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Portland cement paste was prepared in the following five ways: (1) cured in fresh water, (2) made with fresh water, cured in sea water, (3) made and cured in sea water, (4) low-pressure steam cured, (5) high-pressure steam cured. The water-cement ratio was 0.4 in all cases. Slow crack growth was studied by the double torsion method, and plots were made of crack velocity versus stress intensity. Fracture toughness and the modulus of elasticity were also measured by flexural beam methods. The steam cured specimens had lower fracture toughness and were somewhat more sensitive to static fatigue than the room-temperature cured specimens. There was evidence that crack growth is aided by the presence of water in the environment or by increased water-cement ratio.

Historically, concrete and mortar have been used as a flooring and wearing surface because of their availability, durability, and relatively low cost. Under extreme exposure conditions, however, conventional Portland cement mortar and concrete are not sufficient. For example, chemicals, abrasion, and freeze-thaw cycling require that some method of protection be given to the concrete or that another material be used. The most versatile and economical method of protection is a topping of Portland cement mortar modified with saran polymer. The unique chemistry of the saran polymer is such that the mortar bonds tenaciously to the concrete substrate, while maintaining superior chemical and abrasion resistance to most environments encountered in chemical and processing plants. Chemical exposure tests, as well as 10 yr of history, have demonstrated the performance of this modified mortar.

This paper describes a method of removal of the silicate phases in cements and clinkers by leaching with a maleic acid-methanol solution. Quantitative and qualitative determinations by x-ray diffraction can be made on the minor compounds remaining after separation. These compounds include the ferrite phases (C6A2F, C4AF, C6AF2 and C2F), C3A, NC8A3, C4A3 S , and MgO periclase. The paper discusses techniques used, pure compounds manufactured and calibration curves contructed.

It was determined in this research that a Portland cement concrete surface could be treated with methyl-methacrylate in monomer form and then polymerized in situ by natural sunlight. The penetration of the methyl-methacrylate was 0.4 in. nominally with about 50% of the initial loading being polymerized in the concrete surface. The following conclusions were made: (1) it is feasible to use methyl-methacrylate as a surface treatment for Portland cement concrete; (2) such treatment will not significantly increase the strength characteristics of the concrete; (3) such treatment will significantly reduce the amount of water absorbed through the surface of the concrete; (4) such treatment will improve the durability of the surface; and (5) such treatment will reduce the skid-resistance of the surface.

Glass fibre reinforced cement (GRC) provides an interesting example of interaction between a brittle fibre and a porous brittle matrix which is reactive towards the reinforcement. It is also a case in which the composite fails by multiple fracture. The durability of GRC produced from ordinary Portland cement and an alkali-resistant glass fibre recently developed in the U.K., has been studied over a period of three years under different environmental conditions by measuring the variations in the mechanical properties of these composites with age. The experimental results are interpreted in terms of the micromechanics of failure for these composites and an assessment is made of the role of the interface in controlling the behaviour of the composite at various stages of its life. It is concluded that the properties of the interface in GRC change with time, partly due to chemical attack on the fibre which weakens the reinforcement but also due to changes in the physical properties of the fibre bundle and porosity and volume changes in the matrix as it sets and hardens. It has, however, not yet been possible to characterise the materials nature of the interface in GRC composites.

The suitability of clinker-activated high-slag cement mortars for use in brickwork construction and in rendered finishes, has been investigated. The study was carried out on a slag cement composed of 80% granulated slag, 15% clinker and 5% raw gypsum; its specific surface area was 4000 cm2/g. It was found that the slag cement mortars and cement-lime mortars of the proportions commonly used in practice, have higher water-retentivity than the corresponding mortars of ordinary Portland cement, and that their strengths are comparable to those of the latter mortars.

An extensive scanning electron microscopy study was carried out with respect to the fracture surfaces of Portland cement hydrated for various times. It is shown that the two major products of hydration are calcium silicate hydrate spherulites, which consist of radiating fibres and calcium hydroxide platelets. These fibres bond with one another to hold the spherulites together. The volume between the spherulites consists of calcium hydroxide platelets. The fracture is frequently found to be across the weakly bonded basal planes of the calcium hydroxide, and is believed to limit the strength of the Portland cement.

