Role of cement content in specifications for concrete durability: cement type influences

Abstract

In this paper, which describes part of a major investigation, the role of cement content in specifications for concrete durability is examined. The main cements considered were (a) Portland cement (PC; CEM I), (b) PC/30% PFA (CEM II/B-V) and (c) PC/50% GGBS (CEM III/A), while other BS EN 197-1 cements were tested selectively. Concretes of fixed w/c ratio (w/(PC + addition) ratio), but with cement contents varying around the minimum values given in standards were evaluated. The workability of concrete with low cement and water contents was controlled with a superplasticiser and the fines content was maintained by the use of ground limestone as a filler. Tests were carried out to examine these effects on the fresh, engineering, permeation and durability properties of concrete. The results show that at fixed w/c ratio, reduction in cement content by up to 22% had no adverse effect on most concrete properties and, if anything, gave some improvement. The various cement types and combinations tested had little effect on the trends observed. Overall, it was concluded that, in addition to minimum strength class and maximum w/c ratio (and in some cases cover depth), specifying minimum cement content for concrete durability was not necessary.

Experience of using the prTS 12390-12 accelerated carbonation test to assess the relative performance of concrete

“…As shown in Figure 3 (data from Dhir et al, 2001) the test does give the expected pattern of results for variations in w/c ratio and cement type. In a previous paper , the effect of aggregate type when considering concretes at equivalent w/c ratio (and differing strengths) was described and Figure 4, using a different data set (Dhir et al, 2001), shows the same trend.…”

“…In a previous paper , the effect of aggregate type when considering concretes at equivalent w/c ratio (and differing strengths) was described and Figure 4, using a different data set (Dhir et al, 2001), shows the same trend. However, when concretes from the data set were examined on an equal compressive strength basis, the effect of having a lower w/c ratio to achieve the required strength is seen in reduced carbonation depths in concretes containing higher absorption aggregates (Figure 4).…”

“…The prTS 12390-12 reference method was used in a major study on the role of cement content (Dhir et al, 2001). The experimental technique was to keep the w/c ratio constant and use either no admixture, a water reducer or superplasticiser to achieve the same w/c ratio and slump at different cement contents.…”

“…65. Table 8 summarises the experience of using the prTS12390-12 reference method test with a range of 'normal' concretes from several projects (Dhir et al, 1999(Dhir et al, , 2001Kandasami, 2008). It should be noted that BS 8500 (BSI, 2006) has recommended limits for maximum w/c ratio, minimum compressive strength and minimum cement content.…”

Effect of Water-to-Binder Ratio, Air Content, and Type of Cementitious Materials on Fresh and Hardened Properties of Binary and Ternary Blended Concrete

“…For example, as w/b decreases, the porosity of the paste decreases, and concrete becomes less permeable thereby resulting in increased strength and enhanced durability (Wassermann et al 2009, Dhir et al 2004. Therefore, ACI 318 (2011) recommends a w/b of no greater than 0.45 for concretes subjected to moderate and severe exposures to freezing and thawing (F-T), and exposed to deicing chemicals.…”