enable the material itself to last for as long as the pavement is designed. A PEM Transportation Pooled Fund was established by FHWA, numerous SDOTs, and the leading PCC industry consortia to develop and bring newer PCC mix technologies to broader use. The primary benefits associated with the use and implementation of PEMs: • Improved testing for durability properties. 104 Portland Cement Association (PCA) . 105 PCA . 106 PCA .