Small-angle X-ray scattering was used to determine the specific surfaces of hardened portland cement pastes subjected to various treatments. Reasonably mature pastes yielded values of the order of 700 m2/g of ignited paste when examined in the original saturated condition.Driving to an intermediate relative humidity, P-drying, and D-drying reduce the surface areas to values of the order of 200 to 300 m2/g, but vacuum resaturation results in recovery of all the lost surface. Oven drying produces an additional loss in surface area, and in this case recovery on resaturation is not quite complete. The effect of w/c ratio appears to be minor, and pastes of hydrated C3S yield essentially the same surface areas as corresponding portland cement pastes. /AUTHOR/

This study deals mainly with the morphology of the so-called prismatic phase in Portland cement clinker and some characteristic microstructures of the interstitial material. Crystals of the prismatic phase as well as those of the solid solution in the system C 3 A-NC 8 A 3 are usually composed of the forms: bipyramids {112}, {111}, pinacoids {100}, {010}, {001}, being square tablets on {001}. A description has been given on parallel growths between the constituent minerals of the interstitial material. Zonal structure within crystals of the prismatic phase has been confirmed experimentally.

This paper presents data on the influence of a lignosulphonate admixture, used either with or without the accelerating admixtures calcium chloride and triethanolamine, on drying shrinkage and creep in concrete. The ability of these admixtures to give rise to significant increases in drying shrinkage and creep is discussed in terms of the Feldman and SeredaNew Model for the structure of hydrated Portland cement. It is postulated that the increases in drying shrinkage and creep can be attributed to the influence of the admixtures in altering the initial spacing and degree of layering of the tobermorite gel, which takes place on first dryring.

The influence of precuring at room temperature on the autoclave hydration of C 3 S in the presence of other constituents of clinker and of gypsum was studied. C 3 A, C 4 AF and β-C 2 S hampered the formation of C 3 SH 1.5 and, especially for short precuring times, favored the formation of α-C 2 SH. Gypsum hampered the formation of both the crystalline hydrated silicates. When the steam treatment took place after a long precuring, C-S-H was the prevailing hydrated silicate formed.

The study of hydration of expansive cement prepared from 64% portland cement clinker, 23% metakaolinite and 13% CaSO 4 .2H 2 O is described. It was found that in the course of a 10-day hydration period, all the gypsum entered the reaction with the formation of ettringite. In 7–10 days, after the termination of the expansion processes, typical stalk-like crystals were transformed into leaf-shaped or other formations. Ettringite was identified even after 4 months of hydration. Monosulphate (3CaO.Al 2 O 3 .CaSO 4 .12H 2 O) was found in none of the investigated high-expansion cement paste samples.

The impregnation of hardened, dry specimens of Portland cement concrete with melted elemental sulphur increases the compressive strength by a factor of 2.7. The compressive strength of sulphur-impregnated concrete (SIC) with 8.4 per cent sulphur by weight is 174 MN/m2 (25,300 psi). Due to the large surplus of sulphur and the low price, SIC might be a useful alternative to polymer-impregnated concrete, PIC.

As a measure of supersaturation with respect to Ca(OH)2 in the solution of portland cement paste, W/C=0.6, a saturation ratio was used, which was defined by the ratio of actually determined product m′Ca2+⋅m′2OH- to the solubility product, both in molalities, at the same ionic strength. For three of five cements examined, there was seen the time correspondance between the occurrence of maximum saturation ratio of about 3 and the beginning of intensive rise of heat liberation rate. This was ture for the cement paste with or without addition of soluble salt after pre-leaching treatment of cement with a large amount of water. For the other two cements, the maximum saturation ratio was established in an hour, while the rise of heat liberation rate was two to three hours late.

The paper, which summarises a survey and an analysis of empirical strength laws, was undertaken with a view to formulating a strength law interrelating the water-cement ratio-which determines the porosity of the hardened cement-paste-and Powers's Gel/Space ratio, giving the relative strength of the cement stone.

