An Experimental Research on Partial Replacement of River Sand by Silica Sand and Partial Replacement of Cement by GGBS in Rigid Pavements

The utilization of substitutes aggregats like silica sand is a characteristic advance in solving some common aggregate. The examination on substitute material for concret making began before 50 years. concret produced using silica sand as partial additional of River sand will be studies for workability, compressive strength, Flexural strength and split strength, and modulus of elasticity. I will used of silica sand as partial additional of River sand by various rate for making concert of grade M-40. The rate of additional substitution will be 0%, 25%, 50% and 75% with common River sand. For making concrete OPC-53 grade cement is utilized. cube shapes, cylinder and beams will cast and testing compressive strength, Split strength, and flexural strength just as for durability properties. Ideal additional of silica sand can be utilized in structural concerts. GGBS is a Ground Granulate Blast Furnace slag, which is in powdered forms, In concert, it help to decrease the damage caused by an alkali silica chemical attack and also gives higher attrition to chloride. Therefore 35% of GGBS is replacement to cements.

Application of Ground Granulate Blast Furnace Slag-Steel Slag Composite Binder in a Massive Concrete Structure under Severe Sulphate Attack

A composite mineral binder was prepared by mixing ground granulate blast furnace slag (GGBS) and steel slag (GGBS/steel slag ratios are 1 : 1 or 3 : 2 by mass). The application of a composite binder in a massive concrete structure under severe sulphate attack is discussed by determining the hydration heat, adiabatic temperature increase, compressive strength, elastic modulus, chloride ion permeability, and sulphate attack resistance. The results show that the hydration heat of the composite binder decreases greatly when the cement replacement ratio increases to 50% at 45°C. The adiabatic temperature rise of the concrete containing the composite mineral admixture decreases significantly. Concrete containing the composite mineral admixture has a lower early elastic modulus and satisfactory late-age compressive strength. The composite mineral admixture can improve the resistance to chloride ion permeability and sulphate attack resistance of concrete, especially during temperature match curing.

Late-Age Properties of Concrete with Different Binders Cured under 45°C at Early Ages

It is commonly accepted that high curing temperature (near 60°C or above) results in reduced mechanical properties and durability of concrete compared to normal curing temperature. The internal temperature of concrete structures at early ages is not so high as 60°C in many circumstances. In this paper, concretes were cured at 45°C at early ages and their late-age properties were studied. The concrete cured at 20°C was employed as the reference sample. Four different concretes were used: plain cement concrete, concrete containing fly ash, concrete containing ground granulate blast furnace slag (GGBS), and concrete containing silica fume. The results show that, for each concrete, high-temperature curing after precuring does not have any adverse effect on the nonevaporable water content, compressive strength, permeability to chloride ions, and the connected porosity of concrete at late ages compared with standard curing. Additionally, high-temperature curing improves the late-age properties of concrete containing fly ash and GGBS.

Influence of Additve on Over-Sulfur Phosphogypsum-Ground Granulate Blast-Furnace Slag Cement

The effect of sodium hydroxide (NaOH) and polycarboxylate superplasticizer amount on over-sulfur phosphogypsum–ground granulate blast-furnace slag cement was investigated. The mechanical performances and hydration mechanism of the cement with different proportions of NaOH and polycarboxylate superplasticizer (BASF) were analyzed based on setting time, the additive quantity of water, strength test, XRD and SEM analyses. The results showed that the polycarboxylate superplasticizer, can increase the densification and the strength of the cement ,to improve the performance of the cement anti-carbonation properties. NaOH as an alkali activator significantly reduces the cement setting time and improves the cement early strength. But the acceleration of hydration process produces coarse crystalline hydration products and the osteoporosis structure of hardened paste, which has a negative effect on long term strength.

Effect of Phosphogypsum on the Properties of Over-Sulfur Phosphogypsum–Ground Granulate Blast-Furnace Slag Cement

Over-sulfur phosphogypsum(PG)–ground granulate blast-furnace slag(GGBFS) cement paste is utilized by GGBFS, Portland cement clinker(PCC), additive, water and modificated phosphogypsum paste(MPG), produced by milling PG mixed with a certain proportion of steel slag(SS), GGBFS and water. The effect of PG on the properties of over-sulfur PG– GGBFS cement was investigated. The mechanical performances and hydration mechanism of the cement with different kinds, proportions and particle size of PG were analyzed based on setting time, volume stability, strength test, XRD and SEM analyses. The experimental results show that,the optimum mixture of PG amount in the binder was 45%. Overdose of PG may caused strength deterioration. The optimum grinding time of MPG in the binder was 20min. The soluble phosphorus content of PG in the binder was under 0.05%.