Page 46 - Demo

CONCRETE TECHNOLOGY44 CPI %u2013 Concrete Plant International %u2013 4 | 2025 www.cpi-worldwide.comThis article primarily focuses on Optimization Approach II and Optimization Approach III, along with the resulting compressive strength developments. Durability investigations, particularly studies on carbonation resistance, have been conducted but are not part of this article. Additionally, detailed calculations of the resulting CO2 emissions are not covered here. However, the CO2-reducing effect of the optimization approaches can be directly inferred from the GWP (Global Warming Potential) data of the individual constituent materials (see Table 1) and the mix compositions provided below.Granulometric optimization of ternary bindersIn a first step, the influence of granulometric optimization of ternary binders on compressive strength development was studied using mortar mixes with a constant w/b ratio of 0.45. Table 3 summarizes the mortar compositions investigated. The slag content in the binder was kept constant at 30 wt.-%. The remaining components, i.e., clinker and limestone powder, were varied accordingly %u2013 as the clinker content decreased, the limestone powder content increased proportionally. The physical properties of the constituent materials used are summarized in Table 2. The clinker fraction consisted of ordinary Portland cement CEM I 52.5 R according to DIN EN 197-1 [17] (clinker content %u2265 95 wt.-%). Sulphate carriers andother minor constituents (up to 5 wt.-%) were neglected in the mix design calculations and accounted for as part of the clinker content. The fineness of the slag was systematically varied at three levels. The coarsest variant was a standard slag (d50 = 12.1 %u03bcm). The finer variants were Mikrodur R-F(d50 = 5.2 %u03bcm) and Mikrodur R-X (d50 = 2.6 %u03bcm) supplied byDyckerhoff GmbH, Germany [18]. Mikrodur products are fine binders based on granulated blast furnace slag. Their composition corresponds to that of a CEM III/C according to DIN EN 197-1 [17]. During production, the constituent materials are ground separately, sieved to the desired fineness, and classified by particle size. The small proportion of clinker and minor constituents in these products was considered during mix design and assigned to the clinker content of the mortars.Figure 3 shows the compressive strength after 24 hours (left) and 28 days (right) depending on the clinker content, ranging from 50 wt.-% to 20 wt.-%, taking into account the fineness of Fig. 2: Concrete technology optimization approaches considered for the production of resource-efficient and CO2-reduced tunnel segments.Table 1: Global Warming Potential (GWP) data for the individual constituent materials.Constituent Supplier GWP (gross)(kg%u00b7CO2/kg)CEM I 52,5 R Dyckerhoff GmbH 0.888CEM III/A 52,5 N (Variodur 40) 0.650CEM III/B 42,5 N-LH/SR/NA (Aquadur Doppel) 0.359Mikrodur R-X 0.323Next Base SR03 CE 0.717Limestone powder SH minerals 0.039Master X-Seed 100 Master Builders Solutions Deutschland GmbH 0.675Superplasticizer PCE (< 30% Fst.) 0.689I) Calcium sulfoaluminate cement + retarding admixtures%u2022 Use of calcium sulfoaluminate cement (CSA) in combination with Portland cement (CEM III)%u2022 Development and testing of retarding admixtures in CSA+ CEM III binder systems %u2022 Variation of the binder composition %u2013 clinker/slag/limestone powder%u2022 Granulometric optimization of the slag component (fineness)%u2022 Effect of accelerating admixtures in clinker-reduced concrete%u2022 Development of an accelerating admixture for clinker-reduced concreteII) Granulometric optimization of ternary bindersIII) Accelerated admixture for clinker-reduced binders