Specific surface areas and pore structure studies were carried out on “neat” portland cement pastes as well as on cement pastes reinforced with 0.5% or 3% by weight of either asbestos or glass fibres. Investigations were carried out using two W/C ratios, namely 0.2 and 0.7. Fibre reinforcement has a more significant effect on the meso-pore fraction of the structure than on the micro-pore fraction. For meso-pores it affects both their most probable hydraulic radius, as well as their number, whereas for micropores the effect is mainly reduction in number. The effect of fibre reinforcement is qualitatively similar to the effect due to reduction in the water/cement ratio. The reflection on the engineering properties will be a subject of a forthcoming publication.

The influences of chlorides on cement and concrete is discussed. It is stressed that chlorides enhance sulphate attack. Severe conditions which accelerate corrosion in hot arid areas are described. Laboratory experiments on the behaviour of clinker and normal Portland cement immersed in corrosive solutions for a period of 8 years are described. A scheme for chloride attack processes is described. Two of the general conclusions are: 1. (1) The penetration and adsorption of chlorides into Portland cement is much higher than that of sulphates. 2. (2) Climatic factors have a decisive influence on the character and magnitude of corrosion.

Comparative measurements are reported of the moisture content, during air drying, of concrete slabs as measured by 1. (a) a commercial electrical resistance “moisture meter” complying with the requirements of Australian Standard CA 37-1966 2. (b) progressive weight loss to the atmosphere followed by oven drying. Wide divergence between the results from (a) and (b) were observed for all four concretes tested. Lesser, but significant, differences were observed in the resistance-moisture relationships of otherwise identical concretes made with different brands of portland cement. Resistance results from fixed depth electrodes showed a significant thickness effect; this disappeared if the electrode depths were made a fixed proportion of slab thickness. This is explained on the basis of diffusion theory. No correlation could be found between cement composition and the resistance-moisture relationships of the concrete. This suggests that the physical structure of the cement paste may play a significant part in determining this relationship. It thus appears that the use of electrical resistance meters to determine the moisture content of concrete may produce very misleading results unless the meter is calibrated with concrete having the same characteristics as that to be tested.

Helium flow techniques are applied to the hydrated portland cement-water system during rewetting. Measurements of solid volume and density demonstrate irreversible changes to the structure. Measurement of changes in volume of interlayer space are made and are shown to be due to new alignment of layers and to the moving apart of layers as a result of water penetration. The density of the interlayer water is found by these techniques to be 1.20 ± 0.08 gm/ml. Calculation of the parameter Total Volume/Monolayer Volume for the interlayer space yields a value of 1.32. This shows that the space approximates that bounded between two parallel plates.

Instrumental neutron activation analysis using a Ge(Li) detector has been used for the determination of chlorine bound in the hydration of portland cement. Results obtained are in agreement with data published by other investigators.

Thermal expansion of hardened cement paste has been determined within the temperature range of −30°C and +80°C. Mositure content varied from virtually zero to saturaton. Immediate thermal response is followed by time dependnt ration. Immediate thermal response is followed by time dependent partial recovery. A tentative explanation for this behaviour is given.

The fracture of a fiber-reinforced cement, investigated by scanning electron microscopy, shows different types of areas with emergence and imbrication of fibers. Particular well-monocrystallized ettringite (“flower-like” crystallization), generally not encountered in hydrated pure portland cement paste, can be observed in some voids or cavities. This phenomenon is due to the macroporous texture of the material.

A light-pipe technique has been used to follow interfacial changes during the setting and hardening of Portland cement composites. Easily detectable changes have been recorded and are attributed to dilatancy, gel formation and to stress enhanced corrosion.

The results of freezing experiments performed on samples of hardened portland cement-flyash pastes, saturated with benzene and water respectively, are presented. The specimens contained portland cement and flyash in the ratio of 55:45 by weight, and had a water-solids ratio of 0.50. A length change anomaly which occurred in the region of the bulk freezing point of benzene is explained by the hydraulic pressure theory. In discussing their own test results, as well as those of others, the authors deal at some length with thermodynamic considerations of moisture movement as it relates to possible mechanisms of frost action.