Sustainability and reduction of environmental impacts have continued to increase in importance in the concrete marketplace. Portland-limestone cement (PLC) has been shown to reduce total energy consumed and CO2 produced during the cement manufacturing process. This material may also have the ability to benefit concrete properties, such as compressive strength and time of set. Other concrete performance measures of potential interest evaluated in this study include durability and modulus of elasticity. In this dissertation PLC was evaluated for its ability to further increase concrete sustainability, while at the same time providing advantageous properties. This study’s focus was to show that PLC can improve concrete mixtures that are similar to commonly used ordinary portland cement (OPC) mixtures. PLC was also evaluated for its ability to increase the amount of total cement replacement (further increasing sustainability). Additionally PLC properties and concrete mixture combinations were evaluated in an attempt to clarify which PLC properties are crucial in performance benefits. Approximately 2000 concrete specimens were tested along with approximately 1000 cement paste specimens. This dissertation also includes an evaluation of PLC being used in a large scale construction and renovation project on a college football stadium. The scope of the dissertation included 12 cements from four manufacturing facilities that represent a large portion of the cement industry in the southeast US. Supplementary cementitious materials (SCMs), Class C fly ash, Class F fly ash, and slag cement, were also evaluated in single and dual SCM concrete mixtures at replacement rates up to 70%. Replacement rates of this magnitude are not being used in common practice but may become preferred in some conditions with PLC. Results indicated that PLC outperformed OPC in areas tested, in almost all cases at up to 50% replacement with single and dual SCMs. PLC also showed considerable advantages at 60% replacement but was often outperformed by OPC at 70% replacement. Aggregate type played a large role at 70% replacement. Elastic modulus, durability, and variability were all similar with PLC and OPC. Combinations of certain SCMs were more advantageous than others, and optimal SCM combinations changed depending on cement source.

With the pressure on the construction industry to lower CO2 emissions it has become increasingly important to utilise materials that supplement Portland cement (CEM I) in concrete. These include additions such as ground granulated blast-furnace slag (GGBS) and fly ash, which have found greater use due to the benefits they provide to many properties of the material (in addition to environmental impact). While studies have investigated these materials in binary blends with CEM I, little work has examined the effect of combining materials in ternary blend concretes. A wide-ranging study was, therefore, set up to examine this for the range of more commonly available additions. This thesis reports on research carried out to investigate the effects of cement combinations based on CEM I / GGBS with either fly ash or limestone. The experimental programme investigated these materials in both paste and concrete and covered fresh properties, compressive strength, permeation and durability properties (using standard water curing for the latter three) and considered, for the hardened properties, how these may be balanced with environmental cost. The mixes covered a range of w/c ratios (0.35. 0.50 and 0.65), which was the main basis of comparison, and combinations of CEM I with GGBS (at levels of 35%, 55% and 75%), and fly ash and LS part-replacing this (at levels of 10 to 20 % and 10 to 35% respectively), after consideration of the relevant standards and related research. The initial phase of the study examined the characteristics of the materials, which indicated that they conformed to appropriate standards and were typical of those used in the application. Studies with cement paste (0.35 and 0.50 w/c ratio) indicated that there were reductions in water demand with the use of addition materials (binary and ternary) compared to CEM I. The setting times of the cement pastes were also affected, generally increasing with GGBS level for the binary mixes, although the effect was influenced by w/c ratio. Whilst fly ash and limestone delayed setting at the higher w/c ratio, the opposite occurred as this reduced, compared to the binary mixes. It was also found that the yield stress increased with GGBS level and further with the addition of ternary materials (particularly limestone) compared to CEM I. The superplastiser (SP) dosage requirement in concrete was found to decrease with increasing w/c ratio, and ternary additions reduced this compared to binary and CEM I concrete with the effect most noticeable at low w/c ratio. Early strength development was less than CEM I for binary concretes and differences increased with GGBS level. Improvements with the introduction of fly ash compared to the binary concretes were noted with increasing GGBS levels and w/c ratio. In general, the addition of LS gave reduced early strength for all concretes. Although at the 35% GGBS level binary concretes achieved similar strength to those of CEM I, the others generally gave reductions at all ages to 180 days, with differences increasing with GGBS level. However, with increasing w/c ratio and GGBS level improved strength development of ternary concretes, was noted compared to those of CEM I from 28 days. Permeation (absorption (initial surface absorption and sorptivity) and permeability (water penetration and air permeability)) and durability properties (accelerated carbonation and chloride ingress) of the test concrete were also investigated. At 28 days, for low GGBS levels, the binary concretes gave reduced absorption properties compared to CEM I, while the reverse occurred at high level. The effect of the ternary concretes gave further improvements at the lower GGBS levels and with increasing w/c ratio and curing time compared to CEM I. At the higher GGBS level the effect of the ternary additions was less noticeable but, in the case of limestone, improvements were still seen with increasing w/c ratio compared to CEM I. Similar effects were noted for the sorptivity results. The air permeability results gave higher values at 28 days for the binary and ternary concretes compared to CEM I, but significant improvements in the long-term at the lower GGBS level across the range of w/c ratios compared to CEM I concrete. Similar trends were found with water penetration tests. Accelerated carbonation increased with GGBS level for binary concretes compared to CEM I. These differences increased further with the introduction of fly ash and LS, particularly the former. In contrast rapid chloride tests indicated improvements with increasing GGBS levels compared to CEM I and further benefits with the inclusion of fly ash and limestone. Embodied CO2 (ECO2) was calculated based on published British Cement Association (BCA) values for each component of the mix and was shown to reduce with increasing w/c ratio and addition level in concrete. For concrete of an equal strength of 40N/mm2 the ECO2 could be almost halved (reduced from 343 kg/m3 for the CEM I to 176 kg/m3) for the ternary concretes at higher GGBS levels. These combination concretes also gave enhanced durability with regard to chloride ingress and at the lower w/c ratio comparable properties to CEM I in the case of carbonation. Overall, the results suggest that there is potential for ternary concretes to be used in the concrete industry given their ability to reduce ECO2, without compromising strength, permeation and durability properties of concrete.

In this study, the freeze-thaw performance and other engineering properties of different cementitious mixtures containing Type I/II portland cement, Type IL (10) portland Limestone cement (PLC) and Coarse Ground cement (CG-P) with or without partial replacement of fly ash (Class F) were examined. The goal was to develop a concrete mixture with better or similar freeze-thaw durability without adversely affecting other engineering properties of concrete. Crucial engineering properties reviewed include compressive strength, splitting tensile strength, workability, the degree of hydration, setting time, shrinkage and resistivity. The study was divided into two parts, one consisting of mechanical testing of engineering properties including the freeze-thaw test. The second part consisted of microstructure study which involved detection and quantification of micro-cracks/defects using μ-CT and fluorescence microscopy. The results showed that the portland limestone cement in combination with fly ash demonstrated better or similar durability in comparison to the conventional portland cement concrete mixtures.