Mix proportions

The mix proportions for concrete paving mixtures are determined by attaining optimum characteristics of the mix in both the plastic and hardened states. The designed mixture can be properly placed and consolidated, finished to the required texture and smoothness, and will have the desired properties necessary for pavement performance. Concrete paving mixtures should be... 

Mixing Proportions of Flowable Fill with Spend Foundry Sand (kg/m3)... 

The principal reaction hazard attached to use of acetic anhydride is the possibility of rapid and exothermic acid-catalysed hydrolysis unless the conditions prevailing (temperature, agitation, order of mixing, proportion of water) are such as to promote smooth and progressive hydrolysis with adequate heat removal. The examples below illustrate these factors. 

Let us now build the stripping matrix (AJA) lAT, which is independent of the mixing proportions... 

Mendal et al. (1993) compared eight tests of normality to detect a mixture consisting of two normally distributed components with different means but equal variances. Fisher s skewness statistic was preferable when one component comprised less than 15% of the total distribution. When the two components comprised more nearly equal proportions (35-65%) of the total distribution, the Engelman and Hartigan test (1969) was preferable. For other mixing proportions, the maximum likelihood ratio test was best. Thus, the maximum likelihood ratio test appears to perform very well, with only small loss from optimality, even when it is not the best procedure. 

If the admixture is added directly to a concrete as part of the gauging water with no other changes to the mix proportions, a concrete possessing similar strength development characteristics is obtained, yet having a greater workability than the control concrete. 

It is possible to vary the addition level of water-reducing admixtures when an increase in dosage level will generally produce an increase in the amount of water which it is possible to remove from the mix proportions whilst maintaining the required slump. Typical values are shown in Table 1.13 for an aggregate-cement ratio of 5.85 1 and a slump of 50 mm. 

Shacklock, B.W. (1975). Concrete Constituents and Mix Proportions, Cement and Concrete Association. 

Mix proportions cement sand crushed limestone = 1 4.0 6.5, water-cement = 0.45 1. 

The commonly used ratios of admixture to cement for the purpose of shrinkage compensation are 9-11 (admixture) to 91-89 (cement). At these ratios the properties of CSA concrete are similar to Portland cement concretes of similar mix proportions. At admixture dosages exceeding 11% however, concrete workability and strength decrease, while expansion and air entrainment increase. When expansion is umestrained and exceeds 0.3%, strength is reduced [74]. 

Mix proportion aspects that should be considered in the design of highly flowable mixtures include (1) cement content (2) fines content (3) type of superplasticizer (4) the presence of other admixtures in the mix (5) type of cement or cementitious material (6) dosage of the admixture (7) sequence... 

The lower water-cement ratio afforded by the use of a superplasticizer may be used to increase existing compressive strengths or to reduce cement content. Thus the use of superplasticizers may enable the precast producer to use lower cement content without reduction in mix workability and rate of strength development. The actual amount of cement reduction achieved will depend on the cement type used and the mix proportion used in the concrete. Previous work [63] indicates that even with low cement content (306 kg m 3) a normal dose of superplasticizer can accelerate 3- and 28-day strengths by 90% and 55%, respectively, over levels attained with a plain mix. Cement reductions in the range of 11-20% have been achieved in mixes with a cement content of 415 kg m, while maintaining desired strength... 

Since each field installation will use locally available materials, mix proportions may have to be adjusted for the character of the aggregate, cement and specific brand of the admixtures. A sufficient number of lab trial... 

Damp-proofing admixtures include soaps and fatty acids which react with the cement hydrates to modify workability, bleeding and settlement, air content, compressive strength and durability characteristics. Mix proportions, mix consistency, admixture dosage and poor mixing influence the effects produced by the admixture. In cement-rich mixes void content is often increased, resulting in increased permeability. Since the admixture... 

Some very interesting problems occur when an estate is divided up between all the heirs. And then there s the executor s share to be considered in the mix. Proportions are very handy when you re determining who gets how much money. 

In an earlier state of the art report (1) various properties of sulphur concretes were outlined. In the last few years, researchers have concentrated on the topics of durability (moist environment, biological and chemical attack, cycles of freezing and thawing), stress-strain behaviour and mix proportioning. 

---